lake catchment area: Topics by Science.gov

Sample records for lake catchment area

Hydrology, nutrient concentrations, and nutrient yields in nearshore areas of four lakes in northern Wisconsin, 1999-2001

USGS Publications Warehouse

Graczyk, David J.; Hunt, Randall J.; Greb, Steven R.; Buchwald, Cheryl A.; Krohelski, James T.

2003-01-01

The effects of shoreline development on water quality and nutrient yields in nearshore areas of four lakes in northern Wisconsin were investigated from October 1999 through September 2001. The study measured surface runoff and ground-water flows from paired developed (sites containing lawn, rooftops, sidewalks, and driveways) and undeveloped (mature and immature woods) catchments adjacent to four lakes in northern Wisconsin. Water samples from surface runoff and ground water were collected and analyzed for nutrients. Coupled with water volumes, loads and subsequent yields of selected constituents were computed for developed and undeveloped catchments. The median runoff from lawn surfaces ranged from 0.0019 to 0.059 inch over the catchment area. Median surface runoff estimates from the wooded catchments were an order of magnitude less than those from the lawn catchments. The increased water volumes from the lawn catchments resulted in greater nutrient loads and subsequent annual nutrient yields from the developed sites. Soil temperature and soil moisture were measured at two sites with mixed lawn and wooded areas. At both of these sites, the area covered with a lawn commonly was warmer than the wooded area. No consistent differences in soil moisture were found. A ground-water model was constructed to simulate the local flow systems at two of the paired catchments. Model simulations showed that much of the ground water delivered to the lake originated from distant areas that did not contribute runoff directly to the lake. Surface runoff and ground-water nutrient concentrations from the lawn and wooded catchments did not have apparent patterns. Some of the median concentrations from lawns were significantly different (at the 0.05 significance level) from those at wooded catchments. Water wells and piezometers were sampled for chemical analyses three times during the study period. Variability in the shallow ground-water chemistry over time in the lawn samples was larger than samples from the wooded areas and upgradient wells. Median nutrient yields in surface runoff from lawns always were greater than those from the wooded catchments. Runoff volumes were the most important factor in determining whether lawns or wooded catchments contribute more nutrients to the lake. The ground-water system had appreciable nutrient concentrations, and are likely an important pathway for nutrient transport to the lake. The nitrate plus nitrite nitrogen and total phosphorus yields to the ground-water system from a lawn catchment were approximately 3 to 4 times greater than those from the wooded catchment. There was no difference in the yields of dissolved inorganic phosphorus to the ground-water system from the lawn and wooded catchments. Study results demonstrate that choosing the appropriate landscape position for locating lawns in sloped areas (specifically, slopes that do not terminate at the lake or areas with intervening flat or buffer zones between lawn and lake) can help reduce the adverse effect of lawns on the shallow ground water and, ultimately, the lake. Additional information would be needed to extrapolate these results to a large drainage area of a lake.
Simulating Lake-Groundwater Interactions During Decadal Climate Cycles: Accounting For Variable Lake Area In The Watershed

NASA Astrophysics Data System (ADS)

Virdi, M. L.; Lee, T. M.

2009-12-01

The volume and extent of a lake within the topo-bathymetry of a watershed can change substantially during wetter and drier climate cycles, altering the interaction of the lake with the groundwater flow system. Lake Starr and other seepage lakes in the permeable sandhills of central Florida are vulnerable to climate changes as they rely exclusively on rainfall and groundwater for inflows in a setting where annual rainfall and recharge vary widely. The groundwater inflow typically arrives from a small catchment area bordering the lake. The sinkhole origin of these lakes combined with groundwater pumping from underlying aquifers further complicate groundwater interactions. Understanding the lake-groundwater interactions and their effects on lake stage over multi-decadal climate cycles is needed to manage groundwater pumping and public expectation about future lake levels. The interdependence between climate, recharge, changing lake area and the groundwater catchment pose unique challenges to simulating lake-groundwater interactions. During the 10-year study period, Lake Starr stage fluctuated more than 13 feet and the lake surface area receded and expanded from 96 acres to 148 acres over drier and wetter years that included hurricanes, two El Nino events and a La Nina event. The recently developed Unsaturated Zone Flow (UZF1) and Lake (LAK7) packages for MODFLOW-2005 were used to simulate the changing lake sizes and the extent of the groundwater catchment contributing flow to the lake. The lake area was discretized to occupy the largest surface area at the highest observed stage and then allowed to change size. Lake cells convert to land cells and receive infiltration as receding lake area exposes the underlying unsaturated zone to rainfall and recharge. The unique model conceptualization also made it possible to capture the dynamic size of the groundwater catchment contributing to lake inflows, as the surface area and volume of the lake changed during the study period. Groundwater flows simulated using daily time steps over a 10-year period were used to describe the relationship between climate, the size of the groundwater catchment, and the relative importance of groundwater inflow to the lake water budget. Modeling approaches used in this study should be applicable to other surface-water bodies such as wetlands and playa lakes. Lake Starr watershed (depressions from sinkholes)
Extraction and representation of nested catchment areas from digital elevation models in lake-dominated topography

NASA Astrophysics Data System (ADS)

Mackay, D. Scott; Band, Lawrence E.

1998-04-01

This paper presents a new method for extracting flow directions, contributing (upslope) areas, and nested catchments from digital elevation models in lake-dominated areas. Existing tools for acquiring descriptive variables of the topography, such as surface flow directions and contributing areas, were developed for moderate to steep topography. These tools are typically difficult to apply in gentle topography owing to limitations in explicitly handling lakes and other flat areas. This paper addresses the problem of accurately representing general topographic features by first identifying distinguishing features, such as lakes, in gentle topography areas and then using these features to guide the search for topographic flow directions and catchment marking. Lakes are explicitly represented in the topology of a watershed for use in water routing. Nonlake flat features help guide the search for topographic flow directions in areas of low signal to noise. This combined feature-based and grid-based search for topographic features yields improved contributing areas and watershed boundaries where there are lakes and other flat areas. Lakes are easily classified from remotely sensed imagery, which makes automated representation of lakes as subsystems within a watershed system tractable with widely available data sets.
Sources and yields of dissolved carbon in northern Wisconsin stream catchments with differing amounts of Peatland

USGS Publications Warehouse

Elder, J.F.; Rybicki, N.B.; Carter, V.; Weintraub, V.

2000-01-01

In five tributary streams (four inflowing and one outflowing) of 1600-ha Trout Lake in northern Wisconsin, USA, we examined factors that can affect the magnitude of stream flow and transport of dissolved organic and inorganic carbon (DOC and DIC) through the streams to the lake. One catchment, the Allequash Creek basin, was investigated in more detail to describe the dynamics of carbon flow and to identify potential carbon sources. Stream flows and carbon loads showed little or no relation to surface-water catchment area. They were more closely related to ground-water watershed area because ground-water discharge, from both local and regional sources, is a major contributor to the hydrologic budgets of these catchments. An important factor in determining carbon influx to the stream is the area of peatland in the catchment. Peatland porewaters contain DOC concentrations up to 40 mg l-1 and are a significant potential carbon source. Ground-water discharge and lateral flow through peat are the suspected mechanisms for transport of that carbon to the streams. Carbon and nitrogen isotopes suggested that the sources of DOC in Allequash Creek above Allequash Lake were wetland vegetation and peat and that the sources below Allequash Lake were filamentous algae and wild rice. Catchments with high proportions of peatland, including the Allequash Creek catchment, tended to have elevated DOC loads in outflowing stream water. Respiration and carbon mineralization in lakes within the system tend to produce low DOC and low DOC/DIC in lake outflows, especially at Trout Lake. In Allequash Lake, however, the shallow peat island and vegetation-filled west end were sources of DOC. Despite the vast carbon reservoir in the peatlands, carbon yields were very low in these catchments. Maximum yields were on the order of 2.5 g m-2 y-1 DOC and 5.5 g m-2 y-1 DIC. The small yields were attributable to low stream flows due to lack of significant overland runoff and very limited stream channel coverage of the total catchment area.
The Stream-Catchment (StreamCat) and Lake-Catchment (LakeCat) Datasets: leveraging existing geospatial frameworks and data to characterize lotic and lentic ecosystems across the conterminous US for ecological and environmental modeling

EPA Science Inventory

Background/Question/MethodsLake and stream conditions respond to both natural and human-related landscape features. Characterizing these features within contributing areas (i.e., delineated watersheds) of streams and lakes could improve our understanding of how biological conditi...
Conifer density within lake catchments predicts fish mercury concentrations in remote subalpine lakes

USGS Publications Warehouse

Eagles-Smith, Collin A.; Herring, Garth; Johnson, Branden L.; Graw, Rick

2016-01-01

Remote high-elevation lakes represent unique environments for evaluating the bioaccumulation of atmospherically deposited mercury through freshwater food webs, as well as for evaluating the relative importance of mercury loading versus landscape influences on mercury bioaccumulation. The increase in mercury deposition to these systems over the past century, coupled with their limited exposure to direct anthropogenic disturbance make them useful indicators for estimating how changes in mercury emissions may propagate to changes in Hg bioaccumulation and ecological risk. We evaluated mercury concentrations in resident fish from 28 high-elevation, sub-alpine lakes in the Pacific Northwest region of the United States. Fish total mercury (THg) concentrations ranged from 4 to 438 ng/g wet weight, with a geometric mean concentration (±standard error) of 43 ± 2 ng/g ww. Fish THg concentrations were negatively correlated with relative condition factor, indicating that faster growing fish that are in better condition have lower THg concentrations. Across the 28 study lakes, mean THg concentrations of resident salmonid fishes varied as much as 18-fold among lakes. We used a hierarchal statistical approach to evaluate the relative importance of physiological, limnological, and catchment drivers of fish Hg concentrations. Our top statistical model explained 87% of the variability in fish THg concentrations among lakes with four key landscape and limnological variables: catchment conifer density (basal area of conifers within a lake's catchment), lake surface area, aqueous dissolved sulfate, and dissolved organic carbon. Conifer density within a lake's catchment was the most important variable explaining fish THg concentrations across lakes, with THg concentrations differing by more than 400 percent across the forest density spectrum. These results illustrate the importance of landscape characteristics in controlling mercury bioaccumulation in fish.
Conifer density within lake catchments predicts fish mercury concentrations in remote subalpine lakes.

PubMed

Eagles-Smith, Collin A; Herring, Garth; Johnson, Branden; Graw, Rick

2016-05-01

Remote high-elevation lakes represent unique environments for evaluating the bioaccumulation of atmospherically deposited mercury through freshwater food webs, as well as for evaluating the relative importance of mercury loading versus landscape influences on mercury bioaccumulation. The increase in mercury deposition to these systems over the past century, coupled with their limited exposure to direct anthropogenic disturbance make them useful indicators for estimating how changes in mercury emissions may propagate to changes in Hg bioaccumulation and ecological risk. We evaluated mercury concentrations in resident fish from 28 high-elevation, sub-alpine lakes in the Pacific Northwest region of the United States. Fish total mercury (THg) concentrations ranged from 4 to 438 ng/g wet weight, with a geometric mean concentration (±standard error) of 43 ± 2 ng/g ww. Fish THg concentrations were negatively correlated with relative condition factor, indicating that faster growing fish that are in better condition have lower THg concentrations. Across the 28 study lakes, mean THg concentrations of resident salmonid fishes varied as much as 18-fold among lakes. We used a hierarchal statistical approach to evaluate the relative importance of physiological, limnological, and catchment drivers of fish Hg concentrations. Our top statistical model explained 87% of the variability in fish THg concentrations among lakes with four key landscape and limnological variables: catchment conifer density (basal area of conifers within a lake's catchment), lake surface area, aqueous dissolved sulfate, and dissolved organic carbon. Conifer density within a lake's catchment was the most important variable explaining fish THg concentrations across lakes, with THg concentrations differing by more than 400 percent across the forest density spectrum. These results illustrate the importance of landscape characteristics in controlling mercury bioaccumulation in fish. Published by Elsevier Ltd.
Impacts of forestry planting on primary production in upland lakes from north-west Ireland.

PubMed

Stevenson, Mark A; McGowan, Suzanne; Anderson, N John; Foy, Robert H; Leavitt, Peter R; McElarney, Yvonne R; Engstrom, Daniel R; Pla-Rabés, Sergi

2016-04-01

Planted forests are increasing in many upland regions worldwide, but knowledge about their potential effects on algal communities of catchment lakes is relatively unknown. Here, the effects of afforestation were investigated using palaeolimnology at six upland lake sites in the north-west of Ireland subject to different extents of forest plantation cover (4-64% of catchment area). (210)Pb-dated sediment cores were analysed for carotenoid pigments from algae, stable isotopes of bulk carbon (δ(13)C) and nitrogen (δ(15)N), and C/N ratios. In lakes with >50% of their catchment area covered by plantations, there were two- to sixfold increases in pigments from cryptophytes (alloxanthin) and significant but lower increases (39-116%) in those from colonial cyanobacteria (canthaxanthin), but no response from biomarkers of total algal abundance (β-carotene). In contrast, lakes in catchments with <20% afforestation exhibited no consistent response to forestry practices, although all lakes exhibited fluctuations in pigments and geochemical variables due to peat cutting and upland grazing prior to forest plantation. Taken together, patterns suggest that increases in cyanobacteria and cryptophyte abundance reflect a combination of mineral and nutrient enrichment associated with forest fertilization and organic matter influx which may have facilitated growth of mixotrophic taxa. This study demonstrates that planted forests can alter the abundance and community structure of algae in upland humic lakes of Ireland and Northern Ireland, despite long histories of prior catchment disturbance. © 2015 John Wiley & Sons Ltd.
Variability of rainfall over Lake Kariba catchment area in the Zambezi river basin, Zimbabwe

NASA Astrophysics Data System (ADS)

Muchuru, Shepherd; Botai, Joel O.; Botai, Christina M.; Landman, Willem A.; Adeola, Abiodun M.

2016-04-01

In this study, average monthly and annual rainfall totals recorded for the period 1970 to 2010 from a network of 13 stations across the Lake Kariba catchment area of the Zambezi river basin were analyzed in order to characterize the spatial-temporal variability of rainfall across the catchment area. In the analysis, the data were subjected to intervention and homogeneity analysis using the Cumulative Summation (CUSUM) technique and step change analysis using rank-sum test. Furthermore, rainfall variability was characterized by trend analysis using the non-parametric Mann-Kendall statistic. Additionally, the rainfall series were decomposed and the spectral characteristics derived using Cross Wavelet Transform (CWT) and Wavelet Coherence (WC) analysis. The advantage of using the wavelet-based parameters is that they vary in time and can therefore be used to quantitatively detect time-scale-dependent correlations and phase shifts between rainfall time series at various localized time-frequency scales. The annual and seasonal rainfall series were homogeneous and demonstrated no apparent significant shifts. According to the inhomogeneity classification, the rainfall series recorded across the Lake Kariba catchment area belonged to category A (useful) and B (doubtful), i.e., there were zero to one and two absolute tests rejecting the null hypothesis (at 5 % significance level), respectively. Lastly, the long-term variability of the rainfall series across the Lake Kariba catchment area exhibited non-significant positive and negative trends with coherent oscillatory modes that are constantly locked in phase in the Morlet wavelet space.
Integrative investigations on sediments in the Belauer See catchment (northern Germany)

NASA Astrophysics Data System (ADS)

Dreibrodt, Stefan

2015-04-01

The Holocene history of lake development, catchment vegetation, soil formation and human impact since the onset of the Neolithic period was reconstructed via the analysis of sediment sequences at Lake Belau (northern Germany). The chronology of the annually laminated lake sediment sequence was established via varve counts, radiocarbon dating and tephra analysis. Sequences of colluvial sediments and buried soils studied in 19 large exposures and supplementing auger cores within the lake catchment area were dated via radiocarbon dating and archaeological dating of embedded artifacts. The long term development of the lake status was found to be strongly influenced by local human activity. This is indicated by coincidence of phases of landscape openness deduced from pollen data with input of detritus and solutes into the lake. A comparison with palaeo-climate reconstructions reveals that calcite precipitation in the lake reflects climate variability at least to a certain degree. Calibrating the sediment record of the sub-recent lake sediments (micro-facies) on limnological and meteorological records discovered the influence of the NAO as well as solar activity on the limnological processes during the last century reflected by distinguished sedimentation patterns. A comparative study of additional laminated surface sediment sequences from northern Germany corroborates the results. A high resolution reconstruction of Neolithic weather conditions in northern Germany based on the varves of Lake Belau and Lake Poggensee was facilitated by the calibration. The quantitative records of sediments originating from soil erosion (colluvial sediments, allochthonous input into the lake) illustrate the dominance of short distance surface processes (slopes) acting in Holocene mid-latitude landscapes. Coincidence of gully incision in the lake catchment area and increased allochthonous input into the lake indicates the former occurrence of hydrological high energy runoff events (e. g. in the 14th century or at ca. 200 cal BC) whose regional significance is testable via comparative investigations in additional lake catchments.
Direct versus indirect climate controls on Holocene diatom assemblages in a sub-tropical deep, alpine lake (Lugu Hu, Yunnan, SW China)

NASA Astrophysics Data System (ADS)

Wang, Qian; Yang, Xiangdong; Anderson, Nicholas John; Dong, Xuhui

2016-07-01

The reconstruction of Holocene environmental changes in lakes on the plateau region of southwest China provides an understanding of how these ecosystems may respond to climate change. Fossil diatom assemblages were investigated from an 11,000-year lake sediment core from a deep, alpine lake (Lugu Hu) in southwest China, an area strongly influenced by the southwest (or the Indian) summer monsoon. Changes in diatom assemblage composition, notably the abundance of the two dominant planktonic species, Cyclotella rhomboideo-elliptica and Cyclostephanos dubius, reflect the effects of climate variability on nutrient dynamics, mediated via thermal stratification (internal nutrient cycling) and catchment-vegetation processes. Statistical analyses of the climate-diatom interactions highlight the strong effect of changing orbitally-induced solar radiation during the Holocene, presumably via its effect on the lake's thermal budget. In a partial redundancy analysis, climate (solar insolation) and proxies reflecting catchment process (pollen percentages, C/N ratio) were the most important drivers of diatom ecological change, showing the strong effects of climate-catchment-vegetation interactions on lake functioning. This diatom record reflects long-term ontogeny of the lake-catchment ecosystem and suggests that climatic changes (both temperature and precipitation) impact lake ecology indirectly through shifts in thermal stratification and catchment nutrient exports.
Analysis of land use changes over the last 200 years in the catchment of Lake Czechowskie (Pomerania, northern Poland)

NASA Astrophysics Data System (ADS)

Tyszkowski, Sebastian; Kaczmarek, Halina

2014-05-01

Changes in land cover in the catchment area are, beside climate change, some of the major factors affecting sedimentation processes in lakes. With increasing human impact, changes in land cover no longer depend primarily on climate. In relation to research on sediments of Lake Czechowskie in Pomeranian Province in North Poland, land use changes over the last 200 years were analysed, with particular reference to deforestation or afforestation. The study area was the lake catchment, which covers nearly 20 km2. The analysis was based on archival and contemporary cartographic and photogrammetric materials, georeferenced and rectified using ArcGIS software. The following materials were used: Schrötter-Engelhart, Karte von Ost-Preussen nebst Preussisch Litthauen und West-Preussen nebst dem Netzdistrict, 1:50 000, section 92, 93, 1796-1802; Map Messtishchblatt, 1:25000, sheet Czarnen, (mapping conducted in 1874), 1932; Map WIG (Military Geographical Institute - Wojskowy Instytut Geograficzny), 1:25000, sheet Osowo, (mapping conducted in 1929-31), 1933; aerial photos 1:13000, 1964, 1969; 1:25000, 1987; 1:26000, 1997; aerial ortophotomap , 1:5000, 2010. Today, over 60% of the catchment of Lake Czechowskie is covered with forests, dominated by planted Scots pine (Pinus sylvestris), while the remaining areas are used for agricultural purposes or are built up. The first cartographic materials indicate that in the late 18th c., forest covered almost 50% of the catchment surface. By the year 1870, there was a significant reduction in the forested area, as its contribution fell to 40%. Deforestation took place mainly between the main villages. In the 1920s the forest cover increased to 44%. Today, almost the entire lake is surrounded by forest and a wetland belt (at least 0.5 km wide). Deforestation in the catchment should not be attributed solely to logging because the area of Tuchola Forests (Bory Tucholskie) was repeatedly affected by natural disasters. In the 19th c. these predominantly included fires, while in the 20th c., mostly pest outbreaks were observed. Human activity in the catchment of Lake Czechowskie, shown in the cartographic materials from the late 18th and early 19th c., is also manifested by the creation of dams on the lake, which might have increased water level in the lake. The early 20th c., imaged on the map from 1933, was a period of intense change, leading to agricultural use of wetlands. They were drained by ditches, also in the Trzechowskie peatland. This study was supported by the Virtual Institute of Integrated Climate and Landscape Evolution (ICLEA) of the Helmholtz Association and the research project no. 2011/01/B/ST10/07367 Polish Ministry of Science and Higher Education
Patterns and multi-scale drivers of phytoplankton species richness in temperate peri-urban lakes.

PubMed

Catherine, Arnaud; Selma, Maloufi; Mouillot, David; Troussellier, Marc; Bernard, Cécile

2016-07-15

Local species richness (SR) is a key characteristic affecting ecosystem functioning. Yet, the mechanisms regulating phytoplankton diversity in freshwater ecosystems are not fully understood, especially in peri-urban environments where anthropogenic pressures strongly impact the quality of aquatic ecosystems. To address this issue, we sampled the phytoplankton communities of 50 lakes in the Paris area (France) characterized by a large gradient of physico-chemical and catchment-scale characteristics. We used large phytoplankton datasets to describe phytoplankton diversity patterns and applied a machine-learning algorithm to test the degree to which species richness patterns are potentially controlled by environmental factors. Selected environmental factors were studied at two scales: the lake-scale (e.g. nutrients concentrations, water temperature, lake depth) and the catchment-scale (e.g. catchment, landscape and climate variables). Then, we used a variance partitioning approach to evaluate the interaction between lake-scale and catchment-scale variables in explaining local species richness. Finally, we analysed the residuals of predictive models to identify potential vectors of improvement of phytoplankton species richness predictive models. Lake-scale and catchment-scale drivers provided similar predictive accuracy of local species richness (R(2)=0.458 and 0.424, respectively). Both models suggested that seasonal temperature variations and nutrient supply strongly modulate local species richness. Integrating lake- and catchment-scale predictors in a single predictive model did not provide increased predictive accuracy; therefore suggesting that the catchment-scale model probably explains observed species richness variations through the impact of catchment-scale variables on in-lake water quality characteristics. Models based on catchment characteristics, which include simple and easy to obtain variables, provide a meaningful way of predicting phytoplankton species richness in temperate lakes. This approach may prove useful and cost-effective for the management and conservation of aquatic ecosystems. Copyright © 2016 Elsevier B.V. All rights reserved.
Application of a Three-Dimensional Water Quality Model as a Decision Support Tool for the Management of Land-Use Changes in the Catchment of an Oligotrophic Lake

NASA Astrophysics Data System (ADS)

Trolle, Dennis; Spigel, Bob; Hamilton, David P.; Norton, Ned; Sutherland, Donna; Plew, David; Allan, Mathew G.

2014-09-01

While expansion of agricultural land area and intensification of agricultural practices through irrigation and fertilizer use can bring many benefits to communities, intensifying land use also causes more contaminants, such as nutrients and pesticides, to enter rivers, lakes, and groundwater. For lakes such as Benmore in the Waitaki catchment, South Island, New Zealand, an area which is currently undergoing agricultural intensification, this could potentially lead to marked degradation of water clarity as well as effects on ecological, recreational, commercial, and tourism values. We undertook a modeling study to demonstrate science-based options for consideration of agricultural intensification in the catchment of Lake Benmore. Based on model simulations of a range of potential future nutrient loadings, it is clear that different areas within Lake Benmore may respond differently to increased nutrient loadings. A western arm (Ahuriri) could be most severely affected by land-use changes and associated increases in nutrient loadings. Lake-wide annual averages of an eutrophication indicator, the trophic level index (TLI) were derived from simulated chlorophyll a, total nitrogen, and total phosphorus concentrations. Results suggest that the lake will shift from oligotrophic (TLI = 2-3) to eutrophic (TLI = 4-5) as external loadings are increased eightfold over current baseline loads, corresponding to the potential land-use intensification in the catchment. This study provides a basis for use of model results in a decision-making process by outlining the environmental consequences of a series of land-use management options, and quantifying nutrient load limits needed to achieve defined trophic state objectives.
Chemical fractionation of lake sediments to determine the effects of land-use change on nutrient loading

NASA Astrophysics Data System (ADS)

Heathwaite, A. L.

1994-07-01

Lake studies allow contemporary sediment and nutrient dynamics to be placed in a historical context in order that trends and rates of change in catchment inputs may be calculated. Here, a synthesis of the temporal information contained in catchment and lake sediment records is attempted. A chemical fractionation technique is used to isolate the different sediment sources contained in the lake core, and 210Pb dates provide an accurate record of changes in lake sediment sources over the past 100 years. The extent to which land-use records, collated from agricultural census returns, and process-based studies of sediment and nutrient export from different catchment land uses can be used to explain the trends observed in the lake sediments is examined. Sediment influx to the study lake has increased from less than 2 mm year -1 prior to the Second World War to over 10 mm year -1 at present. The source of the sediment is largely unaltered and unweathered allochthonous material eroded from the catchment. Land-use records suggest that the intensification of agriculture, characterized by a shift towards arable land immediately postwar, followed by an increase in the area of temporary grass in the 1960s, may be the cause of accelerated catchment erosion; both land-use changes would have increased the area of ploughed land in the catchment. An increase in the number of cattle and sheep in the catchment from around 2000 and 6000, respectively, in the 1940s, to a peak of nearly 7000 cattle and over 15 000 sheep in the 1980s, provides a further source of sediment and nutrients. Livestock are grazed on permanent grassland which is commonly located on steep hillslopes and in riparian zones where saturation-excess surface runoff may be an important hydrological pathway. Rainfall simulation experiments show that surface runoff from heavily grazed grassland has a high suspended sediment, ammonium-nitrogen and particulate phosphorus load. The combined effect of the long-term increase in the organic loading from livestock and the inorganic N and P load from fertilizers, may be the source of nutrient enrichment in the lake.
Perylene in Lake Biwa sediments originating from Cenococcum geophilum in its catchment area

NASA Astrophysics Data System (ADS)

Itoh, Nobuyasu; Sakagami, Nobuo; Torimura, Masaki; Watanabe, Makiko

2012-10-01

Perylene, which is composed of five benzene rings, is commonly found in sediments throughout the world at concentrations and distributions that are different from those of other polycyclic aromatic hydrocarbons. The only information available on the origin of perylene comes from 4,9-dihydroxyperylene-3,10-quinone (DHPQ), which originates from fungal component symbiosis or from parasites on plants; however, there is no direct evidence of a mechanism of perylene formation. In this study, we examined the relationship between sedimentary perylene and Cenococcum geophilum (C. geophilum) in a catchment area at Lake Biwa. Sclerotium grains of C. geophilum containing DHPQ were found in this catchment area (approximately 40 balls kg-1 dried soil for >1 mm-ϕ), and small sclerotium grains were frequently found in the sediment. In the sediment sample, we also found broken particles containing perylene, and they had a porous structure characteristic of sclerotium grains. Furthermore, the particles contained DHPQ in different transformation stages to perylene via 3,10-perylenequinone (3,10-PQ). This finding was consistent with results from elemental analysis (oxygen/carbon). Because a remarkable amount of DHPQ originating from C. geophilum also exists in the humic acids of soils and because the inputs of compounds to the lake depend strongly on the rivers, perylene in the Lake Biwa sediment originates mainly from the DHPQ of C. geophilum in its catchment area.
Modelling catchment hydrological responses in a Himalayan Lake as a function of changing land use and land cover

NASA Astrophysics Data System (ADS)

Badar, Bazigha; Romshoo, Shakil A.; Khan, M. A.

2013-04-01

In this paper, we evaluate the impact of changing land use/land cover (LULC) on the hydrological processes in Dal lake catchment of Kashmir Himalayas by integrating remote sensing, simulation modelling and extensive field observations. Over the years, various anthropogenic pressures in the lake catchment have significantly altered the land system, impairing, inter-alia, sustained biotic communities and water quality of the lake. The primary objective of this paper was to help a better understanding of the LULC change, its driving forces and the overall impact on the hydrological response patterns. Multi-sensor and multi-temporal satellite data for 1992 and 2005 was used for determining the spatio-temporal dynamics of the lake catchment. Geographic Information System (GIS) based simulation model namely Generalized Watershed Loading Function (GWLF) was used to model the hydrological processes under the LULC conditions. We discuss spatio-temporal variations in LULC and identify factors contributing to these variations and analyze the corresponding impacts of the change on the hydrological processes like runoff, erosion and sedimentation. The simulated results on the hydrological responses reveal that depletion of the vegetation cover in the study area and increase in impervious and bare surface cover due to anthropogenic interventions are the primary reasons for the increased runoff, erosion and sediment discharges in the Dal lake catchment. This study concludes that LULC change in the catchment is a major concern that has disrupted the ecological stability and functioning of the Dal lake ecosystem.
Assessment of Wetland Hydrological Dynamics in a Modified Catchment Basin: Case of Lake Buninjon, Victoria, Australia.

PubMed

Yihdego, Yohannes; Webb, John A

2017-02-01

The common method to estimate lake levels is the water balance equation, where water input and output result in lake storage and water level changes. However, all water balance components cannot always be quickly assessed, such as due to significant modification of the catchment area. A method that assesses general changes in lake level can be a useful tool in examining why lakes have different lake level variation patterns. Assessment of wetlands using the dynamics of the historical hydrological and hydrogeological data set can provide important insights into variations in wetland levels in different parts of the world. A case study from a saline landscape, Lake Buninjon, Australia, is presented. The aim of the present study was to determine how climate, river regime, and lake hydrological properties independently influence lake water levels and salinity, leaving the discrepancy, for the effect of the non-climatic/catchment modification in the past and the model shows that surface inflow is most sensitive variable. The method, together with the analysis and interpretation, might be of interest to wider community to assess its response to natural/anthropogenic stress and decision choices for its ecological, social, scientific value, and mitigation measures to safe guard the wetland biodiversity in a catchment basin.
Legacy effects of nitrogen and phosphorus in a eutrophic lake catchment: Slapton Ley, SW England

NASA Astrophysics Data System (ADS)

Burt, T. P.; Worrall, F.; Howden, N. J. K.

2017-12-01

Slapton Ley is a freshwater coastal lagoon in SW England. The Ley is part of a National Nature Reserve, which is divided into two basins: the Higher Ley (39 ha) is mainly reed swamp; the Lower Ley (77 ha) is a shallow lake (maximum depth 2.9 m). In the 1960s it became apparent that the Lower Ley was becoming increasingly eutrophic. In order to gauge water, sediment and nutrient inputs into the lake, measurements began on the main catchments in 1969. Continuous monitoring of discharge and a weekly water-sampling programme have been maintained by the Slapton Ley Field Centre ever since. The monitoring programme has been supplemented by a number of research projects which have sought to identify the salient hydrological processes operating within the Slapton catchments and to relate these to the delivery of sediment and solute to the stream system. Long-term monitoring data are also available for the catchment area including the lake from the Environment Agency.The nitrate issue has been of particular interest at Slapton; although many longer series exist for large river basins like the Thames, the long record of nitrate data for the Slapton catchments is unique in Britain for a small rural basin. Recent declines in nitrate concentration may reflect less intensive agricultural activity, lower fertiliser inputs in particular, but there may also be a legacy effect in the shallow groundwater system. Phosphorus concentrations in stream and lake water have also shown declining concentrations but a phosphorus legacy in the surficial lake sediments means that algal blooms continue to develop in most summers, as indicated by a continued rise in summer pH levels. Further field observation at the sediment-water interface is needed to better understand the biogeochemical drivers and the balance between N and P limitation in the lake. Successful management of the Nature Reserve requires better understanding of the links between hydrological and biogeochemical processes operating within the catchment area.
The Lake-Catchment (LakeCat) Dataset for characterizing hydrologically-relevant landscape features for lakes across the conterminous US

EPA Science Inventory

Lake conditions, including their biota, respond to both natural and human-related landscape features. Characterizing these features within the contributing areas (i.e., delineated watersheds) of lakes could improve the analysis and the sustainable use and management of these impo...

Mercury pollution in the lake sediments and catchment soils of anthropogenically-disturbed sites across England.

PubMed

Yang, Handong; Turner, Simon; Rose, Neil L

2016-12-01

Sediment cores and soil samples were taken from nine lakes and their catchments across England with varying degrees of direct human disturbance. Mercury (Hg) analysis demonstrated a range of impacts, many from local sources, resulting from differing historical and contemporary site usage and management. Lakes located in industrially important areas showed clear evidence for early Hg pollution with concentrations in sediments reaching 400-1600 ng g -1 prior to the mid-19th century. Control of inputs resulting from local management practices and a greater than 90% reduction in UK Hg emissions since 1970 were reflected by reduced Hg pollution in some lakes. However, having been a sink for Hg deposition for centuries, polluted catchment soils are now the major Hg source for most lakes and consequently recovery from reduced Hg deposition is being delayed. Copyright © 2016 Elsevier Ltd. All rights reserved.
Hydrology-based understanding of Ontario Lacus in Titan's south pole

NASA Astrophysics Data System (ADS)

Dhingra, Rajani D.; Barnes, Jason W.; Yanites, Brian J.; Kirk, Randolph L.

2015-11-01

Ontario Lacus is the largest presently filled lake at the south pole of Titan. Many other large basins in south pole exist at lower elevations than Ontario Lacus but are currently empty. To find out what sets Ontario apart from those empty basins, we have carried a detailed hydrological assessment of Ontario Lacus. Topography of the region, as derived from Cassini RADAR altimetry was used to determine the catchment area of Ontario Lacus. We could map the areal extent of catchments as far as southern mid-latitudes. Clouds in southern mid and high latitudes have been observed by Cassini VIMS which indicate possible precipitation in those regions. Precipitation in southern mid-latitudes coupled with the large catchment areas of Ontario Lacus could be the reason behind it being filled. Our mass conservation calculations indicate that if runoff was the only contributor to the lake volume, then the lake might be filled within one Titan year (29.5 Earth years) in entirety. We also observe a non-linear relationship between the longest identifiable stream and the catchment area (Hack's Law) which is consistent with terrestrial hydrological systems and may help in further interpretation of the hydrology of Ontario Lacus.
Morphology, geology and water quality assessment of former tin mining catchment.

PubMed

Ashraf, Muhammad Aqeel; Maah, Mohd Jamil; Yusoff, Ismail

2012-01-01

Bestari Jaya, former tin mining catchment covers an area of 2656.31 hectares comprised of four hundred and forty-two different-size lakes and ponds. The present study area comprise of 92 hectares of the catchment that include four large size lakes. Arc GIS version 9.2 used to develop bathymetric map, Global Positioning System (GPS) for hydrographical survey and flow meter was utilized for water discharge analysis (flow routing) of the catchment. The water quality parameters (pH, temperature, electric conductivity, dissolved oxygen DO, total dissolved solids TDS, chlorides, ammonium, nitrates) were analyzed by using Hydrolab. Quality assurance (QA) and quality control (QC) procedures were strictly followed throughout the field work and data analysis. Different procedures were employed to evaluate the analytical data and to check for possible transcription or dilution errors, changes during analysis, or unusual or unlikely values. The results obtained are compared with interim national water quality standards for Malaysia indicates that water quality of area is highly degraded. It is concluded that Bestri Jaya ex-mining catchment has a high pollution potential due to mining activities and River Ayer Hitam, recipient of catchment water, is a highly polluted river.
Morphology, Geology and Water Quality Assessment of Former Tin Mining Catchment

PubMed Central

Ashraf, Muhammad Aqeel; Maah, Mohd. Jamil; Yusoff, Ismail

2012-01-01

Bestari Jaya, former tin mining catchment covers an area of 2656.31 hectares comprised of four hundred and forty-two different-size lakes and ponds. The present study area comprise of 92 hectares of the catchment that include four large size lakes. Arc GIS version 9.2 used to develop bathymetric map, Global Positioning System (GPS) for hydrographical survey and flow meter was utilized for water discharge analysis (flow routing) of the catchment. The water quality parameters (pH, temperature, electric conductivity, dissolved oxygen DO, total dissolved solids TDS, chlorides, ammonium, nitrates) were analyzed by using Hydrolab. Quality assurance (QA) and quality control (QC) procedures were strictly followed throughout the field work and data analysis. Different procedures were employed to evaluate the analytical data and to check for possible transcription or dilution errors, changes during analysis, or unusual or unlikely values. The results obtained are compared with interim national water quality standards for Malaysia indicates that water quality of area is highly degraded. It is concluded that Bestri Jaya ex-mining catchment has a high pollution potential due to mining activities and River Ayer Hitam, recipient of catchment water, is a highly polluted river. PMID:22761549
Anthropogenic Sources of Arsenic and Copper to Sediments of a Suburban Lake, 1964-1998

NASA Astrophysics Data System (ADS)

Rice, K. C.; Conko, K. M.; Hornberger, G. M.

2002-05-01

Nonpoint-source pollution from urbanization is becoming a widespread problem. Long-term monitoring data are necessary to document geochemical processes in urban settings and changes in sources of chemical contaminants over time. In the absence of long-term data, lake-sediment cores can be used to reconstruct past processes, because they serve as integrators of sources of pollutants from the contributing airshed and catchment. Lake Anne is a 10.9-ha man-made lake in a 235-ha suburban catchment in Reston, Virginia, with a population density of 1,116 people/km2. Three sediment cores, collected in 1996 and 1997, indicate increasing concentrations of arsenic and copper since 1964, when the lake was formed. The cores were compared to a core collected from a forested catchment in the same airshed that showed no increases in concentrations of these elements. Neither an increase in atmospheric deposition nor diagenesis and remobilization were responsible for the trends in the Lake Anne cores. Mass balances of sediment, arsenic, and copper were calculated using 1998 data on precipitation, streamwater, road runoff, and a laboratory leaching experiment on pressure-treated lumber. Sources of arsenic to the lake in 1998 were in-lake leaching of pressure-treated lumber (52%) and streamwater (47%). Road runoff was a greater (93%) source of copper than leaching of pressure-treated lumber (4%). Atmospheric deposition was an insignificant source (<3%) of both elements. Urbanization of the catchment was confirmed as a major cause of the increasing arsenic and copper in the lake cores through an annual historical reconstruction of the deposition of sediment, arsenic, and copper to the lake for 1964-1997. Aerial photography indicated that the area of roads and parking lots in the catchment increased to 26% by 1997 and that the number of docks on the lake also increased over time. The increased mass of arsenic and copper in the lake sediments corresponded to the increased amount of pressure-treated lumber in the lake, and the mass of copper also corresponded to the increase in paved surfaces in the catchment.
Impact of papyrus wetland encroachment on spatial and temporal variabilities of stream flow and sediment export from wet tropical catchments.

PubMed

Ryken, N; Vanmaercke, M; Wanyama, J; Isabirye, M; Vanonckelen, S; Deckers, J; Poesen, J

2015-04-01

During the past decades, land use change in the Lake Victoria basin has significantly increased the sediment fluxes to the lake. These sediments as well as their associated nutrients and pollutants affect the food and water security of millions of people in one of Africa's most densely populated regions. Adequate catchment management strategies, based on a thorough understanding of the factors controlling runoff and sediment discharge are therefore crucial. Nonetheless, studies on the magnitude and dynamics of runoff and sediment discharge are very scarce for the Lake Victoria basin and the African Rift region. We therefore conducted runoff discharge and sediment export measurements in the Upper Rwizi, a catchment in Southwest Uganda, which is representative for the Lake Victoria basin. Land use in this catchment is characterized by grazing area on the high plateaus, banana cropping on the slopes and Cyperus papyrus L. wetlands in the valley bottoms. Due to an increasing population pressure, these papyrus wetlands are currently encroached and transformed into pasture and cropland. Seven subcatchments (358 km2-2120 km2), with different degrees of wetland encroachment, were monitored during the hydrological year June 2009-May 2010. Our results indicate that, due to their strong buffering capacity, papyrus wetlands have a first-order control on runoff and sediment discharge. Subcatchments with intact wetlands have a slower rainfall-runoff response, smaller peak runoff discharges, lower rainfall-runoff ratios and significantly smaller suspended sediment concentrations. This is also reflected in the measured annual area-specific suspended sediment yields (SYs): subcatchments with encroached papyrus swamps have SY values that are about three times larger compared to catchments with intact papyrus vegetation (respectively 106-137 ton km(-2) y(-1) versus 34-37 ton km(-2) y(-1)). We therefore argue that protecting and (where possible) rehabilitating these papyrus wetlands should be a corner stone of catchment management strategies in the Lake Victoria basin. Copyright © 2014 Elsevier B.V. All rights reserved.
A catchment-scale palaeolimnological investigation into multiple forcings of algal community change

NASA Astrophysics Data System (ADS)

Moorhouse, H. L.; McGowan, S.; Jones, M.; Brayshaw, S.; Barker, P.; Leavitt, P.

2013-12-01

A catchment-scale palaeolimnological investigation of sedimentary algal pigments spanning the past ~200 years was undertaken on lakes which drain into Windermere, England's largest and longest lake. We aimed to determine the relative influence of past regional (climatic, atmospheric deposition) and local (land-use, hydrological modification, point-source pollution) drivers of algal community change by comparing three fertile lowland lakes (Blelham Tarn, Esthwaite Water and Rydal Water) and two upland tarns (Stickle and Easedale Tarns) to better inform a catchment-wide management strategy for Windermere. Drivers of change at the upland sites included atmospheric acid deposition, climatic change and structural modifications caused by dam installation, whereas the influence of agriculture and point-source pollution is greater in the lakes in the lowland parts of the catchment. As a result, contrasting algal responses were noted in the lakes. For example, the cyanobacterial pigment zeaxanthin and the cryptophte pigment alloxanthin increased at Stickle Tarn (359% and 321% respectively) corresponding with the establishment of a dam at the outflow of the tarn in 1838. However, post-1900's the concentration of these pigments declined both at Stickle and at Easedale Tarn coincident with increased storm events and in the later decades of the century (~1980s onwards) decreases in acid deposition. In the lowland sites the cyanobacterial pigment aphanizophyll increased by 400-7000% and the indicator of total algal production β-carotene increased as much as six-fold indicating a substantial degradation in water quality and the onset of cyanobacterial blooms since the 1950's. In the lowland sites, degradation of water quality was closely linked to sewage installations and treatment work upgrades during the 1950's-70's and intensification of agricultural practices most notably increases in sheep stocking densities, which expanded in the 1950's. In lowland lakes with a higher catchment: lake area ratio, climate (specifically precipitation) had a more demonstrable impact on algal communities, through enhanced delivery of catchment nutrients. Therefore, we have identified water-bodies likely to be most 'at-risk' from future climate change, in order to advise on tailored management strategies for individual lakes within the catchment.
Empirical quantification of lacustrine groundwater discharge - different methods and their limitations

NASA Astrophysics Data System (ADS)

Meinikmann, K.; Nützmann, G.; Lewandowski, J.

2015-03-01

Groundwater discharge into lakes (lacustrine groundwater discharge, LGD) can be an important driver of lake eutrophication. Its quantification is difficult for several reasons, and thus often neglected in water and nutrient budgets of lakes. In the present case several methods were applied to determine the expansion of the subsurface catchment, to reveal areas of main LGD and to identify the variability of LGD intensity. Size and shape of the subsurface catchment served as a prerequisite in order to calculate long-term groundwater recharge and thus the overall amount of LGD. Isotopic composition of near-shore groundwater was investigated to validate the quality of catchment delineation in near-shore areas. Heat as a natural tracer for groundwater-surface water interactions was used to find spatial variations of LGD intensity. Via an analytical solution of the heat transport equation, LGD rates were calculated from temperature profiles of the lake bed. The method has some uncertainties, as can be found from the results of two measurement campaigns in different years. The present study reveals that a combination of several different methods is required for a reliable identification and quantification of LGD and groundwater-borne nutrient loads.
Large catchment area recharges Titan's Ontario Lacus

NASA Astrophysics Data System (ADS)

Dhingra, Rajani D.; Barnes, Jason W.; Yanites, Brian J.; Kirk, Randolph L.

2018-01-01

We seek to address the question of what processes are at work to fill Ontario Lacus while other, deeper south polar basins remain empty. Our hydrological analysis indicates that Ontario Lacus has a catchment area spanning 5.5% of Titan's surface and a large catchment area to lake surface area ratio. This large catchment area translates into large volumes of liquid making their way to Ontario Lacus after rainfall. The areal extent of the catchment extends to at least southern mid-latitudes (40°S). Mass conservation calculations indicate that runoff alone might completely fill Ontario Lacus within less than half a Titan year (1 Titan year = 29.5 Earth years) assuming no infiltration. Cassini Visual and Infrared Mapping Spectrometer (VIMS) observations of clouds over the southern mid and high-latitudes are consistent with precipitation feeding Ontario's large catchment area. This far-flung rain may be keeping Ontario Lacus filled, making it a liquid hydrocarbon oasis in the relatively dry south polar region.
Sources and Fate of Chiral Organochlorine Pesticides in Western U.S. National Park Ecosystems

PubMed Central

Genualdi, Susan A.; Hageman, Kimberly J.; Ackerman, Luke K.; Usenko, Sascha; Simonich, Staci L. Massey

2011-01-01

The enantiomer fractions (EFs) of alpha-hexachlorocyclohexane (α-HCH), cis-, trans-, and oxychlordane, and heptachlor epoxide were measured in 73 snow, fish, and sediment samples collected from remote lake catchments, over a wide range of latitudes, in seven western U.S. National Parks/Preserves in order to investigate their sources, fate, accumulation and biotransformation in these ecosystems. The present study is novel because these lakes had no inflow or outflow and the measurement of chiral organochlorine pesticides (OCPs) EFs in snowpack from these lake catchments provided a better understanding of the OCP sources in the Western U.S., while their measurement in fish and sediment provided a better understanding of their biotic transformations within the lake catchments. Non-racemic α-HCH was measured in seasonal snowpack collected from continental U.S. National Parks, while racemic α-HCH was measured in seasonal snowpack collected from the Alaskan parks, suggesting the influence of regional sources to the continental U.S. parks and long-range sources to the Alaskan parks. The α-HCH EFs measured in trout collected from the lake catchments were similar to the α-HCH EFs measured in seasonal snowpack collected from the same lake catchments, suggesting that these fish did not biotransform α-HCH enantioselectively. Racemic cis-chlordane was measured in seasonal snowpack and sediment collected from Sequoia, indicating that it had not undergone significant enantioselective biotransformation in urban soils since its use as a termiticide in the surrounding urban areas. However, non-racemic cis-chlordane was measured in seasonal snowpack and sediments from Rocky Mountain, suggesting cis-chlordane does undergo enantioselective biotransformation in agricultural soils. The trout from these lakes showed preferential biotransformation of the (+)-enantiomer of cis-chlordane and the (−)-enantiomer of trans-chlordane. PMID:21462235
Some climatological factors of pine in the lake toba catchment area

NASA Astrophysics Data System (ADS)

Nasution, Z.

2018-02-01

The article deals with climatological factors of Pine at the Lake Toba Catchment Area also called drained basin, Pinus merkusii is a plant endemic in Sumatra. A central population of Pine in North Sumatra is located in the Tapanuli region to south of Lake Toba. Junghuhn discovered the species in the mountains range of Sipirok. He provisionally named the species as Pinus sumatrana. The article presents a detail analysis of approaches to climate factors, considers rainfall, air temperature, humidity, stemflow, throughfall and Interception following calculation of regression to determine relationship between precipitation with stemflow and interception. Stemflow, it is highly significant with significance of difference between correlation coefficients and z normal distribution. Temperature and relative humidity are the important components in the climate. These components influence the evaporation process and rainfall in the catchment. Pinus merkusii has the big crown interception. Stemflow and Interception has an opposite relation. Increasing of interception capacity will decrease stemflow. This type of Pine also has rough bark however significant channels so that, it flows water even during the wet season and caused the stemflow in Pinus merkusii relatively bigger.
Long-term scientific benefits from preserving old-growth hemlock stands at Clear Lake near Minden, Ontario, Canada

Treesearch

R. A. Reid; K. M. Somers; J. E. Nighswander; A. M. Zobel

2000-01-01

Clear Lake is located in the centre of the 1300 ha Clear Lake Conservation Reserve in Haliburton County, Ontario, Canada. In 1988, the reserve was designated as a protected area representing undisturbed, old-growth ecosystems. The reserve includes several headwater lakes and their associated catchments which support old-growth hemlock stands that are estimated to be up...
Permafrost and lakes control river isotope composition across a boreal Arctic transect in the Western Siberian lowlands

NASA Astrophysics Data System (ADS)

Ala-aho, P.; Soulsby, C.; Pokrovsky, O. S.; Kirpotin, S. N.; Karlsson, J.; Serikova, S.; Manasypov, R.; Lim, A.; Krickov, I.; Kolesnichenko, L. G.; Laudon, H.; Tetzlaff, D.

2018-03-01

The Western Siberian Lowlands (WSL) store large quantities of organic carbon that will be exposed and mobilized by the thawing of permafrost. The fate of mobilized carbon, however, is not well understood, partly because of inadequate knowledge of hydrological controls in the region which has a vast low-relief surface area, extensive lake and wetland coverage and gradually increasing permafrost influence. We used stable water isotopes to improve our understanding of dominant landscape controls on the hydrology of the WSL. We sampled rivers along a 1700 km South-North transect from permafrost-free to continuous permafrost repeatedly over three years, and derived isotope proxies for catchment hydrological responsiveness and connectivity. We found correlations between the isotope proxies and catchment characteristics, suggesting that lakes and wetlands are intimately connected to rivers, and that permafrost increases the responsiveness of the catchment to rainfall and snowmelt events, reducing catchment mean transit times. Our work provides rare isotope-based field evidence that permafrost and lakes/wetlands influence hydrological pathways across a wide range of spatial scales (10-105 km2) and permafrost coverage (0%-70%). This has important implications, because both permafrost extent and lake/wetland coverage are affected by permafrost thaw in the changing climate. Changes in these hydrological landscape controls are likely to alter carbon export and emission via inland waters, which may be of global significance.
Phosphorus Loadings to the World's Largest Lakes: Sources and Trends

NASA Astrophysics Data System (ADS)

Fink, Gabriel; Alcamo, Joseph; Flörke, Martina; Reder, Klara

2018-04-01

Eutrophication is a major water quality issue in lakes worldwide and is principally caused by the loadings of phosphorus from catchment areas. It follows that to develop strategies to mitigate eutrophication, we must have a good understanding of the amount, sources, and trends of phosphorus pollution. This paper provides the first consistent and harmonious estimates of current phosphorus loadings to the world's largest 100 lakes, along with the sources of these loadings and their trends. These estimates provide a perspective on the extent of lake eutrophication worldwide, as well as potential input to the evaluation and management of eutrophication in these lakes. We take a modeling approach and apply the WorldQual model for these estimates. The advantage of this approach is that it allows us to fill in large gaps in observational data. From the analysis, we find that about 66 of the 100 lakes are located in developing countries and their catchments have a much larger average phosphorus yield than the lake catchments in developed countries (11.1 versus 0.7 kg TP km-2 year-1). Second, the main source of phosphorus to the examined lakes is inorganic fertilizer (47% of total). Third, between 2005-2010 and 1990-1994, phosphorus pollution increased at 50 out of 100 lakes. Sixty percent of lakes with increasing pollution are in developing countries. P pollution changed primarily due to changing P fertilizer use. In conclusion, we show that the risk of P-stimulated eutrophication is higher in developing countries.
Sources of core and intact branched tetraether membrane lipids in the lacustrine environment: Anatomy of Lake Challa and its catchment, equatorial East Africa

NASA Astrophysics Data System (ADS)

Buckles, Laura K.; Weijers, Johan W. H.; Verschuren, Dirk; Sinninghe Damsté, Jaap S.

2014-09-01

The MBT/CBT palaeotemperature proxy uses the distribution of branched glycerol dialkyl glycerol tetraethers (brGDGTs), membrane lipids that are supposed to derive from soil bacteria, to reconstruct mean annual air temperature (MAAT). Applied successfully in coastal marine sediments, its extension to lake-sediment records with potentially high time resolution would greatly expand its utility. Over the last years, however, studies have indicated the presence of additional sources of brGDGTs within lake systems. To constrain the factors influencing the MBT/CBT palaeotemperature proxy in lakes, detailed investigation of brGDGT fluxes in a modern lake system is necessary to identify their potential sources. This study concentrates on Lake Challa, a permanently stratified crater lake in equatorial East Africa with limited catchment area. An almost 3-year time series of approximately monthly samples of settling particles, supplemented with a depth profile of suspended particulate matter (SPM) and sets of profundal surface-sediment and catchment soil samples, were analysed for both the 'living' intact polar lipids (IPLs) and 'fossil' core lipids (CLs) of GDGTs. We found that brGDGTs are produced in oxic, suboxic and anoxic zones of the water column, and in substantial amounts compared to influxes from catchment soils. Additional in situ production within the lake sediments is most probable, but cannot be definitely confirmed at this time. These lacustrine brGDGTs display a different response to temperature variation than soil-derived brGDGTs, signifying either a different physiological adaptation to changing conditions within the water column and/or a different composition of the respective bacterial communities. Using this specific relationship with temperature, a local calibration based on brGDGT distributions in SPM generates relatively accurate water temperature estimates from settling particles but fails for surface sediments.
Mercury concentrations in fish from forest harvesting and fire-impacted Canadian Boreal lakes compared using stable isotopes of nitrogen.

PubMed

Garcia, Edenise; Carignan, Richard

2005-03-01

Total mercury (Hg) concentration was determined in several piscivorous and nonpiscivorous species of fish from 38 drainage lakes with clear-cut, burnt, or undisturbed catchments located in the Canadian Boreal Shield. Mercury concentrations increased with increasing fish trophic position as estimated using stable isotopes of nitrogen (N; r2 = 0.52, 0.49, and 0.30 for cut, reference, and burnt lakes, respectively; p < 0.01). Mercury biomagnification per thousand delta15N varied from 22 to 29% in the three groups of lakes. Mercury availability to organisms at the base of the food chain in lakes with cut catchments was higher than that in reference lakes. In cut lakes, Hg concentrations in fish were significantly related to ratio of the clear-cut area to lake area (or lake volume; r = +0.82 and +0.74, respectively, p < 0.01). Both impact ratios were, in turn, significantly correlated with dissolved organic carbon. These findings suggest that differential loading of organic matter-bound Hg to lakes can affect Hg cycling. In addition, Hg concentrations exceeded the advisory limit for human consumption (0.5 microg/g wet wt) from the World Health Organization in all top predatory species (northern pike, walleye, and burbot) found in cut and in two partially burnt lakes. Thus, high Hg concentrations in fish from forest-harvested and partially burnt lakes may reflect increased exposure to Hg relative to that in lakes not having these watershed disturbances.
New estimated Holocene denudation rates for non-glaciated areas in the southernmost Patagonian Andes (53°S), Chile

NASA Astrophysics Data System (ADS)

Breuer, Sonja; Kilian, Rolf; Baeza, Oscar; Arz, Helge

2010-05-01

Cenozoic denudation rates are sparsely known for the southernmost Patagonian Andes. One of the scientific approaches is to calculate long-term denudation rates based on fission track analyses. Though, these average rates comprise a long period with distinct climate conditions and very different extend of glaciation. These integrated denudation rates include extensive surface areas with different morphological, glacial and vegetational properties. In contrast, our approach is restricted to relative short Holocene periods and small catchment areas, for which the denudation and its controlling surface characteristics could be defined more precisely. Thus a more precise evaluation of the influencing parameters like climate, morphology and vegetation cover was possible. We concentrated on three restricted and nearly closed areas of denudation and accumulation. In those catchments we determined the sediment masses of lakes, based on sediment drilling, echosounding and computer based interpolation of the siliciclastic sediment masses. These masses were transferred to the denudation areas which have been characterised and measured by remote sensing. The westernmost Tamar Lake is located on the Tamar Island in the western part of the Magellan Strait, where the annual precipitation is about 4,000 mm. The catchment area has a dense vegetation cover. The lake surrounding slopes reach an elevation of 400 m a.s.l and they are up to 60° steep. The calculated denudation rate for this catchment is about 2.56 mm/ka, which represents a minimum value, because the postglacial weathering horizon is only partly removed into the lake. The highest elevated lake Muy Profundo (500 m a.s.l.) possesses a denudation area with a nearly vegetation-free zone up to 750 m a.s.l. within the Patagonian Batholith. The catchment area of this lake is characterised by a roche moutonnée landform with steep slopes and active fracture zones. The precipitation varies between 5,000 and 8,000 mm/a. The denudation rates of the catchment amount to 0.42 mm/ka. Despite the high precipitation and the exposed position this denudation rate is unexpectedly low. Along the active fracture zones a stronger denudation could be observed by the occurrence of restricted gullies. The removed predominantly coarse clastic material is stored in alluvial cones and not included in our mass balance. The elevation of the catchment of the easternmost Chandler does not exceed 200 m a.s.l. and the area is characterised by a moderate relief with relatively flat slopes. The roche moutonnée landscape is interspersed with tracts of peat land and Magellanic rainforest. The precipitation ranges between 3,500 and 5,000 mm/a. Circulating acid soil water cause an intense chemical weathering and formed a 10-20 cm thick weathering horizon at the interface between bedrock and peaty soil. Due to the sediment core and the echosound stratigraphy, the denudation could be determined for two periods of time. The 2,040 cal. a BP tephra layer of the Mt. Burney volcano is the most distinct reflector in the echosound data. Therefore it was used as a sedimentation boundary. The denudation rates for the period 12,100 to ~2,000 and for the last 2000 years are very similar with ~2.55 mm/ka. On the basis of e.g. Ti/U enrichment in the weathering horizon, we conclude that the chemical denudation is very important in areas with vegetation cover in the superhumid Andes. In a long-term perspective, the relatively high denudation rates of low elevated peat land compared to the exposed rock surfaces may further increase the relief even during interglacial periods, like the Holocene. On the basis of our results we could state that the precipitation plays only a subordinated role as a control mechanism concerning the denudation in ice-free, but low temperate areas of the Patagonian Andes.
3D simulation of the influence of internal mixing dynamics on the propagation of river plumes in Lake Constance

NASA Astrophysics Data System (ADS)

Pflugbeil, Thomas; Pöschke, Franziska; Noffke, Anna; Winde, Vera; Wolf, Thomas

2017-04-01

Lake Constance is one of most important drinking water resources in southern Germany. Furthermore, the lake and its catchment is a meaningful natural habitat as well as economical and cultural area. In this context, sustainable development and conservation of the lake ecosystem and drinking water quality is of high importance. However, anthropogenic pressures (e.g. waste water, land use, industry in catchment area) on the lake itself and its external inflows are high. The project "SeeZeichen" (ReWaM-project cluster by BMBF, funding number 02WRM1365) is investigating different immission pathways (groundwater, river, superficial inputs) and their impact on the water quality of Lake Constance. The investigation includes the direct inflow areas as well as the lake-wide context. The present simulation study investigates the mixing dynamics of Lake Constance and its impacts on river inflows and vice versa. It considers different seasonal (mixing and stratification periods), hydrological (flood events, average and low discharge) and transport conditions (sediment loads). The simulations are focused on two rivers: The River Alpenrhein delivers about 60 % of water and material input into Lake Constance. The River Schussen was chosen since it is highly anthropogenic influenced. For this purpose, a high-resolution three-dimensional hydrodynamic model of the Lake Constance is set up with Delft3D-Flow model system. The model is calibrated and validated with long term data sets of water levels, discharges and temperatures. The model results will be analysed for residence times of river water within the lake and particle distributions to evaluate potential impacts of river plume water constituents on the general water quality of the lake.
Assessment of lake sensitivity to acidic deposition in national parks of the Rocky Mountains.

PubMed

Nanus, L; Williams, M W; Campbell, D H; Tonnessen, K A; Blett, T; Clow, D W

2009-06-01

The sensitivity of high-elevation lakes to acidic deposition was evaluated in five national parks of the Rocky Mountains based on statistical relations between lake acid-neutralizing capacity concentrations and basin characteristics. Acid-neutralizing capacity (ANC) of 151 lakes sampled during synoptic surveys and basin-characteristic information derived from geographic information system (GIS) data sets were used to calibrate the statistical models. The explanatory basin variables that were considered included topographic parameters, bedrock type, and vegetation type. A logistic regression model was developed, and modeling results were cross-validated through lake sampling during fall 2004 at 58 lakes. The model was applied to lake basins greater than 1 ha in area in Glacier National Park (n = 244 lakes), Grand Teton National Park (n = 106 lakes), Great Sand Dunes National Park and Preserve (n = 11 lakes), Rocky Mountain National Park (n = 114 lakes), and Yellowstone National Park (n = 294 lakes). Lakes that had a high probability of having an ANC concentration <100 microeq/L, and therefore sensitive to acidic deposition, are located in basins with elevations >3000 m, with <30% of the catchment having northeast aspect and with >80% of the catchment bedrock having low buffering capacity. The modeling results indicate that the most sensitive lakes are located in Rocky Mountain National Park and Grand Teton National Park. This technique for evaluating the lake sensitivity to acidic deposition is useful for designing long-term monitoring plans and is potentially transferable to other remote mountain areas of the United States and the world.
Soil surface lowering due to soil erosion in villages near Lake Victoria, Uganda

NASA Astrophysics Data System (ADS)

de Meyer, A.; Deckers, J.; Poesen, J.; Isabirye, M.

2009-04-01

In the effort to pinpoint the sources of sediment pollution in Lake Victoria, the contribution of sedi-ment from compounds, landing sites, main roads and footpaths is determined in the catchment of Na-bera Bay and Kafunda Bay at the northern shore of Lake Victoria in southern Uganda. The amount of soil loss in compounds and landing sites is determined by the reconstruction of the original and current soil surface according to botanical and man-made datable objects. The soil erosion rate is then deter-mined by dividing the eroded soil volume (corrected for compaction) by the age of the oldest datable object. In the study area, the average soil erosion rate in compounds amounts to 107 Mg ha-1 year-1 (per unit compound) and in landing sites to 207 Mg ha-1 year-1 (per unit landing site). Although com-pounds and landing sites occupy a small area of the study area (1.1 %), they are a major source of sediment to Lake Victoria (63 %). The soil loss on footpaths and main roads is calculated by multip-lying the total length of footpaths and main roads with the average width and depth (measured towards a reference surface). After the correction for compaction is carried out, the soil erosion rate on foot-paths amounts to 34 Mg ha-1 year-1 and on main roads to 35 Mg ha-1 year-1. Also footpaths and main roads occupy a small area of the study area (1.1 %), but contribute disproportionately to the total soil loss in the catchment (22 %). In this research, the information about the village/compound given by the villager/owner is indispensable. In accordance to an adaptation of the model of McHugh et al. (2002), 32 % of the sediment that is generated in the catchment, is deposited in Lake Victoria (i.e. 2 209 Mg year-1 or 0.7 Mg ha-1 year-1). The main buffer in the study area is papyrus at the shore of Lake Victoria. Also sugarcane can be a major buffer. However, the sugarcane-area is intersected by com-pounds, landing sites, footpaths and main roads that generate large amounts of sediment and function as main bypass mechanisms (high CR) facilitating and enhancing sediment delivery to Lake Victoria.

The Distribution of Antarctic Subglacial Lake Environments With Implications for Their Origin and Evolution

NASA Astrophysics Data System (ADS)

Blankenship, D. D.; Young, D. A.; Carter, S. P.

2006-12-01

Ice-penetrating radar records across the Antarctic Ice Sheet show regions with strong flat mirror-like reflections from the subglacial interface that are interpreted to be from subglacial lakes. The majority of subglacial lakes are found in East Antarctica, primarily in topographically low areas of basins beneath the thick ice divides. Occasionally lakes are observed "perched" at higher elevations within local depressions of rough morphological regions. In addition, a correlation between the "onset" of enhanced glacial flow and subglacial lakes was identified. The greatest concentration of known lakes was found in the vicinity of Dome C. A second grouping of lakes lying near Ridge B includes Lake Vostok and several smaller lakes. Subglacial lakes were also discovered near the South Pole, within eastern Wilkes Land, west of the Transantarctic Mountains, and within West Antarctica's Whitmore Mountains. Aside from Lake Vostok, typical lengths of subglacial lakes were found to range from a few to about 20 kilometers. A recent inventory includes 145 subglacial lakes. Approximately 81% of detected lakes lie at elevations less than a few hundred meters above sea level while the majority of the remaining lakes are "perched" at higher elevations. We present the locations from the subglacial lake inventory on local "ice divides" calculated from the satellite derived surface elevations with and find the distance of each lake from these divides. Most significantly, we found that 66% of the lakes identified lie within 50 km of a local ice divide and 88% lie within 100 km of a local divide. In particular, note that lakes located far from the Dome C/Ridge B cluster and even those associated with very narrow catchments lie either on or within a few tens of kilometers of the local divide marked by the catchment boundary. The distance correlation of subglacial lakes with local ice divides leads to a fundamental question for the evolution of subglacial lake environments: Does the evolving ice sheet control the location of subglacial lakes or does the fixed lithospheric character necessary for lake formation constrain the evolution of ice sheet catchments? To begin to answer these questions, we assess the distributions of classes of lakes defined by their reflection character. These classes include bright specular ("definite") lakes, dim specular lakes and bright non-specular ("fuzzy") lakes. Interestingly, it is the fuzzy lakes that do not strongly correlate with ice divides. We show specific examples of off-divide lake system hydrology from the Byrd Glacier catchment in East Antarctica and Kamb Ice Stream in West Antarctica.
Chemical composition of natural waters of contaminated area: The case for the Imandra Lake catchment (the Kola Peninsula)

NASA Astrophysics Data System (ADS)

Evtyugina, Z. A.; Guseva, N. V.; Kopylova, J. G.; A, Vorobeva D.

2016-03-01

The study of the current chemical composition of natural waters in the eastern and western parts of the Imandra Lake catchment was performed using ion chromatography, potentiometry and inductively coupled plasma mass spectrometry. It was found that the content of trace elements in the surface water is considerably higher than that in the groundwater. The nickel and copper concentrations exceed the background levels over 19 and 2 times respectively in groundwater, and 175 and 61 times in the surface waters. These data show that the Severonikel influences negatively air and surface water.
Sources and Deposition of Polycyclic Aromatic Hydrocarbons to Western U.S. National Parks

PubMed Central

USENKO, SASCHA; MASSEY SIMONICH, STACI L.; HAGEMAN, KIMBERLY J.; SCHRLAU, JILL E.; GEISER, LINDA; CAMPBELL, DON H.; APPLEBY, PETER G.; LANDERS, DIXON H.

2010-01-01

Seasonal snowpack, lichens, and lake sediment cores were collected from fourteen lake catchments in eight western U.S. National Parks and analyzed for sixteen polycyclic aromatic hydrocarbons (PAHs) in order to determine their current and historical deposition, as well as to identify their potential sources. Seasonal snowpack was measured to determine the current wintertime atmospheric PAH deposition; lichens were measured to determine the long-term, year around deposition; and the temporal PAH deposition trends were reconstructed using lake sediment cores dated using 210Pb and 137Cs. The fourteen remote lake catchments ranged from low-latitude catchments (36.6° N) at high elevation (2900 masl) in Sequoia National Park, CA to high-latitude catchments (68.4° N) at low elevation (427 masl) in the Alaskan Arctic. Over 75% of the catchments demonstrated statistically significant temporal trends in ΣPAH sediment flux, depending on catchment proximity to source regions and topographic barriers. The ΣPAH concentrations and fluxes in seasonal snowpack, lichens, and surficial sediment were 3.6 to 60,000 times greater in the Snyder Lake catchment of Glacier National Park than the other 13 lake catchments. The PAH ratios measured in snow, lichen, and sediment were used to identify a local aluminum smelter as a major source of PAHs to the Snyder Lake catchment. These results suggest that topographic barriers influence the atmospheric transport and deposition of PAHs in high-elevation ecosystems and that PAH sources to these national park ecosystems range from local point sources to diffuse regional and global sources. PMID:20465303
Catchment and atmospheric effects on acidity of lakes in the northeastern United States

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, R.B.; Anderson, D.S.; Rhodes, T.E.

1995-06-01

Sedimentary evidence from 12 lakes in northeastern United States reveals that both catchment and atmospheric processes have caused changes in lake acidity. Diatom remains indicate pH 5.2 to 5.8 (one lake 6.8) for one to two centuries before impacts on the catchment by Euro-americans. These low-alkalinity lakes were very sensitive to altered fluxes of base cations and acids. Several lakes increased in pH by 0.2 to 0.6 unit in the 1800s and early 1900s when their catchments were logged. Re-acidification of some of the lakes was initially due to forest succession. Older sediment from one of the lakes also showsmore » alkalization by natural disturbance, and acidification paralleling forest succession. However, much of the recent acidification, to uniquely low levels by the 1970s is due to high sulfur deposition.« less
Monitoring Lake Victoria Water Quality from Space: Opportunities for Strengthening Trans-boundary Information Sharing for Effective Resource Management

NASA Astrophysics Data System (ADS)

Mugo, R. M.; Korme, T.; Farah, H.; Nyaga, J. W.; Irwin, D.; Flores, A.; Limaye, A. S.; Artis, G.

2014-12-01

Lake Victoria (LV) is an important freshwater resource in East Africa, covering 68,800 km2, and a catchment that spans 193,000km2. It is an important source of food, energy, drinking and irrigation water, transport and a repository for agricultural, human and industrial wastes generated from its catchment. For such a lake, and a catchment transcending 5 international boundaries, collecting data to guide informed decision making is a hard task. Remote sensing is currently the only tool capable of providing information on environmental changes at high spatio-temporal scales. To address the problem of information availability for LV, we tackled two objectives; (1) we analyzed water quality parameters retrieved from MODIS data, and (2) assessed land cover changes in the catchment area using Landsat data. We used L1A MODIS-Aqua data to retrieve lake surface temperature (LST), total suspended matter (TSM), chlorophyll-a (CHLa) and diffuse attenuation coefficient (KD490) in four temporal periods i.e. daily, weekly, monthly and seasonal scales. An Empirical Orthogonal Function (EOF) analysis was done on monthly data. An analysis of land cover change was done using Landsat data for 3 epochs in order to assess if land degradation contributes to water quality changes. Our results indicate that MODIS-Aqua data provides synoptic views of water quality changes in LV at different temporal scales. The Winam Gulf in Kenya, the shores of Jinja town in Uganda, as well as the Mwanza region in Tanzania represent water quality hotspots due to their relatively high TSM and CHLa concentrations. High levels of KD490 in these areas would also indicate high turbidity and thus low light penetration due to the presence of suspended matter, algal blooms, and/or submerged vegetation. The EOF analysis underscores the areas where LST and water color variability are more significant. The changes can be associated with corresponding land use changes in the catchment, where for instance wetlands are converted to croplands. On-going dissemination of our findings together with capacity building efforts with the three main fishery and research institutions working in the lake, will enable informed decision making for the water management of LV. Enhanced capacity in trans-boundary water resources research is critical for successful decision making.
Lakes-paleolakes cascade system and its role in shaping the runoff and chemical properties of water in the young-glacial catchment - example from the Tuchola Pinewood Forest (Northern Poland)

NASA Astrophysics Data System (ADS)

Gierszewski, Piotr; Brykała, Dariusz; Kaszubski, Michał; Plessen, Birgit

2016-04-01

The impact of paleolake basins, filled up with organic mineral deposits, in the transformation of the chemical properties of the outflow is generally ignored. Defining their role and importance in the water and matter cycles is one of the objectives of the hydrological and hydrochemical monitoring, which has been run in the catchment of Lake Czechowskie since mid-2012. The axis of the Lake Czechowskie catchment is a hydrographical system made of river and lake sections. Lake sections are not only present-day lakes (Głęboczek and Czechowskie), but also basins of the lakes functioned in the past, which are now biogenic plains. Lake sections of the system are connected by short valley sections, mostly of a gap character. The size and variability of surface water runoff from the basin is mainly affected by groundwater and the size of evaporation. Stable groundwater table provides stability of the river discharge, even during the periods of significant precipitation deficit. Groundwater fluctuation ranges registered during the period from May 2012 to September 2015 were between 0.17 and 1.25 m. The smallest were in the deepest piezometers located in watershed areas, and the largest in the shallow groundwater of lake terraces. The small dynamics of the groundwater states is reflected by slight fluctuations of water levels in Lake Czechowskie, which in the analyzed period amounted 0.40 cm. The surface of paleolake Trzechowskie, cut by a system of drainage ditches, is the area where an essential part of the surface runoff from the monitored catchment is formed. Large water resources in this part of the catchment are evidenced by the specific runoff value, which amounts to 25 dm3s-1km2. It is much larger than the whole basin specific runoff which reaches 11 dm3s-1km2. The measurements showed that the average surface runoff from Lake Czechowskie in the analyzed period was 0,065 m3s-1 and was similar to the size of the water influx via watercourses supplying the lake. On the basis of this value it was calculated that the theoretical time to replace the water in Lake Czechowskie is 2.8 years. The hydrochemical study showed that the studied ground- and surface waters represent the same bicarbonate-calcium-sulphate hydrochemical type. Against the background of a homogeneous ionic composition, the spatial variation of their overall salinity is very large. This is reflected by the values of electrolytic conductivity, which in the study period ranged from 76 to 1218 μSṡcm-1. The most mineralized (700-800 μSṡcm-1) are the waters of streams migrating in the organic-carbonate formations of the paleolakes and shallow groundwater in these areas. The lowest mineralization is showed by the groundwater circulating in sandy sediments of outwash plains. Mineralization of the Lake Czechowskie water of approx. 340 μSṡcm-1 is a result of supplying the lake from both sources and the effect of biogeochemical processes occurring in the lake. The hydrochemical monitoring results showed that the zones of water enrichment in salts are associated with paleolake basins filled with the organic-carbonate sediment, while the salt precipitation zones with lakes. The results of the study of matter flow in the basin of Lake Czechowskie showed that paleolakes equally affect the runoff volume and the transformation of the chemical properties of the water circulating in the basin as the lakes functioning today. The lakes and paleolakes create a cascade system of interconnected basins. Depending on the place they occupy in the cascade, their effect on the water circulation and transformation of matter is different. This study is a contribution to the Virtual Institute of Integrated Climate and Landscape Evolution Analyses - ICLEA- of the Helmholtz Association, Grant No VH-VI-415.
The impact of papyrus wetland encroachment on the spatial and temporal variability of stream flow and sediment export in the upper Rwizi catchment, Southwest Uganda

NASA Astrophysics Data System (ADS)

Ryken, Nick; Vanmaercke, Matthias; Wanyama, Joshua; Deckers, Jozef; Isabirye, Moses; Poesen, Jean

2014-05-01

During the past 30 years, human activities in the Lake Victoria basin are responsible for eutrophication of Lake Victoria via sediment-bound nutrients. This affects food security for millions on people. Addressing this problem in this densely populated region will require adequate catchment management strategies. However, sediment yield and runoff data to develop such a strategy are currently unavailable. Also in general, sediment yields for catchments in tropical environments are very scarce, especially in East-Africa. Therefore, runoff discharge and sediment export measurements were conducted in the upper Rwizi, a representative catchment for the Lake Victoria basin which is located in Southwest Uganda. Land use in this catchment is characterized by grazing area on the high plateaus, banana cropping on the slopes and Cyperus papyrus L. wetlands in the river valleys. These papyrus wetlands are currently encroached and transformed into cropland. Eight subcatchments (99 km2 - 2120 km2), with different degrees of wetland encroachment, were monitored during the hydrological year June 2009 - May 2010. Temporal and spatial variations in runoff discharge give strong indications that papyrus wetlands are crucial for buffering runoff and sediment discharge towards Lake Victoria. Subcatchments with intact wetlands show a slower runoff response to rainfall, smaller peak runoff discharges and lower runoff coefficients. Yearly runoff depths of subcatchment with intact wetlands are three to four times smaller compared to subcatchments with encroached wetlands. Suspended sediment concentrations (SSC) show a similar result, with significant smaller SSC in the subcatchments having intact papyrus wetlands. In the subcatchments where no encroachment occurred, annual area-specific suspended sediment yields (SSY) varied between 0,26 ton ha-1 yr-1and 0,33 ton ha-1 yr-1 , while the SSY of the encroached subcatchments varied between 1,20 ton ha-1 yr-1and 2,61 ton ha-1 yr-1. This study demonstrates that papyrus wetlands are crucial for buffering runoff and sediment discharges to Lake Victoria. Hence, measures should be taken to protect these wetlands.
Biogeochemical fluxes in the Glacier Lakes catchments

Treesearch

John O. Reuss; Frank A. Vertucci; Robert C. Musselman; Richard A. Sommerfeld

1993-01-01

These lakes are moderately sensitive to acid deposition; acidification would require precipitation at least as acidic as that presently found in the more heavily impacted areas of eastern North America. Because most snowpack contaminants are released early in the melting process, seasonal acidification pulses would probably occur at much lower levels of acidic inputs...
Temporal 222Rn distributions to reveal groundwater discharge into desert lakes: Implication of water balance in the Badain Jaran Desert, China

NASA Astrophysics Data System (ADS)

Luo, Xin; Jiao, Jiu Jimmy; Wang, Xu-sheng; Liu, Kun

2016-03-01

How lake systems are maintained and water is balanced in the lake areas in the Badain Jaran Desert (BJD), northeast of China have been debated for about a decade. In this study, continuous 222Rn measurement is used to quantify groundwater discharge into two representative fresh and brine water lakes in the desert using a steady-state mass-balance model. Two empirical equations are used to calculate atmospheric evasion loss crossing the water-air interface of the lakes. Groundwater discharge rates yielded from the radon mass balance model based on the two empirical equations are well correlated and of almost the same values, confirming the validity of the model. The fresh water and brine lakes have a daily averaged groundwater discharge rate of 7.6 ± 1.7 mm d-1 and 6.4 ± 1.8 mm d-1, respectively. The temporal fluctuations of groundwater discharge show similar patterns to those of the lake water level, suggesting that the lakes are recharged from nearby groundwater. Assuming that all the lakes have the same discharge rate as the two studied lakes, total groundwater discharge into all the lakes in the desert is estimated to be 1.59 × 105 m3 d-1. A conceptual model of water balance within a desert lake catchment is proposed to characterize water behaviors within the catchment. This study sheds lights on the water balance in the BJD and is of significance in sustainable regional water resource utilization in such an ecologically fragile area.
Nitrogen Concentrations and Exports in Baseflow and Stormflow from Three Small Urban Catchments in Central Florida

NASA Astrophysics Data System (ADS)

Luo, J.; Hochmuth, G.; Clark, M. W.

2014-12-01

Export of nitrogen from different watersheds across the United States is receiving increasing attention due to the impairment of water quality in receiving water bodies. Researchers have indicated that different land uses exerted a substantial influence on the water quality. Nitrogen loadings on the watershed scale are being studied in many large ecosystems, such as the Baltimore Ecosystem and Arizona Ecosystem, but only a few focuses in a smaller scale such as catchment scale. Characterization of the land use in catchment scale can better explain the observed environmental phenomena under the watershed scale and enrich the related watershed studies. Nitrogen fluxes have been studied at Lake Alice watershed in Gainesville, Florida with a focus on the rarely studied catchments such as sports fields with intensive fertilization management (SFC), urban area with reclaimed water irrigation (RWC) and urban area without irrigation (CC). The entire study started from May 2013. Discharge was monitored in the three catchments by transducers every 5 minutes. Regular biweekly grab samples in the three catchments were used to estimate the baseflow N loads, composite samples in 13 storms were collected to estimate the stormflow N loads. The results showed that in the baseflow, the average NO3-N concentration in SFC was 12.19 mg/l, which was significantly different from the urban catchments. Also there was a significant difference between the NO3-N concentrations in RWC (1.17 mg/l on average) and CC (0.60 mg/l on average). A separate log-log relationship was developed between discharge and N loads to estimate the baseflow N loads and stormflow N loads. It showed that baseflow contributed more N loads than stormflow in the three catchments in the annual N load. In conclusion, the recreational catchment received the greatest N load compared to the other catchments, so it should be the priority catchment when it comes to adopting nutrient management practices in the Lake Alice watershed.
TUM Critical Zone Observatory, Germany

NASA Astrophysics Data System (ADS)

Völkel, Jörg; Eden, Marie

2014-05-01

Founded 2011 the TUM Critical Zone Observatory run by the Technische Universität München and partners abroad is the first CZO within Germany. TUM CZO is both, a scientific as well as an education project. It is a watershed based observatory, but moving behind this focus. In fact, two mountainous areas are integrated: (1) The Ammer Catchment area as an alpine and pre alpine research area in the northern limestone Alps and forelands south of Munich; (2) the Otter Creek Catchment in the Bavarian Forest with a crystalline setting (Granite, Gneiss) as a mid mountainous area near Regensburg; and partly the mountainous Bavarian Forest National Park. The Ammer Catchment is a high energy system as well as a sensitive climate system with past glacial elements. The lithology shows mostly carbonates from Tertiary and Mesozoic times (e.g. Flysch). Source-to-sink processes are characteristic for the Ammer Catchment down to the last glacial Ammer Lake as the regional erosion and deposition base. The consideration of distal depositional environments, the integration of upstream and downstream landscape effects are characteristic for the Ammer Catchment as well. Long term datasets exist in many regards. The Otter Creek catchment area is developed in a granitic environment, rich in saprolites. As a mid mountainous catchment the energy system is facing lower stage. Hence, it is ideal comparing both of them. Both TUM CZO Catchments: The selected catchments capture the depositional environment. Both catchment areas include historical impacts and rapid land use change. Crosscutting themes across both sites are inbuilt. Questions of ability to capture such gradients along climosequence, chronosequence, anthroposequence are essential.
The response of sediment source and transfer dynamics to land use (change) in the Lake Manyara catchment

NASA Astrophysics Data System (ADS)

Wynants, Maarten; Munishi, Linus; Solomon, Henok; Grenfell, Michael; Taylor, Alex; Millward, Geoff; Boeckx, Pascal; Ndakidemi, Patrick; Gilvear, David; Blake, William

2017-04-01

The Lake Manyara basin in the East African Rift Region of Tanzania is considered to be an important driver for sustainable development in northern Tanzania in terms of biodiversity conservation, ecotourism, fisheries, pastoralism and (irrigation) agriculture. Besides local conservation, Lake Manyara National Park and its surroundings also have a vital function as a wildlife corridor connecting the Tarangire and Maasai steppe ecosystem with the entire northern Tanzania and Southern Kenya collective of national parks and ecosystems. However, driven by population pressure, increasing number of farmers are establishing agricultural operations in the catchment, causing a shift of the natural vegetation towards agricultural land. Furthermore, pastoralists with ever growing cattle stocks are roaming the grasslands, causing a decrease in soil structure due to overgrazing and compaction of the soil. We hypothesize that these processes increase the vulnerability to erosion, which presents a credible threat to ecosystem service provision, on the one hand the agricultural- and rangelands where loss of this finite resource threatens food security and people's livelihoods and on the other hand the water bodies, where siltation and eutrophication threatens the water quality and biodiversity. Knowledge of sediment source and transfer dynamics in the main tributaries of Lake Manyara and the response of these dynamics to land use (change) is critical to inform sustainable management policy decisions to maintain and enhance future food and water security. Using geochemical tracing techniques and Bayesian unmixing models we were able to attribute the lake sediment proportionally to its contributing tributaries. Furthermore, we were able to identify differences in erosion processes in different tributary systems using gamma spectrometry measurements of surface-elevated fallout radionuclides (137Cs and 210Pb). In our results we found that almost half of the sediment in the lake could be attributed to the Makuyuni river system, while it only covers about 15 percent of the total catchment area. Comparing these results to our land use data, it is striking that this system has the lowest percentage of protected area and forest cover, while having large areas of agricultural, grass- and shrub land. It thus seems that the erosion dynamics in the Manyara catchment are linked with land cover, however further research into historical changes in sediment fluxes and land use is needed to infer the human impact on these dynamics.
Elaboration of a complex GIS application in a catchment area.

PubMed

Németh, T; Szabó, J; Pásztor, L; Bakacsi, Zs

2002-01-01

Rearrangement of land resources after political changes has not yet been finished in Hungary. It is almost impossible to collect information necessary for planning activities on outer areas of settlements. The data are distributed among various organizations and can be found in diverse forms or there are no available data at all. However water quality protection has become legally ordered concerning municipal activities around Lake Balaton which is considered as the most important recreation area and tourist target in Hungary and is also affected by a number of factors providing sources of environmental conflicts. Settlements in a catchment area (Tetves Creek) on the southern shoreline of Lake Balaton in Central Hungary tendered a complex project for collecting sources of authentic data of the Hungarian rural areas along with systematizing and saving these data in a uniform GIS. An application using Autodesk MapGuide Program for Internet realization was developed. The implemented web-based system can be used in Internet and Intranet environments.
Lake level fluctuations and catchment dynamics at Lake Ohrid (Macedonia, Albania) during MIS6 and MIS5

NASA Astrophysics Data System (ADS)

Francke, Alexander; Wagner, Bernd; Just, Janna; Sadori, Laura; Masi, Alessia; Vogel, Hendrik; Lindhorst, Katja; Krastel, Sebastian; Dosseto, Anthony; Rothacker, Leo; Leicher, Niklas; Gromig, Raphael

2016-04-01

Lake Ohrid, presumably the oldest lake of Europe located at the border of Macedonia and Albania, is about 30 km long, 15 km wide, and up to 290 m deep. In 2013, an ICDP deep drilling campaign was carried out under the umbrella of the Scientific Collaboration on Past Speciation Conditions in Lake Ohrid (SCOPSCO) project. At the main drill site (DEEP) in the central part of Lake Ohrid, the uppermost 568 m from a total sediment fill of ca. 700 m were recovered. Initial data from core catcher material indicate that the sediment sequence covers more than 1.2 million years. An age model, which is based on 11 tephrostratigragphic tie points and on tuning of biogeochemical proxy data versus orbital parameters reveals that that the upper 247 m of the DEEP site sequence cover the time period between 637 ka (MIS16) and the present. Inhere, we present sedimentological, (bio-)geochemical, environmental magnetic, and pollen data for the time period between MIS6 (191 ka) and MIS5 (71 ka). The data imply that MIS6 was one of the most severe glacial periods, while MIS5 was likely one of the more pronounced interglacial during the past 637 kyrs. The repercussions of these high amplitude climatic and environmental variations during this period are recorded in the sedimentological archive of Lake Ohrid. Previous studies based on hydro-acoustic and sediment core data from the northeastern part of the lake basin have shown that the lake level of Lake Ohrid was likely 60 m lower during MIS6. The ˜60 m lower lake level at Lake Ohrid during MIS6 can at least partly be explained by the ongoing subsidence, which persists in the basin until today. However, in the DEEP site sediments, the MIS6/MIS5 transition occurs at ca. 50 m sediment depth. This implies that climate-induced lake level fluctuation at Lake Ohrid are less severe compared for example to Lake Van (Turkey), were a 260 m lower lake level has been reported for the Younger Dryas. The imprint of the environmental variations between 191 ka and 71 ka can also be seen in the catchment dynamics around the lake. Extraordinary high sedimentation rates, high clastic and negligible authigenic matter concentrations in DEEP site sediments during MIS6 imply enhanced erosion in the catchment. Thereby, elemental ratios (Zr/K) and environmental magnetic data (S-ratio) suggest that predominantly the products of chemical weathered, K-depleted old soils were transported into the lake. In contrast, a low sedimentation rate despite high authigenic matter concentrations during MIS5 implies less erosion in the catchment. In order to obtain more information about the catchment dynamics at Lake Ohrid, future studies will encompass the analyses of uranium and lithium isotopes. U isotopes (234U and 238U) can be used to assess the balance between deep and shallow erosion, while Li isotopes (7Li and 6Li) can inform on the extent of chemical weathering in the sediment source area. The application of these tools on a Late Glacial to Holocene record from Lake Dojran (Macedonia, Greece) has recently shown that climatic perturbations (8.2 and 4.2 cooling event) and anthropogenic land use have a direct impact on the catchment dynamics.
Changes in discharge dynamics under the constraints of local and global changes in the Chao Lake basin (China)

NASA Astrophysics Data System (ADS)

Chu, Y.; Salles, C.; Rodier, C.; Crès, F.-N.; Huang, L.; Tournoud, M.-G.

2012-04-01

Located on the Yangtze basin, the Chao Lake is the fifth largest freshwater lake in China and of great importance in terms of water resources and aquaculture. Its catchment (9130 km2) includes the city of Hefei and large extends of agricultural and rural areas. Fast changes are expected in land uses and agricultural practices for the future, due to the touristic appeal of the Chao Lake shore and the growth of the city of Hefei. Climate changes are also expected in this region, with a high impact on rainfall regime. The consequences of these changes on the sustainability of the water inflows into the lake are a major issue for the economical development of the Chao Lake area even though they are little-known. Our study aims to give tools for estimating such consequences, accounting for uncertainties in scenario data and model parameters. The dynamics of rivers flowing into the Chao Lake is not very well-known, except for the Fengle River. The Fengle catchment (1480 km2) is mainly rural. River discharges are recorded at Taoxi station, upstream its outlet into the lake. 20-year records of daily discharges are available. Nine rain gauges, with daily data, daily temperature and evapotranspiration data are also available. The current dynamics of the Fengle River is characterized in terms of flood frequencies on discharge-duration-frequency curves. The ATHYS freely available hydrological tool (www.athys-soft.org) is used to calibrate and validate a distributed model of the Fengle catchment. Four calibration runs are done on four independent 5-year discharge records. Four different sets of model parameters are discussed. The model is then run for validation. The uncertainties in model predictions are evaluated in terms of errors in the simulated discharges during the validation period, with regards to the 5-year period used for calibration. The model is then applied on scenarios of changes in land uses and climate. Uncertainties in scenarios of changes are estimated through literature review. The future dynamics of the Fengle River is characterized on discharge-duration-frequency curves. Results are discussed with regards to the uncertainties in model predictions and scenarios changes. The next step of this study will be to extrapolate the results observed at the scale of the Fengle river as benchmarks for all the rural catchments of the Chao Lake basin. Predictions of changes in the discharge dynamics will then be given at the Chao Lake basin scale.
The Stream-Catchment (StreamCat) and Lake-Catchment ...

EPA Pesticide Factsheets

Background/Question/MethodsLake and stream conditions respond to both natural and human-related landscape features. Characterizing these features within contributing areas (i.e., delineated watersheds) of streams and lakes could improve our understanding of how biological conditions vary spatially and improve the use, management, and restoration of these aquatic resources. However, the specialized geospatial techniques required to define and characterize stream and lake watersheds has limited their widespread use in both scientific and management efforts at large spatial scales. We developed the StreamCat and LakeCat Datasets to model, predict, and map the probable biological conditions of streams and lakes across the conterminous US (CONUS). Both StreamCat and LakeCat contain watershed-level characterizations of several hundred natural (e.g., soils, geology, climate, and land cover) and anthropogenic (e.g., urbanization, agriculture, mining, and forest management) landscape features for ca. 2.6 million stream segments and 376,000 lakes across the CONUS, respectively. These datasets can be paired with field samples to provide independent variables for modeling and other analyses. We paired 1,380 stream and 1,073 lake samples from the USEPAs National Aquatic Resource Surveys with StreamCat and LakeCat and used random forest (RF) to model and then map an invertebrate condition index and chlorophyll a concentration, respectively. Results/ConclusionsThe invertebrate
Hydrological Footprints of Urban Developments in the Lake Simcoe Watershed, Canada: A Combined Paired-Catchment and Change Detection Modeling Approach

NASA Astrophysics Data System (ADS)

Oni, S. K.; Futter, M. N.; Buttle, J. M.; Dillon, P.

2014-12-01

Urban sprawl and regional climate variability are major stresses on surface water resources in many places. The Lake Simcoe watershed (LSW) Ontario, Canada, is no exception. The LSW is predominantly agricultural but is experiencing rapid population growth due to its proximity to the greater Toronto area. This has led to extensive land use changes which have impacted its water resources and altered runoff patterns in some rivers draining to the lake. Here, we use a paired-catchment approach, hydrological change detection modelling and remote sensing analysis of satellite images to evaluate the impacts of land use change on the hydrology of the LSW (1994 to 2008). Results show that urbanization increased up to 16% in Lovers Creek, the most-urban impacted catchment. Annual runoff from Lovers Creek increased from 239 to 442 mm/yr in contrast to the reference catchment (Black River at Washago) where runoff was relatively stable with an annual mean of 474 mm/yr. Increased annual runoff from Lovers Creek was not accompanied by an increase in annual precipitation. Discriminant function analysis suggests that early (1992-1997; pre-major development) and late (2004-2009; fully urbanized) periods for Lovers Creek separated mainly based on model parameter sets related to runoff flashiness and evapotranspiration. As a result, parameterization in either period cannot be used interchangeably to produce credible runoff simulations in Lovers Creek due to greater scatter between the parameters in canonical space. Separation of early and late period parameter sets for the reference catchment was based on climate and snowmelt related processes. This suggests that regional climatic variability could be influencing hydrologic change in the reference catchment whereas urbanization amplified the regional natural hydrologic changes in urbanizing catchments of the LSW.
The changing Arctic carbon cycle: using the past to understand terrestrial-aquatic linkages

NASA Astrophysics Data System (ADS)

Anderson, N. J.; van Hardenbroek, M.; Jones, V.; McGowan, S.; Langdon, P. G.; Whiteford, E.; Turner, S.; Edwards, M. E.

2016-12-01

Predicted shifts in terrestrial vegetation cover associated with Arctic warming are altering the delivery and processing of carbon to aquatic ecosystems. This process could determine whether lakes are net carbon sources or sinks and, because lake density is high in many Arctic areas, may alter regional carbon budgets. Lake sediment records integrate information from within the lake and its catchment and can be used quantify past vegetation shifts associated with known climatic episodes of warmer (Holocene Thermal Maximum) and cooler (Neoglacial) conditions. We analysed sediment cores located in different Arctic vegetation biomes (tundra, shrub, forested) in Greenland, Norway and Alaska and used biochemical (algal pigments, stable isotopes) remains to evaluate whether past vegetation shifts were associated with changes in ecosystem carbon processing and biodiversity. When lake catchments were sparsely vegetated and soil vegetation was limited ultra-violet radiation (UVR) screening pigments indicate clear lake waters, scarce dissolved organic carbon/ matter (DOC/M). Moderate vegetation development (birch scrub in Norway; herb tundra in Greenland) appears to enhance delivery of DOM to lakes, and to stimulate algal production which is apparently linked to heterotrophic carbon processing pathways (e.g. algal mixotrophy, nutrient release via the microbial loop). Mature forest cover (in Alaska and Norway) supressed lake autotrophic production, most likely because coloured DOM delivered from catchment vegetation limited light availability. During wetter periods when mires developed lake carbon processing also changed, indicating that hydrological delivery of terrestrial DOM is also important. Therefore, future changes in Arctic vegetation and precipitation patterns are highly likely to alter the way that arctic ecosystems process carbon. Our approach provides an understanding of how ecosystem diversity and carbon processing respond to past climate change and the difficulty of identifying the drivers of state changes in the arctic.
Influence of the Little Ice Age on the biological structure of lakes in South West Greenland

NASA Astrophysics Data System (ADS)

McGowan, S.; Hogan, E. J.; Jones, V.; Anderson, N. J.; Simpson, G.

2013-12-01

Arctic lakes are considered to be particularly sensitive to environmental change, with biological remains in lake sediment records being interpreted as reflecting climate forcing. However the influence that differences in catchment properties and lake morphometries have on the sedimentary record is rarely considered. We investigated sediment cores from three lakes located close to the inland ice sheet margin in the Kangerlussuaq area of South West Greenland but within a few kilometres of one another. This regional replication allowed for direct comparisons of biological change in lakes exposed to identical environmental pressures (cooling, increased wind speeds) over the past c.2000 years. Sedimentary pigments were used as a proxy for whole-lake production and to investigate differences in phytoplankton community structure whilst fossil diatom assemblages were studied to determine differences in ecological responses during this time. We noted several major effects of the Little Ice Age cooling (LIA, c. 1400-1850AD). The organic content of sediments in all three lakes declined, and this effect was most pronounced in lakes closest to the inland ice sheet margin, which suggests that aeolian inputs derived from the glacial outwash plains (sandurs), and wind-scouring of the thin catchment soils by strong katabatic winds associated with the regional cooling might have both contributed to this sedimentary change. During the LIA total algal production (as indicated by chlorophyll and carotenoid pigments) was lower in all three lakes, most likely because of extended ice-cover and shorter growing seasons, and the ratio of planktonic: benthic diatom taxa increased, possibly because of lower light availability or fertilization from loess material. Despite this coherence in lake response to the LIA, diatom community composition changes in individual lakes differed, reflecting individual lake morphometry and catchment characteristics. These findings highlight the importance of regionally-replicated palaeo-studies when interpreting ecological impacts of long-term climate variability, and in assessing likely future response to climate change.
Water stable isotope shifts of surface waters as proxies to quantify evaporation, transpiration and carbon uptake on catchment scales

NASA Astrophysics Data System (ADS)

Barth, Johannes; van Geldern, Robert; Veizer, Jan; Karim, Ajaz; Freitag, Heiko; Fowlwer, Hayley

2017-04-01

Comparison of water stable isotopes of rivers to those of precipitation enables separation of evaporation from transpiration on the catchment scale. The method exploits isotope ratio changes that are caused exclusively by evaporation over longer time periods of at least one hydrological year. When interception is quantified by mapping plant types in catchments, the amount of water lost by transpiration can be determined. When in turn pairing transpiration with the water use efficiency (WUE i.e. water loss by transpiration per uptake of CO2) and subtracting heterotrophic soil respiration fluxes (Rh), catchment-wide carbon balances can be established. This method was applied to several regions including the Great Lakes and the Clyde River Catchments ...(Barth, et al., 2007, Karim, et al., 2008). In these studies evaporation loss was 24 % and 1.3 % and transpiration loss was 47 % and 22 % when compared to incoming precipitation for the Great Lakes and the Clyde Catchment, respectively. Applying WUE values for typical plant covers and using area-typical Rh values led to estimates of CO2 uptake of 251 g C m-2 a-1 for the Great Lakes Catchment and CO2 loss of 21 g C m2 a-1 for the Clyde Catchment. These discrepancies are most likely due to different vegetation covers. The method applies to scales of several thousand km2 and has good potential for improvement via calibration on smaller scales. This can for instance be achieved by separate treatment of sub-catchments with more detailed mapping of interception as a major unknown. These previous studies have shown that better uncertainty analyses are necessary in order to estimate errors in water and carbon balances. The stable isotope method is also a good basis for comparison to other landscape carbon balances for instance by eddy covariance techniques. This independent method and its up-scaling combined with the stable isotope and area-integrating methods can provide cross validation of large-scale carbon budgets. Together they can help to constrain relationships between carbon and water balances on the continental scale. References .Barth JAC, Freitag H, Fowler HJ, Smith A, Ingle C, Karim A (2007) Water fluxes and their control on the terrestrial carbon balance: Results from a stable isotope study on the Clyde Watershed (Scotland). Appl Geochem 22: 2684-2694 DOI 10.1016/j.apgeochem.2007.06.002 Karim A, Veizer J, Barth J.A.C. (2008) Net ecosystem production in the great lakes basin and its implications for the North American missing carbon sink: A hydrologic and stable isotope approach. Global and Planetary Change 61: 15-27 DOI 10.1016/j.gloplacha.2007.08.004

Factors affecting ground-water exchange and catchment size for Florida lakes in mantled karst terrain

USGS Publications Warehouse

Lee, Terrie Mackin

2002-01-01

In the mantled karst terrain of Florida, the size of the catchment delivering ground-water inflow to lakes is often considerably smaller than the topographically defined drainage basin. The size is determined by a balance of factors that act individually to enhance or diminish the hydraulic connection between the lake and the adjacent surficial aquifer, as well as the hydraulic connection between the surficial aquifer and the deeper limestone aquifer. Factors affecting ground-water exchange and the size of the ground-water catchment for lakes in mantled karst terrain were examined by: (1) reviewing the physical and hydrogeological characteristics of 14 Florida lake basins with available ground-water inflow estimates, and (2) simulating ground-water flow in hypothetical lake basins. Variably-saturated flow modeling was used to simulate a range of physical and hydrogeologic factors observed at the 14 lake basins. These factors included: recharge rate to the surficial aquifer, thickness of the unsaturated zone, size of the topographically defined basin, depth of the lake, thickness of the surficial aquifer, hydraulic conductivity of the geologic units, the location and size of karst subsidence features beneath and onshore of the lake, and the head in the Upper Floridan aquifer. Catchment size and the magnitude of ground-water inflow increased with increases in recharge rate to the surficial aquifer, the size of the topographically defined basin, hydraulic conductivity in the surficial aquifer, the degree of confinement of the deeper Upper Floridan aquifer, and the head in the Upper Floridan aquifer. The catchment size and magnitude of ground-water inflow increased with decreases in the number and size of karst subsidence features in the basin, and the thickness of the unsaturated zone near the lake. Model results, although qualitative, provided insights into: (1) the types of lake basins in mantled karst terrain that have the potential to generate small and large amounts of ground-water inflow, and (2) the location of ground-water catchments that could be managed to safeguard lake water quality. Knowledge of how ground-water catchments are related to lakes could be used by water-resource managers to recommend setback distances for septic tank drain fields, agricultural land uses, and other land-use practices that contribute nutrients and major ions to lakes.
Integrated assessment of land use and cover changes in the Malagarasi river catchment in Tanzania

NASA Astrophysics Data System (ADS)

Kashaigili, J. J.; Majaliwa, A. M.

Malagarasi river catchment represents one of the largest and most significant transboundary natural ecosystems in Africa. The catchment constitutes about one third of the catchment area of Lake Tanganyika and contains ecosystems of both national and international importance (i.e. Muyovozi Wetland Ramsar site). It has been increasingly said that increased anthropogenic activities have had negative impacts on the Muyovozi wetland in particular and other catchment resources. Nevertheless, these beliefs are little supported by quantitative data. A study on the dynamics of land use and cover in the Malagarasi river catchment therefore investigated long-term and seasonal changes that have occurred as a result of human activities in the area for the periods between 1984 and 2001. Landsat TM and ETM+ images were used to locate and quantify the changes. Perceptions of local people on historical changes and drivers for the changes were also collected and integrated in the assessment. The study revealed a significant change in land use and cover within a period of 18 year. Between 1984 and 2001, the woodland and wetland vegetation covers declined by 0.09% and 2.51% per year. Areas with settlements and cultivation increased by 1.05% annually while bushed grassland increased at 1.93% annually. The perceived principal drivers for the changes were found to include fire, cultivation along rivers and lake shores, overgrazing, poor law enforcement, insufficient knowledge on environmental issues, increasing poverty, deforestation and population growth. The human population growth rate stands at 4.8% against a national figure of 2.9%. The most perceived environmental problems include drying of streams and rivers, change in rainfall, loss of soil fertility, soil erosion and reduced crop yield. The study concludes that, there has been significant changes in land use and cover in the catchment and these require concerted actions to reverse the changes. The study highlights the importance of integrating remote sensing and local knowledge in understanding the dynamics catchment resources and generating information that could be used to overcome the catchment management problems.
Remote sensing appraisal of Lake Chad shrinkage connotes severe impacts on green economics and socio-economics of the catchment area.

PubMed

Onamuti, Olapeju Y; Okogbue, Emmanuel C; Orimoloye, Israel R

2017-11-01

Lake Chad commonly serves as a major hub of fertile economic activities for the border communities and contributes immensely to the national growth of all the countries that form its boundaries. However, incessant and multi-decadal drying via climate change pose greater threats to this transnational water resource, and adverse effects on ecological sustainability and socio-economic status of the catchment area. Therefore, this study assessed the extent of shrinkage of Lake Chad using remote sensing. Landsat imageries of the lake and its surroundings between 1987 and 2005 were retrieved from Global Land Cover Facility website and analysed using Integrated Land and Water Information System version 3.3 (ILWIS 3.3). Supervised classification of area around the lake was performed into various land use/land cover classes, and the shrunk part of its environs was assessed based on the land cover changes. The shrinkage trend within the study period was also analysed. The lake water size reduced from 1339.018 to 130.686 km 2 (4.08-3.39%) in 1987-2005. The supervised classification of the Landsat imageries revealed an increase in portion of the lake covered by bare ground and sandy soil within the reference years (13 490.8-17 503.10 km 2 ) with 4.98% total range of increase. The lake portion intersected with vegetated ground and soil also reduced within the period (11 046.44-10 078.82 km 2 ) with 5.40% (967.62 km 2 ) total decrease. The shrunk part of the lake covered singly with vegetation increased by 2.74% from 1987 to 2005. The shrunk part of the lake reduced to sand and turbid water showed 5.62% total decrease from 1987 to 2005 and a total decrease of 1805.942 km 2 in area. The study disclosed an appalling rate of shrinkage and damaging influences on the hydrologic potential, eco-sustainability and socio-economics of the drainage area as revealed using ILWIS 3.3.
The impact of lake and reservoir parameterization on global streamflow simulation.

PubMed

Zajac, Zuzanna; Revilla-Romero, Beatriz; Salamon, Peter; Burek, Peter; Hirpa, Feyera A; Beck, Hylke

2017-05-01

Lakes and reservoirs affect the timing and magnitude of streamflow, and are therefore essential hydrological model components, especially in the context of global flood forecasting. However, the parameterization of lake and reservoir routines on a global scale is subject to considerable uncertainty due to lack of information on lake hydrographic characteristics and reservoir operating rules. In this study we estimated the effect of lakes and reservoirs on global daily streamflow simulations of a spatially-distributed LISFLOOD hydrological model. We applied state-of-the-art global sensitivity and uncertainty analyses for selected catchments to examine the effect of uncertain lake and reservoir parameterization on model performance. Streamflow observations from 390 catchments around the globe and multiple performance measures were used to assess model performance. Results indicate a considerable geographical variability in the lake and reservoir effects on the streamflow simulation. Nash-Sutcliffe Efficiency (NSE) and Kling-Gupta Efficiency (KGE) metrics improved for 65% and 38% of catchments respectively, with median skill score values of 0.16 and 0.2 while scores deteriorated for 28% and 52% of the catchments, with median values -0.09 and -0.16, respectively. The effect of reservoirs on extreme high flows was substantial and widespread in the global domain, while the effect of lakes was spatially limited to a few catchments. As indicated by global sensitivity analysis, parameter uncertainty substantially affected uncertainty of model performance. Reservoir parameters often contributed to this uncertainty, although the effect varied widely among catchments. The effect of reservoir parameters on model performance diminished with distance downstream of reservoirs in favor of other parameters, notably groundwater-related parameters and channel Manning's roughness coefficient. This study underscores the importance of accounting for lakes and, especially, reservoirs and using appropriate parameterization in large-scale hydrological simulations.
Long-Term Water Quality Studies in a Eutrophic Lake Catchment: Slapton Ley, SW England

NASA Astrophysics Data System (ADS)

Burt, T. P.; Worrall, F.; Howden, N. J. K.

2014-12-01

Monitoring is the process by which we keep the behaviour of the environment in view, an essential way of discovering whether there are significant undesirable changes taking place. Long-term datasets reveal important patterns for scientists to explain and are essential for testing hypotheses undreamt of at the time monitoring scheme was set up. Many environmental processes take place over relatively long periods of time; very often, subtle processes are embedded within highly variable systems so that their weak signal cannot be extracted without a long record. Slapton Ley is a freshwater coastal lagoon in SW England. The Ley is part of a National Nature Reserve, wetland 116 ha in area which is divided into two basins: the Higher Ley (39 ha) is mainly reed swamp; the Lower Ley (77 ha) is open water. In the 1960s it became apparent that the Ley was becoming increasingly eutrophic. In order to gauge water, sediment and nutrient inputs into the lake, measurements began on the main catchments in late 1969. Continuous monitoring of discharge and a weekly water-sampling programme have been maintained by the Slapton Ley Field Centre ever since. The monitoring programme has been supplemented by a number of research projects which have sought to identify the salient hydrological processes operating within the Slapton catchments and to relate these to the delivery of sediment and solute to the stream system. The nitrate issue has been of particular interest at Slapton; although many longer series exist for large rivers like the Thames, the long record of nitrate data for the Slapton catchments is unique in Britain for small rural basins. Other issues to be explored will be the phosphorus legacy in lake sediments and a long-term decline in lake pH. The Slapton water quality record has confirmed that undesirable changes are taking place, revealed evidence of important patterns to be explained, allowed testing of new hypotheses (e.g. links with land-use change) and helped provide strategies for more successful management of the catchment area.
An assessment of mean annual precipitation in Rajasthan, India needed to maintain Mid-Holocene lakes

NASA Astrophysics Data System (ADS)

Gill, E.; Rajagopalan, B.; Molnar, P. H.

2013-12-01

Paleo-climate literature reports evidence of freshwater lakes over Rajasthan, a region of northwestern India, during the mid-Holocene (~6ka), where desert conditions prevail in present time. It's suggested that mid-Holocene temperatures were warmer, precipitation was nearly double current levels, and there was an enhanced La Niña-like state. While previous analyses infer the lakes were sustained by generally high precipitation and low evaporation, we provide a systematic analysis on the relevant energy budget quantities and the dynamic relationships between them. We have built a hydrological lake model to reconstruct lake levels throughout the Holocene. Model output is evaporation from the lake. Inputs are precipitation over the lake and catchment runoff, determined using precipitation, Preistley-Taylor evapotranspiration, interception and infiltration. Initial tests of the model have been completed with current climate conditions to ensure accurate behavior. Contemporary runs used station precipitation and temperature data [Rajeevan et al., 2006] for the region surrounding Lake Didwana (27°N 74°E). Digital elevation maps were used to compile lake bathymetry for Lake Didwana. Under current climate conditions, a full Lake Didwana (~ 9 m) empties over the first several years. While lake depth varies yearly, increasing with each monsoon season, variations following the initial decline are minimal (~ × 1.0 m). We ran the model with a 2000-year sequence of precipitation and temperature generated by resampling the observed weather sequences, with a suite of base line fractions of vegetation cover and increased precipitation, with solar insolation appropriate during the mid-Holocene period. Initial runs revealed that precipitation amount and percent of vegetated catchment area influence lake levels, but insolation alone does not. Incrementally changing precipitation (between current levels and a 75% increase) and percent of vegetated area (between 10-90%) reveals that a 50% increase in precipitation alone is not enough to reach the maximum lake levels reported by Enzel et al. [1999] of 7m during the mid-Hoocene. For Lake Didwana to reach maximum levels, both at least 50% more precipitation than today and a vegetated fraction of the catchment of at least 50% is required, but if precipitation were twice that today, and vegetation covered 50% of the area, the lake would have been deeper than 9 m. Future work involves generating precipitation and temperature series for 2000-year long sequences representing the early-, mid-, and late-Holocene using two approaches: k-nearest neighbor and generalized linear model. Using these, we'll run the lake model to determine what combinations of precipitation, evaporation, and other variables are necessary to sustain the lakes. While model runs suggest that monsoon rainfall should increase in a warming world, observations show we are currently in the longest epoch of below-normal south-Asian monsoonal rainfall. By using the mid-Holocene as an analog for a future warming world, this study could expand the understanding of the south-Asian monsoon's potential response to warming.
Foreseen hydrological changes drive efforts to formulate water balance improvement measures as part of the management options of adaptation at Lake Balaton, Hungary

NASA Astrophysics Data System (ADS)

Molnar, Gabor; Kutics, Karoly

2013-04-01

Located in Western Hungary, Lake Balaton (LB) is one of the shallowest large lakes of the world. The catchment area including the lake is 5775 km2, only 10 times more than the lake surface area of 593 km2. This relatively small catchment area and the relatively dry climate results in high vulnerability of the lake water budget to any hydro-meteorological changes. Due to the combined effects of planned water quality protection measures (refer to adjoining article on LB water quality) water quality was not as serious a concern over the last 15 years. However, a new and potentially more damaging threat, decreasing water level started to emerge in 2000. The natural water budget was negative half of the time, i.e. 6 years in the last 12 years. It hadn't occurred in the previous 80 years, since 1921, the year from which detailed meteorological data on the area are available. This new phenomenon raised and continues to raise serious sustainability concerns in the Lake Balaton area requiring better understanding of climatic changes and their foreseen impacts on hydrological and ecological processes that would lead decision makers to formulate the appropriate vulnerability and adaptation policies. Based on the common methodologies of the EULAKES project, present state of the hydrological conditions was analyzed as well as qualitative vulnerability assessment carried out to the area. Using the climate scenarios developed by the project partner Austrian Institute of Technology, calculations on water budget changes was possible. It is estimated that by the middle of the 21st century the lake will experience a drastic drop in the inflow and, accompanied by the increased evaporation, it is likely that years without outflow and serious drops in water-level would occur. The increased frequency of unfavorable water deficit will cause not only ecological, but also socio-economic conflicts in the multipurpose usage of the lake. Therefore, a qualitative vulnerability assessment was completed with a similar methodology applied in partner lakes of the EULAKES project. Based on the assessment through a participatory process involving a broad group of stakeholders the possible management options were gathered and tested as the alternatives to improve the water balance of the lake.
Modelling cascading and erosional processes for glacial lake outburst floods in the Quillcay catchment, Huaraz, Cordillera Blanca, Peru

NASA Astrophysics Data System (ADS)

Baer, Patrick; Huggel, Christian; Frey, Holger; Chisolm, Rachel; McKinney, Daene; McArdell, Brian; Portocarrero, Cesar; Cochachin, Alejo

2016-04-01

Huaraz as the largest city in Cordillera Blanca has faced a major disaster in 1941, when an outburst flood from Lake Palcacocha killed several thousand people and caused widespread destruction. Recent studies on glacial lake outburst flood (GLOF) modelling and early warning systems focussed on Lake Palcacocha which has regrown after the 1941 event, from a volume of half a million m3 in 1974 to a total volume of more than 17 million m3 today. However, little research has been conducted so far concerning the situation of other lakes in the Quillcay catchment, namely Lake Tullparaju (12 mill. m3) and Cuchillacocha (2.5 mill. m3), which both also pose a threat to the city of Huaraz. In this study, we modelled the cascading processes at Lake Tullparaju and Lake Cuchillacocha including rock/ice avalanches, flood wave propagation in the lake and the resulting outburst flood and debris flows. We used the 2D model RAMMS to simulate ice avalanches. Model output was used as input for analytical 2D and 3D calculations of impact waves in the lakes that allowed us to estimate dam overtopping wave height. Since the dimension of the hanging glaciers above all three lakes is comparable, the scenarios in this study have been defined similar to the previous study at Lake Palcacocha. The flow propagation model included sediment entrainment in the steeper parts of the catchment, adding up to 50% to the initial flow volume. The results for total travel time as well as for inundated areas and flow depth and velocity in the city of Huaraz are comparable to the previous studies at Lake Palcacocha. This underlines the importance of considering also these lakes within an integral hazard analysis for the city of Huaraz. A main challenge for modelling GLOFs in the Quillcay catchment using RAMMS is the long runout distance of over 22 km combined with the very low slope gradient of the river. Further studies could improve the process understanding and could focus on more detailed investigations of the stability of the steep glaciers and rock faces, or on incorporation of bathymetric and geotechnical dam information with the application of 3D wave generation simulation. First applications of the beta version of the RAMMS erosion model for GLOF sediment entrainment are promising and could be refined with additional field studies.
Application of the MAGIC model to the Glacier Lakes catchments

Treesearch

John O. Reuss

1994-01-01

The MAGIC model (Cosby et al. 1985, 1986) was calibrated for East and West Glacier Lakes, two adjacent high-altitude (3200 m- 3700 m) catchments in the Medicine Bow National Forest of southern Wyoming. This model uses catchment characteristics including weathering rates, soil chemical characteristics, hydrological parameters, and precipitation amounts and composition...
Relationship between catchment events (earthquake and heavy rain) and sediment core analysis result in Taiwan.

NASA Astrophysics Data System (ADS)

Chen, Hsin-Ying; Lin, Jiun-Chuan

2015-04-01

Lake sediments contains material from the catchment. In those sediments, there are some features which can indicate characteristic or status of the catchment. These features were formed by different mechanisms, including some events like earthquakes or heavy rain, which are very common in Taiwan. By analyzing and discussing features of sediments there is a chance to identify historical events and rebuild catchment history. In this study, we compare features of sediment core ( including density, mineral grain size, whole grain size, and biogenic silica content) and earthquake, precipitation records. Sediment cores are collected from Emerald peak lake (24.514980, 121.605844; 77.5, 77.2, 64cm depth), Liyutan lake (23.959878, 120.996585; 43.2, 78.1 cm depth), Sun Moon Lake (23.847043, 120.909869; 181 cm depth), and Dongyuan lake (22.205742, 120.854984; 45.1, 44.2cm depth) in 2014. We assume that there are regular material and organic output in catchments. And rain will provide impetus to move material into lakes. The greater the rain is the larger the material can move. So, if there is a heavy rainfall event, grain size of lake sediment may increase. However, when earthquakes happen, it will produce more material which have lower organic composition than ordinary. So we suggest that after earthquakes there will be more material stored in catchment than often. And rainfall event provides power to move material into lakes, cause more sediment and mineral content higher than usual. Comparing with earthquake record(from 1949, by USGS) and precipitation record(from1940, by Central Weather Bureau,Taiwan), there were few earthquakes which happened near lakes and scale were more than 7 ML. There were 28 rainfall events near Emerald peak lake; 32 near Liyutan lake and Sun Moon Lake; 58 near Dongyuan lake ( rainfall event: >250 mm/day ). In sediment analytical results, ratio of whole and mineral grain size indeed have similar trends with earthquake record. However, rainfall events were too frequent to determine the relation between rainfall events and sediment analyze results, that may be obstruction of attempt to speculate the extent of earthquake events.
Seasonality of Branched GDGT in Freshwater Settings: a Challenge to the In Situ Production Paradigm?

NASA Astrophysics Data System (ADS)

Rosell-Melé, A.; Cao, M.; Rueda, G.; Henriksen, M.

2017-12-01

The branched GDGTs (brGDGTs) in sediments are used to estimate past mean annual air temperatures (MAT). In lakes, the brGDGT proxy is often applied in high resolution sedimentary sequences to reconstruct MAT at subdecadal time scales. A number of studies argue that their production in the water column override inputs from soil sources into a lake sediments. In addition, brGDGTs proxy estimates are also purported to be seasonally biased. Moreover, the initial definitions of the brGDGTs proxies are questioned as a proxy for MAT on analytical and environmental grounds. To test the some of the current paradigms, we examined the sesonal cycle of brGDGT production and transport in three different sites in Europe. The locations considered had a marked seasonal temperature cycle, which was expected to maximize the possibility of detecting a seasonal bias in the proxies. We analyzed monthly brGDGTs in the soils catchments, and in parallel in the suspended particles in the catchment run off and rivers, and settling particulate matter in a lake. In two of the sites we also analyzed the intact and the core lipds. Two of the areas studied are located in the same latitude but at different altitudes in the Pyrenees, and another area is in Norway. Despite the diversity of environments, the results are very coherent. As expected, the brGDGT distributions in soils show no seasonality. However, the same lack of seasonality is also clear in the suspended particulate matter in the catchment run off and in the rivers studied, and in the settling particulate matter in the lake traps. Our study places into question the current general validity of the paradigm of in situ production of brGDGts in freshwater environments. In fact, the sedimentary brGDGT signature is representative of average environmental conditions in the catchment at least over decades. On shorter timescales (i.e. annual), the sediment variability likely reflects changes in sediment sources rather than climate.
Sensitivity of the East African rift lakes to climate variability

NASA Astrophysics Data System (ADS)

Olaka, L.; Trauth, M. H.

2009-04-01

Lakes in the East African Rift have provided excellent proxies to reconstruct past climate changes in the low latitudes. The lakes occupy volcano-tectonic depressions with highly variable climate and hydrological setting, that present a good opportunity to study the climatic and hydrogeological influences on the lake water budget. Previous studies have used lake floor sediments to establish the sensitivity of the East African rift lakes. This study focuses on geomorphology and climate to offer additional or alternative record of lake history that are key to quantifying sensitivity of these lakes as archives to external and internal climatic forcings. By using the published Holocene lake areas and levels, we analyze twelve lakes on the eastern arm of the East African rift; Ziway, Awassa, Turkana, Suguta, Baringo, Nakuru, Elmenteita, Naivasha, Natron, Manyara and compare with Lake Victoria, that occupies the plateau between the east and the western arms of the rift. Using the SRTM data, Hypsometric (area-altitude) analysis has been used to compare the lake basins between latitude 80 North and 30 South. The mean elevation for the lakes, is between 524 and 2262 meters above sea level, the lakes' hypsometric integrals (HI), a measure of landmass volume above the reference plane, vary from 0.31 to 0.76. The aridity index (Ai), defined as Precipitation/ Evapotranspiration, quantifies the water available to a lake, it encompasses land cover and climatic effects. It is lowest (arid) in the basin between the Ethiopian rift and the Kenyan rift and at the southern termination of the Kenyan Rift in the catchments of lake Turkana, Suguta, Baringo and Manyara with values of 0.55, 0.43, 0.43 and 0.5 respectively. And it is highest (wet) in the catchments of, Ziway, Awassa, Nakuru and Naivasha as 1.33,1.03 and 1.2 respectively, which occupy the highest points of the rift. Lake Victoria has an index of 1.42 the highest of these lakes and receives a high precipitation. We use a simple model written on a Matlab code to illustrate the lake volume and area response to climate of surficialy closed, graben shaped and panshaped lake basins. From preliminary results, lake basins that are sensitive to climate variability have a high HI and high aridity index, which will be presented in this conference
Does historical wildfire activity alter metal fluxes to northern lakes?

NASA Astrophysics Data System (ADS)

Pelletier, N.; Chetelat, J.; Vermaire, J. C.; Palmer, M.; Black, J.; Pellisey, J.; Tracz, B.; van der Wielen, S.

2017-12-01

Current drought conditions in northwestern Canada are conducive to more frequent and severe wildfires that may mobilize mercury and other metals accumulated in soil and biomass. There is evidence that wildfires can remobilize and transport mercury within and outside catchments by atmospheric volatilization, particulate emissions and catchment soil erosion. However, the effect of fires on mercury fluxes to nearby lake sediments remains unclear. In this study, we use a combination of 10 dated lake sediment cores and four nearby ombrotrophic peatland cores to investigate the effects of wildfires on mercury fluxes to lake sediments. Lakes varying in catchment size and distance from recent fire events were sampled. Mercury concentrations in the environmental archives were measured, and macroscopic charcoal particles (>100 um) were counted at high resolution in the sediments to observe the co-variation of the local fire history and mercury fluxes. Mercury flux recorded in ombrotrophic peat cores provided an estimate of the historical atmospheric mercury flux from local and regional atmospheric deposition. The mercury flux recorded in lake sediments corresponds to the sum of direct atmospheric deposition and catchment transport. In combination, these archives will allow for the partitioning of mercury loading attributable to catchment transport from direct atmospheric deposition. After correcting the fluxes for particle focusing and terragenic elements input, flux from different lakes will be compared based on their catchment size and their temporal and spatial proximity known fire events. Altogether, our preliminary results using these paleolimnological methods will provide new insights on mercury transport processes that are predicted to become more important under a changing climate.
Source identification and mass balance studies of mercury in Lake An-dong, S. Korea

NASA Astrophysics Data System (ADS)

Han, J.; Byeon, M.; Yoon, J.; Park, J.; Lee, M.; Huh, I.; Na, E.; Chung, D.; Shin, S.; Kim, Y.

2009-12-01

In this study, mercury and methylmercury were measured in atmospheric, tributary, open-lake water column, sediment, planktons and fish samples in the catchments area of Lake An-dong, S. Korea. Lake An-dong, an artificial freshwater lake is located on the upstream of River Nak-dong. It has 51.5 km2 of open surface water and 1.33 year of hydraulic residence time. It is a source of drinking water for 0.3 million S. Koreans. Recently, the possibilities of its mercury contamination became an issue since current studies showed that the lake had much higher mercury level in sediment and certain freshwater fish species than any other lakes in S. Korea. This catchments area has the possibilities of historical mercury pollution by the location of more than 50 abandoned gold mines and Young-poong zinc smelter. The objective of this study was to develop a mercury mass balance and identify possible mercury sources in the lake. The results of this study are thus expected to offer valuable insights for the sources of mercury loading through the watershed. In order to estimate the mercury flux, TGM, RGM and particulate mercury were measured using TEKRAN 2537 at the five sites surrounding Lake An-dong from May, 2009 with wet and dry deposition. The fate and transport of mercury in water body were predicted by using EFDC (Environmental Dynamic Fluid Code) and Mercury module in WASP7 (Water quality analysis program) after subsequent distribution into water body, sediments, followed by bioaccumulation and ultimate uptake by humans. The mercury mass balance in Young-poong zinc smelter was also pre-estimated by measuring mercury content in zinc ores, emission gases, sludge, wastewater and products.
Importance of diffuse pollution control in the Patzcuaro Lake Basin in Mexico.

PubMed

Carro, Marco Mijangos; Dávila, Jorge Izurieta; Balandra, Antonieta Gómez; López, Rubén Hernández; Delgadillo, Rubén Huerto; Chávez, Javier Sánchez; Inclán, Luís Bravo

2008-01-01

In the catchment area of the Lake Patzcuaro in Central Mexico (933 km2) the apportionments of erosion, sediment, nutrients and pathogen coming from thirteen micro basins were estimated with the purpose of identifying critical areas in which best management practices need to be implemented in order to reduce their contribution to the lake pollution and eutrophication. The ArcView Generalized Watershed Loading Functions model (AV-GWLF) was applied to estimate the loads and sources of nutrients. The main results show that the total annual contribution of nitrogen from point sources were 491 tons and from diffuse pollution 2,065 tons, whereas phosphorus loads where 116 and 236 tons, respectively during a thirty year simulation period. Micro basins with predominant agricultural and animal farm land use (56% of the total area) accounts for a high percentage of nitrogen load 33% and phosphorus 52%. On the other hand, Patzcuaro and Quiroga micro basins which comprise approximately 10% of the total catchment area and are the most populated and visited towns by tourist 686,000 people every year, both contributes with 10.1% of the total nitrogen load and 3.2% of phosphorus. In terms of point sources of nitrogen and phosphorus the last towns contribute with 23.5% and 26.6% respectively. Under this situation the adoption of best management practices are an imperative task since the sedimentation and pollution in the lake has increased dramatically in the last twenty years. Copyright (c) IWA Publishing 2008.
Morphology and morphometry of upland lakes over lateritic crust, Serra dos Carajás, southeastern Amazon region.

PubMed

Silva, Marcio S DA; Guimarães, José T F; Souza Filho, Pedro W M; Nascimento Júnior, Wilson; Sahoo, Prafulla K; Costa, Francisco R DA; Silva Júnior, Renato O; Rodrigues, Tarcísio M; Costa, Marlene F DA

2018-01-01

High-resolution satellite images, digital elevation models, bathymetric and sedimentological surveys coupled with statistical analysis were used to understand the physical environment and discuss their influence on water quality of the five upland lakes of Serra Sul dos Carajás, southeast Amazonia. The lakes have mid-altitude ranges (elevation), very small (catchment) and shallow to very shallow (central basins). Based on the length, area and volume, Violão and TI (Três Irmãs)-3 lakes may present large vertical movements of the water due to wind action and weakly stratified waters. Trophic conditions based on depth and shore development (Ld) parameters must be used with caution, since Amendoim Lake is relatively deep, but it is oligotrophic to ultra-oligotrophic. Ld values suggest that the lakes are circular to subcircular and are likely formed by solution process, as also suggested by volume development. TI-2 Lake is only presenting convex central basin and has highest dynamic ratio (DR), thus it may have high sedimentation and erosion rates. Based on the relationship between studied parameters, morphometric index and DR likely influence temperature and dissolved oxygen of waters of TI-2 Lake due to its depth profile and wind-induced surface mixing. Nevertheless, water quality parameters are controlled by catchment characteristics of the lakes.
Memory of the Lake Rotorua catchment - time lag of the water in the catchment and delayed arrival of contaminants from past land use activities

NASA Astrophysics Data System (ADS)

Morgenstern, Uwe; Daughney, Christopher J.; Stewart, Michael K.; McDonnell, Jeffrey J.

2013-04-01

The transit time distribution of streamflow is a fundamental descriptor of the flowpaths of water through a catchment and the storage of water within it, controlling its response to landuse change, pollution, ecological degradation, and climate change. Significant time lags (catchment memory) in the responses of streams to these stressors and their amelioration or restoration have been observed. Lag time can be quantified via water transit time of the catchment discharge. Mean transit times can be in the order of years and decades (Stewart et al 2012, Morgenstern et al., 2010). If the water passes through large groundwater reservoirs, it is difficult to quantify and predict the lag time. A pulse shaped tracer that moves with the water can allow quantification of the mean transit time. Environmental tritium is the ideal tracer of the water cycle. Tritium is part of the water molecule, is not affected by chemical reactions in the aquifer, and the bomb tritium from the atmospheric nuclear weapons testing represents a pulse shaped tracer input that allows for very accurate measurement of the age distribution parameters of the water in the catchment discharge. Tritium time series data from all catchment discharges (streams and springs) into Lake Rotorua, New Zealand, allow for accurate determination of the age distribution parameters. The Lake Rotorua catchment tritium data from streams and springs are unique, with high-quality tritium data available over more than four decades, encompassing the time when the bomb-tritium moved through the groundwater system, and from a very high number of streams and springs. Together with the well-defined tritium input into the Rotorua catchment, this data set allows for the best understanding of the water dynamics through a large scale catchment, including validation of complicated water mixing models. Mean transit times of the main streams into the lake range between 27 and 170 years. With such old water discharging into the lake, most of the water inflows into the lake are not yet fully representing the nitrate loading in their sub-catchments from current land use practises. These water inflows are still 'diluted' by pristine old water, but over time, the full amount of nitrate load will arrive at the lake. With the age distribution parameters, it is possible to predict the increase in nitrate load to the lake via the groundwater discharges. All sub-catchments have different mean transit times. The mean transit times are not necessarily correlated with observable hydrogeologic properties like hydraulic conductivity and catchment size. Without such age tracer data, it is therefore difficult to predict mean transit times (lag times, memory) of water transfer through catchments. References: Stewart, M.K., Morgenstern, U., McDonnell, J.J., Pfister, L. (2012). The 'hidden streamflow' challenge in catchment hydrology: A call to action for streamwater transit time analysis. Hydrol. Process. 26,2061-2066, Invited commentary. DOI: 10.1002/hyp.9262 Morgenstern, U., Stewart, M.K., and Stenger, R. (2010) Dating of streamwater using tritium in a post nuclear bomb pulse world: continuous variation of mean transit time with streamflow, Hydrol. Earth Syst. Sci, 14, 2289-2301
Extent and drainage status of organic soils in the Lake Victoria catchment

NASA Astrophysics Data System (ADS)

Barthelmes, Reni; Barthelmes, Alexandra; Joosten, Hans

2016-04-01

When considering peatlands and organic soils in the tropics, the huge areas in SE Asia prevail in public and scientific perception, whereas Africa has largely been out of focus. However, East Africa contains large areas of organic soils as well. They basically occur in the high altitudes of the uplifted flanks of the East African Rift System, isolated volcanoes and the Ethiopian highlands, in the Zambezian floodplains (e.g. Zambia), and in coastal environments (e.g. Mozambique and Madagascar). We used a mapping approach that integrates old field data and maps, specialized landscape and peatland-related knowledge, and modern RS and GIS techniques to elaborate a comprehensive and rather reliable overview of organic soils (incl. peatlands) in the Lake Victoria catchment. Maps at a scale of 1:25,000 have been prepared for Burundi, Kenya, Rwanda, Tanzania and Uganda. The land use intensity has been estimated for all organic soil areas based on satellite and aerial imagery. Feeding the Nile River, sustaining a fast growing and widely poor population and already facing climatic changes, organic soils of the Lake Victoria neighbouring countries are partially under heavy threat. We mapped 10,645 km2 of organic soils for the entire area of which 8,860 km2 (83.2%) seem to be in near natural condition. We assume slightly drainage and low degradation for 564 km2 (5.3%) and intensive drainage and heavy degradation for 1,222 km2 (11.5%). Degradation hotspot is Burundi with 522 km2 (79.5%) of heavily drained and degrading organic soils. This area assessment has been quite conservative to not overestimate the extent of organic soils. A reserve of 5-7,000 km2 of wetlands in the Lake Victoria catchment may include peatlands too, which needs to be confirmed in field surveys. Considering the key role of peatlands and organic soils for water provision and regulation and their rapid degradation due to drainage and inappropriate use, this inventory might be a step towards organic soil protection, and the development (or rediscovery) of sustainable land use options for undrained or future rewetted areas.
Impacts of Recent Wetting on Snow Processes and Runoff Generation in a Terminal Lake Basin, Devils Lake, North Dakota.

NASA Astrophysics Data System (ADS)

Mahmood, T. H.; Van Hoy, D.

2016-12-01

The Devils Lake Basin, only terminal lake basin in North America, drains to a terminal lake called Devils Lake. Terminal lakes are susceptible to climate and land use changes as their water levels fluctuate to these changes. The streamflow from the headwater catchments of the Devils Lake basin exerts a strong control on the water level of the lake. Since, the mid-1980s, the Devils Lake Basin as well as other basins in the northern Great Plains have faced a large and abrupt surge in precipitation regime resulting in a series of wetter climatic condition and flooding around the Devils Lake area. Nevertheless, the impacts of the recent wetting on snow processes such as snow accumulations, blowing snow transport, in-transit sublimation, frozen soil infiltration and snowmelt runoff generations in a headwater catchment of the Devils Lake basin are poorly understood. In this study, I utilize a physically-based, distributed cold regions hydrological model to simulate the hydrological responses in the Mauvais Coulee basin that drains to Devils Lake. The Mauvais Coulee basin ( 1072 km2), located in the north-central North Dakota, is set in a gently rolling landscape with low relief ( 220 m) and an average elevation of 500 m. Major land covers are forest areas in turtle mountains ( 10%) and crops ( 86%), with wheat ( 25%) and canola ( 20%) as the major crops. The model set up includes ten sub-basins, each of which is divided into several hydrological response units (HRUs): riparian forest, river channel, reservoir, wheat, canola, other crops, and marsh. The model is parameterized using local and regional measurements and the findings from previous scientific studies. The model is evaluated against streamflow observations at the Mauvais Coulee gauge (USGS) during 1994-2013 periods using multiple performance criteria. Finally, the impacts of recent increases in precipitation on hydrologic responses are investigated using modeled hydrologic processes.
Spatial trends and pollution assessment for mercury in the surface soils of the Nansi Lake catchment, China.

PubMed

Ren, Ming-Yi; Yang, Li-Yuan; Wang, Long-Feng; Han, Xue-Mei; Dai, Jie-Rui; Pang, Xu-Gui

2018-01-01

Surface soil samples collected from Nansi Lake catchment were analyzed for mercury (Hg) to determine its spatial trends and environmental impacts. Results showed that the average soil Hg contents were 0.043 mg kg -1 . A positive correlation was shown between TOC and soil Hg contents. The main type of soil with higher TOC contents and lower pH values showed higher soil Hg contents. Soil TOC contents and CV values were both higher in the eastern catchment. The eastern part of the catchment, where the industry is developed, had relatively high soil Hg contents and a banding distribution of high Hg contents was corresponded with the southwest-northeast economic belt. Urban soils had higher Hg contents than rural soils. The urbanization pattern that soil Hg contents presented a decreasing trend from city center to suburb was shown clearly especially in the three cities. Soil Hg contents in Jining City showed a good consistency with the urban land expansion. The spatial trends of soil Hg contents in the catchment indicated that the type and the intensity of human activities have a strong influence on the distribution of Hg in soils. Calculated risk indices showed that the western part of the catchment presented moderately polluted condition and the eastern part of the catchment showed moderate to strong pollution level. The area with high ecological risk appeared mainly along the economic belt.

36 year trends in dissolved organic carbon export from Finnish rivers to the Baltic Sea.

PubMed

Räike, Antti; Kortelainen, Pirkko; Mattsson, Tuija; Thomas, David N

2012-10-01

Increasing dissolved organic carbon (DOC) concentrations in lakes, rivers and streams in northern mid latitudes have been widely reported during the last two decades, but relatively few studies have dealt with trends in DOC export. We studied the export of DOC from Finnish rivers to the Baltic Sea between 1975 and 2010, and estimated trends in DOC fluxes (both flow normalised and non-normalised). The study encompassed the whole Finnish Baltic Sea catchment area (301,000 km(2)) covering major land use patterns in the boreal zone. Finnish rivers exported annually over 900,000 t DOC to the Baltic Sea, and the mean area specific export was 3.5 t km(-2). The highest export (7.3t km(-2)) was measured in peat dominated catchments, whereas catchments rich in lakes had the lowest export (2.2 t km(-2)). Inter-annual variation in DOC export was high and controlled mainly by hydrology. There was no overall trend in the annual water flow, although winter flow increased in northern Finland over 36 years. Despite the numerous studies showing increases in DOC concentrations in streams and rivers in the northern hemisphere, we could not find any evidence of increases in DOC export to the northern Baltic Sea from Finnish catchments since 1975. Copyright © 2012 Elsevier B.V. All rights reserved.
Mercury bioaccumulation in fishes from subalpine lakes of the Wallowa-Whitman National Forest, northeastern Oregon and western Idaho

USGS Publications Warehouse

Eagles-Smith, Collin A.; Herring, Garth; Johnson, Branden L.; Graw, Rick

2013-01-01

Mercury (Hg) is a globally distributed pollutant that poses considerable risks to human and wildlife health. Over the past 150 years since the advent of the industrial revolution, approximately 80 percent of global emissions have come from anthropogenic sources, largely fossil fuel combustion. As a result, atmospheric deposition of Hg has increased by up to 4-fold above pre-industrial times. Because of their isolation, remote high-elevation lakes represent unique environments for evaluating the bioaccumulation of atmospherically deposited Hg through freshwater food webs, as well as for evaluating the relative importance of Hg loading versus landscape influences on Hg bioaccumulation. The increase in Hg deposition to these systems over the past century, coupled with their limited exposure to direct anthropogenic disturbance make them useful indicators for estimating how changes in Hg emissions may propagate to changes in Hg bioaccumulation and ecological risk. In this study, we evaluated Hg concentrations in fishes of high-elevation, sub-alpine lakes in the Wallowa-Whitman National Forest in northeastern Oregon and western Idaho. Our goals were to (1) assess the magnitude of Hg contamination in small-catchment lakes to evaluate the risk of atmospheric Hg to human and wildlife health, (2) quantify the spatial variability in fish Hg concentrations, and (3) determine the ecological, limnological, and landscape factors that are best correlated with fish total mercury (THg) concentrations in these systems. Across the 28 study lakes, mean THg concentrations of resident salmonid fishes varied as much as 18-fold among lakes. Importantly, our top statistical model explained 87 percent of the variability in fish THg concentrations among lakes with four key landscape and limnological variables— catchment conifer density (basal area of conifers within a lake’s catchment), lake surface area, aqueous dissolved sulfate, and dissolved organic carbon. The basal area of conifers within a lake’s catchment was by far the most important variable explaining fish THg concentrations, with an increase in THg concentrations of more than 400 percent across the forest density spectrum. Across all study lakes, fish THg concentrations ranged from 0.004 to 0.438 milligrams per kilogram wet weight (mg/kg ww). Only a single individual fish sample exceeded the U.S. Environmental Protection Agency’s (USEPA) human health tissue residue criteria of 0.3 mg/kg ww. However, 54 percent of fish (N=177) exceeded the more stringent tissue residue criteria (0.04 mg/kg ww) adopted by the Oregon Department of Environmental Quality to better protect subsistence fishers. Additionally, 2 and 10 percent of fish exceeded levels associated with reduced common loon reproduction and behavior, respectively. Whereas 25 and 68 percent of fish sampled exceeded concentrations deemed protective of mink and kingfisher, respectively. These results suggest that THg concentrations may be present in these lakes at levels associated with ecological risk. It is important to note however, that accurate inference on potential impairment cannot be made within the context of this study design and further research is needed to better quantify these risks.
Climate-landform effects on lateglacial vegetation pattern in northeastern Tuchola Pinewoods (northern Poland): multiproxy evidence from the Lake Czechowskie catchment, northern Poland.

NASA Astrophysics Data System (ADS)

Noryśkiewicz, Agnieszka M.; Kordowski, Jarosław; Tyszkowski, Sebastian; Kramkowski, Mateusz; Zawiska, Izabela; Rzodkiewicz, Monika; Mirosław-Grabowska, Joanna; Ott, Florian; Słowiński, Michał; Obremska, Milena; Błaszkiewicz, Mirosław; Brauer, Achim

2016-04-01

The study area is located in northern Poland in the northeastern part of Tuchola Pinewoods in a young glacially formed and diversified landscape. It comprises the entire lake catchment of Lake Czechowskie (19.76 km2), which comprises a second lake upstream as well as a palaeolake (Trzechowskie) located between the two present-day lakes. Biogenic sediments from eight cores were studied by multiproxy analyses to reconstruct the environmental changes and climate signals during the last Late Glacial and early Holocene. The cores were collected along a W-E transect from Głęboczek Lake to the Czechowskie Lake and were located in different topographic positions (deepest and shallow part of the lake, old lake-bed plains and paleolakes) with a maximum distance of 2.2 km. Detailed and high resolution analyses (pollen, diatoms, cladocera, stable isotopes, geochemistry, varve chronology and radiocarbon dating) to identify the main stages in the development of the natural environment were made. Palynological data indicate melting of the buried ice blocks and the following the onset of biogenic lacustrine sedimentation. The general pattern of vegetation changes in all profiles is similar and includes Late Glacial steppe-tundra plant communities at the onset of organic lake sedimentation. The palynological record of the most profiles shows a high participation of seabuckthorn (Hippophae) in the initial stadium of vegetation history. The lack of this succession in the most western core (Głęboczek Lake) indicates a later period of melt-out processes of the buried dead-ice blocks in the Głęboczek Lake basin. The thickness and type of the accumulated sediments differ significantly during the Bolling-Alerod complex and Younger Dryas Period between our sites. These differences are also reflected in variations of plant species among the different sites. The comparison of different profiles within one catchment allows us to distinguish site specific local responses to climate driven by local factors such as slope steepness and exposure and water depth. This study is a contribution to the Virtual Institute of Integrated Climate and Landscape Evolution Analysis -ICLEA- of the Helmholtz Association
An investigation of enhanced recessions in Poyang Lake: Comparison of Yangtze River and local catchment impacts

NASA Astrophysics Data System (ADS)

Zhang, Qi; Ye, Xu-chun; Werner, Adrian D.; Li, Yun-liang; Yao, Jing; Li, Xiang-hu; Xu, Chong-yu

2014-09-01

Changes in lake hydrological regimes and the associated impacts on water supplies and ecosystems are internationally recognized issues. During the past decade, the persistent dryness of Poyang Lake (the largest freshwater lake in China) has caused water supply and irrigation crises for the 12.4 million inhabitants of the region. There is conjecture as to whether this dryness is caused by climate variability and/or human activities. This study examines long-term datasets of catchment inflow and Lake outflow, and employs a physically-based hydrodynamic model to explore catchment and Yangtze River controls on the Lake's hydrology. Lake water levels fell to their lowest during 2001-2010 relative to previous decades. The average Lake size and volume reduced by 154 km2 and 11 × 108 m3 during the same period, compared to those for the preceding period (1970-2000). Model simulations demonstrated that the drainage effect of the Yangtze River was the primary causal factor. Modeling also revealed that, compared to climate variability impacts on the Lake catchment, modifications to Yangtze River flows from the Three Gorges Dam have had a much greater impact on the seasonal (September-October) dryness of the Lake. Yangtze River effects are attenuated in the Lake with distance from the River, but nonetheless propagate some 100 km to the Lake's upstream limit. Proposals to build additional dams in the upper Yangtze River and its tributaries are expected to impose significant challenges for the management of Poyang Lake. Hydraulic engineering to modify the flow regime between the Lake and the Yangtze River would somewhat resolve the seasonal dryness of the Lake, but will likely introduce other issues in terms of water quality and aquatic ecosystem health, requiring considerable further research.
USE OF A LUMPED MODEL (MAGIC) TO BOUND THE ESTIMATION OF POTENTIAL FUTURE EFFECTS OF SULFUR AND NITROGEN DEPOSITION ON LAKE CHEMISTRY IN THE ADIRONDACK MOUNTAINS

EPA Science Inventory

Leaching of atmospherically deposited nitrogen from forested watersheds can acidify lakes and streams. Using a modified version of the Model of Acidification of Groundwater in Catchments, we made computer simulations of such effects for 36 lake catchments in the Adirondack Mount...
Lake sediment records on climate change and human activities in the Xingyun Lake catchment, SW China.

PubMed

Zhang, Wenxiang; Ming, Qingzhong; Shi, Zhengtao; Chen, Guangjie; Niu, Jie; Lei, Guoliang; Chang, Fengqin; Zhang, Hucai

2014-01-01

Sediments from Xinyun Lake in central Yunnan, southwest China, provide a record of environmental history since the Holocene. With the application of multi-proxy indicators (total organic carbon (TOC), total nitrogen (TN), δ13C and δ15N isotopes, C/N ratio, grain size, magnetic susceptibility (MS) and CaCO3 content), as well as accelerator mass spectrometry (AMS) 14C datings, four major climatic stages during the Holocene have been identified in Xingyun's catchment. A marked increase in lacustrine palaeoproductivity occurred from 11.06 to 9.98 cal. ka BP, which likely resulted from an enhanced Asian southwest monsoon and warm-humid climate. Between 9.98 and 5.93 cal. ka BP, a gradually increased lake level might have reached the optimum water depth, causing a marked decline in coverage by aquatic plants and lake productivity of the lake. This was caused by strong Asian southwest monsoon, and coincided with the global Holocene Optimum. During the period of 5.60-1.35 cal. ka BP, it resulted in a warm and dry climate at this stage, which is comparable to the aridification of India during the mid- and late Holocene. The intensifying human activity and land-use in the lake catchment since the early Tang Dynasty (∼1.35 cal. ka BP) were associated with the ancient Dian culture within Xingyun's catchment. The extensive deforestation and development of agriculture in the lake catchment caused heavy soil loss. Our study clearly shows that long-term human activities and land-use change have strongly impacted the evolution of the lake environment and therefore modulated the sediment records of the regional climate in central Yunnan for more than one thousand years.
Critical loads of acidity for 90,000 lakes in northern Saskatchewan: A novel approach for mapping regional sensitivity to acidic deposition

NASA Astrophysics Data System (ADS)

Cathcart, H.; Aherne, J.; Jeffries, D. S.; Scott, K. A.

2016-12-01

Atmospheric emissions of sulphur dioxide (SO2) from large point sources are the primary concern for acidic deposition in western Canada, particularly in the Athabasca Oil Sands Region (AOSR) where prevailing winds may potentially carry SO2 over acid-sensitive lakes in northern Saskatchewan. A novel catchment-scale regression kriging approach was used to assess regional sensitivity and critical loads of acidity for the total lake population of northern Saskatchewan (89,947 lakes). Lake catchments were delineated using Thiessen polygons, and surface water chemistry was predicted for sensitivity indicators (calcium, pH, alkalinity, and acid neutralizing capacity). Critical loads were calculated with the steady state water chemistry model using regression-kriged base cations, sulphate, and dissolved organic carbon concentrations modelled from surface water observations (n > 800) and digital landscape-scale characteristics, e.g., climate, soil, vegetation, landcover, and geology maps. A large region (>13,726 km2) of two or more indicators of acid sensitivity (pH < 6 and acid neutralizing capacity, alkalinity, calcium < 50 μeq L-1) and low critical loads < 5 meq m-2 yr-1 were predicted on the Athabasca Basin. Exceedance of critical loads under 2006 modelled total sulphate deposition was predicted for 12% of the lakes (covering an area of 3742 km2), primarily located on the Athabasca Basin, within 100 km of the AOSR. There have been conflicting scientific reports of impacts from atmospheric emissions from the AOSR; the results of this study suggest that catchments in the Athabasca Basin within 100 km of the AOSR have received acidic deposition in excess of their critical loads and many of them may be at risk of ecosystem damage owing to their sensitivity.
Chemical fluxes and sensitivity to acidification of two high elevation catchments in southern Wyoming

Treesearch

J. O. Reuss; F. A. Vertucci; R. C. Musselman; R. A. Sommerfeld

1995-01-01

Hydrological and chemical fluxes were examined for East and West Glacier Lakes and their adjacent high-elevation (3200-3700 m) catchments in the Snowy Range of southern Wyoming. Both lakes are approximately 3 ha, but the East Glacier catchment (29 ha) is about half the size of West Glacier. Bedrock is primarily quartzite that has been heavily fractured and crossed with...
Small lakes in big landscape: Multi-scale drivers of littoral ecosystem in alpine lakes.

PubMed

Zaharescu, Dragos G; Burghelea, Carmen I; Hooda, Peter S; Lester, Richard N; Palanca-Soler, Antonio

2016-05-01

In low nutrient alpine lakes, the littoral zone is the most productive part of the ecosystem, and it is a biodiversity hotspot. It is not entirely clear how the scale and physical heterogeneity of surrounding catchment, its ecological composition, and larger landscape gradients work together to sustain littoral communities. A total of 113 alpine lakes from the central Pyrenees were surveyed to evaluate the functional connectivity between littoral zoobenthos and landscape physical and ecological elements at geographical, catchment and local scales, and to ascertain how they affect the formation of littoral communities. At each lake, the zoobenthic composition was assessed together with geolocation, catchment hydrodynamics, geomorphology and topography, riparian vegetation composition, the presence of trout and frogs, water pH and conductivity. Multidimensional fuzzy set models integrating benthic biota and environmental variables revealed that at geographical scale, longitude unexpectedly surpassed altitude and latitude in its effect on littoral ecosystem. This reflects a sharp transition between Atlantic and Mediterranean climates and suggests a potentially high horizontal vulnerability to climate change. Topography (controlling catchment type, snow coverage and lakes connectivity) was the most influential catchment-scale driver, followed by hydrodynamics (waterbody size, type and volume of inflow/outflow). Locally, riparian plant composition significantly related to littoral community structure, richness and diversity. These variables, directly and indirectly, create habitats for aquatic and terrestrial stages of invertebrates, and control nutrient and water cycles. Three benthic associations characterised distinct lakes. Vertebrate predation, water conductivity and pH had no major influence on littoral taxa. This work provides exhaustive information from relatively pristine sites, and unveils a strong connection between littoral ecosystem and catchment heterogeneity at scales beyond the local environment. This underpins the role of alpine lakes as sensors of local and large-scale environmental changes, which can be used in monitoring networks to evaluate further impacts. Copyright © 2016 Elsevier B.V. All rights reserved.
Ecosystem responses during Late Glacial period recorded in the sediments of Lake Łukie (East Poland)

NASA Astrophysics Data System (ADS)

Zawiska, Izabela; Słowiński, Michał; Correa-Metrio, Alex; Obremska, Milena; Luoto, Tomi; Nevalainen, Liisa; Woszczyk, Michał; Milecka, Krystyna

2014-05-01

The main objectives of this study was to reconstruct climate impact on the functioning of Lake Łukie and its catchment (Łęczna Włodawa Lake District, East European Plain) during Late Glacial period. In order to reconstruct climatic fluctuations and corresponding ecosystem responses, we analysed lake sediments for pollen, subfossil Cladocera, plant macrofossils and chemical composition of the sediment. Of these, plant macrofossils and Cladocera were used to infer minimum and mean July temperatures and ordination analysis was used to examine biotic community shifts. Multiproxy analyses of late-glacial sediments of Lake Łukie clearly show that the main driver of aquatic and terrestrial ecosystems as well as geomorphological processes in the catchment was climate variation. The history of the lake initiated during the Older Dryas. In that period, Łęczna Włodawa Lake District was covered by open habitats dominated by grasses (Poaceae), humid sites were occupied by tundra plant communities with less clubmoss (Selaginella selaginoides), dry sites by dominated by steppe-like vegetation with light-demanding species such as Helianthemum, Artemisia, Chenopodiaceae, and juniper bushes (Juniperus). Cold climate limited the growth and development of organisms in the lake, Cladocera community species composition was poor, with only few species present there all the time. During this time period, permafrost was still present in the ground limiting infiltration of rainwater and causing high erosion in the catchment area. Surface runoff is confirmed by the presence of sclerotia of Cenococcum geophilum and high terrigenous silica content. The warming of the early Allerød caused a remarkable change in the natural environment of this area. This is in accordance with the temperature rise reconstructed with the use of plant macrofossils though the Cladocera reconstruction did not recorded the rise than. This temperature increase resulted in turnover of vegetation in the catchment of Lake Łukie, pioneer birch-pine forests dominated, later replaced by pine-birch forests. Consequently this limited the erosion. The results of all proxy suggest the water-lever rise in lake Łukie. The Younger Dryas cooling in the region began about 12 630 14C years BP and recorded in significant drop in temperature reconstructed with plant macrofossils and Cladocera. The cooling resulted in a decline of forest communities and development of open habitats with grasses (Poaceae), Artemisia, and Chenopodiaceae), as well as juniper thickets (Juniperus) At the end of the Younger Dryas, plant communities changed, the non-arborescent pollen declined, while pollen of trees (especially Pinus) became more abundant. This change was more abruptly reflected in Cladocera and aquatic pollen results and is probably related to gradual climate warming. This study is a contribution to the Virtual Institute ICLEA (Integrated Climate and Landscape Evolution Analysis) funded by the Helmholtz Association, projects UMO-2011/01/B/ST10/07367 and N N306 036436 founded by National Science Center, Poland.
Rural plastic emissions into the largest mountain lake of the Eastern Carpathians.

PubMed

Mihai, Florin-Constantin

2018-05-01

The lack of proper waste collection systems leads to plastic pollution in rivers in proximity to rural communities. This environmental threat is more widespread among mountain communities which are prone to frequent flash floods during the warm season. This paper estimates the amounts of plastic bottles dumped into the Izvoru Muntelui lake by upstream rural communities. The plastic pollution dimension between seasonal floods which affected the Bistrita catchment area during 2005-2012 is examined. The floods dumped over 290 tonnes of plastic bottles into the lake. Various scenarios are tested in order to explain each amount of plastic waste collected by local authorities during sanitation activities. The results show that rural municipalities are responsible for 85.51% of total plastic bottles collected during 2005-2010. The source of plastic pollution is mainly local. The major floods of July 2008 and June 2010 collected most of the plastic bottles scattered across the Bistrita river catchment (56 villages) and dumped them into the lake. These comparisons validate the proposed method as a reliable tool in the assessment process of river plastic pollution, which may also be applied in other geographical areas. Tourism and leisure activities are also found to be responsible for plastic pollution in the study area. A new regional integrated waste management system should improve the waste collection services across rural municipalities at the county level when it is fully operational. This paper demonstrates that rural communities are significant contributors of plastics into water bodies.
Rural plastic emissions into the largest mountain lake of the Eastern Carpathians

PubMed Central

2018-01-01

The lack of proper waste collection systems leads to plastic pollution in rivers in proximity to rural communities. This environmental threat is more widespread among mountain communities which are prone to frequent flash floods during the warm season. This paper estimates the amounts of plastic bottles dumped into the Izvoru Muntelui lake by upstream rural communities. The plastic pollution dimension between seasonal floods which affected the Bistrita catchment area during 2005–2012 is examined. The floods dumped over 290 tonnes of plastic bottles into the lake. Various scenarios are tested in order to explain each amount of plastic waste collected by local authorities during sanitation activities. The results show that rural municipalities are responsible for 85.51% of total plastic bottles collected during 2005–2010. The source of plastic pollution is mainly local. The major floods of July 2008 and June 2010 collected most of the plastic bottles scattered across the Bistrita river catchment (56 villages) and dumped them into the lake. These comparisons validate the proposed method as a reliable tool in the assessment process of river plastic pollution, which may also be applied in other geographical areas. Tourism and leisure activities are also found to be responsible for plastic pollution in the study area. A new regional integrated waste management system should improve the waste collection services across rural municipalities at the county level when it is fully operational. This paper demonstrates that rural communities are significant contributors of plastics into water bodies. PMID:29892426
The recent climatic change of subarctic zone recorded in lake sediments in Hokkaido, Japan

NASA Astrophysics Data System (ADS)

Seto, K.; Takata, H.; Saito, M.; Katsuki, K.; Sonoda, T.; Kawajiri, T.; Watanabe, T.

2010-12-01

In the coastal area of the Sea of Okhotsk in the east part of Hokkaido located to for subarctic zone, many brackish-water lakes are distributed. Especially, the Okhotsk brackish-water lake group around Abashiri City is constituted by major lake in Japan such as Lake Abashiri, Lake Mokoto, Lake Tofutsu, and Lake Notoro. The each lake shows a different present environment and history. Therefore, the change that is common in those lakes seems to be the change concerning the climate. In this study, recent environment change in Abashiri region (after the Little Ice Age) is discussed by sedimentologic and geochemical high-resolution analysis of the cores collected from the Okhotsk brackish-water lake group. The cores collected from four lake shows the length of 1 to 3m. In Lake Mokoto, there was the Ta-a tephra (AD 1739) at the 350cm depth. The Ta-a tephra are found at the horizon of 250 cm in Lake Abashiri, of 78 cm in Lake Notoro, and of 44 cm in Lake Tofutsu. The differences of the sedimentation rate of that lake are caused by the size of lake and catchment area. In Lake Mokoto, the catchment area is most large, and the size of lake is smallest among the four lake of Abashiri City. The cores collected from Lake Abashiri and Lake Mokoto consist of organic mud with the lamination in all cores. The core top 56 cm shows the black (N1.5/0, L value: < 5), and it seems to indicate the euxinic environment as present. The organic mud of 56-77cm-depth show black (2.5GY2/1, L values = ca 20), and it is considered that it shows the freshwater environment. In history of Lake Abashiri, the lake water changes to brackish-water from freshwater in 1930’s. It is considered that the change of the lightness in 56 cm depth is correspondent to this timing. In the observation by the soft X-ray photograph, the pattern of the lamination of Lake Abashiri is similar to the Lake Mokoto. The cyclic lamination set is observed in the core from Lake Mokoto. It is considered that this cyclic lamination set is the verve. According to the meteorological data in Abashiri region, the precipitation of every year is high in August to September. Probably, the cyclic lamination set is formed by cyclic change of precipitation. In correlation with the core in Lake Abashiri and Lake Mokoto by the pattern of the lamination, there is consistent with the counting age of cyclic lamination set in Lake Mokoto and the timing of environmental change in Lake Abashiri.
Using groundwater age to understand sources and dynamics of nutrient contamination through the catchment into Lake Rotorua, New Zealand

NASA Astrophysics Data System (ADS)

Morgenstern, U.; Daughney, C. J.; Leonard, G.; Gordon, D.; Donath, F. M.; Reeves, R.

2014-08-01

The water quality of Lake Rotorua has declined continuously over the past 50 yr despite mitigation efforts over recent decades. Delayed response of the groundwater discharges to historic land-use intensification 50 yr ago was the reason suggested by early tritium measurements, which indicated large transit times through the groundwater system. We use the isotopic and chemistry signature of the groundwater for detailed understanding of the origin, fate, flow pathways, lag times, and future loads of contaminants. A unique set of high-quality tritium data over more than four decades, encompassing the time when the tritium spike from nuclear weapons testing moved through the groundwater system, allows us to determine detailed age distribution parameters of the water discharging into Lake Rotorua. The Rotorua volcanic groundwater system is complicated due to the highly complex geology that has evolved through volcanic activity. Vertical and steeply-inclined geological contacts preclude a simple flow model. The extent of the Lake Rotorua groundwater catchment is difficult to establish due to the deep water table in large areas, combined with inhomogeneous groundwater flow patterns. Hierarchical cluster analysis of the water chemistry parameters provided evidence of the recharge source of the large springs near the lake shore, with discharge from the Mamaku ignimbrite through lake sediment layers. Groundwater chemistry and age data show clearly the source of nutrients that cause lake eutrophication, nitrate from agricultural activities and phosphate from geologic sources. With a naturally high phosphate load reaching the lake continuously via all streams, the only effective way to limit algae blooms and improve lake water quality in such environments is by limiting the nitrate load. The groundwater in the Rotorua catchment, once it has passed through the soil zone, shows no further decrease in dissolved oxygen, indicating absence of electron donors in the aquifer that could facilitate microbial denitrification reactions. Nitrate from land-use activities that leaches out of the root zone of agricultural land into the deeper part of the groundwater system must be expected to travel with the groundwater to the lake. The old age and the highly mixed nature of the water discharges imply a very slow and lagged response of the streams and the lake to anthropogenic contaminants in the catchment, such as nitrate. Using the age distribution as deduced from tritium time series data measured in the stream discharges into the lake allows prediction of future nutrient loads from historic land-use activities 50 yr ago. For Hamurana Stream, the largest stream to Lake Rotorua, it takes more than a hundred years for the groundwater-dominated stream discharge to adjust to changes in land-use activities. These time scales apply to activities that cause contamination, but also to remediation action.
Trace element distribution in the water and sediments of certain storage lakes from the Jijia catchment, (Romania)

NASA Astrophysics Data System (ADS)

Dughila, A.; Iancu, O. G.; Romanescu, G. T.

2012-04-01

The present study aims at investigating the concentrations and distribution levels of a series of trace elements in water and sediment samples collected from six storage lakes located in the Jijia catchment - NE of Romania. The lakes are multi-purpose water reservoirs, three of them being mainly used as a source of municipal drinking water, or for fishing, irrigation for the farms in the area, protection against floods and the regulation of river flows. By contrast, agricultural wastes, fertilizers, raw sewage effluents and road runoff constitute the predominant anthropogenic sources, which supply the lakes in question with Cd, Cu, Pb and Zn. The present study was conducted on a series of 63 sediment samples and 18 water samples, collected from the same locations, in order to establish the distribution levels of certain trace elements from the water through sediments. Sediment cores were collected from two sections across each lake by means of a motor boat, using a system that consists of a graduated sampling tube (0.9 m in length and 72.5 mm in diameter) made of Plexiglas (Eijkelkamp sample tube guide). Prior to the analyses, the samples were air-dried, ground and homogenized using an agate mortar, oven-dried at 50 °C for 6 days and then sieved through 63 µm sieves. The sediment and water samples were subjected to a digestion technique with concentrated nitric acid using a microwave oven (Berghof type), and analyzed for the following elements: Pb, Zn, Cu, Cd, Cr and Ni. The total concentration of the elements was measured through atomic absorption spectrometry (AAS) with an RSD of < 10 % from solutions. The vertical distribution of most elements in the cores examined could be characterized as relatively uniform, with higher concentrations for those collected from the lakes which are more influenced by anthropogenic factors, compared to those situated in forested areas. The lake-water quality characteristics were below the recommended drinking water standards imposed by the current legislation (MMGA Ord. No. 161/16.02.2006 - Normative regarding the classification of surface waters in order to establish the ecological status of water bodies, which combines European and Romanian provisions), with the exception of copper (with very high concentrations in all the water samples), lead and cadmium. Keywords: AAS, Jijia catchment (Romania), lake water, sediment core, trace elements
Spatial and Temporal Variability of Dust Deposition in the San Juan Mountains, CO: A Network of Late Holocene Lake Sediment Records

NASA Astrophysics Data System (ADS)

Arcusa, S.; Routson, C.; McKay, N.

2017-12-01

Millions of stakeholders living in the arid southwestern US rely on snowmelt from the San Juan Mountains of Colorado. However, dust deposition on snow accelerates snowmelt, challenging water management. Dustiness in the southwestern US is primarily mediated by drought, which is projected to increase in frequency and severity. Over the past several millennia, multidecadal-length megadroughts are hypothesized to have enhanced regional dustiness. These past megadroughts were more frequent during the Roman (ca. 1-400 CE) and Medieval (ca. 800-1300 CE) time periods and were similar in duration and severity to those projected for the future. Developing an understanding of the temporal and spatial patterns of past dust deposition in the San Juan Mountains will help inform adaptation strategies for future droughts. A network of short sediment cores from six alpine lakes in the San Juan Mountains were collected in 2016 and 2017 to investigate the spatial patterns of dust deposition. The range in lake basin characteristics in the network, such as catchment size, helps to constrain the influence of secondary dust deposition. Grain size analysis and X-ray Fluorescence were combined with radiocarbon dating to trace the temporal patterns in dust flux over the Late Holocene (the last 2000 years). The End-member Modelling Algorithm (EMMA) was used to estimate the dust proportion in the lake sediment, distinguishing from locally derived catchment material. Comparisons to modern dust-on-snow samples were made to identify the dust size distribution. The results show that deposition trends were not uniform between the south-eastern and north-western San Juans, with increasing trends towards the present in the former, possibly reflecting a shift in dust sources associated with changes in wind speed and direction. Dust levels greater than long term averages were recorded during the Medieval and Roman periods. The network also showed the influence of lake basin parameters, such as the ratio of lake surface to drainage area, on dust flux levels. Lakes with a larger catchment compared to the lake surface area receive more dust, possibly including secondary deposition. The results support the hypothesis that past megadroughts occurred in a dustier setting with implications for future drought adaptation and water management.
Vulnerability of European freshwater catchments to climate change.

PubMed

Markovic, Danijela; Carrizo, Savrina F; Kärcher, Oskar; Walz, Ariane; David, Jonathan N W

2017-09-01

Climate change is expected to exacerbate the current threats to freshwater ecosystems, yet multifaceted studies on the potential impacts of climate change on freshwater biodiversity at scales that inform management planning are lacking. The aim of this study was to fill this void through the development of a novel framework for assessing climate change vulnerability tailored to freshwater ecosystems. The three dimensions of climate change vulnerability are as follows: (i) exposure to climate change, (ii) sensitivity to altered environmental conditions and (iii) resilience potential. Our vulnerability framework includes 1685 freshwater species of plants, fishes, molluscs, odonates, amphibians, crayfish and turtles alongside key features within and between catchments, such as topography and connectivity. Several methodologies were used to combine these dimensions across a variety of future climate change models and scenarios. The resulting indices were overlaid to assess the vulnerability of European freshwater ecosystems at the catchment scale (18 783 catchments). The Balkan Lakes Ohrid and Prespa and Mediterranean islands emerge as most vulnerable to climate change. For the 2030s, we showed a consensus among the applied methods whereby up to 573 lake and river catchments are highly vulnerable to climate change. The anthropogenic disruption of hydrological habitat connectivity by dams is the major factor reducing climate change resilience. A gap analysis demonstrated that the current European protected area network covers <25% of the most vulnerable catchments. Practical steps need to be taken to ensure the persistence of freshwater biodiversity under climate change. Priority should be placed on enhancing stakeholder cooperation at the major basin scale towards preventing further degradation of freshwater ecosystems and maintaining connectivity among catchments. The catchments identified as most vulnerable to climate change provide preliminary targets for development of climate change conservation management and mitigation strategies. © 2017 John Wiley & Sons Ltd.
Catchment-mediated atmospheric nitrogen deposition drives ecological change in two alpine lakes in SE Tibet.

PubMed

Hu, Zhujun; Anderson, Nicholas John; Yang, Xiangdong; McGowan, Suzanne

2014-05-01

The south-east margin of Tibet is highly sensitive to global environmental change pressures, in particular, high contemporary reactive nitrogen (Nr) deposition rates (ca. 40 kg ha(-1) yr(-1) ), but the extent and timescale of recent ecological change is not well prescribed. Multiproxy analyses (diatoms, pigments and geochemistry) of (210) Pb-dated sediment cores from two alpine lakes in Sichuan were used to assess whether they have undergone ecological change comparable to those in Europe and North America over the last two centuries. The study lakes have contrasting catchment-to-lake ratios and vegetation cover: Shade Co has a relatively larger catchment and denser alpine shrub than Moon Lake. Both lakes exhibited unambiguous increasing production since the late 19th to early 20th. Principle component analysis was used to summarize the trends of diatom and pigment data after the little ice age (LIA). There was strong linear change in biological proxies at both lakes, which were not consistent with regional temperature, suggesting that climate is not the primary driver of ecological change. The multiproxy analysis indicated an indirect ecological response to Nr deposition at Shade Co mediated through catchment processes since ca. 1930, while ecological change at Moon Lake started earlier (ca. 1880) and was more directly related to Nr deposition (depleted δ(15) N). The only pronounced climate effect was evidenced by changes during the LIA when photoautotrophic groups shifted dramatically at Shade Co (a 4-fold increase in lutein concentration) and planktonic diatom abundance declined at both sites because of longer ice cover. The substantial increases in aquatic production over the last ca. 100 years required a substantial nutrient subsidy and the geochemical data point to a major role for Nr deposition although dust cannot be excluded. The study also highlights the importance of lake and catchment morphology for determining the response of alpine lakes to recent global environmental forcing. © 2013 John Wiley & Sons Ltd.
A late Holocene record of solar-forced atmospheric blocking variability over Northern Europe inferred from varved lake sediments of Lake Kuninkaisenlampi

NASA Astrophysics Data System (ADS)

Saarni, Saija; Muschitiello, Francesco; Weege, Stefanie; Brauer, Achim; Saarinen, Timo

2016-12-01

This study presents a new varved lake sediment sequence from Lake Kuninkaisenlampi, Eastern Finland. The record is constituted by alternations of clastic and biogenic laminae and provides a precise chronology extending back to 3607 ± 94 varve yrs. BP. The seasonality of the boreal climatic zone, with cold winters and mild summers, is reflected in the varve structure as a succession of three laminae from bottom to top, (i) a coarse to fine-grained detrital lamina marked by detrital catchment material transported by spring floods; (ii) a biogenic lamina with diatoms, plant and insect remnants reflecting biological productivity during the season of lake productivity; and (iii) a very fine amorphous organic lamina deposited during the winter stratification. The thickness of the detrital lamina in the lake reflects changes in the rate of spring snow melt in the catchment and is, therefore, considered a proxy for winter conditions. Hence, the record allows reconstructing local climate and environmental conditions on inter-annual to the multi-centennial timescales. We find that minerogenic accumulation reflected in the detrital lamina exhibits a high multi-decadal to centennial-scale spectral coherency with proxies for solar activity, such as Δ14C, and Total Solar Irradiance, suggesting a strong link between solar variability and sediment transport to the lake basin. Increased catchment erosion is observed during periods of low solar activity, which we ascribe to the development of more frequent atmospheric winter blocking circulation induced by solar-forced changes in the stratosphere. We suggest that soil frost in the catchment of Lake Kuninkaisenlampi related to more frequent winter blocking led to increased surface run-off and ultimately to increased catchment erosion during spring. We conclude that, during the past ca 3600 years, solar forcing may have modulated multi-decadal to centennial variations in sedimentation regimes in lakes from Eastern Finland and potentially in other North European lakes.
Impact of land use changes on hydrology of Mt. Kilimanjaro. The case of Lake Jipe catchment

NASA Astrophysics Data System (ADS)

Ngugi, Keziah; Ogindo, Harun; Ertsen, Maurits

2015-04-01

Mt. Kilimanjaro is an important water tower in Kenya and Tanzania. Land degradation and land use changes have contributed to dwindling surface water resources around Mt. Kilimanjaro. This study focuses on Lake Jipe catchment of about 451Km2 (Ndetei 2011) which is mainly drained by River Lumi, a tributary of river Pangani. River Lumi starts from Mt. Kilimanjaro and flows North east wards to cross the border from Tanzania to Kenya eventually flowing into Lake Jipe which is a trans-boundary lake. The main purpose of this study was to investigate historical land use changes and relate this to reduction in surface water resources. The study will propose measures that could restore the catchment thereby enhancing surface water resources feeding Lake Jipe. A survey was conducted to document community perspectives of historical land use changes. This information was corroborated using Landsat remote sensed images spanning the period 1985-2013 to determine changes in the land cover due to human activities on Lake Jipe Catchment. River Lumi flow data was obtained from Water Resources Management Authority and analyzed for flow trends. The dwindling extent of the Lake was obtained from the community's perspective survey and by Landsat images. Community survey and remote sensing indicated clearing of the forest on the mountain and conversion of the same to crop production fields; damming of river Lumi in Tanzania, conversion of bush land to crop production fields further downstream of river Lumi and irrigation. There is heavy infestation of the invasive species Prosopis juliflora which had aggressively colonized grazing land and blocked irrigation canals. Other land use changes include land fragmentation due to subdivision. Insecure land tenure was blamed for failure by farmers to develop soil and water conservation infrastructure. Available River gauging data showed a general decline in river flow. Heavy flooding occurred during rainy seasons. Towards Lake Jipe after the river gauging station, several springs discharge into river Lumi and the river becomes permanent. The community believes Lake Jipe is a dying lake and will be gone in the coming years unless interventions to save it are implemented. Most of river Lumi water was delivered directly into the lakes outlet, river Ruvu, thus by-passing Lake Jipe. This was due to siltation that blocked river Lumis mouth. Consequently, lake Jipes volume and surface area have reduced dramatically from over the years. Drying of Lake Jipe will affect a lot of people who depend on the lake and the ecosystem. Addressing the problems requires re-afforestation measures and soil and moisture conservation. The severe runoff need to be dammed especially on the Kenyan side to create artificial surface water resources. River Lumi should be trained to discharge into the lake. Land tenure security need to be improved as incentives for proper land utilization. New farming methods to increase land productivity will encourage farmers to practice soil and water conservation measure.

Effects of lakes and reservoirs on annual river nitrogen, phosphorus, and sediment export in agricultural and forested landscapes

USGS Publications Warehouse

Powers, Stephen M.; Robertson, Dale M.; Stanley, Emily H.

2014-01-01

Recently, effects of lakes and reservoirs on river nutrient export have been incorporated into landscape biogeochemical models. Because annual export varies with precipitation, there is a need to examine the biogeochemical role of lakes and reservoirs over time frames that incorporate interannual variability in precipitation. We examined long-term (~20 years) time series of river export (annual mass yield, Y, and flow-weighted mean annual concentration, C) for total nitrogen (TN), total phosphorus (TP), and total suspended sediment (TSS) from 54 catchments in Wisconsin, USA. Catchments were classified as small agricultural, large agricultural, and forested by use of a cluster analysis, and these varied in lentic coverage (percentage of catchment lake or reservoir water that was connected to river network). Mean annual export and interannual variability (CV) of export (for both Y and C) were higher in agricultural catchments relative to forested catchments for TP, TN, and TSS. In both agricultural and forested settings, mean and maximum annual TN yields were lower in the presence of lakes and reservoirs, suggesting lentic denitrification or N burial. There was also evidence of long-term lentic TP and TSS retention, especially when viewed in terms of maximum annual yield, suggesting sedimentation during high loading years. Lentic catchments had lower interannual variability in export. For TP and TSS, interannual variability in mass yield was often >50% higher than interannual variability in water yield, whereas TN variability more closely followed water (discharge) variability. Our results indicate that long-term mass export through rivers depends on interacting terrestrial, aquatic, and meteorological factors in which the presence of lakes and reservoirs can reduce the magnitude of export, stabilize interannual variability in export, as well as introduce export time lags.
Using isotopes to quantify evaporation and non-stationary transit times distributions in lake water budgets

NASA Astrophysics Data System (ADS)

Smith, A. A.; Tetzlaff, D.; Soulsby, C.

2017-12-01

Evaporative fluxes from northern lakes are essential components of catchment water balances, providing large supplies of water to the atmosphere, and affecting downstream water availability. However, measurement of lake evaporation is difficult in many catchments due to remoteness and inaccessibility. Evaporative flux may also influence mean transit times of lakes and catchments, identified through water- and tracer mass-balance. We combined stable water isotopes (δ2H and δ18O), transit, and residence time distributions in a non-stationary transit time model to estimate the evaporative flux from two lakes in the Scottish Highlands. The lakes were in close proximity to each other ( 2km), shallow (mean depth, 1.5 m) with one large (0.88km2) and one small (0.4km2). Model calibration used measurements of precipitation, air temperature, water level, and isotopic stream compositions of lake inflow and outflows. Evaporation flux was identified using lake fractionation of δ2H and δ18O. Mixing patterns of the lakes and their respective outlet isotopic compositions were accounted for by comparing three probability distributions for discharge and evaporation. We found that the evaporation flux was strongly influenced by these discharge and evaporation distributions. Decreased mixing within the lake resulted in greater evaporation fluxes. One of the three distributions yielded similar mean daily evaporation and uncertainty for both lakes (max 5mm/day), while evaporation using the other two distributions was inconsistent between the lakes. Importantly, our approach also estimated distributions of evaporation age, which were significantly different between the lakes, reflecting a combination of inflow stream magnitude and the mixing regimes. The mean evaporation flux age of the large lake was 160 days, and 14 days for the small lake. Our integrated approach of stable isotopes, time variant transit time distributions has shown to be a useful tool for quantifying evaporative fluxes and closing the water balance, while simultaneously providing useful transit times of fluxes for lake dominated catchments.
The relationship of catchment topography and soil hydraulic characteristics to lake alkalinity in the northeastern United States

USGS Publications Warehouse

Wolock, D.M.; Hornberger, G.M.; Beven, K.J.; Campbell, W.G.

1989-01-01

We undertook the task of determining whether base flow alkalinity of surface waters in the northeastern United States is related to indices of soil contact time and flow path partitioning that are derived from topographic and soils information. The influence of topography and soils on catchment hydrology has been incorporated previously in the variable source area model TOPMODEL as the relative frequency distribution of ln (a/Kb tan B), where ln is the Naperian logarithm, “a” is the area drained per unit contour, K is the saturated hydraulic conductivity, b is the soil depth, and tan B is the slope. Using digital elevation and soil survey data, we calculated the ln (a/Kb tan B) distribution for 145 catchments. Indices of flow path partitioning and soil contact time were derived from the ln (a/Kb tan B) distributions and compared to measurements of alkalinity in lakes to which the catchments drain. We found that alkalinity was, in general, positively correlated with the index of soil contact time, whereas the correlation between alkalinity and the flow path partitioning index was weak at best. A portion of the correlation between the soil contact time index and alkalinity was attributable to covariation with soil base saturation and cation exchange capacity, while another portion was found to be independent of these factors. Although our results indicate that catchments with long soil contact time indices are most likely to produce high alkalinity base flow, a sensitivity analysis of TOPMODEL suggests that surface waters of these same watersheds may be susceptible to alkalinity depressions during storm events, due to the role of flow paths.
A Tale of Two Lakes: Catchment-Specific Responses to Late Holocene Cooling in Northwest Iceland

NASA Astrophysics Data System (ADS)

Crump, S. E.; Florian, C. R.; Miller, G. H.; Geirsdottir, A.; Zalzal, K.

2015-12-01

Lake sediments are frequently utilized for reconstructing paleoclimate in the Arctic, particularly in Iceland, where high sedimentation rates and abundant tephra layers allow for the development high-resolution, well-dated records. However, when developing climate records using biological proxies, catchment-specific processes must be understood and separated from the primary climate signal in order to develop accurate reconstructions. In this study, we compare proxy records (biogenic silica [BSi], C:N, ∂13C, and algal pigments) of the last 2 ka from two nearby lakes in northwest Iceland in order to elucidate how different catchments respond to similar climate history. Torfdalsvatn and Bæjarvötn are two coastal lakes located 60 km apart; mean summer temperatures are highly correlated between the two sites over the instrumental record, and likely for the past 2 ka as well. Consistent with other Icelandic records, both lakes record cooling as decreasing aquatic productivity (BSi) over the last 2 ka. Both sediment cores also record the onset of landscape destabilization, reflected by increased terrestrial input (C:N and ∂13C), which suggests an intensification of cooling. However, the timing and magnitude of this shift differ markedly between lakes. Biological proxies indicate gradual landscape destabilization beginning ~900 AD at Torfdalsvatn in contrast to a sharper, more intense landscape destabilization at ~1400 AD at Bæjarvötn. Because temperatures at the two lakes are well correlated, contrasting proxy responses are likely the result of catchment-specific thresholds and processes. Specifically, a steeper catchment at Bæjarvötn may allow for a more pronounced influx of terrestrial material as the critical shear stress for soil erosion is surpassed more readily. The impact of human colonization on erosion rates is also critical to assess, and recent developments in lipid biomarkers will allow for more precise reconstructions of human activity in each catchment.
Using Water Isotope Tracers to Investigate Past and Present Water Balance Conditions in the Old Crow Flats, Yukon Territory

NASA Astrophysics Data System (ADS)

Turner, K.; Wolfe, B. B.; Edwards, T. W.

2010-12-01

The Old Crow Flats (OCF), Yukon Territory, is a wetland of international significance that comprises approximately 2700 shallow thermokarst lakes. Located near the northern limit of the boreal forest, the OCF provides vital habitat for abundant wildlife including waterfowl, moose, muskrat, and the Porcupine Caribou Herd, which support the traditional lifestyle of the Vuntut Gwitchin First Nation. Thermokarst lakes, which occupy vast northern regions, are greatly influenced by climate conditions. In the OCF and other regions there have been observations of decreasing water levels and an increase in frequency of lake drainage events over recent decades. Though there is widespread concern that thermokarst landscape changes are accelerating as a result of ongoing climate change, there are few studies that have investigated current and past variability of lake water balances and climate interactions at the landscape scale. As part of a Government of Canada International Polar Year multidisciplinary project, the present and past hydrology of lakes spanning the OCF are being investigated using water isotope tracers and paleolimnological approaches. Water samples were obtained from 57 lakes three times over three ice-free seasons (2007-09) and analyzed for oxygen and hydrogen isotope composition in order to capture seasonal and interannual changes in water balance conditions. Results highlight strong diversity in the hydrology of lakes throughout the OCF. Based on patterns of isotopic evolution and calculations of input source compositions and evaporation-to-inflow ratios, we identified snowmelt-dominated, rainfall-dominated, groundwater-influenced, evaporation-dominated and drained lake types, which represent the dominant hydrological processes influencing lake water balances. Lake physical and catchment land cover characteristics influence dominant input type (rain or snow). Snowmelt-dominated catchments are large relative to lake surface areas and typically contain woodland or large willow land cover that allows for greater snowpack development in contrast to rainfall-dominated lakes, which have catchments dominated by tundra vegetation that are typically smaller relative to lake areas. Precipitation during the three-year study was highly variable and strongly influenced water balance conditions. For example, in years of reduced precipitation, many rainfall-dominated lakes are susceptible to becoming evaporation-dominated late in the ice-free season, whereas prolonged wet conditions can lead to increased thermokarst activity and subsequent lake drainage events. Approaches used in this modern water balance study are readily transferable to other northern thermokarst landscapes in order to develop greater insight into landscape-scale responses to ongoing climate change. Additionally, knowledge of modern water balance variability throughout the OCF provides the basis for interpretation of past limnological conditions, which are being determined through ongoing paleolimnological analyses. Key findings will be used to enhance our ability to anticipate how the water balance of lakes in the OCF will respond to future climate change.
Vegetation, climate and lake changes over the last 7000 years at the boreal treeline in north-central Siberia

NASA Astrophysics Data System (ADS)

Klemm, Juliane; Herzschuh, Ulrike; Pestryakova, Luidmila A.

2016-09-01

Palaeoecological investigations in the larch forest-tundra ecotone in northern Siberia have the potential to reveal Holocene environmental variations, which likely have consequences for global climate change because of the strong high-latitude feedback mechanisms. A sediment core, collected from a small lake (radius ∼100 m), was used to reconstruct the development of the lake and its catchment as well as vegetation and summer temperatures over the last 7100 calibrated years. A multi-proxy approach was taken including pollen and sedimentological analyses. Our data indicate a gradual replacement of open larch forests by tundra with scattered single trees as found today in the vicinity of the lake. An overall trend of cooling summer temperature from a ∼2 °C warmer-than-present mid-Holocene summer temperatures until the establishment of modern conditions around 3000 years ago is reconstructed based on a regional pollen-climate transfer function. The inference of regional vegetation changes was compared to local changes in the lake's catchment. An initial small water depression occurred from 7100 to 6500 cal years BP. Afterwards, a small lake formed and deepened, probably due to thermokarst processes. Although the general trends of local and regional environmental change match, the lake catchment changes show higher variability. Furthermore, changes in the lake catchment slightly precede those in the regional vegetation. Both proxies highlight that marked environmental changes occurred in the Siberian forest-tundra ecotone over the course of the Holocene.
Lakes as sentinels of climate change

PubMed Central

Adrian, Rita; O’Reilly, Catherine M.; Zagarese, Horacio; Baines, Stephen B.; Hessen, Dag O.; Keller, Wendel; Livingstone, David M.; Sommaruga, Ruben; Straile, Dietmar; Van Donk, Ellen; Weyhenmeyer, Gesa A.; Winder, Monika

2010-01-01

While there is a general sense that lakes can act as sentinels of climate change, their efficacy has not been thoroughly analyzed. We identified the key response variables within a lake that act as indicators of the effects of climate change on both the lake and the catchment. These variables reflect a wide range of physical, chemical, and biological responses to climate. However, the efficacy of the different indicators is affected by regional response to climate change, characteristics of the catchment, and lake mixing regimes. Thus, particular indicators or combinations of indicators are more effective for different lake types and geographic regions. The extraction of climate signals can be further complicated by the influence of other environmental changes, such as eutrophication or acidification, and the equivalent reverse phenomena, in addition to other land-use influences. In many cases, however, confounding factors can be addressed through analytical tools such as detrending or filtering. Lakes are effective sentinels for climate change because they are sensitive to climate, respond rapidly to change, and integrate information about changes in the catchment. PMID:20396409
A review on the establishment and research in hydrological experimental areas (catchments) in plain areas in China and abroad

NASA Astrophysics Data System (ADS)

Yang, Hai; Wang, Chuanhai; Hua, Wenjuan

2017-04-01

This paper reviewed some specific conceptions of hydrological experimental areas (catchments) while found that the traditional definition of 'catchment' may be difficult to meet in plain areas. According to the review of development history and current situation of hydrological experimental areas (catchments) in plain areas in China, 4 stages were shown besides the recent 10 years, i.e., 'golden stage(1952-1966)', 'backward stage(1966-1986)', 'short recovery stage(1986-1989)' and 'stagnant stage(1986-2006)'. It gets new impetus since 2006 with some investigation work promoted by the government. Furthermore, some historic problems during establishing experimental areas (catchments) in plain areas were revealed based on the document literature and a few meaningful lessons were drawn from the past. It was also the first time to collect and classify the details of both 11 representative experimental areas in China and abroad, after that a brief comparison about the measurement level and research directions was made between two regions. Additionally, we took the experimental research work in the plain of Taihu Lake Basin as example and introduced the particular research goals and the corresponding establishing process, including how to design the experimental area, eg, size, location, land use type, arranging the measurement instruments et al. We hope such case can provide a reference for newly-building, recovering and extending hydrological experimental areasin plain areas in the future. Finally, this paper prospected the future development in establishment and research in hydrological experimental areas (catchments) in plain areas. It may be more common to see the cooperation between model scientists and field experts. Because of the comprehensive goals in water problems, researchers from various fields would work together in the future experimental research work. Scale study and modelling in plain areas will be a promising branch after some typical experimental areas with different land use types are established. Facing such hopeful opportunities, we also made some suggestions.
Seasonal variation of oxygen-18 in precipitation and surface water of the Poyang Lake Basin, China.

PubMed

Hu, Chunhua; Froehlich, Klaus; Zhou, Peng; Lou, Qian; Zeng, Simiao; Zhou, Wenbin

2013-06-01

Based on the monthly δ(18)O value measured over a hydrology period in precipitation, runoff of five tributaries and the main lake of the Poyang Lake Basin, combined with hydrological and meteorological data, the characteristics of δ(18)O in precipitation (δ(18)OPPT) and runoff (δ(18)OSUR) are discussed. The δ(18)OPPT and δ(18)OSUR values range from-2.75 to-14.12 ‰ (annual mean value=-7.13 ‰ ) and from-2.30 to-8.56 ‰, respectively. The seasonal variation of δ(18)OPPT is controlled by the air mass circulation in this region, which is dominated by the Asian summer monsoon and the Siberian High during winter. The correlation between the wet seasonal averages of δ(18)OSUR in runoff of the rivers and δ(18)OPPT of precipitation at the corresponding stations shows that in the Poyang Lake catchment area the river water consists of 23% direct runoff (precipitation) and 77% base flow (shallow groundwater). This high proportion of groundwater in the river runoff points to the prevalence of wetland conditions in the Poyang Lake catchment during rainy season. Considering the oxygen isotopic composition of the main body of Poyang Lake, no isotopic enrichment relative to river inflow was found during the rainy season with maximum expansion of the lake. Thus, evaporation causing isotopic enrichment is a minor component of the lake water balance in the rainy period. During dry season, a slight isotopic enrichment has been observed, which suggests a certain evaporative loss of lake water in that period.
Assessment of heavy metal enrichment and its human impact in lacustrine sediments from four lakes in the mid-low reaches of the Yangtze River, China.

PubMed

Bing, Haijian; Wu, Yanhong; Liu, Enfeng; Yang, Xiangdong

2013-07-01

Sediments from four lakes in the mid-low reaches of the Yangtze River, Taibai Lake, Longgan Lake, Chaohu Lake and Xijiu Lake, were chosen to evaluate their enrichment state and history. The state of heavy metal enrichment was at a low level in the sediment of Taibai Lake and Longgan Lake. The enrichment state of Co, Cr and Ni was also low in the sediment of Chaohu Lake and Xijiu Lake, while Cu, Pb and Zn enrichment reached a higher level. Mass accumulation fluxes were calculated to quantitatively evaluate the anthropogenic contribution to heavy metals in the sediment. The anthropogenic accumulation fluxes were lower in the sediment of Taibai Lake and Longgan Lake compared with the other two lakes, where heavy metals, especially Cu, Pb and Zn, were mainly from anthropogenic sources. Heavy metal accumulation did not vary greatly in the sediment of Taibai Lake and Longgan Lake, while that in Chaohu Lake and Xijiu Lake increased since the 1950s and substantially increased since the 1980s, although a decrease occurred since 2000 AD in Xijiu Lake. Heavy metal enrichment was strongly related to human activities in the catchment. The development of urbanization and industrialization was much more rapid in the catchments of Chaohu Lake and Xijiu Lake than of the other two lakes, and thus large amounts of anthropogenically sourced heavy metals were discharged into the lakes, which resulted in a higher contamination risk. However, human activities in the Longgan Lake and Taibai Lake catchments mainly involved agriculture, which contributed a relatively small portion of heavy metals to the lakes.
Mercury in the central European lake district - case study Plešné lake

NASA Astrophysics Data System (ADS)

Navratil, Tomas; Rohovec, Jan; Novakova, Tereza; Matouskova, Sarka; Kopacek, Jiri; Kana, Jiri

2017-04-01

The central European lake district extends within the Bohemian forest and Bavarian forest Mountains. It includes 8 glacial lakes extending in altitudes from 935 to 1087 m a.s.l. All of them have been oligotrophic and forests of the lake catchments are dominated by Norway spruce (Picea abies). Plešné lake (PL) catchment is at 1087 m .a.s.l. and it covers area of 0.67 km2. In 2004, the forest at PL catchment was infested by the bark beetle (Ips typographus) and 88%-99% of trees had died by 2011. In contrast to relatively detailed research of North American and Scandinavian lake ecosystems the information concerning Hg contamination of central European lake ecosystems are rather scarce. The PL ecosystem can provide base for assessment of Hg contamination as well as for changes induced by the bark beetle infestation. In 2016, mean annual Hg concentration in bulk precipitation at Plešné lake reached 3.0 ng/L and bulk Hg deposition flux amounted at 4.6 µg/m2. The most important pathway of Hg deposition to the forest ecosystems has been litterfall. The highest Hg concentrations in litterfall material at PL were found in lichens 205 µg/kg, mixture of unidentifiable organic debris 159 µg/kg and bark 123 µg/kg. Litterfall spruce needles averaged at 56 µg/kg, only. Removal of spruce due to bark beetle infestation caused decrease of litterfall Hg fluxes. Recent litterfall fluxes in the unimpacted stands reached 55.8 µg/m2, while in the impacted dead stands they amounted 23.0 µg/m2, only. The qualitative composition of the litterfall in the infested stands was typical with absence of needles and prevalence of twigs and bark. To assess changes in Hg distribution within the soil profile due to forest dieback the soil data from year 1999 were compared with 2015 data. The mean Hg concentrations in the O horizons decreased from 424 to 311 µg/kg between years 1999 and 2015, and in A horizons the situation was reversed and an increase from 353 to 501 µg/kg occurred. The means of Hg concentration in mineral soil remained relatively similar at 145 and 121 µg/kg. Increased Hg concentrations in A horizons were concurrent with increased organic C concentrations from 24.5% in 1999 to 39.9% in 2015. Ratio Hg/C in the A horizon remained rather comparable (1.27 and 1.47). In O horizons Hg/C ratio decreased from 0.9 to 0.5 comparing 1999 and 2015 due to changes in litterfall composition and total deposition due to canopy absence since 2005. Tributaries and lake water Hg concentrations were assessed to estimate the fluxes of Hg within lake catchment. PL lake water contained on average 4.4 ng/L of Hg and 8.2 mg/L of DOC. Mean annual Hg concentration in four lake tributaries ranged from 2.0 to 16.5 ng/L. The differences in Hg concentrations among individual streams were driven by DOC concentrations ranging from 2.1 to 21.2 mg/L. The differences between the Hg and DOC concentrations tributaries result from differences in hydrology of the individual sub-catchments. The financial support was provided by the Czech Science Foundation project No. GA16-14762S.
Sediment accumulation rates and high-resolution stratigraphy of recent fluvial suspension deposits in various fluvial settings, Morava River catchment area, Czech Republic

NASA Astrophysics Data System (ADS)

Sedláček, Jan; Bábek, Ondřej; Kielar, Ondřej

2016-02-01

We present a comprehensive study concerning sedimentary processes in fluvial sediment traps within the Morava River catchment area (Czech Republic) involving three dammed reservoirs, four meanders and oxbow lakes, and several natural floodplain sites. The objective of the study was to determine sediment accumulation rates (SAR), estimate erosion rates, calculating these using a combination of the 137Cs method and historical data. Another purpose of this study was to provide insight into changing erosion and accumulation rates over the last century. Extensive water course modifications were carried out in the Morava River catchment area during the twentieth century, which likely affected sedimentation rates along the river course. Other multiproxy stratigraphic methods (X-ray densitometry, magnetic susceptibility, and visible-light reflectance spectrometry) were applied to obtain additional information about sediment infill. Sediment stratigraphy revealed distinct distal-to-proximal patterns, especially in reservoirs. Granulometrically, silts and sandy silts prevailed in sediments. Oxbow lakes and meanders contained larger amounts of clay and organic matter, which is the main difference between them and reservoirs. Pronounced 137Cs peaks were recorded in all studied cores (maximum 377 Bq·kg- 1), thus indicating Chernobyl fallout from 1986 or older events. Calculated sediment accumulation rates were lowest in distal parts of reservoirs (0.13-0.58 cm/y) and floodplains (0.45-0.88 cm/y), moderately high rates were found in proximal parts of reservoirs and oxbow lakes (2.27-4.4 cm/y), and the highest rates in some oxbow lakes located near the river (6-8 cm/y). The frequency of the inundation still can be high in some natural areas as in the Litovelské Pomoraví protected area, whereas the decreasing frequency of the inundation in other modified parts can contribute to a lower sedimentation rate. The local effects such as difference between SARs in oxbow lakes and reservoirs, different grain size distribution in both systems, and high variability in thickness of their proximal and distal parts play a crucial role in the analysis of regional accumulation rates. Local effects are much stronger than regional effects, such as rainfall and land use. Combined with the low resolution of time scales (usually only three datums are available: reservoir construction datum, 137Cs fallout event, and top of sediment), these effects may obscure the general trends of regionally increasing or decreasing net SARs, making the analysis of erosion rates from the sedimentary record an extremely difficult task.
Characteristics and causal factors of hysteresis in the hydrodynamics of a large floodplain system: Poyang Lake (China)

NASA Astrophysics Data System (ADS)

Zhang, X. L.; Zhang, Q.; Werner, A. D.; Tan, Z. Q.

2017-10-01

A previous modeling study of the lake-floodplain system of Poyang Lake (China) revealed complex hysteretic relationships between stage, storage volume and surface area. However, only hypothetical causal factors were presented, and the reasons for the occurrence of both clockwise and counterclockwise hysteretic functions were unclear. The current study aims to address this by exploring further Poyang Lake's hysteretic behavior, including consideration of stage-flow relationships. Remotely sensed imagery is used to validate the water surface areas produced by hydrodynamic modeling. Stage-area relationships obtained using the two methods are in strong agreement. The new results reveal a three-phase hydrological regime in stage-flow relationships, which assists in developing improved physical interpretation of hysteretic stage-area relationships for the lake-floodplain system. For stage-area relationships, clockwise hysteresis is the result of classic floodplain hysteretic processes (e.g., restricted drainage of the floodplain during recession), whereas counterclockwise hysteresis derives from the river hysteresis effect (i.e., caused by backwater effects). The river hysteresis effect is enhanced by the time lag between the peaks of catchment inflow and Yangtze discharge (i.e., the so-called Yangtze River blocking effect). The time lag also leads to clockwise hysteresis in the relationship between Yangtze River discharge and lake stage. Thus, factors leading to hysteresis in other rivers, lakes and floodplains act in combination within Poyang Lake to create spatial variability in hydrological hysteresis. These effects dominate at different times, in different parts of the lake, and during different phases of the lake's water level fluctuations, creating the unique hysteretic hydrological behavior of Poyang Lake.
Biomass burning and its relationship with water cycle dynamics of the Chari-Logone catchment of Lake Chad Basin

NASA Astrophysics Data System (ADS)

Black, F. W.; Lee, J.; Ellison, L.; Gupta, M.; Bolten, J. D.; Gatebe, C. K.; Ichoku, C. M.

2016-12-01

The cause of shrinkage of Lake Chad has been of great interest for issues of global warming and climate change. The present study investigates the effect of biomass burning on the water cycle dynamics of Lake Chad Basin in the Northern Sub-Saharan Africa. Burning activities increase from November to April when monsoonal precipitation is at its lowest and decreases dramatically from May to October when precipitation peaks. To circumvent weather station scarcity in the region, a variety of satellite products were used as input into a water balance model. The datasets include TRMM 3B31 for precipitation, SRTM for elevation, and MODIS: MOD11C3 for temperature, MOD12Q1 for land cover, and MOD14A for fire count. Non-satellite based data sources include soil maps from the Harmonized World Soil Database and wind speed from NOAA NCDC stations. The Chari-Logone catchment of the Lake Chad Basin was selected since it supplies over 90% of the water input to the Lake. Fire count data from MOD14A were integrated with land cover albedo changes to determine monthly potential evapotranspiration (PET) using a Penman equation. The resolution of the model is 2 km x 2 km which allows for delineation of physical features such as lakes and other water bodies. Fire counts, also at a resolution of 2 km x 2 km, vary dramatically depending on the season. A separate land cover dataset was created to account for the effect of burning of different vegetative land types, which affects vegetative area, bare area, leaf area index, vegetation height, Manning coefficient, and aerodynamic resistance. Two water balance simulations, one considering burning and one without, were compared from the years 2005 to 2010. Results indicate biomass burning contribute to an increase in average monthly runoff and a decrease in groundwater recharge. Actual evapotranspiration shows variation depending on the month.
Rock magnetic properties of sediments from Lake Sanabria and its catchment (NW Spain): paleoenvironmental implications

NASA Astrophysics Data System (ADS)

Larrasoaña, J. C.; Borruel, V.; Gómez-Paccard, M.; Rico, M.; Valero-Garces, B.; Moreno-Caballud, A.; Soto, R.

2013-12-01

Lake Sanabria is located in the NW Spanish mountains at 1000 m a.s.l., and constitutes the largest lake of glacial origin in the Iberian Peninsula. Here we present an environmental magnetic study of a Late Pleistocene-Holocene sediment core from Lake Sanabria and from different lithologies that crop out in its catchment, which includes Paleozoic plutonic, metamorphic and vulcanosedimentary rocks, and Quaternary deposits of glacial origin. This study was designed to complement sedimentologic and geochemical studies aimed at unraveling the climatic evolution of the NW Iberian Peninsula during the last deglaciation. Our results indicate that magnetite and pyrrhotite dominate the magnetic assemblage of both the sediments from the lower half of the studied sequence (25.6 - 13 cal kyr BP) deposited in a proglacial environment, and the Paleozoic rocks that make up most of the catchment of the lake. The occurrence of these minerals both in the catchment rocks and in the lake sediments indicates that sedimentation was then driven by the erosion of a glacial flour, which suffered minimal chemical transformation in response to a rapid and short routing to the lake. Sediments from the upper half of the studied sequence, accumulated after 12.4 cal kyr BP in a fluviolacustrine environment, contain magnetite and greigite. This points to a prominent role of post-depositional reductive dissolution, driven by a sharp increase in the accumulation of organic matter into the lake and the creation of anoxic conditions in the sediments, in shaping the magnetic assemblage of Holocene sediments. Pyrrhotite is stable under reducing conditions as opposed to magnetite, which is unstable. We therefore interpret that previous pedogenic processes occurred in the then deglaciated catchment of the lake were responsible for the oxidation of pyrrhotite and authigenic formation of magnetite, which survived subsequent reductive diagenesis given its initial larger concentrations. This interpretation is supported by the magnetic properties of Quaternary till sediments, which in some cases retain their original magnetic assemblage (magnetite and pyrrhotite) and in other cases include larger concentrations of magnetite. The Holocene sequence includes some discrete layers with a magnetic signature identical to that of the glacial flour. These layers are interpreted as being deposited during extreme runoff events that eroded Quaternary tills. The sharp change in magnetic properties observed in the lake sediments between 13 and 12.4 kyr BP supports the rapid deglaciation of the catchment of Lake Sanabria inferred in previous studies on the basis of sedimentological, geochemical and geomorphological data.
Modeling the Hydrological Regime of Turkana Lake (Kenya, Ethiopia) by Combining Spatially Distributed Hydrological Modeling and Remote Sensing Datasets

NASA Astrophysics Data System (ADS)

Anghileri, D.; Kaelin, A.; Peleg, N.; Fatichi, S.; Molnar, P.; Roques, C.; Longuevergne, L.; Burlando, P.

2017-12-01

Hydrological modeling in poorly gauged basins can benefit from the use of remote sensing datasets although there are challenges associated with the mismatch in spatial and temporal scales between catchment scale hydrological models and remote sensing products. We model the hydrological processes and long-term water budget of the Lake Turkana catchment, a transboundary basin between Kenya and Ethiopia, by integrating several remote sensing products into a spatially distributed and physically explicit model, Topkapi-ETH. Lake Turkana is the world largest desert lake draining a catchment of 145'500 km2. It has three main contributing rivers: the Omo river, which contributes most of the annual lake inflow, the Turkwel river, and the Kerio rivers, which contribute the remaining part. The lake levels have shown great variations in the last decades due to long-term climate fluctuations and the regulation of three reservoirs, Gibe I, II, and III, which significantly alter the hydrological seasonality. Another large reservoir is planned and may be built in the next decade, generating concerns about the fate of Lake Turkana in the long run because of this additional anthropogenic pressure and increasing evaporation driven by climate change. We consider different remote sensing datasets, i.e., TRMM-V7 for precipitation, MERRA-2 for temperature, as inputs to the spatially distributed hydrological model. We validate the simulation results with other remote sensing datasets, i.e., GRACE for total water storage anomalies, GLDAS-NOAH for soil moisture, ERA-Interim/Land for surface runoff, and TOPEX/Poseidon for satellite altimetry data. Results highlight how different remote sensing products can be integrated into a hydrological modeling framework accounting for their relative uncertainties. We also carried out simulations with the artificial reservoirs planned in the north part of the catchment and without any reservoirs, to assess their impacts on the catchment hydrological regime and the Lake Turkana level variability.
The evaluation of water hyacinth (Eichhornia crassiper) control program in Rawapening Lake, Central Java Indonesia

NASA Astrophysics Data System (ADS)

Hidayati, N.; Soeprobowati, T. R.; Helmi, M.

2018-03-01

The existence of water hyacinths and other aquatic plants have been a major concern in Rawapening Lake for many years. Nutrient input from water catchment area and fish feed residues suspected to leads eutrophication, a condition that induces uncontrolled growth of aquatic plants. In dry season, aquatic plants cover almost 70% of lake area. This problem should be handled properly due to wide range of lake function such as water resources, fish farming, power plants, flood control, irrigation and many other important things. In 2011, Rawapening Lake was appointed as pilot project of Save Indonesian Lake Movement: the Indonesian movement for lakes ecosystem conservation and rehabilitation. This project consists of 6 super priority programs and 11 priority programs. This paper will evaluate the first super priority program which aims to control water hyacinth bloom. Result show that the three indicators in water hyacinth control program was not achieved. The coverage area of Water hyacinth was not reduced, tend to increase during period 2012 to 2016. We suggesting better coordination should be performed in order to avoid policies misinterpretation and to clarify the authority from each institution. We also give a support to the establishment of lake zonation plan and keep using all the three methods of cleaning water hyacinth with a maximum population remained at 20%.
Funnel Beaker weather (6200-4900 cal BP) - reconstructed from the palaeolimnological record of synchronously deposited varves in northern Germany

NASA Astrophysics Data System (ADS)

Dreibrodt, Stefan; Zahrer, Jürgen; Brauer, Achim

2013-04-01

Depositional patterns of synchronously deposited varves of Lake Belauer See and Lake Poggensee (northern Germany) were studied on thin sections under the microscope comparatively. Events and trends that occurred synchronously in the lake systems were detected and interpret as limnologic responses to supra-regional extrinsic (climate) drivers. The different thresholds of the compared lake systems implied by different lake size were utilized to infer about weather conditions. For Lake Belauer See microfacies types of sub-recent varves were proved to reflect responses of certain meteorological conditions (e.g. severity of winters). A short weather anomaly at around 5950 cal BP was detected. Cold summers of about 40 successive years (probably with sudden frost events) lead to breaks of the thermal summer stratification and the associated carbonate precipitation. Instead renewed blooms of planctic diatoms occurred. The subsequent interval of the Funnel Beaker Culture seems to have experienced a period with favorable wea¬ther conditions, with warm summers and not extra-ordinary severe winters. Between ca. 5400 and 5340 cal BP an interval with pronounced warm winters is indicated. The favorable weather conditions termina¬ted abruptly at around 5275 cal BP when the weather (in particular summers) became colder. The comparison of the sediment sequences also provides evidence for the asynchronic onset of anthropogenic activity in the catchment areas of the lakes. A significant increase of minerogenic matter (quartz grains) indication soil erosion in the lake catchment started at ca. 3850 cal BC in Lake Poggensee, and at ca. 3500 cal BC in Lake Belau. Cycles of minerogenic input have been detected with duration of 20-25 years. Whether these cycles could represent slash and burn cycles has to be studied further.
Glacier lake outburst floods caused by glacier shrinkage: case study of Ala-Archa valley, Kyrgyz Ala Too, northern Tian Shan, Kyrgyzstan

NASA Astrophysics Data System (ADS)

Petrakov, D.; Erochin, S. A.; Harbor, J.; Ivanov, M.; Rogozhina, I.; Stroeven, A. P.; Usubaliev, R.

2012-12-01

Changes in glacier extent and runoff in Central Asia increase socio-economic stress and may result in political conflict between donors of freshwater (Kyrgyzstan, Tajikistan) and recipients of freshwater (Uzbekistan, China). Glaciers in the Pamir and Tian Shan regions have experienced an unprecedented downwasting due to regional climate changes over the past decades. This is because air temperature increases are in some areas accompanied by a decrease in precipitation. Such conditions have already resulted in a reduction of glacier runoff, especially in the northern and western Tian Shan, and an increase of the number and area of glacial lakes in Kyrgyzstan. Even though glacial lakes in the mountains are in general relatively small and located far from densely populated areas, their outbursts often produce destructive debris flows. Such debris flows are especially common in Kyrgyzstan because of its steep river channels and abundance of Holocene and Quaternary glacier deposits that can be remobilized. The glacial lake outburst flood (GLOF) in the Shakhimardan river catchment in 1999, for example, resulted in 100 fatalities in Uzbekistan, and the GLOF from the Zyndan glacial lake led to substantial economic losses in 2009. According to the latest inventory, there are more than 350 glacial lakes in Kyrgyzstan of which about 70 occur in the Kyrgyz Ala Too. The Ala-Archa valley is among the most important glacierized catchments in Kyrgyzstan. Despite the presence of a relatively small glacier-covered area of 36 km2, the Ala-Archa river is of critical importance to the Bishkek area, its agriculture, and its population which currently exceeds one million. GLOFs are therefore a threat to both numerous settlements of touristic value in the Ala-Archa headwaters and to Bishkek. The Teztor lake in the Adygene catchment of the Ala-Archa river system experienced an outburst during 1988 and 2005. On the early morning of July 31, 2012, this lake began draining through a dam composed of stagnant ice and debris. With the water discharge being merely a few m3/s, the GLOF transformed into a debris flow beyond a steep front of rock glacier, which is within 150 m downstream of the lake. After rushing through the ca. 7 km-long Adygene valley, the debris flow formed a fan in the Ala-Archa valley and transformed into a flood. The flood wave reached Bishkek located more than 40 km downstream. This led to a panic amongst local dwellers and Bishkek residents. The maximum discharge of the debris flow in the lower part of the Adygene valley was assessed as 300 m3/s and the discharge of the flood in Bishkek as 35 m3/s. The latter exceeds the standard discharge of the Ala-Archa river substantially. Although no fatalities resulted from this event, economic losses as a consequence of a destroyed mineral water factory could possibly amount to USD 200000, which is a substantial sum by Kyrgyz standards. Because of the prior history, it is expected that GLOFs from the Teztor valley will recur in the upcoming years. We conclude that installation of an early warning system in lower Adygene valley is needed to prevent further damage in the study area.
Effects of acidic deposition on in-lake phosphorus availability: a lesson from lakes recovering from acidification.

PubMed

Kopáček, Jiří; Hejzlar, Josef; Kaňa, Jiří; Norton, Stephen A; Stuchlík, Evžen

2015-03-03

Lake water concentrations of phosphorus (P) recently increased in some mountain areas due to elevated atmospheric input of P rich dust. We show that increasing P concentrations also occur during stable atmospheric P inputs in central European alpine lakes recovering from atmospheric acidification. The elevated P availability in the lakes results from (1) increasing terrestrial export of P accompanying elevated leaching of dissolved organic carbon and decreasing phosphate-adsorption ability of soils due to their increasing pH, and (2) decreasing in-lake P immobilization by aluminum (Al) hydroxide due to decreasing leaching of ionic Al from the recovering soils. The P availability in the recovering lakes is modified by the extent of soil acidification, soil composition, and proportion of till and meadow soils in the catchment. These mechanisms explain several conflicting observations of the acid rain effects on surface water P concentrations.

Regional estimation of response routine parameters

NASA Astrophysics Data System (ADS)

Tøfte, Lena S.

2015-04-01

Reducing the number of calibration parameters is of a considerable advantage when area distributed hydrological models are to be calibrated, both due to equifinality and over-parameterization of the model in general, and for making the calibration process more efficient. A simple non-threshold response model for drainage in natural catchments based on among others Kirchner's article in WRR 2009 is implemented in the gridded hydrological model in the ENKI framework. This response model takes only the hydrogram into account; it has one state and two parameters, and is adapted to catchments that are dominated by terrain drainage. In former analyses of natural discharge series from a large number of catchments in different regions of Norway, we found that these response model parameters can be calculated from some known catchment characteristics, as catchment area and lake percentage, found in maps or data bases, meaning that the parameters can easily be found also for ungauged catchments. In the presented work from the EU project COMPLEX a large region in Mid-Norway containing 27 simulated catchments of different sizes and characteristics is calibrated. Results from two different calibration strategies are compared: 1) removing the response parameters from the calibration by calculating them in advance, based on the results from our former studies, and 2) including the response parameters in the calibration, both as maps with different values for each catchment, and as a constant number for the total region. The resulting simulation performances are compared and discussed.
Is the destabilisation of lake peipsi ecosystem caused by increased phosphorus loading or decreased nitrogen loading?

PubMed

Nõges, T; Laugaste, R; Loigu, E; Nedogarko, I; Skakalski, B; Nõges, P

2005-01-01

Lake Peipsi (3555 km2, mean depth 7.1 m) located on the border of Estonia and Russia is the largest transboundary lake in Europe. L. Peipsi consists of three parts. The shared largest northern part L. Peipsi s.s. (2611 km2, 8.3 m) and the southern L. Pihkva (708 km2, 3.8 m) which belongs mainly to Russia are connected by the river-shaped L. Lämmijärv (236 km2, 2.5 m). The catchment area (44,245 km2 without lake area) is shared between Estonia (33.3%), Russia (58.6%) and Latvia (8%). Intensive eutrophication of L. Peipsi started in the 1970s. The biomass of N2-fixing cyanobacteria was low at heavy nutrient loading in the 1980s. After the collapse of soviet-type agriculture in the early 1990s, the loading of nitrogen sharply decreased. A certain improvement of L. Peipsi s.s. was noticed at the beginning of the 1990s together with the temporary reduction of phosphorus loading from Estonian catchment while in recent years a destabilisation of the ecosystem has been observed. This deterioration has been expressed mainly as intensive blue-green blooms and fish-kills in summer. Reappearance of blooms has been explained by the decrease in N/P loading ratio due to reduced N discharge while in some periods increased phosphorus loading could have supported this trend.
Water balance of a lake with floodplain buffering: Lake Tana, Blue Nile Basin, Ethiopia

NASA Astrophysics Data System (ADS)

Dessie, Mekete; Verhoest, Niko E. C.; Pauwels, Valentijn R. N.; Adgo, Enyew; Deckers, Jozef; Poesen, Jean; Nyssen, Jan

2015-03-01

Lakes are very important components of the earth's hydrological cycle, providing a variety of services for humans and ecosystem functioning. For a sustainable use of lakes, a substantial body of knowledge on their water balance is vital. We present here a detailed daily water balance analysis for Lake Tana, the largest lake in Ethiopia and the source of the Blue Nile. Rainfall on the lake is determined by Thiessen polygon procedure, open water evaporation is estimated by the Penman-combination equation and observed inflows for the gauged catchments as well as outflow data at the two lake outlets are directly used. Runoff from ungauged catchments is estimated using a simple rainfall-runoff model and runoff coefficients. Hillslope catchments and floodplains are treated separately, which makes this study unique compared to previous water balance studies. Impact of the floodplain on the lake water balance is analyzed by conducting scenario-based studies. We found an average yearly abstraction of 420 × 106 m3 or 6% of river inflows to the lake by the floodplain in 2012 and 2013. Nearly 60% of the inflow to the lake is from the Gilgel Abay River. Simulated lake levels compare well with the observed lake levels (R2 = 0.95) and the water balance can be closed with a closure error of 82 mm/year (3.5% of the total lake inflow). This study demonstrates the importance of floodplains and their influence on the water balance of the lake and the need of incorporating the effects of floodplains and water abstraction for irrigation to improve predictions.
Introduction to paleoenvironments of Bear Lake, Utah and Idaho, and its catchment

USGS Publications Warehouse

Rosenbaum, Joseph G.; Kaufman, Darrell S.

2009-01-01

In 1996 a group led by the late Kerry Kelts (University of Minnesota) and Robert Thompson (U.S. Geological Survey) acquired three piston cores (BL96-1, -2, and -3) from Bear Lake. The coring arose from their recognition of Bear Lake as a potential repository of long records of paleoenvironmental change. They recognized that the lake is located in an area that is sensitive to changes in regional climate patterns (Dean et al., this volume), that the lake basin is long lived (see Colman, 2006; Kaufman et al., this volume), and that, unlike many lakes in the Great Basin, Bear Lake was never dry during warm dry periods. Bear Lake lies in the northeastern Great Basin to the northeast of Great Salt Lake, just south of the Snake River drainage, and a short distance west of the Green River drainage that makes up part of the Upper Colorado River Basin (Fig. 1). Similarity among the historic Bear Lake and Great Salt Lake hydrographs and flows on the Green River indicates that the hydrology of Bear Lake reflects regional precipitation (Fig. 2). Therefore, paleorecords from Bear Lake are important to understanding past climate for a large region, including the Upper Colorado River Basin, the source of much of the water for the southwestern United States. Initially, paleoenvironmental studies of Bear Lake sediments focused on cores BL96-1, -2, and -3. Additional coring was conducted to elucidate the spatial distribution of sedimentary units and to extend the record back in time. The study was also expanded to include extensive study of the catchment, including the properties of catchment materials and the processes that could potentially affect the delivery of catchment materials to the lake. Cores BL96-1, -2, and -3 were taken with a Kullenburg piston corer along an east–west profile in roughly 50, 40, and 30 m of water, respectively (Table 1, Fig. 3). These three cores, each taken as a single 4- to 5-m-long segment, provide a nearly complete composite section from ca. 26 cal ka to the late Holocene. In 1998 a number of short gravity cores were taken from the uppermost water-rich sediments that were not sampled by the 1996 cores. During 2000, cores were taken with a percussion piston corer (manufactured by UWITEC) at three locations in and around Mud Lake and at two locations in the northern end of Bear Lake (Fig. 3). Cores acquired with the percussion corer comprise as many as three overlapping segments up to 2 m in length. In 2002, additional percussion piston cores and associated gravity cores of the uppermost sediments were acquired from five sites in the northern half of the lake. In conjunction with two of the cores collected in 2000, these cores form a north–south profile along a seismic line and span water depths from less than 10 m to ~40 m. Data from this profile provide much of the evidence for lake-level variations (Smoot and Rosenbaum, this volume). Finally, during 2000, two long cores, BL00-1D and -1E (collectively referred to here simply as BL00-1), were taken at a site near the depocenter during testing of the GLAD800 coring platform (Fig. 4; Dean et al., 2002). These cores provide a record back to ca. 220 ka.
Set-up of a decision support system to support sustainable development of the Laguna de Bay, Philippines.

PubMed

Nauta, Tjitte A; Bongco, Alicia E; Santos-Borja, Adelina C

2003-01-01

Over recent decades, population expansion, deforestation, land conversion, urbanisation, intense fisheries and industrialisation have produced massive changes in the Laguna de Bay catchment, Philippines. The resulting problems include rapid siltation of the lake, eutrophication, inputs of toxics, flooding problems and loss of biodiversity. Rational and systematic resolution of conflicting water use and water allocation interests is now urgently needed in order to ensure sustainable use of the water resources. With respect to the competing and conflicting pressures on the water resources, the Laguna Lake Development Authority (LLDA) needs to achieve comprehensive management and development of the area. In view of these problems and needs, the Government of the Netherlands was funding a two-year project entitled 'Sustainable Development of the Laguna de Bay Environment'.A comprehensive tool has been developed to support decision-making at catchment level. This consists of an ArcView GIS-database linked to a state-of-the-art modelling suite, including hydrological and waste load models for the catchment area and a three-dimensional hydrodynamic and water quality model (Delft3D) linked to a habitat evaluation module for the lake. In addition, MS Office based tools to support a stakeholder analysis and financial and economic assessments have been developed. The project also focused on technical studies relating to dredging, drinking water supply and infrastructure works. These aimed to produce technically and economically feasible solutions to water quantity and quality problems. The paper also presents the findings of a study on the development of polder islands in the Laguna de Bay, addressing the water quantity and quality problems and focusing on the application of the decision support system.
Assessment of lake sensitivity to acidic deposition in national parks of the Rocky Mountains

USGS Publications Warehouse

Nanus, L.; Williams, M.W.; Campbell, D.H.; Tonnessen, K.A.; Blett, T.; Clow, D.W.

2009-01-01

The sensitivity of high-elevation lakes to acidic deposition was evaluated in five national parks of the Rocky Mountains based on statistical relations between lake acid-neutralizing capacity concentrations and basin characteristics. Acid-neutralizing capacity (ANC) of 151 lakes sampled during synoptic surveys and basin-characteristic information derived from geographic information system (GIS) data sets were used to calibrate the statistical models. The explanatory basin variables that were considered included topographic parameters, bedrock type, and vegetation type. A logistic regression model was developed, and modeling results were cross-validated through lake sampling during fall 2004 at 58 lakes. The model was applied to lake basins greater than 1 ha in area in Glacier National Park (n = 244 lakes), Grand Teton National Park (n = 106 lakes), Great Sand Dunes National Park and Preserve (n = 11 lakes), Rocky Mountain National Park (n = 114 lakes), and Yellowstone National Park (n = 294 lakes). Lakes that had a high probability of having an ANC concentration 3000 m, with 80% of the catchment bedrock having low buffering capacity. The modeling results indicate that the most sensitive lakes are located in Rocky Mountain National Park and Grand Teton National Park. This technique for evaluating the lake sensitivity to acidic deposition is useful for designing long-term monitoring plans and is potentially transferable to other remote mountain areas of the United States and the world.
Large mass movements related to deglaciation effects in southern Peru (Cusco)

NASA Astrophysics Data System (ADS)

Giráldez, Claudia; Choquevilca, Walter; Fernández, Felipe; Frey, Holger; García, Javier; Haeberli, Wilfried; Huggel, Christian; Ludena, Sebastián; Rohrer, Mario; Suarez, Wilson

2013-04-01

The Andes of Peru are among the regions most severely affected by glacier and high-mountain hazards over the past 100 years. Large-scale disasters with thousands of people killed are on record, including ice/rock avalanches, debris flows, and glacier lake outburst floods (GLOF's). Effects of climate change such as glacier retreat and formation of glacier lakes have been one of the drivers of hazards in the past. Now, there is an increasing concern about the destabilizing effect that recent and further warming has a on perennially frozen bedrock and on steep glaciers in the steep flanks of high-mountain peaks, with potentially severe consequences to ice/rock avalanches, which may impact existing and new lakes, producing far-reaching outburst floods. Risks are also changing due to the socio-economic development in the Andean region and need to be considered using integrative approaches. Most research so far has concentrated on the Cordillera Blanca region where the most devastating disasters occurred during the 20th century. Very little is known about glacier and high-mountain hazards in the southern Peruvian Cordilleras of Cusco although some of the largest debris flows worldwide affected this region in recent years. In fact, very little is known about the nature, origin and exact dimensions of mass movements in this area, and long-term climatic records are neither available. Here we analyze these recent events in the Santa Teresa region based on field work, satellite images, available meteorological data, and numerical modeling of mass movements. These studies are part of a larger effort towards an integrative risk management. Most of the mass movements that caused disasters have their origin in glaciated catchments draining towards Santa Teresa with catchment sizes between about 100 and 300 km2, and glacier areas of 6 to 16 km2 per catchment. It is known that the enormous 1998 debris flow (ca. 25 million m3) that destroyed the Machu Picchu hydropower plant originated from a big landslide in deglaciated terrain which mobilized large sediment reservoirs after a period of intense rainfall. For other events on record, ongoing fieldwork studies and first modeling results are carried out to analyze their origin, trigger and characteristics. Satellite based studies on glacier lakes revealed a significant number of potentially hazardous lakes in the catchments that, together with big landslides, need to be integrated in a comprehensive risk management system which takes into account the high dynamics of such high-mountain environment under climate change.
Monitoring mountain lakes in a changing Alpine cryosphere: the Lago Nero project (Ticino, Switzerland)

NASA Astrophysics Data System (ADS)

Scapozza, Cristian; Bruder, Andreas; Domenici, Mattia; Lepori, Fabio; Pera, Sebastian; Pozzoni, Maurizio; Rioggi, Stefano; Colombo, Luca

2017-04-01

Mountain lakes and their catchments of the Alpine cryosphere are facing global pressures including climate warming and deposition of atmospheric pollutants. Due to their remoteness, often low buffer capacities and sensitive biotic communities, alpine lake catchments are particularly well suited as sentinels of environmental change. Lago Nero is the object of an intensive survey, aimed at developing predictive models of catchment-wide ecosystem responses to environmental change (Bruder et al. 2016). Lago Nero is located at the head of Val Bavona (Canton Ticino, southern Switzerland), in a southwest-facing catchment, with altitude ranging from 2385 to 2842 m asl. The substrate is dominated by gneissic bedrock with patches of grassy vegetation and shallow soils. The catchment is snow-covered approximately from November to May. For a similar period, the lake is ice-covered. Lago Nero is an oligotrophic, soft-water lake with a surface of approximatively 13 ha and a maximal depth of 73 m. According to the regional model of potential permafrost distribution in the southern Swiss Alps (Scapozza & Mari 2010), the presence of discontinuous permafrost is probable in almost the entire surface of the catchment covered by loose debris. A direct evidence of permafrost occurrence is the presence of a small active/inactive rock glacier in the south-eastern part of the catchment (front altitude: 2560 m asl). Monitoring of the site began in summer 2014, with an initial phase aimed at developing and testing methodologies and at evaluating the suitability of the catchment and the feasibility of the monitoring program. The intensive survey at Lago Nero measures a wide array of ecosystem responses, including runoff quantity and chemistry, catchment soil temperature (also on the rock glacier) and composition of terrestrial vegetation. Sampling frequency depends on the parameter measured, varying from nearly continuous (e.g. runoff and temperature) to five-year intervals (e.g. soil and vegetation). First results suggest that Lago Nero is particularly sensitive to changes in the cryosphere, particularly concerning thickness of snow cover, snowmelt date and duration, and length of ice-free period of the lake surface. Probable storage of ground ice during the 1966-1985 period (deduced from the nearby Basòdino Glacier) and its significant melting in the last decades may explain the high amounts of sulphur measured in the outflow of the rock glacier. High levels of sulphur are likely to have ecological effects on the sensitive biota of the Lago Nero catchment, for instance by retarding the recovery from past acidification. REFERENCES Bruder A., Lepori F., Pozzoni M., Pera S., Scapozza C., Rioggi S., Domenici M. & Colombo L. (2016). Lago Nero - a new site to assess the effects of environmental change on high-alpine lakes and their catchments. In: S. Kleemola & M. Forsius (eds.), 25th Annual Report 2016. Convention on Long-range transboundary air pollution. Reports of the Finnish Environments Institute 29: 52-56. Scapozza C. & Mari S. (2010). Catasto, caratteristiche e dinamica dei rock glacier delle Alpi Ticinesi. Bollettino della Società ticinese di Scienze naturali 98: 15-29. [http://repository.supsi.ch/2152/
Seabird guano is an efficient conveyer of persistent organic pollutants (POPs) to Arctic lake ecosystems.

PubMed

Evenset, A; Carroll, J; Christensen, G N; Kallenborn, R; Gregor, D; Gabrielsen, G W

2007-02-15

Migratory seabirds have been linked to localized "hotspots" of contamination in remote Arctic lakes. One of these lakes is Lake Ellasjøen on Bjørnøya in the Barents Sea. Here we provide quantitative evidence demonstrating that even relatively small populations of certain seabird species can lead to major impacts for ecosystems. In the present example, seabird guano accounts for approximately 14% of the contaminant inventory of the Lake Ellasjøen catchment area, approximately 80% of the contaminant inventory of the lake itself, and is approximately thirty times more efficient as a contaminant transport pathway compared to atmospheric long-range transport. We have further shown that this biological transport mechanism is an important contaminant exposure route for ecosystems, responsible for POPs levels in freshwater fish that are an order of magnitude higher than those in Arctic top predators. Given the worldwide presence of seabird colonies in coastal marine areas where resources are also harvested by humans, this biological transport pathway may be a greater source of dietary contamination than is currently recognized with consequent risks for human health.
Glacialmorphological reconstruction of glacier advances and glacial lake outburst floods at the Cachapoal glacier in the Dry Central Andes of Chile (34°S)

NASA Astrophysics Data System (ADS)

Iturrizaga, Lasafam; Charrier, Reynaldo

2013-04-01

Throughout the Andes Mountain range of South America a general trend of glacier shrinkage has taken place in the last century. Only a few glaciers have shown a rather non-continuous trend of glacier retreat and temporally advanced or even surged during the mid-19th to 20th century. One of the earliest assumed glacier surges has occurred in the upper Cachapoal catchment area at the homonymous glacier. In climatic respect the Cachapoal glacier is located in the transition zone from the most southern part of the Dry Central Andes of Chile to the more humid zone of the Wet Andes. The region is affected mainly by winter precipitation deriving from the Westerlies. The debris-covered, 12 km-long Cachapoal glacier represents one of the largest valley glaciers in the Central Andes. It is an avalanche-fed glacier with an almost 1500 m-high head wall in its upper catchment area flowing down from Picos del Barroso (5180 m) and terminates at an elevation of 2630 m a.s.l. with a bifurcated glacier tongue. A large moraine complex, almost 2 km in length and 500 m in width, separates the two glacier lobes. During times of advanced glacier tongue positions the Ríos Molina and Cachapoal may be have blocked independently at two distinct localities which are situated about 2300 m apart from each other. A blockage with temporal lake formation has occurred at least in the years 1848, 1955 and 1981 (cf. Plagemann 1887, Peña 1981), from which the rupture of the earliest glacier barrier has been the most devastating. This event is locally reminded as "la gran avenida en seco" in the historical record. Geomorphological evidence of the past historical and modern glacier expansions is given in the proglacial area by a fresh dead-ice hummocky topography and glacial trimlines at the valley flanks. More down valley broad outwash plains and boulder clusters indicate past high energy floods produced by glacier lake outbursts. Regarding the small size of the catchment area of the Río Molina, which has been the main source of the former impounded glacial lakes, the present risk of potential glacier lake outbursts might be considered as comparatively low. The project is financed by the Universidad de Andrés Bello (Santiago de Chile) as well as by the Alexander von Humboldt Foundation.
A Buoy for Continuous Monitoring of Suspended Sediment Dynamics

PubMed Central

Mueller, Philip; Thoss, Heiko; Kaempf, Lucas; Güntner, Andreas

2013-01-01

Knowledge of Suspended Sediments Dynamics (SSD) across spatial scales is relevant for several fields of hydrology, such as eco-hydrological processes, the operation of hydrotechnical facilities and research on varved lake sediments as geoarchives. Understanding the connectivity of sediment flux between source areas in a catchment and sink areas in lakes or reservoirs is of primary importance to these fields. Lacustrine sediments may serve as a valuable expansion of instrumental hydrological records for flood frequencies and magnitudes, but depositional processes and detrital layer formation in lakes are not yet fully understood. This study presents a novel buoy system designed to continuously measure suspended sediment concentration and relevant boundary conditions at a high spatial and temporal resolution in surface water bodies. The buoy sensors continuously record turbidity as an indirect measure of suspended sediment concentrations, water temperature and electrical conductivity at up to nine different water depths. Acoustic Doppler current meters and profilers measure current velocities along a vertical profile from the water surface to the lake bottom. Meteorological sensors capture the atmospheric boundary conditions as main drivers of lake dynamics. It is the high spatial resolution of multi-point turbidity measurements, the dual-sensor velocity measurements and the temporally synchronous recording of all sensors along the water column that sets the system apart from existing buoy systems. Buoy data collected during a 4-month field campaign in Lake Mondsee demonstrate the potential and effectiveness of the system in monitoring suspended sediment dynamics. Observations were related to stratification and mixing processes in the lake and increased turbidity close to a catchment outlet during flood events. The rugged buoy design assures continuous operation in terms of stability, energy management and sensor logging throughout the study period. We conclude that the buoy is a suitable tool for continuous monitoring of suspended sediment concentrations and general dynamics in fresh water bodies. PMID:24129017
Characterizing chromophoric dissolved organic matter in Lake Tianmuhu and its catchment basin using excitation-emission matrix fluorescence and parallel factor analysis.

PubMed

Zhang, Yunlin; Yin, Yan; Feng, Longqing; Zhu, Guangwei; Shi, Zhiqiang; Liu, Xiaohan; Zhang, Yuanzhi

2011-10-15

Chromophoric dissolved organic matter (CDOM) is an important optically active substance that transports nutrients, heavy metals, and other pollutants from terrestrial to aquatic systems and is used as a measure of water quality. To investigate how the source and composition of CDOM changes in both space and time, we used chemical, spectroscopic, and fluorescence analyses to characterize CDOM in Lake Tianmuhu (a drinking water source) and its catchment in China. Parallel factor analysis (PARAFAC) identified three individual fluorophore moieties that were attributed to humic-like and protein-like materials in 224 water samples collected between December 2008 and September 2009. The upstream rivers contained significantly higher concentrations of CDOM than did the lake water (a(350) of 4.27±2.51 and 2.32±0.59 m(-1), respectively), indicating that the rivers carried a substantial load of organic matter to the lake. Of the three main rivers that flow into Lake Tianmuhu, the Pingqiao River brought in the most CDOM from the catchment to the lake. CDOM absorption and the microbial and terrestrial humic-like components, but not the protein-like component, were significantly higher in the wet season than in other seasons, indicating that the frequency of rainfall and runoff could significantly impact the quantity and quality of CDOM collected from the catchment. The different relationships between the maximum fluorescence intensities of the three PARAFAC components, CDOM absorption, and chemical oxygen demand (COD) concentration in riverine and lake water indicated the difference in the composition of CDOM between Lake Tianmuhu and the rivers that feed it. This study demonstrates the utility of combining excitation-emission matrix fluorescence and PARAFAC to study CDOM dynamics in inland waters. Copyright © 2011 Elsevier Ltd. All rights reserved.
SWAT-CS: Revision and testing of SWAT for Canadian Shield catchments

NASA Astrophysics Data System (ADS)

Fu, Congsheng; James, April L.; Yao, Huaxia

2014-04-01

Canadian Shield catchments are under increasing pressure from various types of development (e.g., mining and increased cottagers) and changing climate. Within the southern part of the Canadian Shield, catchments are generally characterized by shallow forested soils with high infiltration rates and low bedrock infiltration, generating little overland flow, and macropore and subsurface flow are important streamflow generation processes. Large numbers of wetlands and lakes are also key physiographic features, and snow-processes are critical to catchment modeling in this climate. We have revised the existing, publicly available SWAT (version 2009.10.1 Beta 3) to create SWAT-CS, a version representing hydrological processes dominating Canadian Shield catchments, where forest extends over Precambrian Shield bedrock. Prior to this study, very few studies applying SWAT to Canadian Shield catchments exist (we have found three). We tested SWAT-CS using the Harp Lake catchment dataset, an Ontario Ministry of Environment research station located in south-central Ontario. Simulations were evaluated against 30 years of observational data, including streamflow from six headwater sub-catchments (0.1-1.9 km2), outflow from Harp Lake (5.4 km2) and five years of weekly snow water equivalent (SWE). The best Nash-Sutcliffe efficiency (NSE) results for daily streamflow calibration, daily streamflow validation, and SWE were 0.60, 0.65, and 0.87, respectively, for sub-catchment HP4 (with detailed land use and soil data). For this range of catchment scales, land cover and soil properties were found to be transferable across sub-catchments with similar physiographic features, namely streamflow from the remaining five sub-catchments could be modeled well using sub-catchment HP4 parameterization. The Harp Lake outflow was well modeled using the existing reservoir-based target release method, generating NSEs of 0.72 and 0.67 for calibration and verification periods respectively. With significant changes to the infiltration module (introducing macropore flow and reduced bedrock percolation), more than 90% of interflow was generated close to the soil-bedrock interface and the contribution of groundwater flow to total runoff was reduced to small amounts, consistent with hydrological process understanding in this terrain. These two changes also allowed for a positive linear relationship between NSE of SWE and Q, whereas prior to these changes there was a negative relationship. With these key revisions to the infiltration and bedrock percolations modules, it is concluded that SWAT-CS can reasonably capture key hydrological processes within Canadian Shield catchments. Further testing will examine water quality modeling and larger-scale applications.
Using groundwater age and hydrochemistry to understand sources and dynamics of nutrient contamination through the catchment into Lake Rotorua, New Zealand

NASA Astrophysics Data System (ADS)

Morgenstern, U.; Daughney, C. J.; Leonard, G.; Gordon, D.; Donath, F. M.; Reeves, R.

2015-02-01

The water quality of Lake Rotorua has steadily declined over the past 50 years despite mitigation efforts over recent decades. Delayed response of the groundwater discharges to historic land-use intensification 50 years ago was the reason suggested by early tritium measurements, which indicated large transit times through the groundwater system. We use the isotopic and chemistry signature of the groundwater for detailed understanding of the origin, fate, flow pathways, lag times and future loads of contaminants. A unique set of high-quality tritium data over more than four decades, encompassing the time when the tritium spike from nuclear weapons testing moved through the groundwater system, allows us to determine detailed age distribution parameters of the water discharging into Lake Rotorua. The Rotorua volcanic groundwater system is complicated due to the highly complex geology that has evolved through volcanic activity. Vertical and steeply inclined geological contacts preclude a simple flow model. The extent of the Lake Rotorua groundwater catchment is difficult to establish due to the deep water table in large areas, combined with inhomogeneous groundwater flow patterns. Hierarchical cluster analysis of the water chemistry parameters provided evidence of the recharge source of the large springs near the lake shore, with discharge from the Mamaku ignimbrite through lake sediment layers. Groundwater chemistry and age data show clearly the source of nutrients that cause lake eutrophication, nitrate from agricultural activities and phosphate from geologic sources. With a naturally high phosphate load reaching the lake continuously via all streams, the only effective way to limit algae blooms and improve lake water quality in such environments is by limiting the nitrate load. The groundwater in the Rotorua catchment, once it has passed through the soil zone, shows no further decrease in dissolved oxygen, indicating an absence of bioavailable electron donors along flow paths that could facilitate microbial denitrification reactions. Nitrate from land-use activities that leaches out of the root zone of agricultural land into the deeper part of the groundwater system must be expected to travel with the groundwater to the lake. The old age and the highly mixed nature of the water discharges imply a very slow and lagged response of the streams and the lake to anthropogenic contaminants in the catchment, such as nitrate. Using the age distribution as deduced from tritium time series data measured in the stream discharges into the lake allows prediction of future nutrient loads from historic land-use activities 50 years ago. For Hamurana Stream, the largest stream to Lake Rotorua, it takes more than a hundred years for the groundwater-dominated stream discharge to adjust to changes in land-use activities. About half of the currently discharging water is still pristine old water, and after this old water is completely displaced by water affected by land use, the nitrogen load of Hamurana Stream will approximately double. These timescales apply to activities that cause contamination, but also to remediation action.
Characteristics of the water and dissolved matter circulation in the young-glacial catchment of the Czechowskie lake (Tuchola Pinewood Forest, Poland)

NASA Astrophysics Data System (ADS)

Brykala, Dariusz; Gierszewski, Piotr; Kaszubski, Michal

2014-05-01

The studies on the conditions of the water and dissolved matter circulation in the young-glacial catchment of the Czechowskie lake (Tuchola Pinewood Forest) have been conducted since 2012. They are implemented on the basis of an organised network monitoring surface water and groundwater. An important aim of the study is to assess the impact of both modern and fossil lakes on the regime of the outflow and the transformation of the water chemical properties. A high stability of the first groundwater table was recorded. During the study period the range of the groundwater level ranged from 0.17 to 0.92 m. In comparison with the small fluctuations in the groundwater level within the sandy outwash areas, a relatively high instability was shown by the shallow waters of the lake terraces. The measurements of the discharge showed that its average value at the outflow from the Czechowskie lake is 30 dm3s-1. It almost equals the total amount of water flowing into the lake through watercourses. The average specific runoff from the basin of the Czechowskie lake was 3 dm3s-1km-2. The total water mineralisation expressed as the sum of the ions is in the range from 70 to 750 mg dm-3. Both surface water, i.e. the water in streams and lakes, and underground water from different depths represent the bicarbonate-calcium-sulphate type characteristic of the young- glacial environment. The results of hydrochemical mapping and the analysis of the ionic composition of the water showed large spatial variability of the physico-chemical properties of the tested waters and, at the same time, high stability of their ionic composition. At the present stage of the research it is possible to identify the water enrichment zones in salts, which are basins of paleolakes filled with the organic-carbonate sediment, and the zones of salt precipitation within the contemporary lakes. The situation described above creates a specific, cascade model of the transformation of chemical properties of water circulating in the catchment. The presented results are a contribution to the Virtual Institute of Integrated Climate and Landscape Evolution Analysis - ICLEA - of the Helmholtz Association.
Eutrophication of the Strzeszyńskie Lake: Sources, Consequences and Remedies

NASA Astrophysics Data System (ADS)

Zawadzki, Paweł; Murat-Błażejewska, Sadżide; Błażejewski, Ryszard

2016-06-01

The paper presents history and recent review of investigations on ecological status of the Strzeszyńskie Lake, located within borders of town Poznań. The lake is a popular rest place, also for bathing and angling, therefore its state concerns many institutions and inhabitants. Recently, a deterioration of its ecological state has been observed due to pollution from a tributary catchment (Row Złotnicki), lake's direct catchment, precipitation and fallen leaves. Phosphorus balance for an average year was estimated. A review of applied remedies was provided but an assessment of their effectiveness was unfeasible due to simultaneity and relatively short duration of their application.
Photochemical Reactivity of Dissolved Organic Matter in Boreal Lakes

NASA Astrophysics Data System (ADS)

Gu, Y.; Vuorio, K.; Tiirola, M.; Perämäki, S.; Vahatalo, A.

2016-12-01

Boreal lakes are rich in dissolved organic matter (DOM) that terrestrially derived from forest soil and wetland, yet little is known about potential for photochemical transformation of aquatic DOM in boreal lakes. Transformation of chromophoric dissolved organic matter (CDOM) can decrease water color and enhance microbial mineralization, affecting primary production and respiration, which both affect the CO2 balance of the lakes. We used laboratory solar radiation exposure experiments with lake water samples collected from 54 lakes located in Finland and Sweden, representing different catchment composition and watershed location to assess photochemical reactivity of DOM. The pH of water samples ranged from 5.4 to 8.3, and the concentrations of dissolved iron (Fe) were between < 0.06 and 22 μmol L-1. The filtered water samples received simulated solar radiation corresponding to a daily dose of sunlight, and photomineralization of dissolved organic carbon (DOC) to dissolved inorganic carbon (DIC) was measured for determination of spectral apparent quantum yields (AQY). During irradiation, photobleaching decreased the absorption coefficients of CDOM at 330 nm between 4.9 and 79 m-1 by 0.5 to 11 m-1. Irradiation generated DIC from 2.8 to 79 μmol C L-1. The AQY at 330 nm ranged between 31 and 273 ×10-6 mol C mol photons-1 h-1, which was correlated positively with concentration of dissolved Fe, and negatively with pH. Further statistical analyze indicated that the interaction between pH and Fe may explain much of the photochemical reactivity of DOM in the examined lakes, and land cover concerns main catchment areas also can have impact on the photoreaction process. This study may suggest how environmental conditions regulate DOM photomineralization in boreal lakes.
Heavy Metal Pollution of Lakes along the Mid-Lower Reaches of the Yangtze River in China: Intensity, Sources and Spatial Patterns

PubMed Central

Zeng, Haiao; Wu, Jinglu

2013-01-01

Lakes in the middle and lower reaches of the Yangtze River form a shallow lake group unique in the World that is becoming increasingly polluted by heavy metals. Previous studies have largely focused on individual lakes, with limited exploration of the regional pattern of heavy metal pollution of the lake group in this area. This paper explores the sources, intensity and spatial patterns of heavy metal pollution of lake sediments. A total of 45 sample lakes were selected and the concentrations of key metal elements in the sediments of each lake were measured. The cluster analysis (CA), principal component analysis (PCA) and Geo-accumulation index (Ig) analysis permitted analysis of the source and pollution intensity of the target lakes. Results suggested a notable spatial variation amongst the sample lakes. Lakes in the upper part of the lower reach of the Yangtze River surrounded by typical urban landscapes were strongly or extremely polluted, with high concentrations of Pb, Zn, Cu and Cd in their sediments. This was attributed to large amount of untreated industrial discharges and municipal sewage produced within the lake catchments. In contrast, the heavy-metal pollution of lakes in the Taihu Delta area was notably lower due to industrial restructuring and implementation of effective environmental protection measures. Lakes along the middle reach of Yangtze River surrounded by agricultural areas were unpolluted to moderately polluted by heavy metals overall. Our results suggested that lakes in the central part of China require immediate attention and efforts should be made to implement management plans to prevent further degradation of water quality in these lakes. PMID:23442559
Mass-movement and flood-induced deposits in Lake Ledro, southern Alps, Italy: implications for Holocene palaeohydrology and natural hazards

NASA Astrophysics Data System (ADS)

Simonneau, A.; Chapron, E.; Vannière, B.; Wirth, S. B.; Gilli, A.; Di Giovanni, C.; Anselmetti, F. S.; Desmet, M.; Magny, M.

2013-03-01

High-resolution seismic profiles and sediment cores from Lake Ledro combined with soil and riverbed samples from the lake's catchment area are used to assess the recurrence of natural hazards (earthquakes and flood events) in the southern Italian Alps during the Holocene. Two well-developed deltas and a flat central basin are identified on seismic profiles in Lake Ledro. Lake sediments have been finely laminated in the basin since 9000 cal. yr BP and frequently interrupted by two types of sedimentary events (SEs): light-coloured massive layers and dark-coloured graded beds. Optical analysis (quantitative organic petrography) of the organic matter present in soil, riverbed and lacustrine samples together with lake sediment bulk density and grain-size analysis illustrate that light-coloured layers consist of a mixture of lacustrine sediments and mainly contain algal particles similar to the ones observed in background sediments. Light-coloured layers thicker than 1.5 cm in the main basin of Lake Ledro are synchronous to numerous coeval mass-wasting deposits remoulding the slopes of the basin. They are interpreted as subaquatic mass-movements triggered by historical and pre-historical regional earthquakes dated to AD 2005, AD 1891, AD 1045 and 1260, 2545, 2595, 3350, 3815, 4740, 7190, 9185 and 11 495 cal. yr BP. Dark-coloured SEs develop high-amplitude reflections in front of the deltas and in the deep central basin. These beds are mainly made of terrestrial organic matter (soils and lignocellulosic debris) and are interpreted as resulting from intense hyperpycnal flood event. Mapping and quantifying the amount of soil material accumulated in the Holocene hyperpycnal flood deposits of the sequence allow estimating that the equivalent soil thickness eroded over the catchment area reached up to 5 mm during the largest Holocene flood events. Such significant soil erosion is interpreted as resulting from the combination of heavy rainfall and snowmelt. The recurrence of flash flood events during the Holocene was, however, not high enough to affect pedogenesis processes and highlight several wet regional periods during the Holocene. The Holocene period is divided into four phases of environmental evolution. Over the first half of the Holocene, a progressive stabilization of the soils present through the catchment of Lake Ledro was associated with a progressive reforestation of the area and only interrupted during the wet 8.2 event when the soil destabilization was particularly important. Lower soil erosion was recorded during the mid-Holocene climatic optimum (8000-4200 cal. yr BP) and associated with higher algal production. Between 4200 and 3100 cal. yr BP, both wetter climate and human activities within the drainage basin drastically increased soil erosion rates. Finally, from 3100 cal. yr BP to the present-day, data suggest increasing and changing human land use.
Multidisciplinary distinction of mass-movement and flood-induced deposits in lacustrine environments: implications for Holocene palaeohydrology and natural hazards (Lake Ledro, Southern Alps, Italy)

NASA Astrophysics Data System (ADS)

Simonneau, A.; Chapron, E.; Vannière, B.; Wirth, S. B.; Gilli, A.; Di Giovanni, C.; Anselmetti, F. S.; Desmet, M.; Magny, M.

2012-08-01

High-resolution seismic profiles and sediment cores from Lake Ledro combined with soil and river-bed samples from the lake's catchment area are used to assess the recurrence of natural hazards (earthquakes and flood events) in the southern Italian Alps during the Holocene. Two well-developed deltas and a flat central basin are identified on seismic profiles in Lake Ledro. Lake sediments are finely laminated in the basin since 9000 cal. yr BP and frequently interrupted by two types of sedimentary events: light-coloured massive layers and dark-coloured graded beds. Optical analysis (quantitative organic petrography) of the organic matter occurring in soils, river beds and lacustrine samples together with lake-sediment bulk density and grain-size analysis illustrate that light-coloured layers consist of a mixture of lacustrine sediments and mainly contain algal particles similar to the ones observed in background sediments. Light-coloured layers thicker than 1.5 cm in the main basin of Lake Ledro are dense and synchronous to numerous coeval mass-wasting deposits remoulding the slopes of the basin. They are interpreted as subaquatic mass movements triggered by historical and pre-historical regional earthquakes dated to 2005 AD, 1891 AD, 1045 AD and 1260, 2545, 2595, 3350, 3815, 4740, 7190, 9185 and 11495 cal. yr BP. Dark-coloured sedimentary event are dense and develop high-amplitude reflections in front of the deltas and in the deep central basin. These beds are mainly made of terrestrial organic matter (soils and ligno-cellulosic debris) and are interpreted as resulting from intense hyperpycnal flood events. Mapping and quantifying the amount of soil material accumulated in the Holocene hyperpycnal flood deposits of the sequence and applying the De Ploey erosion model allow estimating that the equivalent soil thickness eroded over the catchment area reached up to 4 mm during the largest Holocene flood events. Such significant soil erosion is interpreted as resulting from the combination of heavy rainfall and snowmelt. The recurrence of flash-flood events during the Holocene was however not high enough to affect pedogenesis processes and highlight several wet regional periods during the Holocene. The Holocene period is divided into four phases of environmental evolution. Over the first half of the Holocene, a progressive stabilization of the soils present through the catchment of Lake Ledro was associated with a progressive reforestation of the area and only interrupted during the wetter 8.2 event when the soil destabilization was particularly important. Lower soil erosion was recorded during the Mid-Holocene climatic optimum (8000-4200 cal. yr BP) and associated with higher algal production. Between 4200 and 3100 cal. yr BP, both wetter climate and human activities within the drainage basin drastically increased soil erosion rates. Finally, from 3100 cal. yr BP to the present-day, results suggest increasing and changing human land-use.

Stable isotopes and Digital Elevation Models to study nutrient inputs in high-Arctic lakes

NASA Astrophysics Data System (ADS)

Calizza, Edoardo; Rossi, David; Costantini, Maria Letizia; Careddu, Giulio; Rossi, Loreto

2016-04-01

Ice cover, run-off from the watershed, aquatic and terrestrial primary productivity, guano deposition from birds are key factors controlling nutrient and organic matter inputs in high-Arctic lakes. All these factors are expected to be significantly affected by climate change. Quantifying these controls is a key baseline step to understand what combination of factors subtends the biological productivity in Arctic lakes and will drive their ecological response to environmental change. Basing on Digital Elevation Models, drainage maps, and C and N elemental content and stable isotope analysis in sediments, aquatic vegetation and a dominant macroinvertebrate species (Lepidurus arcticus Pallas 1973) belonging to Tvillingvatnet, Storvatnet and Kolhamna, three lakes located in North Spitsbergen (Svalbard), we propose an integrated approach for the analysis of (i) nutrient and organic matter inputs in lakes; (ii) the role of catchment hydro-geomorphology in determining inter-lake differences in the isotopic composition of sediments; (iii) effects of diverse nutrient inputs on the isotopic niche of Lepidurus arcticus. Given its high run-off and large catchment, organic deposits in Tvillingvatnet where dominated by terrestrial inputs, whereas inputs were mainly of aquatic origin in Storvatnet, a lowland lake with low potential run-off. In Kolhamna, organic deposits seem to be dominated by inputs from birds, which actually colonise the area. Isotopic signatures were similar between samples within each lake, representing precise tracers for studies on the effect of climate change on biogeochemical cycles in lakes. The isotopic niche of L. aricticus reflected differences in sediments between lakes, suggesting a bottom-up effect of hydro-geomorphology characterizing each lake on nutrients assimilated by this species. The presented approach proven to be an effective research pathway for the identification of factors subtending to nutrient and organic matter inputs and transfer within each water body, as well as for the modelling of expected changes in nutrient content associated to changes in isotopic composition of sediments. Key words: nitrogen; carbon, sediment; biogeochemical cycle; climate change; hydro-ecology; isotopic niche; Svalbard
Tracing the sources of organic carbon in freshwater systems

NASA Astrophysics Data System (ADS)

Glendell, Miriam; Meersmans, Jeroen; Barclay, Rachel; Yvon-Durocher, Gabriel; Barker, Sam; Jones, Richard; Hartley, Iain; Dungait, Jennifer; Quine, Timothy

2016-04-01

Quantifying the lateral fluxes of carbon from land to inland waters is critical for the understanding of the global carbon cycle and climate change mitigation. However, the crucial role of rivers in receiving, transporting and processing the equivalent of terrestrial net primary production in their watersheds has only recently been recognised. In addition, the fluxes of carbon from land to ocean, and the impact of anthropogenic perturbation, are poorly quantified. Therefore, a mechanistic understanding of the processes involved in the loss and preservation of C along the terrestrial-aquatic continuum is required to predict the present and future contribution of aquatic C fluxes to the global C budget. This pilot study examines the effect of land use on the fate of organic matter within two headwater catchments in Cornwall (UK) in order to develop a methodological framework for investigating C-cycling across the entire terrestrial-aquatic continuum. To this end, we aim to characterise the spatial heterogeneity of soil erosion driven lateral fluxes of SOC to identify areas of erosion and deposition using 137Cs radio-isotope and trace the terrestrial versus aquatic origin of C along the river reaches and in lake sediments at the catchment outlet. The 3D spatial distribution of SOC has been investigated by sampling three depth increments (i.e. 0-15cm, 15-30cm and 30-50cm) along 14 hillslope transects within two sub-catchments of ˜km2 each. In total, 80 terrestrial sites were monitored and analysed for total C and N, and bulk stable 13C/15N isotope values, while 137Cs was used to obtain a detailed understanding of the spatial - temporal variability in erosion driven lateral fluxes of SOC within the catchments. The relative contribution of terrestrial and aquatic C was examined along the river reaches as well as in lake sediments at the catchment outlet by considering n-alkane signatures. By linking the C accumulation rates in lake sediments over decadal timescales from both terrestrial and aquatic sources as recorded in lake sediments to the measured rates of soil erosion and terrestrial & aquatic CO2 respiration rates, this study has paved a way towards a novel and cross-disciplinary approach to investigate and further improve current status of knowledge as regards C-cycling across the entire terrestrial-aquatic continuum. 137Cs was found to be useful to understand the dynamics and spatial pattern of lateral fluxes of sediment & C at the catchment scale, while tracing chemical composition of C using n-alkanes and stable isotopes (δ13C, δ15N) allowed distinguishing between the terrestrial vs. aquatic origin of C and determining main sources of particulate organic carbon in the aquatic environment within the two study catchments.
Dramatic water-level fluctuations in lakes under intense human impact: modelling the effect of vegetation, climate and hydrogeology

NASA Astrophysics Data System (ADS)

Vainu, M.

2012-04-01

Lakes form a highly important ecosystem in the glacial terrain of northern Europe and America, but their hydrology remains understudied. When the water-level of a lake drops significantly and rises again in a time span of half a century and the widespread explanation of the fluctuations seems insufficient, then it raises a question: how do different anthropogenic and natural processes actually affect the formation of a lakes' water body. The abovementioned scenario applies to three small closed-basin Estonian lakes (L. Ahnejärv, L. Kuradijärv and L. Martiska) analysed in the current study. These lakes suffered a major water-level drop (up to 3.8 m) between 1946 and 1987 and a major rise between 1987 and 2010, from 1 m (L. Ahnejärv) to 2.5 m (L. Kuradijärv). Decreasing and increasing groundwater abstraction near the lakes has been widely considered to be the only reason for the fluctuations. It is true that the most severe drop in the lake levels did occur after 1972 when groundwater abstraction for drinking water started in the vicinity of the lakes. However, the lake levels started to fall before the groundwater abstraction began and for the time being the lake levels have risen to a higher level than in the 1970s when the quantity of annually abstracted groundwater was similar to nowadays. Therefore the processes affecting the formation of the lakes' water body prove to be more complex than purely the hydrogeological change caused by groundwater abstraction. A new deterministic water balance model (where the evaporation from the lake surface was calculated by Penman equation and the catchment runoff by Thornthwaite-Mather soil-moisture model), compiled for the study, coupled with LiDAR-based GIS-modelling of the catchments was used to identify the different factors influencing the lakes' water level. The modelling results reveal that the moderate drop in lake water levels before the beginning of groundwater abstraction was probably caused by the growth of a coniferous forest on the lake catchments, due to which evapotranspiration and subsequently runoff from the catchment decreased. The forest had been destroyed by wildfires during World War II. The water-level rise that the lakes have gone through in the last 20 years has in the case of L. Ahnejärv been caused by changing meteorological conditions (precipitation, air temperature and wind speed). In the case of Lakes Kuradijärv and Martiska the change has been caused by both the raise of groundwater level (caused by the decreasing groundwater abstraction) and the change of meteorological conditions. Therefore the vegetation change on the catchment and changes in meteorological conditions have played as important or, at times, even more important role in the water-level fluctuations than changes in the hydrogeological conditions. Although concentrating on three specific lakes in a specific region, the result of the study indicate the complexity of factors influencing the amount of water stored in a lake at a certain moment. Therefore it manifests a need for improved models in order to improve lake management around the world.
Detection of Critical LUCC Indices and Sensitive Watershed Regions Related to Lake Algal Blooms: A Case Study of Taihu Lake

PubMed Central

Lin, Chen; Ma, Ronghua; Su, Zhihu; Zhu, Qing

2015-01-01

Taihu Lake in China has suffered from severe eutrophication over the past 20 years which is partly due to significant land use/cover change (LUCC). There is an increasing need to detect the critical watershed region that significantly affects lake water degradation, which has great significance for environmental protection. However, previous studies have obtained conflicting results because of non–uniform lake indicators and inadequate time periods. To identify the sensitive LUCC indices and buffer distance regions, three lake divisions (Meiliang Lake, Zhushan Lake and Western Coastal region) and their watershed region within the Taihu Lake basin were chosen as study sites, the algal area was used as a uniform lake quality indicator and modeled with LUCC indices over the whole time series. Results showed that wetland (WL) and landscape index such as Shannon diversity index (SHDI) appeared to be sensitive LUCC indices when the buffer distance was less than 5 km, while agricultural land (AL) and landscape fragmentation (Ci) gradually became sensitive indices as buffer distances increased to more than 5 km. For the relationship between LUCC and lake algal area, LUCC of the WC region seems to have no significant effect on lake water quality. Conversely, LUCC within ML and ZS region influenced algal area of corresponding lake divisions greatly, while the most sensitive regions were found in 3 km to 5 km, rather than the whole catchment. These results will be beneficial for the further understanding of the relationship between LUCC and lake water quality, and will provide a practical basis for the identification of critical regions for lake. PMID:25642691
Long-term chloride concentrations in North American and European freshwater lakes

PubMed Central

Dugan, Hilary A.; Summers, Jamie C.; Skaff, Nicholas K.; Krivak-Tetley, Flora E.; Doubek, Jonathan P.; Burke, Samantha M.; Bartlett, Sarah L.; Arvola, Lauri; Jarjanazi, Hamdi; Korponai, János; Kleeberg, Andreas; Monet, Ghislaine; Monteith, Don; Moore, Karen; Rogora, Michela; Hanson, Paul C.; Weathers, Kathleen C.

2017-01-01

Anthropogenic sources of chloride in a lake catchment, including road salt, fertilizer, and wastewater, can elevate the chloride concentration in freshwater lakes above background levels. Rising chloride concentrations can impact lake ecology and ecosystem services such as fisheries and the use of lakes as drinking water sources. To analyze the spatial extent and magnitude of increasing chloride concentrations in freshwater lakes, we amassed a database of 529 lakes in Europe and North America that had greater than or equal to ten years of chloride data. For each lake, we calculated climate statistics of mean annual total precipitation and mean monthly air temperatures from gridded global datasets. We also quantified land cover metrics, including road density and impervious surface, in buffer zones of 100 to 1,500 m surrounding the perimeter of each lake. This database represents the largest global collection of lake chloride data. We hope that long-term water quality measurements in areas outside Europe and North America can be added to the database as they become available in the future. PMID:28786983
Long-term chloride concentrations in North American and European freshwater lakes.

PubMed

Dugan, Hilary A; Summers, Jamie C; Skaff, Nicholas K; Krivak-Tetley, Flora E; Doubek, Jonathan P; Burke, Samantha M; Bartlett, Sarah L; Arvola, Lauri; Jarjanazi, Hamdi; Korponai, János; Kleeberg, Andreas; Monet, Ghislaine; Monteith, Don; Moore, Karen; Rogora, Michela; Hanson, Paul C; Weathers, Kathleen C

2017-08-08

Anthropogenic sources of chloride in a lake catchment, including road salt, fertilizer, and wastewater, can elevate the chloride concentration in freshwater lakes above background levels. Rising chloride concentrations can impact lake ecology and ecosystem services such as fisheries and the use of lakes as drinking water sources. To analyze the spatial extent and magnitude of increasing chloride concentrations in freshwater lakes, we amassed a database of 529 lakes in Europe and North America that had greater than or equal to ten years of chloride data. For each lake, we calculated climate statistics of mean annual total precipitation and mean monthly air temperatures from gridded global datasets. We also quantified land cover metrics, including road density and impervious surface, in buffer zones of 100 to 1,500 m surrounding the perimeter of each lake. This database represents the largest global collection of lake chloride data. We hope that long-term water quality measurements in areas outside Europe and North America can be added to the database as they become available in the future.
Rock glaciers in crystalline catchments: Hidden permafrost-related threats to alpine headwater lakes.

PubMed

Ilyashuk, Boris P; Ilyashuk, Elena A; Psenner, Roland; Tessadri, Richard; Koinig, Karin A

2018-04-01

A global warming-induced transition from glacial to periglacial processes has been identified in mountainous regions around the world. Degrading permafrost in pristine periglacial environments can produce acid rock drainage (ARD) and cause severe ecological damage in areas underlain by sulfide-bearing bedrock. Limnological and paleolimnological approaches were used to assess and compare ARDs generated by rock glaciers, a typical landform of the mountain permafrost domain, and their effects on alpine headwater lakes with similar morphometric features and underlying bedrock geology, but characterized by different intensities of frost action in their catchments during the year. We argue that ARD and its effects on lakes are more severe in the alpine periglacial belt with mean annual air temperatures (MAAT) between -2°C and +3°C, where groundwater persists in the liquid phase for most of the year, in contrast to ARD in the periglacial belt where frost action dominates (MAAT < -2°C). The findings clearly suggest that the ambient air temperature is an important factor affecting the ARD production in alpine periglacial environments. Applying the paleoecological analysis of morphological abnormalities in chironomids through the past millennium, we tested and rejected the hypothesis that unfavorable conditions for aquatic life in the ARD-stressed lakes are largely related to the temperature increase over recent decades, responsible for the enhanced release of ARD contaminants. Our results indicate that the ARDs generated in the catchments are of a long-lasting nature and the frequency of chironomid morphological deformities was significantly higher during the Little Ice Age (LIA) than during pre- or post-LIA periods, suggesting that lower water temperatures may increase the adverse impacts of ARD on aquatic invertebrates. This highlights that temperature-mediated modulations of the metabolism and life cycle of aquatic organisms should be considered when reconstructing long-term trends in the ecotoxicological state of lakes. © 2017 The Authors. Global Change Biology Published by John Wiley & Sons Ltd.
Towards a GLOF hazard map for the city of Huaraz, Cordillera Blanca, Peru

NASA Astrophysics Data System (ADS)

Frey, Holger; Huggel, Christian; E Chisolm, Rachel; Gonzales, César; Cochachin, Alejo; Portocarrero, César

2017-04-01

Huaraz, with 120,000 inhabitants, is the largest city at the foot of the Cordillera Blanca Mountain Range, Peru, and is located at the confluence of the Quillcay River with the main Santa River. Three moraine dammed glacier lakes are located in the headwaters of the Quillcay catchment, which pose a potential threat of glacier lake outburst floods (GLOFs) to Huaraz: Laguna Cuchillacocha (2.5 x 106 m3), Laguna Tullparaju (12 x 106 m3), and Laguna Palcacocha (17 x 106 m3). The latter burst out in 1941, causing one of the deadliest GLOFs known in history, with about 2000 casualties and destroying a third of the city of Huaraz. Currently, the presence of these lakes within potential runout distances of possibly very large ice or rock/ice-avalanches, combined with the large damage potential in the city of Huaraz, some 20 km downstream of the lakes and further potentially endangered infrastructures such as the city of Trujillo, large-scale irrigation projects and hydropower plants along the Santa River poses a high-risk situation, despite lake safety systems at all three lakes were constructed in the last century. At Laguna Palcacocha, temporary measures, such as syphoning and a permanent supervision by a team of observers are undertaken at Laguna Palcacocha. For the future, more permanent measures are planned, including non-structural measures, such as a sensor-based early warning system for the entire catchment. In this framework, a preliminary GLOF hazard map for the entire Quillcay catchment has been developed, based on physically-based numerical modeling. For each of the three lakes, three scenarios of different magnitudes and related probabilities were modeled. For each case, a series of models was used to simulate each part of the chain of interacting processes. The eventual GLOFs were simulated with FLO2D for Palcacocha and RAMMS for Tullparaju and Cuchillacocha. Small, medium and large scenarios were merged for all three lakes, in order to come up with a single hazard map for the entire catchment. Inundation heights were first translated into intensities, and then intensities were converted into hazard levels, according to the probability of the scenario, which resulted in the preliminary hazard map. This map is currently used for informing the population and for the planning of further mitigation actions. For the development of the final hazard map, more detailed simulations in the urban area of Huaraz are needed, combined with field mapping to adjust the map to local conditions and peculiarities. Related efforts are ongoing, in close collaboration with local institutions and authorities. Besides the scientific challenges for the development of such a hazard map, the institutional aspect for the official approval and legal validation is a major challenge that needs to be tackled.
Land use changing and land use optimization of Lake Baikal basin on the example of two key areas

NASA Astrophysics Data System (ADS)

Solodyankina, S.

2012-04-01

Lake Baikal contains roughly 20% of the world's unfrozen surface fresh water. It was declared a UNESCO World Heritage Site in 1996. Today levels of urbanization and economic stress on environmental resources is increasing on the shorts of the lake Baikal. The potential of economic development (industry, local tourism, and mining) of the Severobaykalsky and Sludyansky districts is rather high although they are characterized not only by beneficial features for local economy but also by considerable disadvantages for nature of this world valuable territory. This investigation show human-caused landscape changes during economic development of the two key areas in Baikal water catchment basin during 10 years (point of reference is 2000 year). Key areas are 1) the Baikalo-Patomskoe highland in the north of the Baikal catchment basin (Severobaykalsky district, Republic of Buryatia); 2) Khamar-Daban mountain system in the south of the Baikal catchment basin (Sludyansky districy, Irkutsk region). Since 2000 year land use of the territory has changed. Areas of agriculture were reduced but recreation activity on the bank of the lake was increased. Methods of GIS analysis and local statistic analysis of landscape characteristic were used. Nature, rural and urban areas ratio are estimated. Vegetation and soil condition assessment were made. The essence of this research is in helping to make decisions linked to upcoming problems: situation identification, evaluation and forecasting of the potential landscape condition, optimization of land use, mitigation of impact and mapping of territories and nature resources which have a high ecological value or endangered by industrial impact. For this purpose landscape maps of the territories on the base of the remote sensing information and field investigations were created. They used to calculate potential landscape functions of the territory without taking into account present impact of anthropogenic actions. Land use maps for years 2000 and 2010 were created to show: 1) how many landscape functions (ecosystem services) have been missed in time period of 2000-2010 years; 2) trends of land use changing. The nature-anthropogenic landscapes classification is developed, where natural and anthropogenic factors are taken into account in one system. It used to considerate of cumulative impacts of anthropogenic actions for each relevant resource, and to analyse of all past, present, and reasonably foreseeable future condition of whole landscape and its components (parent rock, surface and ground water, soil, flora and fauna, air).
Influence of permafrost on lake terraces of Lake Heihai (NE Tibetan Plateau)

NASA Astrophysics Data System (ADS)

Lockot, Gregori; Hartmann, Kai; Wünnemann, Bernd

2013-04-01

The Tibetan Plateau (TP) is one of the key regions for climatic global change. Besides the poles the TP is the third highest storage of frozen water in glaciers. Here global warming is three times higher than in the rest of the world. Additionally the TP provides water for billions of people and influences the moisture availability from the Indian and East Asian monsoon systems. During the Holocene extent and intensity of the monsoonal systems changed. Hence, in the last decades, a lot of work was done to reconstruct timing and frequency of monsoonal moisture, to understand the past and give a better forecast for the future. Comparative workings often show very heterogeneous patterns of timing and frequency of the Holocene precipitation and temperature maximum, emphasizing the local importance of catchment dynamics. In this study we present first results of lake Heihai (36°N, 93°15'E, 4500m a.s.l.), situated at the north-eastern border of the TP. The lake is surrounded by a broad band of near-shore lake sediments, attesting a larger lake extent in the past. These sediments were uplifted by permafrost, reaching nowadays heights ca. +8 meters above present lake level. Due to the uplift one of the main inflows was blocked and the whole hydrology of the catchment changed. To quantify the uplift of permafrost Hot Spot Analysis were accomplished at a DEM of the near-shore area. As a result regions of high permafrost uplift and those which mirror the original height of lake ground were revealed. The most obvious uplift took place in the northern and western part of the lake, where the four uplift centers are located. In contrast the southern and eastern areas show a rather degraded pattern (probably by fluvial erosion, thermokarst, etc.). The ancient lake bottom, without permafrost uplift was estimated to be 4-6 meters above the modern lake level. For a better understanding of permafrost interaction inside the terrace bodies a 5m sediment profile was sampled and elements, minerals, grain size and isotopes were analyzed. Different factor and end-member analysis were applied on the data, resulting in a clear dichotomy between permafrost-influenced and uninfluenced layers. Hence a completely different process composition must be assumed.
Contemporary suspended sediment fluxes and accumulation processes in the small proglacial Sætrevatnet sub-catchment, Bødalen, Western Norway

NASA Astrophysics Data System (ADS)

Liermann, S.; Beylich, A. A.

2012-04-01

A combination of different process monitoring, lake sediment coring and sediment analysis methods and techniques were applied in order (i) to ascertain the hydro-meteorological controls of runoff generation, suspended sediment transport and sediment accumulation on the delta and in Lake Sætrevatnet and (ii) to define the role of the small proglacial lake Sætrevatnet within the basin-wide catchment routing system of the Bødalen valley-fjord system (Nordfjord area, western Norway). Within the Bødalen valley investigations of sediment transfer and sediment accumulation processes were focused on the small proglacial Sætrevatnet area in upper Bødalen. The proglacial Sætrevatnet valley segment shows the characteristic seasonal weather-depended runoff variation for glacierized drainage basins. Suspended sediment concentration varied closely related to water discharge. Hence, significant suspended sediment transport is associated to high runoff conditions during thermally induced summer glacier melt (when 61.9% of the annual suspended sediment yield was recorded in 2010) as well as to single extreme rainfall events (19.8% of the annual suspended sediment yield was recorded during a single extreme rainfall event in 2010). Solar radiation and the magnitude and frequency of extreme rainfall events were found to be crucial for the rate of sediment transport within the Sætrevatnet sub-catchment. Altogether, the annual suspended sediment yield is with 24.2 t km-2 notable lower as compared to other glacierized basins worldwide. Delta accumulation rates at the inlet of Lake Sætrevatnet of 4 cm yr-1 in 2009 and 3.5 cm yr-1 in 2010 as well as a mean annual delta advance of about 3 - 4 m as calculated from comparisons of aerial photographs point to an ongoing and rapid sediment infill of the Sætrevatnet valley basin. Lacustrine sediment sequence analysis and 210-Pb and 137-Cs dating of samples taken from the Lake Sætrevatnet confirm high annual accumulation rates. Based on a basic CSR model (with the assumption of a constant rate of 210-Pb supply) and additionally validated by 137-Cs activity an annual lake sedimentation rate of 1.7cm was calculated. Both the low suspended sediment yields and the high accumulation rates emphasize the importance of bedload and nearly to the channel beds transported sediments for the Sætrevatnet lake system. As a result, Lake Sætrevatnet currently traps about 80-85 % of the sediments delivered from the upstream located glacial and proglacial system highlighting the importance of small ephemeral lakes within larger valley-fjord sediment routing systems. As a next step the potential yearly pattern of laminations (varves) is discussed in association with the calculated sedimentation rates within the Sætrevatnet valley segment. ITRAX (XRF) analysis, magnetic susceptibility measurements and the interpretation of the potential varve/lamination thickness and composition enable the identification of different sedimentary processes and related discharge mechanisms within the Saetrevatnet sub-catchment. Rhythmites are tentatively associated to regional meteorological variables (temperature; precipitation, e.g. heavy rainfall events). Analysis of grain size composition, density and carbon (TOC, inorganic carbon using LECO) are carried out to characterize the laminated structure and to identify possible sediment sources.
Temporal coherence of two alpine lake basins of the Colorado Front Range, USA

USGS Publications Warehouse

Baron, Jill S.; Caine, N.

2000-01-01

1. Knowledge of synchrony in trends is important to determining regional responses of lakes to disturbances such as atmospheric deposition and climate change. We explored the temporal coherence of physical and chemical characteristics of two series of mostly alpine lakes in nearby basins of the Colorado Rocky Mountains. Using year-to-year variation over a 10-year period, we asked whether lakes more similar in exposure to the atmosphere be-haved more similarly than those with greater influence of catchment or in-lake processes.2. The Green Lakes Valley and Loch Vale Watershed are steeply incised basins with strong altitudinal gradients. There are glaciers at the heads of each catchment. The eight lakes studied are small, shallow and typically ice-covered for more than half the year. Snowmelt is the dominant hydrological event each year, flushing about 70% of the annual discharge from each lake between April and mid-July. The lakes do not thermally stratify during the period of open water. Data from these lakes included surface water temper-ature, sulphate, nitrate, calcium, silica, bicarbonate alkalinity and conductivity.3. Coherence was estimated by Pearson's correlation coefficient between lake pairs for each of the different variables. Despite close geographical proximity, there was not a strong direct signal from climatic or atmospheric conditions across all lakes in the study. Individual lake characteristics overwhelmed regional responses. Temporal coherence was higher for lakes within each basin than between basins and was highest for nearest neighbours.4. Among the Green Lakes, conductivity, alkalinity and temperature were temporally coherent, suggesting that these lakes were sensitive to climate fluctuations. Water tem-perature is indicative of air temperature, and conductivity and alkalinity concentrations are indicative of dilution from the amount of precipitation flushed through by snowmelt.5. In Loch Vale, calcium, conductivity, nitrate, sulphate and alkalinity were temporally coherent, while silica and temperature were not. This suggests that external influences are attenuated by internal catchment and lake processes in Loch Vale lakes. Calcium and sulphate are primarily weathering products, but sulphate derives both from deposition and from mineral weathering. Different proportions of snowmelt versus groundwater in different years could influence summer lake concentrations. Nitrate is elevated in lake waters from atmospheric deposition, but the internal dynamics of nitrate and silica may be controlled by lake food webs. Temperature is attenuated by inconsistently different climates across altitude and glacial meltwaters.6. It appears that, while the lakes in the two basins are topographically close, geologically and morphologically similar, and often connected by streams, only some attributes are temporally coherent. Catchment and in-lake processes influenced temporal patterns, especially for temperature, alkalinity and silica. Montane lakes with high altitudinal gradients may be particularly prone to local controls compared to systems where coherence is more obvious.
Catchment tracers reveal discharge, recharge and sources of groundwater-borne pollutants in a novel lake modelling approach

NASA Astrophysics Data System (ADS)

Kristensen, Emil; Madsen-Østerbye, Mikkel; Massicotte, Philippe; Pedersen, Ole; Markager, Stiig; Kragh, Theis

2018-02-01

Groundwater-borne contaminants such as nutrients, dissolved organic carbon (DOC), coloured dissolved organic matter (CDOM) and pesticides can have an impact the biological quality of lakes. The sources of pollutants can, however, be difficult to identify due to high heterogeneity in groundwater flow patterns. This study presents a novel approach for fast hydrological surveys of small groundwater-fed lakes using multiple groundwater-borne tracers. Water samples were collected from the lake and temporary groundwater wells, installed every 50 m within a distance of 5-45 m to the shore, were analysed for tracer concentrations of CDOM, DOC, total dissolved nitrogen (TDN, groundwater only), total nitrogen (TN, lake only), total dissolved phosphorus (TDP, groundwater only), total phosphorus (TP, lake only), δ18O / δ16O isotope ratios and fluorescent dissolved organic matter (FDOM) components derived from parallel factor analysis (PARAFAC). The isolation of groundwater recharge areas was based on δ18O measurements and areas with a high groundwater recharge rate were identified using a microbially influenced FDOM component. Groundwater discharge sites and the fractions of water delivered from the individual sites were isolated with the Community Assembly via Trait Selection model (CATS). The CATS model utilized tracer measurements of TDP, TDN, DOC and CDOM from the groundwater samples and related these to the tracer measurements of TN, TP, DOC and CDOM in the lake. A direct comparison between the lake and the inflowing groundwater was possible as degradation rates of the tracers in the lake were taken into account and related to a range of water retention times (WRTs) of the lake (0.25-3.5 years in 0.25-year increments). These estimations showed that WRTs above 2 years required a higher tracer concentration of inflowing water than found in any of the groundwater wells around the lake. From the estimations of inflowing tracer concentration, the CATS model isolated groundwater discharge sites located mainly in the eastern part of the lake with a single site in the southern part. Observations from the eastern part of the lake revealed an impermeable clay layer that promotes discharge during heavy precipitation events, which would otherwise be difficult to identify using traditional hydrological methods. In comparison to the lake concentrations, high tracer concentrations in the southern part showed that only a smaller fraction of water could originate from this area, thereby confirming the model results. A Euclidean cluster analysis of δ18O isotopes identified recharge sites corresponding to areas adjacent to drainage channels, and a cluster analysis of the microbially influenced FDOM component C4 further identified five sites that showed a tendency towards high groundwater recharge rate. In conclusion, it was found that this methodology can be applied to smaller lakes within a short time frame, providing useful information regarding the WRT of the lake and more importantly the groundwater recharge and discharge sites around the lake. Thus, it is a tool for specific management of the catchment.
Lithium isotopes and implications on chemical weathering in the catchment of Lake Donggi Cona, northeastern Tibetan Plateau

NASA Astrophysics Data System (ADS)

Weynell, Marc; Wiechert, Uwe; Schuessler, Jan A.

2017-09-01

This study presents lithium (Li) isotope ratios (δ7Li) for rocks, sediments, suspended particulate material, and dissolved Li from the Lake Donggi Cona catchment, located on the northeastern Tibetan Plateau, China. The average δ7Li = +1.9‰ of the bedrocks is estimated from local loess. δ7Li values decrease progressively within the sediment cascade from loess, to river and lake floor sediments. The lake floor sediments average at -0.7‰. The difference between bedrock and lake sediments reflects the preferential fractionation of dissolved 6Li into clay minerals (mostly illite) in the weathering zone and grain-size sorting during fluvial sediment transport. The δ7Li values of stream and lake water samples range from +13.6 to +20.8‰, whereas thermal waters fall between +5.9 and +11.6‰. The δ7Li values of lake water samples are close to +17‰ and reflect mixing of waters from two perennial inflows and thermal waters. Dissolved Li in streams represents an integrated isotopic signal derived from soil solutions in the weathering zone. An apparent isotopic fractionation of -17.8 ± 1.6‰ (αsec-sol ∼ 0.982) between secondary minerals and solution was determined. An inflow that drains a sub-catchment in the north carries a high proportion of thermal waters. Despite of the high proportion of admixed thermal waters with high Li concentrations and low δ7Li, this stream has the highest δ7Li values of about +21‰. This is consistent with admixing of thermal waters to solutions in the weathering zone and subsequent fractionation by preferential uptake of isotopically light dissolved Li into secondary phases. Based on Li isotope ratios of the dissolved and solid export flux from the weathering zone we calculated that around five times more Li is exported in particles than dissolved in streams. An average δ7Li value of about +17‰ of most streams and the lake is reflecting a low weathering intensity and chemical weathering rate of about 4 t/km2/a. Low weathering rates and an erosion dominated weathering system are consistent with moderate precipitations, the cold climate, and the high relief of the study area.
A spatial classification and database for management, research, and policy making: The Great Lakes aquatic habitat framework

USGS Publications Warehouse

Wang, Lizhu; Riseng, Catherine M.; Mason, Lacey; Werhrly, Kevin; Rutherford, Edward; McKenna, James E.; Castiglione, Chris; Johnson, Lucinda B.; Infante, Dana M.; Sowa, Scott P.; Robertson, Mike; Schaeffer, Jeff; Khoury, Mary; Gaiot, John; Hollenhurst, Tom; Brooks, Colin N.; Coscarelli, Mark

2015-01-01

Managing the world's largest and most complex freshwater ecosystem, the Laurentian Great Lakes, requires a spatially hierarchical basin-wide database of ecological and socioeconomic information that is comparable across the region. To meet such a need, we developed a spatial classification framework and database — Great Lakes Aquatic Habitat Framework (GLAHF). GLAHF consists of catchments, coastal terrestrial, coastal margin, nearshore, and offshore zones that encompass the entire Great Lakes Basin. The catchments captured in the database as river pour points or coastline segments are attributed with data known to influence physicochemical and biological characteristics of the lakes from the catchments. The coastal terrestrial zone consists of 30-m grid cells attributed with data from the terrestrial region that has direct connection with the lakes. The coastal margin and nearshore zones consist of 30-m grid cells attributed with data describing the coastline conditions, coastal human disturbances, and moderately to highly variable physicochemical and biological characteristics. The offshore zone consists of 1.8-km grid cells attributed with data that are spatially less variable compared with the other aquatic zones. These spatial classification zones and their associated data are nested within lake sub-basins and political boundaries and allow the synthesis of information from grid cells to classification zones, within and among political boundaries, lake sub-basins, Great Lakes, or within the entire Great Lakes Basin. This spatially structured database could help the development of basin-wide management plans, prioritize locations for funding and specific management actions, track protection and restoration progress, and conduct research for science-based decision making.
Biological studies of atmospheric deposition impact on biota in Kola North Mountain Lakes, Russia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yakovlev, V.; Sharov, A.; Vandysh, O.

1996-12-31

In the framework of the AL:PE projects, biological studies of phyto-, zooplankton and zoobenthos communities of a small lakes situated in Chuna tundra and Chibiny mountains in Murmansk region were performed in 1993-1995. The lakes are the typical oligotrophic mountain lakes. In the Chibiny lake phytoplankton were presented mostly by species from rock catchment area. Summer phytoplankton state in the lakes showed no acidification in 1993-1995. However, the great number dead cells of acid tolerance diatoms, such as Tabellaria flocculosa found in the Chuna lake in summer period, may indicate a presence of acid episodes. Zooplankton of the lakes ismore » typical for high oligotrophic mountain lakes. However, lack of the acid sensitive daphniidae cladocerans seems to be a result of acidification effects. There were no significant relationships between benthic invertebrates species composition and present water acidity of the lakes. The typical for mountain lakes taxa (Prodiamesinae chironomids, stone flies and mayflies) were found in lake shore and streams. Despite the only little evidence of damage in biota, the further biological studies would be useful for long-term monitoring of the mountain lakes.« less
The Role of Dynamic Storage in the Response to Snowmelt Conditions in the Southwestern United States: Flux Hysteresis at the Catchment Scale

NASA Astrophysics Data System (ADS)

Driscoll, J. M.; Meixner, T.; Ferré, T. P. A.; Williams, M. W.; Sickman, J. O.; Molotch, N. P.; Jepsen, S. M.

2014-12-01

The role of dynamic storage in catchment discharge response to earlier snowmelt timing has not been fully quantified. Green Lake 4 (GL4) and Emerald Lake Watershed (ELW) have similar high-elevation settings but GL4 has greater estimated storage capacity relative to ELW due to differences in physical structure. Daily catchment area-normalized input (modelled snowmelt estimates) and output (measured discharge) in conjunction with mineral weathering products (hydrochemical data) for eleven snowmelt seasons from GL4 (more storage) and ELW (less storage) were used to determine the role of dynamic storage at the catchment scale. Daily fluxes generally show snowmelt is greater than discharge initially, changing mid-season to discharge being greater than snowmelt, creating a counter-clockwise hysteresis loop for each snowmelt season. This hysteresis loop can be approximated with a least-squares fitted ellipse. The properties of fitted ellipses were used to quantify catchment response, which were then compared between catchments with different storage capacities (GL4 and ELW). The eccentricity of the fitted ellipses can be used to quantify delay between snowmelt and discharge due to connection to subsurface storage; narrower loops show minimal storage delay whereas wider loops show greater storage delay. Variability of mineral weathering products shows changes in contribution from stored water over the snowmelt season. Both catchments show a moderate linear correlation between fitted ellipse area and total snowmelt volume (GL4 R2=0.516, ELW R2=0.614). Ellipse eccentricity is more consistent among years in ELW (range=0.81-0.94) than in GL4 (range=0.54-0.95), indicating a more consistent hydrologic structure and connectivity to shallow storage at ELW. The linear correlation between seasonal eccentricity versus snowmelt timing is stronger in ELW than GL4 (R2=0.741 and 0.223, respectively). ELW shows hydrochemical response independent of snowmelt timing, whereas GL4 shows more variability. The larger storage capacity of GL4 allows for a greater range of physical and chemical response to input conditions. The limited storage capacity of ELW shows greater vulnerability of physical response to changes in snowmelt conditions, though chemical response remains constant regardless of snowmelt conditions.
Interpretation and application of carbon isotope ratios in freshwater diatom silica

PubMed Central

Webb, Megan; Wynn, Peter M.; Heiri, Oliver; van Hardenbroek, Maarten; Pick, Frances; Russell, James M.; Stott, Andy W.; Leng, Melanie J.

2016-01-01

ABSTRACT Carbon incorporated into diatom frustule walls is protected from degradation enabling analysis for carbon isotope composition (δ13Cdiatom). This presents potential for tracing carbon cycles via a single photosynthetic host with well‐constrained ecophysiology. Improved understanding of environmental processes controlling carbon delivery and assimilation is essential to interpret changes in freshwater δ13Cdiatom. Here relationships between water chemistry and δ13Cdiatom from contemporary regional data sets are investigated. Modern diatom and water samples were collected from river catchments within England and lake sediments from across Europe. The data suggest dissolved, biogenically produced carbon supplied proportionately to catchment productivity was critical in the rivers and soft water lakes. However, dissolved carbon from calcareous geology overwhelmed the carbon signature in hard water catchments. Both results demonstrate carbon source characteristics were the most important control on δ13Cdiatom, with a greater impact than productivity. Application of these principles was made to a sediment record from Lake Tanganyika. δ13Cdiatom co‐varied with δ13Cbulk through the last glacial and Holocene. This suggests carbon supply was again dominant and exceeded authigenic demand. This first systematic evaluation of contemporary δ13Cdiatom controls demonstrates that diatoms have the potential to supply a record of carbon cycling through lake catchments from sediment records over millennial timescales. PMID:27656013
Assessing risk of non-compliance of phosphorus standards for lakes in England and Wales

NASA Astrophysics Data System (ADS)

Duethmann, D.; Anthony, S.; Carvalho, L.; Spears, B.

2009-04-01

High population densities, use of inorganic fertilizer and intensive livestock agriculture have increased phosphorus loads to lakes, and accelerated eutrophication is a major pressure for many lakes. The EC Water Framework Directive (WFD) requires that good chemical and ecological quality is restored in all surface water bodies by 2015. Total phosphorus (TP) standards for lakes in England and Wales have been agreed recently, and our aim was to estimate what percentage of lakes in England and Wales is at risk of failing these standards. With measured lake phosphorus concentrations only being available for a small number of lakes, such an assessment had to be model based. The study also makes a source apportionment of phosphorus inputs into lakes. Phosphorus loads were estimated from a range of sources including agricultural loads, sewage effluents, septic tanks, diffuse urban sources, atmospheric deposition, groundwater and bank erosion. Lake phosphorus concentrations were predicted using the Vollenweider model, and the model framework was satisfactorily tested against available observed lake concentration data. Even though predictions for individual lakes remain uncertain, results for a population of lakes are considered as sufficiently robust. A scenario analysis was carried out to investigate to what extent reductions in phosphorus loads would increase the number of lakes achieving good ecological status in terms of TP standards. Applying the model to all lakes in England and Wales greater than 1 ha, it was calculated that under current conditions roughly two thirds of the lakes would fail the good ecological status with respect to phosphorus. According to our estimates, agricultural phosphorus loads represent the most frequent dominant source for the majority of catchments, but diffuse urban runoff also is important in many lakes. Sewage effluents are the most frequent dominant source for large lake catchments greater than 100 km². The evaluation in terms of total load can be misleading in terms of what sources need to be tackled by catchment management for most of the lakes. For example sewage effluents are responsible for the majority of the total load but are the dominant source in only a small number of larger lake catchments. If loads from all sources were halved this would potentially increase the number of complying lakes to two thirds but require substantial measures to reduce phosphorus inputs to lakes. For agriculture, required changes would have to go beyond improvements of agricultural practise, and need to include reducing the intensity of land use. The time required for many lakes to respond to reduced nutrient loading is likely to extend beyond the current timelines of the WFD due to internal loading and biological resistances.
Saving the Baltic Sea, the inland waters of its drainage basin, or both? spatial perspectives on reducing P-loads in eastern Sweden.

PubMed

Andersson, Ingela; Jarsjö, Jerker; Petersson, Mona

2014-11-01

Nutrient loads from inland sources to the Baltic Sea and adjacent inland waters need to be reduced in order to prevent eutrophication and meet requirements of the European Water Framework Directive (WFD) and the Baltic Sea Action Plan (BSAP). We here investigate the spatial implications of using different possible criteria for reducing water-borne phosphorous (P) loads in the Northern Baltic Sea River Basin District (NBS-RBD) in Sweden. Results show that most catchments that have a high degree of internal eutrophication do not express high export of P from their outlets. Furthermore, due to lake retention, lake catchments with high P-loads per agricultural area (which is potentially of concern for the WFD) did not considerably contribute to the P-loading of the Baltic Sea. Spatially uniform water quality goals may, therefore, not be effective in NBS-RBD, emphasizing more generally the need for regional adaptation of WFD and BSAP-related goals.

The Effect of Catchment Urbanization on Nutrient Uptake and Biofilm Enzyme Activity in Lake Superior (USA) Tributary Streams

EPA Science Inventory

We used landscape, habitat, and chemistry variables, along with nutrient spiraling metrics and biofilm extracellular enzyme activity (EEA), to assess the response of streams to the level of urbanization within their catchments. For this study nine streams of similar catchment are...
Impact of Holocene terrestrial vegetation succession on the biogeochemical structure and function of an Arctic lake, Alaska

NASA Astrophysics Data System (ADS)

Langdon, P. G.; Whiteford, E.; Hopla, E.; van Hardenbroek, M.; Turner, S.; Edwards, M. E.; Jones, V.; McGowan, S.; Wiik, E.; Anderson, N. J.

2016-12-01

Vegetation changes are occurring in the Arctic as warming progresses, a process often referred to as "greening". The northward expansion of woody shrubs influence nutrient cycling in soils, including carbon (C) cycling, but the extent to which they will change the storage or release of carbon at a landscape scale is uncertain. The role that lakes play in this system is not fully understood, but it is known that many lakes in the tundra and northern forests are today releasing carbon dioxide (and methane) into the atmosphere in significant amounts, and a proportion of this carbon comes into the lake from the vegetation and soils of the surrounding landscape. Furthermore, the number of lakes contributing to this gas release has been hitherto underestimated, and it is thus likely that lakes play a far greater role in terms of total gas emissions. In order to assess the relationships between vegetation succession and lake biogeochemical cycling we have studied palaeoenvironmental change in a suite of lakes across the Arctic in a NERC funded project LAC (Lakes and the Arctic Carbon Cycle). This abstract is focused on a full Holocene sequence from an Alaskan Lake (Woody Bottom Pond), with palaeo records of major elements (scanning XRF), diatoms, pollen, stable isotopes and pigments. The small size of the catchment likely leads to strong coupling between catchment processes such as vegetation succession and fire and aquatic biogeochemical responses. For example the arrival of alder is followed by marked shift in diatom assemblage and pigments associated with changes in N cycling. This approach allows us to assess how catchment change affects aquatic ecosystems and the resultant balance between heterotrophy and autotrophy in arctic lakes over long timescales.
Origin of middle rare earth element enrichments in acid waters of a Canadian high Arctic lake.

NASA Astrophysics Data System (ADS)

Johannesson, Kevin H.; Zhou, Xiaoping

1999-01-01

-Middle rare earth element (MREE) enriched rock-normalized rare earth element (REE) patterns of a dilute acidic lake (Colour Lake) in the Canadian High Arctic, were investigated by quantifying whole-rock REE concentrations of rock samples collected from the catchment basin, as well as determining the acid leachable REE fraction of these rocks. An aliquot of each rock sample was leached with 1 N HNO 3 to examine the readily leachable REE fraction of each rock, and an additional aliquot was leached with a 0.04 M NH 2OH · HCl in 25% (v/v) CH 3COOH solution, designed specifically to reduce Fe-Mn oxides/oxyhydroxides. Rare earth elements associated with the leachates that reacted with clastic sedimentary rock samples containing petrographically identifiable Fe-Mn oxide/oxyhydroxide cements and/or minerals/amorphous phases, exhibited whole-rock-normalized REE patterns similar to the lake waters, whereas whole-rock-normalized leachates from mafic igneous rocks and other clastic sedimentary rocks from the catchment basin differed substantially from the lake waters. The whole-rock, leachates, and lake water REE data support acid leaching or dissolution of MREE enriched Fe-Mn oxides/oxyhydroxides contained and identified within some of the catchment basin sedimentary rocks as the likely source of the unique lake water REE patterns. Solution complexation modelling of the REEs in the inflow streams and lake waters indicate that free metal ions (e.g., Ln 3+, where Ln = any REE) and sulfate complexes (LnSO 4+) are the dominant forms of dissolved REEs. Consequently, solution complexation reactions involving the REEs during weathering, transport to the lake, or within the lake, cannot be invoked to explain the MREE enrichments observed in the lake waters.
The role of metabolism in modulating CO2 fluxes in boreal lakes

NASA Astrophysics Data System (ADS)

Bogard, Matthew J.; del Giorgio, Paul A.

2016-10-01

Lake CO2 emissions are increasingly recognized as an important component of the global CO2 cycle, yet the origin of these emissions is not clear, as specific contributions from metabolism and in-lake cycling, versus external inputs, are not well defined. To assess the coupling of lake metabolism with CO2 concentrations and fluxes, we estimated steady state ratios of gross primary production to respiration (GPP:R) and rates of net ecosystem production (NEP = GPP-R) from surface water O2 dynamics (concentration and stable isotopes) in 187 boreal lakes spanning long environmental gradients. Our findings suggest that internal metabolism plays a dominant role in regulating CO2 fluxes in most lakes, but this pattern only emerges when examined at a resolution that accounts for the vastly differing relationships between lake metabolism and CO2 fluxes. Fluxes of CO2 exceeded those from NEP in over half the lakes, but unexpectedly, these effects were most common and typically largest in a subset ( 30% of total) of net autotrophic lakes that nevertheless emitted CO2. Equally surprising, we found no environmental characteristics that distinguished this category from the more common net heterotrophic, CO2 outgassing lakes. Excess CO2 fluxes relative to NEP were best predicted by catchment structure and hydrologic properties, and we infer from a combination of methods that both catchment inputs and internal anaerobic processes may have contributed this excess CO2. Together, our findings show that the link between lake metabolism and CO2 fluxes is often strong but can vary widely across the boreal biome, having important implications for catchment-wide C budgets.
Anthropic influences on the sedimentation rates of lakes situated in different geographic areas.

PubMed

Simon, Hedvig; Kelemen, Szabolcs; Begy, Róbert-Csaba

2017-07-01

The aim of this study is to determine the effects of natural and anthropic events occurring in the last 30 years in the catchment areas of four Romanian lakes (St. Anna Lake, Red Lake, Vârşolţ Lake and Matiţa Lake) originating from four different geomorphologic areas. A total of eleven sediment cores have been processed for age and sedimentation rate determination using the 210 Pb dating method. Total 210 Pb was measured via alpha spectrometry by 210 Po using PIPS detectors, while supported 210 Pb was measured by 226 Ra using HPGe detectors. Ages and sedimentation rates were calculated using the CRS model. The values of the sedimentation rates have grown multiply in the last three decades: 2.66 times in case of the St. Anna Lake (from 0.06 ± 0.01 g/cm 2 y to 0.16 ± 0.02 g/cm 2 y), up to 6.72 times in case of Red Lake (0.36 ± 0.04 g/cm 2 y to 2.42 ± 0.36 g/cm 2 y), 4.02 times in case of Vârşolţ Lake (04 g/cm 2 y to 1.53 ± 0.18 g/cm 2 y) and up to 16.18 times in case of Matiţa Lake (0.27 ± 0.03 g/cm 2 y to 4.37 ± 0.32). Copyright © 2016 Elsevier Ltd. All rights reserved.
Fate and Transport of Polycyclic Aromatic Hydrocarbons in Upland Irish Headwater Lake Catchments

PubMed Central

Scott, Heidi E. M.; Aherne, Julian; Metcalfe, Chris D.

2012-01-01

Polycyclic aromatic hydrocarbons (PAHs) are a concern due to their carcinogenicity and propensity for transboundary atmospheric transport. Ireland is located on the western periphery of Europe and assumed to receive clean Atlantic air. As such, it has been used as an atmospheric reference for comparison to other regions. Nonetheless, few studies have evaluated concentrations of PAHs within the Irish environment. In the current study, PAHs were measured at five upland (500–800 masl) headwater lake catchments in coastal regions around Ireland, remote from industrial point source emissions. Semipermeable membrane devices were deployed in lakes for a 6-month period in July 2009, and topsoils were sampled from each catchment during October 2010. The concentrations of PAHs were low at most study sites with respect to other temperate regions. Homologue groups partitioned between lake and soil compartments based on their molecular weight were: “lighter” substances, such as Phenanthrene and Fluorene, were found in higher proportions in lakes, whereas “heavier” compounds, such as Chrysene and Benz[a]anthracene, were more prominent in soils. Concentrations of PAHs were highest at the east coast sites, potentially due to contributions from historical transboundary and regional combustion sources. PMID:23346024
Insight into dissolved organic matter fractions in Lake Wivenhoe during and after a major flood.

PubMed

Aryal, Rupak; Grinham, Alistair; Beecham, Simon

2016-03-01

Dissolved organic matter is an important component of biogeochemical processes in aquatic environments. Dissolved organic matter may consist of a myriad of different fractions and resultant processing pathways. In early January 2011, heavy rainfall occurred across South East Queensland, Australia causing significant catchment inflow into Lake Wivenhoe, which is the largest water supply reservoir for the city of Brisbane, Australia. The horizontal and vertical distributions of dissolved organic matter fractions in the lake during the flood period were investigated and then compared with stratified conditions with no catchment inflows. The results clearly demonstrate a large variation in dissolved organic matter fractions associated with inflow conditions compared with stratified conditions. During inflows, dissolved organic matter concentrations in the reservoir were fivefold lower than during stratified conditions. Within the dissolved organic matter fractions during inflow, the hydrophobic and humic acid fractions were almost half those recorded during the stratified period whilst low molecular weight neutrals were higher during the flood period compared to during the stratified period. Information on dissolved organic matter and the spatial and vertical variations in its constituents' concentrations across the lake can be very useful for catchment and lake management and for selecting appropriate water treatment processes.
Mountain lakes of Russian subarctic as markers of air pollution: Acidification, metals and paleoecology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moiseenko, T.I.; Dauvalter, V.A.; Kagan, L.Y.

1996-12-31

The Kola Peninsula mountain lakes reflect a real situation not only of the local air pollution but also polluted transborder emissions from Europe to Arctic and they are of interest for early detection and monitoring for acidification and pollution by heavy metals. Two monitoring mountain lakes had a discrepancy by their resistance to acidification: the Chuna lake is vulnerable and the Chibiny one is not, respectively. Despite the Chuna and Chibiny lakes are close tone of the main heavy metal pollution sources of the Kola Peninsula - smelters of the Severonickel Company, local emissions very slightly affect the mountain lakes,more » because heavily polluted air masses do not rise in altitude. Sulfur deposition on the Chuna lake catchment is 0.4 gSm{sup -2}, Chibiny lake is 0.6 gSm{sup -2}. In comparison with area at the foot of the mountain (less than 200 m above the sea level) sulfur deposition is 1.0-1.5 gSm{sup -2}. Water quality, sediment chemistry, and diatoms in sediment cores were studied.« less
A comparison of charcoal measurements for reconstruction of Mediterranean paleo-fire frequency in the mountains of Corsica

NASA Astrophysics Data System (ADS)

Leys, Bérangère; Carcaillet, Christopher; Dezileau, Laurent; Ali, Adam A.; Bradshaw, Richard H. W.

2013-05-01

Fire-history reconstructions inferred from sedimentary charcoal records are based on measuring sieved charcoal fragment area, estimating fragment volume, or counting fragments. Similar fire histories are reconstructed from these three approaches for boreal lake sediment cores, using locally defined thresholds. Here, we test the same approach for a montane Mediterranean lake in which taphonomical processes might differ from boreal lakes through fragmentation of charcoal particles. The Mediterranean charcoal series are characterized by highly variable charcoal accumulation rates. Results there indicate that the three proxies do not provide comparable fire histories. The differences are attributable to charcoal fragmentation. This could be linked to fire type (crown or surface fires) or taphonomical processes, including charcoal transportation in the catchment area or in the sediment. The lack of correlation between the concentration of charcoal and of mineral matter suggests that fragmentation is not linked to erosion. Reconstructions based on charcoal area are more robust and stable than those based on fragment counts. Area-based reconstructions should therefore be used instead of the particle-counting method when fragmentation may influence the fragment abundance.
Mycobacterium avium subsp. paratuberculosis in Lake Catchments, in River Water Abstracted for Domestic Use, and in Effluent from Domestic Sewage Treatment Works: Diverse Opportunities for Environmental Cycling and Human Exposure

PubMed Central

Pickup, R. W.; Rhodes, G.; Bull, T. J.; Arnott, S.; Sidi-Boumedine, K.; Hurley, M.; Hermon-Taylor, J.

2006-01-01

Mycobacterium avium subsp. paratuberculosis from infected animals enters surface waters and rivers in runoff from contaminated pastures. We studied the River Tywi in South Wales, United Kingdom, whose catchment comprises 1,100 km2 containing more than a million dairy and beef cattle and more than 1.3 million sheep. The River Tywi is abstracted for the domestic water supply. Between August 2002 and April 2003, 48 of 70 (68.8%) twice-weekly river water samples tested positive by IS900 PCR. In river water, the organisms were associated with a suspended solid which was depleted by the water treatment process. Disposal of contaminated slurry back onto the land established a cycle of environmental persistence. A concentrate from 100 liters of finished water tested negative, but 1 of 54 domestic cold water tanks tested positive, indicating the potential for these pathogens to access domestic outlets. In the separate English Lake District region, with hills up to 980 m, tests for M. avium subsp. paratuberculosis in the high hill lakes and sediments were usually negative, but streams and sediments became positive lower down the catchment. Sediments from 9 of 10 major lakes receiving inflow from these catchments were positive, with sediment cores indicating deposition over at least 40 to 50 years. Two of 12 monthly 1-liter samples of effluent and a single 100-liter sample from the Ambleside sewage treatment works were positive for M. avium subsp. paratuberculosis. Since Lake Ambleside discharges into Lake Windermere, which is available for domestic supply, there is a potential for these organisms to cycle within human populations. PMID:16751517
The Lake-Catchment (LakeCat) Dataset: Characterizing landscape features for lake basins within the conterminous USA

EPA Science Inventory

Natural and human-related landscape features influence the ecology and water quality within lakes. It is critical, therefore, to quantify landscape features in a hydrologically meaningful way to effectively manage these important ecosystems. Such summaries of the landscape are of...
Glacial lakes amplify glacier recession in the central Himalaya

NASA Astrophysics Data System (ADS)

King, Owen; Quincey, Duncan; Carrivick, Jonathan; Rowan, Ann

2016-04-01

The high altitude and high latitude regions of the world are amongst those which react most intensely to climatic change. Across the Himalaya glacier mass balance is predominantly negative. The spatial and temporal complexity associated with this ice loss across different glacier clusters is poorly documented however, and our understanding of the processes driving change is limited. Here, we look at the spatial variability of glacier hypsometry and glacial mass loss from three catchments in the central Himalaya; the Dudh Koshi basin, Tama Koshi basin and an adjoining section of the Tibetan Plateau. ASTER and SETSM digital elevation models (2014/15), corrected for elevation dependant biases, co-registration errors and along or cross track tilts, are differenced from Shuttle Radar Topographic Mission (SRTM) data (2000) to yield surface lowering estimates. Landsat data and a hypsometric index (HI), a classification scheme used to group glaciers of similar hypsometry, are used to examine the distribution of glacier area with altitude in each catchment. Surface lowering rates of >3 m/yr can be detected on some glaciers, generally around the clean-ice/debris-cover boundary, where dark but thin surface deposits are likely to enhance ablation. More generally, surface lowering rates of around 1 m/yr are more pervasive, except around the terminus areas of most glaciers, emphasising the influence of a thick debris cover on ice melt. Surface lowering is only concentrated at glacier termini where glacial lakes have developed, where surface lowering rates are commonly greater than 2.5 m/yr. The three catchments show contrasting hypsometric distributions, which is likely to impact their future response to climatic changes. Glaciers of the Dudh Koshi basin store large volumes of ice at low elevation (HI > 1.5) in long, debris covered tongues, although their altitudinal range is greatest given the height of mountain peaks in the catchment. In contrast, glaciers of the Tama Koshi store large amounts of ice in broad accumulation zones and are more equidimensional (HI -1.2 to 1.2). Glaciers flowing onto the Tibetan Plateau have a similar hypsometric distribution to glaciers of the Dudh Koshi, but terminate at a higher altitude overall, approximately 500 m higher than glaciers of the Dudh Koshi or Tama Koshi. We estimate the approximate Equilibrium Line Altitudes (ELA) of the last 15 years to be above a substantial portion (66%- Dudh Koshi; 87%- Tama Koshi; 83% Tibetan Plateau) of the glacierised area for all three catchments. Future ice recession may therefore be governed primarily by glacier hypsometry, but is likely to be amplified by the continued development of new, or growth of current glacial lakes.
Application of Classification Algorithm of Machine Learning and Buffer Analysis in Torism Regional Planning

NASA Astrophysics Data System (ADS)

Zhang, T. H.; Ji, H. W.; Hu, Y.; Ye, Q.; Lin, Y.

2018-04-01

Remote Sensing (RS) and Geography Information System (GIS) technologies are widely used in ecological analysis and regional planning. With the advantages of large scale monitoring, combination of point and area, multiple time-phases and repeated observation, they are suitable for monitoring and analysis of environmental information in a large range. In this study, support vector machine (SVM) classification algorithm is used to monitor the land use and land cover change (LUCC), and then to perform the ecological evaluation for Chaohu lake tourism area quantitatively. The automatic classification and the quantitative spatial-temporal analysis for the Chaohu Lake basin are realized by the analysis of multi-temporal and multispectral satellite images, DEM data and slope information data. Furthermore, the ecological buffer zone analysis is also studied to set up the buffer width for each catchment area surrounding Chaohu Lake. The results of LUCC monitoring from 1992 to 2015 has shown obvious affections by human activities. Since the construction of the Chaohu Lake basin is in the crucial stage of the rapid development of urbanization, the application of RS and GIS technique can effectively provide scientific basis for land use planning, ecological management, environmental protection and tourism resources development in the Chaohu Lake Basin.
Freshwater bacterioplankton richness in oligotrophic lakes depends on nutrient availability rather than on species–area relationships

PubMed Central

Logue, Jürg Brendan; Langenheder, Silke; Andersson, Anders F; Bertilsson, Stefan; Drakare, Stina; Lanzén, Anders; Lindström, Eva S

2012-01-01

A central goal in ecology is to grasp the mechanisms that underlie and maintain biodiversity and patterns in its spatial distribution can provide clues about those mechanisms. Here, we investigated what might determine the bacterioplankton richness (BR) in lakes by means of 454 pyrosequencing of the 16S rRNA gene. We further provide a BR estimate based upon a sampling depth and accuracy, which, to our knowledge, are unsurpassed for freshwater bacterioplankton communities. Our examination of 22 669 sequences per lake showed that freshwater BR in fourteen nutrient-poor lakes was positively influenced by nutrient availability. Our study is, thus, consistent with the finding that the supply of available nutrients is a major driver of species richness; a pattern that may well be universally valid to the world of both micro- and macro-organisms. We, furthermore, observed that BR increased with elevated landscape position, most likely as a consequence of differences in nutrient availability. Finally, BR decreased with increasing lake and catchment area that is negative species–area relationships (SARs) were recorded; a finding that re-opens the debate about whether positive SARs can indeed be found in the microbial world and whether positive SARs can in fact be pronounced as one of the few ‘laws' in ecology. PMID:22170419
Non-Linear Response to Holocene Insolation Forcing Recorded by High-Resolution Lake Sediment Records Across Iceland

NASA Astrophysics Data System (ADS)

Geirsdottir, A.; Miller, G. H.; Axford, Y.

2009-12-01

Many Icelandic lakes have sedimentation rates in excess of 1 m ka-1 throughout the Holocene. Such high rates offer the potential for decadally resolved (or better) records of environmental change at this sensitive North Atlantic site. Abundant well-defined tephra provide a secure geochronology. The fidelity of the common climate proxies biogenic silica (BSi) and total organic carbon (TOC), was tested by comparing these proxies in three lakes with very different catchment characteristics. Hestvatn (HST, 60 m deep) in southern Iceland receives overflow from a large river originating in the glaciated highlands of central Iceland, whereas the nearby lake Vestra Gislholtsvatn (VGHV, 15 m deep) has a small, low elevation catchment without glaciers. Haukadalsvatn (HAK, 42 m deep), in northwestern Iceland, has a large, high relief catchment. The BSi record from HAK has been shown to reflect April-May temperatures, with BSi highest when spring temperatures are at their maximum. The first- and second-order trends in BSi are similar in all three lakes for most of the Holocene. This supports the contention that BSi reflects primary productivity, and is less influenced by changes in sedimentation rate. In all three lakes, BSi reaches a maximum value shortly after 8 ka, and then declines gradually toward present, reflecting a relatively late Holocene thermal maximum, potentially due to the influence of meltwater from the lingering Laurentide Ice Sheet. A steady reduction in summer insolation determines this first-order trend towards lower BSi through the middle and late Holocene. Large, abrupt departures from the overall decrease in BSi characterize all three records after 8 ka. Following each rapid BSi decrease, BSi usually exhibits a step-function change, re-equilibrating at a lower BSi value. Some of the strongest departures (ca. 6 ka, 4 to 4.5 ka and ca. 3 ka) may be related to Icelandic volcanism, but the lack of a full recovery to pre-existing values after the eruptions suggests a change in state occurred in the catchments of the lakes. TOC reflects the balance between changes in primary productivity within the lakes, which appears to dominate the early and middle Holocene, and the flux of soil carbon to the lake during periods of catchment instability that dominates the record after ~2.5 ka. In HAK TOC the flux of soil carbon to the lake is high when cold summers are accompanied by dry, windy winters. The two southern lakes exhibit a substantial overprinting after settlement, although the northern and southern records start to depart ca. 1.5 ka, well before settlement, possibly reflecting an earlier onset of late Holocene cooling off northwest Iceland than in the south where the Irminger current maintains warmer coastal temperatures.
The impact of climate and environmental processes on vegetation pattern in the Czechowskie lake catchment Czechowo Region (Northern Tuchola Pinewoods) during the Younger Dryas cooling

NASA Astrophysics Data System (ADS)

Noryśkiewicz, Agnieszka Maria; Kramkowski, Mateusz; Słowiński, Michał; Zawiska, Izabela; Lutyńska, Monika; Błaszkiewicz, Mirosław; Brauer, Achim

2014-05-01

Czechowskie lake is located in the northern part of the Tuchola Pinewoods District (Northern Poland) in a young glacial landscape. At present, the majority of the area is forested or used for agricultural purposes, but among them a high amount of basins filled with biogenic sediments are present. This area is very suitable for the postglacial vegetation development investigation because of the LST ash and laminated sediments which we found in the Trzechowskie palaeolake and Czechowskie Lake (Wulf et. all 2013). The aim of the research was to reconstruct the past landscape and vegetation response to Younger Dryas cooling and we present the results of the palinological analysis done for 6 core of biogenic sediments. Our main objective was to determine whether local factors such as topography and soil cover have a significant impact on the vegetation, eutrophy and sedimentation rate at this time. In the lake Czechowskie lake catchment we have six cores that cover postglacial succession (Lake Czechowskie small basin - profile JC-12-s; Lake Czechowskiego terrace - profile TK; Lake Czechowskie vicinity - profile "Oko and Cz/80; Trzechowskie paleolake - profile T/trz; Valley between paleolake Trzechowskie and Lake Czechowskie - profile DTCZ-4). The paleoecological research carried out involved an analysis of pollen, macrofossils, Cladocera, diatom, loss-on-ignition and CaCO3 content. The results show, that the dominant plant communities during the Youngers Dryas in the region nearby Lake Czechowskie are heliophytes xeric herb vegetation with juniper (Juniperus communis) shrubs and birch (Betula) and pine (Pinus sylvestris). In the pollen diagrams there was the difference noted in the participation of the dominant pollen, the juniper pollen was always high but varied from 18 to 37%, birch average pollen share was between 17-27%. The thickness and type of the sediment accumulated in Younger Dryas in the presented profiles differs significantly. In the profiles which comprise the whole succession of the Younger Dryas ("Oko", T/trz, JC-12-s) the thickest sediments are in "Oko" profile (1 m) and thinness in the profile from the lake Czechowskie small basin JC-12-s (45 cm). In Cz/80 profile the lake sedimentation stopped at the beginning of the Younger Dryas. The conclusion is that the all pollen results show the same main patterns during the Younger Dryas cooling. Nevertheless the local factors had an influence on the vegetation and this reflected in the different participation of species among sites. The sediment type and sedimentation rate was strongly influenced by the local factors. The combined approach of fossil pollen data and contemporary distribution of substrate and relief allowed to reconstruct of Younger Dryas vegetation patterns and relief in Czechowskie lake catchment Czechowo region. This study is a contribution to the Virtual Institute of Integrated Climate and Landscape Evolution Analysis -ICLEA- of the Helmholtz Association. The research was supported by the National Science Centre Poland (grants No. NN 306085037 and NCN 2011/01/B/ST10/07367). Literature: Wulf S., Ott F., Słowiński M., Noryśkiewicz A. M., Drager N., Martin-Puertas C., Czymzik M., Neugebauer I., Dulski P., Bourne A., Błaszkiewicz M., Brauer A. 2013. Tracing the Laacher See Tephra in the varved sediment record of the Trzechowskie palaeolake in central Northern Poland. Quaternary Science Reviews, s. 129-139.
Influence of catchment vegetation on mercury accumulation in lake sediments from a long-term perspective.

PubMed

Rydberg, Johan; Rösch, Manfred; Heinz, Emanuel; Biester, Harald

2015-12-15

Organic matter (OM) cycling has a large impact on the cycling of mercury (Hg) in the environment. Hence, it is important to have a thorough understanding on how changes in, e.g., catchment vegetation - through its effect on OM cycling - affect the behavior of Hg. To test whether shifts in vegetation had an effect on Hg-transport to lakes we investigated a sediment record from Herrenwieser See (Southern Germany). This lake has a well-defined Holocene vegetation history: at ~8700years BP Corylus avellana (hazel) was replaced by Quercus robur (oak), which was replaced by Abies alba (fir) and Fagus sylvatica (beech) ~5700years BP). We were particularly interested in testing if coniferous vegetation leads to a larger export of Hg to aquatic systems than deciduous vegetation. When hazel was replaced by oak, reduced soil erosion and increased transport of DOM-bound mercury from the catchment resulted in increases in both Hg-concentrations and accumulation rates (61ngg(-1) and 5.5ngcm(-2)yr.(-)(1) to 118ngg(-1) and 8.5ngcm(-2)yr.(-)(1)). However, even if Hg-concentrations increased also in association with the introduction of fir and beech (173ngg(-1)), as a result of higher Hg:C, there was no increase in Hg-accumulation rates (7.6ngcm(-2)yr.(-)(1)), because of a decreased input of OM. At around 2500years BP Hg-accumulation rates and Hg-concentration indicated an additional input of Hg to the sediment (316ngg(-1) and 10.3ngcm(-2)yr.(-)(1)), which might be due to increased human activities in the area, e.g., forest burning or mining. Our results contrast those of several paired-catchment studies that suggest a higher release of Hg from coniferous than deciduous forest, and there is a need for studies with a long-term perspective to increase our understanding of the effects of slow and gradual processes on mercury cycling. Copyright © 2015 Elsevier B.V. All rights reserved.
Water quality and agricultural practices: the case study of southern Massaciuccoli reclaimed land (Tuscany, Italy)

NASA Astrophysics Data System (ADS)

Pistocchi, Chiara; Baneschi, Ilaria; Basile, Paolo; Cannavò, Silvia; Guidi, Massimo; Risaliti, Rosalba; Rossetto, Rudy; Sabbatini, Tiziana; Silvestri, Nicola; Bonari, Enrico

2010-05-01

Owing to increasing anthropogenic impacts, lagoons and wetlands are being exposed to environmental degradation. Therefore, the sustainable management of these environmental resources is a fundamental issue to maintain either the ecosystems and the human activity. The Massaciuccoli Lake is a coastal lake of fresh to brackish water surrounded by a marsh, which drains a total catchment of about 114 km2. Large part of the basin has been reclaimed since 1930 by means of pumping stations forcing water from the drained areas into the lake. The system is characterized by: high complexity of the hydrological setting; subsidence of the peaty soils in the reclaimed area (2 to 3 m in 70 years), that left the lake perched; reclaimed land currently devoted mainly to conventional agriculture (e.g.: maize monoculture) along with some industrial sites, two sewage treatment plants and some relevant urban settlements; social conflicts among different land users because of the impact on water quality and quantity. The interaction between such a fragile natural system and human activities leads to an altered ecological status mainly due to eutrophication and water salinisation. Hence, the present work aims at identifying and assessing the sources of nutrients (phosphorous in particular) into the lake, and characterising land use and some socio-economic aspects focusing on agricultural systems, in order to set up suitable mitigation measures. Water quantity and quality in the most intensively cultivated sub-catchment, placed 0.5 to 3 m under m.s.l. were monitored in order to underlain the interaction between water and its nutrient load. Questionnaires and interviews to farmers were conducted to obtain information about agricultural practices, farm management, risks and constraints for farming activities. The available information about the natural system and land use were collected and organised in a GIS system: a conceptual model of surface water hydrodinamics was build up and 14 sampling points were monitored monthly during 2008-2009. The main water physical and chemical parameters, including nutrients, as well as the principal soil types within the sub-catchment were analysed. First results point out: the reclaimed land presents a dense drainage network hydraulically interconnected with the shallow aquifer; surface waters present a high chemical heterogeneity: three main hydrochemical facies were identified and compared with nutrients contents and soil chemistry; artificially induced recharge to the reclaimed land aquifer occurs by means of lake water infiltration. This forces the pumping stations to remove an additional amount of water in order to allow land cultivation; the water salinity in the drainage network may increase during summer period. This could be related both to irrigation using lake water and a further contribution due to evapotranspiration processes; agricultural land use changed during the last 15 years, and shifted to less intensive farming practices. Fertilization levels dropped from 200 and 150 to 100 and 50 kg/ha N and P2O5 respectively, and the irrigated area decreased from 50% to 40% of the total utilised agricultural area; in the low land peaty area, the higher content of sulphate and phosphate in the drainage water supports the hypothesis that peat degradation could be a relevant source of nutrients. As a result, the impact of fertilizer use on the water quality is limited, while land management (e.g. water use and land reclamation) constitutes the key issue. Therefore, local stakeholders participation, farmers above all, should be supported in future management and planning actions in order to adapt socio-economic needs with the peculiar biophysical conditions.
Sulfur isotope dynamics in a high-elevation catchment, West Glacier Lake, Wyoming

Treesearch

J. B. Finley; J. I. Drever; J. T. Turk

1995-01-01

Stable isotopes of S are used in conjunction with dissolved SO2-|4 concentrations to evaluate the utility of Ã¤34S ratios in tracing contributions of bedrock-derived S to SO2-|4 in runoff. Water samples were collected over the annual hydrograph from two tributaries in the West Glacier Lake, Wyoming, catchment. Concentrations of SO2-|4 ranged from 12.6 to 43.0 Ãeq L-1;...
Hydrologic response to modeled snowmelt input in alpine catchments in the Southwestern United States

NASA Astrophysics Data System (ADS)

Driscoll, J. M.; Molotch, N. P.; Jepsen, S. M.; Meixner, T.; Williams, M. W.; Sickman, J. O.

2012-12-01

Snowmelt from high elevation catchments is the primary source of water resources in the Southwestern United States. Timing and duration of snowmelt and resulting catchment response can show the physical and chemical importance of storage at the catchment scale. Storage of waters in subsurface materials provides a physical and chemical buffer to hydrologic input variability. We expect the hydrochemistry of catchments with less storage capacity will more closely reflect input waters than a catchment with more storage and therefore more geochemical evolution of waters. Two headwater catchments were compared for this study; Emerald Lake Watershed (ELW) in the southern Sierra Nevada and Green Lake 4 (GL4) in the Colorado Front Range. These sites have geochemically similar granitic terrane, and negligible evaporation and transpiration due to their high-elevation setting. Eleven years of data (1996-2006) from spatially-distributed snowmelt models were spatially and temporally aggregated to generate daily values of snowmelt volume for each catchment area. Daily storage flux was calculated as the difference between snowmelt input and catchment outflow at a daily timestep, normalized to the catchment area. Daily snowmelt values in GL4 are more consistent (the annual standard deviation ranged from 0.19 to 0.76 cm) than the daily snowmelt in ELW (0.60 to 1.04 cm). Outflow follows the same trend, with an even narrower range of standard deviations from GL4 (0.27 to 0.54 cm) compared to the standard deviation of outflow in ELW (0.38 to 0.98 cm). The dampening of the input variability could be due to storage in the catchment; the larger effect would mean a larger storage capacity in the catchment. Calculations of storage flux (the input snowmelt minus the output catchment discharge) show the annual sum of water into storage in ELW ranges from -0.9200 to 1.1124 meters, in GL4 the ranger is narrower, from -0.655 to 0.0992 meters. Cumulative storage for each year can be negative (more water leaving the system than entering; storage loss) or positive (more water coming into the system than leaving; storage gain). The cumulative storage for all years in GL4 show a similar positive trend from day of year 60 through 150, followed by a decrease to the end of the snowmelt season. Only two years (1997 and 2005) in GL4 were calculated to cumulatively gain storage water, the other nine years lost stored water to outflow. The cumulative storage annual data in ELW do not show as strong of a trend for all years. ELW also a different distribution of cumulative storage values; with four years showing a cumulative loss and seven years showing a gain in stored water. This could show a depletion of stored water, an underestimate of snowmelt or a connection to deeper flowpaths. Mass-balance inverse geochemical models will be used to determine the hydrochemical connectivity or lack of connectivity of snowmelt to outflow relative to the physical calculations. Initial hydrochemical results show generally higher concentrations of solutes from GL4 outflow, which may show more contribution from stored waters.

Holocene glacier activity reconstructed from proglacial lake Gjøavatnet on Amsterdamøya, NW Svalbard

NASA Astrophysics Data System (ADS)

de Wet, Gregory A.; Balascio, Nicholas L.; D'Andrea, William J.; Bakke, Jostein; Bradley, Raymond S.; Perren, Bianca

2018-03-01

Well-dated and highly resolved paleoclimate records from high latitudes allow for a better understanding of past climate change. Lake sediments are excellent archives of environmental change, and can record processes occurring within the catchment, such as the growth or demise of an upstream glacier. Here we present a Holocene-length, multi-proxy lake sediment record from proglacial lake Gjøavatnet on the island of Amsterdamøya, northwest Svalbard. Today, Gjøavatnet receives meltwater from the Annabreen glacier and contains a record of changes in glacier activity linked to regional climate conditions. We measured changes in organic matter content, dry bulk density, bulk carbon isotopes, elemental concentrations via Itrax core-scanning, and diatom community composition to reconstruct variability in glacier extent back through time. Our reconstruction indicates that glacially derived sedimentation in the lake decreased markedly at ∼11.1 cal kyr BP, although a glacier likely persisted in the catchment until ∼8.4 cal kyr BP. During the mid-Holocene (∼8.4-1.0 cal kyr BP) there was significantly limited glacial influence in the catchment and enhanced deposition of organic-rich sediment in the lake. The deposition of organic rich sediments during this time was interrupted by at least three multi-centennial intervals of reduced organic matter accumulation (∼5.9-5.0, 2.7-2.0, and 1.7-1.5 cal kyr BP). Considering our chronological information and a sedimentological comparison with intervals of enhanced glacier input, we interpret these intervals not as glacial advances, but rather as cold/dry episodes that inhibited organic matter production in the lake and surrounding catchment. At ∼1.0 cal kyr BP, input of glacially derived sediment to Gjøavatnet abruptly increased, representing the rapid expansion of the Annabreen glacier.
Spatial and temporal variations of Rb/Sr ratios of the bulk surface sediments in Lake Qinghai

PubMed Central

2010-01-01

The Rb/Sr ratios of lake sediments have been suggested as indicators of weathering intensity by increasing work. However, the geochemistry of Rb/Sr ratios of lake sediments is variable between different lakes. In this study, we investigated the spatial and temporal patterns of Rb/Sr ratios, as well as those of other major elements in surface sediments of Lake Qinghai. We find that the spatial pattern of Rb/Sr ratios of the bulk sediments correlates well with that of the mass accumulation rate, and those of the terrigenous fractions, e.g., SiO2, Ti, and Fe. The temporal variations of Rb/Sr ratios also synchronize with those of SiO2, Ti, and Fe of each individual core. These suggest that Rb/Sr ratios of the surface sediments are closely related to terrigenous input from the catchment. Two out of eight cores show similar trends between Rb/Sr ratios and precipitation indices on decadal scales; however, the other cores do not show such relationship. The result of this study suggests that physical weathering and chemical weathering in Lake Qinghai catchment have opposite influence on Rb/Sr ratios of the bulk sediments, and they compete in dominating the Rb/Sr ratios of lake sediments on different spatial and temporal scales. Therefore, it is necessary to study the geochemistry of Rb/Sr ratio of lake sediments (especially that on short term timescales) particularly before it is used as an indicator of weathering intensity of the catchment. PMID:20615264
Lake-specific responses to elevated atmospheric nitrogen deposition in the Colorado Rocky Mountains, U.S.A.

USGS Publications Warehouse

Nydick, K.R.; LaFrancois, B.M.; Baron, Jill S.; Johnson, B.M.

2003-01-01

We explored variability among subalpine lakes sharing very similar climate and atmospheric conditions, but differing in watershed characteristics, hydrology, and food web structure. Special attention was given to nitrogen (N) dynamics because the study area receives some of the highest levels of atmospheric N deposition in the Rocky Mountains. We asked if the effect of regional N deposition would be manifested uniformly among neighboring lakes both in terms of ambient conditions and responses to greater nutrient inputs. Catchment vegetation appeared to be the main determinant of ambient nitrate (NO3), phosphate (PO4), and dissolved organic carbon (DOC) concentrations, although in-lake differences in recycling produced variable and contrasting NH4 levels. Phytoplankton chlorophyll a temporarily responded to early season NO3 peaks in the lakes with rocky watersheds, but chlorophyll means over the ice-free season were remarkably similar among lakes despite differences in both nutrient supply and zooplankton grazing. In most cases, phosphorus was limiting to phytoplankton growth, although the importance of N deficiencies was greater in lakes with forested watersheds and fringing wetlands.
Lake-specific responses to elevated atmospheric nitrogen deposition in the Colorado Rocky Mountains, U.S.A

USGS Publications Warehouse

Nydick, K.R.; LaFrancois, B.M.; Baron, Jill S.; Johnson, B.M.

2003-01-01

We explored variability among subalpine lakes sharing very similar climate and atmospheric conditions, but differing in watershed characteristics, hydrology, and food web structure. Special attention was given to nitrogen (N) dynamics because the study area receives some of the highest levels of atmospheric N deposition in the Rocky Mountains. We asked if the effect of regional N deposition would be manifested uniformly among neighboring lakes both in terms of ambient conditions and responses to greater nutrient inputs. Catchment vegetation appeared to be the main determinant of ambient nitrate (NO3), phosphate (PO4), and dissolved organic carbon (DOC) concentrations, although in-lake differences in recycling produced variable and contrasting NH4 levels. Phytoplankton chlorophyll atemporarily responded to early season NO3 peaks in the lakes with rocky watersheds, but chlorophyll means over the ice-free season were remarkably similar among lakes despite differences in both nutrient supply and zooplankton grazing. In most cases, phosphorus was limiting to phytoplankton growth, although the importance of N deficiencies was greater in lakes with forested watersheds and fringing wetlands.
Environmental changes and the Migration Period in northern Germany as reflected in the sediments of Lake Dudinghausen

NASA Astrophysics Data System (ADS)

Dreßler, Mirko; Selig, Uwe; Dörfler, Walter; Adler, Sven; Schubert, Hendrik; Hübener, Thomas

2006-07-01

Paleolimnological techniques were used to identify environmental changes in and around Lake Dudinghausen (northern Germany) over the past 4800 yr. Diatom-inferred total phosphorus (DI-TP) changes identify four phases of high nutrient levels (2600-2200 BC, 1050-700 BC, 500 BC-AD 100 and AD 1850-1970). During these high DI-TP phases, fossil pollen, sediment geochemistry and archaeological records indicate human activities in the lake catchment. Although the same paleo-indicators suggest increased human settlement and agriculture activity during the late Slavonic Age, the Medieval Time and the Modern Time (AD 1000-1850), DI-TP levels were low during this period. In the sediments, iron and total phosphorus were high from ˜AD 100 to 1850, likely due to increased inflow of iron-rich groundwater into the lake. Increased iron input would have lead to a simultaneous binding and precipitation of phosphate in the upper sediment and overlying water column. As a result, anthropogenic impact on Lake Dudinghausen was masked by these phosphorus-controlling processes from AD 1000 to 1850 and was not evident by means of DI-TP. In accordance with fossil pollen, sediment geochemistry and limited archaeological records, DI-TP levels were low from AD 100-1000. Groundwater levels likely rose during this period as the climate gradually changed toward colder and/or moister conditions. Such climate change likely led to reduced settlement activities and forest regeneration in the catchment area. Our results are concordant with similar studies from central Europe which indicate rapid decreasing settlement activities from AD 100 to 1000.
Changes in water and sediment exchange between the Changjiang River and Poyang Lake under natural and anthropogenic conditions, China.

PubMed

Gao, Jian Hua; Jia, Jianjun; Kettner, Albert J; Xing, Fei; Wang, Ya Ping; Xu, Xia Nan; Yang, Yang; Zou, Xin Qing; Gao, Shu; Qi, Shuhua; Liao, Fuqiang

2014-05-15

To study the fluvial interaction between Changjiang River and Poyang Lake, we analyze the observed changes of riverine flux of the mid-upstream of Changjiang River catchment, the five river systems of Poyang Lake and Poyang Lake basin. Inter-annual and seasonal variations of the water discharge and sediment exchange processes between Changjiang River and Poyang Lake are systematically explored to determine the influence of climate change as well as human impact (especially the Three Gorges Dam (TGD)). Results indicate that climate variation for the Changjiang catchment and Poyang Lake watershed is the main factor determining the changes of water exchanges between Changjiang River and Poyang Lake. However, human activities (including the emplacement of the TGD) accelerated this rate of change. Relative to previous years (1956-1989), the water discharge outflow from Poyang Lake during the dry season towards the Changjiang catchment increased by 8.98 km(3)y(-1) during 2003-2010. Evidently, the water discharge flowing into Poyang Lake during late April-late May decreased. As a consequence, water storage of Poyang Lake significantly reduced during late April-late May, resulting in frequent spring droughts after 2003. The freshwater flux of Changjiang River towards Poyang Lake is less during the flood season as well, significantly lowering the magnitude and frequency of the backflow of the Changjiang River during 2003-2010. Human activities, especially the emplacement and operation of the TGD and sand mining at Poyang Lake impose a major impact on the variation of sediment exchange between Changjiang main river and Poyang Lake. On average, sediments from Changjiang River deposited in Poyang Lake before 2000. After 2000, Changjiang River no longer supplied sediment to Poyang Lake. As a consequence, the sediment load of Changjiang River entering the sea increasingly exists of sediments from Lake Poyang during 2003-2010. As a result, Poyang Lake converted from a depositional to an erosional system, with a gross sediment loss of 120.19 Mty(-1) during 2001-2010, including sand mining. Copyright © 2014 Elsevier B.V. All rights reserved.
Linkage between Three Gorges Dam impacts and the dramatic recessions in China’s largest freshwater lake, Poyang Lake

PubMed Central

Mei, Xuefei; Dai, Zhijun; Du, Jinzhou; Chen, Jiyu

2015-01-01

Despite comprising a small portion of the earth’s surface, lakes are vitally important for global ecosystem cycling. However, lake systems worldwide are extremely fragile, and many are shrinking due to changing climate and anthropogenic activities. Here, we show that Poyang Lake, the largest freshwater lake in China, has experienced a dramatic and prolonged recession, which began in late September of 2003. We further demonstrate that abnormally low levels appear during October, 28 days ahead of the normal initiation of the dry season, which greatly imperiled the lake’s wetland areas and function as an ecosystem for wintering waterbirds. An increase in the river-lake water level gradient induced by the Three Gorges Dam (TGD) altered the lake balance by inducing greater discharge into the Changjiang River, which is probably responsible for the current lake shrinkage. Occasional episodes of arid climate, as well as local sand mining, will aggravate the lake recession crisis. Although impacts of TGD on the Poyang Lake recession can be overruled by episodic extreme droughts, we argue that the average contributions of precipitation variation, human activities in the Poyang Lake catchment and TGD regulation to the Poyang Lake recession can be quantified as 39.1%, 4.6% and 56.3%, respectively. PMID:26657816
Linkage between Three Gorges Dam impacts and the dramatic recessions in China’s largest freshwater lake, Poyang Lake

NASA Astrophysics Data System (ADS)

Mei, Xuefei; Dai, Zhijun; Du, Jinzhou; Chen, Jiyu

2015-12-01

Despite comprising a small portion of the earth’s surface, lakes are vitally important for global ecosystem cycling. However, lake systems worldwide are extremely fragile, and many are shrinking due to changing climate and anthropogenic activities. Here, we show that Poyang Lake, the largest freshwater lake in China, has experienced a dramatic and prolonged recession, which began in late September of 2003. We further demonstrate that abnormally low levels appear during October, 28 days ahead of the normal initiation of the dry season, which greatly imperiled the lake’s wetland areas and function as an ecosystem for wintering waterbirds. An increase in the river-lake water level gradient induced by the Three Gorges Dam (TGD) altered the lake balance by inducing greater discharge into the Changjiang River, which is probably responsible for the current lake shrinkage. Occasional episodes of arid climate, as well as local sand mining, will aggravate the lake recession crisis. Although impacts of TGD on the Poyang Lake recession can be overruled by episodic extreme droughts, we argue that the average contributions of precipitation variation, human activities in the Poyang Lake catchment and TGD regulation to the Poyang Lake recession can be quantified as 39.1%, 4.6% and 56.3%, respectively.
Net atmospheric mercury deposition to Svalbard: Estimates from lacustrine sediments

NASA Astrophysics Data System (ADS)

Drevnick, Paul E.; Yang, Handong; Lamborg, Carl H.; Rose, Neil L.

2012-11-01

In this study we used lake sediments, which faithfully record Hg inputs, to derive estimates of net atmospheric Hg deposition to Svalbard, Norwegian Arctic. With the exception of one site affected by local pollution, the study lakes show twofold to fivefold increases in sedimentary Hg accumulation since 1850, likely due to long-range atmospheric transport and deposition of anthropogenic Hg. Sedimentary Hg accumulation in these lakes is a linear function of the ratio of catchment area to lake area, and we used this relationship to model net atmospheric Hg flux: preindustrial and modern estimates are 2.5 ± 3.3 μg m-2 y-1 and 7.0 ± 3.0 μg m-2 y-1, respectively. The modern estimate, by comparison with data for Hg wet deposition, indicates that atmospheric mercury depletion events (AMDEs) or other dry deposition processes contribute approximately half (range 0-70%) of the net flux. Hg from AMDEs may be moving in significant quantities into aquatic ecosystems, where it is a concern because of contamination of aquatic food webs.
Attributes for MRB_E2RF1 Catchments by Major River Basins in the Conterminous United States: Physiographic Provinces

USGS Publications Warehouse

Wieczorek, Michael; LaMotte, Andrew E.

2010-01-01

This tabular data set represents the area of each physiographic province (Fenneman and Johnson, 1946) in square meters, compiled for every MRB_E2RF1 catchment of selected Major River Basins (MRBs, Crawford and others, 2006). The source data are from Fenneman and Johnson's Physiographic Provinces of the United States, which is based on 8 major divisions, 25 provinces, and 86 sections representing distinctive areas having common topography, rock type and structure, and geologic and geomorphic history (Fenneman and Johnson, 1946).The MRB_E2RF1 catchments are based on a modified version of the U.S. Environmental Protection Agency's (USEPA) ERF1_2 and include enhancements to support national and regional-scale surface-water quality modeling (Nolan and others, 2002; Brakebill and others, 2011). Data were compiled for every MRB_E2RF1 catchment for the conterminous United States covering New England and Mid-Atlantic (MRB1), South Atlantic-Gulf and Tennessee (MRB2), the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy (MRB3), the Missouri (MRB4), the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf (MRB5), the Rio Grande, Colorado, and the Great basin (MRB6), the Pacific Northwest (MRB7) river basins, and California (MRB8).
Attributes for MRB_E2RF1 Catchments by Major River Basins in the Conterminous United States: Bedrock Geology

USGS Publications Warehouse

Wieczorek, Michael; LaMotte, Andrew E.

2010-01-01

This tabular data set represents the area of bedrock geology types in square meters compiled for every catchment of MRB_E2RF1 catchments for Major River Basins (MRBs, Crawford and others, 2006). The source data set is the "Geology of the Conterminous United States at 1:2,500,000 Scale--A Digital Representation of the 1974 P.B. King and H.M. Beikman Map" (Schuben and others, 1994). The MRB_E2RF1 catchments are based on a modified version of the U.S. Environmental Protection Agency's (USEPA) ERF1_2 and include enhancements to support national and regional-scale surface-water quality modeling (Nolan and others, 2002; Brakebill and others, 2011). Data were compiled for every MRB_E2RF1 catchment for the conterminous United States covering New England and Mid-Atlantic (MRB1), South Atlantic-Gulf and Tennessee (MRB2), the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy (MRB3), the Missouri (MRB4), the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf (MRB5), the Rio Grande, Colorado, and the Great basin (MRB6), the Pacific Northwest (MRB7) river basins, and California (MRB8).
Investigation of the complexity of streamflow fluctuations in a large heterogeneous lake catchment in China

NASA Astrophysics Data System (ADS)

Ye, Xuchun; Xu, Chong-Yu; Li, Xianghu; Zhang, Qi

2018-05-01

The occurrence of flood and drought frequency is highly correlated with the temporal fluctuations of streamflow series; understanding of these fluctuations is essential for the improved modeling and statistical prediction of extreme changes in river basins. In this study, the complexity of daily streamflow fluctuations was investigated by using multifractal detrended fluctuation analysis (MF-DFA) in a large heterogeneous lake basin, the Poyang Lake basin in China, and the potential impacts of human activities were also explored. Major results indicate that the multifractality of streamflow fluctuations shows significant regional characteristics. In the study catchment, all the daily streamflow series present a strong long-range correlation with Hurst exponents bigger than 0.8. The q-order Hurst exponent h( q) of all the hydrostations can be characterized well by only two parameters: a (0.354 ≤ a ≤ 0.384) and b (0.627 ≤ b ≤ 0.677), with no pronounced differences. Singularity spectrum analysis pointed out that small fluctuations play a dominant role in all daily streamflow series. Our research also revealed that both the correlation properties and the broad probability density function (PDF) of hydrological series can be responsible for the multifractality of streamflow series that depends on watershed areas. In addition, we emphasized the relationship between watershed area and the estimated multifractal parameters, such as the Hurst exponent and fitted parameters a and b from the q-order Hurst exponent h( q). However, the relationship between the width of the singularity spectrum (Δ α) and watershed area is not clear. Further investigation revealed that increasing forest coverage and reservoir storage can effectively enhance the persistence of daily streamflow, decrease the hydrological complexity of large fluctuations, and increase the small fluctuations.
Landscape drivers of regional variation in the relationship between total phosphorus and chlorophyll in lakes

USGS Publications Warehouse

Wagner, Tyler; Soranno, Patricia A.; Webster, Katherine E.; Cheruvelil, Kendra Spence

2011-01-01

1. For north temperate lakes, the well-studied empirical relationship between phosphorus (as measured by total phosphorus, TP), the most commonly limiting nutrient and algal biomass (as measured by chlorophyll a, CHL) has been found to vary across a wide range of landscape settings. Variation in the parameters of these TP–CHL regressions has been attributed to such lake variables as nitrogen/phosphorus ratios, organic carbon and alkalinity, all of which are strongly related to catchment characteristics (e.g. natural land cover and human land use). Although this suggests that landscape setting can help to explain much of the variation in ecoregional TP–CHL regression parameters, few studies have attempted to quantify relationships at an ecoregional spatial scale.2. We tested the hypothesis that lake algal biomass and its predicted response to changes in phosphorus are related to both local-scale features (e.g. lake and catchment) and ecoregional-scale features, all of which affect the availability and transport of covarying solutes such as nitrogen, organic carbon and alkalinity. Specifically, we expected that land use and cover, acting at both local and ecoregional scales, would partially explain the spatial pattern in parameters of the TP–CHL regression.3. We used a multilevel modelling framework and data from 2105 inland lakes spanning 35 ecoregions in six US states to test our hypothesis and identify specific local and ecoregional features that explain spatial heterogeneity in TP–CHL relationships. We include variables such as lake depth, natural land cover (for instance, wetland cover in the catchment of lakes and in the ecoregions) and human land use (for instance, agricultural land use in the catchment of lakes and in the ecoregions).4. There was substantial heterogeneity in TP–CHL relationships across the 35 ecoregions. At the local scale, CHL was negatively and positively related to lake mean depth and percentage of wooded wetlands in the catchment, respectively. At the ecoregional scale, the slope parameter was positively related to the percentage of pasture in an ecoregion, indicating that CHL tends to respond more rapidly to changes in TP where there are high levels of agricultural pasture than where there is little. The intercept (i.e. the ecoregion-average CHL) was negatively related to the percentage of wooded wetlands in the ecoregion.5. By explicitly accounting for the hierarchical nature of lake–landscape interactions, we quantified the effects of landscape characteristics on the response of CHL to TP at two spatial scales. We provide new insight into ecoregional drivers of the rate at which algal biomass responds to changes in nutrient concentrations. Our results also indicate that the direction and magnitude of the effects of certain land use and cover characteristics on lake nutrient dynamics may be scale dependent and thus likely to represent different underlying mechanisms regulating lake productivity.
Emergent Archetype Hydrological-Biogeochemical Response Patterns in Heterogeneous Catchments

NASA Astrophysics Data System (ADS)

Jawitz, J. W.; Gall, H. E.; Rao, P.

2013-12-01

What can spatiotemporally integrated patterns observed in stream hydrologic and biogeochemical signals generated in response to transient hydro-climatic and anthropogenic forcing tell us about the interactions between spatially heterogeneous soil-mediated hydrological and biogeochemical processes? We seek to understand how the spatial structure of solute sources coupled with hydrologic responses affect observed concentration-discharge (C-Q) patterns. These patterns are expressions of the spatiotemporal structure of solute loads exported from managed catchments, and their likely ecological consequences manifested in receiving water bodies (e.g., wetlands, rivers, lakes, and coastal waters). We investigated the following broad questions: (1) How does the correlation between flow-generating areas and biogeochemical source areas across a catchment evolve under stochastic hydro-climatic forcing? (2) What are the feasible hydrologic and biogeochemical responses that lead to the emergence of the observed archetype C-Q patterns? and; (3) What implications do these coupled dynamics have for catchment monitoring and implementation of management practices? We categorize the observed temporal signals into three archetypical C-Q patterns: dilution; accretion, and constant concentration. We introduce a parsimonious stochastic model of heterogeneous catchments, which act as hydrologic and biogeochemical filters, to examine the relationship between spatial heterogeneity and temporal history of solute export signals. The core concept of the modeling framework is considering the types and degree of spatial correlation between solute source zones and flow generating zones, and activation of different portions of the catchments during rainfall events. Our overarching hypothesis is that each of the archetype C-Q patterns can be generated by explicitly linking landscape-scale hydrologic responses and spatial distributions of solute source properties within a catchment. The model simulations reproduce the three major C-Q patterns observed in published data, offering valuable insight into coupled catchment processes. The findings have important implications for effective catchment management for water quality improvement, and stream monitoring strategies.
Wetland Management - A Success Story In Transition - Restoration of Bhoj Wetland, India

NASA Astrophysics Data System (ADS)

Mudgal, M. K.; Tech, B. M.; Miwwa

Wetlands are beautiful, biologically diverse, hydrologically disperse and ecological vibrant landscape world wide, embracing soils, water, plants, animals and human be- ing. The population growth in the catchment of wetlands led to multifarious human interventions for deriving maximum benefit from the wetlands and their catchments neglecting and disrespecting the principles of sustainability. This act of destruction has been pronounced in developing countries which are under the grip of poverty, illiteracy and lack of environmental education. SBhoj WetlandS is a Lake situated ´ in Central India, Earthen Dam across the river KOLANS in 1061 AD by then ruler king BHOJ. Till 1950 this Wetland was served as a principal source of water supply, even not requiring filtration. As the city grew and the wetland started getting encir- cled by habitation and urban development, the anthropogenic pressures on the lake increased, thus accelerating the process of eutrophication, making the water unfit for human consumption without due treatment due to deterioration of quality of water. For the conservation and management of Bhoj Wetland (Lake Bhopal) a project is under- taken in the financial assistance from Japan Bank for International Cooperation (JBIC, Japan). The project envisages tackle various issues of conservation and management ofn the wetlands under a multi prongs strategies and manner. Although these issues are deeply interrelated and interlinked but for operational and management ease, these issues have been divided into various sub projects which are being tackled indepen- dently, albeit with undercurrent knowledge and understanding of the related issues and interconnectivity with each other. The Project itself is an apt example of the spectrum of varied problems and issues that come to light when attempts are made for sustain- able conservation and management of a wetland. The Project as envisaged intends to conserve and manage through 14 sub projects as under:- Sub Projects within the wa- ter body 1. Desilting and Dredging 2. Deweeding 3. Deepening and widening of the spill channel 4. Biological control of weeds through acquaculture 5. Improvement and Management of Water Quality through floating fountains 6. Water quality monitoring 7. Restoration of Takia Island Sub Projects in the Fringe Area and in Catchment 8. Catchment Area Treatment through afforestation 9. Construction of check dams, silt traps and cascades 10. Sewerage Scheme 11. Garland Drains 12. Shoreline and Fringe Area Management through Link Road 13. Solid Waste Management 14. Relocation of 1 Dhobighat (Washerman Platform) 2
Accounting for inter-annual and seasonal variability in regionalization of hydrologic response in the Great Lakes basin

NASA Astrophysics Data System (ADS)

Kult, J. M.; Fry, L. M.; Gronewold, A. D.

2012-12-01

Methods for predicting streamflow in areas with limited or nonexistent measures of hydrologic response typically invoke the concept of regionalization, whereby knowledge pertaining to gauged catchments is transferred to ungauged catchments. In this study, we identify watershed physical characteristics acting as primary drivers of hydrologic response throughout the US portion of the Great Lakes basin. Relationships between watershed physical characteristics and hydrologic response are generated from 166 catchments spanning a variety of climate, soil, land cover, and land form regimes through regression tree analysis, leading to a grouping of watersheds exhibiting similar hydrologic response characteristics. These groupings are then used to predict response in ungauged watersheds in an uncertainty framework. Results from this method are assessed alongside one historical regionalization approach which, while simple, has served as a cornerstone of Great Lakes regional hydrologic research for several decades. Our approach expands upon previous research by considering multiple temporal characterizations of hydrologic response. Due to the substantial inter-annual and seasonal variability in hydrologic response observed over the Great Lakes basin, results from the regression tree analysis differ considerably depending on the level of temporal aggregation used to define the response. Specifically, higher levels of temporal aggregation for the response metric (for example, indices derived from long-term means of climate and streamflow observations) lead to improved watershed groupings with lower within-group variance. However, this perceived improvement in model skill occurs at the cost of understated uncertainty when applying the regression to time series simulations or as a basis for model calibration. In such cases, our results indicate that predictions based on long-term characterizations of hydrologic response can produce misleading conclusions when applied at shorter time steps. This study suggests that measures of hydrologic response quantified at these shorter time steps may provide a more robust basis for making predictions in applications of water resource management, model calibration and simulations, and human health and safety.
Phosphorus Export Model Development in a Terminal Lake Basin using Concentration-Streamflow Relationship

NASA Astrophysics Data System (ADS)

Jeannotte, T.; Mahmood, T. H.; Matheney, R.; Hou, X.

2017-12-01

Nutrient export to streams and lakes by anthropogenic activities can lead to eutrophication and degradation of surface water quality. In Devils Lake, ND, the only terminal lake in the Northern Great Plains, the algae boom is of great concern due to the recent increase in streamflow and consequent rise in phosphorus (P) export from prairie agricultural fields. However, to date, very few studies explored the concentration (c) -streamflow (q) relationship in the headwater catchments of the Devils Lake basin. A robust watershed-scale quantitative framework would aid understanding of the c-q relationship, simulating P concentration and load. In this study, we utilize c-q relationships to develop a simple model to estimate phosphorus concentration and export from two headwater catchments of different size (Mauvais Coulee: 1032 km2 and Trib 3: 160 km2) draining to Devils Lake. Our goal is to link the phosphorus export model with a physically based hydrologic model to identify major drivers of phosphorus export. USGS provided the streamflow measurements, and we collected water samples (filtered and unfiltered) three times daily during the spring snowmelt season (March 31, 2017- April 12, 2017) at the outlets of both headwater catchments. Our results indicate that most P is dissolved and very little is particulate, suggesting little export of fine-grained sediment from agricultural fields. Our preliminary analyses in the Mauvais Coulee catchment show a chemostatic c-q relationship in the rising limb of the hydrograph, while the recession limb shows a linear and positive c-q relationship. The poor correlation in the rising limb of the hydrograph suggests intense flushing of P by spring snowmelt runoff. Flushing then continues in the recession limb of the hydrograph, but at a more constant rate. The estimated total P load for the Mauvais Coulee basin is 193 kg/km2, consistent with other catchments of similar size across the Red River of the North basin to the east. We expect our P measurements at Trib 3 basin, a considerably smaller basin compared to Mauvais Coulee, provide an opportunity to investigate the impacts of watershed scales on nutrient exports and c-q relationship. Finally, our study will lay a strong foundation for future nutrient modeling studies in the Devils Lake basin.
Understanding and Predicting the Fate of Semivolatile Organic Pesticides in a Glacier-Fed Lake Using a Multimedia Chemical Fate Model.

PubMed

Wu, Xiaolin; Davie-Martin, Cleo L; Steinlin, Christine; Hageman, Kimberly J; Cullen, Nicolas J; Bogdal, Christian

2017-10-17

Melting glaciers release previously ice-entrapped chemicals to the surrounding environment. As glacier melting accelerates under future climate warming, chemical release may also increase. This study investigated the behavior of semivolatile pesticides over the course of one year and predicted their behavior under two future climate change scenarios. Pesticides were quantified in air, lake water, glacial meltwater, and streamwater in the catchment of Lake Brewster, an alpine glacier-fed lake located in the Southern Alps of New Zealand. Two historic-use pesticides (endosulfan I and hexachlorobenzene) and three current-use pesticides (dacthal, triallate, and chlorpyrifos) were frequently found in both air and water samples from the catchment. Regression analysis indicated that the pesticide concentrations in glacial meltwater and lake water were strongly correlated. A multimedia environmental fate model was developed for these five chemicals in Brewster Lake. Modeling results indicated that seasonal lake ice cover melt, and varying contributions of input from glacial melt and streamwater, created pulses in pesticide concentrations in lake water. Under future climate scenarios, the concentration pulse was altered and glacial melt made a greater contribution (as mass flux) to pesticide input in the lake water.
Rock glacier outflows may adversely affect lakes: lessons from the past and present of two neighboring water bodies in a crystalline-rock watershed.

PubMed

Ilyashuk, Boris P; Ilyashuk, Elena A; Psenner, Roland; Tessadri, Richard; Koinig, Karin A

2014-06-03

Despite the fact that rock glaciers are one of the most common geomorphological expressions of mountain permafrost, the impacts of their solute fluxes on lakes still remain largely obscure. We examined water and sediment chemistry, and biota of two neighboring water bodies with and without a rock glacier in their catchments in the European Alps. Paleolimnological techniques were applied to track long-term temporal trends in the ecotoxicological state of the water bodies and to establish their baseline conditions. We show that the active rock glacier in the mineralized catchment of Lake Rasass (RAS) represents a potent source of acid rock drainage that results in enormous concentrations of metals in water, sediment, and biota of RAS. The incidence of morphological abnormalities in the RAS population of Pseudodiamesa nivosa, a chironomid midge, is as high as that recorded in chironomid populations inhabiting sites heavily contaminated by trace metals of anthropogenic origin. The incidence of morphological deformities in P. nivosa of ∼70% persisted in RAS during the last 2.5 millennia and was ∼40% in the early Holocene. The formation of RAS at the toe of the rock glacier most probably began at the onset of acidic drainage in the freshly deglaciated area. The present adverse conditions are not unprecedented in the lake's history and cannot be associated exclusively with enhanced thawing of the rock glacier in recent years.
Chloride imbalance in rivers from landscapes undergoing hydrological change

NASA Astrophysics Data System (ADS)

Cartwright, I.; Gilfedder, B.; Hofmann, H.

2012-12-01

There has been much research into the sources of solutes in river systems; however, there has been little emphasis on determining whether medium or large catchments are in long-term chemical balance (i.e., whether the flux of solutes into a catchment is balanced by the export from that catchment). Where surface water and groundwater catchments coincide, the mass balance of a conservative solute (X) is: P*X(P) = SW*X(SW) - GW*X(GW) - ΔST*X(ST) where P, SW, and GW, are precipitation, surface water outflows, and groundwater outflows (in m3/year). ΔST accounts for changes to water held in storage in soils, groundwater, or surface water bodies. X is the concentration of solute X in the various stores (mg/m3). Precipitation and river discharges are commonly well constrained and in many regions there are also rainfall, groundwater, and surface water geochemistry data. Groundwater fluxes and changes to volumes of solutes held in storage are less well known and it is difficult to perform accurate solute balances. However, if the flux of a conservative solute out of a catchment via the river system is larger than the input from rainfall (i.e. where SW*X(SW) > P*X(P)), the catchment is a net exporter of solutes. In turn this implies a change to the amount of water stored in the catchment and/or a change in chemistry of the water in the various stores. We use this approach to assess the chemical balance in several regional-scale catchments (areas up to 15,000 km2) in Victoria, southeast Australia. Rivers from many of these catchments are saline (Total Dissolved Solids, TDS, contents >1000 mg/L). Groundwater in this area is also saline (TDS contents locally up to 100,000 mg/L). Major ion geochemistry indicates that the source of Cl in all catchments dominantly from rainfall and the major geochemical process controlling the salinity of surface water and groundwater is evapotranspiration. Cl concentrations and EC values are well correlated allowing a continual record of Cl fluxes to be estimated from long-term (up to 25 years) sub-daily discharge and EC records. The records span several drought and high rainfall periods allowing variation in individual years to be accounted for. Many of the rivers in southeast Victoria export significantly higher volumes of Cl than is delivered via rainfall (up to ~2700%) with average annual fluxes of up to ~200 kg/ha/year. These catchments are not in chemical balance and are net exporters of solutes. Two scenarios may explain the high rates of Cl export in individual catchments. Firstly, saline marshes and lakes developed on young (<1 Ma) basaltic lava plains have gradually drained as blocked river systems have been re-established. Evapotranspiration within these lakes and wetlands produced high Cl loads in shallow groundwater and soil water that is currently being exported via the river systems. Additionally, in many catchments land-clearing over the last 200 years resulted in increased recharge that has resulted in a rise of the regional water table. In turn this has increased the baseflow component to the rivers and Cl from the groundwater that has relatively long residence time is being exported. In both cases, the catchments are adjusting to a new hydrological balance.

Attributes for MRB_E2RF1 Catchments by Major River Basins in the Conterminous United States: Surficial Geology

USGS Publications Warehouse

Wieczorek, Michael; LaMotte, Andrew E.

2010-01-01

This tabular data set represents the area of surficial geology types in square meters compiled for every MRB_E2RF1 catchment of selected Major River Basins (MRBs, Crawford and others, 2006). The source data set is the "Digital data set describing surficial geology in the conterminous US" (Clawges and Price, 1999).The MRB_E2RF1 catchments are based on a modified version of the U.S. Environmental Protection Agency's (USEPA) ERF1_2 and include enhancements to support national and regional-scale surface-water quality modeling (Nolan and others, 2002; Brakebill and others, 2008). Data were compiled for every MRB_E2RF1 catchment for the conterminous United States covering New England and Mid-Atlantic (MRB1), South Atlantic-Gulf and Tennessee (MRB2), the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy (MRB3), the Missouri (MRB4), the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf (MRB5), the Rio Grande, Colorado, and the Great basin (MRB6), the Pacific Northwest (MRB7) river basins, and California (MRB8).
Impact of acid and trace metals deposition on freshwater invertebrates in north-eastern Fennoscandia and Kola Peninsula

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yakovlev, V.

1996-12-31

Freshwater invertebrate communities in a total 400 lakes and streams in northeastern Norway, Finnish Lapland and the Kola Peninsula, subjected to the atmospheric deposition were studied. The severe influence of toxic heavy metals, dusts from smelters and mineral enrichment factories were found in the Kola Peninsula. The negative acidification effects on benthic communities were found in the Jarfjord (Norway), Enontekio, Ranua-Posio and Kittila-Kolari (Finnish Lapland) areas and in the Kola Peninsula (Russia). Taxa groups, known to be sensitive to acidification, such as gammarids, snails, mayflies, stone flies, were represented with few species and in a low abundance. Heavy metals accumulationmore » in biota is recorded in areas surrounding nickel smelters in the Kola Peninsula. The metal concentration invertebrates in remote areas is rather wide and depend on an air deposition, characteristics of lake catchment areas, as well as water acidity. The environmental variables, such as lake hydrological type, altitude of lakes, dominant substratum type, abundance of macrophytes and mosses in sampling area, content of pollutants in water also show significant relationships with metal concentration in invertebrates. The most severe negative effects on biota were found in waters with low pH and simultaneously contaminated by heavy metals. The biological method for estimation of simultaneously water acidification and contamination is suggested.« less
Lake-level stratigraphy and geochronology revisited at Lago (Lake) Cardiel, Argentina, and changes in the Southern Hemispheric Westerlies over the last 25 ka

NASA Astrophysics Data System (ADS)

Quade, J.; Kaplan, M. R.

2017-12-01

Paleoshorelines around Lago (Lake) Cardiel in southern Argentina (S48.9°, W71.3°; ∼275 m) record substantial changes in lake area over the past 25 ka. Our results combined with previous research show that during the last glacial maximum (or LGM, 23-21 ka), the lake stood at near modern levels, but had nearly dried up by ∼13 ka. Between 11.3 and 10.1 ka the lake reached its highest point (+54-58 m) and greatest extent in at least the last 40 ka. Lake levels dropped thereafter and experienced two lower-lake periods: 8.5-7.5 ka and 5-3.3 ka; and two higher-lake periods: 7.4-6 and ∼5.2 ka. In the last 3.5 ka, the lake has remained generally near or slightly above its present level. The depth and surface area of Lago Cardiel are controlled mainly by precipitation onto the lake and surrounding catchment, air and water temperature, and wind-speed related to local strength of the Southern Hemispheric Westerlies (SHW). Our lake-level reconstruction combined with evidence from other studies suggest that on average the core of the SHW was located well to the north (<45°S) of the Cardiel basin during the deep lake phase associated with the LGM, and was well to the south (>55°S?) during the hydrologic maximum of Cardiel in the early Holocene. The lower phases of the lake at 20.0-11.5, 8.5-7.5, and 5.0-3.3 ka generally correspond to cold conditions in other records, when we infer that the SHW were strongly focused around the latitudes of Cardiel at 49°S.
Interannual lake level fluctuations (1993 1999) in Africa from Topex/Poseidon: connections with ocean atmosphere interactions over the Indian Ocean

NASA Astrophysics Data System (ADS)

Mercier, Franck; Cazenave, Anny; Maheu, Caroline

2002-04-01

Water level fluctuations of continental lakes are related to regional to global scale climate changes. Water level fluctuations reflect variations in evaporation and precipitation over the lake area and its catchment area. Over such inland water bodies, the satellite altimetry technique offers both a world-wide coverage and a satisfying accuracy. We present here results of lake level variations of 12 African lakes based on 7 years of Topex/Poseidon (T/P) altimetry data acquired between 1993 and 1999. Among the 12 African lakes presented in this study, three are reservoirs whose level fluctuations are mainly driven by anthropogenic usage of the water. Either closed or open, the nine remaining lakes are sensitive indicators of the climate evolution over Africa during the 1990s. Seasonal signals of each lake are clearly identified and filtered out to focus on the interannual fluctuations. Clear correlated regional variations are reported among the east African lakes: several lakes exhibit a regular level decrease between 1993 and 1997, probably due to intense droughts. However, the most spectacular feature is an abrupt water level rise occurring in late 1997-early 1998 and affecting most of the lakes located within the Rift Valley. This major anomalous pattern, explained by a large excess rainfall anomaly occurring in late 1997, is quantified in both space and time domains through an EOF analysis of the lake level height time series. The spatial distribution of the leading mode of lake level height correlates with the dominant mode of precipitation computed over the same time span. Nevertheless, similar rainfall anomaly, but with lesser intensity, occurred in late 1994 without any noticeable consequence on lake level. The precipitation anomaly appears related to the equatorial Indian Ocean warming reported during the 1997-1998 ENSO event.
Forests fuel fish growth in freshwater deltas

PubMed Central

Tanentzap, Andrew J.; Szkokan-Emilson, Erik J.; Kielstra, Brian W.; Arts, Michael T.; Yan, Norman D.; Gunn, John M.

2014-01-01

Aquatic ecosystems are fuelled by biogeochemical inputs from surrounding lands and within-lake primary production. Disturbances that change these inputs may affect how aquatic ecosystems function and deliver services vital to humans. Here we test, using a forest cover gradient across eight separate catchments, whether disturbances that remove terrestrial biomass lower organic matter inputs into freshwater lakes, thereby reducing food web productivity. We focus on deltas formed at the stream-lake interface where terrestrial-derived particulate material is deposited. We find that organic matter export increases from more forested catchments, enhancing bacterial biomass. This transfers energy upwards through communities of heavier zooplankton, leading to a fourfold increase in weights of planktivorous young-of-the-year fish. At least 34% of fish biomass is supported by terrestrial primary production, increasing to 66% with greater forest cover. Habitat tracers confirm fish were closely associated with individual catchments, demonstrating that watershed protection and restoration increase biomass in critical life-stages of fish. PMID:24915965
Climate Change Increasing Calcium and Magnesium Leaching from Granitic Alpine Catchments.

PubMed

Kopáček, Jiří; Kaňa, Jiří; Bičárová, Svetlana; Fernandez, Ivan J; Hejzlar, Josef; Kahounová, Marie; Norton, Stephen A; Stuchlík, Evžen

2017-01-03

Climate change can reverse trends of decreasing calcium and magnesium [Ca + Mg] leaching to surface waters in granitic alpine regions recovering from acidification. Despite decreasing concentrations of strong acid anions (-1.4 μeq L -1 yr -1 ) during 2004-2016 in nonacidic alpine lakes in the Tatra Mountains (Central Europe), the average [Ca + Mg] concentrations increased (2.5 μeq L -1 yr -1 ), together with elevated terrestrial export of bicarbonate (HCO 3 - ; 3.6 μeq L -1 yr -1 ). The percent increase in [Ca + Mg] concentrations in nonacidic lakes (0.3-3.2% yr -1 ) was significantly and positively correlated with scree proportion in the catchment area and negatively correlated with the extent of soil cover. Leaching experiments with freshly crushed granodiorite, the dominant bedrock, showed that accessory calcite and (to a lesser extent) apatite were important sources of Ca. We hypothesize that elevated terrestrial export of [Ca + Mg] and HCO 3 - resulted from increased weathering caused by accelerated physical erosion of rocks due to elevated climate-related mechanical forces (an increasing frequency of days with high precipitation amounts and air temperatures fluctuating around 0 °C) during the last 2-3 decades. These climatic effects on water chemistry are especially strong in catchments where fragmented rocks are more exposed to weathering, and their position is less stable than in soil.
the observation, simulation and evaluation of lake-air interaction process over a high altitude small lake on the Tibetan Plateau

NASA Astrophysics Data System (ADS)

Wang, Binbin; Ma, Yaoming; Ma, Weiqiang; Su, Bob

2017-04-01

Lakes are an important part of the landscape on the Tibetan Plateau. The area that contains most of the plateau lakes has been expanding in recent years, but the impact of lakes on lake-atmosphere energy and water interactions is poorly understood because of a lack of observational data and adequate modeling systems. Furthermore, Precise measurements of evaporation and understanding of the physical controls on turbulent heat flux over lakes at different time scales have fundamental significance for catchment-scale water balance analysis and local-scale climate modeling. To test the performance of lake-air turbulent exchange models over high-altitude lakes and to understanding the driving forces for turbulent heat flux and obtain the actual evaporation over the small high-altitude lakes, an eddy covariance observational system was built above the water surface of the small Nam Co Lake (with an altitude of 4715 m and an area of approximately 1 km2) in April 2012. Firstly, we proposed the proper Charnock coefficient (0.031) and the roughness Reynolds number (0.54) for simulation using turbulent data in 2012, and validated the results using data in 2013 independently; secondly, wind speed shows significance at half-hourly time scales, whereas water vapor and temperature gradients have higher correlations over daily and monthly time scales in lake-air turbulent heat exchange; thirdly, the total evaporation in this small lake (812 mm) is approximately 200 mm larger than that from adjacent Nam Co (approximately 627 mm) during their ice-free seasons. Moreover, the energy stored during April to June is mainly released during September to November, suggesting an energy balance closure value of 0.97 over the entire ice-free season; lastly, 10 evaporation estimation methods are evaluated with the prepared datasets.
Signs of lateral transport of CO2 and CH4 in freshwater systems in boreal zone

NASA Astrophysics Data System (ADS)

Ojala, A.; Pumpanen, J. S.

2013-12-01

The numerous waterbodies and their riparian zones in the boreal zone are important to lateral carbon transport of terrestrial origin. These freshwater systems are also significant for carbon cycling on the landscape level. However, the lateral signals of carbon gases can be difficult to detect and thus, we used here different approaches to verify the phenomenon. We installed continuous measurement systems with CO2 probes in the riparian zone soil matrix around a small pristine headwater lake, in the lake, and in the outflowing stream and followed up the seasonal variation in CO2 concentration and in rain event-driven changes. We also used the probes in a second-order stream discharging a catchment of managed forest. The conventional weekly sampling protocol on water column CO2 and CH4 concentrations as well as gas fluxes was applied in three lakes surrounded by managed forests and some crop land but having different size and water quality. In two of the lakes most drastic changes in gas fluxes occurred not in spring but during or just after the summer rains when the clear water lake changed from a small carbon sink to carbon source and in the humic lake almost half of the CO2 and CH4 fluxes occurred during or just after the rainy period. Gas concentrations in the water columns revealed that the high surface water concentrations resulting in peak fluxes were not due to transport from hypolimnia rich in gases, but were due to soil processes and export from the flooded catchments. In the third lake, seasonal peak fluxes took place just after ice out, but again this was not a result of carbon gases accumulated under the ice, but gases originated from the surrounding catchment. In this lake, ca. 30 % of the annual CO2 flux occurred in May and 13 % of CH4 was emitted during one single week in May. In general, CH4 appeared as a good tracer for lateral transport. In the soil-lake-stream continuum, seasonal variation in CO2 was greatest and concentrations highest deep in the soil and in the lake itself, but also in the stream, especially further down from the lake. In the stream, the influence of the riparian zone superseded that of the lake at less than 150 m distance, which resulted in wider variation and higher concentrations of CO2. After a spell of heavy rain, the CO2 concentration in the soil increased and supposedly, a considerable amount of CO2 of terrestrial origin entered the lake annually. However, since the rain event was combined with exceptionally high winds mixing the water column, the riparian CO2 load was diluted and could not be properly tracked down. The second-order stream draining a small lake had an unresponsive catchment with high base flow contribution and the low flow was important for the total annual CO2 export. In general, CO2 export was controlled by runoff. There was no concentration-discharge relationship which was different from four other catchments in Canada, UK and Sweden. The only exception was snowmelt event in spring when CO2 concentrations were high. This high concentration could be tracked down in the downstream lake. The studies thus revealed the importance of hydrological events such as high spring discharge after snowmelt and extreme rain events in summer for lateral carbon gas transport.
A 1000-year record of dry conditions in the eastern Canadian prairies reconstructed from oxygen and carbon isotope measurements on Lake Winnipeg sediment organics

USGS Publications Warehouse

Buhay, W.M.; Simpson, S.; Thorleifson, H.; Lewis, M.; King, J.; Telka, A.; Wilkinson, Philip M.; Babb, J.; Timsic, S.; Bailey, D.

2009-01-01

A short sediment core (162 cm), covering the period AD 920-1999, was sampled from the south basin of Lake Winnipeg for a suite of multi-proxy analyses leading towards a detailed characterisation of the recent millennial lake environment and hydroclimate of southern Manitoba, Canada. Information on the frequency and duration of major dry periods in southern Manitoba, in light of the changes that are likely to occur as a result of an increasingly warming atmosphere, is of specific interest in this study. Intervals of relatively enriched lake sediment cellulose oxygen isotope values (??18Ocellulose) were found to occur from AD 1180 to 1230 (error range: AD 1104-1231 to 1160-1280), 1610-1640 (error range: AD 1571-1634 to 1603-1662), 1670-1720 (error range: AD 1643-1697 to 1692-1738) and 1750-1780 (error range: AD 1724-1766 to 1756-1794). Regional water balance, inferred from calculated Lake Winnipeg water oxygen isotope values (??18Oinf-lw), suggest that the ratio of lake evaporation to catchment input may have been 25-40% higher during these isotopically distinct periods. Associated with the enriched d??18Ocellulose intervals are some depleted carbon isotope values associated with more abundantly preserved sediment organic matter (d??13COM). These suggest reduced microbial oxidation of terrestrially derived organic matter and/or subdued lake productivity during periods of minimised input of nutrients from the catchment area. With reference to other corroborating evidence, it is suggested that the AD 1180-1230, 1610-1640, 1670-1720 and 1750-1780 intervals represent four distinctly drier periods (droughts) in southern Manitoba, Canada. Additionally, lower-magnitude and duration dry periods may have also occurred from 1320 to 1340 (error range: AD 1257-1363), 1530-1540 (error range: AD 1490-1565 to 1498-1572) and 1570-1580 (error range: AD 1531-1599 to 1539-1606). ?? 2009 John Wiley & Sons, Ltd.
Hydrogeomorphic Classification of Wetlands on Mt. Desert Island, Maine, Including Hydrologic Susceptibility Factors for Wetlands in Acadia National Park

USGS Publications Warehouse

Nielsen, Martha G.

2006-01-01

The U.S. Geological Survey, in cooperation with the National Park Service, developed a hydrogeomorphic (HGM) classification system for wetlands greater than 0.4 hectares (ha) on Mt. Desert Island, Maine, and applied this classification using map-scale data to more than 1,200 mapped wetland units on the island. In addition, two hydrologic susceptibility factors were defined for a subset of these wetlands, using 11 variables derived from landscape-scale characteristics of the catchment areas of these wetlands. The hydrologic susceptibility factors, one related to the potential hydrologic pathways for contaminants and the other to the susceptibility of wetlands to disruptions in water supply from projected future changes in climate, were used to indicate which wetlands (greater than 1 ha) in Acadia National Park (ANP) may warrant further investigation or monitoring. The HGM classification system consists of 13 categories: Riverine-Upper Perennial, Riverine-Nonperennial, Riverine- Tidal, Depressional-Closed, Depressional-Semiclosed, Depressional-Open, Depressional-No Ground-Water Input, Mineral Soil Flat, Organic Soil Flat, Tidal Fringe, Lacustrine Fringe, Slope, and Hilltop/Upper Hillslope. A dichotomous key was developed to aid in the classification of wetlands. The National Wetland Inventory maps produced by the U.S. Fish and Wildlife Service provided the wetland mapping units used for this classification. On the basis of topographic map information and geographic information system (GIS) layers at a scale of 1:24,000 or larger, 1,202 wetland units were assigned a preliminary HGM classification. Two of the 13 HGM classes (Riverine-Tidal and Depressional-No Ground-Water Input) were not assigned to any wetlands because criteria for determining those classes are not available at that map scale, and must be determined by more site-specific information. Of the 1,202 wetland polygons classified, which cover 1,830 ha in ANP, 327 were classified as Slope, 258 were Depressional (Open, Semiclosed, and Closed), 231 were Riverine (Upper Perennial and Nonperennial), 210 were Soil Flat (Mineral and Organic), 68 were Lacustrine Fringe, 51 were Tidal Fringe, 22 were Hilltop/Upper Hillslope, and another 35 were small open water bodies. Most small, isolated wetlands classified on the island are Slope wetlands. The least common, Hilltop/Upper Hillslope wetlands, only occur on a few hilltops and shoulders of hills and mountains. Large wetland complexes generally consist of groups of Depressional wetlands and Mineral Soil Flat or Organic Soil Flat wetlands, often with fringing Slope wetlands at their edges and Riverine wetlands near streams flowing through them. The two analyses of wetland hydrologic susceptibility on Mt. Desert Island were applied to 186 wetlands located partially or entirely within ANP. These analyses were conducted using individually mapped catchments for each wetland. The 186 wetlands were aggregated from the original 1,202 mapped wetland polygons on the basis of their HGM classes. Landscape-level hydrologic, geomorphic, and soil variables were defined for the catchments of the wetlands, and transformed into scaled scores from 0 to 10 for each variable. The variables included area of the wetland, area of the catchment, area of the wetland divided by the area of the catchment, the average topographic slope of the catchment, the amount of the catchment where bedrock crops out with no soil cover or excessively thin soil cover, the amount of storage (in lakes and wetlands) in the catchment, the topographic relief of the catchment, the amount of clay-rich soil in the catchment, the amount of manmade impervious surface, whether the wetland had a stream inflow, and whether the wetland had a hydraulic connection to a lake or estuary. These data were determined using a GIS and data layers mapped at a scale of 1:24,000 or larger. These landscape variables were combined in different ways for the two hydrologic susceptibility fact
Hydrochemistry dynamics in remote mountain lakes and its relation to catchment and atmospheric features: the case study of Sabocos Tarn, Pyrenees.

PubMed

Santolaria, Zoe; Arruebo, Tomas; Urieta, José Santiago; Lanaja, Francisco Javier; Pardo, Alfonso; Matesanz, José; Rodriguez-Casals, Carlos

2015-01-01

Increasing the understanding of high mountain lake dynamics is essential to use these remote aquatic ecosystems as proxies of global environmental changes. With this aim, at Sabocos, a Pyrenean cirque glacial lake or tarn, this study shows the main results of a morphological and catchment characterization, along with statistical analyses of its hydrochemical trends and their concomitant driving factors from 2010 to 2013. Dissolved oxygen, water temperature stratification, and its snow and ice cover composition and dynamics have been also investigated. According to morphological analyses, Sabocos can be classified as a medium-large and deep lake, having a circular contour and a long water retention time as compared to Pyrenean glacial lake average values. Sabocos hydrochemistry is mainly determined by very high alkalinity, pH and conductivity levels, and high Ca(2+), Mg(2+), and SO4(2-) content, coming from the easily weatherable limestone-dolomite bedrock. Thus, lake water is well buffered, and therefore, Sabocos tarn is non-sensitive to acidification processes. On the other hand, the main source of K(+), Na(+), and Cl(-) (sea salts) and nutrients (NH4(+), NO3(-), and phosphorous) to lake water appears to be atmospheric deposition. Primary production is phosphorous limited, and due to the N-saturation stage of the poorly developed soils of Sabocos catchment, NO3(-) is the chief component in the total nitrogen pool. External temperature seems to be the major driver regulating lake productivity, since warm temperatures boot primary production. Although precipitation might also play an important role in lake dynamics, especially regarding to those parameters influenced by the weathering of the bedrock, its influence cannot be easily assessed due to the seasonal isolation produced by the ice cover. Also, as occurs in the whole Pyrenean lake district, chemical composition of bulk deposition is highly variable due to the contribution of air masses with different origin.
Simulation of 1998-Big Flood in Changjiang River Catchment, China

NASA Astrophysics Data System (ADS)

Nakayama, T.; Watanabe, M.

2006-05-01

Almost every year, China is affected by severe flooding, which causes considerable economic loss and serious damage to towns and farms. Big floods are mainly concentrated in the middle and lower reaches of the "seven big rivers", which include the Changjiang (Yangtze) River, the Yellow (Huanghe) River, and the Huaihe River. The Changjiang River is the fourth largest water resource to the oceans after the Amazon, Zaire, and Orinoco Rivers. In addition to abnormal weather, artificial effects were considered as main causes of the big flood disaster in the Changjiang River catchment by the previous researches; (i) extreme deforestation and soil erosion in the upper reaches, (ii) shrinking of lake water volumes and their reduced connection with the Changjiang River due to reclamation of lakes that retarded water in the middle reaches, and (iii) restriction of channel capacity following levee construction. Because there is an urgent need to quantify these relations on the spatial scale of the whole catchment in order to prevent flood damage as small as possible, it is very important to evaluate the complicated phenomena of water/heat dynamics in the Changjiang River catchment by using process-based models. The present research focuses on simulating the water/heat dynamics for 1998 big-flood with 60-year recurrent period in the Changjiang River catchment. We compared the flood period of 1998 with the normal period of 1987-1988. We expanded the NIES Integrated Catchment-based Eco-hydrology (NICE) model (Nakayama and Watanabe, 2004; Nakayama et al., 2006) for the application to broader catchments in order to evaluate large- scale flooding in the Changjiang River (NICE-FLD). We simulated the water/heat dynamics in the entire catchment (3,000 km wide by 1,000 km long) with a resolution of 10 km mesh by using the NICE-FLD. The model reproduced excellently the river discharge, soil moisture, evapotranspiration, groundwater level, et al. Furthermore, we evaluated the role of flood storage capacity in the lakes and farms in relation to the water/heat budgets, and simulated the change of water/heat dynamics by human activity in order to help decision-making on sustainable development in the catchment.
Improvement of a free software tool for the assessment of sediment connectivity

NASA Astrophysics Data System (ADS)

Crema, Stefano; Lanni, Cristiano; Goldin, Beatrice; Marchi, Lorenzo; Cavalli, Marco

2015-04-01

Sediment connectivity expresses the degree of linkage that controls sediment fluxes throughout landscape, in particular between sediment sources and downstream areas. The assessment of sediment connectivity becomes a key issue when dealing with risk mitigation and priorities of intervention in the territory. In this work, the authors report the improvements made to an open source and stand-alone application (SedInConnect, http://www.sedalp.eu/download/tools.shtml), along with extensive applications to alpine catchments. SedInConnect calculates a sediment connectivity index as expressed in Cavalli et al. (2013); the software improvements consisted primarily in the introduction of the sink feature, i.e. areas that act as traps for sediment produced upstream (e.g., lakes, sediment traps). Based on user-defined sinks, the software decouples those parts of the catchment that do not deliver sediment to a selected target of interest (e.g., fan apex, main drainage network). In this way the assessment of sediment connectivity is achieved by taking in consideration effective sediment contributing areas. Sediment connectivity analysis has been carried out on several catchments in the South Tyrol alpine area (Northern Italy) with the goal of achieving a fast and objective characterization of the topographic control on sediment transfer. In addition to depicting the variability of sediment connectivity inside each basin, the index of connectivity has proved to be a valuable indicator of the dominant process characterizing the basin sediment dynamics (debris flow, bedload, mixed behavior). The characterization of the dominant process is of great importance for the hazard and risk assessment in mountain areas, and for choice and design of structural and non-structural intervention measures. The recognition of the dominant sediment transport process by the index of connectivity is in agreement with evidences arising from post-event field surveys and with the application of morphometric indexes, such as the Melton ruggedness number, commonly used for discriminating debris-flow catchments from bedload catchments. References: Cavalli, M., Trevisani, S., Comiti, F., Marchi, L., 2013. Geomorphometric assessment of spatial sediment connectivity in small Alpine catchments. Geomorphology 188,31-41. doi:10.1016/j.geomorph.2012.05.007
Reviewing Landmark Nitrogen Cap and Trade Legislation in New Zealand's Taupo Catchment: What Have We Learned after 5+ Years?

NASA Astrophysics Data System (ADS)

Baisden, W. T.; Hamilton, D. P.

2014-12-01

In 2007, the first cap and trade legislation for a catchment nitrogen (N) budget was enacted to protect water quality in New Zealand's iconic Lake Taupo. The clarity of the 616 km² N-limited oligotrophic lake was declining due to human-induced increases in N losses from the 3,487 km² catchment. Focus was placed on reversing increases in N inputs from agriculture, and to a lesser degree sewerage sources. The legislation imposed a cap equal to 20% reduction in the N inputs to the lake, and enabled trading. The landmark legislation could have failed during appeal. Sources of disagreement included the N budgeting model and grand-parenting method that benchmarked the N leaching of individual farms. The N leaching rates for key land uses were also a major battleground, with strong effects on the viability of trading and relative value of enterprises. Sufficient science was applied to resolve the substantive issues in the appeal by 2008. Crucially, the decision recognized that N inputs to the "N cascade" mattered more than leaching evidence including land-use legacies. Other catchment cap-and-trade schemes followed. Rotorua Lakes had already capped inputs and established a ~33% N input reduction target after acceptance of a trading scheme compatible with groundwater lag times. In the Upper Manawatu catchment, a cap-and-trade scheme now governs river N loads in a more typical farming region, with an innovative allocation scheme based on the natural capital of soils. Collectively, these schemes have succeeded in imposing a cap, and signaling the intention of reductions over time. I conclude with common themes in the successes, and examine the role of science in the success and ongoing implementation. Central to success has been the role of science in framing N budgets at farm and catchment scales. Long-term data has been invaluable, despite the need to correct biases. Cap-and-trade policies alter future science needs toward reducing uncertainty in overall budgets, the ability to measure success or failure in innovative source reductions at a management scale, and defining quantitative measures of aquatic health. Broadly, the schemes have enabled a culture of innovation, in farming and research. For example, recent evidence suggests it may be possible to flip the Rotorua Lakes into a P limitation regime through alum dosing.
Estimation of design floods in ungauged catchments using a regional index flood method. A case study of Lake Victoria Basin in Kenya

NASA Astrophysics Data System (ADS)

Nobert, Joel; Mugo, Margaret; Gadain, Hussein

Reliable estimation of flood magnitudes corresponding to required return periods, vital for structural design purposes, is impacted by lack of hydrological data in the study area of Lake Victoria Basin in Kenya. Use of regional information, derived from data at gauged sites and regionalized for use at any location within a homogenous region, would improve the reliability of the design flood estimation. Therefore, the regional index flood method has been applied. Based on data from 14 gauged sites, a delineation of the basin into two homogenous regions was achieved using elevation variation (90-m DEM), spatial annual rainfall pattern and Principal Component Analysis of seasonal rainfall patterns (from 94 rainfall stations). At site annual maximum series were modelled using the Log normal (LN) (3P), Log Logistic Distribution (LLG), Generalized Extreme Value (GEV) and Log Pearson Type 3 (LP3) distributions. The parameters of the distributions were estimated using the method of probability weighted moments. Goodness of fit tests were applied and the GEV was identified as the most appropriate model for each site. Based on the GEV model, flood quantiles were estimated and regional frequency curves derived from the averaged at site growth curves. Using the least squares regression method, relationships were developed between the index flood, which is defined as the Mean Annual Flood (MAF) and catchment characteristics. The relationships indicated area, mean annual rainfall and altitude were the three significant variables that greatly influence the index flood. Thereafter, estimates of flood magnitudes in ungauged catchments within a homogenous region were estimated from the derived equations for index flood and quantiles from the regional curves. These estimates will improve flood risk estimation and to support water management and engineering decisions and actions.
Pre-aged plant waxes in tropical lake sediments and their influence on the chronology of molecular paleoclimate proxy records

NASA Astrophysics Data System (ADS)

Douglas, Peter M. J.; Pagani, Mark; Eglinton, Timothy I.; Brenner, Mark; Hodell, David A.; Curtis, Jason H.; Ma, Keith F.; Breckenridge, Andy

2014-09-01

Sedimentary records of plant-wax hydrogen (δDwax) and carbon (δ13Cwax) stable isotopes are increasingly applied to infer past climate change. Compound-specific radiocarbon analyses, however, indicate that long time lags can occur between the synthesis of plant waxes and their subsequent deposition in marginal marine sediments. The influence of these time lags on interpretations of plant-wax stable isotope records is presently unconstrained, and it is unclear whether such time lags also affect lacustrine sediments. We present compound-specific radiocarbon (14Cwax) data for n-alkanoic acid plant waxes (n-C26 to n-C32) from: (1) a sediment core from Lake Chichancanab, Yucatan Peninsula, Mexico, (2) soils in the Lake Chichancanab catchment, and (3) surface sediments from three other lakes in southeastern Mexico and northern Guatemala. 14Cwax ages in the surface sediments are consistently older than modern, and may be negatively correlated with mean annual precipitation and positively correlated with lake catchment area. 14Cwax ages in soils surrounding Lake Chichancanab increase with soil depth, consistent with deep, subsoil horizons being the primary source of lacustrine aged plant waxes, which are likely delivered to lake sediments through subsurface transport. Plant waxes in the Lake Chichancanab core are 350-1200 years older than corresponding ages of bulk sediment deposition, determined by 14C dates on terrestrial plant macrofossils in the core. A δDwax time series is in closer agreement with other regional proxy hydroclimate records when a plant-wax 14C age model is applied, as opposed to the macrofossil-based core chronology. Inverse modeling of plant-wax age distribution parameters suggests that plant waxes in the Lake Chichancanab sediment core derive predominantly from millennial-age soil carbon pools that exhibit relatively little age variance (<200 years). Our findings demonstrate that high-temporal-resolution climate records inferred from stable isotope measures on plant waxes in lacustrine sediments may suffer from possible chronologic distortions as a consequence of long residence times of plant waxes in soils. They also underscore the importance of direct radiocarbon dating of these organic molecules.
New Insights Into the Climate and Vegetation History of the subtropical Crater Lake 'Tswaing', South Africa, for the Last 300,000 Year

NASA Astrophysics Data System (ADS)

Kristen, I.; Fuhrmann, A.; Haug, G. H.; Horsfield, B.; Oberhänsli, H.; Partridge, T. C.; Thorpe, J.; Wilkes, H.

2005-12-01

Deeper time palaeoclimate reconstructions are still rare on the continental southern hemisphere. Here we present new biogeochemical data from a core retrieved in crater lake 'Tswaing' (formerly 'Pretoria saltpan'). This opens a novel chance to get a more detailed view into climate variability of the subtropical region of South Africa on the glacial/interglacial time scale. The crater 'Tswaing' was formed around 220±52 kyr ago by a meteorite impact. However, new U/Th analyses of authigenic carbonates provide preliminary evidence that the lake might be older than 300 kyr. Today the basin contains a shallow (< 3 m water depth), hypersaline (pH ~10) lake with a diameter of about 300 m in an about 1 km wide crater. Hence, the lake catchment is small with no water in- or outflow. Therefore, the lake is sensitive for variations in rainfall and probably wind stress. Our 90 m composite core profile consists of partly fine-laminated lake sediments intercalated with mudflow deposits. Previous investigations and our new data reveal a considerable variability of bulk geochemical proxies such as total inorganic carbon (TIC), total organic carbon (TOC) and the C/N ratio. The upper half of the core is dominated by fluctuations in TOC while TIC controls the variation in the lower half of the core. These data argue for substantial changes in the depositional environment of the lake system. They are complemented by facies analyses in thin sections, major element patterns derived from μXRF scanning , the carbon isotopic composition of the bulk sediment, maceral analysis, and lipid biomarkers of the organic material in the sediments. First results allow to distinguish intervals with completely different ecosystems and hydrology during lake history. Intervals with dinoflagellates and algae as main primary producers alternate with phases dominated by bacteria and ciliates feeding on them. Future detailed analyses will provide new insights into the development of these climate sensitive lacustrine habitats as well as the surrounding vegetation in the catchment area over two to four glacial cycles.
Ecological, biogeochemical and salinity changes in coastal lakes and wetlands over the last 200 years

NASA Astrophysics Data System (ADS)

Roberts, Lucy; Holmes, Jonathan; Horne, David

2016-04-01

Shallow lakes provide extensive ecosystem services and are ecologically important aquatic resources supporting a diverse flora and fauna. In marginal-marine areas, where such lakes are subjected to the multiple pressures of coastal erosion, sea level rise, increasing sea surface temperature and increasing frequency and intensity of storm surges, environments are complex and unstable. They are characterised by physico-chemical variations due to climatic (precipitation/evaporation cycles) and dynamic factors (tides, currents, freshwater drainage and sea level changes). Combined with human activity in the catchment these processes can alter the salinity, habitat and ecology of coastal fresh- to brackish water ecosystems. In this study the chemical and biological stability of coastal lakes forming the Upper Thurne catchment in the NE of the Norfolk Broads, East Anglia, UK are seriously threatened by long-term changes in salinity resulting from storm surges, complex hydrogeology and anthropogenic activity in the catchment. Future management decisions depend on a sound understanding of the potential ecological impacts, but such understanding is limited by short-term observations and measurements. This research uses palaeolimnological approaches, which can be validated and calibrated with historical records, to reconstruct changes in the aquatic environment on a longer time scale than can be achieved by observations alone. Here, salinity is quantitatively reconstructed using the trace-element geochemistry (Sr/Ca and Mg/Ca) of low Mg-calcite shells of Ostracoda (microscopic bivalved crustaceans) and macrophyte and macroinvertebrate macrofossil remains are used as a proxy to assess ecological change in response to variations in salinity. δ13C values of Cladocera (which are potentially outcompeted by the mysid Neomysis integer with increasing salinity and eutrophication) can be used to reconstruct carbon cycling and energy pathways in lake food webs, which alongside reconstructions of salinity and eutrophication can aid the disentanglement of environmental drivers and increase understanding on the interactions between ecology and biogeochemical cycles within the lake. Previous palaeolimnological work on the Thurne Broads system has suggested shifts between macrophyte abundance and loss within a framework of rising salinity (varying between 1.8-8.7‰ and eutrophication (phosphorus loading greater than 100μg-1). A complex combination of salinity, eutrophication, toxicity and associated changes in habitat have acted as drivers for ecological change over the past 200 years, but these interactions have not previously been well understood. By combining reconstructions of palaeosalinity, biodiversity, food web dynamics, redox conditions and eutrophication, the interaction between and controls on long-term variations in shallow lake environments can be further explored.
Distribution and flux of 238Pu, 239,240Pu, 241Am, 137Cs and 210Pb to high arctic lakes in the Thule district (Greenland).

PubMed

Eriksson, M; Holm, E; Roos, P; Dahlgaard, H

2004-01-01

Environmental samples (soil, sediment and lake water) in the Thule area (NW Greenland) have been studied to assess the contamination of radionuclides originating from a nuclear weapons accident (the Thule accident in 1968). Four lakes were chosen at different distances from the point of impact with the Thule air base community situated in between. The sedimentation rates in the lakes varied from 0.4 mm a(-1) (5 mg cm(-2) a(-1)) to 1.6 mm a(-1) (82 mg cm(-2) a(-1)). With these sedimentation rates, it is not possible to resolve the (239,240)Pu global fallout peak from a possible (239,240)Pu "accident" peak in the sediment depth profiles. However, the (239,240)Pu/(137)Cs and the (238)Pu/(239,240)Pu ratios agreed well with global fallout ratios, indicating that plutonium originating from the accident had not reached these lakes. This also indicates that the Thule air base community has probably only been exposed to radionuclides from the accident to a very limited extent. A limited study showed that (210)Pb could not be used as a normalizing nuclide to explain the transport of transuranic elements from the catchment area to the lake, i.e. (210)Pb has a different transport mechanism from that of the transuranic elements studied in this investigation.
In-lake carbon dioxide concentration patterns in four distinct phases in relation to ice cover dynamics

NASA Astrophysics Data System (ADS)

Denfeld, B. A.; Wallin, M.; Sahlee, E.; Sobek, S.; Kokic, J.; Chmiel, H.; Weyhenmeyer, G. A.

2014-12-01

Global carbon dioxide (CO2) emission estimates from inland waters include emissions at ice melt that are based on simple assumptions rather than evidence. To account for CO2 accumulation below ice and potential emissions into the atmosphere at ice melt we combined continuous CO2 concentrations with spatial CO2 sampling in an ice-covered small boreal lake. From early ice cover to ice melt, our continuous surface water CO2 concentration measurements at 2 m depth showed a temporal development in four distinct phases: In early winter, CO2 accumulated continuously below ice, most likely due to biological in-lake and catchment inputs. Thereafter, in late winter, CO2 concentrations remained rather constant below ice, as catchment inputs were minimized and vertical mixing of hypolimnetic water was cut off. As ice melt began, surface water CO2 concentrations were rapidly changing, showing two distinct peaks, the first one reflecting horizontal mixing of CO2 from surface and catchment waters, the second one reflecting deep water mixing. We detected that 83% of the CO2 accumulated in the water during ice cover left the lake at ice melt which corresponded to one third of the total CO2 storage. Our results imply that CO2 emissions at ice melt must be accurately integrated into annual CO2 emission estimates from inland waters. If up-scaling approaches assume that CO2 accumulates linearly under ice and at ice melt all CO2 accumulated during ice cover period leaves the lake again, present estimates may overestimate CO2 emissions from small ice covered lakes. Likewise, neglecting CO2 spring outbursts will result in an underestimation of CO2 emissions from small ice covered lakes.

Terrestrial organic matter as subsidies that aid in the recovery of macroinvertebrates in industrially damaged lakes.

PubMed

Szkokan-Emilson, E J; Wesolek, B E; Gunn, J M

2011-09-01

The importance of allochthonous carbon to the productivity of stream ecosystems in temperate ecozones is well understood, but this relationship is less established in oligotrophic lakes. The nearshore littoral zones, at the interface of terrestrial and aquatic systems, are areas where the influence of terrestrial subsidies is likely greatest. We investigated the response of nearshore communities to variation in the quantity and composition of allochthonous materials, determined the landscape characteristics that regulate the variation of this subsidy, and explored the potential for terrestrial restoration practices to influence the export of organic matter to lakes. Stepwise multiple regressions revealed that diversity of nearshore macroinvertebrate families increased with the amount of fine particulate organic matter (FPOM) captured in sediment traps. The quantity of FPOM (g) increased with forest cover, and the relative amount of FPOM (percentage of total particulate material) in the traps increased with surface area of wetland in the catchments. These models suggest that terrestrially derived subsidies are important in smelter-impacted watersheds, and that the restoration of forests and wetlands will speed the return of nearshore consumer community diversity in industrially damaged lakes.
Modeling the effects of climatic and land use changes on phytoplankton and water quality of the largest Turkish freshwater lake: Lake Beyşehir.

PubMed

Bucak, Tuba; Trolle, Dennis; Tavşanoğlu, Ü Nihan; Çakıroğlu, A İdil; Özen, Arda; Jeppesen, Erik; Beklioğlu, Meryem

2018-04-15

Climate change and intense land use practices are the main threats to ecosystem structure and services of Mediterranean lakes. Therefore, it is essential to predict the future changes and develop mitigation measures to combat such pressures. In this study, Lake Beyşehir, the largest freshwater lake in the Mediterranean basin, was selected to study the impacts of climate change and various land use scenarios on the ecosystem dynamics of Mediterranean freshwater ecosystems and the services that they provide. For this purpose, we linked catchment model outputs to the two different processed-based lake models: PCLake and GLM-AED, and tested the scenarios of five General Circulation Models, two Representation Concentration Pathways and three different land use scenarios, which enable us to consider the various sources of uncertainty. Climate change and land use scenarios generally predicted strong future decreases in hydraulic and nutrient loads from the catchment to the lake. These changes in loads translated into alterations in water level as well as minor changes in chlorophyll a (Chl-a) concentrations. We also observed an increased abundance of cyanobacteria in both lake models. Total phosphorus, temperature and hydraulic loading were found to be the most important variables determining cyanobacteria biomass. As the future scenarios revealed only minor changes in Chl-a due to the significant decrease in nutrient loads, our results highlight that reduced nutrient loading in a warming world may play a crucial role in offsetting the effects of temperature on phytoplankton growth. However, our results also showed increased abundance of cyanobacteria in the future may threaten ecosystem integrity and may limit drinking water ecosystem services. In addition, extended periods of decreased hydraulic loads from the catchment and increased evaporation may lead to water level reductions and may diminish the ecosystem services of the lake as a water supply for irrigation and drinking water. Copyright © 2017 Elsevier B.V. All rights reserved.
High resolution analysis of northern Patagonia lake sediments

NASA Astrophysics Data System (ADS)

Jarvis, S. W.; Croudace, I. W.; Langdon, P. G.; Rindby, A.

2009-04-01

Sediment cores covering the period from the last glacial maximum through the Holocene to the present have been collected from sites in the Chacubuco valley, southern Chile (around 47°08'S, 72°25'W, to the east of the North Patagonian Icecap). Cores were taken from five lakes and one recently dried lake bed. Short cores (0.2 to 0.5m), covering approximately the last two hundred years, were taken from all the lakes. Additionally, long sequences were obtained from one of the lakes and from the dried lake bed, the latter sequence extending back to the last glacial maximum as indicated by thick clay at the base. Each of the lakes are small-medium sized and are open systems situated at 300-1000m above sea level. The shorter cores comprise predominantly clastic gyttja but show a number of distinct changes in colour and chemical composition that suggest major environmental changes over the period of sediment accumulation. This is also reflected in variations in the loss on ignition of samples from the cores and in elemental profiles produced by scanning the cores with the Itrax micro-XRF corescanner at 200μm resolution. The long sequence from the dried lake bed has very low organic content glacial clay at the base, interpreted as last glacial maximum basal clay following determination in the field that this layer exceeded 2m in thickness. Similar sediments occur within a stratigraphically discrete section of approximately 14cm and may relate to a stadial event. The latter section also shows a drop in organic content and appears to be glacial clay incorporating some coarse sandy components indicative of detrital input from the catchment. The second long sequence, from a carbonate lake, includes two mineral layers indicating increased detrital input from the catchment. The deeper and thicker of these layers appears similar to the 14cm layer in the first long sequence, while the upper layer comprises a fine grain size indicative of rock flour and hence also of glacial activity in the catchment. Variation of elemental composition of these ‘glacial' layers is also clear from the Itrax data. It therefore appears that there have been significant reglaciation events in the catchment since the last glacial maximum. Many cores contain tephra layers, identified both visually and from the Itrax scans. Some of these have been confirmed as volcanic ash from the 1991 eruption of Mt Hudson, which at 45°54'S, 72°58'W is the southern-most volcano in the Chilean Andes and only 140km from the study area. Further work is underway to confirm and identify the source and age of other suspected tephra layers. Sediment accumulation rates in the upper parts of the cores are of the order of 1mm/yr (as determined by lead-210, caesium-137 dating and the 1991 Hudson tephra). Given XRF scan resolutions of up to 200μm there is thus the potential for investigation of sub-annual variability. Funding has been obtained to determine carbon-14 dates for the lower parts of the longer cores. The reproducibility and accuracy of the Itrax data has been validated using conventional WD-XRF spectrometry and the work presented will also include geochemical interpretation of the XRF data and comparison with recorded and proxy-inferred climate data for the region.
Holocene multi-proxy environmental reconstruction from lake Hakluytvatnet, Amsterdamøya Island, Svalbard (79.5°N)

NASA Astrophysics Data System (ADS)

Gjerde, Marthe; Bakke, Jostein; D'Andrea, William J.; Balascio, Nicholas L.; Bradley, Raymond S.; Vasskog, Kristian; Ólafsdóttir, Sædis; Røthe, Torgeir O.; Perren, Bianca B.; Hormes, Anne

2018-03-01

High resolution proxy records of past climate are sparse in the Arctic due to low organic production that restricts the use of radiocarbon dating and challenging logistics that make data collection difficult. Here, we present a new lake record from lake Hakluytvatnet at Amsterdamøya island (79.5°N), the northwesternmost island on Svalbard. Multi-proxy analyses of lake sediments in combination with geomorphological mapping reveal large environmental shifts that have taken place at Amsterdamøya during the Holocene. A robust chronology has been established for the lake sediment core through 28 AMS radiocarbon ages, and this gives an exceptionally well-constrained age control for a lake at this latitude. The Holocene was a period with large changes in the Hakluytvatnet catchment, and the onset of the Neoglacial (ca. 5 ka) marks the start of modern-day conditions in the catchment. The Neoglacial is characterized by fluctuations in the minerogenic input to the lake as well as internal productivity, and we suggest that these fluctuations are driven by atmospherically forced precipitation changes as well as sea ice extent modulating the amount of moisture that can reach Hakluytvatnet.
Synchronicity of long-term nitrate patterns in forested catchments across the northeastern U.S.

EPA Science Inventory

Nitrogen movement through minimally-disturbed catchments can be affected by a variety of biogeochemical processes, climatic effects, hydrology and in-stream or in-lake processes. These combine to create dizzying complexity in long-term and seasonal nitrate patterns, with adjacen...
[Soil Phosphorus Forms and Leaching Risk in a Typically Agricultural Catchment of Hefei Suburban].

PubMed

Fan, Hui-hui; Li, Ru-zhong; Pei, Ting-ting; Zhang, Rui-gang

2016-01-15

To investigate the soil phosphorus forms and leaching risk in a typically agricultural catchment of Ershibu River in Hefei Suburban, Chaohu Lake basin, 132 surface soil samples were collected from the catchment area. The spatial distribution of total phosphorus (TP) and bio-available phosphorus (Bio-P), and the spatial variability of soil available phosphorus (Olsen-P) and easy desorption phosphorus (CaCl2-P) were analyzed using the Kriging technology of AreGIS after speciation analysis of soil phosphorus. Moreover, the enrichment level of soil phosphorus was studied, and the phosphorus leaching risk was evaluated through determining the leaching threshold value of soil phosphorus. The results showed that the samples with high contents of TP and Bio-P mainly located in the upstream of the left tributary and on the right side of local area where two tributaries converged. The enrichment rates of soil phosphorus forms were arranged as follows: Ca-P (15.01) > OP (4.16) > TP (3. 42) > IP (2.94) > Ex-P (2.76) > Fe/Al-P (2.43) > Olsen-P (2.34). The critical value of Olsen-P leaching was 18.388 mg x kg(-1), and the leaching samples with values higher than the threshold value accounted for 16.6% of total samples. Generally, the high-risk areas mainly occurred in the upstream of the left tributary, the middle of the right tributary and the local area of the downstream of the area where two tributaries converged.
Solar Output Controls Periodicity in Lake Productivity and Wetness at Southernmost South America

PubMed Central

Pérez-Rodríguez, Marta; Gilfedder, Benjamin-Silas; Hermanns, Yvonne-Marie; Biester, Harald

2016-01-01

Cyclic changes in total solar irradiance (TSI) during the Holocene are known to affect global climatic conditions and cause cyclic climatic oscillations, e.g., Bond events and related changes of environmental conditions. However, the processes how changes in TSI affect climate and environment of the Southern Hemisphere, especially in southernmost South America, a key area for the global climate, are still poorly resolved. Here we show that highly sensitive proxies for aquatic productivity derived from sediments of a lake near the Chilean South Atlantic coast (53 °S) strongly match the cyclic changes in TSI throughout the Holocene. Intra-lake productivity variations show a periodicity of ~200–240 years coherent with the time series of TSI-controlled cosmogenic nuclide 10Be production. In addition TSI dependent periodicity of Bond events (~1500 years) appear to control wetness at the LH site indicated by mineral matter erosion from the catchment to the lake assumingly through shifts of the position of the southern westerly wind belt. Thus, both intra-lake productivity and wetness at the southernmost South America are directly or indirectly controlled by TSI. PMID:27869191
Novel sedimentological fingerprints link shifting depositional processes to Holocene climate transitions in East Greenland

NASA Astrophysics Data System (ADS)

van der Bilt, Willem G. M.; Rea, Brice; Spagnolo, Matteo; Roerdink, Desiree L.; Jørgensen, Steffen L.; Bakke, Jostein

2018-05-01

The Arctic warms faster than any other region of our planet. Besides melting glaciers, thawing permafrost and decreasing sea-ice, this amplified response affects earth surface processes. This geomorphological expression of climate change may alter landscapes and increase the frequency and magnitude of geohazards like floods or mass-movements. Beyond the short span of sparse monitoring time series, geological archives provide a valuable long-term context for future risk assessment. Lake sediment sequences are particularly promising in this respect as continuous recorders of surface process change. Over the past decade, the emergence of new techniques that characterize depositional signatures in more detail has enhanced this potential. Here, we present a well-dated Holocene-length lake sediment sequence from Ammassalik Island on southeast Greenland. This area is particularly sensitive to regional shifts in the Arctic climate system due to its location near the sea-ice limit, the Greenland Ice Sheet and the convergence of polar and Atlantic waters. The expression of Holocene change is fingerprinted using physical (grain size, organic content, density), visual (3-D Computed Tomography) and geochemical (X-Ray Fluorescence, X-Ray Diffraction) evidence. We show that three sharp transitions characterize the Holocene evolution of Ymer Lake. Between 10 and 9.5 cal. ka BP, rapid local glacier loss from the lake catchment culminated in an outburst flood. Following a quiescent Holocene climatic optimum, Neoglacial cooling, lengthening lake ice cover and shifting wind patterns prompted in-lake avalanching of sediments from 4.2 cal. ka BP onwards. Finally, glaciers reformed in the catchment around 1.2 cal. ka BP. The timing of these shifts is consistent with the regional expression of deglaciation, Neoglacial cooling and Little Ice Age-type glacier growth, respectively. The novel multi-proxy approach applied in this study rigorously links depositional sediment signatures to surface processes and thereby provides a key step towards a process-based understanding of climate responses.
Allogenic sedimentary components of Bear Lake, Utah and Idaho

USGS Publications Warehouse

Rosenbaum, J.G.; Dean, W.E.; Reynolds, R.L.; Reheis, M.C.

2009-01-01

Bear Lake is a long-lived lake filling a tectonic depression between the Bear River Range to the west and the Bear River Plateau to the east, and straddling the border between Utah and Idaho. Mineralogy, elemental geochemistry, and magnetic properties provide information about variations in provenance of allogenic lithic material in last-glacial-age, quartz-rich sediment in Bear Lake. Grain-size data from the siliciclastic fraction of late-glacial to Holocene carbonate-rich sediments provide information about variations in lake level. For the quartz-rich lower unit, which was deposited while the Bear River fl owed into and out of the lake, four source areas are recognized on the basis of modern fluvial samples with contrasting properties that reflect differences in bedrock geology and in magnetite content from dust. One of these areas is underlain by hematite-rich Uinta Mountain Group rocks in the headwaters of the Bear River. Although Uinta Mountain Group rocks make up a small fraction of the catchment, hematite-rich material from this area is an important component of the lower unit. This material is interpreted to be glacial fl our. Variations in the input of glacial flour are interpreted as having caused quasi-cyclical variations in mineralogical and elemental concentrations, and in magnetic properties within the lower unit. The carbonate-rich younger unit was deposited under conditions similar to those of the modern lake, with the Bear River largely bypassing the lake. For two cores taken in more than 30 m of water, median grain sizes in this unit range from ???6 ??m to more than 30 ??m, with the coarsest grain sizes associated with beach or shallow-water deposits. Similar grain-size variations are observed as a function of water depth in the modern lake and provide the basis for interpreting the core grain-size data in terms of lake level. Copyright ?? 2009 The Geological Society of America.
Attributes for MRB_E2RF1 Catchments by Major River Basins in the Conterminous United States: Hydrologic Landscape Regions

USGS Publications Warehouse

Wieczorek, Michael; LaMotte, Andrew E.

2010-01-01

This tabular data set represents the area of Hydrologic Landscape Regions (HLR) compiled for every MRB_E2RF1 catchment of the Major River Basins (MRBs, Crawford and others, 2006). The source data set is a 100-meter version of Hydrologic Landscape Regions of the United States (Wolock, 2003). HLR groups watersheds on the basis of similarities in land-surface form, geologic texture, and climate characteristics. The MRB_E2RF1 catchments are based on a modified version of the U.S. Environmental Protection Agency's (USEPA) ERF1_2 and include enhancements to support national and regional-scale surface-water quality modeling (Nolan and others, 2002; Brakebill and others, 2011). Data were compiled for every MRB_E2RF1 catchment for the conterminous United States covering New England and Mid-Atlantic (MRB1), South Atlantic-Gulf and Tennessee (MRB2), the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy (MRB3), the Missouri (MRB4), the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf (MRB5), the Rio Grande, Colorado, and the Great basin (MRB6), the Pacific Northwest (MRB7) river basins, and California (MRB8).
Attributes for MRB_E2RF1 Catchments by Major River Basins in the Conterminous United States: Level 3 Ecoregions

USGS Publications Warehouse

Wieczorek, Michael; LaMotte, Andrew E.

2010-01-01

This tabular data set represents the estimated area of level 3 ecological landscape regions (ecoregions), as defined by Omernik (1987), compiled for every MRB_E2RF1 catchment of the Major River Basins (MRBs, Crawford and others, 2006). The source data set is Level III Ecoregions of the Continental United States (U.S. Environmental Protection Agency, 2003). The MRB_E2RF1 catchments are based on a modified version of the U.S. Environmental Protection Agency's (USEPA) ERF1_2 and include enhancements to support national and regional-scale surface-water quality modeling (Nolan and others, 2002; Brakebill and others, 2011). Data were compiled for every MRB_E2RF1 catchment for the conterminous United States covering New England and Mid-Atlantic (MRB1), South Atlantic-Gulf and Tennessee (MRB2), the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy (MRB3), the Missouri (MRB4), the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf (MRB5), the Rio Grande, Colorado, and the Great basin (MRB6), the Pacific Northwest (MRB7) river basins, and California (MRB8).
Attributes for MRB_E2RF1 Catchments by Major River Basins in the Conterminous United States: Level 3 Nutrient Ecoregions, 2002

USGS Publications Warehouse

Wieczorek, Michael; LaMotte, Andrew E.

2010-01-01

This tabular data set represents the area of each level 3 nutrient ecoregion in square meters compiled for every MRB_E2RF1 catchment of the Major River Basins (MRBs, Crawford and others, 2006). The source data are from the 2002 version of the U.S. Environmental Protection Agency's (USEPA) Aggregations of Level III Ecoregions for National Nutrient Assessment & Management Strategy (USEPA, 2002). The MRB_E2RF1 catchments are based on a modified version of the U.S. Environmental Protection Agency's (USEPA) ERF1_2 and include enhancements to support national and regional-scale surface-water quality modeling (Nolan and others, 2002; Brakebill and others, 2011). Data were compiled for every MRB_E2RF1 catchment for the conterminous United States covering New England and Mid-Atlantic (MRB1), South Atlantic-Gulf and Tennessee (MRB2), the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy (MRB3), the Missouri (MRB4), the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf (MRB5), the Rio Grande, Colorado, and the Great basin (MRB6), the Pacific Northwest (MRB7) river basins, and California (MRB8).
The Upper Laacher See Tephra in Lake Geneva sediments: Paleoenvironmental and paleoclimatological implications

USGS Publications Warehouse

Moscariello, A.; Costa, F.

1997-01-01

Microstratigraphical analysis of Late glacial lacustrine sediments from Geneva Bay provided evidence of a tephra layer within the upper Aller??d biozone. The layer consists of alkali feldspar, quartz, plagioclase. amphibole, pyroxene, opaques, titanite and glass shards. Electron microprobe analyses and morphological study of glass shards allowed correlation with the upper part of the Laacher See Tephra of the Laacher See volcano (Eifel Mountains, Germany). Sedimentological features of enclosing lacustrine sediments suggest that a momentary decrease in precipitation occurred in the catchment area and consequent reduction in detrital supply in the lake, after the ash fall-out. This has been interpreted as the environmental response to a momentary cooling following the Laacher See Tephra aerosols emission. Comparison with Sedimentological features characterizing the Aller??d-Younger Dryas transition highlights the sensitivity of Lake Geneva system in recording both short and long-terms climate-induced environmental changes.
Water regime of Playa Lakes from southern Spain: conditioning factors and hydrological modeling.

PubMed

Moral, Francisco; Rodriguez-Rodriguez, Miguel; Beltrán, Manuel; Benavente, José; Cifuentes, Victor Juan

2013-07-01

Andalusia's lowland countryside has a network of small geographically isolated playa lakes scattered across an area of 9000 km2 whose watersheds are mostly occupied by clayey rocks. The hydrological model proposed by the authors seeks to find equilibrium among usefulness, simplicity, and applicability to isolated playas in a semiarid context elsewhere. Based in such model, the authors have used monthly climatic data, water stage measurements, and the basin morphometry of a particular case (Los Jarales playa lake) to calibrate the soil water budget in the catchment and the water inputs from the watershed (runoff plus groundwater flow) at different scales, from monthly to daily. After the hydrologic model was calibrated, the authors implemented simulations with the goal of reproducing the past hydrological dynamics and forecasting water regime changes that would be caused by a modification of the wetland morphometry.
Modeling the Sedimentary Infill of Lakes in the East African Rift: A Case Study of Multiple versus Single Rift Basin Segments

NASA Astrophysics Data System (ADS)

Zhang, C.; Scholz, C. A.

2016-12-01

The sedimentary basins in the East African Rift are considered excellent modern examples for investigating sedimentary infilling and evolution of extensional systems. Some lakes in the western branch of the rift have formed within single-segment systems, and include Lake Albert and Lake Edward. The largest and oldest lakes developed within multi-segment systems, and these include Lake Tanganyika and Lake Malawi. This research aims to explore processes of erosion and sedimentary infilling of the catchment area in single-segment rift (SSR) and multi-segment rift (MSR) systems. We consider different conditions of regional precipitation and evaporation, and assess the resulting facies architecture through forward modeling, using state-of-the-art commercial basin modeling software. Dionisos is a three-dimensional numerical stratigraphic forward modeling software program, which simulates basin-scale sediment transport based on empirical water- and gravity-driven diffusion equations. It was classically used to quantify the sedimentary architecture and basin infilling of both marine siliciclastic and carbonate environments. However, we apply this approach to continental rift basin environments. In this research, two scenarios are developed, one for a MSR and the other for a SSR. The modeled systems simulate the ratio of drainage area and lake surface area observed in modern Lake Tanganyika and Lake Albert, which are examples of MSRs and SSRs, respectively. The main parameters, such as maximum subsidence rate, water- and gravity-driven diffusion coefficients, rainfall, and evaporation, are approximated using these real-world examples. The results of 5 million year model runs with 50,000 year time steps show that MSRs are characterized by a deep water lake with relatively modest sediment accumulation, while the SSRs are characterized by a nearly overfilled lake with shallow water depths and thick sediment accumulation. The preliminary modeling results conform to the features of sedimentary infills revealed by seismic reflection data acquired in Lake Tanganyika and Lake Albert. Future models will refine the parameters of rainfall and evaporation in these two scenarios to better evaluate detailed basin facies architecture.
Frequency of event deposits reflecting glacial/interglacial conditions during the last ca. 50,000 years in the south Patagonian maar lake Laguna Potrok Aike, Argentina

NASA Astrophysics Data System (ADS)

Kliem, Pierre; Hahn, Annette; Ohlendorf, Christian; Zolitschka, Bernd; Pasado Science Team

2010-05-01

Laguna Potrok Aike is a 100m deep maar lake located in the dry steppe of southern Patagonia. The catchment area of >200km² mainly consists of till from Bella Vista and Río Ciaike Glaciations as well as of alkali-olivine basalts of the Pali Aike Volcanic Field. Today's regional climate is affected by the Southern Hemispheric Westerlies and the rainshadow effect of the north-south striking Andean mountain chain. Since lakes are valuable terrestrial paleoclimate archives, sediments of Laguna Potrok Aike should reflect shifts of mid latitude wind and pressure fields as well as precipitation changes in southeastern South America. Aiming at the reconstruction of past climate, the deep drilling at Laguna Potrok Aike was accomplished in the framework of the ICDP project PASADO during Sept. to Dec. 2008. By correlation of three holes drilled at Site 2 ca. 700 m south of the lake's center, a composite profile of 106.09 mcd (meters composite depth) was established. According to the lowermost 14C-age of aquatic macro remains from 80.6 mcd, the entire record comprises at least 50,000 years. The initial lithological description indicates that 50.74 m (i.e. 47.8%) of the sediment record consists of remobilized sediment (turbidity currents; homogenites; ball and pillow structures, gravel layers, slumps). Such deposits are almost absent in the top 12 mcd, where laminated clays and silts dominate. Correlation with an existing piston core allows a temporal relation to the Holocene. Apart from obviously remobilized deposits Holocene sediments are distinguished from Late Glacial deposits by a lower frequency of coarse silt/fine sand layers within a silt/clay matrix. Frequency and thickness of remobilized deposits increase with sediment depth. Most reworked sections are composed of three units: (1) a dark, coarse and fining upward base overlain by (2) a homogeneous layer of silt and (3) clay capped by a relatively thin light colored clay layer. Such sequences were often described as homogenites from marine sediments but are only rarely known from lakes. In the record from Laguna Potrok Aike thickest homogenites reach up to 3 m in thickness. In contrast, turbidites are characterized by a fining-upward pattern of the entire sequence. Homogenites in lake and marine sediments are generally regarded as representing a record for regional seismicity or tsunami activity. Since homogenites are not only triggered by seismotectonic activity and no such deposits are represented in the Holocene sediments of Laguna Potrok Aike, we hypothesize that homogenite generation could be linked to different climate conditions during glacial times. Reasons for this climate link may be (1) higher clastic input through the main tributary or (2) an extremely low lake level. The first option could be the result of more intense geomorphodynamic processes in the catchment area than today due to periglacial conditions with permafrost, forcing precipitation and melt water to run off superficially. Evidence for permafrost conditions in this region until the end of the last glacial is given by an OSL-dated sand wedge in the catchment area (19.1 ± 1.4ka). The latter explanation is supported by the occurrence of coarse gravel at the bases of some homogenites as well as by one chaotic gravel-dominated unit between 87 and 89 mcd, considering that the distal core is located 1.8 km from the main tributary.
Estimation of monthly water yields and flows for 1951-2012 for the United States portion of the Great Lakes Basin with AFINCH

USGS Publications Warehouse

Luukkonen, Carol L.; Holtschlag, David J.; Reeves, Howard W.; Hoard, Christopher J.; Fuller, Lori M.

2015-01-01

Monthly water yields from 105,829 catchments and corresponding flows in 107,691 stream segments were estimated for water years 1951–2012 in the Great Lakes Basin in the United States. Both sets of estimates were computed by using the Analysis of Flows In Networks of CHannels (AFINCH) application within the NHDPlus geospatial data framework. AFINCH provides an environment to develop constrained regression models to integrate monthly streamflow and water-use data with monthly climatic data and fixed basin characteristics data available within NHDPlus or supplied by the user. For this study, the U.S. Great Lakes Basin was partitioned into seven study areas by grouping selected hydrologic subregions and adjoining cataloguing units. This report documents the regression models and data used to estimate monthly water yields and flows in each study area. Estimates of monthly water yields and flows are presented in a Web-based mapper application. Monthly flow time series for individual stream segments can be retrieved from the Web application and used to approximate monthly flow-duration characteristics and to identify possible trends.
The effectiveness and resilience of phosphorus management practices in the Lake Simcoe watershed, Ontario, Canada

NASA Astrophysics Data System (ADS)

Crossman, J.; Futter, M. N.; Palmer, M.; Whitehead, P. G.; Baulch, H. M.; Woods, D.; Jin, L.; Oni, S. K.; Dillon, P. J.

2016-09-01

Uncertainty surrounding future climate makes it difficult to have confidence that current nutrient management strategies will remain effective. This study used monitoring and modeling to assess current effectiveness (% phosphorus reduction) and resilience (defined as continued effectiveness under a changing climate) of best management practices (BMPs) within five catchments of the Lake Simcoe watershed, Ontario. The Integrated Catchment Phosphorus model (INCA-P) was used, and monitoring data were used to calibrate and validate a series of management scenarios. To assess current BMP effectiveness, models were run over a baseline period 1985-2014 with and without management scenarios. Climate simulations were run (2070-2099), and BMP resilience was calculated as the percent change in effectiveness between the baseline and future period. Results demonstrated that livestock removal from water courses was the most effective BMP, while manure storage adjustments were the least. Effectiveness varied between catchments, influenced by the dominant hydrological and nutrient transport pathways. Resilience of individual BMPs was associated with catchment sensitivity to climate change. BMPs were most resilient in catchments with high soil water storage capacity and small projected changes in frozen-water availability and in soil moisture deficits. Conversely, BMPs were less resilient in catchments with larger changes in spring melt magnitude and in overland flow proportions. Results indicated that BMPs implemented are not always those most suited to catchment flow pathways, and a more site-specific approach would enhance prospects for maintaining P reduction targets. Furthermore, BMP resilience to climate change can be predicted from catchment physical properties and present-day hydrochemical sensitivity to climate forcing.
Origin of carbon released from ecosystems affected by permafrost degradation in Northern Siberia

NASA Astrophysics Data System (ADS)

Gandois, L.; Hoyt, A.; Xu, X.; Hatte, C.; Teisserenc, R.; Tananaev, N.

2016-12-01

Permafrost soils and peatlands store half of the soil organic carbon stock worldwide, and are rapidly evolving as a result of permafrost thaw. Determining the origin (permafrost or recent photosynthesis) of carbon which is released to surface waters and the atmosphere is crucial to assess Arctic ecosystems' potential feedback to climate change. In order to evaluate it, we investigated the stable and radioactive content of carbon in solid organic matter, dissolved organic matter (DOM) and dissolved CO2 and CH4 in a discontinuous permafrost area of Siberia affected by permafrost degradation (Igarka, Graviyka catchment (67°27'11''N, 86°32'07''E)). We collected samples from the active layer, permafrost, surface water and bubbles from thermokarst lakes. We further investigated DOM and dissolved CO2 and CH4 in porewater profiles, streams and the catchment outlet. In thermokarst lakes, DOM of surface water as well as CO2 and CH4 from bubbles from lake sediments predominantly originate from modern carbon. In two locations, CO2 and CH4 from bubbles have relatively low 14C contents, with ages greater than 700 yr BP, but still younger that what was previously reported in Eastern Siberia. In all samples the Δ14C of CH4 and CO2 were strongly correlated, with CH4 being consistently older than CO2, indicating strong interrelation between CO2 and CH4 cycles. In our study, permafrost influenced CO2 and CH4 is found in small ponds where palsa collapse and the resulting bank erosion has mobilized sequestered carbon. In peatland porewater, the Δ14C of DOM, CO2 and CH4 increases with depth (DOM: 1385 ±45 yr BP at 2m), indicating a contribution from Holocene peatlands affected by permafrost. In deep layers, CO2 reduction is the dominant pathway of CH4 production, whereas acetate fermentation dominates in thermokarst lakes. In summary, the majority of dissolved CO2 and CH4 analyzed from thermokarst lakes and degraded peatlands is modern and originates from recently fixed carbon. Additionally, the DOM exported in small streams draining peatlands is also modern. However, at the catchment scale, an additional contribution from deep groundwater or thawing permafrost results in an intermediate Δ14C of DOM (300-400 yr BP) at the outlet of the Graviyka River.
Catchment nitrogen saturation drives ecological change in an alpine lake in SW China (eastern margin of Tibet)

NASA Astrophysics Data System (ADS)

Anderson, N. J.; Hu, Z.; Yang, X.; Zhang, E.

2011-12-01

There is substantial evidence for recent (last ca. 120 years) ecological change in remote arctic and alpine lakes (increased productivity, altered biological structure). Initially, these changes were attributed to global warming which has altered the heat budgets of these lakes (stronger stratification, longer ice free periods). The emphasis on temperature, however, ignores that global environmental change is driven by a range of multiple stressors (e.g. altered biogeochemical cycles, land cover change). One of the characteristics of the observed change in remote lakes is the expansion of small species of the planktonic diatom genus Cyclotella. It is increasingly obvious that the recent success of this diatom genus is driven by other factors (nutrients, light, mixing depth) as much as temperature. SE Asia is a major hotspot for the emission of reactive nitrogen as a result of intensive agriculture and fossil fuel combustion. In this study we report recent ecological change in a small, oligotrophic alpine lake (ShadeCo; altitude 4423 m) located in Sichuan Province (SW China), one of many relatively unstudied alpine lakes on the eastern margin of Tibet. The lake is located above the tree-line and there is no cultural land-use; the catchment vegetation is dominated by alpine shrub (predominantly Rhododendron). We used a multi-proxy palaeolimnological approach (diatom, geochemical and stable isotope analyses of a 210-Pb dated core) coupled with regional long-term climate data to understand the pronounced 20th century changes in the diatom record, notably an expansion of Cyclotella spp from around 1920. This initial increase is coincident with warming in SW China but the maximum Cyclotella abundance occurs in in the 1970s and 1980s, a period of regional cooling and major changes in catchment-lake biogeochemistry as indicated by geochemical analyses. The possible drivers of the observed changes (nitrogen deposition, temperature) at this site are discussed in the context of regional water chemistry surveys.

The High Arctic's Only Great Lake Is Succumbing To Climate Warming

NASA Astrophysics Data System (ADS)

St Louis, V. L.; Lehnherr, I.; Schiff, S. L.; Sharp, M. J.; Smol, J. P.; Muir, D.; Gardner, A. S.; Tarnocai, C.; St Pierre, K.; Michelutti, N.; Emmerton, C. A.; Mortimer, C.; Talbot, C.; Wiklund, J.

2016-12-01

Lake Hazen, located within Quttinirpaaq National Park on northern Ellesmere Island (Nunavut, Canada), is the largest lake by volume north of the Arctic Circle and the High Arctic's only true Great Lake. Lake Hazen has a maximum depth of 267 m, a surface area of 540 km2 and a 8400 km2 watershed that is 1/3 glaciated. The climate of the Lake Hazen watershed has experienced a recent strong warming trend of 0.21 °C yr-1 from 2000-2012. During this period, modeled glacier mass-balance values showed a distinct shift from net annual mass gain of 0.3 Gt to a net annual mass loss of up to 1.4 Gt beginning in 2007-2008. Recent warming of soils (0.14 oC yr-1) and deepening of the active layer in the Lake Hazen watershed have also occurred. Rising temperatures had important consequences for summer lake ice cover: the ice-free area on the lake increased by an average of 3 km2 yr-1 from 2000 to 2012, and full ice-off on Lake Hazen became more frequent, from 60% of the years between 1985-95 to 88% of the years between 2006-12. The 250 year sediment record obtained from the floor of Lake Hazen showed that, in the past 15 years, changes in diatom species % abundance, sedimentation rates, geological inputs from the catchment, the abundance of redox sensitive elements such as Fe and Mn in the sediments, and fluxes of organic carbon and contaminants are historically unprecedented and consistent with the observed trends of rising surface temperatures, increasing glacial melt and runoff, and decreasing summer lake ice cover. These changes have important implications for in-lake processes that pertain to ecosystem net productivity, and the cycling of carbon, nutrients and contaminants. We demonstrate that even more resilient ecosystems such as very large lakes are exhibiting regime shifts due to climate change and entering new ecological states.
DYNAMICS OF NUTRIENTS AND HYDROLOGY IN A LAKE SUPERIOR COASTAL WETLAND

EPA Science Inventory

Coastal wetlands are hydrologically complex ecosystems situated at the interface of upland catchments and oligotrophic Lake Superior. Little is known about nutrient dynamics within coastal wetlands or their role in modifying or contributing to nutrient fluxes from watersheds to ...
Evaluation of catchment delineation methods for the medium-resolution National Hydrography Dataset

USGS Publications Warehouse

Johnston, Craig M.; Dewald, Thomas G.; Bondelid, Timothy R.; Worstell, Bruce B.; McKay, Lucinda D.; Rea, Alan; Moore, Richard B.; Goodall, Jonathan L.

2009-01-01

Different methods for determining catchments (incremental drainage areas) for stream segments of the medium-resolution (1:100,000-scale) National Hydrography Dataset (NHD) were evaluated by the U.S. Geological Survey (USGS), in cooperation with the U.S. Environmental Protection Agency (USEPA). The NHD is a comprehensive set of digital spatial data that contains information about surface-water features (such as lakes, ponds, streams, and rivers) of the United States. The need for NHD catchments was driven primarily by the goal to estimate NHD streamflow and velocity to support water-quality modeling. The application of catchments for this purpose also demonstrates the broader value of NHD catchments for supporting landscape characterization and analysis. Five catchment delineation methods were evaluated. Four of the methods use topographic information for the delineation of the NHD catchments. These methods include the Raster Seeding Method; two variants of a method first used in a USGS New England study-one used the Watershed Boundary Dataset (WBD) and the other did not-termed the 'New England Methods'; and the Outlet Matching Method. For these topographically based methods, the elevation data source was the 30-meter (m) resolution National Elevation Dataset (NED), as this was the highest resolution available for the conterminous United States and Hawaii. The fifth method evaluated, the Thiessen Polygon Method, uses distance to the nearest NHD stream segments to determine catchment boundaries. Catchments were generated using each method for NHD stream segments within six hydrologically and geographically distinct Subbasins to evaluate the applicability of the method across the United States. The five methods were evaluated by comparing the resulting catchments with the boundaries and the computed area measurements available from several verification datasets that were developed independently using manual methods. The results of the evaluation indicated that the two New England Methods provided the most accurate catchment boundaries. The New England Method with the WBD provided the most accurate results. The time and cost to implement and apply these automated methods were also considered in ultimately selecting the methods used to produce NHD catchments for the conterminous United States and Hawaii. This study was conducted by a joint USGS-USEPA team during the 2-year period that ended in September 2004. During the following 2-year period ending in the fall of 2006, the New England Methods were used to produce NHD catchments as part of a multiagency effort to generate the NHD streamflow and velocity estimates for a suite of integrated geospatial products known as 'NHDPlus.'
Variation in reciprocal subsidies between lakes and land: perspectives from the mountains of California

Treesearch

Jonah Piovia-Scott; Steven Sadro; Roland A. Knapp; James Sickman; Karen L. Pope; Sudeep Chandra

2016-01-01

Lakes are connected to surrounding terrestrial habitats by reciprocal flows of energy and nutrients. We synthesize data from Californiaâs mountain lake catchments to investigate how these reciprocal subsidies change along an elevational gradient and with the introduction of a top aquatic predator. At lower elevations, well-developed terrestrial vegetation provides...
Differential response of vegetation in Hulun Lake region at the northern margin of Asian summer monsoon to extreme cold events of the last deglaciation

NASA Astrophysics Data System (ADS)

Zhang, Shengrui; Xiao, Jule; Xu, Qinghai; Wen, Ruilin; Fan, Jiawei; Huang, Yun; Yamagata, Hideki

2018-06-01

The response of vegetation to extreme cold events during the last deglaciation is important for assessing the impact of possible extreme climatic events on terrestrial ecosystems under future global warming scenarios. Here, we present a detailed record of the development of regional vegetation in the northern margin of Asian summer monsoon during the last deglaciation (16,500-11,000 cal yr BP) based on a radiocarbon-dated high-resolution pollen record from Hulun Lake, northeast China. The results show that the regional vegetation changed from subalpine meadow-desert steppe to mixed coniferous and deciduous forest-typical steppe during the last deglaciation. However, its responses to the Heinrich event 1 (H1) and the Younger Dryas event (YD) were significantly different: during the H1 event, scattered sparse forest was present in the surrounding mountains, while within the lake catchment the vegetation cover was poor and was dominated by desert steppe. In contrast, during the YD event, deciduous forest developed and the proportion of coniferous forest increased in the mountains, the lake catchment was occupied by typical steppe. We suggest that changes in Northern Hemisphere summer insolation and land surface conditions (ice sheets and sea level) caused temperature and monsoonal precipitation variations that contributed to the contrasting vegetation response during the two cold events. We conclude that under future global warming scenarios, extreme climatic events may cause a deterioration of the ecological environment of the Hulun Lake region, resulting in increased coniferous forest and decreased total forest cover in the surrounding mountains, and a reduction in typical steppe in the lake catchment.
Evaluation and assessment of water quality in Likangala River and its catchment area

NASA Astrophysics Data System (ADS)

Chidya, R. C. G.; Sajidu, S. M. I.; Mwatseteza, J. F.; Masamba, W. R. L.

Likangala is one of the perennial rivers in Malawi that flow into a closed Lake Chilwa, a designated wetland ratified by Ramsar Convention in 1997. Earlier work conducted on this river revealed considerable social-economic activities at riverbanks resulting in indiscriminate disposal of wastes. This study intended to evaluate water quality in Likangala River and its catchment area. Water samples were collected thrice (dry, early rainy and mid rainy seasons) and tested for major physico-chemical and microbiological parameters. The EC, pH, and selected ions ( NO3-, PO43-, Na +, K +, Mg 2+, and Ca 2+) were analysed in soil samples obtained in crop fields along the river banks. Elevated EC levels (>1035.00 μS/cm) were measured during mid rainy season at site S15 (Zomba Sewage Works), near and in the lake. Most of the water samples (86%, n = 28) registered phosphate levels above 1.50 mg/L during mid rainy season with a maximum value (10.70 ± 0.01 mg/L) at site S15. Lower amounts (<0.05 mg/L) of Pb 2+, Cd 2+, Cr 3+, Zn 2+ and Mn 2+ were measured at few sites, while Cu 2+ and Ni 2+ were all below detection limits. The water was classified as soft (0-75 mg/L CaCO 3) to moderately hard (75-150 mg/L CaCO 3). The total and fecal coliform counts above the World Health Organisation (2008) and Malawi Bureau of Standards (2005) limits (0 cfu/100 ml) at some sites signified that the water is unsuitable for human consumption without treatment. The study showed that the river is fairly polluted, the effects being significant in the urban area, near and in the lake. This calls for awareness campaigns aiming at behavioural change and integrated control of water, land use and waste management in order to prevent escalation of the effects.
Hydrology, Ecology and Pastoralism in the Sahel: Abrupt Changes in Surface Water Dynamics in a Coupled Natural-Human System

NASA Astrophysics Data System (ADS)

Hanan, N. P.; Prihodko, L.

2008-12-01

The Sahelian region of Africa is situated to the south of the Sahara desert, stretching from Senegal in the West to Sudan in the East. It is an area with semi-arid climate (300-600 mm mean annual precipitation) and long, severe, dry seasons (8-9 months without rain). Sahelian vegetation consists of extensive annual grasslands, with low tree and shrub density (generally < 5% canopy cover). Though rainfall limits the productivity of Sahelian vegetation, this self-same water limitation means that nutrients are relatively available and the nutrient value and digestibility of Sahelian vegetation is much higher than in the adjacent (wetter) savannas to the south. For this reason, the Sahel is a prized grazing resource. However, because domestic animals (cattle, sheep, goats) require regular access to drinking water, most areas of the Sahel are only accessible for grazing during the short rainy season while ephemeral surface pools persist. We will describe observations on one such ephemeral pool in northern Mali which underwent an unexpected transition from ephemeral to perennial during the years of average rainfall (1988-1992) following the severe Sahelian drought of 1985-86. As a result of this transformation a small village has established beside the lake and 5-10 thousand cattle now routinely remain in the watershed throughout the dry season. In this paper the dynamics that may have caused the shift from stable ephemeral lake to stable perennial lake, with no long-term increase in rainfall, will be explored. We will examine hypotheses for the change and how it may have arisen through interactions between hydrology, ecology, climate, humans, their livestock, and land use patterns in the lake catchment. It is likely that biological and physical thresholds were exceeded during the drought to trigger a temporary state change in the lake from ephemeral to perennial, which then triggered a socio-economic reorganization. We hypothesize that the resulting change in land use may now maintain the lake in its 'perennial' state. For how long remains uncertain. We will, furthermore, explore reports from elsewhere in the Sahel suggesting that this phenomenon may not be unique in space or time. If our hypotheses are correct, the interactions and feedbacks operating in our catchment may have broad implications for the ecology and management of the wider Sahel region.
Scenario Tools For Efficient Eutrophication Management

NASA Astrophysics Data System (ADS)

Arheimer, B.; Vastra SP3 Team

Several possible measures are available to reduce diffuse (non-point source) nutri- ent load to surface water and thereby reduce eutrophication. Such measures include changed arable practices and constructions of wetlands and buffer zones in the land- scape, as well as managing lake ecosystems. In some cases, such as for wetlands, there is an intense debate regarding the efficiency of their nutrient reducing capability. In ad- dition, the combined effect of several measures in a catchment is not necessarily equal to their sum. It is therefore important to apply a holistic and integrated catchment approach when applying and evaluating different management strategies. To facili- tate such catchment analyses, the Swedish water management research programme (VASTRA) develop modelling tools addressing both phosphorus (P) and nitrogen (N) dynamics in catchments. During the last three years decision support tools for N man- agement in rivers and lakes have been developed (e.g., HBV-N, BIOLA) and applied in scenarios to demonstrate the effect of various reducing measures. At present, similar tools for P are under development. This presentation will demonstrate the VASTRA tool-box and its applications for efficient eutrophication management.
Radio-echo sounding of 'active' Antarctic subglacial lakes

NASA Astrophysics Data System (ADS)

Siegert, M. J.; Ross, N.; Blankenship, D. D.; Young, D. A.; Greenbaum, J. S.; Richter, T.; Rippin, D. M.; Le Brocq, A. M.; Wright, A.; Bingham, R.; Corr, H.; Ferraccioli, F.; Jordan, T. A.; Smith, B. E.; Payne, A. J.; Dowdeswell, J. A.; Bamber, J. L.

2013-12-01

Repeat-pass satellite altimetry has revealed 124 discrete surface height changes across the Antarctic Ice Sheet, interpreted to be caused by subglacial lake discharges (surface lowering) and inputs (surface uplift). Few of these active lakes have been confirmed by radio-echo sounding (RES) despite several attempts, however. Over the last 5 years, major geophysical campaigns have acquired RES data from several 'active' lake sites, including the US-UK-Australian ICECAP programme in East Antactica and the UK survey of the Institute Ice Stream in West Antarctica. In the latter case, a targeted RES survey of one 'active' lake was undertaken. RES evidence of the subglacial bed beneath 'active' lakes in both East and West Antarctica will be presented, and the evidence for pooled subglacial water from these data will be assessed. Based on this assessment, the nature of 'active' subglacial lakes, and their associated hydrology and relationship with surrounding topography will be discussed, as will the likelihood of further 'active' lakes in Antarctica. Hydraulic potential map of the Byrd Glacier catchment with contours at 5 MPa intervals. Predicted subglacial flowpaths are shown in blue. Subglacial lakes known from previous geophysical surveys are shown as black triangles while the newly discovered 'Three-tier lakes' are shown in dashed black outline. Surface height change features within the Byrd subglacial catchment are shown in outline and are shaded to indicate whether they were rising or falling during the ICESat campaign. Those features are labelled in-line with the numbering system of Smith et al. (J. Glac. 2009).
Sources and deposition of polycyclic aromatic hydrocarbons to western US national parks

EPA Science Inventory

Seasonal snowpack, lichens, and lake sediment cores were collected from fourteen lake catchments in eight western U.S. National Parks and analyzed for sixteen polycyclic aromatic hydrocarbons (PAHs) to determine their current and historical deposition, as well as to identify thei...
Microplastic pollution in lakes and lake shoreline sediments - A case study on Lake Bolsena and Lake Chiusi (central Italy).

PubMed

Fischer, Elke Kerstin; Paglialonga, Lisa; Czech, Elisa; Tamminga, Matthias

2016-06-01

Rivers and effluents have been identified as major pathways for microplastics of terrestrial sources. Moreover, lakes of different dimensions and even in remote locations contain microplastics in striking abundances. This study investigates concentrations of microplastic particles at two lakes in central Italy (Lake Bolsena, Lake Chiusi). A total number of six Manta Trawls have been carried out, two of them one day after heavy winds occurred on Lake Bolsena showing effects on particle distribution of fragments and fibers of varying size categories. Additionally, 36 sediment samples from lakeshores were analyzed for microplastic content. In the surface waters 2.68 to 3.36 particles/m(3) (Lake Chiusi) and 0.82 to 4.42 particles/m(3) (Lake Bolsena) were detected, respectively. Main differences between the lakes are attributed to lake characteristics such as surface and catchment area, depth and the presence of local wind patterns and tide range at Lake Bolsena. An event of heavy winds and moderate rainfall prior to one sampling led to an increase of concentrations at Lake Bolsena which is most probable related to lateral land-based and sewage effluent inputs. The abundances of microplastic particles in sediments vary from mean values of 112 (Lake Bolsena) to 234 particles/kg dry weight (Lake Chiusi). Lake Chiusi results reveal elevated fiber concentrations compared to those of Lake Bolsena what might be a result of higher organic content and a shift in grain size distribution towards the silt and clay fraction at the shallow and highly eutrophic Lake Chiusi. The distribution of particles along different beach levels revealed no significant differences. Copyright © 2016 Elsevier Ltd. All rights reserved.
Combining XAS speciation and Zn isotopes to track past eutrophication in lake sediments : The example of Baldeggersee (Switzerland)

NASA Astrophysics Data System (ADS)

Noël, V. S.; Voegelin, A.; Jouvin, D.; Louvat, P.; gelabert, A.; Mueller, B.; Benedetti, M. F.; Juillot, F.

2011-12-01

Among transition elements, Zn has attracted a great deal of interest because it is an essential nutrient at low concentrations, but it can also be toxic when present at high concentrations in ecosystems (Morel et al., 2003). In the present study, the isotopic signature and crystal-chemical of Zn were followed along a sediment core from a prealpine lake that experienced a marked eutrophication in order to explore the potential of this approach at tracking past environmental conditions of continental lake-catchment systems. Lake Baldeggersee (Luzern, Switzerland) is located at an elevation of 900 m in the Swiss Prealps. It experienced a period of strong eutrophication due to intensive farming in its catchment (Lotter et al., 1997). These led to the formation of varved sediments over one century prior to artificial lake aeration (Wehrli et al., 1997). This enabled us to correlate Zn speciation and isotopic signatures to the history of the water column. Results indicate that both Zn speciation and isotopes are distinct between sediments deposited during mesotrophic and eutrophic conditions in the water column: During the mesotrophic period, sedimentation was mainly detrital and Zn is mainly found associated with clay minerals in the sediments. During the eutrophic period, sedimentation was dominated by biological activity in the lake and Zn mainly occurs as ZnS in the sediments. Zn isotopes recorded these changes in the sedimentation regime, with δ66ZnJMC values around +0.2 % for the sediments of the mesotrophic period and δ66ZnJMC values around 0 % for the sediments of the eutrophic period. Comparison with the results from a study on the seasonal variation of the isotope signature of Zn in settling sediment of another prealpine lake (Peel et al., 2010) suggests that the enrichment in light Zn isotopes in the eutrophic sediments is in line with predominant Zn input with settling biomass (algae). Since lake eutrophication is mainly related to hydrological conditions and occupancy of the related catchment, these results emphasize the great potential of such a combination of molecular level speciation and Zn isotopes in lake sediments cores to track paleo-climatic or paleo-environmental conditions in lake catchments. Lotter A.F., Sturm M., Teranes J.L. and Wehrli B. (1997) Varve fromation since 1885 and high-resolution varve analyses in hypertrophic Baldeggersee (Switzerland) Aquatic Sciences 59, 304-325. Morel F. M. M. and Price N. M. (2003) The biogeochemical cycles of trace metals in the oceans. Science 300, 944-947. Peel K., Weiss D., Sigg L. (2010) Zinc isotope composition of settling particles as a proxy for biogeochemical processes in lakes: Insights from the eutrophic Lake Greifen, Switzerland. Limnol. Oceanogr., 54(5), 1699-1708. Wehrli, B.; Lotter, A.F.; Schaller, T.; Sturm, M. (1997) High-resolution varve studies in Baldeggersee (Switzerland): Project overview and limnological background data. Aquatic Sciences 59, 285-294).
Assessing the response of Emerald Lake, an alpine watershed in Sequoia National Park, California, to acidification during snowmelt by using a simple hydrochemical model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hooper, R.P.; West, C.T.; Peters, N.E.

1990-01-01

A sparsely parameterized hydrochemical model has been developed by using data from Emerald Lake watershed, which is a 120-ha alpine catchment in Sequoia National Park, California. Greater than 90% of the precipitation to this watershed is snow; hence, snowmelt is the dominant hydrologic event. A model which uses a single alkalinity-generating mechanism, primary mineral weathering, was able to capture the pattern of solute concentrations in surface waters during snowmelt. An empirical representation of the weathering reaction, which is based on rock weathering stoichiometry and which uses discharge as a measure of residence time, was included in the model. Results ofmore » the model indicate that current deposition levels would have to be increased between three-fold and eight-fold to exhaust the alkalinity of the lake during snowmelt if their is a mild acidic pulse in the stream at the beginning of snowmelt as was observed during the study period. The acidic pulse in the inflow stream at the onset of snowmelt was less pronounced than acidic pulses observed in the meltwater draining the snowpack at a point using snow lysimeters or in the laboratory. Sulfate concentrations in the stream water were the most constant; chloride and nitrate concentrations increased slightly at the beginning of snowmelt. Additional field work is required to resolve whether an acidic meltwater pulse occurs over a large area as well as at a point or whether, due to physical and chemical processes within the snowpack, the acidic meltwater pulse is attenuated at the catchment scale. The modest data requirements of the model permit its applications to other alpine watersheds that are much less intensively studied than Emerald Lake watershed.« less
Geochemical characterization of the largest upland lake of the Brazilian Amazonia: Impact of provenance and processes

NASA Astrophysics Data System (ADS)

Sahoo, Prafulla Kumar; Guimarães, José Tasso Felix; Souza-Filho, Pedro Walfir Martins; da Silva, Marcio Sousa; Nascimento, Wilson, Júnior; Powell, Mike A.; Reis, Luiza Santos; Pessenda, Luiz Carlos Ruiz; Rodrigues, Tarcísio Magevski; da Silva, Delmo Fonseca; Costa, Vladimir Eliodoro

2017-12-01

Lake Três Irmãs (LTI), the largest upland lake in the Brazilian Amazonia, located in Serra dos Carajás, was characterized using multi-elemental and isotope geochemistry (δ13C and δ15N) to understand the significance of organic and inorganic sources, weathering and sedimentary processes on the distribution of elements in lake bottom (surficial) sediments. Carbon and nitrogen isotopes from sedimentary organic matter suggest C3 terrestrial plants (forests > canga vegetation), macrophytes and freshwater DOC as the main sources. Sediments are depleted in most of the major oxides (except Fe2O3 and P2O5) when compared to upper continental crust (UCC) and their spatial distribution is highly influenced by catchment lithology. Principal Component Analysis revealed that most of the trace elements (Ba, Sr, Rb, Sc, Th, U, Zr, Hf, Nb, Y, V, Cr, Ga, Co, Ni) and REEs are closely correlated with Al and Ti (PC1; Group-1), so their redistribution is less influenced by post-depositional process. This is due to their relative immobility and being hosted by Al-bearing minerals during laterization. High Chemical Index of Alteration (CIA), Mafic Index of Alteration (MIA) and Index of Laterization (IOL) values indicate intense chemical weathering at source areas, but the weathering transformation was better quantified by IOL. A-CN-K plot along with elemental ratios (Al/K, Ti/K, Ti/Zr, La/Al, Cr/Th, Co/Th, La/Sm, La/Gd, Zr/Y, and Eu/Eu*) as well as chondrite-normalized REE patterns show that the detritic sediments are mainly sourced from ferruginous laterites and soils in the catchment, which may have characteristics similar to mafic rocks.
Release of PCBs from Silvretta glacier (Switzerland) investigated in lake sediments and meltwater.

PubMed

Pavlova, P A; Zennegg, M; Anselmetti, F S; Schmid, P; Bogdal, C; Steinlin, C; Jäggi, M; Schwikowski, M

2016-06-01

This study is part of our investigations about the release of persistent organic pollutants from melting Alpine glaciers and the relevance of the glaciers as secondary sources of legacy pollutants. Here, we studied the melt-related release of polychlorinated biphenyls (PCBs) in proglacial lakes and glacier streams of the catchment of the Silvretta glacier, located in the Swiss Alps. To explore a spatial and temporal distribution of chemicals in glacier melt, we combined two approaches: (1) analysing a sediment record as an archive of past remobilization and (2) passive water sampling to capture the current release of PCBs during melt period. In addition, we determined PCBs in a non-glacier-fed stream as a reference for the background pollutant level in the area. The PCBs in the sediment core from the Silvretta lake generally complied with trends of PCB emissions into the environment. Elevated concentrations during the most recent ten years, comparable in level with times of the highest atmospheric input, were attributed to accelerated melting of the glacier. This interpretation is supported by the detected PCB fractionation pattern towards heavier, less volatile congeners, and by increased activity concentrations of the radioactive tracer (137)Cs in this part of the sediment core. In contrast, PCB concentrations were not elevated in the stream water, since no significant difference between pollutant concentrations in the glacier-fed and the non-glacier-fed streams was detected. In stream water, no current decrease of the PCBs with distance from the glacier was observed. Thus, according to our data, an influence of PCBs release due to accelerated glacier melt was only detected in the proglacial lake, but not in the other compartments of the Silvretta catchment.
Pleistocene lake level changes in Western Mongolia

NASA Astrophysics Data System (ADS)

Borodavko, P. S.

2009-04-01

Global cooling in the Early Pleistocene caused extensive continental glaciation in the northern hemisphere including the arid areas of Central Asia. The reduction of temperatures (particularly summer temperatures) reduced evaporation and strengthened the importance of precipitation. The simultaneity of "lakes periods" (pluvials) and stages of glaciation is established experience confirmed by investigations in the west of North America and Russia. In the Mongolian Great Lakes Depression new evidence for similar conditions is found. The Great Lakes Depression is one of the largest in Central Asia, and is divided into 2 main Lakes basins: Hyargas Lake Basin and Uvs Lake Basin. The basin is 600-650 km in length with a width of 200-250 km in the north and 60-100 km in the south. Total catchment area is about 186600 km2. The elevation of the basin floor is from 1700 m a.s.l. to 760 m a.s.l., decreasing to the north and south-east. The depression extends south-north and is bounded by mountains: Tannu-Ola to the north, Hangai to the east; Gobi Altai to the south and Mongolian Altay to the west. The maximum elevation of the mountains is 4000 m a.s.l. There are some mountains with an elevation between 2000 and 3000 m a.s.l in the lake catchment. These mountains are not glaciated today. The geological record [1] suggests the Great Lakes Depression already existed in the Mesozoic, but assumed its modern form only during the Pliocene-Quaternary when tectonic movements caused the uplift of the surrounding mountains. A phase of tectonic stability occurred during the Late Quaternary. The depression is filled by Quaternary fluvial, aeolian and lacustrine deposits (e.g. sand, pebbles). The Neogene deposits are represented by coloured clay, marl, sand and sandstone [1]. Hyargas Lake is the end base level of erosion of the lake group consisting of the Hara-Us Nur, Dorgon, Hara Nur and Airag lakes. Hyargas is one of the largest lakes in Mongolia, with a water surface of 1,407 km2. The lake is 75 km long and 31 km wide. Its mean depth is 47 m, with the deepest point reaching 80 m, and its total water volume is 66,034 km3 and drainage basin 115,500 km2. The only water flowing into it is Galbiyn Hooloi. Hara-Us Nur Lake is a fresh-water (mineralization ca 107-348 mg/l, pH -7.8) basin situated in the Mongolian Great Lakes Depression [2]. Hara-Us Nur is fed by the Kobdo and Buyant rivers, which start in the Mongolian Altay, and outflows via the Chano-Hairkhan River into Hara-Us Nur Lake. Hara-Us Nur is divided by the Ak-Bashi Island into two subbasins. It has a water area of 1857 km2 with a length of 72.2 km and a maximum width of 27 km [4]. The maximum depth is 4 m and the average depth is ca 2 m [5,6]. The terraced lake shores are covered by steppe and desert vegetation. Pharagmites is abundant in the river deltas and close to the shore-line and the shallow-water littoral is covered by rich aquatic vegetation, including Myriophyllum verticulatum, Zannichelia pedunculata, Utricularia vulgaris [3]. Hara-Nur Lake is situated in the desert steppe subzone of the Mongolian Great Lakes Depression. The fresh-water Hara-Nur Lake receives inflow from Hara-Us Nur Lake via the Chano-Hairkhan River. There are two outflows from the lake one outflow is via a 10 km-long channel which flows to the Dzabhan River, which in turn flows into the closed Hyargas Lake. The other outflow is a small semi-permanent stream with flows southward into the closed brackish-water Dorgon Lake. Hara-Nur has a water area of 57,500 ha, with a length of 37 km and a maximum width of ca 24 km. The maximum depth is 7 m and the average depth is ca 4 m. The mean water mineralization is 260 mg/l and the pH is 8.0 [5]. The catchment area is ca 7,200,000 ha. Lake Ureg located in the Mongolian Altay at an altitude of 1425 m.a.s.1., this lake has an area 237.6 km2 and maximum depth of 48 m. Secchi disk transparency is to 8 m. Macrophyte beds cover up to 20 per cent of the lake area, with the common cane sedges and horsetails dominant. The benthic fauna is poor, and only single pecimens of molluscs and amphipods are met. The ichtyofauna is represented by Oreoleuciscus Pewzowi. Previous and modern investigations of these lakes, their morphologies and deposits, allow to specify periods of extension of the lakes and palaeogeographical conditions. Two clear extension periods can be determined in the Mongolian Great Lakes Basin, corresponding to Mid-and Late Pleistocene transgressions. During the Mid-Pleistocene transgression the current Lakes Har-Us Nur, Dorgon Nur, Hara Nur, Airag Nur and Hyargas were integrated to a united lake, with a maximal level at 1265 m. and total water area about 23 158 km2 . The maximal thickness of Mid-Pleistocene lake deposits is 70 m. Late Pleistocene lake sediments are investigated in sections near Dzabhan River and Hyargas Nuur shorelines. They consist of laminated sand, clay and gravel with cryogenic structures at the base and upper part of sections. The mean thickness of Late Pleistocene lake deposits is 20-35 m. The main characteristics of Late Pleistocene lake features are represented by a very bright "lake relief" — obvious steps of shorelines, gravel bands, bars and spits. The specific structure of Late Pleistocene lake cross-sections allows to separate two transgressions within this period. In the first half of the Holocene a minor regression of several meters occurred. Elements of the modern time aeolian relief were still inundated on the north shore of Lake Har-Us Nur. Researches funded by RFBR (Grant 08-05-00037-a) References 1. Geomorfologiya Mongol'skoi Narodnoi Respubliki (Geomorphology of the Mongolian People Republic). M.: Nauka, pp. 135-148. 2. Ozera MNR i ikh mineral'nye resursy (Lakes of MPR and their mineral resources), 1991. Moscow, Nauka, 136 p. 3. Sevastyanov, D.V., Shuvalov, V.F. and Neustrueva, I. Yu. (Eds.), 1994. Limnologiya i paleolimnologiya Mongolii (Limnology and Palaeolimnology of Mongolia). St.Petersburg, Nauka, 304 p. 4. Tarasov, P.E., Harrison, S.P., Saarse, L., Pushenko, M.Ya., Andreev, A.A., Aleshinskaya, Z.V., Davydova, N.N., Dorofeyuk, N.I., Efremov, Yu.V., Khomutova, V.I., Sevastyanov, D.V., Tamosaitis, J., Dorofeyuk, N.I., Efremov, Yu.V., Khomutova, V.I., Sevastyanov, D.V., Tamosaitis, J.,Uspenskaya, O.N., Yakushko, O.F. and Tarasova, I.V., 1994. Lake status records from the Former Soviet Union and Mongolia: Data Base Documentation, World Data Center -A for Paleoclimatology NOAA Paleoclimatology Program, Paleoclimatology Publications Series Report No 2, Boulder, Colorado USA, 274 p. 5. Tserensodnom, Zh., 1971. Mongol orny Nuur. Ulaanbaatar, TUAH, 202 p. 6. Vipper, P., Dorofeyuk, N., Liiva, A., Meteltseva, E., and Sokolovskaya, V., 1981. Palaeogeography of the Central Mongolia during the upper Pleistocene and Holocene. Izv. Akad. Nauk ESSR, Ser. Biol., vol. 30, no. 1, pp. 74-82.
Environmental monitoring of Micro Prespa Lake basin (Western Macedonia, Greece): hydrogeochemical characteristics of water resources and quality trends.

PubMed

Tziritis, Evangelos P

2014-07-01

The Micro Prespa basin is a trilateral catchment area of significant importance with a unique ecosystem closely related to the homonymous lake. In this frame, a fully operational monitoring project was carried out including continuous real-time measurements in Micro Prespa Lake with the use of a multi-sensor probe, as well as periodical sampling and analyses of all available water systems for an extended set of 85 parameters. Four main interacting water systems were identified, including alluvial and karstic aquifers, Micro Prespa Lake and adjacent drainage network. The results outlined that general environmental conditions are satisfying in respect to the relative legislation and the hydrogeochemical signatures. However, trends of environmental pressures were ascertained as a result of natural (geogenic) factors, embracing seasonal peaks for Ni, Pb, and NH4 mainly in groundwater systems. Based on chlorophyll a records, Micro Prespa is classified as oligotrophic to slightly mesotrophic, subjected to seasonal variations. Heavy metal concentrations are low, except Ni which appears to have elevated values during the dry hydrological period. Finally, the hydrogeochemistry of drainage network is primarily influenced by surface runoff of the surrounding mountainous areas, hence elevated phosphorus values of the Aghios Germanos stream are possibly linked with the leaching of the granitic formations on the east.
The Great Lakes Hydrography Dataset: Consistent, binational ...

EPA Pesticide Factsheets

Ecosystem-based management of the Laurentian Great Lakes, which spans both the United States and Canada, is hampered by the lack of consistent binational watersheds for the entire Basin. Using comparable data sources and consistent methods we developed spatially equivalent watershed boundaries for the binational extent of the Basin to create the Great Lakes Hydrography Dataset (GLHD). The GLHD consists of 5,589 watersheds for the entire Basin, covering a total area of approximately 547,967 km2, or about twice the 247,003 km2 surface water area of the Great Lakes. The GLHD improves upon existing watershed efforts by delineating watersheds for the entire Basin using consistent methods; enhancing the precision of watershed delineation by using recently developed flow direction grids that have been hydrologically enforced and vetted by provincial and federal water resource agencies; and increasing the accuracy of watershed boundaries by enforcing embayments, delineating watersheds on islands, and delineating watersheds for all tributaries draining to connecting channels. In addition, the GLHD is packaged in a publically available geodatabase that includes synthetic stream networks, reach catchments, watershed boundaries, a broad set of attribute data for each tributary, and metadata documenting methodology. The GLHD provides a common set of watersheds and associated hydrography data for the Basin that will enhance binational efforts to protect and restore the Great
An inventory of glacial lakes in the Austrian Alps

NASA Astrophysics Data System (ADS)

Buckel, Johannes; Otto, Jan-Christoph; Keuschnig, Markus; Götz, Joachim

2016-04-01

The formation of lakes is one of the consequences of glacier retreat due to climate change in mountain areas. Numerous lakes have formed in the past few decades in many mountain regions around the globe. Some of these lakes came into focus due to catastrophic hazard events especially in the Himalayas and the Andes. Glacial lake development and lifetime is controlled by the complex interplay of glacier dynamics, geomorphological process activity and geological boundary conditions. Besides the hazard potential new lakes in formerly glaciated areas will significantly contribute to a new landscape setting and to changing geomorphologic, hydrologic and ecologic conditions at higher alpine altitudes. We present an inventory of high alpine lakes in the Austrian Alps located above an altitude of 1700 m asl. Most of these lakes are assumed to be of glacial origin, but other causes for development, like mass movements are considered as well. The inventory is a central part of the project FUTURELAKES that aims at modelling the potential development of glacial lakes in Austria (we refer to the presentation by Helfricht et al. during the conference for more details on the modelling part). Lake inventory data will serve as one basis for model validation since modelling is performed on different time steps using glacier inventory data. The purpose of the lake inventory is to get new insights into boundary conditions for lake formation and evolution by analysing existing lake settings. Based on these information the project seeks to establish a model of lake sedimentation after glacier retreat in order to assess the potential lifetime of the new lakes in Austria. Lakes with a minimum size of 1000 m² were mapped using multiple aerial imagery sources. The dataset contains information on location, geometry, dam type, and status of sedimentation for each lake. Additionally, various geologic, geomorphic and morphometric parameters describe the lake catchments. Lake data is related to glacier inventories and paleo-limnologic information to get an idea of the lake formation time. Within the Austrian Alps 1619 lakes were mapped covering an area of more than 25 km². The largest natural lake recorded has an area of 40,000 m². A majority of lakes is classified as bedrock-dammed (48%). 28% of the lakes are moraine-dammed, 21% are embedded in till and 2% landslide-dammed lakes exist. Only three lakes are dammed by existing glacier ice. About 13% of the mapped lakes are considered to be completely silted up. 262 lakes have formed since deglaciation from the maximum glacier extent of the Little Ice Age (LIA, Mid-19th century). The average annual number of lake formation increased significantly since the end of the LIA. Between the different available glacier inventories (1850, 1969, 1998, 2006) this number has grown from 1.1 lakes per year between 1850 and 1969 to 5.6 lakes per year between 2006 and 2014. However, mean lake area decreased from 15,000 m² (1850 - 1969) to 2,500 m² (2006 - 2014).
Long term response of acid-sensitive Vermont Lakes to sulfate deposition

EPA Science Inventory

Atmospheric deposition of sulfur can negatively affect the health of lakes and streams, particularly in poorly buffered catchments. In response to the Clean Air Act Amendments, wet deposition of sulfate decreased more than 35% in Vermont between 1990 and 2008. However, most of ...

The eutrophication history of a naturally eutrophic watercourse

NASA Astrophysics Data System (ADS)

Tammelin, Mira; Kauppila, Tommi

2015-04-01

For efficient inland water protection, it is essential to know the natural states of lakes or, at least, the reference conditions before intensive human impact. The estimation of the natural state is particularly difficult for geologically anomalous areas, where naturally eutrophic lakes are located within nutrient-poorer regions. This is because of the lack of monitoring data and pristine reference lakes and the poor functioning of regional paleoecological nutrient models in such anomalous areas. A paleoecological model that is specifically targeted to the anomalously eutrophic area, however, could be used to interpret the eutrophication histories and natural states of the naturally eutrophic lakes in that area. We applied a targeted paleoecological diatom-total phosphorus transfer function to examine the natural eutrophy and eutrophication history of a central basin and two upstream lakes of the anomalously nutrient-rich Iisalmi watercourse in Eastern Finland. In addition to the nutrient reconstruction based on stratigraphic diatom samples, we studied chrysophyte cyst to diatom ratio, taxonomic diversity and the magnetic susceptibility of the sediment core to find further evidence for possible changes in the lakes and their catchments. The results show that the three lakes are naturally eutrophic with average background total phosphorus levels between 40 μg/l - 60 μg/l. However, human-induced eutrophication has also affected the lakes, which can be seen as rapid changes in the diatom assemblages and magnetic susceptibility between the sediment depths of 40 cm and 90 cm. The modeled lake water total phosphorus concentration has increased less abruptly, approximately 20 μg/l altogether, and the reconstructions of the top sediments mainly correspond well with the water quality observations of the last few decades. The results of this study indicate that a targeted paleoecological nutrient model can be used to interpret the natural state and the eutrophication history of a locality that has anomalous water quality characteristics compared to its surroundings and where regional models perform poorly. Despite their exceptional natural conditions, these localities may often be very important economically, recreationally or historically, which is why we need to be able to focus water protection measures rationally and efficiently to them as well.
Spatial variability of soil water content in the covered catchment at Gårdsjön, Sweden

NASA Astrophysics Data System (ADS)

Nyberg, Lars

1996-01-01

The spatial variability of soil water content was investigated for a 6300 m2 covered catchment on the Swedish west coast. The catchment podzol soil is developed in a sandy - silty till with a mean depth of 43 cm and the dominant vegetation is Norway spruce. The acid precipitation is removed by a plastic roof and replaced with lake water irrigated under the tree canopies. On two occasions, in April and May 1993, TDR measurements were made at 57-73 points in the catchment using 15 and 30 cm long vertically installed probes. The water content pattern at the two dates, which occurred during a relatively dry period, were similar. The range of water content was large, from 5 to 60%. In May 1993 measurements also were made in areas of 10 × 10 m, 1 × 1 m and 0·2 × 0·2 m. The range and standard deviation for the 10 × 10 m area, which apart from a small-scale variability in soil hydraulic properties and fine root distribution also had a heterogeneous micro- and macro-topography, was similar to the range and standard deviation for the catchment. The 1 × 1 m and 0·2 × 0·2 m areas had considerably lower variability. Semi-variogram models for the water content had a range of influence of about 20 m. If data were paired in the east--west direction the semi-variance reflected the topography of the central valley and had a maximum for data pairs with internal distances of 20-40 m. The correlation between soil water content and topographic index, especially when averaged for the eight topographically homogeneous subareas, indicated the macro-topography as the cause of a large part of the water content variability.
The GRASP project - a multidisciplinary study of hydrology and biogeochemistry in a periglacial catchment area

NASA Astrophysics Data System (ADS)

Johansson, Emma; Lindborg, Tobias

2017-04-01

The Arctic region is sensitive to global warming, and permafrost thaw and release of old carbon are examples of processes that may have a positive feedback effect to the global climate system. Quantification and assumptions on future change are often based on model predictions. Such models require cross-disciplinary data of high quality that often is lacking. Biogeochemical processes in the landscape are highly influenced by the hydrology, which in turn is intimately related to permafrost processes. Thus, a multidisciplinary approach is needed when collecting data and setting up field experiments aiming at increase the understanding of these processes. Here we summarize and present data collected in the GRASP, Greenland Analogue Surface Project. GRASP is a catchment-scale field study of the periglacial area in the Kangerlussuaq region, West Greenland, focusing on hydrological and biogeochemical processes in the landscape. The site investigations were initiated in 2010 and have since then resulted in three separate data sets published in ESSD (Earth system and Science Data) each one focusing on i) meteorological data and hydrology, ii) biogeochemistry and iii) geometries of sediments and the active layer. The three data-sets, which are freely available via the PANGAEA data base, enable conceptual and coupled numerical modeling of hydrological and biogeochemical processes. An important strength with the GRASP data is that all data is collected within the same, relatively small, catchment area. This implies that measurements are more easily linked to the right source area or process. Despite the small catchment area it includes the major units of the periglacial hydrological system; a lake, a talik, a supra- and subpermafrost aquifer and, consequently, biogeochemical processes in each of these units may be studied. The new data from GRASP is both used with the aim to increase the knowledge of present day periglacial hydrology and biogeochemistry but also in order to predict consequences within these subjects of future climate change.
Impacts of shore expansion and catchment characteristics on lacustrine thermokarst records in permafrost lowlands, Alaska Arctic Coastal Plain

USGS Publications Warehouse

Lenz, Josefine; Jones, Benjamin M.; Wetterich, Sebastian; Tjallingii, Rik; Fritz, Michael; Arp, Christopher D.; Rudaya, Natalia; Grosse, Guido

2016-01-01

Arctic lowland landscapes have been modified by thermokarst lake processes throughout the Holocene. Thermokarst lakes form as a result of ice-rich permafrost degradation, and they may expand over time through thermal and mechanical shoreline erosion. We studied proximal and distal sedimentary records from a thermokarst lake located on the Arctic Coastal Plain of northern Alaska to reconstruct the impact of catchment dynamics and morphology on the lacustrine depositional environment and to quantify carbon accumulation in thermokarst lake sediments. Short cores were collected for analysis of pollen, sedimentological, and geochemical proxies. Radiocarbon and 210Pb/137Cs dating, as well as extrapolation of measured historic lake expansion rates, were applied to estimate a minimum lake age of ~1400 calendar years BP. The pollen record is in agreement with the young lake age as it does not include evidence of the “alder high” that occurred in the region ~4000 cal yr BP. The lake most likely initiated from a remnant pond in a drained thermokarst lake basin (DTLB) and deepened rapidly as evidenced by accumulation of laminated sediments. Increasing oxygenation of the water column as shown by higher Fe/Ti and Fe/S ratios in the sediment indicate shifts in ice regime with increasing water depth. More recently, the sediment source changed as the thermokarst lake expanded through lateral permafrost degradation, alternating from redeposited DTLB sediments, to increased amounts of sediment from eroding, older upland deposits, followed by a more balanced combination of both DTLB and upland sources. The characterizing shifts in sediment sources and depositional regimes in expanding thermokarst lakes were, therefore, archived in the thermokarst lake sedimentary record. This study also highlights the potential for Arctic lakes to recycle old carbon from thawing permafrost and thermokarst processes.
Sedimentology and geochemistry of a perennially ice-covered epishelf lake in Bunger Hills Oasis, East Antarctica.

PubMed

Doran, P T; Wharton, R A; Lyons, W B; Des Marais, D J; Andersen, D T

2000-01-01

A process-oriented study was carried out in White Smoke lake, Bunger Hills, East Antarctica, a perennially ice-covered (1.8 to 2.8 m thick) epishelf (tidally-forced) lake. The lake water has a low conductivity and is relatively well mixed. Sediments are transferred from the adjacent glacier to the lake when glacier ice surrounding the sediment is sublimated at the surface and replaced by accumulating ice from below. The lake bottom at the west end of the lake is mostly rocky with a scant sediment cover. The east end contains a thick sediment profile. Grain size and delta 13C increase with sediment depth, indicating a more proximal glacier in the past. Sedimentary 210Pb and 137Cs signals are exceptionally strong, probably a result of the focusing effect of the large glacial catchment area. The post-bomb and pre-bomb radiocarbon reservoirs are c. 725 14C yr and c. 1950 14C yr, respectively. Radiocarbon dating indicates that the east end of the lake is >3 ka BP, while photographic evidence and the absence of sediment cover indicate that the west end has formed only over the last century. Our results indicate that the southern ice edge of Bunger Hills has been relatively stable with only minor fluctuations (on the scale of hundreds of metres) over the last 3000 years.
Methane and carbon dioxide emissions from 40 lakes along a north–south latitudinal transect in Alaska

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sepulveda-Jauregui, A.; Walter Anthony, K. M.; Martinez-Cruz, K.

Uncertainties in the magnitude and seasonality of various gas emission modes, particularly among different lake types, limit our ability to estimate methane (CH 4) and carbon dioxide (CO 2) emissions from northern lakes. Here we assessed the relationship between CH 4 and CO 2 emission modes in 40 lakes along a latitudinal transect in Alaska to lakes' physicochemical properties and geographic characteristics, including permafrost soil type surrounding lakes. Emission modes included direct ebullition, diffusion, storage flux, and a newly identified ice-bubble storage (IBS) flux. We found that all lakes were net sources of atmospheric CH 4 and CO 2, butmore » the climate warming impact of lake CH 4 emissions was 2 times higher than that of CO 2. Ebullition and diffusion were the dominant modes of CH 4 and CO 2 emissions, respectively. IBS, ~10% of total annual CH 4 emissions, is the release to the atmosphere of seasonally ice-trapped bubbles when lake ice confining bubbles begins to melt in spring. IBS, which has not been explicitly accounted for in regional studies, increased the estimate of springtime emissions from our study lakes by 320%. Geographically, CH 4 emissions from stratified, mixotrophic interior Alaska thermokarst (thaw) lakes formed in icy, organic-rich yedoma permafrost soils were 6-fold higher than from non-yedoma lakes throughout the rest of Alaska. The relationship between CO 2 emissions and geographic parameters was weak, suggesting high variability among sources and sinks that regulate CO 2 emissions (e.g., catchment waters, pH equilibrium). Total CH 4 emission was correlated with concentrations of soluble reactive phosphorus and total nitrogen in lake water, Secchi depth, and lake area, with yedoma lakes having higher nutrient concentrations, shallower Secchi depth, and smaller lake areas. In conclusion, our findings suggest that permafrost type plays important roles in determining CH 4 emissions from lakes by both supplying organic matter to methanogenesis directly from thawing permafrost and by enhancing nutrient availability to primary production, which can also fuel decomposition and methanogenesis.« less
Methane and carbon dioxide emissions from 40 lakes along a north–south latitudinal transect in Alaska

DOE PAGES

Sepulveda-Jauregui, A.; Walter Anthony, K. M.; Martinez-Cruz, K.; ...

2015-06-02

Uncertainties in the magnitude and seasonality of various gas emission modes, particularly among different lake types, limit our ability to estimate methane (CH 4) and carbon dioxide (CO 2) emissions from northern lakes. Here we assessed the relationship between CH 4 and CO 2 emission modes in 40 lakes along a latitudinal transect in Alaska to lakes' physicochemical properties and geographic characteristics, including permafrost soil type surrounding lakes. Emission modes included direct ebullition, diffusion, storage flux, and a newly identified ice-bubble storage (IBS) flux. We found that all lakes were net sources of atmospheric CH 4 and CO 2, butmore » the climate warming impact of lake CH 4 emissions was 2 times higher than that of CO 2. Ebullition and diffusion were the dominant modes of CH 4 and CO 2 emissions, respectively. IBS, ~10% of total annual CH 4 emissions, is the release to the atmosphere of seasonally ice-trapped bubbles when lake ice confining bubbles begins to melt in spring. IBS, which has not been explicitly accounted for in regional studies, increased the estimate of springtime emissions from our study lakes by 320%. Geographically, CH 4 emissions from stratified, mixotrophic interior Alaska thermokarst (thaw) lakes formed in icy, organic-rich yedoma permafrost soils were 6-fold higher than from non-yedoma lakes throughout the rest of Alaska. The relationship between CO 2 emissions and geographic parameters was weak, suggesting high variability among sources and sinks that regulate CO 2 emissions (e.g., catchment waters, pH equilibrium). Total CH 4 emission was correlated with concentrations of soluble reactive phosphorus and total nitrogen in lake water, Secchi depth, and lake area, with yedoma lakes having higher nutrient concentrations, shallower Secchi depth, and smaller lake areas. In conclusion, our findings suggest that permafrost type plays important roles in determining CH 4 emissions from lakes by both supplying organic matter to methanogenesis directly from thawing permafrost and by enhancing nutrient availability to primary production, which can also fuel decomposition and methanogenesis.« less
Recent changes in aquatic biota in subarctic Fennoscandia - the role of global and local environmental variables

NASA Astrophysics Data System (ADS)

Weckström, Jan; Leppänen, Jaakko; Sorvari, Sanna; Kaukolehto, Marjut; Weckström, Kaarina; Korhola, Atte

2013-04-01

The Arctic, representing a fifth of the earth's surface, is highly sensitive to the predicted future warming and it has indeed been warming up faster than most other regions. This makes the region critically important and highlights the need to investigate the earliest signals of global warming and its impacts on the arctic and subarctic aquatic ecosystems and their biota. It has been demonstrated that many Arctic freshwater ecosystems have already experienced dramatic and unpreceded regime shifts during the last ca. 150 years, primarily driven by climate warming. However, despite the indisputable impact of climate-related variables on freshwater ecosystems other, especially local-scale catchment related variables (e.g. geology, vegetation, human activities) may override the climate signal and become the primary factor in shaping the structure of aquatic ecosystems. Although many studies have contributed to an improved understanding of limnological and hydrobiological features of Artic and subarctic lakes, much information is still needed especially on the interaction between the biotic and abiotic components, i.e. on factors controlling the food web dynamics in these sensitive aquatic ecosystems. This is of special importance as these lakes are of great value in water storage, flood prevention, and maintenance of biodiversity, in addition to which they are vital resources for settlement patterns, food production, recreation, and tourism. In this study we compare the pre-industrial sediment assemblages of primary producers (diatoms and Pediastrum) and primary consumers (cladoceran and chironomids) with their modern assemblages (a top-bottom approach) from 50 subarctic Fennoscandian lakes. We will evaluate the recent regional pattern of changes in aquatic assemblages, and assess how coherent the lakes' responses are across the subarctic area. Moreover, the impact of global (e.g. climate, precipitation) and local (e.g. lake and its catchment characteristics) scale environmental changes on the aquatic biota will be compared and discussed.
Meltwater palaeohydrology of the Baker River basin (Chile/Argentina) during Late Pleistocene deglaciation of the Northern Patagonia Icefield

NASA Astrophysics Data System (ADS)

Thorndycraft, Varyl; Bendle, Jacob; Benito, Gerardo; Sancho, Carlos; Palmer, Adrian; Rodríguez, Xavier

2016-04-01

The Late Pleistocene deglaciation of the Northern Patagonia Icefield (NPI) was characterised by rapid ice sheet thinning and retreat, and the development of large proglacial lake systems characterised by continental scale drainage reversals. In this region, research has focused primarily on the identification of former ice-limits (e.g. moraine ridges) for geochronological analyses, with little attention given to the meltwater palaeohydrology of major river valleys. The Baker River catchment drains the majority of the eastern ice shed of the NPI, with a basin area of 29,000 km2 that includes the large transboundary lakes of General Carrera/Buenos Aires and Cochrane/Puerreydón. The Baker River valley is aligned north to south, crossing the east-west valleys of the main NPI outflow glaciers, and thus represents an important aspect of regional Late Pleistocene palaeogeography. The Baker River valley therefore has the potential to refine regional models of deglaciation through better understanding of relationships between glacier dynamics, ice dammed lakes and meltwater pathways. Here we present geomorphological mapping from the Atlantic-Pacific drainage divide (over 150 km east of the Cordillera) to the lower Baker valley, in order to reconstruct Late Pleistocene palaeohydrology. We provide new mapping of palaeolake shoreline elevations and evidence for glacial lake outburst flood (GLOF) pathways that require a re-evaluation of the currently accepted palaeogeographic models. For example, the palaeohydrological evidence does not support existing models of a unified Buenos Aires/Puerreydón mega-lake at ca. 400m elevation. We propose a relative chronology of palaeohydrological events that help refine the published moraine chronology derived from cosmogenic nuclide exposure dating. Controls on Late Pleistocene meltwater palaeohydrology of the Baker catchment are discussed, including the interplay of glacial processes and regional tectonics, in particular, dynamic topography.
Lake System Development on the northern Tibetan Plateau during the last 12 ka

NASA Astrophysics Data System (ADS)

Ramisch, A. C.; Lockot, G.; Kasper, T.; Schulte, P.; Zhang, Y.; Daut, G.; Haberzettl, T.; Stauch, G.; Hartmann, K.; Zhu, L.; Lehmkuhl, F.; Maeusbacher, R.; Wuennemann, B.; Diekmann, B.

2013-12-01

Lake systems and their drainage basins provide valuable information of late Quaternary palaeo-environmental conditions on the Tibetan Plateau (TP). This information is often difficult to interpret because of a complex forcing-response mechanism of lake systems and their environment. Here we present an analysis of the endogenic mineral precipitation of Lake Heihai (northern TP) and its environmental constrains expressed by the exogenic mineral input. The mineralogical analysis of carbonate phases by means of X-ray diffraction revealed three distinct stages of carbonate precipitation: Aragonite (late Glacial), Monohydrocalcite (early to mid-Holocene) and Mg bearing Calcite (late Holocene). Each phase precipitates under steady state conditions of exogenic mineral input, as determined by a phase space analysis. This suggests a self-organized precipitation process driven by interactions of different ions. Hence, under steady environmental conditions carbonate precipitation is strongly dependent on the ionic compositions of the lake water and thus controlled by sources of the exogenic mineral input. To analyze the provenance of the exogenic mineral input, a Fuzzy C-Means (FCM) Clustering algorithm was performed on the minerogenic detrital fraction of the total mineral content of 57 surface reference samples. Three major sources can be distinguished: (a) glacially mediated, far distant transport originating from SE catchment (b) precipitation generated, close distant runoff originating from the SW catchment and (c) close distant transport of granite weathering products in the northern parts of the drainage basin. A change from the compositional dominance of (b) over (a) to (a) over (b) in lake sediments suggests a transition from rainfall to glacier dominated runoff production and hence drier climate conditions in the study area during the late Holocene. The environmentally controlled changes in the exogenic mineral input are compared to two different lake systems: Lake Donggi Cona (northern Tibetan Plateau) and Lake Nam Co (southern Tibetan Plateau). Major differences occur during two broad Holocene episodes: Until ~6 ka cal BP the differences reach their maximum with a peak around 9.5 cal ka BP. An intensification of the Indian Summer Monsoon (ISM) led to wetter conditions and an increased minerogenic input into Lake Nam Co. Subsequently, the aridification on the TP led to decreased minerogenic input in all three lakes especially since ~2 ka cal BP. Short term divergences from this trend are caused by dry spells on the northern TP. Their timing is quasi synchronous to Holocene Bond events, suggesting a teleconnection of northern TP climate to the circulation of the North Atlantic Ocean.
The glacial/deglacial history of sedimentation in Bear Lake, Utah and Idaho

USGS Publications Warehouse

Rosenbaum, J.G.; Heil, C.W.

2009-01-01

Bear Lake, in northeastern Utah and southern Idaho, lies in a large valley formed by an active half-graben. Bear River, the largest river in the Great Basin, enters Bear Lake Valley ???15 km north of the lake. Two 4-m-long cores provide a lake sediment record extending back ???26 cal k.y. The penetrated section can be divided into a lower unit composed of quartz-rich clastic sediments and an upper unit composed largely of endogenic carbonate. Data from modern fluvial sediments provide the basis for interpreting changes in provenance of detrital material in the lake cores. Sediments from small streams draining elevated topography on the east and west sides of the lake are characterized by abundant dolomite, high magnetic susceptibility (MS) related to eolian magnetite, and low values of hard isothermal remanent magnetization (HIRM, indicative of hematite content). In contrast, sediments from the headwaters of the Bear River in the Uinta Mountains lack carbonate and have high HIRM and low MS. Sediments from lower reaches of the Bear River contain calcite but little dolomite and have low values of MS and HIRM. These contrasts in catchment properties allow interpretation of the following sequence from variations in properties of the lake sediment: (1) ca. 26 cal ka-onset of glaciation; (2) ca. 26-20 cal ka-quasicyclical, millennial-scale variations in the concentrations of hematite-rich glacial fl our derived from the Uinta Mountains, and dolomite- and magnetite-rich material derived from the local Bear Lake catchment (reflecting variations in glacial extent); (3) ca. 20-19 cal ka-maximum content of glacial fl our; (4) ca. 19-17 cal ka-constant content of Bear River sediment but declining content of glacial fl our from the Uinta Mountains; (5) ca. 17-15.5 cal ka-decline in Bear River sediment and increase in content of sediment from the local catchment; and (6) ca. 15.5-14.5 cal ka-increase in content of endogenic calcite at the expense of detrital material. The onset of glaciation indicated in the Bear Lake record postdates the initial rise of Lake Bonneville and roughly corresponds to the Stansbury shoreline. The lake record indicates that maximum glaciation occurred as Lake Bonneville reached its maximum extent ca. 20 cal ka and that deglaciation was under way while Lake Bonneville remained at its peak. The transition from siliciclastic to carbonate sedimentation probably indicates increasingly evaporative conditions and may coincide with the climatically driven fall of Lake Bonneville from the Provo shoreline. Although lake levels fluctuated during the Younger Dryas, the Bear Lake record for this period is more consistent with drier conditions, rather than cooler, moister conditions interpreted from many studies from western North America. Copyright ?? 2009 The Geological Society of America.
Differential Millennial-scale Responses of Terrestrial Carbon Cycling Dynamics to Warming from two Contrasting Lake Catchments in Arctic Alaska

NASA Astrophysics Data System (ADS)

Longo, W. M.; Huang, Y.; Russell, J. M.; Giblin, A. E.; McNichol, A. P.; Xu, L.; Daniels, W.

2016-12-01

Earth's permafrost carbon (C) reservoir is more than twice as large as global atmospheric C and its vulnerability to warming makes it a significant potential feedback to climate change. Predicted rates of warming could result in the release of 5 to 15% of permafrost C to the atmosphere by 2100 (Schuur et al., 2015); however the uncertainty around this estimate hinders our ability to quantify the arctic temperature-carbon feedback. To elucidate the long-term response of terrestrial C to warming in regions underlain by continuous permafrost, we present geologic records of changes in temperature and terrestrial C cycling dynamics from sediment cores from two contrasting lake catchments in arctic Alaska. The sediment records feature independent chronologies, biomarker-based temperature reconstructions, and geochemical measurements of vascular plant biomarkers (lignin phenols) that provide insight into terrestrial carbon quality, its release from permafrost soils and its transit time on the landscape. Our results indicate that both abrupt and sustained increases in temperature over the past 20,000 years resulted in increased carbon normalized yields of lignin phenols (Λ8, Λ6), which indicate increased mobilization of terrestrial organic carbon from permafrost soils. Lignin phenol indicators of terrestrial carbon quality (Ad:Al(s), Ad:Al(v)), indicated that carbon quality decreased with increasing temperature. These results demonstrate covariation between temperature and both the decay of terrestrial organic matter and lignin alteration resulting from dissolution and sorption processes. Compound specific radiocarbon analyses of lignin phenols and their offsets from depositional ages quantify transit times of terrestrial carbon on the landscape. These measurements revealed the presence of a persistent "pre-aged" terrestrial organic carbon pool, which is likely sourced from degrading permafrost. We also observe different responses of terrestrial organic carbon cycling to temperature that depend on landscape characteristics. C cycling responses are pronounced in the low-relief, Pleistocene-aged catchment of lake E5, and more muted in Lake Fog 2, which exists in a higher-relief and younger catchment. Mechanisms differentiating the responses of these catchments are discussed.
Atmospheric flux, transport and mass balance of (210)Pb and (137)Cs radiotracers in different regions of Romania.

PubMed

Begy, R Cs; Kovacs, T; Veres, D; Simon, H

2016-05-01

This study focuses on the determination of (210)Pb and (137)Cs fluxes from different areas in Transylvania, Romania and on the determination of transport and mass balance within the lacustrine system of Red Lake. In order to achieve this, samples were taken from six different locations (Bihor County area, Ighiel area, Red Lake area, Mluha Peatbog, Mohos Peatbog and Zanoaga Rosie Peat bog in the Semenic Mountains) throughout Romania, these being compared to the values of the Danube Delta area. The activity concentrations of the soil samples were measured by gamma spectrometry (HPGe detector) for both (210)Pbtotal, (210)Pbsup ((226)Ra) and (137)Cs, while peat samples were measured by both alpha ((210)Po) spectrometry (PIPS detectors) as well. The mean value for the (210)Pb flux was measured in the Danube Delta region (42±8Bqm(-2) yr(-1)), while the highest was measured in the Semenic Peatbog (227±54Bqm(-2) yr(-1)); the average being 132±8Bqm(-2) yr(-1). In case of (137)Cs the mean was 298±3Bqm(-2) yr(-1), maximum being 1683±15Bqm(-2) yr(-1) in case of Ighiel area and minimum being 32±1Bqm(-2) yr(-1) in the Danube Delta region. In case of the Red Lake, from the total inventory of 410±23Bqm(-2) yr(-1) in the sediments, the loss by outflows is 100±12Bqm(-2) yr(-1), the catchment to lake transfer factor being 0.84%. Copyright © 2016 Elsevier Ltd. All rights reserved.
Temporal patterns of glacial lake evolution in high-mountain environments

NASA Astrophysics Data System (ADS)

Mergili, Martin; Emmer, Adam; Viani, Cristina; Huggel, Christian

2017-04-01

Lakes forming at the front of retreating glaciers are characteristic features of high-mountain areas in a warming climate. Typically, lakes shift from the proglacial phase (lake is in direct contact with glacier) to a glacier-detached (no direct contact) and finally to a non-glacial phase (lake catchment is completely deglaciated) of lake evolution. Apart from changing glacier-lake interactions, each stage is characterized by particular features of lake growth, and by the lake's susceptibility to sudden drainage (lake outburst flood). While this concept appears to be valid globally, some mountain areas are rich in dynamically evolving proglacial lakes, while in others most lakes have already shifted to the glacier-detached or even non-glacial phase. In the present contribution we (i) explore and quantify the history of glacial lake formation and evolution over the past up to 70 years; (ii) assess the current situation of selected contrasting mountain areas (eastern and western European Alps, southern and northern Pamir, Cordillera Blanca); and (iii) link the patterns of lake evolution to the prevailing topographic and glaciological characteristics in order to improve the understanding of high-mountain geoenvironmental change. In the eastern Alps we identify only very few lakes in the proglacial stage. While many lakes appeared and dynamically evolved until the 1980s between 2550 m and 2800 m asl, most of them have lost glacier contact until the 2000s, whereas very few new proglacial lakes appeared at the same time. Even though a similar trend is observed in the higher western Alps, a more dynamic glacial lake evolution is observed there. The arid southern Pamir is characterized by a high number of proglacial lakes, mainly around 4500 m asl. There is strong evidence that glacial lake evolution is, after a highly dynamic phase between the 1970s and approx. 2000, decelerating. Few proglacial lakes exist in the higher and more humid, heavily glacierized northern Pamir, even though there is some evidence for a the recent trend of lake formation and growth. The tropical Cordillera Blanca displays a high, but gradually decreasing share of proglacial lakes. A significant shift of lake elevation was observed: tmost lakes were situated between 4250 m and 4600 m asl in 1950s, while almost half of the lakes are currently situated above 4600 m asl, confirming post-LIA climate change forcing. We attempt to explain the observed trends by investigating the relation of the timing of lake evolution with an interplay of the broad-scale elevational patterns of glaciers and topography, and the local conditions. The findings will assist in anticipating possible future patterns of lake evolution at different scales, relevant for lake outburst risks and water management issues.
Chromophoric Dissolved Organic Matter in Southwestern Greenland Lakes

NASA Astrophysics Data System (ADS)

Osburn, C. L.; Giles, M. E.; Underwood, G. J. C.

2014-12-01

Dissolved organic matter (DOM) is an important property of Arctic lake ecosystems, originating from allochthonous inputs from catchments and autochthonous production by plankton in the water column. Little is known about the quality of DOM in Arctic lakes that lack substantial inputs from catchments and such lakes are abundant in southwestern Greenland. Colored dissolved organic matter (CDOM), the fraction that absorbs ultraviolet (UV) and visible light, is the controlling factor for the optical properties of many surface waters and as well informs on the quality of DOM. We examined the quality of CDOM in 21 lakes in southwestern Greenland, from the ice sheet to the coast, as part of a larger study examining the role of DOM in regulating microbial communities in these lakes. DOM was size fractioned and absorbance and fluorescence was measured on each size fraction, as well as on bulk DOM. The specific ultraviolet absorbance (SUVA) at 254 nm (SUVA254), computed by normalizing absorption (a254) to dissolved organic carbon (DOC) concentration, provided an estimate of the aromatic carbon content of DOM. SUVA values were generally <2, indicating low aromatic content. Parallel factor analysis (PARAFAC) of CDOM fluorescence was used to determine the relative abundance of allochthonous and autochthonous DOM in all size fractions. Younger lakes near the ice sheet and lakes near the coast had lower amounts of CDOM and appeared more microbial in quality. However, lakes centrally located between the ice sheet and the coast had the highest CDOM concentrations and exhibited strong humic fluorescence. Overall distinct differences in CDOM quality were observed between lake locations and among DOM size fractions.
Repeat synoptic sampling reveals drivers of change in carbon and nutrient chemistry of Arctic catchments

NASA Astrophysics Data System (ADS)

Zarnetske, J. P.; Abbott, B. W.; Bowden, W. B.; Iannucci, F.; Griffin, N.; Parker, S.; Pinay, G.; Aanderud, Z.

2017-12-01

Dissolved organic carbon (DOC), nutrients, and other solute concentrations are increasing in rivers across the Arctic. Two hypotheses have been proposed to explain these trends: 1. distributed, top-down permafrost degradation, and 2. discrete, point-source delivery of DOC and nutrients from permafrost collapse features (thermokarst). While long-term monitoring at a single station cannot discriminate between these mechanisms, synoptic sampling of multiple points in the stream network could reveal the spatial structure of solute sources. In this context, we sampled carbon and nutrient chemistry three times over two years in 119 subcatchments of three distinct Arctic catchments (North Slope, Alaska). Subcatchments ranged from 0.1 to 80 km2, and included three distinct types of Arctic landscapes - mountainous, tundra, and glacial-lake catchments. We quantified the stability of spatial patterns in synoptic water chemistry and analyzed high-frequency time series from the catchment outlets across the thaw season to identify source areas for DOC, nutrients, and major ions. We found that variance in solute concentrations between subcatchments collapsed at spatial scales between 1 to 20 km2, indicating a continuum of diffuse- and point-source dynamics, depending on solute and catchment characteristics (e.g. reactivity, topography, vegetation, surficial geology). Spatially-distributed mass balance revealed conservative transport of DOC and nitrogen, and indicates there may be strong in-stream retention of phosphorus, providing a network-scale confirmation of previous reach-scale studies in these Arctic catchments. Overall, we present new approaches to analyzing synoptic data for change detection and quantification of ecohydrological mechanisms in ecosystems in the Arctic and beyond.
A 500 year sediment lake record of anthropogenic and natural inputs to Windermere (English Lake District) using double-spike lead isotopes, radiochronology, and sediment microanalysis.

PubMed

Miller, Helen; Croudace, Ian W; Bull, Jonathan M; Cotterill, Carol J; Dix, Justin K; Taylor, Rex N

2014-07-01

A high-resolution record of pollution is preserved in recent sediments from Windermere, the largest lake in the English Lake District. Data derived from X-ray core scanning (validated against wavelength dispersive X-ray fluorescence), radiochronological techniques ((210)Pb and (137)Cs) and ultrahigh precision, double-spike mass spectrometry for lead isotopes are combined to decipher the anthropogenic inputs to the lake. The sediment record suggests that while most element concentrations have been stable, there has been a significant increase in lead, zinc, and copper concentrations since the 1930s. Lead isotope down-core variations identify three major contributory sources of anthropogenic (industrial) lead, comprising gasoline lead, coal combustion lead (most likely source is coal-fired steam ships), and lead derived from Carboniferous Pb-Zn mineralization (mining activities). Periods of metal workings do not correlate with peaks in heavy metals due to the trapping efficiency of up-system lakes in the catchment. Heavy metal increases could be due to flood-induced metal inwash after the cessation of mining and the weathering of bedrock in the catchment. The combination of sediment analysis techniques used provides new insights into the pollutant depositional history of Windermere and could be similarly applied to other lake systems to determine the timing and scale of anthropogenic inputs.
One century sedimentary record of lead and zinc pollution in Yangzong Lake, a highland lake in southwestern China.

PubMed

Zhang, Enlou; Liu, Enfeng; Shen, Ji; Cao, Yanmin; Li, Yanling

2012-01-01

Reconstruction of trace metal pollution histories and sources may help us to regulate current pollutant discharge. This is especially important for the highland lakes in southwestern China, which are facing trace metals pollution. We present sedimentary records of 11 metals accumulated in Yangzong Lake since the 1870's, a highland lake in southwestern China. Pollution of lead and zinc (Pb and Zn) was differentiated based on principal component analysis, geochemical normalization, and lead isotope ratios. Nearly all the metals as well as grain size composition show generally constant values before the mid-1980's, denoting stable detrital input in the catchment. Fluctuations in the concentrations of the metals as well as grain size composition since the mid-1980's indicate an increase in soil erosion with strengthened human disturbance in the catchment. After geochemical normalization, Pb and Zn showed constant values before 1990 AD and then a gradual increase in parallel with the variations in 208Pb/206Pb and 207Pb/206Pb ratios, indicating that Pb and Zn pollution occurred. Combining the data of 208pb/206Pb and 207Pb/6Pb ratios in the sediments of Yangzong Lake, leaded gasoline, Pb-Zn ore and coal, and consumption or production historical trends, we deduced that the enhanced Pb and Zn pollution in Yangzong Lake is caused primarily by ore mining and refining.
Water Quality Investigations at Lake Merritt in Oakland, California

NASA Astrophysics Data System (ADS)

Carter, G.; Casino, C.; Johnson, K.; Huang, J.; Le, A.; Truisi, V. M.; Turner, D.; Yanez, F.; Yu, J. F.; Unigarro, M.; Vue, G.; Garduno, L.; Cuff, K.

2005-12-01

Lake Merritt is a saltwater tidal lagoon that forms a portion of a wildlife refuge in downtown Oakland, California. The general area was designated as the nation's first wildlife refuge in 1869, and is currently the home to over 90 species of migrating waterfowl, as well as a variety of aquatic wildlife. Situated within an area composed of compacted marine sediment located near the center of Oakland, Lake Merritt also serves as a major local catchment basin, receiving significant urban runoff from a 4,650 acre local watershed through 60 storm drains and four culverted creeks. Due to factors related to its geographical location, Lake Merritt has suffered from poor water quality at various times throughout its history. In fact, in May of 1999 the US Environmental Protection Agency designated Lake Merritt as a body of water whose beneficial uses are impaired, mainly due to high levels of trash and low levels of dissolved oxygen. As a contribution to continuing efforts to monitor and assess water quality of the Lake, we began a water quality investigation during the Summer of 2005, which included the measurement of dissolved oxygen concentrations of samples collected near its surface at over 85 different locations. These measurements were made using a sensor attached to a PASCO data- logger. The sensor measures the electric current produced by a chemical reaction in its probe, which is composed of a platinum cathode and a silver anode surrounded by an electrolyte solution. Results of these measurements were statistically analyzed, mapped, and then used in assessing the quality of Lake Merritt's water, particularly in relation to supporting aquatic biota. Preliminary analysis of results obtained so far indicates that the highest quality waters in Lake Merritt occur in areas that are closest to a source of San Francisco Bay water, as well as those areas nearby where water circulation is robust. Significantly high levels of dissolved oxygen were measured in an area that has the greatest number and diversity of organisms as indicated through visual observation, which is located where marine waters flow directly into the Lake. In addition, high levels of dissolved oxygen were measured at two sites along an approximately 500 meters stretch of the Lake's eastern shoreline, where swift moving currents were observed. Dissolved oxygen levels were lowest in areas where storm drain runoff waters flow into the Lake, as well as those that include trash-filled, stagnant sections. Overall, our work has generated information that may be used to better understand important factors that affect Lake Merritt's water quality. Such studies should be continued in the future and used to help maintain a healthy ecosystem in and around Lake Merritt.
A 15,400-year record of environmental magnetic variations in sub-alpine lake sediments from the western Nanling Mountains in South China: Implications for palaeoenvironmental changes

NASA Astrophysics Data System (ADS)

Zhong, Wei; Wei, Zhiqiang; Shang, Shentan; Ye, Susu; Tang, Xiaowen; Zhu, Chan; Xue, Jibin; Ouyang, Jun; Smol, John P.

2018-04-01

A detailed environmental magnetic investigation has been performed on a sub-alpine sedimentary succession deposited over the past 15,400 years in Daping Swamp in the western Nanling Mountains of South China. Magnetic parameters reveal that fine grains of pseudo-single domain (PSD) magnetite or titanomagnetite are the dominant magnetic minerals in the lake sediments and surface soils collected from the catchment, which suggests that magnetic minerals in lake sediments mainly originated from surface soil erosion of the catchment. Variation of surface runoff caused by rainfall is interpreted as the main process for transportation of weathered soils into the lake. In the Last Deglacial period (LGP, 15,400-11,500 cal a BP), the influx of magnetic minerals of detrital material may have been significantly affected by the severe dry and cold conditions of the Last Glacial Maximum. Stabilised conditions of the catchment associated with increased vegetation coverage (e.g., 8000-4500 and 2500-1000 cal a BP) limited the input of magnetic minerals. Intensive soil erosion caused by increased human activity may have given rise to abnormal increases in multiple magnetic parameters after 1000 cal a BP. Because changes in runoff and vegetation coverage are closely related to Asian summer monsoon (ASM) intensity, the sedimentary magnetism of Daping Swamp provides another source of information to investigate the evolution of the ASM.

How wet is wet? Strontium isotopes as paleo-lake level indicators in the Chew Bahir basin (S-Ethiopia)

NASA Astrophysics Data System (ADS)

Junginger, A.; Vonhof, H.; Foerster, V. E.; Asrat, A.; Cohen, A. S.; Lamb, H. F.; Schaebitz, F.; Trauth, M. H.

2016-12-01

A major challenge in paleo-anthropology is to understand the impact of climatic changes on human evolution. The Hominin Sites and Paleo-lakes Drilling Project (HSPDP) is currently meeting that challenge by providing records that cover the last 3.7 Ma of paleoenvironmental change all located in close proximity to key paleo-anthropological findings in East Africa. One of the cored climatic archives comes from the dried up Chew Bahir basin in southern Ethiopia, where duplicate sediment cores, each 280 m long, are expected to provide valuable insights about East African environmental variability during the last >500 ka. The lake basins in the eastern branch of the East African Rift System today contain mainly shallow and alkaline lakes. However, paleo-shorelines in the form of wave cut notches, shell beds, and beach ridges are common morphological evidences for deep freshwater lakes that have filled the basins up to their overflow level during pronounced humid episodes, such as the African Humid Period (AHP, 15-5 ka). Unfortunately, further back in time, many of those morphological features disappear due to erosion and the estimation of paleo-water depths depend merely on qualitative proxies from core analyses. We here present a new method that shows high potential to translate qualitative proxy signals from sediment core analyses to quantitative climate signals in the Ethiopian Rift. The method aims at water level reconstruction of multiple paleo-lake episodes in the Chew Bahir basin using strontium isotope ratios (87Sr/86Sr, SIR) in lacustrine fossils and microfossils. SIR preserved in lacustrine fossils reflect the lithology of the drained catchment. The catchment of Chew Bahir consists mainly of Precambrian basement rocks producing high SIR in the lake waters. During humid periods, its catchment enlarged when higher elevated paleo-lakes Abaya, Chamo and Awassa were cascading down into Chew Bahir. These basins drain mainly volcanic rocks producing low SIR. First results show such an onset of hydrological connectivity in a pronounced reduction of SIR in the lacustrine fossils of Chew Bahir when the last AHP set in. This new method may help to quantify paleo-lake levels beyond the past 20 ka and may also detect migrational barriers or routes due to the occurrence of synchronous large, connected and deep paleo-lakes.
Scaling relationships among drivers of aquatic respiration from the smallest to the largest freshwater ecosystems

USGS Publications Warehouse

Hall, Ed K; Schoolmaster, Donald; Amado, A.M; Stets, Edward G.; Lennon, J.T.; Domaine, L.; Cotner, J.B.

2016-01-01

To address how various environmental parameters control or constrain planktonic respiration (PR), we used geometric scaling relationships and established biological scaling laws to derive quantitative predictions for the relationships among key drivers of PR. We then used empirical measurements of PR and environmental (soluble reactive phosphate [SRP], carbon [DOC], chlorophyll a [Chl-a)], and temperature) and landscape parameters (lake area [LA] and watershed area [WA]) from a set of 44 lakes that varied in size and trophic status to test our hypotheses. We found that landscape-level processes affected PR through direct effects on DOC and temperature and indirectly via SRP. In accordance with predictions made from known relationships and scaling laws, scale coefficients (the parameter that describes the shape of a relationship between 2 variables) were found to be negative and have an absolute value 1, others <1). We also found evidence of a significant relationship between temperature and SRP. Because our dataset included measurements of respiration from small pond catchments to the largest body of freshwater on the planet, Lake Superior, these findings should be applicable to controls of PR for the great majority of temperate aquatic ecosystems.
A multi-method study of regional groundwater circulation in the Ordos Plateau, NW China

NASA Astrophysics Data System (ADS)

Jiang, Xiao-Wei; Wan, Li; Wang, Xu-Sheng; Wang, Dan; Wang, Heng; Wang, Jun-Zhi; Zhang, Hong; Zhang, Zhi-Yuan; Zhao, Ke-Yu

2018-01-01

The Ordos Basin is one of the most intensively studied groundwater basins in China. The Ordos Plateau, located in the north part of the Ordos Basin, is ideal to study the pattern of regional groundwater circulation induced by water-table undulations due to the wavy topography and the relatively simple aquifer systems with macroscopically homogeneous sandstone. In catchments located near the first-order divide, the water table is found to be a subdued replica of the topography, and the nonclosed water-table contours in topographic highs of a catchment are indicative of regional groundwater outflow to other catchments. In topographic lows, groundwater-fed lakes/rivers, topography-driven flowing wells, water-loving and/or salt-tolerant vegetation, and soap holes are all indicative of discharge areas. In discharge areas, although groundwater inflow from recharge areas is relatively stable, seasonal variations in groundwater recharge and evapotranspiration lead to significant seasonal fluctuations in the water table, which can be used to estimate groundwater inflow and evapotranspiration rates based on water balance at different stages of water-table change. In the lowest reaches of a complex basin, superposition of local flow systems on regional flow systems has been identified based on groundwater samples collected from wells with different depths and geophysical measurements of apparent resistivity, both of which can be used for characterizing groundwater flow systems. This study enhances understanding of the pattern of regional groundwater circulation in the Ordos Plateau, and also tests the effectiveness of methods for groundwater flow-system characterization.
Modeled Sources, Transport, and Accumulation of Dissolved Solids in Water Resources of the Southwestern United States.

PubMed

Anning, David W

2011-10-01

Information on important source areas for dissolved solids in streams of the southwestern United States, the relative share of deliveries of dissolved solids to streams from natural and human sources, and the potential for salt accumulation in soil or groundwater was developed using a SPAtially Referenced Regressions On Watershed attributes model. Predicted area-normalized reach-catchment delivery rates of dissolved solids to streams ranged from <10 (kg/year)/km(2) for catchments with little or no natural or human-related solute sources in them to 563,000 (kg/year)/km(2) for catchments that were almost entirely cultivated land. For the region as a whole, geologic units contributed 44% of the dissolved-solids deliveries to streams and the remaining 56% of the deliveries came from the release of solutes through irrigation of cultivated and pasture lands, which comprise only 2.5% of the land area. Dissolved-solids accumulation is manifested as precipitated salts in the soil or underlying sediments, and (or) dissolved salts in soil-pore or sediment-pore water, or groundwater, and therefore represents a potential for aquifer contamination. Accumulation rates were <10,000 (kg/year)/km(2) for many hydrologic accounting units (large river basins), but were more than 40,000 (kg/year)/km(2) for the Middle Gila, Lower Gila-Agua Fria, Lower Gila, Lower Bear, Great Salt Lake accounting units, and 247,000 (kg/year)/km(2) for the Salton Sea accounting unit.
Modeled Sources, Transport, and Accumulation of Dissolved Solids in Water Resources of the Southwestern United States1

PubMed Central

Anning, David W

2011-01-01

Abstract Information on important source areas for dissolved solids in streams of the southwestern United States, the relative share of deliveries of dissolved solids to streams from natural and human sources, and the potential for salt accumulation in soil or groundwater was developed using a SPAtially Referenced Regressions On Watershed attributes model. Predicted area-normalized reach-catchment delivery rates of dissolved solids to streams ranged from <10 (kg/year)/km2 for catchments with little or no natural or human-related solute sources in them to 563,000 (kg/year)/km2 for catchments that were almost entirely cultivated land. For the region as a whole, geologic units contributed 44% of the dissolved-solids deliveries to streams and the remaining 56% of the deliveries came from the release of solutes through irrigation of cultivated and pasture lands, which comprise only 2.5% of the land area. Dissolved-solids accumulation is manifested as precipitated salts in the soil or underlying sediments, and (or) dissolved salts in soil-pore or sediment-pore water, or groundwater, and therefore represents a potential for aquifer contamination. Accumulation rates were <10,000 (kg/year)/km2 for many hydrologic accounting units (large river basins), but were more than 40,000 (kg/year)/km2 for the Middle Gila, Lower Gila-Agua Fria, Lower Gila, Lower Bear, Great Salt Lake accounting units, and 247,000 (kg/year)/km2 for the Salton Sea accounting unit. PMID:22457583
Nutrient pressures and ecological responses to nutrient loading reductions in Danish streams, lakes and coastal waters

NASA Astrophysics Data System (ADS)

Kronvang, Brian; Jeppesen, Erik; Conley, Daniel J.; Søndergaard, Martin; Larsen, Søren E.; Ovesen, Niels B.; Carstensen, Jacob

2005-03-01

The Danish National Aquatic Monitoring and Assessment Programme (NOVA) was launched in 1988 following the adoption of the first Danish Action Plan on the Aquatic Environment in 1987 with the aim to reduce by 50% the nitrogen (N) loading and by 80% the phosphorus (P) loading to the aquatic environment. The 14 years of experience gathered from NOVA have shown that discharges of total N (TN) and P (TP) from point sources to the Danish Aquatic Environment have been reduced by 69% (N) and 82% (P) during the period 1989 2002. Consequently, the P concentration has decreased markedly in most Danish lakes and estuaries. Considerable changes in agricultural practice have resulted in a reduction of the net N-surplus from 136 to 88 kg N ha-1 yr-1 (41%) and the net P-surplus from 19 to 11 kg P ha-1 yr-1 (42%) during the period 1985 2002. Despite these efforts Danish agriculture is today the major source of both N (>80%) and P (>50%) in Danish streams, lakes and coastal waters. A non-parametric statistical trend analysis of TN concentrations in streams draining dominantly agricultural catchments has shown a significant (p<0.05) downward trend in 48 streams with the downward trend being stronger in loamy compared to sandy catchments, and more pronounced with increasing dominance of agricultural exploitation in the catchments. In contrast, a statistical trend analysis of TP concentrations in streams draining agricultural catchments did not reveal any significant trends. The large reduction in nutrient loading from point and non-point sources has in general improved the ecological conditions of Danish lakes in the form of increased summer Secchi depth, decreased chlorophyll a and reduced phytoplankton biomass. Major changes have also occurred in the fish communities in lakes, with positive cascading effects on water quality. In Danish estuaries and coastal waters only a few significant improvements in the ecological quality have been observed, although it is expected that the observed reduced nutrient concentrations are likely to improve the ecological quality of estuaries and coastal waters in Denmark in the long term.
Holocene rainfall runoff in the central Ethiopian highlands and evolution of the River Nile drainage system as revealed from a sediment record from Lake Dendi

NASA Astrophysics Data System (ADS)

Wagner, Bernd; Wennrich, Volker; Viehberg, Finn; Junginger, Annett; Kolvenbach, Anne; Rethemeyer, Janet; Schaebitz, Frank; Schmiedl, Gerhard

2018-04-01

A 12 m long sediment sequence was recovered from the eastern Dendi Crater lake, located on the central Ethiopian Plateau and in the region of the Blue Nile headwaters. 24 AMS radiocarbon dates from bulk organic carbon samples indicate that the sediment sequence spans the last ca. 12 cal kyr BP. Sedimentological and geochemical data from the sediment sequence that were combined with initial diatom information show only moderate change in precipitation and catchment runoff during that period, probably due to the elevated location of the study region in the Ethiopian highlands. Less humid conditions prevailed during the Younger Dryas (YD). After the return to full humid conditions of the African Humid Period (AHP), a 2 m thick tephra layer, probably originating from an eruption of the Wenchi crater 12 km to the west of the lake, was deposited at 10.2 cal kyr BP. Subsequently, single thin horizons of high clastic matter imply that short spells of dry conditions and significantly increased rainfall, respectively, superimpose the generally humid conditions. The end of the AHP is rather gradual and precedes relatively stable and less humid conditions around 3.9 cal kyr BP. Subsequently, slightly increasing catchment runoff led to sediment redeposition, increasing nutrient supply, and highest trophic states in the lake until 1.5 cal kyr BP. A highly variable increase in clastic matter indicates fluctuating and increasing catchment runoff over the last 1500 years. The data from Lake Dendi show, in concert with other records from the Nile catchment and the Eastern Mediterranean Sea (EMS), that the Blue Nile discharge was relatively high between ca. 10.0 and 8.7 cal kyr BP. Subsequent aridification peaked with some regional differences between ca. 4.0 and 2.6 cal kyr BP. Higher discharge in the Blue Nile hydraulic regime after 2.6 cal kyr BP is probably triggered by more local increase in rainfall, which is tentatively caused by a change in the influence of the Indian Ocean monsoon.
New insights on water level variability for Lake Turkana for the past 15 ka and at 150 ka from relict beaches

NASA Astrophysics Data System (ADS)

Forman, S. L.; Wright, D.

2015-12-01

Relict beaches adjacent to Lake Turkana provide a record of water level variability for the Late Quaternary. This study focused on deciphering the geomorphology, sedimentology, stratigraphy and 14C chronology of strand plain sequences in the Kalokol and Lothagam areas. Nine >30 m oscillations in water level were documented between ca. 15 and 4 ka. The earliest oscillation between ca. 14.5 and 13 ka is not well constrained with water level to at least 70 m above the present surface and subsequently fell to at least 50 m. Lake level increased to ~ 90 m between ca. 11.2 and 10.4 ka, post Younger Dryas cooling. Water level fell by >30 m by 10.2 ka, with another potential rise at ca. 8.5 ka to >70 m above current level. Lake level regressed by > 40 m at 8.2 ka coincident with cooling in the equatorial Eastern Atlantic Ocean. Two major >70 m lake level oscillations centered at 6.6 and 5.2 ka may reflect enhanced convection with warmer sea surface temperatures in the Western Indian Ocean. The end of the African Humid Period occurred from ca. 8.0 to 4.5 ka and was characterized by variable lake level (± > 40 m), rather than one monotonic fall in water level. This lake level variability reflects a complex response to variations in the extent and intensity of the East and West African Monsoons near geographic and topographic limits within the catchment of Lake Turkana. Also, for this closed lake basin excess and deficits in water input are amplified with a cascading lake effect in the East Rift Valley and through the Chew Bahir Basin. The final regression from a high stand of > 90 m began at. 5.2 ka and water level was below 20 m by 4.5 ka; and for the remainder of the Holocene. This sustained low stand is associated with weakening of the West African Monsoon, a shift of the mean position of Congo Air Boundary west of the Lake Turkana catchment and with meter-scale variability in lake level linked to Walker circulation across the Indian Ocean. A surprising observation is the presence of older, heavily dissected relict beaches up to 175 m above current lake level, which host beach rock and well developed carbonate rich soils. A preliminary OSL age of 145 ka, indicates that these surface are associated with MOI stage 6 and 5. The higher elevation of these beach either reflect tectonic up-warping, a change in elevation of the outlet to the Blue Nile or combination of these processes.
The impacts of prescribed moorland burning on water colour and dissolved organic carbon: a critical synthesis.

PubMed

Holden, J; Chapman, P J; Palmer, S M; Kay, P; Grayson, R

2012-06-30

Discolouration of natural surface waters due to the humic component of dissolved organic carbon (DOC) is a costly problem for water supply companies. This paper reviews what is known about the impacts of prescribed moorland vegetation burning on water colour. Relevant research has taken place at three scales: laboratory experiments on peat cores, plot scale sampling of soil waters and catchment scale sampling of stream waters. While laboratory studies suggest burning increases colour production, the evidence from catchment and plot studies is contradictory. Plot studies suggest colour production may decrease or remain unchanged following burning although there is evidence for some transient changes. Catchment studies suggest prescribed moorland burning causes stream water colour to increase, although in most cases the evidence is not clear cut since most studies could not clearly disentangle the effects of burning from those of vegetation cover. The differences in findings between plot and catchment studies may be explained by: i) the short-term nature of some studies which do not measure long-term response and recovery times to burning; ii) the lack of colour measurements from shallow soil depths which contribute more to streamflow than soil water from deeper in the peat; and iii) the possibility of hydrological interactions occurring between different experimental plots at some sites. Additionally, the increase in recent patch burning in some catchments that has been statistically attributed by some authors to increases in stream water colour cannot be reconciled with theoretical calculations. When dilution with waters derived from other parts of the catchment are taken into account, large values of colour have to be theoretically derived from those recently burnt areas that occupy a small proportion of the catchment area in order to balance the change in stream water colour observed in recent years. Therefore, much further process-based work is required to properly investigate whether prescribed vegetation burning is a direct driver of enhanced colour and DOC in upland streams, rivers and lakes. Copyright © 2012 Elsevier Ltd. All rights reserved.
Copper content in lake sediments as a tracer of urban emissions: evaluation through a source-transport-storage model.

PubMed

Cui, Qing; Brandt, Nils; Sinha, Rajib; Malmström, Maria E

2010-06-01

A coupled source-transport-storage model was developed to determine the origin and path of copper from materials/goods in use in the urban drainage area and the fate of copper in local recipient lakes. The model was applied and tested using five small lakes in Stockholm, Sweden. In the case of the polluted lakes Råcksta Träsk, Trekanten and Långsjön, the source strengths of copper identified by the model were found to be well linked with independently observed copper contents in the lake sediments through the model. The model results also showed that traffic emissions, especially from brake linings, dominated the total load in all five cases. Sequential sedimentation and burial proved to be the most important fate processes of copper in all lakes, except Råcksta Träsk, where outflow dominated. The model indicated that the sediment copper content can be used as a tracer of the urban diffuse copper source strength, but that the response to changes in source strength is fairly slow (decades). Major uncertainties in the source model were related to management of stormwater in the urban area, the rate of wear of brake linings and weathering of copper roofs. The uncertainty of the coupled model is in addition affected mainly by parameters quantifying the sedimentation and bury processes, such as particulate fraction, settling velocity of particles, and sedimentation rate. As a demonstration example, we used the model to predict the response of the sediment copper level to a decrease in the copper load from the urban catchment in one of the case study lakes. Copyright (c) 2010 Elsevier B.V. All rights reserved.
Hydrological Relevant Parameters from Remote Sensing - Spatial Modelling Input and Validation Basis

NASA Astrophysics Data System (ADS)

Hochschild, V.

2012-12-01

This keynote paper will demonstrate how multisensoral remote sensing data is used as spatial input for mesoscale hydrological modeling as well as for sophisticated validation purposes. The tasks of Water Resources Management are subject as well as the role of remote sensing in regional catchment modeling. Parameters derived from remote sensing discussed in this presentation will be land cover, topographical information from digital elevation models, biophysical vegetation parameters, surface soil moisture, evapotranspiration estimations, lake level measurements, determination of snow covered area, lake ice cycles, soil erosion type, mass wasting monitoring, sealed area, flash flood estimation. The actual possibilities of recent satellite and airborne systems are discussed, as well as the data integration into GIS and hydrological modeling, scaling issues and quality assessment will be mentioned. The presentation will provide an overview of own research examples from Germany, Tibet and Africa (Ethiopia, South Africa) as well as other international research activities. Finally the paper gives an outlook on upcoming sensors and concludes the possibilities of remote sensing in hydrology.
Export of excess Cl by river systems indicates long-term changes to groundwater-surface water interaction

NASA Astrophysics Data System (ADS)

Cartwright, Ian; Hofmann, Harald; Gilfedder, Ben

2013-04-01

Understanding whether catchments are in chemical mass balance is important in understand long-term groundwater-surface water interactions. The mass balance of a conservative solute such as Cl in a catchment is: P*Cl(P) = SW*Cl(SW) + GW*Cl(GW) + dST*Cl(ST) where P, SW, and GW, are net precipitation, surface water outflows, and groundwater outflows and dST accounts for changes to water held in storage, primarily in the groundwater system. Cl() is the concentration of Cl in the various water components. Precipitation and river discharges are commonly well constrained and in many regions there are also rainfall, groundwater, and surface water geochemistry data. Groundwater fluxes and changes to water in storage are less well known meaning that it is difficult to perform accurate solute balances. However, if the flux of a conservative solute out of a catchment via the river system is larger than the input from rainfall (i.e., if SW*Cl(SW) > P*Cl(P)), the catchment is a net exporter of solutes. In turn this implies a change to the amount of water stored in the catchment and/or a change in chemistry of water in storage. We apply this technique to several regional-scale catchments (areas up to 15,000 km2) from Victoria, southeast Australia. Cl/Br ratios indicate that the Cl in groundwater and surface water in this region is derived from evapotranspiration of rainfall. Rivers from several catchments in Victoria are saline (Cl >500 mg/L) due mainly to groundwater inflows. Cl concentrations and EC values are well correlated allowing a long-term (up to 25 years) continual record of Cl fluxes to be estimated from sub-daily river discharge and EC data. Many of the rivers export significantly higher volumes of Cl than is delivered via rainfall (up to 1800%). Two scenarios may explain this chemical imbalance. Firstly, saline marshes and lakes developed on young (<1 Ma) basaltic lava plains have gradually drained as blocked river systems re-established. Evapotranspiration and repeated recharge-discharge cycles within these lakes and wetlands produced shallow groundwater with high Cl concentrations that is currently being exported via the re-established river systems. Secondly, in many catchments land-clearing over the last 200 years has resulted in lower evapotranspiration rates and increased recharge. The increased recharge has resulted in a rise of regional water tables and increased baseflow to the rivers. As a consequence, Cl from the groundwater that has relatively long residence time is now being exported. In both cases, the catchments are adjusting to a new hydrological balance and the Cl mass balance indicates that the present patterns of groundwater-surface water interaction are transitory. Both scenarios involve a decrease in evapotranspiration in the catchments that results in groundwater salinities decreasing. Thus, over time, the Cl concentrations in these rivers will decrease as fresher groundwater increasingly forms the baseflow to the rivers and the catchments will tend toward chemical balance; the timescale of change however may be several ka.
Effects of 500 years of eutrophication and flooding control on lowland lake development

NASA Astrophysics Data System (ADS)

Kirilova, E.; van Hardenbroek, M.; Heiri, O.; Cremer, H.; Lotter, A. F.

2009-04-01

Nutrient enrichment and the ecology of surface waters have been intensively studied in lowland regions. However, detailed palaeolimnological reconstructions of the trophic and flooding history of floodplain lakes are still rare. In the Netherlands dike-breaches caused by high floods of the river Rhine formed a new type of lake since the Middle Ages. These dike-breach lakes were strongly impacted by the development of channel systems in their catchment, agriculture, and repeated flooding events. Here we present a multiproxy palaeolimnological study of past nutrient loading and ecology of the dike-breach lake De Waay which is located on the Rhine-Meuse delta (The Netherlands). The lake was created in A.D. 1496 as a result of damage done to a dike by floating ice and the subsequent dike-breach due to a flooding event. A sediment core of 11.5 m was recovered from Lake De Waay and diatoms, Cladocera, and geochemistry were analyzed in the sediment. From the beginning of the lake's existence to the end of the 18th century diatom-inferred total phosphorus (TP) concentrations were above 300 µg/l, suggesting hypertrophic conditions. Cladoceran assemblages reflect the lake's pioneer stage and suggest a lack of rooted aquatic macrophytes resulting from low water-transparency, possibly caused by frequent floods. Until the late 18th century floods occurred regularly in the area, as shown by the elevated Ti values in the sediments, indicative of high erosion from the floodplain and runoff from the surrounding agricultural catchment. This caused the exceptionally high sedimentation rates and elevated nutrient contents of the lake waters. Since the beginning of the 19th century sewage input and flooding frequency were strongly reduced by the construction of new ditches, canals, and dikes. The improved sewage and dike systems are reflected by decreased TP concentrations of 40-150 µg/l. The increased stability of littoral habitats led to an increased diversity in the Cladocera assemblages. The phase with the lowest inferred TP concentrations lasted from the end of the 19th to the mid-20th century. During this period direct nutrient sources were no longer connected to the lake and TP concentrations consequently decreased to 40 µg/l. Dike construction was highly developed and flooding events no longer affected this region. However, a renewed eutrophication with TP values reaching 100 µg/l was registered in the sediment record since the mid-20th century. The increased TP concentrations are most likely related to increased agricultural activity in the vicinity of the lake. Our results show that Lake De Waay was eutrophic to hypertrophic during much of its history. The lake was formed as a consequence of human activity and never existed in an undisturbed state. Restoration of lakes to an "undisturbed" natural state, as required by the European Water Framework Directive, can therefore not be recommended for strongly modified lowland lakes such as De Waay.
Disentangling Holocene lake level changes with a transect of lake sediment cores - a case study from Lake Fürstenseer See, northeastern Germany

NASA Astrophysics Data System (ADS)

Dietze, Elisabeth; Slowinski, Michal; Kienel, Ulrike; Zawiska, Izabela; Brauer, Achim

2014-05-01

Deciphering the main processes contributing to lake and landscape evolution in the northern central European lowlands on different temporal scales is one of the main targets of the Virtual Institute of Integrated Climate and Landscape Evolution Analysis (ICLEA) of the Helmholtz Association. In the context of future climatic changes especially the hydrological system is a vulnerable landscape component that showed considerably large changes in the recent past. The analysis of lake sediment archives can help to infer long-term dynamics of regional lake and groundwater levels, although available proxy information needs to be studied carefully, as water level changes are only one trigger. Lake Fürstenseer See (53°19'N, 13°12'E, lake level in 2009: 63.3 m a.s.l.) formed after the retreat of the Weichselian ice sheet in a subglacial channel in the direct forefront of the Pommerian ice margin. The ~2 km2 large lake (zmax = 24.5 m) has a (sub-) surficial catchment area of ~(20) 40 km2 including other smaller lakes and peatlands. In the past, the lake system was artificially dammed for the operation of water mills. Located within the well-drained sandur substrate, the lake levels vary with groundwater levels in response to hydrological and catchment-related groundwater recharge. Detrital matter input from fluvial activity can be excluded. Lake sediment cores at four sites along a transect down to 23 m water depth show distinct sediment facies patterns. Stratigraphic descriptions and non-destructive continuous micro-XRF scanning allowed the differentiation of the main sediment facies, which were microscopically described using thin sections. Quantification of total organic and inorganic matter (TOC, TIC, C/N-composition) and discontinuous macrorest, diatom and Cladocera analysis helped to approach the sedimentation history. Stable isotopes of (delta-180, delta-13C) were used for characterization of carbonates. A high amount of non-reworked terrestrial plant remains from prominent facies shifts were dated with AMS-14C and allowed to link the different cores, assess individual sedimentation rates and to evaluate sediment focusing in the lake. Carbonatic and organic gyttjas are the main sedimentary components related mainly to authigenic production. Sometimes, carbonates show detrital mineral structures and correlations with allochthonous components (K, Ti, Si) that can only be provided by reworking of shore and slope material or in times of intense aeolian transport. Sandy facies dominate only at near-shore, steep sites and form distinct layers at the current sediment limit. A robust statistical analysis considering compositional data constraints allows an objective compilation of indications for lake level change from water depth-related habitat changes and shore erosion. They oppose detrital matter input from aeolian processes in times of anthropogenically-cleared forests. A first lake level reconstruction from the Early Holocene to recent times will be presented and linked to climatic and/or anthropogenic drivers of regional hydrological changes.
Catchment sediment flux: a lake sediment perspective on the onset of the Anthropocene?

NASA Astrophysics Data System (ADS)

Chiverrell, Richard

2014-05-01

Definitions of the Anthropocene are varied but from a geomorphological perspective broadly can be described as the interval of recent Earth history during which 'humans have had an 'overwhelming' effect on the Earth system' (Brown et al., 2013). Identifying the switch to a human-dominated geomorphic process regime is actually a challenging process, with in the 'Old World' ramping up of human populations and impacts on earth surface processes since the Neolithic/Mesolithic transition and the onset of agriculture. In the terrestrial realm lakes offer a unique window on changes in human forcing of earth surface processes from a sedimentary flux perspective, because unlike alluvial and hill-slope systems sedimentation is broadly continuous and uninterrupted. Dearing and Jones (2003) showed for a global dataset of lakes a 5-10 fold increase in sediment delivery comparing pre- and post-anthropogenic disturbance. Here sediment records from several lakes in lowland agricultural landscapes are presented to examine the changes in the flux and composition of materials delivered from their catchments. By definition the lakes record the switch to a human dominated system, but not necessary in accelerated sediment accumulation rates with changes in sediment composition equally important. Data from Crose, Hatch and Peckforton Meres, in lowland northwest England are interrogated producing quantitative land-cover reconstructions from pollen spectra calculated using the REVEALS model (Sugita, 2007), geochemical evidence for changes sediment provenance and flux, and 14C and stable Pb pollutant based chronological models detecting changes in sediment accumulation rate. The lake sediment geochemistry points to several phases of heightened human impact within these small agricultural catchments. Following small-in-scale forest cover reductions and limited impacts in terms of sediment flux during the Neolithic, the Bronze to Iron Age saw the first substantial reductions in forest cover and widespread expansions of agriculture. In some cases the catchment responses, for example here detected via dry mass Zr concentrations, were substantial and outstrip later impacts driven by more intensive agriculture e.g. early Medieval, Norman Conquest and 19th century AD. These themes are developed in relation to the concept of an Anthropocene and wider European lake sediment record. References Brown AG, Tooth S, Chiverrell RC, Rose J, Thomas DSG, Wainwright J, Bullard JE, Thorndycraft VR, Aalto R, Downs P. 2013. The Anthropocene: is there a geomorphological case? Earth Surface Processes and Landforms 38: 431-434. Dearing JA, Jones RT. 2003. Coupling temporal and spatial dimensions of global sediment flux through lake and marine sediment records. Global and Planetary Change 39: 147-168. Sugita S. 2007. Theory of quantitative reconstruction of vegetation I: pollen from large sites REVEALS regional vegetation composition. Holocene 17, 2: 229-241.
Reservoirs as hotspots of fluvial carbon cycling in peatland catchments.

PubMed

Stimson, A G; Allott, T E H; Boult, S; Evans, M G

2017-02-15

Inland water bodies are recognised as dynamic sites of carbon processing, and lakes and reservoirs draining peatland soils are particularly important, due to the potential for high carbon inputs combined with long water residence times. A carbon budget is presented here for a water supply reservoir (catchment area~9km 2 ) draining an area of heavily eroded upland peat in the South Pennines, UK. It encompasses a two year dataset and quantifies reservoir dissolved organic carbon (DOC), particulate organic carbon (POC) and aqueous carbon dioxide (CO 2 (aq)) inputs and outputs. The budget shows the reservoir to be a hotspot of fluvial carbon cycling, as with high levels of POC influx it acts as a net sink of fluvial carbon and has the potential for significant gaseous carbon export. The reservoir alternates between acting as a producer and consumer of DOC (a pattern linked to rainfall and temperature) which provides evidence for transformations between different carbon species. In particular, the budget data accompanied by 14 C (radiocarbon) analyses provide evidence that POC-DOC transformations are a key process, occurring at rates which could represent at least ~10% of the fluvial carbon sink. To enable informed catchment management further research is needed to produce carbon cycle models more applicable to these environments, and on the implications of high POC levels for DOC composition. Copyright © 2016 Elsevier B.V. All rights reserved.
The regional and global significance of nitrogen removal in lakes and reservoirs

USGS Publications Warehouse

Harrison, J.A.; Maranger, R.J.; Alexander, Richard B.; Giblin, A.E.; Jacinthe, P.-A.; Mayorga, Emilio; Seitzinger, S.P.; Sobota, D.J.; Wollheim, W.M.

2009-01-01

Human activities have greatly increased the transport of biologically available nitrogen (N) through watersheds to potentially sensitive coastal ecosystems. Lentic water bodies (lakes and reservoirs) have the potential to act as important sinks for this reactive N as it is transported across the landscape because they offer ideal conditions for N burial in sediments or permanent loss via denitrification. However, the patterns and controls on lentic N removal have not been explored in great detail at large regional to global scales. In this paper we describe, evaluate, and apply a new, spatially explicit, annual-scale, global model of lentic N removal called NiRReLa (Nitrogen Retention in Reservoirs and Lakes). The NiRReLa model incorporates small lakes and reservoirs than have been included in previous global analyses, and also allows for separate treatment and analysis of reservoirs and natural lakes. Model runs for the mid-1990s indicate that lentic systems are indeed important sinks for N and are conservatively estimated to remove 19.7 Tg N year-1 from watersheds globally. Small lakes (<50 km2) were critical in the analysis, retaining almost half (9.3 Tg N year -1) of the global total. In model runs, capacity of lakes and reservoirs to remove watershed N varied substantially at the half-degree scale (0-100%) both as a function of climate and the density of lentic systems. Although reservoirs occupy just 6% of the global lentic surface area, we estimate they retain ~33% of the total N removed by lentic systems, due to a combination of higher drainage ratios (catchment surface area:lake or reservoir surface area), higher apparent settling velocities for N, and greater average N loading rates in reservoirs than in lakes. Finally, a sensitivity analysis of NiRReLa suggests that, on-average, N removal within lentic systems will respond more strongly to changes in land use and N loading than to changes in climate at the global scale. ?? 2008 Springer Science+Business Media B.V.
Effects of land use on lake nutrients: The importance of scale, hydrologic connectivity, and region

USGS Publications Warehouse

Soranno, Patricia A.; Cheruvelil, Kendra Spence; Wagner, Tyler; Webster, Katherine E.; Bremigan, Mary Tate

2015-01-01

Catchment land uses, particularly agriculture and urban uses, have long been recognized as major drivers of nutrient concentrations in surface waters. However, few simple models have been developed that relate the amount of catchment land use to downstream freshwater nutrients. Nor are existing models applicable to large numbers of freshwaters across broad spatial extents such as regions or continents. This research aims to increase model performance by exploring three factors that affect the relationship between land use and downstream nutrients in freshwater: the spatial extent for measuring land use, hydrologic connectivity, and the regional differences in both the amount of nutrients and effects of land use on them. We quantified the effects of these three factors that relate land use to lake total phosphorus (TP) and total nitrogen (TN) in 346 north temperate lakes in 7 regions in Michigan, USA. We used a linear mixed modeling framework to examine the importance of spatial extent, lake hydrologic class, and region on models with individual lake nutrients as the response variable, and individual land use types as the predictor variables. Our modeling approach was chosen to avoid problems of multi-collinearity among predictor variables and a lack of independence of lakes within regions, both of which are common problems in broad-scale analyses of freshwaters. We found that all three factors influence land use-lake nutrient relationships. The strongest evidence was for the effect of lake hydrologic connectivity, followed by region, and finally, the spatial extent of land use measurements. Incorporating these three factors into relatively simple models of land use effects on lake nutrients should help to improve predictions and understanding of land use-lake nutrient interactions at broad scales.
Paleoecological inferences of recent alluvial damming of a lake basin due to retrogressive permafrost thaw slumping

NASA Astrophysics Data System (ADS)

Quinlan, R.; Delaney, S.; Lamoureux, S. F.; Kokelj, S. V.; Pisaric, M. F.

2014-12-01

Expected climate impacts of future warming in the Arctic include thawing of permafrost landscapes in northern latitudes. Thawing permafrost is expected to have major consequences on hydrological dynamics, which will affect the limnological conditions of Arctic lakes and ponds. In this study we obtained a sediment core from a small lake (informally named "FM1") near Fort McPherson, Northwest Territories, Canada, with a large retrogressive thaw slump (nearly 1 kilometre in diameter) within its catchment. A radiocarbon date from the base of the FM1 sediment core suggests the lake formed between 990-1160 Cal AD. The analysis of aerial photographs indicate the thaw slump initiated between 1970-1990, and sediment geochemistry analysis indicated major changes in sediment content at 54-cm sediment core depth. Analyses of subfossil midge (Chironomidae) fossils inferred that, pre-slump, lake FM1 was shallow with a large bog or wetland environment, with midge assemblages dominated by taxa such as Limnophyes and Parametriocnemus. Post-thaw midge assemblages were dominated by subfamily Chironominae (Tribe Tanytarsini and Tribe Chironomini) taxa, and the appearance of deepwater-associated taxa such as Sergentia suggests that lake FM1 deepened, possibly as a result of alluvial damming from slump materials washing into the lake near its outlet. Most recent stratigraphic intervals infer a reversion back to shallower conditions, with a slight recovery of bog or wetland-associated midge taxa, possibly due to rapid basin infilling from increased deposition rates of catchment-derived materials. Results emphasize that there may be a variety of different outcomes to Arctic lake and pond ecosystems as a result of permafrost thawing, contingent on system-specific characteristics such as slump location relative to the lake basin, and relative inflow and outflow locations within the lake basin.
Temporal Dynamics and Decay of Putatively Allochthonous and Autochthonous Viral Genotypes in Contrasting Freshwater Lakes

PubMed Central

Barbosa, Jorge G.; Brown, Julia M.; Donelan, Ryan P.; Eaglesham, James B.; Eggleston, Erin M.; LaBarre, Brenna A.

2012-01-01

Aquatic viruses play important roles in the biogeochemistry and ecology of lacustrine ecosystems; however, their composition, dynamics, and interactions with viruses of terrestrial origin are less extensively studied. We used a viral shotgun metagenomic approach to elucidate candidate autochthonous (i.e., produced within the lake) and allochthonous (i.e., washed in from other habitats) viral genotypes for a comparative study of their dynamics in lake waters. Based on shotgun metagenomes prepared from catchment soil and freshwater samples from two contrasting lakes (Cayuga Lake and Fayetteville Green Lake), we selected two putatively autochthonous viral genotypes (phycodnaviruses likely infecting algae and cyanomyoviruses likely infecting picocyanobacteria) and two putatively allochthonous viral genotypes (geminiviruses likely infecting terrestrial plants and circoviruses infecting unknown hosts but common in soil libraries) for analysis by genotype-specific quantitative PCR (TaqMan) applied to DNAs from viruses in the viral size fraction of lake plankton, i.e., 0.2 μm > virus > 0.02 μm. The abundance of autochthonous genotypes largely reflected expected host abundance, while the abundance of allochthonous genotypes corresponded with rainfall and storm events in the respective catchments, suggesting that viruses with these genotypes may have been transported to the lake in runoff. The decay rates of allochthonous and autochthonous genotypes, assessed in incubations where all potential hosts were killed, were generally lower (0.13 to 1.50% h−1) than those reported for marine virioplankton but similar to those for freshwater virioplankton. Both allochthonous and autochthonous viral genotypes were detected at higher concentrations in subsurface sediments than at the water-sediment interface. Our data indicate that putatively allochthonous viruses are present in lake plankton and sediments, where their temporal dynamics reflect active transport to the lake during hydrological events and then decay once there. PMID:22773646

Effects of Land Use on Lake Nutrients: The Importance of Scale, Hydrologic Connectivity, and Region

PubMed Central

Soranno, Patricia A.; Cheruvelil, Kendra Spence; Wagner, Tyler; Webster, Katherine E.; Bremigan, Mary Tate

2015-01-01

Catchment land uses, particularly agriculture and urban uses, have long been recognized as major drivers of nutrient concentrations in surface waters. However, few simple models have been developed that relate the amount of catchment land use to downstream freshwater nutrients. Nor are existing models applicable to large numbers of freshwaters across broad spatial extents such as regions or continents. This research aims to increase model performance by exploring three factors that affect the relationship between land use and downstream nutrients in freshwater: the spatial extent for measuring land use, hydrologic connectivity, and the regional differences in both the amount of nutrients and effects of land use on them. We quantified the effects of these three factors that relate land use to lake total phosphorus (TP) and total nitrogen (TN) in 346 north temperate lakes in 7 regions in Michigan, USA. We used a linear mixed modeling framework to examine the importance of spatial extent, lake hydrologic class, and region on models with individual lake nutrients as the response variable, and individual land use types as the predictor variables. Our modeling approach was chosen to avoid problems of multi-collinearity among predictor variables and a lack of independence of lakes within regions, both of which are common problems in broad-scale analyses of freshwaters. We found that all three factors influence land use-lake nutrient relationships. The strongest evidence was for the effect of lake hydrologic connectivity, followed by region, and finally, the spatial extent of land use measurements. Incorporating these three factors into relatively simple models of land use effects on lake nutrients should help to improve predictions and understanding of land use-lake nutrient interactions at broad scales. PMID:26267813
Provenance of tetraether membrane lipids in a large temperate lake (Loch Lomond, UK): implications for GDGT-based palaeothermometry

NASA Astrophysics Data System (ADS)

Buckles, L. K.; Weijers, J. W. H.; Tran, X.-M.; Waldron, S.; Sinninghe Damsté, J. S.

2014-03-01

The application of glycerol dialkyl glycerol tetraether (GDGT)-based palaeoenvironmental proxies, such as the BIT index, TEX86 and the MBT/CBT palaeothermometer, has lately been expanded to lacustrine sediments. Given recent research identifying the production of branched, bacterial GDGTs (brGDGTs) within lakes, it is necessary to ascertain the effect of this lacustrine production on GDGT-based proxies. This study profiles a temperate, monomictic lake (Loch Lomond, UK), analysing labile intact polar GDGT lipids (IPLs) and resilient core GDGT lipids (CLs) in catchment soils, small tributary rivers, lake water and lake sediments. Loch Lomond consists of two basins bisected by the Highland Boundary Fault, resulting in a mesotrophic to oligotrophic gradient from south to north. The north basin is fjord-like, while the south basin is shallow with a lowland catchment. Besides abundant influxes of allochthonous soil and peat-derived (CL) brGDGTs, brGDGTs are produced in a variety of settings in Loch Lomond. Rather than integrating a scattered soil signal, there is some evidence that small rivers may contribute to the brGDGT pool through addition of brGDGTs produced in situ in these streams. 300 days of settling particles and water column profiles of suspended particulate matter (SPM; March and September 2011) reveal brGDGT production throughout the water column, with (IPL and CL) brGDGT distributions varying by basin. In lake sediments, in situ brGDGT production affects the distributions of sedimentary brGDGTs despite high soil and peat-derived organic matter influxes from the catchment. MBT/CBT-derived mean annual air temperature (MAAT) estimates from soil, river and lake sediments vary widely. A strong bias towards higher MAATs in the south and lower MAATs in the north basin further complicates the application of the proxy. These results emphasise that caution must be exercised when applying the MBT/CBT palaeothermometer to individual lakes in which the use of the proxy has not been validated and therefore the factors affecting its application are not well understood. Despite elevated BIT indices, (partly) due to in situ brGDGT production, reliable TEX86 lake surface temperature (LST) estimates were obtained from SPM with BIT indices up to 0.9 but containing abundant crenarchaeol. Lower north basin sediments yielded accurate LST estimates but require further evaluation to properly constrain the application of the TEX86 proxy.
Transposing Concentration-Discharge Curves onto Unmonitored Catchments to Estimate Seasonal Nutrient Loads

NASA Astrophysics Data System (ADS)

Minaudo, C.; Moatar, F.; Abbott, B. W.; Dupas, R.; Gascuel-Odoux, C.; Pinay, G.; Roubeix, V.; Danis, P. A.

2017-12-01

Many lakes and reservoirs in Europe suffer from severe eutrophication. Accurate quantification of nutrient loads are critical for effective mitigation measures, but this information is often unknown. For example, in France, only 50 out of 481 lakes and reservoirs have national monitoring allowing estimation of interannual nitrogen and phosphorus loads, and even these loads are computed from low-frequency data. To address this lack of data, we developed a straightforward method to predict seasonal loads in lake tributaries. First, we analyzed concentration-discharge (C-Q) curves in monitored catchments and identified slopes, intercepts, and coefficient of variation of the log(C)-log(Q) regressions determined for both low and high flows, separated by the median daily flow [Moatar et al., 2017]. Then, we used stepwise multiple linear regression models to empirically link the characteristics of C-Q curves with a set of catchment descriptors such as land use, lithology, morphology indices, climate, and hydrological indicators. Modeled C-Q relationships were then used to estimate annual and seasonal nutrient loads in nearby and similar unmonitored catchments. We implemented this approach on a large dataset from France where stream flow was surveyed daily and water quality (suspended solids, nitrate, total phosphorus, and orthophosphate concentrations) was measured on a monthly basis at 233 stations over the past 20 years in catchments from 10 to 3000 km². The concentration at the median daily flow (seen here as a metric of the general level of contamination in a catchment) was predicted with uncertainty ranging between 30 and 100 %, depending on the variable. C-Q slopes were predicted with large errors, but a sensitivity analysis was conducted to determine the impact of C-Q slopes uncertainties on computed annual and seasonal loads. This approach allows estimation of seasonal and annual nutrient loads and could be potentially implemented to improve protection and restoration of aquatic ecosystems. Moatar, F., B. W. Abbott, C. Minaudo, F. Curie, and G. Pinay. 2017. Elemental properties, hydrology, and biology interact to shape concentration-discharge curves for carbon, nutrients, sediment, and major ions. Water Resources Research 53:1270-1287.
Quantitative assessment of glacial fluctuations in the level of Lake Lisan, Dead Sea rift

NASA Astrophysics Data System (ADS)

Rohling, Eelco J.

2013-06-01

A quantitative understanding of climatic variations in the Levant during the last glacial cycle is needed to support archaeologists in assessing the drivers behind hominin migrations and cultural developments in this key region at the intersection between Africa and Europe. It will also foster a better understanding of the region's natural variability as context to projections of modern climate change. Detailed documentation of variations in the level of Lake Lisan - the lake that occupied the Dead Sea rift during the last glacial cycle - provides crucial climatic information for this region. Existing reconstructions suggest that Lake Lisan highstands during cold intervals of the last glacial cycle represent relatively humid conditions in the region, but these interpretations have remained predominantly qualitative. Here, I evaluate realistic ranges of the key climatological parameters that controlled lake level, based on the observed timing and amplitudes of lake-level variability. I infer that a mean precipitation rate over the wider catchment area of about 500 mm y-1, as proposed in the literature, would be consistent with observed lake levels if there was a concomitant 15-50% increase in wind speed during cold glacial stadials. This lends quantitative support to previous inferences of a notable increase in the intensity of Mediterranean (winter) storms during glacial periods, which tracked eastward into the Levant. In contrast to highstands during ‘regular’ stadials, lake level dropped during Heinrich Events. I demonstrate that this likely indicates a further intensification of the winds during those times.
Glacial flour in lacustrine sediments: Records of alpine glaciation in the western U.S.A. during the last glacial interval

NASA Astrophysics Data System (ADS)

Rosenbaum, J. G.; Reynolds, R. L.

2010-12-01

Sediments in Bear Lake (UT/ID) and Upper Klamath Lake (OR) contain glacial flour derived during the last glacial interval from the Uinta Mountains and the southern Cascade Range, respectively. Magnetic properties provide measures of glacial-flour content and, in concert with elemental and grain-size analyses, yield high-resolution records of glacial growth and decay. Creation and preservation of such records requires that (1) properties of glacial flour contrast with those of other sedimentary components and (2) magnetic minerals are neither formed nor destroyed after deposition. In the Bear Lake watershed, glaciers were confined to a small headwater area of the Bear River underlain by hematite-rich rocks of the Uinta Mountain Group (UMG), which are not exposed elsewhere in the catchment. Because UMG detritus is abundant only in Bear Lake sediments of glacial age, hard isothermal remanent magnetization (a measure of hematite content) provides a proxy for glacial flour. In contrast, the entire Upper Klamath Lake catchment, which lies to the east of the Cascade Range in southern Oregon, is underlain largely by basalt and basaltic andesite. Magnetic properties of fresh titanomagnetite-rich rock flour from glaciers on a composite volcano contrast sharply with those of detritus from unglaciated areas in which weathering destroyed some of the titanomagnetite. Ideally, well-dated records of the flux of glacial flour can be compared to ages of glacial features (e.g., moraines). For Upper Klamath Lake, quantitative measures of rock-flour content (from magnetic properties) and excellent chronology allow accurate calculation of flux. However, ages of glacial features are lacking and mafic volcanic rocks, which weather rapidly in this environment, are not well suited for cosmogenic exposure dating. At Bear Lake, estimates of glacial-flour content are less quantitative and chronology within the glacial interval must be interpolated from radiocarbon ages above and below the glacial-age sediments, but cosmogenic dating (by Laabs et al.) of highly resistant quartzite boulders provide ages from terminal moraines in the Bear River drainage. Glacial flour appears abruptly at ~26 cal ka in Bear Lake, whereas it is present at the base of the Upper Klamath Lake core (~37 cal ka). Both glacial flour records (1) contain millennial-scale variations (uncertainties in chronology prevent precise correlation of these features), (2) attain maxima circa 19 cal ka, and (3) rapidly decline beginning prior to 18 cal ka. At Bear Lake the age of the decline in glacial flour coincides with cosmogenic exposure ages (18.1 - 18.7 ka) of terminal moraines in the upper Bear River valley. This concurrence supports the interpretation that the maximum amount and subsequent decrease in glacial flour are indicative of maximum glacial extent and glacial retreat, respectively, and more generally that increases and decreases in rock flour in these lake sediments represent waxing and waning of glaciers. Laabs, B,J.C., et al., 2007, Chronology of the last glacial maximum in the upper Bear River basin, Utah, Arctic and Alpine Research, v. 39, p. 537 - 548.
Modeling dissolved silica retention in the limnic system of North America

NASA Astrophysics Data System (ADS)

Lauerwald, R.; Jansen, N.; Hartmann, J.; Dürr, H. H.; Loos, S.; Kempe, S.; Middelkoop, H.

2009-04-01

Dissolved silica (DSi) is an important nutrient in freshwater and coastal ecosystems. The availability of DSi is governed by DSi mobilization from the terrestrial system into the limnic system and fluvial transport of DSi to the coasts, respectively. Part of the DSi is retained in the limnic system due to biotic uptake and sedimentation. Anthropogenic influences including eutrophication and construction of dams and locks can lead to an increase in DSi retention (Humborg et al., 2006), with potentially severe consequences for coastal ecosystems (Danielsson et al., 2008). It is here hypothesized that DSi retention can be calculated by subtracting DSi fluxes observed at downstream sampling locations from the amount of DSi mobilized from the terrestrial system into rivers. This strategy to estimate the DSi retention is applied to river systems located in the USA and evaluated. Hydrochemical data from the USGS programs WQN and NAWQA are used to calculate annual DSi fluxes for more than 500 sampling locations. For each water sampling location the river catchment and catchment properties (lithology, land cover, lake area etc.) are calculated. Emphasize is put on abundance and size of lakes, wetlands, and reservoirs as places of increased DSi retention. DSi mobilization into rivers is estimated applying an empirical mobilization function developed for the North American region (Jansen et al., submitted). On average, DSi fluxes from the terrestrial system into rivers are higher than observed fluvial DSi fluxes. The difference between mobilized and observed DSi fluxes increases with catchment area. Applying the introduced difference method to a subset of water sampling locations situated near the rivers' mouths (n=89), a discharge weighted average DSi retention of about 26% is calculated. Uncertainties due to the statistical methods are discussed. References Danielsson, A., Papush, L., and Rahm, L., 2008, Alterations in nutrient limitations - Scenarios of a changing Baltic Sea: Journal of Marine Systems, v. 73, p. 263-283. Humborg, C., Pastuszak, M., Aigars, J., Siegmund, H., Morth, C.M., and Ittekkot, V., 2006, Decreased silica land-sea fluxes through damming in the Baltic Sea catchment - significance of particle trapping and hydrological alterations: Biogeochemistry, v. 77, p. 265-281. Jansen, N., Lauerwald, R., Hartmann, J., Dürr, H. H., Loos, S., Kempe, S. and Middelkoop, H. ,submitted, A continental scale model for dissolved silica mobilization for North America. (submitted to this session)
IMPLICATION OF LAKE WATER RESIDENCE TIME ON THE CLASSIFICATION OF NORWEGIAN SURFACE WATER SITES INTO PROGRESSIVE STAGES OF NITROGEN SATURATION

EPA Science Inventory

Seasonal behaviour of NO3- in surface water is often used as an indicator on a catchment's ability to retain N from atmospheric deposition. In this paper, we classify 12 pristine sites (five streams and seven lakes) in southernmost Norway according to the N saturation stage conce...
Regime Shifts in Shallow Lakes: Responses of Cyanobacterial Blooms to Watershed Agricultural Phosphorus Loading Over the Last ~100 Years.

NASA Astrophysics Data System (ADS)

Vermaire, J. C.; Taranu, Z. E.; MacDonald, G. K.; Velghe, K.; Bennett, E.; Gregory-Eaves, I.

2015-12-01

Rapid changes in ecosystem states have occurred naturally throughout Earth's history. However, environmental changes that have taken place since the start of the Anthropocene may be destabilizing ecosystems and increasing the frequency of regime shifts in response to abrupt changes in external drivers or local intrinsic dynamics. To evaluate the relative influence of these forcers and improve our understanding of the impact of future change, we examined the effects of historical catchment phosphorus loading associated with agricultural land use on lake ecosystems, and whether this caused a shift from a stable, clear-water, regime to a turbid, cyanobacteria-dominated, state. The sedimentary pigments, diatom, and zooplankton (Cladocera) records from a currently clear-water shallow lake (Roxton Pond) and a turbid-water shallow lake (Petit lac Saint-François; PSF) were examined to determine if a cyanobacteria associated pigment (i.e. echinenone) showed an abrupt non-linear response to continued historical phosphorus load index (determined by phosphorus budget) over the last ~100 years. While PSF lake is presently in the turbid-water state, pigment and diatom analyses indicated that both lakes were once in the clear-water state, and that non-linear increases in catchment phosphorus balance resulted in an abrupt transition to cyanobacteria dominated states in each record. These results show that phosphorus loading has resulted in state shifts in shallow lake ecosystems that has been recorded across multiple paleolimnological indicators preserved in the sedimentary record.
Ecosystem Disturbances in Central European Spruce Forests: a Multi-proxy Integration of Dendroecology and Sedimentary Records

NASA Astrophysics Data System (ADS)

Clear, J.; Chiverrell, R. C.; Kunes, P.; Boyle, J.; Kuosmanen, N.; Carter, V.

2016-12-01

The montane Norway spruce (Picea abies) dominated forests of Central Europe are a niche environment; situated outside their natural boreal distribution they are vulnerable to both short term disturbances (e.g. floods, avalanches, fire, windstorm and pathogens) and longer-term environmental change (e.g. climate induced stress, snow regimes). Holocene sediment records from lakes in the High Tatra (Slovakia) and Bohemian (Czech) Mountains show repeated disturbances of the pristine Picea abies-dominated forests as sharp well defined minerogenic in-wash horizons that punctuate the accumulation of organic gyttja. These event horizons span a process continuum from lakes with restricted catchments and limited inflow (e.g. Prazilske Lake, Czech) to more catchment-process dominated lakes with large catchments (e.g. Popradske Lake, Slovakia). The events include complex responses to a global climatic downturn at 8.2ka, other cooler episodes 3.5, 1.6 and 0.5 ka, and to recent discrete wind-storms and pathogen outbreaks. We develop a typology for disturbance events using sediment geochemistry, particle size, mineral magnetism, charcoal and palaeoecology to assess likely drivers of disturbance. For the recent past integrating data from dendroecology and sediments is used to calibrate our longer-term perspective on forest dynamics. Tree-ring series from plots or forest stands are used alongside lake and forest hollow sediments to explore the local, regional and biogeographical scale of forest disturbances. Dendroecological data showing tree-ring gap recruitment and post-suppression growth release highlight frequent disturbance events focused on tree or forest stand spatial scales, but are patchy in terms of their reoccurrence. However they highlight levels of disturbance in the late 19th Century and parallel lake and forest hollow sediments record variable pollen influx (beetle host / non-host ratios) and stratigraphies that include mineral in-wash events. The identified recent and ongoing forest disturbances coupled with well-evidenced events in the 19th century highlight the need for the longer sedimentary perspective to assess whether contemporary climate warming has and continues to stretch the resilience of these fragile ecosystems.
Do changes in climate and land use pose a risk to the future water availability of Mediterranean Lakes?

NASA Astrophysics Data System (ADS)

Bucak, T.; Trolle, D.; Andersen, H. E.; Thodsen, H.; Erdoğan, Ş.; Levi, E. E.; Filiz, N.; Jeppesen, E.; Beklioğlu, M.

2016-12-01

Inter- and intra-annual water level fluctuations and change in water flow regime are intrinsic characteristics of Mediterranean lakes. However, considering the climate change projections for the water-limited Mediterranean region where potential evapotranspiration exceeds precipitation and with increased air temperatures and decreased precipitation, more dramatic water level declines in lakes and severe water scarcity problems are expected to occur in the future. Our study lake, Lake Beyşehir, the largest freshwater lake in the Mediterranean basin, is - like other Mediterranean lakes - under pressure due to water abstraction for irrigated crop farming and climatic changes, and integrated water level management is therefore required. We used an integrated modeling approach to predict the future lake water level of Lake Beyşehir in response to the future changes in both climate and, potentially, land use by linking the catchment model Soil and Water Assessment Tool (SWAT) with a Support Vector Machine Regression model (ɛ-SVR). We found that climate change projections caused enhanced potential evapotranspiration and reduced total runoff, whereas the effects of various land use scenarios within the catchment were comparatively minor. In all climate scenarios applied in the ɛ-SVR model, changes in hydrological processes caused a water level reduction, predicting that the lake may dry out already in the 2040s with the current outflow regulation considering the most pessimistic scenario. Based on model runs with optimum outflow management, a 9-60% reduction in outflow withdrawal is needed to prevent the lake from drying out by the end of this century. Our results indicate that shallow Mediterranean lakes may face a severe risk of drying out and loss of ecosystem value in near future if the current intense water abstraction is maintained. Therefore, we conclude that outflow management in water-limited regions in a warmer and drier future and sustainable use of water sources are vitally important to sustain lake ecosystems and their ecosystem services.
Restoration of Bhoj Wetlands At Bhopal, India

NASA Astrophysics Data System (ADS)

Shukla, S. S.; Kulshrestha, M.; Wetland Project, Bhoj

Bhoj Wetlands comprise the two lakes at Bhopal, India. These wetlands are listed amongst the 21 lakes recognized by Ministry of Environment and Forest, India and are under consideration for Ramsar lake status. The twin lakes have a total water- spread area of 32.29 sq. kms and catchment area of 370.6 sq. kms and both lakes support a rich and diverse range of flora and fauna. Currently with the help of 7055-m Yen soft loan from Japan Bank for International Cooperation (JBIC), a comprehen- sive project called the Bhoj Wetland Project has been launched for Eco-conservation management of twin lakes and this is one of the most reputed projects of its kind being undertaken in India. This paper presents details of the various works being undertaken for restoration of these wetlands at Bhopal. The Bhoj Wetlands are located at Bhopal, a city founded in 11th century AD by King Bhoj and which became known for the worst industrial Gas tragedy in 1984 when thousands lost their lives. The city is still recovering and the Bhoj Wetland Project is playing a very crucial role in improving the overall environmental status of the City. These wetlands are at present facing acute en- vironmental degradation due to pollution from a number of sources such as inflow of untreated sewage and solid waste, silt erosion and inflow from catchment, commercial activities like washing of clothes and cleaning of vehicles etc., inflow of agricultural residues and pesticides, and encroachment by builders all of which are fast eroding the rich eco-culture, flora fauna in and around the wetlands. The Bhoj Wetland Project is being implemented since the year 1995 and is scheduled to end in March 2002. The project works are being undertaken under the overall aegis of Ministry of Housing Environment, Govt. of Madhya Pradesh (M.P.) State, India. All the detailed project reports (DPRs) and preliminary ground work was undertaken by the in-house staff of Bhoj Wetland project, resulting in huge amounts of financial savings as well as devel- opment of in-house expertise. The works have also been taken up manually as far as possible, giving employment opportunities to thousands of poor residents of Bhopal City and nearby villages. This also has ensured participation of masses by default. The project had at the time of its inception envisaged a sum of Rs. 2470 millions. As a result of manual pursuance of work, development of in-house expertise and due to various other cost reduction exercises adopted by the project authorities and engineers the project has so far spent only Rs. 1100 millions thus resulting in huge savings. A part of savings (Rs. 500 millions) has been invested to form a Lake Conservation Authority U a Government body which will look after all the lakes in the entire state 1 of Madhya Pradesh, thus contributing immensely to the cause of lake conservation. One of the special features of this project has been the involvement of masses in its various developmental schemes. This has been ensured by involving more than 55 NGOs and dozens of local educational institutions. Millions of Rupees have been ear- marked for ensuring public participation in various sub-projects. The project on its completion within the next 4 months will contribute immensely to the conservation of both the lakes which can them become role models for other similar wetlands. The paper also details out the various project works like diversion and treatment of nearly 56 MLD of sewage, reduction of harmful inflows of chemicals from activities such as washing activity, idol immersions etc., reduction measures for silt inflow to the lakes, desilting and dredging operations to increase the lake capacity by more than 2.5 M.Cum, improvement in the water quality by reduction of pollution, deweeding oper- ations, nutrient removal by dredging, increased aquaculture activities etc., large scale afforestation (1.6 million trees have been planted in the catchment) and implementa- tion of solid waste management plan in the city. The direct beneficiaries of this project would be the common people who are set to gain by virtue of improved city environ- ment, increased forest produce, controlled fishing, eco-tourism and improvement in the quality of drinking water. 2
Subcatchment deltas and upland features influence multiscale aquatic ecosystem recovery in damaged landscapes.

PubMed

Kielstra, Brian W; Arnott, Shelley E; Gunn, John M

2017-12-01

Assessing biological recovery in damaged aquatic environments requires the consideration of multiple spatial and temporal scales. Past research has focused on assessing lake recovery from atmospheric or catchment disturbance at regional or catchment levels. Studies have also rarely considered the influences of adjacent terrestrial characteristics on within-lake habitats, such as subcatchment delta confluences. We used Hyalella azteca, a ubiquitous freshwater amphipod, as a sensitive indicator to assess the importance of local subcatchment scale factors in the context of multiscale lake recovery within the metal mining region of Sudbury, Canada following a period of major reductions in atmospheric pollution. At the regional scale, data from repeated surveys of 40 lakes showed higher probabilities of H. azteca occurrence with higher lake water conductivity, alkalinity, and pH and lower metal concentrations. The importance of metals decreased through time and the importance of higher conductivity, alkalinity, and pH increased. At the subcatchment scale, a subset of six lakes sampled across a colonization gradient revealed higher H. azteca abundances at subcatchment delta sites than non-delta sites in early colonization stages, and that abundance at delta sites was correlated with both within-lake habitat and terrestrial subcatchment characteristics. For example, wetland cover reduced the strength of positive associations between H. azteca abundance and macrophyte density. A single lake from this subset also revealed higher abundances at delta sites associated with higher concentrations of terrestrial organic matter and larger subcatchments. Our results demonstrate that factors affecting recovery can change with the scale of study, and that managing terrestrial-aquatic linkages is important for facilitating recovery processes within damaged lake ecosystems. © 2017 by the Ecological Society of America.
From Air Temperature to Lake Evaporation on a Daily Time Step: A New Empirical Approach

NASA Astrophysics Data System (ADS)

Welch, C.; Holmes, T. L.; Stadnyk, T. A.

2016-12-01

Lake evaporation is a key component of the water balance in much of Canada due to the vast surface area covered by open water. Hence, incorporating this flux effectively into hydrological simulation frameworks is essential to effective water management. Inclusion has historically been limited by the intensive data required to apply the energy budget methods previously demonstrated to most effectively capture the timing and volume of the evaporative flux. Widespread, consistent, lake water temperature and net radiation data are not available across much of Canada, particularly the sparsely populated boreal shield. We present a method to estimate lake evaporation on a daily time step that consists of a series of empirical equations applicable to lakes of widely varying morphologies. Specifically, estimation methods that require the single meteorological variable of air temperature are presented for lake water temperature, net radiation, and heat flux. The methods were developed using measured data collected at two small Boreal shield lakes, Lake Winnipeg North and South basins, and Lake Superior in 2008 and 2009. The mean average error (MAE) of the lake water temperature estimates is generally 1.5°C, and the MAE of the heat flux method is 50 W m-2. The simulated values are combined to estimate daily lake evaporation using the Priestley-Taylor method. Heat storage within the lake is tracked and limits the potential heat flux from a lake. Five-day running averages compare well to measured evaporation at the two small shield lakes (Bowen Ratio Energy Balance) and adequately to Lake Superior (eddy covariance). In addition to air temperature, the method requires a mean depth for each lake. The method demonstrably improves the timing and volume of evaporative flux in comparison to existing evaporation methods that depend only on temperature. The method will be further tested in a semi-distributed hydrological model to assess the cumulative effects across a lake-dominated catchment in the Lower Nelson River basin.
Inter- and Intra- Field variations in soil compaction levels and subsequent impacts on hydrological extremes

NASA Astrophysics Data System (ADS)

Pattison, Ian; Coates, Victoria

2015-04-01

The rural landscape in the UK is dominated by pastoral agriculture, with about 40% of land cover classified as either improved or semi-natural grassland according to the Land Cover Map 2007. Intensification has resulted in greater levels of compaction associated with higher stocking densities. However, there is likely to be a great amount of variability in compaction levels within and between fields due to multiple controlling factors. This research focusses in on two of these factors; firstly animal species, namely sheep, cattle and horses; and secondly field zonation e.g. feeding areas, field gates, open field. Field experiments have been conducted in multiple fields in the River Skell catchment, in Yorkshire, UK, which has an area of 140km2. The effect on physical and hydrologic soil characteristics such as bulk density and moisture contents have been quantified using a wide range of field and laboratory based experiments. Results have highlighted statistically different properties between heavily compacted areas where animals congregate and less-trampled open areas. Furthermore, soil compaction has been hypothesised to contribute to increased flood risk at larger spatial scales. Previous research (Pattison, 2011) on a ~40km2 catchment (Dacre Beck, Lake District, UK) has shown that when soil characteristics are homogeneously parameterised in a hydrological model, downstream peak discharges can be 65% higher for a heavy compacted soil than for a lightly compacted soil. Here we report results from spatially distributed hydrological modelling using soil parameters gained from the field experimentation. Results highlight the importance of both the percentage of the catchment which is heavily compacted and also the spatial distribution of these fields.
Modeled Sources, Transport, and Accumulation of Dissolved Solids in Water Resources of the Southwestern United States

USGS Publications Warehouse

Anning, D.W.

2011-01-01

Information on important source areas for dissolved solids in streams of the southwestern United States, the relative share of deliveries of dissolved solids to streams from natural and human sources, and the potential for salt accumulation in soil or groundwater was developed using a SPAtially Referenced Regressions On Watershed attributes model. Predicted area-normalized reach-catchment delivery rates of dissolved solids to streams ranged from <10(kg/year)/km2 for catchments with little or no natural or human-related solute sources in them to 563,000(kg/year)/km2 for catchments that were almost entirely cultivated land. For the region as a whole, geologic units contributed 44% of the dissolved-solids deliveries to streams and the remaining 56% of the deliveries came from the release of solutes through irrigation of cultivated and pasture lands, which comprise only 2.5% of the land area. Dissolved-solids accumulation is manifested as precipitated salts in the soil or underlying sediments, and (or) dissolved salts in soil-pore or sediment-pore water, or groundwater, and therefore represents a potential for aquifer contamination. Accumulation rates were <10,000(kg/year)/km2 for many hydrologic accounting units (large river basins), but were more than 40,000(kg/year)/km2 for the Middle Gila, Lower Gila-Agua Fria, Lower Gila, Lower Bear, Great Salt Lake accounting units, and 247,000(kg/year)/km2 for the Salton Sea accounting unit. ?? 2011 American Water Resources Association. This article is a U.S. Government work and is in the public domain in the USA.
Nitrogen saturation in the Rocky Mountains

Treesearch

Mark W. Williams; Jill S. Baron; Nel Caine; Richard Sommerfeld; Robert Sanford

1996-01-01

Nitrogen saturation is occurring throughout high-elevation catchments of the Colorado Front Range. Annual inorganic N loading in wet deposition to the Front Range of ~4 kg ha-1 yr-1 is about twice that of the Pacific States and similar to many sites in the northeastern United States. In the last ten years at Niwot Ridge/Green Lakes Valley and Glacier Lakes, annual...
Hydrological and depositional processes associated with recent glacier recession in Yanamarey catchment, Cordillera Blanca (Peru).

PubMed

López-Moreno, J I; Valero-Garcés, B; Mark, B; Condom, T; Revuelto, J; Azorín-Molina, C; Bazo, J; Frugone, M; Vicente-Serrano, S M; Alejo-Cochachin, J

2017-02-01

In this study, we investigate changes in the glaciated surface and the formation of lakes in the headwater of the Querococha watershed in Cordillera Blanca (Peru) using 24 Landsat images from 1975 to 2014. Information of glacier retreat was integrated with available climate data, the first survey of recent depositional dynamics in proglacial Yanamarey Lake (4600m a.s.l.), and a relatively short hydrological record (2002-2014) at the outlet of Yanamarey Lake. A statistically significant temperature warming (0.21°C decade -1 for mean annual temperature) has been detected in the region, and it caused a reduction of the glacierized area since 1975 from 3.5 to 1.4km -2 . New small lakes formed in the deglaciated areas, increasing the flooded area from1.8ha in 1976 to 2.8ha in 2014. A positive correlation between annual rates of glacier recession and runoff was found. Sediment cores revealed a high sedimentation rate (>1cmyr -1 ) and two contrasted facies, suggesting a shift toward a reduction of meltwater inputs and higher hydrological variability likely due to an increasing role of precipitation on runoff during the last decades. Despite the age control uncertainties, the main transition likely occurred around 1998-2000, correlating with the end of the phase with maximum warming rates and glacier retreat during the 1980s and 1990s, and the slowing down of expansion of surface lake-covered surface. With this hydrological - paleolimnological approach we have documented the association between recent climate variability and glacier recession and the rapid transfer of hydroclimate signal to depositional and geochemical processes in high elevation Andean environments. This, study also alerts about water quality risks as proglacial lakes act as secondary reservoirs that trap trace and minor elements in high altitude basins. Copyright © 2016 Elsevier B.V. All rights reserved.
Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.

PubMed

Kelly, Erin N; Schindler, David W; St Louis, Vincent L; Donald, David B; Vladicka, Katherine E

2006-12-19

Recent findings indicate that fishes from lakes in partially burned catchments contain greater mercury (Hg) concentrations than fishes from reference catchments. Increased methyl Hg (MeHg) concentrations in fishes can result in serious health problems for consumers. Here we show that a forest fire caused a 5-fold increase in whole-body Hg accumulation by rainbow trout (Oncorhynchus mykiss) and smaller Hg increases in muscle of several fish species in a mountain lake. The enhanced Hg accumulation was caused primarily by increased nutrient concentrations in the lake, which enhanced productivity and restructured the food web through increased piscivory and consumption of Mysis. This restructuring resulted in increases to the trophic positions and Hg concentrations of fishes. Forest fire also caused a large short-term release of total Hg (THg) and MeHg to streams and the lake. This release initiated a small pulse of MeHg in invertebrates that contributed to enhanced Hg accumulation by fishes. Climate change and prescribed burning to compensate for past fire suppression are predicted to increase future forest fire occurrence in North America, and increased Hg accumulation by fishes may be an unexpected consequence.
Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs

PubMed Central

Kelly, Erin N.; Schindler, David W.; St. Louis, Vincent L.; Donald, David B.; Vladicka, Katherine E.

2006-01-01

Recent findings indicate that fishes from lakes in partially burned catchments contain greater mercury (Hg) concentrations than fishes from reference catchments. Increased methyl Hg (MeHg) concentrations in fishes can result in serious health problems for consumers. Here we show that a forest fire caused a 5-fold increase in whole-body Hg accumulation by rainbow trout (Oncorhynchus mykiss) and smaller Hg increases in muscle of several fish species in a mountain lake. The enhanced Hg accumulation was caused primarily by increased nutrient concentrations in the lake, which enhanced productivity and restructured the food web through increased piscivory and consumption of Mysis. This restructuring resulted in increases to the trophic positions and Hg concentrations of fishes. Forest fire also caused a large short-term release of total Hg (THg) and MeHg to streams and the lake. This release initiated a small pulse of MeHg in invertebrates that contributed to enhanced Hg accumulation by fishes. Climate change and prescribed burning to compensate for past fire suppression are predicted to increase future forest fire occurrence in North America, and increased Hg accumulation by fishes may be an unexpected consequence. PMID:17158215
The pre-spawning migratory behaviour of Atlantic salmon Salmo salar in a large lacustrine catchment.

PubMed

Kennedy, R J; Allen, M

2016-09-01

The movements of adult Atlantic salmon Salmo salar were determined as they migrated to spawning habitats in a large lacustrine catchment, Lough Neagh, in Northern Ireland. The minimum average ground speed of S. salar through the lake was 2·1 km day(-1) and the mean residence time was 11 days. Tagged S. salar tended to actively migrate through the lake which represented a transitory habitat for adult S. salar. Migration time from the release site, through the lake, to a spawning tributary decreased during the migratory period. During the 4 year study period between 20·5 and 41·6% of tagged S. salar which entered the lake each year, explored at least one other channel before ascending the final spawning tributary. Exploratory behaviour was more likely in S. salar which spawned in the tributaries furthest from the sea. Exploratory behaviour was also more likely to occur during periods of reduced discharge in the natal stream. The fishery management implications of complex pre-spawning behaviour in a mixed stock lacustrine system, are discussed. © 2016 The Fisheries Society of the British Isles.

Effects of warming on groundwater flow in mountainous snowmelt-dominated catchments

NASA Astrophysics Data System (ADS)

Evans, S. G.; Ge, S.; Molotch, N. P.

2015-12-01

In mountainous regions, warmer air temperatures have led to an earlier onset of spring snowmelt and lower snowmelt rates; i.e. because snowmelt has shifted earlier when energy availability is lower. These changes to snowmelt will likely affect the partitioning of snowmelt water between surface runoff and groundwater flow, and therefore, the lag time between snowmelt and streamflow. While the connection between snowmelt and surface runoff has been well-studied, the impact of snowmelt variability on groundwater flow processes has received limited attention, especially in mountainous catchments. We construct a two-dimensional, finite element, coupled flow and heat transport hydrogeologic model to evaluate how changes in snowmelt onset and rate may alter groundwater discharge to streams in mountainous catchments. The coupled hydrogeologic model simulates seasonally frozen ground by incorporating permeability variation as a function of temperature and allows for modeling of pore water freeze and thaw. We apply the model to the Green Lakes Valley (GLV) watershed in the Rocky Mountains of Colorado, a representative snowmelt-dominated catchment. Snowmelt for the GLV catchment is reconstructed from a 12 year (1996-2007) dataset of hydrometeorological records and satellite-derived snow covered area. Modeling results suggest that on a yearly cycle, groundwater infiltration and discharge is limited by the seasonally frozen subsurface. Under average conditions from 1996 to 2007, maximum groundwater discharge to the surface lags maximum snowmelt by approximately two months. Ongoing modeling is exploring how increasing air temperatures affect lag times between snowmelt and groundwater discharge to streams. This study has implications for water resource availability and its temporal variability in a warming global climate.
Tackling soil degradation and environmental changes in Lake Manyara Basin, Tanzania to support sustainable landscape/ecosystem management.

NASA Astrophysics Data System (ADS)

Munishi, Linus; Mtei, Kelvin; Bode, Samuel; Dume, Bayu; Navas, Ana; Nebiyu, Amsalu; Semmens, Brice; Smith, Hugh; Stock, Brian; Boeckx, Pascal; Blake, Will

2017-04-01

The Lake Manyara Basin (LMB), which encompasses Lake Manyara National Park a world ranking World Biosphere Reserve, is of great ecological and socio-economic value because it hosts a small-holder rain fed and extensive irrigation agriculture, grazing grounds for pastoralists, terrestrial and aquatic habitat for wildlife and tourism business contributing to poverty alleviation. Despite these multiple ecosystem services that support the local communities, the LMB is threatened by; (a) siltation from eroded soil fed from the wider catchment and rift escarpment of the basin and (b) declining water levels due to water capture by agriculture and possibly climate change. These threats to the ecosystem and its services are augmented by increasing human population, pollution by agricultural pesticides, poaching, human encroachment and infrastructure development, and illegal fisheries. Despite these challenges, here is a dearth of information on erosion hotspots and to date soil erosion and siltation problems in LMB have been interpreted largely in qualitative terms, and no coherent interpretative framework of these records exists. Despite concerns that modern sediment fluxes to the Lake may exceed long-term fluxes, little is known about erosion sources, how erosion rates and processes vary across the landscape and how erosion rates are influenced by the strong climate gradients in the basin. This contribution describes a soil erosion and sediment management project that aims to deliver a demonstration dataset generated from inter-disciplinary sediment-source tracing technologies and approaches to assess erosion hotspots, processes and spatial patterns of erosion in the area. The work focuses on a sub basin, the Monduli Sub catchment, located within the greater LMB. This is part of efforts to establish an understanding of soil erosion and landscape degradation in the basin as a pathway for generating and developing knowledge, building capacity to assist conservationists, farmers and pastoralists, agro-entrepreneurs, and their support agents to address the problems while feeding the information into the national development policies in Tanzania and the entire East African region.
A multi-proxy approach to understanding complex responses of salt-lake catchments to climate variability and human pressure: A Late Quaternary case study from south-eastern, Spain

NASA Astrophysics Data System (ADS)

Jones, Samantha Elsie; Burjachs, Francesc; Ferrer-García, Carlos; Giralt, Santiago; Schulte, Lothar; Fernández-López de Pablo, Javier

2018-03-01

This article focuses on a former salt lake in the upper Vinalopó Valley in south-eastern Spain. The study spans the Late Pleistocene through to the Late Holocene, although with particular focus on the period between 11 ka cal BP and 3000 ka cal BP (which spans the Mesolithic and part of the Bronze Age). High resolution multi-proxy analysis (including pollen, non pollen palynomorphs, grain size, X-ray fluorescence and X-ray diffraction) was undertaken on the lake sediments. The results show strong sensitivity to both long term and small changes in the evaporation/precipitation ratio, affecting the surrounding vegetation composition, lake-biota and sediment geochemistry. To summarise the key findings the main general trends identified include: 1) Hyper-saline conditions and low lake levels at the end of the Late Glacial 2) Increasing wetness and temperatures which witnessed an expansion of mesophilic woodland taxa, lake infilling and the establishment of a more perennial lake system at the onset of the Holocene 3) An increase in solar insolation after 9 ka cal BP which saw the re-establishment of pine forests 4) A continued trend towards increasing dryness (climatic optimum) at 7 ka cal BP but with continued freshwater input 5) An increase in sclerophyllous open woody vegetation (anthropogenic?), and increasing wetness (climatic?) is represented in the lake record between 5.9 and 3 ka cal BP 6) The Holocene was also punctuated by several aridity pulses, the most prominent corresponding to the 8.2 ka cal BP event. These events, despite a paucity of well dated archaeological sites in the surrounding area, likely altered the carrying capacity of this area both regionally and locally, particularly during the Mesolithic-Neolithic transition, in terms of fresh water supply for human/animal consumption, wild plant food reserves and suitable land for crop growth.
Variations in sedimentological properties in Lake Challa, East Africa: Understanding the source to sink processes

NASA Astrophysics Data System (ADS)

Meyer, Inka; Eloy, Jonas; Verschuren, Dirk; De Batist, Marc

2016-04-01

The clastic mineral fraction of lacustrine sediments has been proven to provide valuable information about sedimentation dynamics within a lake, and it can be used to define distinct terrestrial source areas and transport mechanisms from source to sink. Down-core variation in the properties of the clastic mineral fraction yields indications for changes in terrestrial sediment sources over time. However, in order to use terrestrial proxies in palaeo-environmental reconstruction, we have to understand and quantify the modern conditions of sediment provenance and deposition at the study site. In this study we present data on grain-size distribution, mineralogy and particle shape of the clastic mineral component of lacustrine sediments from Lake Challa, a small freshwater lake of volcanic origin, located on the eastern slope of Mt. Kilimanjaro. Situated close to the equator, it contains a uniquely long and continuous sediment sequence allowing the study of inter-hemispheric climate dynamics. The finely laminated profundal sediments of Lake Challa are characterized by a fine-grained texture and are mainly composed of organic matter, biogenic silica and authigenic carbonate, with a relatively minor component of detrital mineral that can either originate from erosion of the steep volcanic crater walls or was mobilized by wind from unvegetated areas of the surrounding scrub savannah landscape. In order to distinguish between these two sources of terrestrial sediment input (i.e., local run-off versus distant aeolian) into Lake Challa, and to map out differences in sediment properties, samples were investigated from profundal surface sediments and short cores, as well as on-shore soils from several locations around the lake and from beyond the crater catchment. Variation in grain-size distribution and mineralogy can be linked to distinct terrestrial sources, whereas the shape of single particles gives additional information about transport dynamics. In future, the results from this study will be applied to the down-core record of Lake Challa to reconstruct climate-driven changes in terrigenous sediment input over time.
Huguangyan Maar Lake (SE China): A solid record of atmospheric mercury pollution history in a non-remote region

NASA Astrophysics Data System (ADS)

Zeng, Yan; Chen, Jingan; Yang, Yongqiong; Wang, Jianxu; Zhu, Zhengjie; Li, Jian

2017-10-01

Mercury is a highly toxic metal that can cause harm to environment and human health. As atmospheric deposition is the main source of total Hg input to aquatic system in remote and pristine regions, almost all the studies on atmospheric Hg pollution history concentrated in these areas, while the studies in non-remote areas are much limited, especially for the long history records. In this study, Huguangyan Maar Lake, an undisturbed lake system at low altitude in China, was selected to reconstruct the atmospheric mercury pollution history. Variation patterns of TOC, Hg and non-residual Sr in the sediment core indicated that, compared to the direct atmospheric Hg deposition, the effect of either Hg scavenging from water column by algae or the catchment inputs of previously deposited Hg on the Hg accumulation in the lake sediment was limited. The sediment Hg content in Huguangyan Lake was mainly controlled by the atmospheric Hg deposition, and thus accurately reflected the atmospheric Hg pollution history. The Hga (Hg content from atmospheric deposition) in Huguangyan Lake presented a comparable variation pattern to that in remote sites. It had the same variation trend as the global atmospheric Hg before 1950 CE, which could be attributed to the Industrial Revolution. After that, it was mainly controlled by Hg emissions from Asian countries. The variation of Hga also indicated that atmospheric Hg deposition accelerated significantly since 2000 CE. This study, along with other investigations in remote sites in China, showed that the sediment Hg in Huguangyan Lake responded to the atmospheric Hg pollution more sensitively than in the alpine regions. It should be noted that, the more intensive acceleration of Hg deposition in Huguangyan Lake may imply that the South of China suffered from much more serious atmospheric Hg pollution than previous studies revealed.
Identifying the impacts of land use on water and nutrient cycling in the South-West Mau, Kenya

NASA Astrophysics Data System (ADS)

Jacobs, Suzanne; Weeser, Björn; Breuer, Lutz; Butterbach-Bahl, Klaus; Rufino, Mariana

2016-04-01

The Mau Forest is the largest closed canopy forest system and indigenous montane forest in Kenya, covering approximately 400,000 ha. It is the source of twelve major rivers in the Rift Valley and Western Kenya and one of Kenya's five 'water towers' that provide around 10 million people with fresh water. Significant areas have been affected by deforestation and land use changes in the past decades, resulting in a loss of approx. 25% of the forest area. Recent changes in downstream water supply are discussed to be attributed to land use change, though compelling scientific evidence is still lacking. The study area is located in the South-West Mau as a part of the Sondu River basin that drains into Lake Victoria. This area has suffered a forest loss of 25% through conversion of natural forest to smallholder agriculture and tea/tree plantations. A nested catchment approach has been applied, whereby automatic measurement equipment for monitoring discharge, turbidity, nitrate, total and dissolved organic carbon, electrical conductivity and water temperature at a 10 minute interval has been set up at the outlets of three sub-catchments of 27 - 36 km² and the outlet of the 1023 km² major catchment. The dominant land use in the sub-catchments is either natural forest, tea/tree plantation or smallholder agriculture. The river data is complemented by six precipitation gauging stations and three climate stations, that all measure at the same interval. Installed during October 2014, the systems have collected high resolution data for one and a half year now. The high resolution dataset is being analysed for patterns in stream flow and water quality during dry and wet seasons as well as diurnal cycling of nitrate. The results of the different sub-catchments are compared to identify the role of land use in water and nutrient cycling. First results of the high temporal resolution data already indicate that the different types of land use affect the stream nitrate concentration. In addition to that the high resolution allows to investigate diurnal patterns, showing a shift in nitrate concentrations between wet and dry seasons. Additional spatial stream water snapshot sampling campaigns within the major catchment, as well as sampling for End Member Mixing Analysis (EMMA) and analysis of stable isotopes of precipitation, throughfall, stream water and soil and ground water is ongoing and will provide further information to increase our understanding of hydrological and biogeochemical processes and how these are affected by land use in the Mau Forest. We will report results from six snapshot sampling campaigns that depict the impact of tea/tree plantations on nitrate concentrations and an influence of land use on catchment specific discharge.
Shifts in the Source and Composition of Dissolved Organic Matter in Southwest Greenland Lakes Along a Regional Hydro-climatic Gradient

NASA Astrophysics Data System (ADS)

Osburn, Christopher L.; Anderson, Nicholas J.; Stedmon, Colin A.; Giles, Madeline E.; Whiteford, Erika J.; McGenity, Terry J.; Dumbrell, Alex J.; Underwood, Graham J. C.

2017-12-01

Dissolved organic matter (DOM) concentration and quality were examined from Arctic lakes located in three clusters across south-west (SW) Greenland, covering the regional climatic gradient: cool, wet coastal zone; dry inland interior; and cool, dry ice-marginal areas. We hypothesized that differences in mean annual precipitation between sites would result in a reduced hydrological connectivity between lakes and their catchments and that this concentrates degraded DOM. The DOM in the inland lake group was characterized by a lower aromaticity and molecular weight, a low soil-like fluorescence, and carbon stable isotope (δ13C-DOC) values enriched by 2‰ relative to the coastal group. DOC-specific absorbance (SUVA254) and DOC-specific soil-like fluorescence (SUVFC1) revealed seasonal and climatic gradients across which DOM exhibited a dynamic we term "pulse-process": Pulses of DOM exported from soils to lakes during snow and ice melt were followed by pulses of autochthonous DOM inputs (possibly from macrophytes), and their subsequent photochemical and microbial processing. These effects regulated the dynamics of DOM in the inland lakes and suggested that if circumpolar lakes currently situated in cool wetter climatic regimes with strong hydrological connectivity have reduced connectivity under a drier future climate, they may evolve toward an end-point of large stocks of highly degraded DOC, equivalent to the inland lakes in the present study. The regional climatic gradient across SW Greenland and its influence on DOM properties in these lakes provide a model of possible future changes to lake C cycling in high-latitude systems where climatic changes are most pronounced.
Contrasting temporal trends and relationships of total organic carbon, black carbon, and polycyclic aromatic hydrocarbons in rural low-altitude and remote high-altitude lakes.

PubMed

Bogdal, Christian; Bucheli, Thomas D; Agarwal, Tripti; Anselmetti, Flavio S; Blum, Franziska; Hungerbühler, Konrad; Kohler, Martin; Schmid, Peter; Scheringer, Martin; Sobek, Anna

2011-05-01

Historical records of total organic carbon (TOC), black carbon (BC), and polycyclic aromatic hydrocarbons (PAHs) were reconstructed in dated sediment cores from four nearby lakes in central Switzerland. In the sub-Alpine Lake Thun, located at 558 m a.s.l., the proximity to anthropogenic emission sources is reflected in higher input of BC and PAHs into sediments with fluxes only slightly decreasing during the last decades. PAH/BC ratios are relatively high and correlation between levels of total PAHs and BC is almost inexistent in Lake Thun, probably due to the presence of less condensed forms of the BC spectrum (char BC) that is underestimated with the chemothermal oxidation method applied in this study. The sediment profiles of TOC, BC, and PAHs are noticeably different in the mountain lakes located around 2000 m a.s.l. In Lake Engstlen, the PAH/BC ratios, as well as the correlation between PAHs and BC, point towards appreciable amounts of predominantly light soot particles. Light soot particles have higher mobility and can, therefore, be efficiently transported to this remote site. The proglacial Lake Oberaar is shown to be a receptor of BC and PAHs released by the fast melting adjacent glacier acting as a secondary source for these conservative species temporarily stored in the glacier ice. Finally, Lake Stein is in strong contrast to all other lakes. High flux of BC into Lake Stein, combined with constant temporal evolutions of BC and PAHs, and in particular BC/TOC ratios approaching 100% are all strong indications for a geogenic presence of graphite in its catchment area.
Sediment tracing by `customised' magnetic fingerprinting: from the sub-catchment to the ocean scale

NASA Astrophysics Data System (ADS)

Maher, B.

2009-04-01

Robust identification of catchment suspended sediment sources is a prerequisite both for understanding sediment delivery processes and targeting of effective mitigation measures. Fine sediment delivery can pose management problems, especially with regard to nutrient run-off and siltation of water courses and bodies. Suspended sediment load constitutes the dominant mode of particulate material loss from catchments but its transport is highly episodic. Identification of suspended sediment sources and fluxes is therefore a prerequisite both for understanding of fluvial geomorphic process and systems and for designing strategies to reduce sediment transport, delivery and yields. Here will be discussed sediment ‘fingerprinting', using the magnetic properties of soils and sediments to characterise sediment sources and transport pathways over a very wide variety of spatial scales, from Lake Bassenthwaite in the English Lake District to the Burdekin River in Queensland and even the North Atlantic Ocean during the last glacial maximum. The applicability of magnetic ‘fingerprinting' to such a range of scales and environments has been significantly improved recently through use of new and site-appropriate magnetic measurement techniques, statistical processing and sample treatment options.
Fine-grained suspended sediment source identification for the Kharaa River basin, northern Mongolia

NASA Astrophysics Data System (ADS)

Rode, Michael; Theuring, Philipp; Collins, Adrian L.

2015-04-01

Fine sediment inputs into river systems can be a major source of nutrients and heavy metals and have a strong impact on the water quality and ecosystem functions of rivers and lakes, including those in semiarid regions. However, little is known to date about the spatial distribution of sediment sources in most large scale river basins in Central Asia. Accordingly, a sediment source fingerprinting technique was used to assess the spatial sources of fine-grained (<10 microns) sediment in the 15 000 km2 Kharaa River basin in northern Mongolia. Five field sampling campaigns in late summer 2009, and spring and late summer in both 2010 and 2011, were conducted directly after high water flows, to collect an overall total of 900 sediment samples. The work used a statistical approach for sediment source discrimination with geochemical composite fingerprints based on a new Genetic Algorithm (GA)-driven Discriminant Function Analysis, the Kruskal-Wallis H-test and Principal Component Analysis. The composite fingerprints were subsequently used for numerical mass balance modelling with uncertainty analysis. The contributions of the individual sub-catchment spatial sediment sources varied from 6.4% (the headwater sub-catchment of Sugnugur Gol) to 36.2% (the Kharaa II sub-catchment in the middle reaches of the study basin) with the pattern generally showing higher contributions from the sub-catchments in the middle, rather than the upstream, portions of the study area. The importance of riverbank erosion was shown to increase from upstream to midstream tributaries. The source tracing procedure provides results in reasonable accordance with previous findings in the study region and demonstrates the general applicability and associated uncertainties of an approach for fine-grained sediment source investigation in large scale semi-arid catchments. The combined application of source fingerprinting and catchment modelling approaches can be used to assess whether tracing estimates are credible and in combination such approaches provide a basis for making sediment source apportionment more compelling to catchment stakeholders and managers.
Regional versus local drivers of water quality in the Windermere catchment, Lake District, UK: the dominant influence of wastewater pollution over the past 200 years.

PubMed

Moorhouse, Heather L; McGowan, Suzanne; Taranu, Zofia E; Gregory-Eaves, Irene; Leavitt, Peter R; Jones, Matthew D; Barker, Philip; Brayshaw, Susan A

2018-05-10

Freshwater ecosystems are threatened by multiple anthropogenic stressors acting over different spatial and temporal scales, resulting in toxic algal blooms, reduced water quality, and hypoxia. However, while catchment characteristics act as a 'filter' modifying lake response to disturbance, little is known of the relative importance of different drivers and possible differentiation in the response of upland remote lakes in comparison to lowland, impacted lakes. Moreover, many studies have focussed on single lakes rather than looking at responses across a set of individual, yet connected lake basins. Here we used sedimentary algal pigments as an index of changes in primary producer assemblages over the last ~200 years in a northern temperate watershed consisting of 11 upland and lowland lakes within the Lake District, UK, to test our hypotheses about landscape drivers. Specifically, we expected that the magnitude of change in phototrophic assemblages would be greatest in lowland rather than upland lakes due to more intensive human activities in the watersheds of the former (agriculture, urbanization). Regional parameters, such as climate dynamics, would be the predominant factors regulating lake primary producers in remote upland lakes and thus, synchronize the dynamic of primary producer assemblages in these basins. We found broad support for the hypotheses pertaining to lowland sites as wastewater treatment was the main predictor of changes to primary producer assemblages in lowland lakes. In contrast, upland headwaters responded weakly to variation in atmospheric temperature, and dynamics in primary producers across upland lakes were asynchronous. Collectively, these findings show that nutrient inputs from point sources overwhelm climatic controls of algae and nuisance cyanobacteria, but highlights that large-scale stressors do not always initiate coherent regional lake response. Further, a lake's position in its landscape, its connectivity and proximity to point nutrients are important determinants of changes in production and composition of phototrophic assemblages. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
Early-Holocene intensified Indian summer monsoon and its impact on vegetation: study based on hydrogen and carbon isotope values in long chain alkane from relict lake sediments in the Central Himalaya

NASA Astrophysics Data System (ADS)

Sanyal, P.; Ghosh, S.; Bhushan, R.; Juyal, N.

2017-12-01

The early Holocene was characterized by intensified monsoon, however none of the paleoclimatic records showed the magnitude required to shape the observed landform in the Ganges plain and sediment discharge in the Bay of Bengal. The Tropical Rainfall Measurement Mission data suggests that the Central Himalaya ( 2 km altitude) is characterized by high rainfall and hence paleoclimate proxies from this region would provide excellent opportunity to reconstruct the Holocene monsoon. An attempt has been made, for the first time, to reconstruct the Holocene monsoon using n-alkane δDC29 values of lake sediments from Benital area in the Central Himalaya which receives ca. 80% of the mean annual rainfall during summer monsoon. The n-alkane δDC29 values indicated that early Holocene (ca. 9 ka) was characterised by a wet phase with 70% increase in the rainfall followed by the dry middle-late Holocene which is in agreement with existing continental records. However, the change in intensity as inferred in the present study is maximum compared to the existing records. The comparison of δDC29values and the solar insolation data at 30 °N latitude suggested that migration of the Inter Tropical Convergence Zone controlled the variation in monsoonal rainfall. Comparison with the modern plants, the δ13CC29 values indicated that during ca. pre and post 7 ka the lake catchment was dominated by woody and non-woody plants, respectively. The cross plot between δDC29 and δ13CC29 indicated that at higher rainfall, the δ13CC29 values of catchment vegetation were less-responsive.
SCOPSCO: Scientific Collaboration On Past Speciation Conditions in Lake Ohrid

NASA Astrophysics Data System (ADS)

Wagner, B.; Wilke, T.; Grazhdani, A.; Kostoski, G.; Krastel-Gudegast, S.; Reicherter, K.; Zanchetta, G.

2009-04-01

Lake Ohrid is a transboundary lake with approximately two thirds of its surface area belonging to the Former Yugoslav Republic of Macedonia and about one third belonging to the Republic of Albania. With more than 210 endemic species described, the lake is a unique aquatic ecosystem and a hotspot of biodiversity. This importance was emphasized, when the lake was declared a UNESCO World Heritage Site in 1979, and included as a target area of the International Continental Scientific Drilling Program (ICDP) already in 1993. Though the lake is considered to be the oldest, continuously existing lake in Europe, the age and the origin of Lake Ohrid are not completely unravelled to date. Age estimations vary between one and ten million years and concentrate around two to five million years, and both marine and limnic origin is proposed. Extant sedimentary records from Lake Ohrid cover the last glacial/interglacial cycle and reveal that Lake Ohrid is a valuable archive of volcanic ash dispersal and climate change in the central northern Mediterranean region. These records, however, are too short to provide information about the age and origin of the lake and to unravel the mechanisms controlling the evolutionary development leading to the extraordinary high degree of endemism. Concurrent genetic brakes in several invertebrate groups indicate that major geological and/or environmental events must have shaped the evolutionary history of endemic faunal elements in Lake Ohrid. High-resolution hydroacoustic profiles (INNOMAR SES-96 light and INNOMAR SES-2000 compact) taken between 2004 and 2008, and multichannel seismic (Mini-GI-Gun) studies in 2007 and 2008 demonstrate well the interplay between sedimentation and active tectonics and impressively prove the potential of Lake Ohrid for an ICDP drilling campaign. The maximal sediment thickness is ~680 m in the central basin, where unconformities or erosional features are absent. Thus the complete history of the lake is likely recorded. A deep drilling in Lake Ohrid would help (i) to obtain more precise information about the age and origin of the lake, (ii) to unravel the seismotectonic history of the lake area including effects of major earthquakes and associated mass wasting events, (iii) to obtain a continuous record containing information on volcanic activities and climate changes in the central northern Mediterranean region, and (iv) to better understand the impact of major geological/environmental events on general evolutionary patterns and shaping an extraordinary degree of endemic biodiversity as a matter of global significance. For this purpose, five primary drill sites were selected based on the results obtained from sedimentological studies, tectonic mapping in the catchment and detailed seismic surveys conducted between 2004 and 2008. For the recovery of the up to ca. 680 m long sediment sequences the GLAD800 shall be used.
Strontium isotopic evidence of shifting inflows to Eocene Lake Uinta in the Laramide foreland of Utah

NASA Astrophysics Data System (ADS)

Davis, S. J.; Wiegand, B. A.; Chamberlain, C. P.

2007-12-01

Isotopic records from the Uinta basin in Utah are evidence of an evolving landscape during the early Cenozoic. Combined with studies of provenance and paleoflow, oxygen and carbon isotopic results have recently been interpreted to reflect changes in hydrology and catchment hypsometry as the basin responded to developing relief in the foreland. We now present strontium isotope data from lacustrine limestones indicating significant and rapid (< 1 my) shifts in the source of inflowing surface waters. Provenance of Eocene sediments has been used to argue that water spilling south from an overfilled Lake Gosiute in the Greater Green River basin caused a highstand of the lake in the Piceance Creek basin, which in turn overtopped the Douglas Creek Arch and connected with Lake Uinta in the Uinta basin. The lake highstand was extremely productive, and resulted in the deposition of the rich "Mahogany zone" oil shales. New data shows that the 87Sr/86Sr ratio of lacustrine limestones collected in the Uinta basin is generally low (< 0.7105) for most of the Eocene, but spikes higher (to 0.7122) in samples of the Main Body of the Green River Formation near and within the Mahogany zone. We interpret this data to reflect a period of input of water from Lake Gosiute, where that lake's catchments included exposed basement that was much more radiogenic. The strontium data further supports the interpretation that intraforeland basin development in the central North American Cordillera was largely controlled by shifting drainage patterns as the landscape responded to ongoing Laramide tectonism.
Basis for paleoenvironmental interpretation of magnetic properties of sediment from Upper Klamath Lake (Oregon): Effects of weathering and mineralogical sorting

USGS Publications Warehouse

Rosenbaum, J.G.; Reynolds, R.L.

2004-01-01

Studies of magnetic properties enable reconstruction of environmental conditions that affected magnetic minerals incorporated in sediments from Upper Klamath Lake. Analyses of stream sediment samples from throughout the catchment of Upper Klamath Lake show that alteration of Fe-oxide minerals during subaerial chemical weathering of basic volcanic rocks has significantly changed magnetic properties of surficial deposits. Titanomagnetite, which is abundant both as phenocrysts and as microcrystals in fresh volcanic rocks, is progressively destroyed during weathering. Because fine-grained magnetite is readily altered due to large surface-to-volume ratios, weathering causes an increase in average magnetic grain size as well as reduction in the quantity of titanomagnetite both absolutely and relative to hematite. Hydrodynamic mineralogical sorting also produces differences in magnetic properties among rock and mineral grains of differing sizes. Importantly, removal of coarse silicate and Fe-oxide grains by sorting concentrated extremely fine-grained magnetite in the resulting sediment. The effects of weathering and sorting of minerals cannot be completely separated. These processes combine to produce the magnetic properties of a non-glacial lithic component of Upper Klamath Lake sediments, which is characterized by relatively low magnetite content and coarse magnetic grain size. Hydrodynamic sorting alone causes significant differences between the magnetic properties of glacial flour in lake sediments and of fresh volcanic rocks in the catchment. In comparison to source volcanic rocks, glacial flour in the lake sediment is highly enriched in extremely fine-grained magnetite.
Increasing rates of atmospheric mercury deposition in midcontinental North America

USGS Publications Warehouse

Swain, Edward B.; Engstrom, Daniel R.; Brigham, Mark E.; Henning, Thomas A.; Brezonik, P.L.

1992-01-01

Mercury contamination of remote lakes has been attributed to increasing deposition of atmospheric mercury, yet historic deposition rates and inputs from terrestrial sources are essentially unknown. Sediments of seven headwater lakes in Minnesota and Wisconsin were used to reconstruct regional modern and preindustrial deposition rates of mercury. Whole-basin mercury fluxes, determined from lake-wide arrays of dated cores, indicate that the annual deposition of atmospheric mercury has increased from 3.7 to 12.5 micrograms per square meter since 1850 and that 25 percent of atmospheric mercury deposition to the terrestrial catchment is exported to the lake. The deposition increase is similar among sites, implying regional or global sources for the mercury entering these lakes.
Projecting the impact of regional land-use change and water management policies on lake water quality: an application to periurban lakes and reservoirs.

PubMed

Catherine, Arnaud; Mouillot, David; Maloufi, Selma; Troussellier, Marc; Bernard, Cécile

2013-01-01

As the human population grows, the demand for living space and supplies of resources also increases, which may induce rapid change in land-use/land-cover (LULC) and associated pressures exerted on aquatic habitats. We propose a new approach to forecast the impact of regional land cover change and water management policies (i.e., targets in nutrient loads reduction) on lake and reservoir water eutrophication status using a model that requires minimal parameterisation compared with alternative methods. This approach was applied to a set of 48 periurban lakes located in the Ile de France region (IDF, France) to simulate catchment-scale management scenarios. Model outputs were subsequently compared to governmental agencies' 2030 forecasts. Our model indicated that the efforts made to reduce pressure in the catchment of seepage lakes might be expected to be proportional to the gain that might be obtained, whereas drainage lakes will display little improvement until a critical level of pressure reduction is reached. The model also indicated that remediation measures, as currently planned by governmental agencies, might only have a marginal impact on improving the eutrophication status of lakes and reservoirs within the IDF region. Despite the commitment to appropriately managing the water resources in many countries, prospective tools to evaluate the potential impacts of global change on freshwater ecosystems integrity at medium to large spatial scales are lacking. This study proposes a new approach to investigate the impact of region-scale human-driven changes on lake and reservoir ecological status and could be implemented elsewhere with limited parameterisation. Issues are discussed that relate to model uncertainty and to its relevance as a tool applied to decision-making.
Projecting the Impact of Regional Land-Use Change and Water Management Policies on Lake Water Quality: An Application to Periurban Lakes and Reservoirs

PubMed Central

Catherine, Arnaud; Mouillot, David; Maloufi, Selma; Troussellier, Marc; Bernard, Cécile

2013-01-01

As the human population grows, the demand for living space and supplies of resources also increases, which may induce rapid change in land-use/land-cover (LULC) and associated pressures exerted on aquatic habitats. We propose a new approach to forecast the impact of regional land cover change and water management policies (i.e., targets in nutrient loads reduction) on lake and reservoir water eutrophication status using a model that requires minimal parameterisation compared with alternative methods. This approach was applied to a set of 48 periurban lakes located in the Ile de France region (IDF, France) to simulate catchment-scale management scenarios. Model outputs were subsequently compared to governmental agencies’ 2030 forecasts. Our model indicated that the efforts made to reduce pressure in the catchment of seepage lakes might be expected to be proportional to the gain that might be obtained, whereas drainage lakes will display little improvement until a critical level of pressure reduction is reached. The model also indicated that remediation measures, as currently planned by governmental agencies, might only have a marginal impact on improving the eutrophication status of lakes and reservoirs within the IDF region. Despite the commitment to appropriately managing the water resources in many countries, prospective tools to evaluate the potential impacts of global change on freshwater ecosystems integrity at medium to large spatial scales are lacking. This study proposes a new approach to investigate the impact of region-scale human-driven changes on lake and reservoir ecological status and could be implemented elsewhere with limited parameterisation. Issues are discussed that relate to model uncertainty and to its relevance as a tool applied to decision-making. PMID:23991066
High-resolution characterization of individual flood deposits

NASA Astrophysics Data System (ADS)

Støren, Eivind; Paasche, Øyvind; Hirt, Ann

2014-05-01

In most fluvial landscapes rivers transport sediments within and across catchments throughout the year. During flood events the capacity and competence of the river manifolds, and consequently more sediment are eroded and transported within the catchment. Whenever such sediment-laden rivers reach lakes, sediments are deposited at rate much faster than background sedimentation. For this reason alone, lakes can provide exceptionally rich archives of paleofloods. Flood sediments carry information not only about frequency variability through time, but also about source area(s), the time of the deposit (on a seasonal scale), as well as the evolution of the flood. In order to scrutinize the information that can be extracted from such pristine lake records we have developed an approach where high-resolution data are compared to high-precision measurements of selected samples. More specifically, data from high-resolution X-ray fluorescence (XRF) scanning (Itrax) and magnetic susceptibility (Bartington MS2 point sensor) can potentially provide information on annual to decadal resolution. These fast and effective surface scanning methods are subjected to well-known uncertainties, which can impact the interpretation of individual layers. To overcome this challenge - and obtain the highest possible precision and resolution - precise quantitative analysis of discrete flood layers using magnetic hysteresis measurements and First-order reversal curves (FORCs) as well as conventional X-ray fluorescence spectrometer (Philips PW1404) have been conducted. FORCs are obtained with an Alternating Gradient Force Magnetometer and have exceptional high sensitivity (1 x 10-11 A m2) that allows samples smaller than 200 milligrams to be measured. This means that sediments representing a band of less than a couple of millimeters in the lake sediment cores can be sampled without notable contamination from adjacent non-flood sediments, and analyzed with a high degree of precision (analytical error ±2%). Analyses are carried out on a well-documented lake sediment flood-archive from Meringsdalsvatnet in Southern Norway, which is proven to contain the sedimentary imprint of over hundred floods during the last ca. 10 000 years, including well-known historical events. Preliminary results indicate only minor changes in magnetic mineralogy throughout the record, but notable changes are seen in saturation magnetization, which reflects variations in concentration of the ferromagnetic mineralogy. When these results are compared to corresponding concentration of iron (Fe) and rubidium (Rb) it becomes evident that the core contains two statistical populations, which may indicate two contrasting flood systems. There are at least three potential explanations for this pattern: (1) a dual source area; (2) different mechanisms that trigger floods (spring snowmelting versus intense summer rainstorms); (3) the magnitude of the floods, which influences the sedimentary composition; or 4) a combination of the above.
Monitoring the water balance of Lake Victoria, East Africa, from space

NASA Astrophysics Data System (ADS)

Swenson, Sean; Wahr, John

2009-05-01

SummaryUsing satellite gravimetric and altimetric data, we examine trends in water storage and lake levels of multiple lakes in the Great Rift Valley region of East Africa for the years 2003-2008. GRACE total water storage estimates reveal that water storage declined in much of East Africa, by as much as 60 {mm}/{year}, while altimetric data show that lake levels in some large lakes dropped by as much as 1-2 m. The largest declines occurred in Lake Victoria, the Earth's second largest freshwater body. Because the discharge from the outlet of Lake Victoria is used to generate hydroelectric power, the role of human management in the lake's decline has been questioned. By comparing catchment water storage trends to lake level trends, we confirm that climatic forcing explains only about 50decline. This analysis provides an independent means of assessing the relative impacts of climate and human management on the water balance of Lake Victoria that does not depend on observations of dam discharge, which may not be publically available. In the second part of the study, the individual components of the lake water balance are estimated. Satellite estimates of changes in lake level, precipitation, and evaporation are used with observed lake discharge to develop a parameterization for estimating subsurface inflows due to changes in groundwater storage estimated from satellite gravimetry. At seasonal timescales, this approach provides closure to Lake Victoria's water balance to within 17 {mm}/{month}. The third part of this study uses the water balance of a downstream water body, Lake Kyoga, to estimate the outflow from Lake Victoria remotely. Because Lake Kyoga is roughly 20 times smaller in area than Lake Victoria, its water balance is strongly influenced by inflow from Lake Victoria. Lake Kyoga has been shown to act as a linear reservoir, where its outflow is proportional to the height of the lake. This model can be used with satellite altimetric lake levels to estimate a time series of Lake Victoria discharge with an rms error of about 134 {m}/{s}.

Assessment of heavy metal contamination in the sediments of Nansihu Lake Catchment, China.

PubMed

Liu, Enfeng; Shen, Ji; Yang, Liyuan; Zhang, Enlou; Meng, Xianghua; Wang, Jianjun

2010-02-01

At present, anthropogenic contribution of heavy metals far exceeds natural input in some aquatic sediment, but the proportions are difficult to differentiate due to the changes in sediment characters. In this paper, the metal (Al, Fe, K, Mg, Ca, Cr, Cu, Ni, and Zn) concentrations, grain size, and total organic carbon (TOC) content in the surface and core sediments of Nansihu Lake Catchment (the open lake and six inflow rivers) were determined. The chemical speciations of the metals (Al, Fe, Cr, Cu, Ni, and Zn) in the surface sediments were also analyzed. Approaches of factor analysis, normalized enrichment factor (EF) and the new non-residual fractions enrichment factor (K(NRF)) were used to differentiate the sources of the metals in the sediments, from detrital clastic debris or anthropogenic input, and to quantify the anthropogenic contamination. The results indicate that natural processes were more dominant in concentrating the metals in the surface and core sediments of the open lake. High concentration of Ca and deficiency of other metals in the upper layers of the sediment core were attributed to the input of carbonate minerals in the catchment with increasing human activities since 1980s. High TOC content magnified the deficiency of the metals. Nevertheless, the EF and K(NRF) both reveal moderate to significant anthropogenic contamination of Cr, Cu, Ni, and Zn in the surface sediments of Laoyun River and the estuary and Cr in the surface sediments of Baima River. The proportion of non-residual fractions (acid soluble, reducible, and oxidizable fractions) of Cr, Cu, Ni, and Zn in the contaminated sediments increased to 37-99% from the background levels less than 30%.
Direct and indirect climatic drivers of biotic interactions: ice-cover and carbon runoff shaping Arctic char Salvelinus alpinus and brown trout Salmo trutta competitive asymmetries.

PubMed

Ulvan, Eva M; Finstad, Anders G; Ugedal, Ola; Berg, Ole Kristian

2012-01-01

One of the major challenges in ecological climate change impact science is to untangle the climatic effects on biological interactions and indirect cascading effects through different ecosystems. Here, we test for direct and indirect climatic drivers on competitive impact of Arctic char (Salvelinus alpinus L.) on brown trout (Salmo trutta L.) along a climate gradient in central Scandinavia, spanning from coastal to high-alpine environments. As a measure of competitive impact, trout food consumption was measured using (137)Cs tracer methodology both during the ice-covered and ice-free periods, and contrasted between lakes with or without char coexistence along the climate gradient. Variation in food consumption between lakes was best described by a linear mixed effect model including a three-way interaction between the presence/absence of Arctic char, season and Secchi depth. The latter is proxy for terrestrial dissolved organic carbon run-off, strongly governed by climatic properties of the catchment. The presence of Arctic char had a negative impact on trout food consumption. However, this effect was stronger during ice-cover and in lakes receiving high carbon load from the catchment, whereas no effect of water temperature was evident. In conclusion, the length of the ice-covered period and the export of allochthonous material from the catchment are likely major, but contrasting, climatic drivers of the competitive interaction between two freshwater lake top predators. While future climatic scenarios predict shorter ice-cover duration, they also predict increased carbon run-off. The present study therefore emphasizes the complexity of cascading ecosystem effects in future effects of climate change on freshwater ecosystems.
Evolution of the Lake Victoria basin in the context of coeval rift initiation in East Africa: a 3D numerical model approach

NASA Astrophysics Data System (ADS)

Wichura, Henry; Quinteros, Javier; Melnick, Daniel; Brune, Sascha; Schwanghart, Wolfgang; Strecker, Manfred R.

2015-04-01

Over the last four years sedimentologic and thermochronologic studies in the western and eastern branches of the Cenozoic East African Rift System (EARS) have supported the notion of a broadly contemporaneous onset of normal faulting and rift-basin formation in both segments. These studies support previous interpretations based on geophysical investigations from which an onset of rifting during the Paleogene had been postulated. In light of these studies we explore the evolution of the Lake Victoria basin, a shallow, unfaulted sedimentary basin centered between both branches of the EARS and located in the interior of the East African Plateau (EAP). We quantify the fluvial catchment evolution of the Lake Victoria basin and assess the topographic response of African crust to the onset of rifting in both branches. Furthermore, we evaluate and localize the nature of strain and flexural rift-flank uplift in both branches. We use a 3D numerical forward model that includes nonlinear temperature- and stress-dependent elasto-visco-plastic rheology. The model is able to reproduce the flexural response of variably thick lithosphere to rift-related deformation processes such as lithospheric thinning and asthenospheric upwelling. The model domain covers the entire EAP and integrates extensional processes in a heterogeneous, yet cold and thick cratonic block (Archean Tanzania craton), which is surrounded by mechanically weaker Proterozoic mobile belts, which are characterized by thinner lithosphere ("thin spots"). The lower limits of the craton (170 km) and the mobile belts (120 km) are simulated by different depths of the 1300 °C lithosphere-asthenosphere boundary. We assume a constant extension rate of 4 mm/a throughout the entire simulation of 30 Ma and neglect the effect of dynamic topography and magmatism. Even though the model setup is very simple and the resolution is not high enough to calculate realistic rift-flank uplift, it intriguingly reveals important topographic trends. The model shows that elevation differences of 120 to 180 m between the plateau interior and bordering rift shoulders are pronounced enough to form a closed basin after 6.5 Ma of extension. By that time the catchment area is already comparable to the present-day Lake Victoria catchment. Moreover, the final modeled topography, including 1000 m of dynamic and 500 m of pre-plume topography, yields a base basin elevation of 1110 m, which is also in good agreement with the present-day elevation of Lake Victoria. The combined effects of the formation of an extensive lacustrine depositional environment in the interior of the EAP after 6.5 Ma and rift-shoulder uplift may have forced far-reaching environmental impacts. These may have included the onset of the Lake Victoria microclimate, the influence of the basin and surrounding orographic barriers on precipitation patterns in East Africa, and the establishment of a unique flora and fauna.
Reconstructing transport pathways for late Quaternary dust from eastern Australia using the composition of trace elements of long traveled dusts

NASA Astrophysics Data System (ADS)

Petherick, Lynda M.; McGowan, Hamish A.; Kamber, Balz S.

2009-04-01

The southeast Australian dust transport corridor is the principal pathway through which continental emissions of dust from central and eastern Australia are carried to the oceans by the prevailing mid-latitude westerly circulation. The analysis of trace elements of aeolian dust, preserved in lake sediment on North Stradbroke Island, southeast Queensland, is used to reconstruct variation in the intensity and position of dust transport to the island over the past 25,000 yrs. Separation of local and long traveled dust content of lake sediments is achieved using a unique, four-element (Ga, Ni, Tl and Sc) separation method. The local and continental chronologies of aeolian deposition developed by this study show markedly different records, and indicate varied responses to climate variability on North Stradbroke Island (local aeolian sediment component) and in eastern and central Australia (long traveled dust component). The provenance of the continental component of the record to sub-geologic catchment scales was accomplished using a ternary mixing model in which the chemical identification of dusts extracted, from the lake sediments, was compared to potential chemical characteristics of surface dust from the source areas using 16 trace elements. The results indicate that the position and intensity of dust transport pathways during the late Quaternary varied considerably in response to changing atmospheric circulation patterns as well as to variations in sediment supply to dust source areas, which include the large anabranching river systems of the Lake Eyre and Murray-Darling Basins.
Bromine species fluxes from Lake Constance’s catchment, and a preliminary lake mass balance

NASA Astrophysics Data System (ADS)

Gilfedder, B. S.; Petri, M.; Wessels, M.; Biester, H.

2011-06-01

Bromine was historically termed a cyclic salt in terrestrial freshwater environments due to its perceived conservative cycling between the oceans and the continents. This basic assumption has been challenged recently, with evidence that bromine is involved in dynamic chemical cycles in soils and freshwaters. We present here a study on dissolved bromine species (bromide, organically bound bromine, DOBr) concentrations and fluxes as well as sediment trap bromine levels and fluxes in Lake Constance, a large lake in southern Germany. Water samples were obtained from all major and some minor inflows and outflows over one year, where-after dissolved bromine species were measured by a combination of ICP-MS and ion chromatography coupled to an ICP-MS (IC-ICP-MS). Sediment traps were deployed at two locations for two years with Br, Ti and Zr levels being measured by μ-XRF. 190 t yr -1 of total dissolved bromine (TDBr) was delivered to the lake via 14 rivers and precipitation, with the rivers Alpenrhein (84 t TDBr yr -1) and the Schussen (50 t TDBr yr -1) providing the largest sources. The estimated particulate bromine flux contributed an extra 24-26 t Br yr -1. In comparison, only 40 t TDBr yr -1 was deposited to the lake's catchment by precipitation, and thus ˜80% of the riverine TDBr flux came from soils and rocks. Bromide was the dominant species accounting for, on average, 78% of TDBr concentrations and 93% of TDBr flux to the lake. Despite some high concentrations in the smaller lowland rivers, DOBr was only a minor component of the total riverine bromine flux (˜12 t yr -1, 7%), most of which came from the rivers Schussen, Bregenzer Ach and Argen. In contrast, most of the bromine in the sediment traps was bound to organic matter, and showed a clear seasonal pattern in concentrations, with a maximum in winter and minimum in summer. The summer minimum is thought to be due to dilution of a high Br autochthonous component by low bromine mineral and organic material from the catchment, which is supported by Ti, Zr and Br/C org data. In the lake bromine was irreversibly lost to the sediments, with best flux estimates based on mass-balance and sediment trap data of +50-90 μg Br m -2 d -1. Overall, it appears that bromine is not simply a cyclic salt in the case of Lake Constance, with a clear geological component and dynamic lacustrine biogeochemistry.
Provenance of tetraether membrane lipids in a large temperate lake (Loch Lomond, UK): implications for glycerol dialkyl glycerol tetraether (GDGT)-based palaeothermometry

NASA Astrophysics Data System (ADS)

Buckles, L. K.; Weijers, J. W. H.; Tran, X.-M.; Waldron, S.; Sinninghe Damsté, J. S.

2014-10-01

The application of glycerol dialkyl glycerol tetraether (GDGT)-based palaeoenvironmental proxies, such as the branched vs. isoprenoidal tetratether (BIT) index, TEX86 and the MBT-CBT palaeothermometer, has lately been expanded to lacustrine sediments. Given recent research identifying the production of branched, bacterial GDGTs (brGDGTs) within lakes, it is necessary to ascertain the effect of this lacustrine production on GDGT-based proxies. This study profiles a temperate, monomictic lake (Loch Lomond, UK), analysing labile intact polar GDGT lipids (IPLs) and resilient core GDGT lipids (CLs) in catchment soils, small tributary rivers, lake water and lake sediments. Loch Lomond consists of two basins bisected by the Highland Boundary Fault, resulting in a mesotrophic to oligotrophic gradient from south to north. The north basin is fjord-like, while the south basin is shallow with a lowland catchment. Besides abundant influxes of allochthonous soil- and peat-derived (CL) brGDGTs, brGDGTs are produced in a variety of settings in Loch Lomond. Rather than integrating a scattered soil signal, there is some evidence that small rivers may contribute to the brGDGT pool through addition of brGDGTs produced in situ in these streams. Three hundred days of settling particles and water column profiles of suspended particulate matter (SPM; March and September 2011) reveal brGDGT production throughout the water column, with (IPL and CL) brGDGT distributions varying by basin. In lake sediments, in situ brGDGT production affects the distributions of sedimentary brGDGTs despite high soil- and peat-derived organic matter influxes from the catchment. MBT-CBT-derived mean annual air temperature (MAAT) estimates from soil, river and lake sediments vary widely. A strong bias towards higher MAATs in the south and lower MAATs in the north basin further complicates the application of the proxy. These results emphasise that caution must be exercised when applying the MBT-CBT palaeothermometer to individual lakes in which the use of the proxy has not been validated and therefore the factors affecting its application are not well understood. Despite elevated BIT indices, (partly) due to in situ brGDGT production, reliable TEX86 lake surface temperature (LST) estimates were obtained from SPM with BIT indices up to 0.9. Lower north basin sediments yielded accurate LST estimates but require further evaluation to properly constrain the application of the TEX86 proxy.
Carbon Cycling of Lake Kivu (East Africa): Net Autotrophy in the Epilimnion and Emission of CO2 to the Atmosphere Sustained by Geogenic Inputs

PubMed Central

Borges, Alberto V.; Morana, Cédric; Bouillon, Steven; Servais, Pierre; Descy, Jean-Pierre; Darchambeau, François

2014-01-01

We report organic and inorganic carbon distributions and fluxes in a large (>2000 km2) oligotrophic, tropical lake (Lake Kivu, East Africa), acquired during four field surveys, that captured the seasonal variations (March 2007–mid rainy season, September 2007–late dry season, June 2008–early dry season, and April 2009–late rainy season). The partial pressure of CO2 (pCO2) in surface waters of the main basin of Lake Kivu showed modest spatial (coefficient of variation between 3% and 6%), and seasonal variations with an amplitude of 163 ppm (between 579±23 ppm on average in March 2007 and 742±28 ppm on average in September 2007). The most prominent spatial feature of the pCO2 distribution was the very high pCO2 values in Kabuno Bay (a small sub-basin with little connection to the main lake) ranging between 11213 ppm and 14213 ppm (between 18 and 26 times higher than in the main basin). Surface waters of the main basin of Lake Kivu were a net source of CO2 to the atmosphere at an average rate of 10.8 mmol m−2 d−1, which is lower than the global average reported for freshwater, saline, and volcanic lakes. In Kabuno Bay, the CO2 emission to the atmosphere was on average 500.7 mmol m−2 d−1 (∼46 times higher than in the main basin). Based on whole-lake mass balance of dissolved inorganic carbon (DIC) bulk concentrations and of its stable carbon isotope composition, we show that the epilimnion of Lake Kivu was net autotrophic. This is due to the modest river inputs of organic carbon owing to the small ratio of catchment area to lake surface area (2.15). The carbon budget implies that the CO2 emission to the atmosphere must be sustained by DIC inputs of geogenic origin from deep geothermal springs. PMID:25314144
Calibration of a transient transport model to tritium data in streams and simulation of groundwater ages in the western Lake Taupo catchment, New Zealand

NASA Astrophysics Data System (ADS)

Gusyev, M. A.; Toews, M.; Morgenstern, U.; Stewart, M.; White, P.; Daughney, C.; Hadfield, J.

2013-03-01

Here we present a general approach of calibrating transient transport models to tritium concentrations in river waters developed for the MT3DMS/MODFLOW model of the western Lake Taupo catchment, New Zealand. Tritium has a known pulse-shaped input to groundwater systems due to the bomb tritium in the early 1960s and, with its radioactive half-life of 12.32 yr, allows for the determination of the groundwater age. In the transport model, the tritium input (measured in rainfall) passes through the groundwater system, and the simulated tritium concentrations are matched to the measured tritium concentrations in the river and stream outlets for the Waihaha, Whanganui, Whareroa, Kuratau and Omori catchments from 2000-2007. For the Kuratau River, tritium was also measured between 1960 and 1970, which allowed us to fine-tune the transport model for the simulated bomb-peak tritium concentrations. In order to incorporate small surface water features in detail, an 80 m uniform grid cell size was selected in the steady-state MODFLOW model for the model area of 1072 km2. The groundwater flow model was first calibrated to groundwater levels and stream baseflow observations. Then, the transient tritium transport MT3DMS model was matched to the measured tritium concentrations in streams and rivers, which are the natural discharge of the groundwater system. The tritium concentrations in the rivers and streams correspond to the residence time of the water in the groundwater system (groundwater age) and mixing of water with different age. The transport model output showed a good agreement with the measured tritium values. Finally, the tritium-calibrated MT3DMS model is applied to simulate groundwater ages, which are used to obtain groundwater age distributions with mean residence times (MRTs) in streams and rivers for the five catchments. The effect of regional and local hydrogeology on the simulated groundwater ages is investigated by demonstrating groundwater ages at five model cross-sections to better understand MRTs simulated with tritium-calibrated MT3DMS and lumped parameter models.
Anthropopression markers in lake bottom sediments

NASA Astrophysics Data System (ADS)

Nadolna, Anna; Nowicka, Barbara

2014-05-01

Lakes are vulnerable to various types of anthropogenic disturbances. Responses of lake ecosystems to environmental stressors are varied and depend not only on the type of a factor but also on the lake natural resistance to degradation. Within the EULAKES project an evaluation of anthropogenic stress extent in a flow-through, postglacial, ribbon lake (Lake Charzykowskie) was carried out. It was assumed, that this impact manifests unevenly, depending on a type and degree of the pressure on the shore zones, water quality of tributaries, lake basin shape and dynamics of a water movement. It was stated, that anthropogenic markers are substances accumulated in bottom sediments as a result of allochthonous substances inflow from the catchment and atmosphere. Along the selected transects 105 samples from the top layer of sediments (about 20 cm) was collected representing the contemporary accumulation (about 15 years). The content of selected chemical elements and compounds was examined, including nutrients (TN and TP), heavy metals (arsenic, cadmium, lead, chromium, nickel, copper, zinc, mercury, iron, and manganese) and pesticides (DDT, DDD, DDE, DMDT , γ-HCH). The research was conducted in the deepest points of each lake basin and along the research transects - while choosing the spots, the increased intensity of anthropogenic impact (ports, roads with heavy traffic, wastewater discharge zones, built-up areas) was taken into consideration. The river outlets to the lake, where there are ecotonal zones between limnic and fluvial environment, were also taken into account. Analysis of the markers distribution was carried out against the diversity of chemical characteristics of limnic sediments. Ribbon shape of the lake basin and the dominant wind direction provide an opportunity of easy water mixing to a considerable depth. Intensive waving processes cause removal of the matter from the littoral zone towards lake hollows (separated by the underwater tresholds), where the top layer of sediments consists of organic sediment ("sapropel" type). The littoral zone is dominated by sandy material from the shores denudation. In river mouths sandy deltas are formed. The most contaminated sediments are deposited in the central pool, which is a natural trap for the substances flowing with the river that is draining wastewaters from urban areas. At its mouth the sediment samples were significantly contaminated with chromium, zinc, cadmium, copper, nickel, lead and mercury. A high content of total phosphorus was also detected. A different role is played by a large river flowing through the lake. While flushing the sediments it reduces their pollution. The lowest content of markers was detected in headwater areas and in littoral zones exposed to waving.
Hydrogeology and water chemistry of Infranz catchment springs, Bahir Dar Area, Lake Tana Basin, Ethiopia

NASA Astrophysics Data System (ADS)

Abera, F. N.

2017-12-01

The major springs in the Infranz catchment are a significant source of water for Bahir city and nearby villages, while they help to sustain Infranz River and the downstream wetlands. The aim of the research was to understand the hydrogeological conditions of these high-discharge springs, and to explain the hydrochemical composition of spring waters. Water samples from rainwater and springs were collected and analyzed and compared for major cations and anions. The hydrochemical data analysis showed that all water samples of the springs have freshwater chemistry, Ca-HCO3 type, while deep groundwater shows more evolved types. This indicates limited water-rock interaction and short residence time for the spring waters. The rise of NO3- and PO43- may indicate future water quality degradation unless the anthropogenic activities upgradient and nearby are restricted. The uptake of 75% of spring water for water supply of Bahir Dar results in wetland degradation. Key words: Spring water, Infranz River, Bahir Dar, Ethiopia, hydrochemistry
Lumped parameter, isotopic model simulations of closed-basin lake response to drought in the Pacific Northwest and implications for lake sediment oxygen isotope records.

NASA Astrophysics Data System (ADS)

Steinman, B. A.; Rosenmeier, M.; Abbott, M.

2008-12-01

The economy of the Pacific Northwest relies heavily on water resources from the drought-prone Columbia River and its tributaries, as well as the many lakes and reservoirs of the region. Proper management of these water resources requires a thorough understanding of local drought histories that extends well beyond the instrumental record of the twentieth century, a time frame too short to capture the full range of drought variability in the Pacific Northwest. Here we present a lumped parameter, mass-balance model that provides insight into the influence of hydroclimatological changes on two small, closed-basin systems located in north- central Washington. Steady state model simulations of lake water oxygen isotope ratios using modern climate and catchment parameter datasets demonstrate a strong sensitivity to both the amount and timing of precipitation, and to changes in summertime relative humidity, particularly at annual and decadal time scales. Model tests also suggest that basin hypsography can have a significant impact on lake water oxygen isotope variations, largely through surface area to volume and consequent evaporative flux to volume ratio changes in response to drought and pluvial sequences. Additional simulations using input parameters derived from both on-site and National Climatic Data Center historical climate datasets accurately approximate three years of continuous lake observations (seasonal water sampling and continuous lake level monitoring) and twentieth century oxygen isotope ratios in sediment core authigenic carbonate recovered from the lakes. Results from these model simulations suggest that small, closed-basin lakes in north-central Washington are highly sensitive to changes in the drought-related climate variables, and that long (8000 year), high resolution records of quantitative changes in precipitation and evaporation are obtainable from sediment cores recovered from water bodies of the Pacific Northwest.
Does human activity impact the natural antibiotic resistance background? Abundance of antibiotic resistance genes in 21 Swiss lakes.

PubMed

Czekalski, Nadine; Sigdel, Radhika; Birtel, Julia; Matthews, Blake; Bürgmann, Helmut

2015-08-01

Antibiotic resistance genes (ARGs) are emerging environmental contaminants, known to be continuously discharged into the aquatic environment via human and animal waste. Freshwater aquatic environments represent potential reservoirs for ARG and potentially allow sewage-derived ARG to persist and spread in the environment. This may create increased opportunities for an eventual contact with, and gene transfer to, human and animal pathogens via the food chain or drinking water. However, assessment of this risk requires a better understanding of the level and variability of the natural resistance background and the extent of the human impact. We have analyzed water samples from 21 Swiss lakes, taken at sampling points that were not under the direct influence of local contamination sources and analyzed the relative abundance of ARG using quantitative real-time PCR. Copy numbers of genes mediating resistance to three different broad-spectrum antibiotic classes (sulfonamides: sul1, sul2, tetracyclines: tet(B), tet(M), tet(W) and fluoroquinolones: qnrA) were normalized to copy numbers of bacterial 16S rRNA genes. We used multiple linear regression to assess if ARG abundance is related to human activities in the catchment, microbial community composition and the eutrophication status of the lakes. Sul genes were detected in all sampled lakes, whereas only four lakes contained quantifiable numbers of tet genes, and qnrA remained below detection in all lakes. Our data indicate higher abundance of sul1 in lakes with increasing number and capacity of wastewater treatment plants (WWTPs) in the catchment. sul2 abundance was rather related to long water residence times and eutrophication status. Our study demonstrates the potential of freshwater lakes to preserve antibiotic resistance genes, and provides a reference for ARG abundance from lake systems with low human impact as a baseline for assessing ARG contamination in lake water. Copyright © 2015 Elsevier Ltd. All rights reserved.
Modelling the Loktak Lake Basin to Assess Human Impact on Water Resources

NASA Astrophysics Data System (ADS)

Eliza, K.

2015-12-01

Loktak Lake is an internationally important, Ramsar designated, fresh water wetland system in the state of Manipur, India. The lake was also listed under Montreux Record on account of the ecological modifications that the lake system has witnessed over time. A characteristic feature of this lake is the extensive occurrence of coalesced, naturally or otherwise, vegetative masses floating over it. A contiguous 40 km2 area of Phumdis, as these vegetative masses are locally referred to, also constitutes the only natural home of the endemic and endangered species of Manipur's brow-antlered deer popularly known as Sangai. Appropriately notified as Keibul Lamjao National Park by Government of India, this natural feature is known to be the world's largest floating park. Water quality and sediment deposition on account of soil erosion in its catchments are some of the emerging concerns along with a reported enhanced frequency and duration of flooding of the shore areas, reduced fish catch within a visibly deteriorated overall natural ecosystem. Disturbances of watershed processes, command area management practices, ineffective as indeed largely absent, waste management practices and management interventions linked to the Loktak Hydroelectric Project are often cited as the principal triggers that are seen to be responsible for the damage. An effective management protocol for the Lake requires a rigorous understanding of its hydrobiology and eco-hydrodynamics. The present study is carried out to establish such a characterization of the various rivers systems draining directly into the Lake using MIKE SHE, MIKE 11 HD and MIKE 11 ECO Lab modelling platforms. Water quality modelling was limited to dissolved oxygen (DO), biological oxygen demand (BOD) and water temperature. Model calibration was done using the available measured water quality data. The derived results were then investigated for causal correlation with anthropogenic influences to assess human impact on water resource as a primary step towards the eventual goal to design effective conservation and management practices for the entire Loktak eco-system. Keywords: Water quality modelling, hydrodynamic modelling, rainfall- runoff model, hydrobiology
Process-based model with flood control measures towards more realistic global flood modeling

NASA Astrophysics Data System (ADS)

Tang, Q.; Zhang, X.; Wang, Y.; Mu, M.; Lv, A.; Li, Z.

2017-12-01

In the profoundly human-influenced era, the Anthropocene, increased amount of land was developed in flood plains and many flood control measures were implemented to protect people and infrastructures placed in the flood-prone areas. These human influences (for example, dams and dykes) have altered peak streamflow and flood risk, and are already an integral part of flood. However, most of the process-based flood models have yet to taken into account the human influences. In this study, we used a hydrological model together with an advanced hydrodynamic model to assess flood risk at the Baiyangdian catchment. The Baiyangdian Lake is the largest shallow freshwater lake in North China, and it was used as a flood storage area in the past. A new development hub for the Beijing-Tianjin-Hebei economic triangle, namely the Xiongan new area, was recently established in the flood-prone area around the lake. The shuttle radar topography mission (SRTM) digital elevation model (DEMs) was used to parameterize the hydrodynamic model simulation, and the inundation estimates were compared with published flood maps and observed inundation area during the extreme historical flood events. A simple scheme was carried out to consider the impacts of flood control measures, including the reservoirs in the headwaters and the dykes to be built. By comparing model simulations with and without the influences of flood control measures, we demonstrated the importance of human influences in altering the inundated area and depth under design flood conditions. Based on the SRTM DEM and dam and reservoir data in the Global Reservoir and Dam (GRanD) database, we further discuss the potential to develop a global flood model with human influences.
The Mungo Mega-Lake Event, Semi-Arid Australia: Non-Linear Descent into the Last Ice Age, Implications for Human Behaviour

PubMed Central

Fitzsimmons, Kathryn E.; Stern, Nicola; Murray-Wallace, Colin V.; Truscott, William; Pop, Cornel

2015-01-01

The Willandra Lakes complex is one of the few locations in semi-arid Australia to preserve both paleoenvironmental and Paleolithic archeological archives at high resolution. The stratigraphy of transverse lunette dunes on the lakes’ downwind margins record a late Quaternary sequence of wetting and drying. Within the Willandra system, the Lake Mungo lunette is best known for its preservation of the world’s oldest known ritual burials, and high densities of archeological traces documenting human adaptation to changing environmental conditions over the last 45 ka. Here we identify evidence at Lake Mungo for a previously unrecognised short-lived, very high lake filling phase at 24 ka, just prior to the Last Glacial Maximum. Mega-lake Mungo was up to 5 m deeper than preceding or subsequent lake full events and represented a lake volume increase of almost 250%. Lake Mungo was linked with neighboring Lake Leaghur at two overflow points, creating an island from the northern part of the Mungo lunette. This event was most likely caused by a pulse of high catchment rainfall and runoff, combined with neotectonic activity which may have warped the lake basin. It indicates a non-linear transition to more arid ice age conditions. The mega-lake restricted mobility for people living in the area, yet archeological traces indicate that humans rapidly adapted to the new conditions. People repeatedly visited the island, transporting stone tools across water and exploiting food resources stranded there. They either swam or used watercraft to facilitate access to the island and across the lake. Since there is no evidence for watercraft use in Australia between initial colonization of the continent prior to 45 ka and the mid-Holocene, repeated visits to the island may represent a resurrection of waterfaring technologies following a hiatus of at least 20 ky. PMID:26083665
Hydrology and Alkalinity Regulation of Soft Florida Waters: An Integrated Assessment

NASA Astrophysics Data System (ADS)

Stauffer, Robert E.; Canfield, Daniel E., Jr.

1992-06-01

Natural waters in ridge provinces of Florida and southeast Georgia were classified geographically, by degrees of cultural disturbance, and according to the dominant hydrologic and biogeochemical processes controlling chemistry. The ionic composition of lakes, upland streams, and surficial aquifer (water table) springs in relatively undeveloped catchments reflects the geographic variations in bulk deposition corrected for evapotranspiration (Na, Cl), plus a slight gain (net watershed mobilization) of Mg, and partial to nearly complete losses (net retention) of nitrate, sulfate, Ca, and K. Recharge to the Floridan aquifer in infertile, forested, sandy ridge provinces of northern Florida contains 360-580 μmol CO2. On the basis of indirect geochemical evidence, sulfate retention appears less important in lake sediments than in the region's highly weathered, ferruginous, kaolinitic, sand soils. Silica concentrations in upland streams and water table springs closely reflect the predicted equilibrium between kaolinite and gibbsite. Along with other evidence, the Si concentrations in ridge lakes indicate that seepage inflow is much more important than assumed in Baker et al.'s (1988) regional model. Lakes and streams are acidified either by humic acids or nonmarine sulfate but rarely by both, as reflected by the significant inverse correlation between these two components. Contrary to previous reports, there is no significant difference in alkalinity for culturally undisturbed lakes in the northern Trail versus southern Highlands Ridge areas.
Monitoring Reservoirs Using MERIS And LANDSAT Fused Images : A Case Study Of Polyfitos Reservoir - West Macedonia - Greece

NASA Astrophysics Data System (ADS)

Stefouli, M.; Charou, E.; Vasileiou, E.; Stathopoulos, N.; Perrakis, A.

2012-04-01

Research and monitoring is essential to assess baseline conditions in reservoirs and their watershed and provide necessary information to guide decision-makers. Erosion and degradation of mountainous areas can lead to gradual aggradation of reservoirs reducing their lifetime. Collected measurements and observations have to be communicated to the managers of the reservoirs so as to achieve a common / comprehensive management of a large watershed and reservoir system. At this point Remote Sensing could help as the remotely sensed data are repeatedly and readily available to the end users. Aliakmon is the longest river in Greece, it's length is about 297 km and the surface of the river basin is 9.210 km2.The flow of the river starts from Northwest of Greece and ends in Thermaikos Gulf. The riverbed is not natural throughout the entire route, because constructed dams restrict water and create artificial lakes, such as lake of Polyfitos, that prevent flooding. This lake is used as reservoir, for covering irrigational water needs and the water is used to produce energy from the hydroelectric plant of Public Power Corporation-PPC. The catchment basin of Polyfitos' reservoir covers an area of 847.76 km2. Soil erosion - degradation in the mountainous watershed of streams of Polyfitos reservoir is taking place. It has been estimated that an annual volume of sediments reaching the reservoir is of the order of 244 m3. Geomatic based techniques are used in processing multiple data of the study area. A data inventory was formulated after the acquisition of topographic maps, compilation of geological and hydro-geological maps, compilation of digital elevation model for the area of interest based on satellite data and available maps. It also includes the acquisition of various hydro-meteorological data when available. On the basis of available maps and satellite data, digital elevation models are used in order to delineate the basic sub-catchments of the Polyfytos basin as well as the irrigation network in the area We evaluate the possibility to merge two different resolution satellite data i.e. MERIS/ENVISAT and LANDSAT to facilitate the study of the Polyfitos reservoir. State of the art data fusion techniques, that preserve the best characteristics (spatial, temporal, spectral) of the two types of images are implemented and used to mining information concerning selected parameters. Summer 2011 Landsat and ENVISAT MERIS satellite images are used in order to extract lake water quality parameters such as water clarity -and sediment content. Assessment of the whole watershed of Polyfitos reservoir is carried out for the last 25 years. The methodology presented here can be used to support existing reservoir monitoring programs as it gives regular measurements for the whole of the watershed area of the reservoir. The results can be made available to end-users / reservoir managers, using web/GIS techniques. They can also support environmental awareness of the conditions of watershed of Polyfitos reservoir.
Estimating the SCS runoff curve number in forest catchments of Korea

NASA Astrophysics Data System (ADS)

Choi, Hyung Tae; Kim, Jaehoon; Lim, Hong-geun

2016-04-01

To estimate flood runoff discharge is a very important work in design for many hydraulic structures in streams, rivers and lakes such as dams, bridges, culverts, and so on. So, many researchers have tried to develop better methods for estimating flood runoff discharge. The SCS runoff curve number is an empirical parameter determined by empirical analysis of runoff from small catchments and hillslope plots monitored by the USDA. This method is an efficient method for determining the approximate amount of runoff from a rainfall even in a particular area, and is very widely used all around the world. However, there is a quite difference between the conditions of Korea and USA in topography, geology and land use. Therefore, examinations in adaptability of the SCS runoff curve number need to raise the accuracy of runoff prediction using SCS runoff curve number method. The purpose of this study is to find the SCS runoff curve number based on the analysis of observed data from several experimental forest catchments monitored by the National Institute of Forest Science (NIFOS), as a pilot study to modify SCS runoff curve number for forest lands in Korea. Rainfall and runoff records observed in Gwangneung coniferous and broad leaves forests, Sinwol, Hwasoon, Gongju and Gyeongsan catchments were selected to analyze the variability of flood runoff coefficients during the last 5 years. This study shows that runoff curve numbers of the experimental forest catchments range from 55 to 65. SCS Runoff Curve number method is a widely used method for estimating design discharge for small ungauged watersheds. Therefore, this study can be helpful technically to estimate the discharge for forest watersheds in Korea with more accuracy.
Glacier-induced Hazards in the Trans-Himalaya of Ladakh (NW-India)

NASA Astrophysics Data System (ADS)

Schmidt, Susanne; Dame, Juliane; Nüsser, Marcus

2016-04-01

Glaciers are important water resources for irrigated crop cultivation in the semi-arid Trans-Himalaya of Ladakh (NW-India). Due to global warming, many glaciers of South Asia have retreated over the last century and further ice loss will threaten local livelihoods in the long run. In the short term, an increase of flood events caused by melting glaciers and permafrost is expected for the Himalayan region. Beside large catastrophic events, small outburst floods are 'more' regularly reported for various parts of the region. This also holds true for the Trans-Himalayan region of Ladakh, where small glaciers exist at high altitudes. Caused by glacier retreat, a number of proglacial lakes have been formed, most of them dammed by ice filled moraines. The potential risk of these lakes is shown by recent reports on glacial lake outburst flood in the villages Nidder in October 2010 and Gya in August 2014. The 2014 flood destroyed several agricultural terraces, a new concrete bridge and two houses. Own remote sensing analyses shows the increase of a moraine dammed proglacial lake in the upper catchment area, which grew from about 0.03 to 0.08 km2 between 1969 and 2014. Because of the relatively stable altitude of the lake level, one can assume that the flood was caused by a piping process, initiated by melted ice bodies in the moraine. Already in the 1990s a small GLOF was observed in the village, which destroyed some fields. As in 2014, the lake was not completely spilled and a short-term decrease of the lake area is detectable in remote sensing data. Thus, further GLOF-events can be expected for the future. Beside physical risk factors, population growth and new infrastructure development along the streams and valleys increases potential damages of floods. Therefore, investigations are required to estimate the risks of these small glacial lakes and the potential flood effected area for the case study of Gya as well as for the whole region of Ladakh. Remote sensing data are used to detect glacial lakes and their dynamics, and to derive historical GLOF-events. These results will be contextualized with oral history and local interviews about historical flood events. Due to the small size of these glacial lakes and the fact that many of them are almost always frozen, a monitoring system based on high resolution images and field surveys is required to detect potential lake outburst hazards.
Early Holocene deglaciation of Drangajökull, Vestfirðir, Iceland

NASA Astrophysics Data System (ADS)

Harning, David J.; Geirsdóttir, Áslaug; Miller, Gifford H.; Zalzal, Kate

2016-12-01

The status of Icelandic ice caps during the early Holocene provides important constraints on North Atlantic climate and the mechanisms behind natural climate variability. A recent study postulates that Drangajökull on Vestfirðir, Iceland, persisted through the Holocene Thermal Maximum (HTM, 7.9-5.5 ka) and may be a relic from the last glacial period. We test this hypothesis with a suite of sediment cores from threshold lakes both proximal and distal to the ice cap's modern margin. Distal lakes document rapid early Holocene deglaciation from the coast and across the highlands south of the glacier. Sediment from Skorarvatn, a lake to the north of Drangajökull, shows that the northern margin of the ice cap reached a size comparable to its contemporary limit by ∼10.3 ka. Two southeastern lakes with catchments extending well beneath modern Drangajökull confirm that by ∼9.2 ka, the ice cap was reduced to ∼20% of its current area. A continuous 10.3ka record of biological productivity from Skorarvatn's sediment indicates local peak warmth occurred between 9 and 6.9 ka. The combination of warm and dry summers on Vestfirðir suggests that Drangajökull very likely melted completely shortly after 9.2 ka, similar to most other Icelandic ice caps.

Paleohydrology on Mars constrained by mass balance and mineralogy of pre-Amazonian sodium chloride lakes

NASA Astrophysics Data System (ADS)

Melwani Daswani, M.; Kite, E. S.

2017-09-01

Chloride-bearing deposits on Mars record high-elevation lakes during the waning stages of Mars' wet era (mid-Noachian to late Hesperian). The water source pathways, seasonality, salinity, depth, lifetime, and paleoclimatic drivers of these widespread lakes are all unknown. Here we combine reaction-transport modeling, orbital spectroscopy, and new volume estimates from high-resolution digital terrain models, in order to constrain the hydrologic boundary conditions for forming the chlorides. Considering a T = 0°C system, we find that (1) individual lakes were >100 m deep and lasted decades or longer; (2) if volcanic degassing was the source of chlorine, then the water-to-rock ratio or the total water volume were probably low, consistent with brief excursions above the melting point and/or arid climate; (3) if the chlorine source was igneous chlorapatite, then Cl-leaching events would require a (cumulative) time of >10 years at the melting point; and (4) Cl masses, divided by catchment area, give column densities 0.1-50 kg Cl/m2, and these column densities bracket the expected chlorapatite-Cl content for a seasonally warm active layer. Deep groundwater was not required. Taken together, our results are consistent with Mars having a usually cold, horizontally segregated hydrosphere by the time chlorides formed.
Spatial and temporal variability of greenhouse gas emissions from a small and shallow temperate lake

NASA Astrophysics Data System (ADS)

Praetzel, Leandra; Schmiedeskamp, Marcel; Broder, Tanja; Hüttemann, Caroline; Jansen, Laura; Metzelder, Ulrike; Wallis, Ronya; Knorr, Klaus-Holger; Blodau, Christian

2017-04-01

Small inland waters (< 1 km2) have recently been discovered as significant sources and sinks in the global carbon cycle because they cover larger areas than previously assumed and exhibit a higher metabolic activity than larger lakes. They are further expected to be susceptible to changing climate conditions. So far, little is known about the spatial and temporal variability of carbon dioxide (CO2) and methane (CH4) emissions and in-lake dynamics of CH4 production and oxidation in small, epilimnetic lakes in the temperate zone. Of particular interest is the potential occurrence of "hot spots" and "hot moments" that could contribute significantly to total emissions. To address this knowledge gap, we determined CO2 and CH4 emissions and dynamics to identify their controlling environmental factors in a polymictic small (1.4 ha) and shallow (max. depth approx. 1.5 m) crater lake ("Windsborn") in the Eifel uplands in south-west Germany. As Lake Windsborn has a small catchment area (8 ha) and no surficial inflows, it serves well as a model system for the identification of factors and processes controlling emissions. In 2015, 2016 and 2017 we measured CO2 and CH4 gas fluxes with different techniques across the sediment/water and water/atmosphere interface. Atmospheric exchange was measured using mini-chambers equipped with CO2 sensors and with an infra-red greenhouse gas analyzer for high temporal resolution flux measurements. Ebullition of CH4 was quantified with funnel traps. Sediment properties were examined using pore-water peepers. All measurements were carried out along a transect covering both littoral and central parts of the lake. Moreover, a weather station on a floating platform in the center of the lake recorded meteorological data as well as CO2 concentration in different depths of the water column. So far, Lake Windsborn seems to be a source for both CO2 and CH4 on an annual scale. CO2 emissions generally increased from spring to summer. Even though CO2 uptake could be observed during some periods in spring and fall, CO2 emissions in the summer exceeded the uptake. CO2 and CH4 emissions also appeared to be spatially variable between littoral areas and the inner lake. Shallow areas turned out to be "hot spots" of CO2 emissions whereas CH4 emissions were - against our expectations - highest in the center of the lake. Moreover, CH4 ebullition contributed substantially to total CH4 emissions. Our results show the importance of spatially and temporally highly resolved long-term measurements of greenhouse gas emissions and of potential controlling factors to address diurnal, seasonal and inter-annual variability as well as possible feedbacks to climate change.
Climatic and lacustrine morphometric controls of diatom paleoproductivity in a tropical Andean lake

NASA Astrophysics Data System (ADS)

Bao, R.; Hernández, A.; Sáez, A.; Giralt, S.; Prego, R.; Pueyo, J. J.; Moreno, A.; Valero-Garcés, B. L.

2015-12-01

The coupling of lake dynamics with catchment biogeochemistry is considered the key element controlling primary production in mountain lakes at time scales of a few decades to millennia, yet little is known on the impacts of the morphometry of lakes throughout their ontogeny. As Lake Chungará (Central Andean Altiplano, northern Chile) experienced long-term lake-level fluctuations that strongly modified its area:volume ratio, it is an ideal system for exploring the relative roles that long-term climatic shifts and lake morphometry play on biosiliceous lacustrine productivity. In this paper, we review previous data on the percent contents of total organic carbon, total inorganic carbon, total nitrogen, total biogenic silica, isotopic composition of organic matter, carbonates, and diatom frustules, as well as data on the abundance of the chlorophycean Botryococcus braunii in this lake for the period 12,400-1300 cal yr BP. We also include new data on organic carbon and biogenic silica mass accumulation rates and the diatom assemblage composition of an offshore core dated using 14C and U/Th. Biosiliceous productivity in Lake Chungará was influenced by shifts in allochthonous nutrient inputs related to variability in precipitation. Humid phases dated at approx. 12,400 to 10,000 and 9600 to 7400 cal yr BP coincide with periods of elevated productivity, whereas decreases in productivity were recorded during arid phases dated at approx. 10,000 to 9600 and 7400 to 3550 cal yr BP (Andean mid-Holocene Aridity Period). However, morphometry-related in-lake controls led to a lack of a linear response of productivity to precipitation variability. During the late Glacial to early Holocene, lowstands facilitated complete water column mixing, prompting episodic massive blooms of a large centric diatom, Cyclostephanos cf. andinus. Thus, moderate productivity could be maintained, regardless of aridity, by this phenomenon of morphometric eutrophy during the early history of the lake. The subsequent net increase in lake level introduced modifications in the area of the epilimnion sediments versus the total volume of the epilimnion, preventing complete overturn. Surpassing a certain depth threshold at approx. 8300 cal yr BP caused cessation of the morphometric eutrophy conditions associated with Cyclostephanos cf. andinus superblooms. After 7300 cal yr BP, the lake experienced a decrease in biosiliceous productivity and a change of state that involved a stronger dependence on precipitation variability, with a lesser contribution of diatoms to the total primary productivity. Our results show that the interpretation of lacustrine paleoproductivity records as paleoclimatic archives needs to take into account the effects of changes in the epilimnion sediment area to epilimnion volume ratio in association with lake ontogeny.
Large Carbon Dioxide Fluxes from Headwater Boreal and Sub-Boreal Streams

PubMed Central

Venkiteswaran, Jason J.; Schiff, Sherry L.; Wallin, Marcus B.

2014-01-01

Half of the world's forest is in boreal and sub-boreal ecozones, containing large carbon stores and fluxes. Carbon lost from headwater streams in these forests is underestimated. We apply a simple stable carbon isotope idea for quantifying the CO2 loss from these small streams; it is based only on in-stream samples and integrates over a significant distance upstream. We demonstrate that conventional methods of determining CO2 loss from streams necessarily underestimate the CO2 loss with results from two catchments. Dissolved carbon export from headwater catchments is similar to CO2 loss from stream surfaces. Most of the CO2 originating in high CO2 groundwaters has been lost before typical in-stream sampling occurs. In the Harp Lake catchment in Canada, headwater streams account for 10% of catchment net CO2 uptake. In the Krycklan catchment in Sweden, this more than doubles the CO2 loss from the catchment. Thus, even when corrected for aquatic CO2 loss measured by conventional methods, boreal and sub-boreal forest carbon budgets currently overestimate carbon sequestration on the landscape. PMID:25058488
Large carbon dioxide fluxes from headwater boreal and sub-boreal streams.

PubMed

Venkiteswaran, Jason J; Schiff, Sherry L; Wallin, Marcus B

2014-01-01

Half of the world's forest is in boreal and sub-boreal ecozones, containing large carbon stores and fluxes. Carbon lost from headwater streams in these forests is underestimated. We apply a simple stable carbon isotope idea for quantifying the CO2 loss from these small streams; it is based only on in-stream samples and integrates over a significant distance upstream. We demonstrate that conventional methods of determining CO2 loss from streams necessarily underestimate the CO2 loss with results from two catchments. Dissolved carbon export from headwater catchments is similar to CO2 loss from stream surfaces. Most of the CO2 originating in high CO2 groundwaters has been lost before typical in-stream sampling occurs. In the Harp Lake catchment in Canada, headwater streams account for 10% of catchment net CO2 uptake. In the Krycklan catchment in Sweden, this more than doubles the CO2 loss from the catchment. Thus, even when corrected for aquatic CO2 loss measured by conventional methods, boreal and sub-boreal forest carbon budgets currently overestimate carbon sequestration on the landscape.
Environmental factors prevail over dispersal constraints in determining the distribution and assembly of Trichoptera species in mountain lakes.

PubMed

de Mendoza, Guillermo; Ventura, Marc; Catalan, Jordi

2015-07-01

Aiming to elucidate whether large-scale dispersal factors or environmental species sorting prevail in determining patterns of Trichoptera species composition in mountain lakes, we analyzed the distribution and assembly of the most common Trichoptera (Plectrocnemia laetabilis, Polycentropus flavomaculatus, Drusus rectus, Annitella pyrenaea, and Mystacides azurea) in the mountain lakes of the Pyrenees (Spain, France, Andorra) based on a survey of 82 lakes covering the geographical and environmental extremes of the lake district. Spatial autocorrelation in species composition was determined using Moran's eigenvector maps (MEM). Redundancy analysis (RDA) was applied to explore the influence of MEM variables and in-lake, and catchment environmental variables on Trichoptera assemblages. Variance partitioning analysis (partial RDA) revealed the fraction of species composition variation that could be attributed uniquely to either environmental variability or MEM variables. Finally, the distribution of individual species was analyzed in relation to specific environmental factors using binomial generalized linear models (GLM). Trichoptera assemblages showed spatial structure. However, the most relevant environmental variables in the RDA (i.e., temperature and woody vegetation in-lake catchments) were also related with spatial variables (i.e., altitude and longitude). Partial RDA revealed that the fraction of variation in species composition that was uniquely explained by environmental variability was larger than that uniquely explained by MEM variables. GLM results showed that the distribution of species with longitudinal bias is related to specific environmental factors with geographical trend. The environmental dependence found agrees with the particular traits of each species. We conclude that Trichoptera species distribution and composition in the lakes of the Pyrenees are governed predominantly by local environmental factors, rather than by dispersal constraints. For boreal lakes, with similar environmental conditions, a strong role of dispersal capacity has been suggested. Further investigation should address the role of spatial scaling, namely absolute geographical distances constraining dispersal and steepness of environmental gradients at short distances.
Environmental factors prevail over dispersal constraints in determining the distribution and assembly of Trichoptera species in mountain lakes

PubMed Central

de Mendoza, Guillermo; Ventura, Marc; Catalan, Jordi

2015-01-01

Aiming to elucidate whether large-scale dispersal factors or environmental species sorting prevail in determining patterns of Trichoptera species composition in mountain lakes, we analyzed the distribution and assembly of the most common Trichoptera (Plectrocnemia laetabilis, Polycentropus flavomaculatus, Drusus rectus, Annitella pyrenaea, and Mystacides azurea) in the mountain lakes of the Pyrenees (Spain, France, Andorra) based on a survey of 82 lakes covering the geographical and environmental extremes of the lake district. Spatial autocorrelation in species composition was determined using Moran’s eigenvector maps (MEM). Redundancy analysis (RDA) was applied to explore the influence of MEM variables and in-lake, and catchment environmental variables on Trichoptera assemblages. Variance partitioning analysis (partial RDA) revealed the fraction of species composition variation that could be attributed uniquely to either environmental variability or MEM variables. Finally, the distribution of individual species was analyzed in relation to specific environmental factors using binomial generalized linear models (GLM). Trichoptera assemblages showed spatial structure. However, the most relevant environmental variables in the RDA (i.e., temperature and woody vegetation in-lake catchments) were also related with spatial variables (i.e., altitude and longitude). Partial RDA revealed that the fraction of variation in species composition that was uniquely explained by environmental variability was larger than that uniquely explained by MEM variables. GLM results showed that the distribution of species with longitudinal bias is related to specific environmental factors with geographical trend. The environmental dependence found agrees with the particular traits of each species. We conclude that Trichoptera species distribution and composition in the lakes of the Pyrenees are governed predominantly by local environmental factors, rather than by dispersal constraints. For boreal lakes, with similar environmental conditions, a strong role of dispersal capacity has been suggested. Further investigation should address the role of spatial scaling, namely absolute geographical distances constraining dispersal and steepness of environmental gradients at short distances. PMID:26257867
Photochemical reactivities of dissolved organic matter (DOM) in a sub-alpine lake revealed by EEM-PARAFAC: An insight into the fate of allochthonous DOM in alpine lakes affected by climate change.

PubMed

Du, Yingxun; Zhang, Yuanyuan; Chen, Feizhou; Chang, Yuguang; Liu, Zhengwen

2016-10-15

Due to climate change, tree line advance is occurring in many alpine regions. Within the next 50 to 100years, alpine lake catchments are expected to develop increased vegetation cover similar to that of sub-alpine lake catchments which currently exist below the tree line. Such changes in vegetation could trigger increased allochthonous DOM inputs to alpine lakes. To understand the fate of allochthonous DOM in alpine lakes impacted by climate change, the photochemical reactivity of DOM in sub-alpine Lake Tiancai (located 200m below the tree line) was investigated by excitation emission matrix fluorescence combined with parallel factor analysis (EEM-PARAFAC) and UV-Vis spectra analysis. With photo-exposure, a decrease in apparent DOM molecular weight was observed and 32% DOM was photomineralized to CO2. Interestingly, the aromaticity of DOM increased after photodegradation, as evidenced by increases in both the specific UV absorbance at 254nm (SUVA254) and the humification index (HIX). Five EEM-PARAFAC components were identified, including four terrestrially-derived substances (C1, C2, C3 and C4; allochthonous) and one tryptophan-like substance (C5; autochthonous). Generally, allochthonous DOM represented by C2 and C3 exhibited greater photoreactivity than autochthonous DOM represented by C5. C4 was identified as a possible photoproduct with relatively high aromaticity and photorefractive tendencies and contributed to the observed increase in SUVA254 and HIX. UV light facilitated the photodegradation of DOM and had the greatest effect on the removal of C3. This study provides information on the transformation of EEM-PARAFAC components in a sub-alpine lake, which is important in understanding the fate of increased allochthonous DOM inputs to alpine lakes impacted by climate change. Copyright © 2016 Elsevier B.V. All rights reserved.
Sedimentation influx and volcanic interactions in the Fuji Five Lakes: implications for paleoseismological records

NASA Astrophysics Data System (ADS)

Lamair, Laura; Hubert-Ferrari, Aurélia; Yamamoto, Shinya; El Ouahabi, Meriam; Garrett, Ed; Shishikura, Masanobu; Schmidt, Sabine; Boes, Evelien; Obrochta, Stephen; Nakamura, Atsunori; Miyairi, Yosuke; Yokoyama, Yusuke; De Batist, Marc; Heyvaert, Vanessa M. A.

2017-04-01

The Fuji Fives Lakes are located at the foot of Mount Fuji volcano close to the triple junction, where the North American Plate, the Eurasian plate and the Philippine Sea Plate meet. These lakes are ideally situated to study Mount Fuji volcanism and the interaction between volcanism, changes in lake sedimentation rates and the ability of lakes to record paleoearthquakes. Here, we present newly acquired geological data of Lake Yamanaka and Lake Motosu, including seismic reflection profiles, gravity and piston cores. These two lakes and their respective watersheds were affected by several eruptions of Mount Fuji. Lake Yamanaka, a very shallow lake (max. depth 14 m), was heavily impacted by the scoria fall-out of the A.D. 1707 Hoei eruption of Mount Fuji. A detailed investigation of the effect of the Hoei eruption was conducted on short gravity cores, using high resolution XRD, C/N and 210Pb/137Cs analyses. The preliminary results suggest that the sedimentation rate of Lake Yamanaka drastically reduced after the Hoei eruption, followed by an increase until the present day. Similarly, lacustrine sedimentation in Lake Motosu (max. depth 122 m) was disturbed by Mount Fuji volcanism at a larger scale. The watershed of Lake Motosu was impacted by several lava flows and scoria cones. For example, the Omuro scoria cone reduced the catchment size of Lake Motosu and modified its physiography. The related scoria fall out covered an extensive part of the lake catchment and reduced terrigenous sedimentary influx to Lake Motosu. Within the deep basin of Lake Motosu, seismic reflection data shows two different periods that are distinguished by a major change in the dominant sedimentary processes. During the first period, sublacustrine landslides and turbidity currents were the dominant sedimentation processes. During the second one, the seismic stratigraphy evidences only deposition of numerous turbidites interrupting the hemipelagic sedimentation. Changes in sedimentary processes can be linked to the modification of the lake watershed by Mount Fuji volcanism, leading to a decrease in the sediment volume that can be remobilized, and therefore disappearance of large sublacustrine landslides. Turbidites are deposited due to surficial remobilization of lake slope sediments most probably as a result of earthquake shaking. When studying sedimentological records of lakes to define the paleoearthquake record, eruptions of nearby volcanoes should be taken into account. This study suggests that a large magnitude earthquake occurring few decades after a volcanic eruption (with large scale scoria fall-out), might not be recorded in a lake, or would only be fingerprinted in the sedimentary record by small turbiditic flows.
Impact of the Three-Gorges Dam and water transfer project on Changjiang floods

NASA Astrophysics Data System (ADS)

Nakayama, Tadanobu; Shankman, David

2013-01-01

Increasing frequency of severe floods on the middle and lower Changjiang (Yangtze) River during the past few decades can be attributed to both abnormal monsoon rainfall and landscape changes that include extensive deforestation affecting river sedimentation, and shrinking lakes and levee construction that reduced the areas available for floodwater storage. The Three-Gorges Dam (TGD) and the South-to-North Water Transfer Project (SNWTP) will also affect frequency and intensity of severe floods in the Poyang Lake region of the middle Changjiang. Process-based National Integrated Catchment-based Eco-hydrology (NICE) model predicts that the TGD will increase flood risk during the early summer monsoon against the original justifications for building the dam, relating to complex river-lake-groundwater interactions. Several scenarios predict that morphological change will increase flood risk around the lake. This indicates the importance of managing both flood discharge and sediment deposition for the entire basin. Further, the authors assessed the impact of sand mining in the lake after its prohibition on the Changjiang, and clarified that alternative scenario of sand mining in lakes currently disconnected from the mainstream would reduce the flood risk to a greater extent than intensive dredging along junction channel. Because dry biomasses simulated by the model were linearly related to the Time-Integrated Normalized Difference Vegetation Index (TINDVI) estimated from satellite images, its decadal gradient during 1982-1999 showed a spatially heterogeneous distribution and generally decreasing trends beside the lakes, indicating that the increases in lake reclamation and the resultant decrease in rice productivity are closely related to the hydrologic changes. This integrated approach could help to minimize flood damage and promote better decisions addressing sustainable development.
Volcanic influence of Mt. Fuji on the watershed of Lake Motosu and its impact on the lacustrine sedimentary record

NASA Astrophysics Data System (ADS)

Lamair, Laura; Hubert-Ferrari, Aurélia; Yamamoto, Shinya; El Ouahabi, Meriam; Vander Auwera, Jacqueline; Obrochta, Stephen; Boes, Evelien; Nakamura, Atsunori; Fujiwara, Osamu; Shishikura, Masanobu; Schmidt, Sabine; Siani, Giuseppe; Miyairi, Yosuke; Yokoyama, Yusuke; De Batist, Marc; Heyvaert, Vanessa M. A.; QuakeRecNankai Team

2018-01-01

Lacustrine sediments are particularly sensitive to modifications within the lake catchment. In a volcanic area, sedimentation rates are directly affected by the history of the volcano and its eruptions. Here, we investigate the impact of Mt. Fuji Volcano (Japan) on Lake Motosu and its watershed. The lacustrine infill is studied by combining seismic reflection profiles and sediment cores. We show evidence of changes in sedimentation patterns during the depositional history of Lake Motosu. The frequency of large mass-transport deposits recorded within the lake decreases over the Holocene. Before 8000 cal yr BP, large sublacustrine landslides and turbidites were filling the lacustrine depression. After 8000 cal yr BP, only one large sublacustrine landslide was recorded. The change in sedimentation pattern coincides with a change in sediment accumulation rate. Over the last 8000 cal yr BP, the sediment accumulation rate was not sufficient enough to produce large sublacustrine slope failures. Consequently, the frequency of large mass-transport deposits decreased and only turbidites resulting from surficial slope reworking occurred. These constitute the main sedimentary infill of the deep basin. We link the change in sediment accumulation rate with (i) climate and vegetation changes; and (ii) the Mt. Fuji eruptions which affected the Lake Motosu watershed by reducing its size and strongly modified its topography. Moreover, this study highlights that the deposition of turbidites in the deep basin of Lake Motosu is mainly controlled by the paleobathymetry of the lakefloor. Two large mass-transport deposits, occurring around 8000 cal yr BP and 2000 cal yr BP respectively, modified the paleobathymetry of the lakefloor and therefore changed the turbidite depositional pattern of Lake Motosu.
GloboLakes: A global observatory of lake responses to environmental change.

NASA Astrophysics Data System (ADS)

Groom, Steve; Tyler, Andrew; Hunter, Peter; Spyrakos, Evangelos; Martinez-Vicente, Victor; Merchant, Chris; Cutler, Mark; Rowan, John; Dawson, Terry; Maberly, Stephen; Cavalho, Laurence; Elliot, Alex; Thackery, Stephen; Miller, Claire; Scott, Marian

2014-05-01

The world's freshwater ecosystems are vital components of the global biosphere, yet are vulnerable to climate and other human-induced change. There is increasing recognition that lakes play an important role in global biogeochemical cycling and provide key ecosystem services. However, our understanding of how lakes respond to environmental change at a global scale, and how this impacts on their status and function, is hampered by limited information on their chemical, physical and ecological condition. There are estimated to be over 300 million lakes globally, of which over 17,000 are greater than 10 km2 in surface area. These numbers have limited the systematic study of lake ecosystems. GloboLakes is a five-year UK research programme investigating the state of lakes and their response to climatic and other environmental drivers of change. It will establish a satellite-based observatory with archive and near-real time data processing to produce a time series of observed biogeochemical parameters and lake temperature for over 1000 lakes globally. This will be supported by linked ancillary data on climate and catchment land-use. The ability to monitor a large number of lakes consistently at high frequency and globally will facilitate a paradigm shift in our understanding of how lakes respond to environmental change at different spatial and temporal scales. A key requirement is to validate satellite retrieval algorithms and test the time-series of resulting lake properties such as chlorophyll-a by comparison with in situ data. To support the former extensive bio-optical and constituent data were taken in year 1 of the project in a number of UK lakes with a variety of trophic states. Furthermore, for wider validation activities GloboLakes has established the LIMNADES initiative to create a centralised database of ground bio-optical measurements of worldwide lakes through voluntary cooperation across the international scientific community. This presentation will introduce the GloboLakes project including its scientific ambitions for the next 4 years, present initial results, focussing on in-water optical data and describe the LIMNADES database.
Deltas, freshwater discharge, and waves along the Young Sound, NE Greenland.

PubMed

Kroon, Aart; Abermann, Jakob; Bendixen, Mette; Lund, Magnus; Sigsgaard, Charlotte; Skov, Kirstine; Hansen, Birger Ulf

2017-02-01

A wide range of delta morphologies occurs along the fringes of the Young Sound in Northeast Greenland due to spatial heterogeneity of delta regimes. In general, the delta regime is related to catchment and basin characteristics (geology, topography, drainage pattern, sediment availability, and bathymetry), fluvial discharges and associated sediment load, and processes by waves and currents. Main factors steering the Arctic fluvial discharges into the Young Sound are the snow and ice melt and precipitation in the catchment, and extreme events like glacier lake outburst floods (GLOFs). Waves are subordinate and only rework fringes of the delta plain forming sandy bars if the exposure and fetch are optimal. Spatial gradients and variability in driving forces (snow and precipitation) and catchment characteristics (amount of glacier coverage, sediment characteristics) as well as the strong and local influence of GLOFs in a specific catchment impede a simple upscaling of sediment fluxes from individual catchments toward a total sediment flux into the Young Sound.
Hydrologic data for urban storm runoff from three localities in the Denver metropolitan area, Colorado

USGS Publications Warehouse

Ellis, Sherman R.

1978-01-01

Urban storm-runoff data, collected from 1975 to 1977, on three catchment areas in the Denver, Colo., metropolitan area are presented. The catchment are predominantly a single-family residential catchment area in Littleton, a multifamily residential and commercial catchment area in Lakewood, and a high-density residential and commercial catchment area in Denver. Precipitation, rainfall-runoff, snowmelt-runoff, water-quality (common constituents, nutrients, biochemical oxygen demand, coliform bacteria, and solids, trace elements, and pesticides), and catchment-area data are necessary to use the U.S. Environmental Protection Agency 's Storm Water Management Model II. The urban storm-runoff data may be used by planning, water-management, and environmental-protection agencies to assess the impact of urban storm runoff on the hydrologic system. (Woodard-USGS)
SCOPSCO - Scientific Collaboration On Past Speciation Conditions in Lake Ohrid

NASA Astrophysics Data System (ADS)

Vogel, Hendrik; Wagner, Bernd; Wilke, Thomas; Grazhdani, Andon; Kostoski, Goce; Krastel-Gudegast, Sebastian; Reicherter, Klaus; Zanchetta, Giovanni

2010-05-01

Lake Ohrid is a transboundary lake with approximately two thirds of its surface area belonging to the Former Yugoslav Republic of Macedonia and about one third belonging to the Republic of Albania. With more than 210 endemic species described, the lake is a unique aquatic ecosystem and a hotspot of biodiversity. This importance was emphasized, when the lake was declared a UNESCO World Heritage Site in 1979, and included as a target area of the International Continental Scientific Drilling Program (ICDP) already in 1993. Though the lake is considered to be the oldest, continuously existing lake in Europe, the age and the origin of Lake Ohrid are not completely unravelled to date. Age estimations vary between one and ten million years and concentrate around two to five million years, and both marine and limnic origin is proposed. Extant sedimentary records from Lake Ohrid cover the last glacial/interglacial cycle and reveal that Lake Ohrid is a valuable archive of volcanic ash dispersal and climate change in the central northern Mediterranean region. These records, however, are too short to provide information about the age and origin of the lake and to unravel the mechanisms controlling the evolutionary development leading to the extraordinary high degree of endemism. Concurrent genetic brakes in several invertebrate groups indicate that major geological and/or environmental events must have shaped the evolutionary history of endemic faunal elements in Lake Ohrid. High-resolution hydroacoustic profiles (INNOMAR SES-96 light and INNOMAR SES-2000 compact) taken between 2004 and 2008, and multichannel seismic (Mini-GI-Gun) studies in 2007 and 2008 demonstrate well the interplay between sedimentation and active tectonics and impressively prove the potential of Lake Ohrid for an ICDP drilling campaign. The maximal sediment thickness is ˜680 m in the central basin, where unconformities or erosional features are absent. Thus the complete history of the lake is likely recorded. A deep drilling in Lake Ohrid would help (i) to obtain more precise information about the age and origin of the lake, (ii) to unravel the seismotectonic history of the lake area including effects of major earthquakes and associated mass wasting events, (iii) to obtain a continuous record containing information on volcanic activities and climate changes in the central northern Mediterranean region, and (iv) to better understand the impact of major geological/environmental events on general evolutionary patterns and shaping an extraordinary degree of endemic biodiversity as a matter of global significance. For this purpose, five primary drill sites were selected based on the results obtained from sedimentological studies, tectonic mapping in the catchment and detailed seismic surveys conducted between 2004 and 2008. For the recovery of up to ca. 680 m long sediment sequences at water depths of more than 260 m a newly developed platform operated by DOSECC shall be used. The drilling operation is planned to take place in 2011.
Evaluating the response of Lake Prespa (SW Balkan) to future climate change projections from a high-resolution model

NASA Astrophysics Data System (ADS)

van der Schriek, Tim; Varotsos, Konstantinos V.; Giannakopoulos, Christos

2017-04-01

The Mediterranean stands out globally due to its sensitivity to (future) climate change. Projections suggest that the Balkans will experience precipitation and runoff decreases of up to 30% by 2100. However, these projections show large regional spatial variability. Mediterranean lake-wetland systems are particularly threatened by projected climate changes that compound increasingly intensive human impacts (e.g. water extraction, drainage, pollution and dam-building). Protecting the remaining systems is extremely important for supporting global biodiversity. This protection should be based on a clear understanding of individual lake-wetland hydrological responses to future climate changes, which requires fine-resolution projections and a good understanding of the impact of hydro-climate variability on individual lakes. Climate change may directly affect lake level (variability), volume and water temperatures. In turn, these variables influence lake-ecology, habitats and water quality. Land-use intensification and water abstraction multiply these climate-driven changes. To date, there are no projections of future water level and -temperature of individual Mediterranean lakes under future climate scenarios. These are, however, of crucial importance to steer preservation strategies on the relevant catchment-scale. Here we present the first projections of water level and -temperature of the Prespa Lakes covering the period 2071-2100. These lakes are of global significance for biodiversity, and of great regional socio-economic importance as a water resource and tourist attraction. Impact projections are assessed by the Regional Climate Model RCA4 of the Swedish Meteorological and Hydrological Institute (SMHI) driven by the Max Planck Institute for Meteorology global climate model MPI-ESM-LR under two RCP future emissions scenarios, the RCP4.5 and the RCP8.5, with the simulations carried out in the framework of EURO-CORDEX. Temperature, evapo(transpi)ration and precipitation over the Prespa catchment were simulated with this high horizontal resolution (12 × 12 km) regional climate model. Lake temperatures were derived from surface temperatures based on physical models, while water levels were calculated with the lake water balance model. Climate simulations indicate that annual- and wet season catchment precipitation does not significantly change by the end of the century. The median precipitation decreases, while precipitation variability increases. The percentage of annual precipitation falling in the wet season increases by 5-10%, indicating a stronger seasonality in the precipitation regime. Summer (lake) temperatures and lake surface evaporation will rise significantly under both explored climate change scenarios. Lake impact projections indicate that evaporation changes will cause the water level of Lake Megali Prespa to fall by 5m to 840-839m. The increased precipitation variability will cause large inter-annual water level fluctuations. Average water level may fall even further if: (1) drier summers lead to more water abstraction for irrigation, and (2) there is a reduction in winter snowfall/accumulation and thus less discharge. These findings are of key importance for developing sustainable lake water resource management in a region that is highly vulnerable to future climate change and already experiences significant water stress. Research paves the way for innovative management adaptation strategies focussed on decreasing water abstraction, for example through introducing smart irrigation and selecting more water efficient crops.
The impact of soil redistribution on SOC pools in a Mediterranean agroforestry catchment

NASA Astrophysics Data System (ADS)

Quijano, Laura; Gaspar, Leticia; Lizaga, Iván; Navas, Ana

2017-04-01

Soil redistribution processes play an important role influencing the spatial distribution patterns of soil and associated soil organic carbon (SOC) at landscape scale. Information on drivers of SOC dynamics is key for evaluating both soil degradation and SOC stability that can affect soil quality and sustainability. 137Cs measurements provide a very effective tool to infer spatial patterns of soil redistribution and quantify soil redistribution rates in different landscapes, but to date these data are scarce in mountain Mediterranean agroecosystems. We evaluate the effect of soil redistribution on SOC and SOC pools in relation to land use in a Mediterranean mountain catchment (246 ha). To this purpose, two hundred and four soil bulk cores were collected on a 100 m grid in the Estaña lakes catchment located in the central sector of the Spanish Pyrenees (31T 4656250N 295152E). The study area is an agroforestry and endorheic catchment characterized by the presence of evaporite dissolution induced dolines, some of which host permanent lakes. The selected landscape is representative of rainfed areas of Mediterranean continental climate with erodible lithology and shallow soils, and characterized by an intense anthropogenic activity through cultivation and water management. The cultivated and uncultivated areas are heterogeneously distributed. SOC and SOC pools (the active and decomposable fraction, ACF and the stable carbon fraction SCF) were measured by the dry combustion method and soil redistribution rates were derived from 137Cs measurements. The results showed that erosion predominated in the catchment, most of soil samples were identified as eroded sites (n=114) with an average erosion rate of 26.9±51.4 Mg ha-1 y-1 whereas the mean deposition rate was 13.0±24.2 Mg ha-1 y-1. In cultivated soils (n=54) the average of soil erosion rate was significantly higher (78.5±74.4 Mg ha-1 y-1) than in uncultivated soils (6.8±10.4 Mg ha-1 y-1). Similarly, the mean of soil deposition rate in cultivated soils (n=22) was significantly higher (42.6±35.1 Mg ha-1 y-1) than in uncultivated soils (3.4±3.2 Mg ha-1 y-1). The mean SOC content for all soil samples was 2.5±2.0%. In uncultivated soils, significantly higher (P<0.01) amounts of SOC (3.0±2.6%), ACF (2.1±0.7%) and SCF (0.9±0.4%) were found compared to cultivated soils where the means were 1.1±0.7%, 0.7±0.5% and 0.4±0.3%, respectively. Significant (P<0.05) correlations between SOC, SOC pools and soil redistribution rates indicate that the distribution of SOC pools were significantly affected by soil redistribution in the study area. SOC and SOC pools were significantly higher at depositional (n=90, 2.8±1.8%) than at eroded sampling points (2.2±2.1%). ACF shows greater differences at eroding sites and at depositional sites than SCF reflecting that ACF is more sensitive to soil redistribution processes. Our findings emphasize the role of soil redistribution and land use in influencing the dynamics of SOC, information that can be also relevant in soil management. Improving the knowledge on the relationships between land use, soil redistribution processes and SOC fractions is of interest, especially in these Mediterranean rapidly changing landscapes.
Magnetic Signature of Glacial Flour in Sediments From Bear Lake, Utah/Idaho

NASA Astrophysics Data System (ADS)

Rosenbaum, J. G.; Dean, W. E.; Colman, S. M.; Reynolds, R. L.

2002-12-01

Variations in magnetic properties within an interval of Bear Lake sediments correlative with oxygen isotope stage 2 (OIS 2) and OIS 3 provide a record of glacial flour production for the Uinta Mountains. Like sediments of the same age from Upper Klamath Lake (OR), these Bear Lake sediments have high magnetic susceptibilities (MS) relative to non-glacial-age sediments and contain well-defined millennial-scale variations in magnetic properties. In contrast to glacial flour derived from volcanic rocks surrounding Upper Klamath Lake, glacial flour derived from the Uinta Mountains and deposited in Bear Lake by the Bear River has low magnetite content but high hematite content. The relatively low MS values of younger and older non-glacial-age sediments are due entirely to dilution by non-magnetic endogenic carbonate and to the effects of sulfidic alteration of detrital Fe-oxides. Analysis of samples from streams entering Bear Lake and from along the course of the Bear River demonstrates that, in comparison to other areas of the catchment, sediment derived from the Uinta Mountains is rich in hematite (high HIRM) and aluminum, and poor in magnetite (low MS) and titanium. Within the glacial-age lake sediments, there are strong positive correlations among HIRM, Al/Ti, and fine sediment grain size. MS varies inversely with theses three variables. These relations indicate that the observed millennial-scale variations in magnetic and chemical properties arise from varying proportions of two detrital components: (1) very fine-grained glacial flour derived from Proterozoic metasedimentary rocks in the Uinta Mountains and characterized by high HIRM and low MS, and (2) somewhat coarser material, characterized by higher MS and lower HIRM, derived from widespread sedimentary rocks along the course of the Bear River and around Bear Lake. Measurement of glacial flour incorporated in lake sediments can provide a continuous history of alpine glaciation, because the rate of accumulation of glacial flour probably varies closely with the areal extent of glaciation. In the absence of post-depositional alteration of magnetic minerals, magnetic measurements can provide a highly sensitive tool for assessing variations in glacial flour content if glacial and non-glacial materials have contrasting magnetic properties. For Bear Lake, the required contrast is produced by differences in bedrock underlying glaciated and unglaciated areas.
Direct and indirect climate impact on the lake ecosystem during Late Glacial Period.

NASA Astrophysics Data System (ADS)

Zawiska, Izabela; Słowiński, Michał; Obremska, Milena; Woszczyk, Michał; Milecka, Krystyna

2013-04-01

Climate was the main factor that influenced environment in Late Glacial. The general warming trend was interrupted by cooling periods. This fluctuations had a great impact on the lakes environment not only directly by the changing temperature and precipitation but also indirectly influencing, among others, vegetation cover changes and intensity of erosion which consecutively effected lake productivity. In this study we analyzed the sediments of Lake Łukie located in East part of Poland in Łęczna-Włodawa Lake District, beyond the reach of the last glaciation. In present time lake Łukie is shallow, eutrophic lake and its area do not extend 140ha. The aim of this study was to find out how lake ecosystem changed in Late Glacial under the influence of the climate. In order to reconstruct those changes we did several analysis: subfossil Cladocera, macrofossil, pollen, chemical composition of the sediment (TOC, OC, IC, SiO2biog, SiO2ter). The chronology was based on palinology and correlated with the lake Perespilno chronology which was based on the laminated sediments and several 14C data (lake Perespilno is located 30 km east of Łukie lake). Our results show that during Late Glacial lake Łukie ecosystem changed dynamically. Its history started in Older Dryas, whan the lake was shallow with low biodiversity. The erosion played very important role in the sediment formation as the vegetation cover was sparse, dominated by shrubs and grasses. The Allerod warming caused the deepening of the lake and the increase of biodiversity and productivity. The pine - birch forests developed. At the end of this period fishes appeared in the lake. The Younger Dryas cooling marked very visibly in all the results but though the productivity decreased the biodiversity maintained high. The vegetation cover become more open, with high share of grasses, which caused the increase in the erosion of the catchment. At the end on YD sudden change in lake ecosystem happened, probably caused by the water level drop. This dramatic event was probably caused by the changes in the ground water circulation connected with the permafrost disappearance.
Spatial patterns of lacustrine fish assemblages in a catchment of the Mississippi Alluvial Valley

USGS Publications Warehouse

Andrews, Caroline S.; Miranda, Leandro E.; Goetz, Daniel B.; Kroger, Robert

2014-01-01

Off-channel floodplain lakes are among the first landscape elements to vanish as a consequence of agricultural development. These habitats tend to accumulate sediments at fast rates and are converted to agricultural land as soon as suitable drainage can be attained. Considering that off-channel lakes with limited connectivity contribute greatly to the heterogeneity of fish assemblages, such losses pose great concerns to conservation of biodiversity.

Water input requirements of the rapidly shrinking Dead Sea

NASA Astrophysics Data System (ADS)

Abu Ghazleh, Shahrazad; Hartmann, Jens; Jansen, Nils; Kempe, Stephan

2009-05-01

The deepest point on Earth, the Dead Sea level, has been dropping alarmingly since 1978 by 0.7 m/a on average due to the accelerating water consumption in the Jordan catchment and stood in 2008 at 420 m below sea level. In this study, a terrain model of the surface area and water volume of the Dead Sea was developed from the Shuttle Radar Topography Mission data using ArcGIS. The model shows that the lake shrinks on average by 4 km2/a in area and by 0.47 km3/a in volume, amounting to a cumulative loss of 14 km3 in the last 30 years. The receding level leaves almost annually erosional terraces, recorded here for the first time by Differential Global Positioning System field surveys. The terrace altitudes were correlated among the different profiles and dated to specific years of the lake level regression, illustrating the tight correlation between the morphology of the terrace sequence and the receding lake level. Our volume-level model described here and previous work on groundwater inflow suggest that the projected Dead Sea-Red Sea channel or the Mediterranean-Dead Sea channel must have a carrying capacity of >0.9 km3/a in order to slowly re-fill the lake to its former level and to create a sustainable system of electricity generation and freshwater production by desalinization. Moreover, such a channel will maintain tourism and potash industry on both sides of the Dead Sea and reduce the natural hazard caused by the recession.
Community managed forests dominate the catchment sediment cascade in the mid-hills of Nepal: A compound-specific stable isotope analysis.

PubMed

Upadhayay, Hari Ram; Smith, Hugh G; Griepentrog, Marco; Bodé, Samuel; Bajracharya, Roshan Man; Blake, William; Cornelis, Wim; Boeckx, Pascal

2018-05-08

Soil erosion by water is critical for soil, lake and reservoir degradation in the mid-hills of Nepal. Identification of the nature and relative contribution of sediment sources in rivers is important to mitigate water erosion within catchments and siltation problems in lakes and reservoirs. We estimated the relative contribution of land uses (i.e. sources) to suspended and streambed sediments in the Chitlang catchment using stable carbon isotope signature (δ 13 C) of long-chain fatty acids as a tracer input for MixSIAR, a Bayesian mixing model used to apportion sediment sources. Our findings reveal that the relative contribution of land uses varied between suspended and streambed sediment, but did not change over the monsoon period. Significant over- or under-prediction of source contributions could occur due to overlapping source tracer values, if source groups are classified on a catchment-wide basis. Therefore, we applied a novel deconvolutional framework of MixSIAR (D-MixSIAR) to improve source apportionment of suspended sediment collected at tributary confluences (i.e. sub-catchment level) and at the outlet of the entire catchment. The results indicated that the mixed forest was the dominant (41 ± 13%) contributor of sediment followed by broadleaf forest (15 ± 8%) at the catchment outlet during the pre-wet season, suggesting that forest disturbance as well as high rainfall and steep slopes interact for high sediment generation within the study catchment. Unpaved rural road tracks located on flat and steep slopes (11 ± 8 and 9 ± 7% respectively) almost equally contributed to the sediment. Importantly, agricultural terraces (upland and lowland) had minimal contribution (each <7%) confirming that proper terrace management and traditional irrigation systems played an important role in mitigating sediment generation and delivery. Source contributions had a small temporal, but large spatial, variation in the sediment cascade of Chitlang stream. D-MixSIAR provided significant improvement regarding spatially explicit sediment source apportionment within the entire catchment system. This information is essential to prioritize implementation measures to control erosion in community managed forests to reduce sediment loadings to Kulekhani hydropower reservoir. In conclusion, using compound-specific stable isotope (CSSI) tracers for sediment fingerprinting in combination with a deconvolutional Bayesian mixing model offers a versatile approach to deal with the large tracer variability within catchment land uses and thus to successfully apportion multiple sediment sources. Copyright © 2018. Published by Elsevier B.V.
Stationarity and Inequality from the Mississippi to the Kissimmee: Climatic Control of Temporal Patterns in Catchment Discharge and Solute Export

NASA Astrophysics Data System (ADS)

Jawitz, J. W.

2011-12-01

What are the relative contributions of climatic variability, land management, and local geomorphology in determining the temporal dynamics of streamflow and the export of solutes from watersheds to receiving water bodies? A simple analytical framework is introduced for characterizing the temporal inequality of stream discharge and solute export from catchments using Lorenz diagrams and the associated Gini coefficient. These descriptors are used to illustrate a broad range of observed flow variability with a synthesis of multi-decadal flow data from 22 rivers in Florida. The analytical framework is extended to comprehensively link variability in flows and loads to climatically-driven inputs in terms of these inequality-based metrics. Further, based on a synthesis of data from the basins of the Baltic Sea, the Mississippi River, the Kissimmee River and other tributaries to Lake Okeechobee, FL, it is shown that inter-annual variations in exported loads for geogenic constituents, and for total N and total P, are dominantly controlled by discharge. Emergence of this consistent pattern across diverse managed catchments is attributed to the anthropogenic legacy of accumulated nutrient sources generating memory, similar to ubiquitously present sources for geogenic constituents. Multi-decadal phosphorus load data from 4 of the primary tributaries to Lake Okeechobee and sodium and nitrate load data from 9 of the Hubbard Brook, NH long-term study site catchments are used to examine the relation between inequality of climatic inputs, river flows and catchment loads. The intra-annual loads to Lake Okeechobee are shown to be highly unequal, such that 90% of annual load is delivered in as little as 15% of the time. Analytic expressions are developed for measures of inequality in terms of parameters of the lognormal distribution under general conditions that include intermittency. In cases where climatic variability is high compared to that of concentrations (chemostatic conditions), such as for P in the Lake Okeechobee basin and Na in Hubbard Brook, the temporal inequality of rainfall and flow are strong surrogates for load inequality. However, in cases where variability of concentrations is high compared to that of flows (chemodynamic conditions), such as for nitrate in the Hubbard Brook catchments, load inequality is greater than rainfall or flow inequality. The measured degree of correspondence between climatic, flow, and load inequality for these data sets are shown to be well described using the general inequality framework introduced here. Important implications are that (1) variations in hydro-climatic or anthropogenic forcing can be used to robustly predict inter-annual variations in flows and loads, (2) water quality problems in receiving inland and coastal waters may persist until the accumulated storages of nutrients have been substantially depleted, and (3) remedial measures designed to intercept or capture exported flows and loads must be designed with consideration of the intra-annual inequality.
Find the future from the past: Paleolimnology in Indonesia

NASA Astrophysics Data System (ADS)

Retnaningsih Soeprobowati, Tri; Suedy, Sri Sidodo Agung; Hadiyanto

2018-02-01

Agriculture, hydro electricity power, fisheries, source of drinking water, recreation, and industrial use has led to wide-spread impairment of Indonesia surface waters. Indonesia is rich with various freshwaters, including 840 unique lakes with different size and types, 735 ponds, and 162 dams that covering about 21,000 km2 of area, contain about 500 km3 of water functions as both economically and ecologically purposes. Indonesia is also one of the biggest listed freshwater endemic species in Asia. However, an increase of population and human activities affect a decrease in quantity and quality of several lake ecosystems that able to induce the destruction up to extinction of the lake ecosystem. An increase of lake utilization, with partial management system without considering the preservation and sustainability of ecosystem had reduced lake functions. Paleolimnological approach is one of science and technological approach to support the successfull of grand design of Indonesian lakes conservation and rehabilitation, specifically on the program of lakes' development ecosystem monitoring, evaluation, and information system. The studied on (paleo) limnology in Indonesia had been collected and compared. The vertical distribution of trace elements of Ni, Mg, and B were analyzed by Inductively Coupled Plasma (ICP) with mass spectrophotometry for 44 cm sediment core from Telaga Pengilon Dieng, Java. The paleolimnological studies in Indonesia have been limited, particularly for Indonesian as the first author. Lakes' sediment records the changes condition of catchment area, like a diary book. Reconstruction of the past environmental condition is required to predict the future condition. This can be done using the organism preserved in the sediment, such as diatoms and pollen. Diatoms are unicellular algae that are used extensively in paleoecology. The diatom assemblages in sedimentary records can make direct and indirect inferences about past environmental conditions. The palynological data on the terrestrial and aquatic ecosystem are used as an indicator of recent and paleoecological changes, particularly on the climate, history and floral diversity. Paleolimnological analysis increasingly attention is being given to developing the technique to model human activities.
Sensitivity to acidification of subalpine ponds and lakes in north-western Colorado

USGS Publications Warehouse

Campbell, D.H.; Muths, E.; Turk, J.T.; Corn, P.S.

2004-01-01

Although acidifying deposition in western North America is lower than in many parts of the world, many high-elevation ecosystems there are extremely sensitive to acidification. Previous studies determined that the Mount Zirkel Wilderness Area (MZWA) has the most acidic snowpack and aquatic ecosystems that are among the most sensitive in the region. In this study, spatial and temporal variability of ponds and lakes in and near the MZWA were examined to determine their sensitivity to acidification and the effects of acidic deposition during and after snowmelt. Within the areas identified as sensitive to acidification based on bedrock types, there was substantial variability in acid-neutralizing capacity (ANC), which was related to differences in hydrological flowpaths that control delivery of weathering products to surface waters. Geological and topographic maps were of limited use in predicting acid sensitivity because their spatial resolution was not fine enough to capture the variability of these attributes for lakes and ponds with small catchment areas. Many of the lakes are sensitive to acidification (summer and autumn ANC < 100 µeq L−1), but none of them appeared to be threatened immediately by episodic or chronic acidification. In contrast, 22 ponds had minimum ANC < 30 µeq L−1, indicating that they are extremely sensitive to acidic deposition and could be damaged by episodic acidification, although net acidity (ANC < 0) was not measured in any of the ponds during the study. The lowest measured pH value was 5·4, and pH generally remained less than 6·0 throughout early summer in the most sensitive ponds, indicating that biological effects of acidification are possible at levels of atmospheric deposition that occurred during the study. The aquatic chemistry of lakes was dominated by atmospheric deposition and biogeochemical processes in soils and shallow ground water, whereas the aquatic chemistry of ponds was also affected by organic acids and biogeochemical processes in the water column and at the sediment–water interface. These results indicate that conceptual and mechanistic acidification models that have been developed for lakes and streams may be inadequate for predicting acidification in less-understood systems such as ponds.
Exploring the Causes of Mid-Holocene Drought in the Rocky Mountains Using Hydrologic Forward Models

NASA Astrophysics Data System (ADS)

Meador, E.; Morrill, C.

2017-12-01

We present a quantitative model-data comparison for mid-Holocene (6 ka) lake levels in the Rocky Mountains, with the goals of assessing the skill coupled climate models and hydrologic forward models in simulating climate change and improving our understanding of the factors causing past changes in water resources. The mid-Holocene climate in this area may in some ways be similar to expected future climate, thus improved understanding of the factors causing past changes in water resources have the potential to aid in the process of water allocation for large areas that share a relatively small water source. This project focuses on Little Windy Hill Pond in the Medicine Bow Forest in the Rocky Mountains in southern Wyoming. We first calibrated the Variable Infiltration Capacity (VIC) catchment hydrologic model and the one-dimensional Hostetler Bartlein lake energy-balance model to modern observations, using U.S. Geological Survey stream discharge data and Snow Telemetry (SNOTEL) data to ensure appropriate selection of model parameters. Once the models were calibrated to modern conditions, we forced them with output from eight mid-Holocene coupled climate model simulations completed as part of the Coupled Model Intercomparison Project, Phase 5. Forcing from nearly all of the CMIP5 models generates intense, short-lived droughts for the mid-Holocene that are more severe than any we modeled for the past six decades. The severity of the mid-Holocene droughts could be sufficient, depending on sediment processes in the lake, to account for low lake levels recorded by loss-on-ignition in sediment cores. Our preliminary analysis of model output indicates that the combined effects of decreased snowmelt runoff and increased summer lake evaporation cause low mid-Holocene lake levels. These factors are also expected to be important in the future under anthropogenic climate change.
Sedimentation rates and erosion changes recorded in recent sediments of Lake Piaseczno, south-eastern Poland

NASA Astrophysics Data System (ADS)

Tylmann, Wojciech; Turczyński, Marek; Kinder, Małgorzata

2009-10-01

This paper presents the dating results and basic analyses of recent sediments from Lake Piaseczno. The age of sediments was determined using the 210Pb method and constant flux: constant sedimentation (CF: CS) model. The estimated timescale was in agreement with the AMS14C date from the base of the core. The mean sediment accumulation rate during the last 100 years was calculated as 0.025 g cm-2 a-1. Based on the radiocarbon date, the rate of sediment accumulation below the 210Pb dating horizon was estimated as 0.066 g cm-2 a-1. The variability of main physical properties and sediment components along the core was analysed as well. The sediments were characterised by a very high water content (>80%). Carbonates were either not present or at a very low level (<1%). However, organic and minerogenic matter variability represents an interesting record of increasing erosion intensity in the catchment area. Analysis of archival cartographic materials demonstrated that the most likely reason for the enhanced transport of minerogenic matter to the lake was deforestation caused by human activity in the beginning of the 20th century.
Moments of catchment storm area

NASA Technical Reports Server (NTRS)

Eagleson, P. S.; Wang, Q.

1985-01-01

The portion of a catchment covered by a stationary rainstorm is modeled by the common area of two overlapping circles. Given that rain occurs within the catchment and conditioned by fixed storm and catchment sizes, the first two moments of the distribution of the common area are derived from purely geometrical considerations. The variance of the wetted fraction is shown to peak when the catchment size is equal to the size of the predominant storm. The conditioning on storm size is removed by assuming a probability distribution based upon the observed fractal behavior of cloud and rainstorm areas.
Sources of nitrogen and phosphorus emissions to Irish rivers: estimates from the Source Load Apportionment Model (SLAM)

NASA Astrophysics Data System (ADS)

Mockler, Eva; Deakin, Jenny; Archbold, Marie; Daly, Donal; Bruen, Michael

2017-04-01

More than half of the river and lake water bodies in Europe are at less than good ecological status or potential, and diffuse pollution from agriculture remains a major, but not the only, cause of this poor performance. In Ireland, it is evident that agri-environmental policy and land management practices have, in many areas, reduced nutrient emissions to water, mitigating the potential impact on water quality. However, additional measures may be required in order to further decouple the relationship between agricultural productivity and emissions to water, which is of vital importance given the on-going agricultural intensification in Ireland. Catchment management can be greatly supported by modelling, which can reduce the resources required to analyse large amounts of information and can enable investigations and measures to be targeted. The Source Load Apportionment Model (SLAM) framework was developed to support catchment management in Ireland by characterising the contributions from various sources of phosphorus (P) and nitrogen (N) emissions to water. The SLAM integrates multiple national spatial datasets relating to nutrient emissions to surface water, including land use and physical characteristics of the sub-catchments to predict emissions from point (wastewater, industry discharges and septic tank systems) and diffuse sources (agriculture, forestry, peatlands, etc.). The annual nutrient emissions predicted by the SLAM were assessed against nutrient monitoring data for 16 major river catchments covering 50% of the area of Ireland. At national scale, results indicate that the total average annual emissions to surface water in Ireland are over 2,700 t yr-1 of P and 80,000 t yr-1 of N. The SLAM results include the proportional contributions from individual sources at a range of scales from sub-catchment to national, and show that the main sources of P are from wastewater and agriculture, with wide variations across the country related to local anthropogenic pressures and the hydrogeological setting. Agriculture is the main source of N emissions to water across all regions of Ireland. The SLAM results have been incorporated into an Integrated Catchment Management process and used in conjunction with monitoring data and local knowledge during the characterisation of all Irish water bodies by the Environmental Protection Agency. This demonstrates the successful integration of research into catchment management to inform the identification of (i) the sources of nutrients at regional and local scales and (ii) the potential significant pressures and appropriate mitigation measures.
Assessment of nutrient loadings of a large multipurpose prairie reservoir

NASA Astrophysics Data System (ADS)

Morales-Marín, L. A.; Wheater, H. S.; Lindenschmidt, K. E.

2017-07-01

The relatively low water flow velocities in reservoirs cause them to have high capacities for retaining sediments and pollutants, which can lead to a reduction in downstream nutrient loading. Hence, nutrients can progressively accumulate in reservoirs, resulting in the deterioration of aquatic ecosystems and water quality. Lake Diefenbaker (LD) is a large multipurpose reservoir, located on the South Saskatchewan River (SSR), that serves as a major source of freshwater in Saskatchewan, Canada. Over the past several years, changes in land use (e.g. expansion of urban areas and industrial developments) in the reservoir's catchment have heightened concerns about future water quality in the catchment and in the reservoir. Intensification of agricultural activities has led to an increase in augmented the application of manure and fertilizer for crops and pasture. Although previous research has attempted to quantify nutrient retention in LD, there is a knowledge gap related to the identification of major nutrient sources and quantification of nutrient export from the catchment at different spatial scales. Using the SPAtially Referenced Regression On Watershed (SPARROW) model, this gap has been addressed by assessing water quality regionally, and identifying spatial patterns of factors and processes that affect water quality in the LD catchment. Model results indicate that LD retains about 70% of the inflowing total nitrogen (TN) and 90% of the inflowing total phosphorus (TP) loads, of which fertilizer and manure applied to agricultural fields contribute the greatest proportion. The SPARROW model will be useful as a tool to guide the optimal implementation of nutrient management plans to reduce nutrient inputs to LD.
Radiocarbon constraints on the coupled growth of sediment and organic carbon reservoirs in fluvial systems

NASA Astrophysics Data System (ADS)

Torres, M. A.; Kemeny, P. C.; Fischer, W. W.; Lamb, M. P.

2017-12-01

Vast amounts of sediments are stored transiently in fluvial deposits as they move in rivers from source to sink. The timescale(s) of transient storage have the potential to set the cadence for biogeochemical reactions to occur in river sediments. However, the extent to which storage modulates the chemical composition of river sediments remains unclear. In case of the organic carbon (OC) cycle, transient sediment storage may leave an imprint in the radiocarbon (14C) content of riverine particulate OC (POC), offering a potential tool to trace the coupling of sediment storage and biogeochemical cycling in river systems. We investigated the modern and ancient budgets of sediments and POC in the Efi Haukadalsá River catchment in West Iceland to provide new empirical constraints on the role of sediment storage in the terrestrial OC cycle. This field site is attractive because the basaltic bedrock is free of rock-derived (i.e. "petrogenic") POC such that bulk 14C measurements can be interpreted more directly as constraints on catchment OC storage timescales. Additionally, Lake Haukadalsvatn at the outlet of the river catchment has captured sediment for nearly 13 ka, which offers a complementary record of the evolution of climate-sediment-OC linkages since deglaciation. New 14C measurements show that bulk POC in fine grained fluvial deposits within the Haukadalsá catchment is remarkably old (model ages between 1 and 10 ka). This evidence for "aged" POC in floodplain storage is consistent with previous measurements from Lake Haukadalsvatn, which show that POC is aged in the river system by thousands of years prior to deposition in the lake. Additionally, our estimate of the mean transit time of sediments through the river system matches the millennial-scale reservoir age of riverine POC derived from 14C, which implies a tight coupling between sediment storage and the OC cycle. We interpret the long-term increase in the 14C reservoir age of riverine POC over the last 10 ka preserved in the lake sediments to reflect the growth of a terrestrial sediment reservoir and concomitant POC storage in response to deglaciation. Our results illustrate how sediment storage by fluvial systems strongly influences the terrestrial OC cycle and its response to changes in environmental conditions.
Putting humans in the loop: Using crowdsourced snow information to inform water management

NASA Astrophysics Data System (ADS)

Fedorov, Roman; Giuliani, Matteo; Castelletti, Andrea; Fraternali, Piero

2016-04-01

The unprecedented availability of user generated data on the Web due to the advent of online services, social networks, and crowdsourcing, is opening new opportunities for enhancing real-time monitoring and modeling of environmental systems based on data that are public, low-cost, and spatio-temporally dense, possibly contributing to our ability of making better decisions. In this work, we contribute a novel crowdsourcing procedure for computing virtual snow indexes from public web images, either produced by users or generated by touristic webcams, which is based on a complex architecture designed for automatically crawling content from multiple web data sources. The procedure retains only geo-tagged images containing a mountain skyline, identifies the visible peaks in each image using a public online digital terrain model, and classifies the mountain image pixels as snow or no-snow. This operation yields a snow mask per image, from which it is possible to extract time series of virtual snow indexes representing a proxy of the snow covered area. The value of the obtained virtual snow indexes is estimated in a real world water management problem. We consider the snow-dominated catchment of Lake Como, a regulated lake in Northern Italy, where snowmelt represents the most important contribution to seasonal lake storage, and we used the virtual snow indexes for informing the daily operation of the lake's dam. Numerical results show that such information is effective in extending the anticipation capacity of the lake operations, ultimately improving the system performance.
Remotely Sensed Based Lake/Reservoir Routing in Congo River Basin

NASA Astrophysics Data System (ADS)

Raoufi, R.; Beighley, E.; Lee, H.

2017-12-01

Lake and reservoir dynamics can influence local to regional water cycles but are often not well represented in hydrologic models. One challenge that limits their inclusion in models is the need for detailed storage-discharge behavior that can be further complicated in reservoirs where specific operation rules are employed. Here, the Hillslope River Routing (HRR) model is combined with a remotely sensed based Reservoir Routing (RR) method and applied to the Congo River Basin. Given that topographic data are often continuous over the entire terrestrial surface (i.e., does not differentiate between land and open water), the HRR-RR model integrates topographic derived river networks and catchment boundaries (e.g., HydroSHEDs) with water boundary extents (e.g., Global Lakes and Wetlands Database) to develop the computational framework. The catchments bordering lakes and reservoirs are partitioned into water and land portions, where representative flowpath characteristics are determined and vertical water balance and lateral routings is performed separately on each partition based on applicable process models (e.g., open water evaporation vs. evapotranspiration). To enable reservoir routing, remotely sensed water surface elevations and extents are combined to determine the storage change time series. Based on the available time series, representative storage change patterns are determined. Lake/reservoir routing is performed by combining inflows from the HRR-RR model and the representative storage change patterns to determine outflows. In this study, a suite of storage change patterns derived from remotely sensed measurements are determined representative patterns for wet, dry and average conditions. The HRR-RR model dynamically selects and uses the optimal storage change pattern for the routing process based on these hydrologic conditions. The HRR-RR model results are presented to highlight the importance of lake attenuation/routing in the Congo Basin.
The role of Water Resources Users Associations in hydrological research: experiences from Lake Naivasha Basin, Kenya

NASA Astrophysics Data System (ADS)

Agol, D.

2012-04-01

This paper is based on recent studies in Lake Naivasha Basin that explored the ways in which locally based institutions namely the Water Resources Users Associations (WRUAs) are contributing to hydrological knowledge for decision-making processes. Lake Naivasha is a shallow freshwater body which is situated on the floor of Kenya's Rift Valley. It covers approximately 140 Km2 and supports a rich diversity of plants and animals. The Lake Naivasha Basin faces several challenges associated with over- population, urbanization and intensive agricultural activities. For example, the large-scale floricultural and horticultural export industries around the Lake have attracted thousands of migrants from different parts of Kenya who have settled around the Lake and exert a lot of pressure on its resources. The Lake Naivasha is one of the best examples in Kenya where the WRUAs development process has shown some progress. There are 12 WRUAS across the Lake Basin representing its various sub-catchments. In recent years, the role of WRUAs in the Lake has changed rapidly as they are no longer restricted to just resolving conflicts and fostering cooperation between water users. They now have an additional responsibility of collecting hydrological data within their respective sub-catchments. The majority of WRUA officials have been trained on how to collect data such as reading rain gauges, measuring stream flows, turbidity and sediment loads. The data collected are sent to the relevant government authorities for validation and interpretation and the information derived from this process is used to formulate important strategies such as water allocation plans. Using secondary data analysis, interviews and focus group discussions the study investigated how this new role of the WRUAs is changing the water resource management landscape in the Lake Naivasha Basin. In particular it presents key challenges and opportunities associated with attempts to build capacities of lower level institutions like the WRUAs to take a more active role in participating in evidence based research. Some interesting issues have emerged including data validation, credibility and authenticity of the information generated as well as intellectual property rights.
Land use and flow regime effects on phosphorus chemical dynamics in the fluvial sediment of the Winooski River, Vermont

USGS Publications Warehouse

McDowell, R.W.; Sharpley, A.N.; Chalmers, A.T.

2002-01-01

In the last century, fourfold increase in phosphorus (P) loadings to Lake Champlain, Vermont (VT), USA, have led to nuisance levels of algal growth occurring more often. To better understand the transport, storage, and cycling of P within the lake's catchment, we examined the chemistry, bioavailability and processes controlling sediment P release to waters of the Winooski River, VT, the largest tributary to Lake Champlain. Iron-oxide strip P (algal-bioavailable P) of the river sediments adjacent to agricultural land (3.6 mg kg-1) was greater (P < 0.05) than adjacent to forested land (2.4 mg kg-1). When compared among flow regimes, impoundment (731 mg kg-1) and reservoir sediments (803 mg kg-1) had greater total P concentrations than river sediment (462 mg kg-1). This was attributed to more fines (< 63 ??m) in impoundments and reservoirs (64%) than in river sediments (33%), which also decreased the ability of impoundment sediments to release P to solution and thereby be a sink for P. Although land use and flow regime influenced whether Winooski River sediments acted as a sink or source of P to Lake Champlain, long-term remedial strategies for the catchment should continue to focus on decreasing P losses in agricultural and urban runoff. ?? 2002 Elsevier Science B.V. All rights reserved.
Early land use and centennial scale changes in lake-water organic carbon prior to contemporary monitoring.

PubMed

Meyer-Jacob, Carsten; Tolu, Julie; Bigler, Christian; Yang, Handong; Bindler, Richard

2015-05-26

Organic carbon concentrations have increased in surface waters across parts of Europe and North America during the past decades, but the main drivers causing this phenomenon are still debated. A lack of observations beyond the last few decades inhibits a better mechanistic understanding of this process and thus a reliable prediction of future changes. Here we present past lake-water organic carbon trends inferred from sediment records across central Sweden that allow us to assess the observed increase on a centennial to millennial time scale. Our data show the recent increase in lake-water carbon but also that this increase was preceded by a landscape-wide, long-term decrease beginning already A.D. 1450-1600. Geochemical and biological proxies reveal that these dynamics coincided with an intensification of human catchment disturbance that decreased over the past century. Catchment disturbance was driven by the expansion and later cessation of widespread summer forest grazing and farming across central Scandinavia. Our findings demonstrate that early land use strongly affected past organic carbon dynamics and suggest that the influence of historical landscape utilization on contemporary changes in lake-water carbon levels has thus far been underestimated. We propose that past changes in land use are also a strong contributing factor in ongoing organic carbon trends in other regions that underwent similar comprehensive changes due to early cultivation and grazing over centuries to millennia.
Hydro-climatic forcing of dissolved organic carbon in two boreal lakes of Canada.

PubMed

Diodato, Nazzareno; Higgins, Scott; Bellocchi, Gianni; Fiorillo, Francesco; Romano, Nunzio; Guadagno, Francesco M

2016-11-15

The boreal forest of the northern hemisphere represents one of the world's largest ecozones and contains nearly one third of the world's intact forests and terrestrially stored carbon. Long-term variations in temperature and precipitation have been implied in altering carbon cycling in forest soils, including increased fluxes to receiving waters. In this study, we use a simple hydrologic model and a 40-year dataset (1971-2010) of dissolved organic carbon (DOC) from two pristine boreal lakes (ELA, Canada) to examine the interactions between precipitation and landscape-scale controls of DOC production and export from forest catchments to surface waters. Our results indicate that a simplified hydrologically-based conceptual model can enable the long-term temporal patterns of DOC fluxes to be captured within boreal landscapes. Reconstructed DOC exports from forested catchments in the period 1901-2012 follow largely a sinusoidal pattern, with a period of about 37years and are tightly linked to multi-decadal patterns of precipitation. By combining our model with long-term precipitation estimates, we found no evidence of increasing DOC transport or in-lake concentrations through the 20th century. Copyright © 2016 Elsevier B.V. All rights reserved.
Quantifying the heterogeneity of soil compaction, physical soil properties and soil moisture across multiple spatial scales

NASA Astrophysics Data System (ADS)

Coates, Victoria; Pattison, Ian; Sander, Graham

2016-04-01

England's rural landscape is dominated by pastoral agriculture, with 40% of land cover classified as either improved or semi-natural grassland according to the Land Cover Map 2007. Since the Second World War the intensification of agriculture has resulted in greater levels of soil compaction, associated with higher stocking densities in fields. Locally compaction has led to loss of soil storage and an increased in levels of ponding in fields. At the catchment scale soil compaction has been hypothesised to contribute to increased flood risk. Previous research (Pattison, 2011) on a 40km2 catchment (Dacre Beck, Lake District, UK) has shown that when soil characteristics are homogeneously parameterised in a hydrological model, downstream peak discharges can be 65% higher for a heavy compacted soil than for a lightly compacted soil. However, at the catchment scale there is likely to be a significant amount of variability in compaction levels within and between fields, due to multiple controlling factors. This research focusses in on one specific type of land use (permanent pasture with cattle grazing) and areas of activity within the field (feeding area, field gate, tree shelter, open field area). The aim was to determine if the soil characteristics and soil compaction levels are homogeneous in the four areas of the field. Also, to determine if these levels stayed the same over the course of the year, or if there were differences at the end of the dry (October) and wet (April) periods. Field experiments were conducted in the River Skell catchment, in Yorkshire, UK, which has an area of 120km2. The dynamic cone penetrometer was used to determine the structural properties of the soil, soil samples were collected to assess the bulk density, organic matter content and permeability in the laboratory and the Hydrosense II was used to determine the soil moisture content in the topsoil. Penetration results show that the tree shelter is the most compacted and the open field area is least compacted in both periods. The falling head test showed that soil permeability was lowest around the feeding area and highest in the open field area in both periods. Laboratory tests showed that the tree shelter had the lowest bulk density values, due to the higher levels of organic matter content and the field gate had the highest levels of bulk density in both periods. There was also a significant difference in bulk density at the field gate and open field areas between the two periods. These results highlight statistically significant differences between heavily compacted areas where animals congregate and less-trampled areas of the field.
SCOPSCO - Scientific Collaboration On Past Speciation Conditions in Lake Ohrid

NASA Astrophysics Data System (ADS)

Wagner, B.; Wilke, T.; Grazhdani, A.; Kostoski, G.; Krastel, S.; Reicherter, K. R.; Zanchetta, G.

2009-12-01

Lake Ohrid is a transboundary lake with approximately two thirds of its surface area belonging to the Former Yugoslav Republic of Macedonia and about one third belonging to the Republic of Albania. With more than 210 endemic species described, the lake is a unique aquatic ecosystem and a hotspot of biodiversity. This importance was emphasized, when the lake was declared a UNESCO World Heritage Site in 1979. Though the lake is considered to be the oldest, continuously existing lake in Europe, the age and the origin of Lake Ohrid are not completely unravelled to date. Age estimations vary between one and ten million years and concentrate around two to five million years, and both marine and limnic origin is proposed. Extant sedimentary records from Lake Ohrid cover the last glacial/interglacial cycle and reveal that Lake Ohrid is a valuable archive of volcanic ash dispersal and climate change in the central northern Mediterranean region. These records, however, are too short to provide information about the age and origin of the lake and to unravel the mechanisms controlling the evolutionary development leading to the extraordinary high degree of endemism. Concurrent genetic brakes in several invertebrate groups indicate that major geological and/or environmental events must have shaped the evolutionary history of endemic faunal elements in Lake Ohrid. High-resolution hydroacoustic profiles taken between 2004 and 2008, and multichannel seismic (Mini-GI-Gun) studies in 2007 and 2008 demonstrate well the interplay between sedimentation and active tectonics and impressively prove the potential of Lake Ohrid for an ICDP drilling campaign. The maximal sediment thickness is c. 680 m in the central basin, where unconformities or erosional features are absent. Thus the complete history of the lake is likely recorded. A deep drilling in Lake Ohrid would help (i) to obtain more precise information about the age and origin of the lake, (ii) to unravel the seismotectonic history of the lake area including effects of major earthquakes and associated mass wasting events, (iii) to obtain a continuous record containing information on volcanic activities and climate changes in the central northern Mediterranean region, and (iv) to better understand the impact of major geological/environmental events on general evolutionary patterns and shaping an extraordinary degree of endemic biodiversity as a matter of global significance. For this purpose, five primary drill sites were selected based on the results obtained from sedimentological studies, tectonic mapping in the catchment and detailed seismic surveys conducted between 2004 and 2008. For the recovery of the up to c. 680 m long sediment sequences the GLAD800 shall be used. The drilling operation is planned to take place in 2011.
Comparing the index-flood and multiple-regression methods using L-moments

NASA Astrophysics Data System (ADS)

Malekinezhad, H.; Nachtnebel, H. P.; Klik, A.

In arid and semi-arid regions, the length of records is usually too short to ensure reliable quantile estimates. Comparing index-flood and multiple-regression analyses based on L-moments was the main objective of this study. Factor analysis was applied to determine main influencing variables on flood magnitude. Ward’s cluster and L-moments approaches were applied to several sites in the Namak-Lake basin in central Iran to delineate homogeneous regions based on site characteristics. Homogeneity test was done using L-moments-based measures. Several distributions were fitted to the regional flood data and index-flood and multiple-regression methods as two regional flood frequency methods were compared. The results of factor analysis showed that length of main waterway, compactness coefficient, mean annual precipitation, and mean annual temperature were the main variables affecting flood magnitude. The study area was divided into three regions based on the Ward’s method of clustering approach. The homogeneity test based on L-moments showed that all three regions were acceptably homogeneous. Five distributions were fitted to the annual peak flood data of three homogeneous regions. Using the L-moment ratios and the Z-statistic criteria, GEV distribution was identified as the most robust distribution among five candidate distributions for all the proposed sub-regions of the study area, and in general, it was concluded that the generalised extreme value distribution was the best-fit distribution for every three regions. The relative root mean square error (RRMSE) measure was applied for evaluating the performance of the index-flood and multiple-regression methods in comparison with the curve fitting (plotting position) method. In general, index-flood method gives more reliable estimations for various flood magnitudes of different recurrence intervals. Therefore, this method should be adopted as regional flood frequency method for the study area and the Namak-Lake basin in central Iran. To estimate floods of various return periods for gauged catchments in the study area, the mean annual peak flood of the catchments may be multiplied by corresponding values of the growth factors, and computed using the GEV distribution.

Hydrogeochemical characteristics and assessment of water quality in the Al-Saad Lake, Abha Saudi Arabia

NASA Astrophysics Data System (ADS)

Mallick, Javed

2017-10-01

Hydrogeochemical characteristics and assessment of water quality investigations have been carried out at Abha, located in Saudi Arabia, where Al-Saad Lake represents a rare example of natural endorheic lake. The ecosystem within and around the Al-Saad Lake including catchment area is of great social, cultural, aesthetic, environmental and economic values to Abha. Sampling and experiments of lake water has been carried out with the aim of characterizing the main physico-chemical parameters, such as DO, EC, TDS, Mg2+, Ca2+, Na+, K+, SO4 2-, Cl-, HCO3, NO3 - and F- concentration. The ordinary kriging (OK) method was used to produce the spatial patterns of water quality. The Result of DO (mean 5.38 mg/L) trend in Al-Saad Lake is not very encouraging as majority of the lake area is under DO stress or marginally above it. So, proper management strategies are needed to be formulated to protect flora and fauna of the lake. Furthermore, the chemical analysis results show the abundance of the major cations in the order Mg2+ > Ca2+ > Na+ > K+ whereas the abundance of anions are in the order SO4 2- > Cl- > HCO3 > NO3 - > F-. The result obtained in this investigation inferred that the cations in water i.e. sodium and iron are within the permissible limits but magnesium and potassium have exceeded the permissible limit. Whereas anions such as nitrate and fluoride are within the permissible range but chloride and sulphate have exceeded the permissible limits. The concentration of cation, magnesium (Mg) and potassium (K) in the lake water has exceeded the desirable range (30, 10 mg/L, respectively). This may be due to weathering and transported from rocks and particularly from sulphate deposits such as gypsum and anhydride and subsequently ends up in water. The concentration of anion, Sulphate (SO4) and chloride are above the desirable limit. The major source of bicarbonate are the carbonate rocks containing calcite (CaCO3) and dolomite (CaMg (CO3)2), Calcium (Ca) and Magnesium (Mg) can also be transported from Ca-silicates and Mg-silicates. The piper trilinear plot suggests the increase of Ca and SO4 contents is attributed to dissolution of gypsum and anhydrite, which are commonly found in the quaternary formations of watershed (wadi). Ion exchange, dissolution of calcite, semi-arid climate, alkaline condition and weathering are responsible for high concentration of ions exceeding the desirable limit of the study area.
Attributes for MRB_E2RF1 Catchments by Major River Basins in the Conterminous United States: Base-Flow Index, 2002

USGS Publications Warehouse

Wieczorek, Michael; LaMotte, Andrew E.

2010-01-01

This tabular data set represents the mean base-flow index expressed as a percent, compiled for every catchment of MRB_E2RF1 catchments of Major River Basins (MRBs, Crawford and others, 2006). Base flow is the component of streamflow that can be attributed to ground-water discharge into streams. The source data set is Base-Flow Index for the Conterminous United States (Wolock, 2003). The MRB_E2RF1 catchments are based on a modified version of the U.S. Environmental Protection Agency's (USEPA) ERF1_2 and include enhancements to support national and regional-scale surface-water quality modeling (Nolan and others, 2002; Brakebill and others, 2011). Data were compiled for every catchment of MRB_E2RF1 catchments for the conterminous United States covering New England and Mid-Atlantic (MRB1), South Atlantic-Gulf and Tennessee (MRB2), the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy (MRB3), the Missouri (MRB4), the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf (MRB5), the Rio Grande, Colorado, and the Great basin (MRB6), the Pacific Northwest (MRB7) river basins, and California (MRB8).
Timetable of an operational flood forecasting system

NASA Astrophysics Data System (ADS)

Liechti, Katharina; Jaun, Simon; Zappa, Massimiliano

2010-05-01

At present a new underground part of Zurich main station is under construction. For this purpose the runoff capacity of river Sihl, which is passing beneath the main station, is reduced by 40%. If a flood is to occur the construction site is evacuated and gates can be opened for full runoff capacity to prevent bigger damages. However, flooding the construction site, even if it is controlled, is coupled with costs and retardation. The evacuation of the construction site at Zurich main station takes about 2 to 4 hours and opening the gates takes another 1 to 2 hours each. In the upper part of the 336 km2 Sihl catchment the Sihl lake, a reservoir lake, is situated. It belongs and is used by the Swiss Railway Company for hydropower production. This lake can act as a retention basin for about 46% of the Sihl catchment. Lowering the lake level to gain retention capacity, and therewith safety, is coupled with direct loss for the Railway Company. To calculate the needed retention volume and the water to be released facing unfavourable weather conditions, forecasts with a minimum lead time of 2 to 3 days are needed. Since the catchment is rather small, this can only be realised by the use of meteorological forecast data. Thus the management of the construction site depends on accurate forecasts to base their decisions on. Therefore an operational hydrological ensemble prediction system (HEPS) was introduced in September 2008 by the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL). It delivers daily discharge forecasts with a time horizon of 5 days. The meteorological forecasts are provided by MeteoSwiss and stem from the operational limited-area COSMO-LEPS which downscales the ECMWF ensemble prediction system to a spatial resolution of 7 km. Additional meteorological data for model calibration and initialisation (air temperature, precipitation, water vapour pressure, global radiation, wind speed and sunshine duration) and radar data are also provided by MeteoSwiss. Additional meteorological and hydrological observations are provided by a hydropower company, the Canton of Zurich and the Federal Office for the Environment (FOEN). The hydrological forecasting is calculated by the semi-distributed hydrological model PREVAH (Precipitation-Runoff-EVapotranspiration-HRU-related Model) and is further processed by the hydraulic model FLORIS. Finally the forecasts and alerts along with additional meteorological and hydrological observations and forecasts from collaborating institution are sent to a webserver accessible for decision makers. We will document the setup of our operational flood forecasting system, evaluate its performance and show how the collaboration and communication between science and practice, including all the different interests, works for this particular example.
Towards improved cirque glacier reconstructions: differentiating glacial- from non-glacial sediments by means of environmental magnetism.

NASA Astrophysics Data System (ADS)

Kvisvik, Bjørn Christian; Paasche, Øyvind; Olaf Dahl, Svein

2014-05-01

Skriufonnen, a small cirque glacier (0.4 km2) in Southern Norway, has been monitored for the last 10 years, revealing a short response time to on-going climate change. This is the only remaining glacier in the central mountain massif known as Rondane where investigations of past climate variability are scarce. A series of short (HTH, n=8) and long (piston, n=6) cores from two lakes located downstream of Skriufonnen were retrieved and sediments were dated and analysed. In order to complement and validate lake sediment interpretations i.e., the potential connection to glacier variability, a number of soil samples was collected from the surrounding catchment. The six 110 mm piston cores (< 3.1 m length) and eight sediment surface cores were analysed for grain size distribution, geochemical elements (ITRAX XRF-scanning), organic matter content (LOI), magnetic parameters (magnetic susceptibility; surface and bulk), anhysteretic remanent magnetization (ARM) and Saturation Isothermal remanent magnetizations (sIRM). Consistent age-depth relationships were obtained by AMS-C14 and Pb210 dates showing that the cores cover at least the last 10 000 years. High-resolution analysis (XRF and MS) reveals centennial trends, but also distinct changes in frequency and amplitude. A quiescent period during the Holocene Thermal Optimum (9-6 ka) is followed by a sudden onset of Neoglacial (3.8 ka) activity peaking at 2.4 ka. The Little Ice Age (LIA) peaked at 1800 AD. A weak magnetic signal is observed in all cores. This is explained by the fact that Rondane is made of Sparagmite, an arkosic sandstone partly consisting of metamorphosed sandstone and conglomerate with high content of quarts (SiO2) (between 80 to 87 %) and Feldspar. The Sparagmite is resistant to chemical weathering, making the soils dry and sandy. Catchment sediment samples, running in a transect all the way up from the lakes to the glacier snout were sieved into various size classes (250, 125, 63, 38, 20 μm) prior to measuring bulk susceptibility (Ξbulk) at 293K and 77K. The ratio between the two measurements indicates the relative amount of paramagnetic versus ferromagnetic minerals, and results indicate not only that the finest fractions increase in strength as one gets closer to the glacier front, but also that there are long periods in the cores which is dominated by paramagnetic minerals. The approach employed here suggests that the combination of catchment samples with high-resolution analysis of lake sediment cores provide a more accurate reconstruction of past glacier variability, and has resulted in the first continuous cirque glacier reconstruction from this area.
Sedimentation architecture of the volcanically-dammed Alf valley in the West Eifel Volcanic Field, Germany

NASA Astrophysics Data System (ADS)

Eichhorn, Luise; Lange, Thomas; Engelhardt, Jörn; Polom, Ulrich; Pirrung, Michael; Büchel, Georg

2015-04-01

In the southeastern part of the Quaternary West Eifel Volcanic Field, the Alf valley with its morphologically wide (~ 500 m) and flat valley bottom is visibly outstanding. This flat valley bottom was formed during the Marine Isotope Stage 2 due to fluviolacustrine sediments which deposited upstream of a natural volcanic dam. The dam consisted of lava and scoria breccia from the Wartgesberg Volcano complex (Cipa 1958, Hemfler et al. 1991) that erupted ~ 31 BP (40Ar/ 39Ar dating on glass shards, Mertz, pers. communication 2014). Due to this impoundment, the Alf creek turned into a dendritic lake, trapping the catchment sediments. The overall aim is to create the sedimentation architecture of the Alf valley. In comparison to maar archives like Holzmaar or Meerfelder Maar in the vicinity, the fluviolacustrine sediments of the Alf valley show clay-silt lamination despite the water percolation. This archive covers the transition from the Last Glacial Maximum to Early Holocene (Pirrung et al. 2007). Focus of this study is the creation of a 3D model by applying the program ESRI ArcGIS 10.2 to reconstruct the pre-volcanic Alf valley. Moreover, the sedimentation architecture is reconstructed and the sediment fill quantified. Therefore, the digital elevation model with 5 m resolution from the State Survey and Geobasis Information of Rhineland-Palatinate, polreduced magnetic data measured on top of the Strohn lava stream, shear seismic data and core stratigraphies were utilized. Summarizing previous results, Lake Alf had a catchment area of ~ 55 km² (Meerfelder Maar: 1.27 km²) and a surface area of 8.2 km² (Meerfelder Maar: 0.24 km²) considering a maximum lake water level of 410 m a.s.l.. In the deepest parts (~ 50 m) of Lake Alf, lake sediments are laminated, up to 21 m thick and show a very high sedimentation rate ~ 3 mm a-1 (Dehner Maar ~ 1.5 mm a-1, (Sirocko et al. 2013)). The sediments become coarser upstream und stratigraphically above the fine-grained lake sediments. Due to the density of core locations in the valley and shear seismic data, an architecture model of this high resolution archive was established. Cipa, W. (1958). Erdmagnetische Vermessung einiger Lavaströme und Tuffschlote in der Vorder-Eifel. Geologisches Jahrbuch 75. Hemfler, M. and G. Büchel (1991). Influente Verhältnisse als Folge der Trinkwassergewinnung im Alfbachtal bei Strohn (Westeifel). Pollichia 78. Pirrung, M., G. Büchel and K.-H. Köppen (2007). Hochauflösende fluviolakustrine Sedimente des jüngeren Pleistozän aus dem Alfbachtal bei Gillenfeld (Westeifel) - erste Ergebnisse. Mainzer geowissenschaftliche Mitteilungen 35. Sirocko, F., S. Dietrich, D. Veres, P. M. Grootes, K. Schaber-Mohr, K. Seelos, M.-J. Nadeau, B. Kromer, L. Rothacker, M. Röhner, M. Krbetschek, P. Appleby, U. Hambach, C. Rolf, M. Sudo and S. Grim (2013). Multi-proxy dating of Holocene maar lakes and Pleistocene dry maar sediments in the Eifel, Germany. Quaternary Science Reviews 62.
Reservoir-flooded river mouth areas as sediment traps revealing erosion from peat mining areas - Jukajoki case study in eastern Finland

NASA Astrophysics Data System (ADS)

Tahvanainen, Teemu; Meriläinen, Henna-Kaisa; Haraguchi, Akira; Simola, Heikki

2016-04-01

Many types of soil-disturbing land use have caused excess sedimentation in Finnish lakes. Identification and quantification of catchment sources of sediment material is crucial in cases where demands for remediation measures are considered. We studied recent (50 yr) sediments of four small rivers, all draining to a reservoir impounded in 1971. Catchments of two of the rivers had had peat mining activities from early 1980s until recently, exposing large areas of peat surfaces to erosion. The water level of the reservoir had risen to the river mouth areas of all rivers, while in each case, the river mouth areas still form riverine narrows separable from the main reservoir, hence collecting sedimentation from their own catchments. The original soils under the reservoir water level could readily be observed in core samples, providing a dated horizon under recent sediments. In addition, we used 137Cs-stratigraphies for dating of samples from original river bed locations. As expected, recent sediments of rivers with peat mining influence differed from others e.g. by high organic content and C:N ratios. Stable isotopes 13C and 15N both correlated with C:N (r = 0.799 and r = -0.717, respectively) and they also differentiated the peat-mining influenced samples from other river sediments. Principal components of the physical-chemical variables revealed clearer distinction than any variables separately. Light-microscopy revealed abundance of leafs of Sphagnum mosses in peat-mining influenced river sediments that were nearly absent from other rivers. Spores of Sphagnum were, however, abundant in all river sediments indicating their predominantly airborne origin. We find that combination of several physical-chemical characters rather than any single variable and microscopy of plant remains can result in reliable recognition of peatland-origin of sediment material when non-impacted sites are available for comparison. Dating of disturbed recent sediments is challenging. River-mouth areas with reservoir history can be particularly useful as the terrestrial soil strata provides a dated horizon under recent sediments.
A Global Classification System for Catchment Hydrology

NASA Astrophysics Data System (ADS)

Woods, R. A.

2004-05-01

It is a shocking state of affairs - there is no underpinning scientific taxonomy of catchments. There are widely used global classification systems for climate, river morphology, lakes and wetlands, but for river catchments there exists only a plethora of inconsistent, incomplete regional schemes. By proceeding without a common taxonomy for catchments, freshwater science has missed one of its key developmental stages, and has leapt from definition of phenomena to experiments, theories and models, without the theoretical framework of a classification. I propose the development of a global hierarchical classification system for physical aspects of river catchments, to help underpin physical science in the freshwater environment and provide a solid foundation for classification of river ecosystems. Such a classification scheme can open completely new vistas in hydrology: for example it will be possible to (i) rationally transfer experimental knowledge of hydrological processes between basins anywhere in the world, provided they belong to the same class; (ii) perform meaningful meta-analyses in order to reconcile studies that show inconsistent results (iii) generate new testable hypotheses which involve locations worldwide.
Biomarkers and isotopic fingerprinting to track sediment origin and connectivity at Baldegg Lake (Switzerland)

NASA Astrophysics Data System (ADS)

Lavrieux, Marlène; Meusburger, Katrin; Birkholz, Axel; Alewell, Christine

2017-04-01

Slope destabilization and associated sediment transfer are among the major causes of aquatic ecosystems and surface water quality impairment. Through land uses and agricultural practices, human activities modify the soil erosive risk and the catchment connectivity, becoming a key factor of sediment dynamics. Hence, restoration and management plans of water bodies can only be efficient if the sediment sources and the proportion attributable to different land uses and agricultural practices are identified. Several sediment fingerprinting methods, based on the geochemical (elemental composition), color, magnetic or isotopic (137Cs) sediment properties, are currently in use. However, these tools are not suitable for a land-use based fingerprinting. New organic geochemical approaches are now developed to discriminate source-soil contributions under different land-uses: The compound-specific stable isotopes (CSSI) technique, based on the biomarkers isotopic signature (here, fatty acids δ13C) variability within the plant species, The analysis of highly specific (i.e. source-family- or even source-species-specific) biomarkers assemblages, which use is until now mainly restricted to palaeoenvironmental reconstructions, and which offer also promising prospects for tracing current sediment origin. The approach was applied to reconstruct the spatio-temporal variability of the main sediment sources of Baldegg Lake (Lucern Canton, Switzerland), which suffers from a substantial eutrophication, despite several restoration attempts during the last 40 years. The sediment supplying areas and the exported volumes were identified using CSSI technique and highly specific biomarkers, coupled to a sediment connectivity model. The sediment origin variability was defined through the analysis of suspended river sediments sampled at high flow conditions (short term), and by the analysis of a lake sediment core covering the last 130 years (long term). The results show the utility of biomarkers and CSSI to track organic sources in contrasted land-use settings. Associated to other fingerprinting methods, this approach could in the future become a decision support tool for catchments management.
Establishing a tracer-based sediment budget to preserve wetlands in Mediterranean mountain agroecosystems (NE Spain).

PubMed

Navas, Ana; López-Vicente, Manuel; Gaspar, Leticia; Palazón, Leticia; Quijano, Laura

2014-10-15

Mountain wetlands in Mediterranean regions are particularly threatened in agricultural environments due to anthropogenic activity. An integrated study of source-to-sink sediment fluxes was carried out in an agricultural catchment that holds a small permanent lake included in the European NATURA 2000 Network. More than 1000 yrs of human intervention and the variety of land uses pose a substantial challenge when attempting to estimate sediment fluxes which is the first requirement to protect fragile wetlands. To date, there have been few similar studies and those that have been carried out have not addressed such complex terrain. Geostatistical interpolation and GIS tools were used to derive the soil spatial redistribution from point (137)Cs inventories, and to establish the sediment budget in a catchment located in the Southern Pyrenees. The soil redistribution was intense and soil erosion predominated over soil deposition. On the areas that maintained natural vegetation the median soil erosion and deposition rates were moderate, ranging from 2.6 to 6 Mg ha yr(-1) and 1.5 to 2.1 Mg ha yr(-1), respectively. However, in cultivated fields both erosion and deposition were significantly higher (ca. 20 Mg ha yr(-1)), and the maximum rates were always associated with tillage practices. Farming activities in the last part of the 20th century intensified soil erosion, as evidenced by the 1963 (137)Cs peaks in the lake cores and estimates from the sediment budget indicated a net deposition of 671 Mg yr(-1). Results confirm a siltation risk for the lake and provide a foundation for designing management plans to preserve this threatened wetland. This comprehensive approach provides information useful for understanding processes that influence the patterns and rates of soil transfer and deposition within fragile Mediterranean mountain wetlands subjected to climate and anthropogenic stresses. Copyright © 2014 Elsevier B.V. All rights reserved.
A Sensitivity Analysis of Triggers and Mechanisms of Mass Movements in Fjords

NASA Astrophysics Data System (ADS)

Overeem, I.; Lintern, G.; Hill, P.

2016-12-01

Fjords are characterized by rapid sedimentation as they typically drain glaciated river catchments with high seasonal discharges and large sediment evacuation rates. For this reason, fjords commonly experience submarine mass movements; failures of the steep delta front that trigger tsunamis, and turbidity currents or debris flows. Repeat high-resolution bathymetric surveys, and in-situ process measurements collected in fjords in British Columbia, Canada, indicate that mass movements occur many times per year in some fjords and are more rare and of larger magnitude in other fjords. We ask whether these differences can be attributed to river discharge characteristics or to grainsize characteristics of the delivered sediment. To test our ideas, we couple a climate-driven river sediment transport model, HydroTrend, and a marine sedimentation model, Sedflux2D, to explore the triggers of submarine failures and mechanisms of subsequent turbidity and debris flows. HydroTrend calculates water and suspended sediment transport on a daily basis based on catchment characteristics, glaciated area, lakes and temperature and precipitation regime. Sedflux uses the generated river time-series to simulate delta plumes, failures and mass movements with separate process models. Model uncertainty and parameter sensitivity are assessed using Dakota Tools, which allows for a systematic exploration of the effects of river basin characteristics and climate scenarios on occurrence of hyperpycnal events, delta front sedimentation rate, submarine pore pressure, failure frequency and size, and run-out distances. Preliminary simulation results point to the importance of proglacial lakes and lakes abundance in the river basin, which has profound implications for event-based sediment delivery to the delta apex. Discharge-sediment rating curves can be highly variable based on these parameters. Distinction of turbidity currents and debris flows was found to be most sensitive to both earthquake frequency and delta front grainsize. As a first step we compare these model experiments against field data from the Squamish River and Delta in Howe Sound, BC.
Cogs in the endless machine: lakes, climate change and nutrient cycles: a review.

PubMed

Moss, Brian

2012-09-15

Lakes have, rather grandly, been described as sentinels, integrators and regulators of climate change (Williamson et al., Limnol. Oceanogr. 2009; 54: 2273-82). Lakes are also part of the continuum of the water cycle, cogs in a machine that processes water and elements dissolved and suspended in myriad forms. Assessing the changes in the functioning of the cogs and the machine with respect to these substances as climate changes is clearly important, but difficult. Many other human-induced influences, not least eutrophication, that impact on catchment areas and consequently on lakes, have generally complicated the recording of recent change in sediment records and modern sets of data. The least confounded evidence comes from remote lakes in mountain and polar regions and suggests effects of warming that include mobilisation of ions and increased amounts of phosphorus. A cottage industry has arisen in deduction and prediction of the future effects of climate change on lakes, but the results are very general and precision is marred not only by confounding influences but by the complexity of the lake system and the infinite variety of possible future scenarios. A common conclusion, however, is that warming will increase the intensity of symptoms of eutrophication. Direct experimentation, though expensive and still unusual and confined to shallow lake and wetland systems is perhaps the most reliable approach. Results suggest increased symptoms of eutrophication, and changes in ecosystem structure, but in some respects are different from those deduced from comparisons along latitudinal gradients or by inference from knowledge of lake behaviour. Experiments have shown marked increases in community respiration compared with gross photosynthesis in mesocosm systems and it may be that the most significant churnings of these cogs in the earth-air-water machine will be in their influence on the carbon cycle, with possibly large positive feedback effects on warming. Copyright © 2011 Elsevier B.V. All rights reserved.
Plant DNA metabarcoding of lake sediments: How does it represent the contemporary vegetation

PubMed Central

Lammers, Youri; Yoccoz, Nigel Giles; Jørgensen, Tina; Sjögren, Per; Gielly, Ludovic; Edwards, Mary E.

2018-01-01

Metabarcoding of lake sediments have been shown to reveal current and past biodiversity, but little is known about the degree to which taxa growing in the vegetation are represented in environmental DNA (eDNA) records. We analysed composition of lake and catchment vegetation and vascular plant eDNA at 11 lakes in northern Norway. Out of 489 records of taxa growing within 2 m from the lake shore, 17–49% (mean 31%) of the identifiable taxa recorded were detected with eDNA. Of the 217 eDNA records of 47 plant taxa in the 11 lakes, 73% and 12% matched taxa recorded in vegetation surveys within 2 m and up to about 50 m away from the lakeshore, respectively, whereas 16% were not recorded in the vegetation surveys of the same lake. The latter include taxa likely overlooked in the vegetation surveys or growing outside the survey area. The percentages detected were 61, 47, 25, and 15 for dominant, common, scattered, and rare taxa, respectively. Similar numbers for aquatic plants were 88, 88, 33 and 62%, respectively. Detection rate and taxonomic resolution varied among plant families and functional groups with good detection of e.g. Ericaceae, Roseaceae, deciduous trees, ferns, club mosses and aquatics. The representation of terrestrial taxa in eDNA depends on both their distance from the sampling site and their abundance and is sufficient for recording vegetation types. For aquatic vegetation, eDNA may be comparable with, or even superior to, in-lake vegetation surveys and may therefore be used as an tool for biomonitoring. For reconstruction of terrestrial vegetation, technical improvements and more intensive sampling is needed to detect a higher proportion of rare taxa although DNA of some taxa may never reach the lake sediments due to taphonomical constrains. Nevertheless, eDNA performs similar to conventional methods of pollen and macrofossil analyses and may therefore be an important tool for reconstruction of past vegetation. PMID:29664954
Plant DNA metabarcoding of lake sediments: How does it represent the contemporary vegetation.

PubMed

Alsos, Inger Greve; Lammers, Youri; Yoccoz, Nigel Giles; Jørgensen, Tina; Sjögren, Per; Gielly, Ludovic; Edwards, Mary E

2018-01-01

Metabarcoding of lake sediments have been shown to reveal current and past biodiversity, but little is known about the degree to which taxa growing in the vegetation are represented in environmental DNA (eDNA) records. We analysed composition of lake and catchment vegetation and vascular plant eDNA at 11 lakes in northern Norway. Out of 489 records of taxa growing within 2 m from the lake shore, 17-49% (mean 31%) of the identifiable taxa recorded were detected with eDNA. Of the 217 eDNA records of 47 plant taxa in the 11 lakes, 73% and 12% matched taxa recorded in vegetation surveys within 2 m and up to about 50 m away from the lakeshore, respectively, whereas 16% were not recorded in the vegetation surveys of the same lake. The latter include taxa likely overlooked in the vegetation surveys or growing outside the survey area. The percentages detected were 61, 47, 25, and 15 for dominant, common, scattered, and rare taxa, respectively. Similar numbers for aquatic plants were 88, 88, 33 and 62%, respectively. Detection rate and taxonomic resolution varied among plant families and functional groups with good detection of e.g. Ericaceae, Roseaceae, deciduous trees, ferns, club mosses and aquatics. The representation of terrestrial taxa in eDNA depends on both their distance from the sampling site and their abundance and is sufficient for recording vegetation types. For aquatic vegetation, eDNA may be comparable with, or even superior to, in-lake vegetation surveys and may therefore be used as an tool for biomonitoring. For reconstruction of terrestrial vegetation, technical improvements and more intensive sampling is needed to detect a higher proportion of rare taxa although DNA of some taxa may never reach the lake sediments due to taphonomical constrains. Nevertheless, eDNA performs similar to conventional methods of pollen and macrofossil analyses and may therefore be an important tool for reconstruction of past vegetation.
Preliminary assessment of heavy metals in water, sediment and macrophyte ( Lemna minor) collected from Anchar Lake, Kashmir, India

NASA Astrophysics Data System (ADS)

Showqi, Irfana; Lone, Farooq Ahmad; Naikoo, Mehrajuddin

2018-06-01

Water samples, sediments and free floating macrophytic plant, Lemna minor specimens were collected from five designated sites in Anchar lake (Srinagar, J&K, India) to assess its heavy metal (Cu, Cr, Zn, Ni, Cd, Pb) load and changes on seasonal basis. The concentration of heavy metals was determined using atomic absorption spectroscopy. Most of the samples were found within limits of maximum permissible concentrations as recommended by WHO (Guidelines for drinking water quality, pp 491-493, 2006). During all the seasons, highest concentration of all heavy metals (Cu, Cr, Zn, Ni, Cd, Pb) was recorded at highly polluted sites of the lake viz. near agricultural fields (S1), near settlements (S3) and SKIMS (S4). These sites received huge agrochemical run-off from the surrounding agricultural fields, solid and liquid wastes from the nearby catchment areas and effluents from Sher-e-Kashmir Institute of Medical Sciences (SKIMS) compared to control site lake centre (S5). Furthermore, most of the metals in water and sediment were found with highest concentration during autumn (Viz., Cu-1.5 ppm; Zn-0.38 ppm; Ni-1.89 ppm; Pb-0.84 ppm in water and Cu-26.9 ppm; Zn-13.6 ppm; Pb-4.33 ppm in sediment) and summer (Viz., Cr-0.68 ppm in water and Ni-4.8 ppm; Cd-2.6 ppm; Cr-8.01 ppm in sediment) seasons. Also in Lemna minor plant highest concentration was observed during summer season (Cu-29.09 ppm; Zn-19.11 ppm; Ni-5.7 ppm; Cd-1.34 ppm; Cr-9.18 ppm and Pb-9.77 ppm). From these observations, it was found that the sources of heavy metals in Anchar lake were both natural and anthropogenic ones. This study recommended that continuous monitoring of heavy metals (Viz; Cu, Cr, Zn, Ni, Cd and Pb) in water, sediment and other aquatic biota of Anchar lake should be directed to protection of ecological status of the lake and its surrounding area.
High-resolution multi-proxy reconstruction of Lake Ighiel (Western Carpathians, Romania): processes and controlling factors of lacustrine dynamics during the mid and late Holocene

NASA Astrophysics Data System (ADS)

Haliuc, Aritina; Veres, Daniel; Hubay, Katalin; Begy, Robert; Brauer, Achim; Hutchinson, Simon; Braun, Mihaly

2016-04-01

Concerns about current and prospective environmental change have increased the interest in past climate variability and its impact on the bio-hydro-atmosphere and human society. Acting as high-resolution terrestrial archives, lacustrine sediments are the result of the complex interaction between internal and external forcing and an important tool in efforts to resolve questions related to the palaeoclimatic and palaeoenvironmental conditions of the recent past. Here we discuss a new, high-resolution sedimentary record from the Romanian Carpathians (central-eastern Europe). Lake Ighiel (46° 10'50"N, 23° 22'00"E) is a small lake located in a mid-altitude mountain belt (Trascau Mountains) at an altitude of 924 m ( lake maximum depth 9 m; catchment area 487 ha). We employ detailed 210Pb and 14C dating coupled with high-resolution X-ray fluorescence scanning (μ-XRF) measurements, long-core sedimentary logging, environmental magnetic proxies (susceptibility, natural and induced remanences) in an attempt to trace the 6000 years evolution of lake-catchment system. More specifically, we discuss: i) the temporal evolution of the main sedimentation phases of the lake based on sedimentological, geochemical and magnetic proxies; ii) the amplitude and interplay of processes (natural and/or anthropogenic) controlling the depositional environment through time; iii) assess the contribution of each controlling factors and reconstruct the evolution of lacustrine system and palaeoclimate forcing using multivariate statistics. The sedimentary record can be divided into six phases based on alternating high and low detrital fluxes, oscillating lacustrine productivity and redox conditions. A series of detrital events (5200; 4800; 5400; 5250; 4500; 4050; 3800; 3500; 3250; 3050; 2650; 2350; 2250; 1400; 1100; 500; 100 cal yr BP) were identified by microfacies analyses and X-ray fluorescence scanning (μ-XRF) analysis. These events are reflected in most of the parameters and appear synchronous with climatically induced forcing such as increased regional precipitation and decreased total solar radiation. These changes are superimposed on clear anthropogenic derived contributions reflecting natural and mineral resource exploitation during the early metal ages, the Roman and Medieval periods, as well as during the recent period. The comparison of the our proxies with similarly resolved records from central-eastern Europe highlight the potential of Lake Ighiel as a record of palaeoclimatic and palaeohydrological conditions in a region still lacking high-resolution multi-proxy palaeoenvironmental archives. The authors acknowledge financial support from project PN-II-ID-PCE-2012-4-0530 "Millennial-scale geochemical records of anthropogenic impact and natural climate change in the Romanian Carpathians", contract nr. 15/02.09.2013.
Comparison of Multi-Scale Digital Elevation Models for Defining Waterways and Catchments Over Large Areas

NASA Astrophysics Data System (ADS)

Harris, B.; McDougall, K.; Barry, M.

2012-07-01

Digital Elevation Models (DEMs) allow for the efficient and consistent creation of waterways and catchment boundaries over large areas. Studies of waterway delineation from DEMs are usually undertaken over small or single catchment areas due to the nature of the problems being investigated. Improvements in Geographic Information Systems (GIS) techniques, software, hardware and data allow for analysis of larger data sets and also facilitate a consistent tool for the creation and analysis of waterways over extensive areas. However, rarely are they developed over large regional areas because of the lack of available raw data sets and the amount of work required to create the underlying DEMs. This paper examines definition of waterways and catchments over an area of approximately 25,000 km2 to establish the optimal DEM scale required for waterway delineation over large regional projects. The comparative study analysed multi-scale DEMs over two test areas (Wivenhoe catchment, 543 km2 and a detailed 13 km2 within the Wivenhoe catchment) including various data types, scales, quality, and variable catchment input parameters. Historic and available DEM data was compared to high resolution Lidar based DEMs to assess variations in the formation of stream networks. The results identified that, particularly in areas of high elevation change, DEMs at 20 m cell size created from broad scale 1:25,000 data (combined with more detailed data or manual delineation in flat areas) are adequate for the creation of waterways and catchments at a regional scale.
Estimation of Net Groundwater Recharge Using Natural Drawdown Events in Subtropical Isolated Wetland Ecosystems

NASA Astrophysics Data System (ADS)

Perkins, D. B.; Min, J.; Jawitz, J. W.

2008-12-01

Restoration of ditched and drained wetlands in the Lake Okeechobee basin, Florida, USA is currently under study for possible amelioration of anthropogenic phosphorus enrichment of the lake. To date most research in this area has focused on the biogeochemical role of these wetlands. Here we focus on the dynamic hydrology of these systems and the resulting control on biogeochemical cycling. Four depressional wetlands in the basin were monitored for approximately three years to understand the interaction between wetland surface water and adjacent upland groundwater system. A coupled hydrologic-biogeochemical model was created to evaluate restoration scenarios. Determining wetland-scale hydraulic conductivity was an important aspect of the hydrologic model. Based on natural drawdown events observed at wetland-upland well pairs, hydraulic conductivities of top sandy soil layers surrounding the isolated wetlands were calculated using the Dupuit equation under a constrained water budget framework. The drawdown-based hydraulic conductivity estimates of 1.1 to 18.7 m/d (geometric mean of 4.8 m/d) were about three times greater than slug test- based values (1.5 ± 1.1 m/d), which is consistent with scale-dependent expectations. Model-based net groundwater recharge rate at each depressional wetland was predicted based on the estimated hydraulic conductivities, which corresponded to 50 to 72% of rainfall in the same period. These variances appeared to be due to the relative difference of ditch bottom elevation controlling the surface runoff as well as the spatial heterogeneity of the sandy aquifer. Results from this study have implications for nutrient loads to Lake Okeechobee via groundwater as well as water quality monitoring and management strategies aimed to reduce solute export (especially P) from the upstream catchment area to Lake Okeechobee.
Stream chemistry modeling of two watersheds in the Front Range, Colorado

USGS Publications Warehouse

Meixner, Thomas; Bales, Roger C.; Williams, Mark W.; Campbell, Donald H.; Baron, Jill S.

2000-01-01

We investigated the hydrologic, geochemical, and biogeochemical controls on stream chemical composition on the Green Lakes Valley and Andrews Creek watersheds using the alpine hydrochemical model (AHM). Both sites had comparable data sets from 1994 and 1996, including high‐resolution spatial data and high‐frequency time series of hydrology, geochemistry, and meteorology. The model of each watershed consisted of three terrestrial subunits (soil, talus, and rock), with the routing between the subunits determined by spatial land cover data. Using 1994 data for model calibration and 1996 data for evaluation, AHM captured the dominant processes and successfully simulated daily stream chemical composition on both watersheds. These results confirm our procedure of using spatial and site‐specific field and laboratory data to generate an initial catchment model and then calibrating the model to calculate effective parameters for unmeasured processes. A net source of nitrogen was identified in the Andrews Creek watershed during the spring snowmelt period, whereas nitrogen was immobilized in the Green Lakes Valley. This difference was most likely due to the larger and more dominant area of talus in the Andrews Creek watershed. Our results also indicate that routing of snowmelt through either soil or talus material is sufficient for retention of H+ and release of base cations but that N retention is more important on areas mapped as soil. Owing to the larger ionic pulse and larger fraction of surface runoff the Green Lakes Valley was more sensitive to a doubling of wet deposition chemistry than the Andrews Creek watershed.
Selenium stable isotope investigation into selenium biogeochemical cycling in a lacustrine environment: Sweitzer Lake, Colorado.

PubMed

Clark, Scott K; Johnson, Thomas M

2010-01-01

We present a comprehensive set of Se concentration and isotope ratio data collected over a 3-yr period from dissolved, sediment-hosted, and organically bound Se in a Se-contaminated lake and littoral wetland. Median isotope ratios of these various pools of Se spanned a narrow isotopic range (delta80/76Se(SRM-3149)) = 1.14-2.40 per thousand). Selenium (VI) reduction in the sediments is an important process in this system, but its isotopic impact is muted by the lack of direct contact between surface waters and reduction sites within sediments. This indicates that using Se isotope data as an indicator of microbial or abiotic Se oxyanion reduction is not effective in this or other similar systems. Isotopic data suggest that most Se(IV) in the lake originates from oxidation of organically bound Se rather than directly through Se(VI) reduction. Mobilization of Se(VI) from bedrock involves only a slight isotopic shift. Temporally constant isotopic differences observed in Se(VI) from two catchment areas suggest the potential for tracing Se(VI) from different source areas. Phytoplankton isotope ratios are close to those of the water, with a small depletion in heavy isotopes (0.56 per thousand). Fish tissues nearly match the phytoplankton, being only slightly depleted in the heavier isotopes. This suggests the potential for Se isotopes as migration indicators. Volatile, presumably methylated Se was isotopically very close to median values for phytoplankton and macrophytes, indicating a lack of isotopic fractionation during methylation.
How do blockings relate to heavy precipitation events in Europe?

NASA Astrophysics Data System (ADS)

Lenggenhager, Sina; Romppainen, Olivia; Brönnimann, Stefan; Croci-Maspoli, Mischa

2017-04-01

Atmospheric blockings are quasi-stationary high pressure systems that persist for several days. Due to their longevity, blockings can be key features for extreme weather events. While several studies have shown their relevant role for temperatures extremes, the link between blockings and extreme precipitation and floods is still poorly understood. A case study of a Swiss lake flood event in the year 2000 reveals how different processes connected to blockings can favour the development of a flood. First upstream blocks helped to form strongly elongated troughs that are known to be associated with heavy precipitation events south of the Alps. Second recurrent precipitation events upstream of a block led to a moistening of the catchment and an increase of the lake level. Third the progression of the upstream weather systems was slowed and thereby the precipitation period over a catchment prolonged. Additionally, cloud diabatic processes in the flood region contributed to the establishment and maintenance of blocking anticyclones. Based on this case study we extend our analysis to all of Europe. Focusing on flood relevant precipitation events, i.e. extreme precipitation events that last for several days and affect larger areas, we show that different regions in Europe have very distinct seasonal precipitation patterns. Hence there is a strong seasonality in the occurrence of extreme events, depending on the geographical region. We further suggest that for different precipitation regimes, the preferred location of blockings varies strongly. Heavy precipitation events in southern France, for example, are often observed during Scandinavian blockings, while heavy precipitation events in south-eastern Europe coincide more often with eastern North-Atlantic blockings.

Adequacy of TRMM satellite rainfall data in driving the SWAT modeling of Tiaoxi catchment (Taihu lake basin, China)

NASA Astrophysics Data System (ADS)

Li, Dan; Christakos, George; Ding, Xinxin; Wu, Jiaping

2018-01-01

Spatial rainfall data is an essential input to Distributed Hydrological Models (DHM), and a significant contributor to hydrological model uncertainty. Model uncertainty is higher when rain gauges are sparse, as is often the case in practice. Currently, satellite-based precipitation products increasingly provide an alternative means to ground-based rainfall estimates, in which case a rigorous product assessment is required before implementation. Accordingly, the twofold objective of this work paper was the real-world assessment of both (a) the Tropical Rainfall Measuring Mission (TRMM) rainfall product using gauge data, and (b) the TRMM product's role in forcing data for hydrologic simulations in the area of the Tiaoxi catchment (Taihu lake basin, China). The TRMM rainfall products used in this study are the Version-7 real-time 3B42RT and the post-real-time 3B42. It was found that the TRMM rainfall data showed a superior performance at the monthly and annual scales, fitting well with surface observation-based frequency rainfall distributions. The Nash-Sutcliffe Coefficient of Efficiency (NSCE) and the relative bias ratio (BIAS) were used to evaluate hydrologic model performance. The satisfactory performance of the monthly runoff simulations in the Tiaoxi study supports the view that the implementation of real-time 3B42RT allows considerable room for improvement. At the same time, post-real-time 3B42 can be a valuable tool of hydrologic modeling, water balance analysis, and basin water resource management, especially in developing countries or at remote locations in which rainfall gauges are scarce.
A comparative analysis of the distribution, composition and geochemistry of surface sediments in the Linthipe and Songwe River Deltas of Lake Malawi

NASA Astrophysics Data System (ADS)

Dolozi, Michael B.; Kalindekafe, Leonard S. N.; Ngongondo, Cosmo; Dulanya, Zuze

2011-05-01

The Linthipe and Songwe River Deltas are found to the extreme southern and northern parts of Lake Malawi respectively within the East African Rift System. They occur in contrasting tectonic and climatic settings of the rift-valley half-graben structure. The sub-aqueous part of the Songwe Delta consists of relatively finer grained sediments than the Linthipe but is relatively poorly sorted. The composition of sediments within the Songwe Delta shows significant amounts of sedimentary and volcanic lithic fragments which are lacking in the Linthipe. On the other hand, ferromanganese nodules were recovered in the Linthipe Delta at water depths of 80-100 m but were not recovered in Songwe Delta at similar water depths. The finer grained facies of the Songwe Delta suggests a more prograded delta than the Linthipe. However, its poorly sorted sediments are most likely due to the heterogeneous geology of the source area; higher and faster depositional rates due to climatic influences. The lack of Ferromangenese nodules in the Songwe Delta is probably due to the sand-mud facies boundary which occurs at shallower depth. The higher proportion of Total Organic Carbon (TOC) in higher the Linthipe Delta is probably related to high rates of environmental degradation such as deforestation and agricultural activities in the riparian catchment basin. This is in contrast to the Songwe catchment basin where the levels of anthropogenic disturbance are less and climate, geomorphology and the heterogenous character of the source rocks seems to play a major role in the sedimentation processes.
Flash Floods Simulation Using a Physical based hydrological Model at the Eastern Nile Basin: Case studies; Wadi Assiut, Egypt and Wadi Gumara, Lake Tana, Ethiopia.

NASA Astrophysics Data System (ADS)

Saber, M.; Sefelnasr, A.; Yilmaz, K. K.

2015-12-01

Flash flood is a natural hydrological phenomenon which affects many regions of the world. The behavior and effect of this phenomenon is different from one region to the other regions depending on several issues such as climatology and hydrological and topographical conditions at the target regions. Wadi assiut, Egypt as arid environment, and Gumara catchment, Lake Tana, Ethiopia, as humid conditions have been selected for application. The main target of this work is to simulate flash floods at both catchments considering the difference between them on the flash flood behaviors based on the variability of both of them. In order to simulate the flash floods, remote sensing data and a physical-based distributed hydrological model, Hydro-BEAM-WaS (Hydrological River Basin Environmental Assessment Model incorporating Wadi System) have been integrated used in this work. Based on the simulation results of flash floods in these regions, it was found that the time to reach the maximum peak is very short and consequently the warning time is very short as well. It was found that the flash floods starts from zero flow in arid environment, but on the contrary in humid arid, it starts from Base flow which is changeable based on the simulated events. Distribution maps of flash floods showing the vulnerable regions of these selected areas have been developed. Consequently, some mitigation strategies relying on this study have been introduced. The proposed methodology can be applied effectively for flash flood forecasting at different climate regions, however the paucity of observational data.
Runoff and Solute Mobilisation in a Semi-arid Headwater Catchment

NASA Astrophysics Data System (ADS)

Hughes, J. D.; Khan, S.; Crosbie, R.; Helliwell, S.; Michalk, D.

2006-12-01

Runoff and solute transport processes contributing to stream flow were determined in a small headwater catchment in the eastern Murray-Darling Basin of Australia using hydrometric and tracer methods. Stream flow and electrical conductivity were monitored from two gauges draining a portion of upper catchment area (UCA), and a saline scalded area respectively. Results show that the bulk of catchment solute export, occurs via a small saline scald (< 2% of catchment area) where solutes are concentrated in the near surface zone (0-40 cm). Non-scalded areas of the catchment are likely to provide the bulk of catchment runoff, although the scalded area is a higher contributor on an areal basis. Runoff from the non-scalded area is about two orders of magnitude lower in electrical conductivity than the scalded area. This study shows that the scalded zone and non-scalded parts of the catchment can be managed separately since they are effectively de-coupled except over long time scales, and produce runoff of contrasting quality. Such differences are "averaged out" by investigations that operate at larger scales, illustrating that observations need to be conducted at a range of scales. EMMA modelling using six solutes shows that "event" or "new" water dominated the stream hydrograph from the scald. This information together with hydrometric data and soil physical properties indicate that saturated overland flow is the main form of runoff generation in both the scalded area and the UCA. Saturated areas make up a small proportion of the catchment, but are responsible for production of all run off in conditions experienced throughout the experimental period. The process of saturation and runoff bears some similarities to the VSA concept (Hewlett and Hibbert 1967).
A Digital Hydrologic Network Supporting NAWQA MRB SPARROW Modeling--MRB_E2RF1WS

USGS Publications Warehouse

Brakebill, J.W.; Terziotti, S.E.

2011-01-01

A digital hydrologic network was developed to support SPAtially Referenced Regression on Watershed attributes (SPARROW) models within selected regions of the United States. These regions correspond with the U.S. Geological Survey's National Water Quality Assessment (NAWQA) Program Major River Basin (MRB) study units 2, 3, 4, 5, and 7 (Preston and others, 2009). MRB2, covers the South Atlantic-Gulf and Tennessee River basins. MRB3, covers the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy River basins. MRB4, covers the Missouri River basins. MRB5, covers the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf River basins. MRB7, covers the Pacific Northwest River basins. The digital hydrologic network described here represents surface-water pathways (MRB_E2RF1) and associated catchments (MRB_E2RF1WS). It serves as the fundamental framework to spatially reference and summarize explanatory information supporting nutrient SPARROW models (Brakebill and others, 2011; Wieczorek and LaMotte, 2011). The principal geospatial dataset used to support this regional effort was based on an enhanced version of a 1:500,000 scale digital stream-reach network (ERF1_2) (Nolan et al., 2002). Enhancements included associating over 3,500 water-quality monitoring sites to the reach network, improving physical locations of stream reaches at or near monitoring locations, and generating drainage catchments based on 100m elevation data. A unique number (MRB_ID) identifies each reach as a single unit. This unique number is also shared by the catchment area drained by the reach, thus spatially linking the hydrologically connected streams and the respective drainage area characteristics. In addition, other relevant physical, environmental, and monitoring information can be associated to the common network and accessed using the unique identification number.
A Digital Hydrologic Network Supporting NAWQA MRB SPARROW Modeling--MRB_E2RF1

USGS Publications Warehouse

Brakebill, J.W.; Terziotti, S.E.

2011-01-01

A digital hydrologic network was developed to support SPAtially Referenced Regression on Watershed attributes (SPARROW) models within selected regions of the United States. These regions correspond with the U.S. Geological Survey's National Water Quality Assessment (NAWQA) Program Major River Basin (MRB) study units 2, 3, 4, 5, and 7 (Preston and others, 2009). MRB2, covers the South Atlantic-Gulf and Tennessee River basins. MRB3, covers the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy River basins. MRB4, covers the Missouri River basins. MRB5, covers the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf River basins. MRB7, covers the Pacific Northwest River basins. The digital hydrologic network described here represents surface-water pathways (MRB_E2RF1) and associated catchments (MRB_E2RF1WS). It serves as the fundamental framework to spatially reference and summarize explanatory information supporting nutrient SPARROW models (Brakebill and others, 2011; Wieczorek and LaMotte, 2011). The principal geospatial dataset used to support this regional effort was based on an enhanced version of a 1:500,000 scale digital stream-reach network (ERF1_2) (Nolan et al., 2002). Enhancements included associating over 3,500 water-quality monitoring sites to the reach network, improving physical locations of stream reaches at or near monitoring locations, and generating drainage catchments based on 100m elevation data. A unique number (MRB_ID) identifies each reach as a single unit. This unique number is also shared by the catchment area drained by the reach, thus spatially linking the hydrologically connected streams and the respective drainage area characteristics. In addition, other relevant physical, environmental, and monitoring information can be associated to the common network and accessed using the unique identification number.
Multi-proxy evidence for climate-driven changes in arctic lakes from northern Russia over the Holocene.

NASA Astrophysics Data System (ADS)

Self, Angela; Brooks, Stephen; Jones, Vivienne; Solovieva, Nadia; McGowan, Suzanne; Rosén, Peter; Parrott, Emily; Seppä, Heikki; Salonen, Sakari

2010-05-01

Average arctic temperatures have increased at almost twice the rate of the rest of the world over the last 100 years and climate projections suggest this trend is likely to continue resulting in an additional warming of 2 - 3°C in annual mean air temperatures by 2050. Freshwater ecosystems occupy a substantial area of the terrestrial environment in the Arctic and are particularly sensitive to temperature increases which may lead to profound changes in catchment characteristics, permafrost, hydrology and nutrient availability. Therefore it is important to understand how past changes in climate have affected these ecosystems. In this paper we present one of the first quantitative multi-proxy climate records from arctic Siberia. The affect of early - mid Holocene and recent climate change on arctic lakes in northern Russia were investigated in multi-proxy studies. The past climate was reconstructed using chironomid inference models to estimate mean July air temperatures and trends in continentality. Stable isotopes and LOI were analysed to infer past changes in sediment organic matter. Near-infrared spectroscopy (NIRS) and/or diatoms were used to infer changes in lake water total organic carbon and algal pigments and/or diatoms were used to infer changes in productivity and light penetration in the lake. Analyses of a sediment core from a tundra lake (Lake Kharinei) in north-eastern European Russia show significant assemblage changes in diatoms, chironomids and pigments, which coincide with climate-driven vegetation shifts from open birch forest to spruce forest and then to tundra over the Holocene. During the open birch phase of the late Glacial - early Holocene, chironomid-inferred reconstructions suggest that the climate was approximately 1 - 3°C warmer and more continental than present. Isotopic analyses indicate a productive environment receiving a significant input of organic material from terrestrial plants into the lake. Both diatoms and NIRS-TOC also suggest that the lake water was relatively high in TOC. Spruce forest became established within the catchment during the early - mid Holocene, which appears to have stimulated algal production. Throughout this period July air temperatures are inferred to have gradually declined to present-day values and the climate became more maritime. From ca. 4000 cal yrs BP July air temperatures remained stable but continentality increased leading to a shorter ice-free period. The pollen and macrofossil record indicates a transition to tundra vegetation ca 3000 cal yr BP which coincides with major changes in pigments, chironomids and diatoms. High resolution reconstruction of climate variability over the last 200 years from two tundra lakes on the Putoran Plateau, western Siberia, suggest that mean July air temperatures warmed by approximately 0.5°C between ca 1820 - 1980 and have remained relatively stable over the last 30 years. However major compositional changes in the chironomid and diatom assemblages have occurred within the last 125 - 50 years. Since the 1970s increases in the instrumental June temperature record and a chironomid-inferred shift to a more maritime climate have been accompanied by increases in diatom accumulation rates together with an increase in within-lake productivity and a trend towards increased algal productivity (as highlighted by stable isotope analysis). The synchronicity of the changes suggests the biota may be responding to lengthening of the ice-free period and related limnological changes. The changes in these Russian lakes corroborate results from Europe and Arctic Canada and indicate a circumpolar pattern of climate-driven regime change in arctic lakes in the last 100 years.
Adaptations of a physical-based hydrological model for alpine catchments. Application to the upper Durance catchment.

NASA Astrophysics Data System (ADS)

Lafaysse, Matthieu; Hingray, Benoit

2010-05-01

The impact of global change on water resources is expected to be especially pronounced in mountainous areas. Future hydrological scenarios required for impact studies are classically simulated with hydrological models from future meteorological scenarios based on GCMs outputs. Future hydrological regimes of French rivers were estimated following this methodology by Boé et al. (2009) with the physical-based hydrological model SAFRAN-ISBA-MODCOU (SIM), developed by Météo-France. Scenarios obtained for the Alps seem however not very reliable due to the poor performance achieved by the model for the present climate over this region. This work presents possible improvements of SIM for a more relevant simulation of alpine catchments hydrological behavior. Results obtained for the upper Durance catchment (3580 km2) are given for illustration. This catchment is located in Southern French Alps. Its outlet is the Serre-Ponçon lake, a large dam operated for hydropower production, with a key role for water supply in southeastern France. With altitudes ranging from 700 to 4100 meters, the catchment presents highly seasonal flows: minimum and maximum discharges are observed in winter and spring respectively due to snow accumulation and melt, low flows are sustained by glacier melt in late summer (39 km2 are covered by glaciers), major floods can be observed in fall due to large liquid precipitation amounts. Two main limitations of SIM were identified for this catchment. First the 8km-side grid discretization gives a bad representation of the spatial variability of hydrological processes induced by elevation and orientation. Then, low flows are not well represented because the model doesn't include deep storage in aquifers nor ice melt from glaciers. We modified SIM accordingly. For the first point, we applied a discretization based on topography : we divided the catchment in 9 sub-catchments and further 300 meters elevation bands. The vertical variability of meteorological inputs and vegetation cover could be thus better accounted for. Then, each elevation band is divided in 7 exposure classes, in order to represent the influence on snow cover of the solar radiation spatial variability . This discretisation results in 539 Hydrological Units where hydrological processes are assumed to be homogeneous. For the second point, we first included the possibility for glacier melt in previous discretization. We next added a conceptual non-linear underground reservoir in order to simulate water retention by aquifers. These adaptations lead to a clear improvement of simulations for all the hydrometric stations. Daily simulated discharges fit well with measurements (Nash score = 0.8). The model has a good ability to simulate interannual variability and it is robust under a long simulation period (1959-2006). This encourages us to use it in a modified climate context. We studied the effect of each model improvement with a set of sensitivity tests. Accounting for elevation bands allows simulating more persistent snow cover at high altitudes, contributing later to river flows. Adding underground storage leads to delay the snowmelt runoff transfer in river. The exposure influence is not so sensitive for discharges simulation, but it gives a more accurate description of the spatial variability of snow cover. Although glaciered areas are very small compared to total basin area, a better simulation of summer low flows is obtained including a glacier melt module. Despite previous improvements, winter low flows are still slightly underestimated. As suggested by a simple sensitivity analysis, this could be partly due to the fact that the model doesn't correctly simulate basal snowmelt by ground heat flow.
Earth Observations taken by the Expedition 27 Crew

NASA Image and Video Library

2011-04-25

ISS027-E-016922 (25 April 2011) --- River deltas and Lake Ayakum in China (Tibet) are featured in this image photographed by an Expedition 27 crew member on the International Space Station. The Tibetan Plateau contains numerous lakes that dot an otherwise arid landscape. Lake Ayakum is located near the northern boundary of the Plateau to the southeast of the Kunlun Mountains. While many of the small glacier- and snowmelt-fed streams that cross the Tibetan Plateau eventually give rise to major Southeast Asian rivers including the Mekong and Yangtze, some empty into saline lakes such as Lake Ayakum. This detailed photograph highlights two river deltas (upper left and lower right) formed along the southwestern shoreline of the lake. When sediments build up to the point that a river can no longer flow over them, it will jump to a new channel position and begin the process anew. Scientists have noted that, over geologic time, the channels tend to sweep back and forth ? similar to the motion of an automobile windshield wiper ? to form the typical semi-circular or fan shape of the delta. Gray to tan surfaces of both deltas indicate prior positions of their respective river channels; the uniform coloration and smooth texture suggest that they are relatively old and are now inactive. In contrast, the younger and currently active delta surfaces can be recognized by reddish-brown sediment and clearly visible river channels. Lateral channel migration is particularly evident in the approximately eight-kilometer-wide active delta area at upper left. The reddish coloration of the actively depositing sediment may indicate a change from the sources that formed the older parts of the deltas (or indicate weathering and soil formation on the older deposits), or an episodic input of dust or other material to the river catchments.
How does precipitation become runoff? Comparison of hydrologic thresholds across hillslope and catchment scales

NASA Astrophysics Data System (ADS)

Ross, C.; Ali, G.; Oswald, C. J.; McMillan, H. K.; Walter, K.

2017-12-01

A hydrologic threshold is a critical point in time when runoff behavior rapidly changes, often in response to the activation of specific storage-driven or intensity-driven processes. Hydrologic thresholds can be viewed as characteristic signatures of hydrosystems, which makes them useful for site comparison as long as their presence (or lack thereof) can be evaluated in a standard manner across a range of environments. While several previous studies have successfully identified thresholds at a variety of individual sites, only a limited number have compared dynamics prevailing at the hillslope versus catchment scale, or distinguished the role of storage versus intensity thresholds. The objective of this study was therefore to examine precipitation input thresholds as well as "precipitation minus evapotranspiration" thresholds in environments with contrasted climatic and geographic characteristics. Historical climate and hydrometric datasets were consolidated for one hillslope site located at the Panola Mountain Research Watershed (Southeastern USA) and catchments located in the HJ Andrew's Experimental Forest (Northwestern USA), the Catfish Creek Watershed (Canadian prairies), the Experimental Lakes Area (Canadian boreal ecozone), the Tarrawarra catchment (Australia) and the Mahurangi catchment (New Zealand). Individual precipitation-runoff events were delineated using the newly introduced software HydRun to derive event-specific hydrograph parameters as well surrogate measures of antecedent moisture conditions and evapotranspiration in an automated and consistent manner. Various hydrograph parameters were then plotted against those surrogate measures to detect and evaluate site-specific threshold dynamics. Preliminary results show that a range of threshold shapes (e.g., "hockey stick", heaviside and dirac) were observed across sites. The influence of antecedent precipitation on threshold magnitude and shape also appeared stronger at sites with lower topographic relief and drier climate. Future analyses will focus on the interaction between storage and intensity thresholds in order to evaluate the importance of considering both for comparative hydrological studies.
Geomorphic responses of lower Bega River to catchment disturbance, 1851?1926

NASA Astrophysics Data System (ADS)

Brooks, Andrew P.; Brierley, Gary J.

1997-03-01

Prior to significant European settlement of the area in the 1850s, lower Bega River on the South Coast of NSW had a narrow, relatively deep channel lined by river oaks. The river had a suspended or mixed load, with platypus habitat available in pools. Banks were fine-grained and relatively cohesive (silts and clays), as was the floodplain, which graded to a series of valley-marginal swamps and lakes. Extensive evidence from maps and portion plans, archival photographs, bridge surveys, and anecdotal sources, complemented by field analysis of floodplain sedimentology (including radiocarbon-dated samples) and vegetation remnants are used to document the dramatic metamorphosis in the character and behaviour of lower Bega River in the latter half of the nineteenth century. By 1926 the channel had widened extensively (up to 340%) and shallowed in association with bed aggradation by coarse sandy bedload. Floodplain accretion was dominated by fine to medium sands, with some coarse sand splays. In contrast with most other studies of channel metamorphosis in Australia, which have emphasised river responses to climatically-induced flood histories, relegating human impacts to a secondary role, the profound changes to the geomorphic condition and behaviour of Bega River reflect indirect human disturbance of Bega catchment, and direct but non point source disturbance to the channel. Extensive clearance of catchment, floodplain, and channel-marginal vegetation occurred within a few decades of European settlement, altering the hydrologic and sediment regime of the river, and transforming the geomorphic effectiveness of floods. Although this study is situated in a relatively sensitive, granitic catchment, catchment clearance is likely to have induced equally significant responses in many other river systems in eastern Australia. In some instances the diffuse aspects of human disturbance on landscapes induce impacts on river character that are just as profound as major direct disturbances of river channels. This may have profound implications in understanding, and hence managing, the geomorphic consequences of river behaviour in Australia and elsewhere.
USE OF WATERSHED CLASSIFICATION IN MONITORING FRAMEWORKS FOR THE WESTERN LAKE SUPERIOR BASIS

EPA Science Inventory

In this case study we predicted stream sensitivity to nonpoint source pollution based on the nonlinear responses of hydrologic regimes and associated loadings of nonpoint source pollutants to catchment properties. We assessed two hydrologically-based thresholds of impairment, on...
Relict rock glaciers in alpine catchments: A regional study in Central Austria

NASA Astrophysics Data System (ADS)

Kellerer-Pirklbauer, Andreas; Pauritsch, Marcus; Winkler, Gerfried

2013-04-01

Alpine catchments represent an important freshwater source in many regions. Catchments in the subalpine to nival altitudinal levels are generally characterised by higher precipitation, lower evapotranspiration and consequently higher discharge rates compared to lower elevated areas of the montane and foothill levels of the same region. Particularly in crystalline mountain regions in the mid- to high latitudes glacial and periglacial sediments cover larger areas and form important aquifers in alpine catchments. Typical periglacial landforms in mountain areas are rock glaciers. Relict rock glaciers consist of sediment accumulations without permafrost at present. This rock glacier type has a strong influence on water storage capacities and discharge behaviour of the catchments. The hydraulic properties of rock glaciers have a positive impact on flood-risk reduction and the riparian ecology below rock glacier springs during dry periods. Furthermore, the exceptional high discharge rates at springs at the front of relict rock glaciers compared to nearby non-rock glacier springs are also of economic interest. Knowledge about morphometric characteristics of rock glacier catchments helps to increase the understanding of the groundwater system and discharge dynamics of rock glaciers. In this context the main objectives of our study are (a) to assess and quantitatively describe rock glacier catchments at a regional scale by analysing different morphometric parameters of the catchments and (b) to combine the rock glacier catchment properties with water balance data. In doing so, at first an inventory of 295 rock glacier catchments was established for the 2440 km² large study area (Niedere Tauern Range, Styria) in Central Austria ranging from 590 to 2862 m a.s.l.. In a second step, the inventory data were combined with area-wide precipitation, discharge and evapotranspiration data. Results reveal that 108 km² or 4.4% of the entire study area belongs to rock glacier catchments. This proportion increases to 8.6% for areas above 1500 m a.s.l. and even to 23% for areas above 2000 m a.s.l.. Results for a 626 km² large subunit (Seckauer Tauern Range) reveal that even 15.6% of the area above 1500 m a.s.l. and more 42% above 2000 m a.s.l. are influenced by relict rock glaciers as aquifers. A total water volume of 4240 Mio m³ is precipitated annually (mean value for the normal period 1971-2000) in the entire study area. 22% of this water is evapotranspirated and the remaining water is the discharge of the catchments. Despite the fact that 8.6% of the entire Niedere Tauern Range above 1500 m a.s.l. belong to rock glacier catchments, about 9.5% of the total discharge and 9.2% of the total precipitation originates in the rock glacier catchments. In contrast, only 7.9% of all precipitated water is evapotranspirated in these catchments. In the subunit Seckauer Tauern Range the same figures for rock glacier catchments are substantially higher and more pronounced in their differences with 15.6% for area, 16.8% for precipitation, 14.5% for evapotranspiration and even 17.3% for discharge. These figures exemplarily show that rock glaciers and their catchments are highly relevant in the alpine water cycle of the study area.
Modelling catchment areas for secondary care providers: a case study.

PubMed

Jones, Simon; Wardlaw, Jessica; Crouch, Susan; Carolan, Michelle

2011-09-01

Hospitals need to understand patient flows in an increasingly competitive health economy. New initiatives like Patient Choice and the Darzi Review further increase this demand. Essential to understanding patient flows are demographic and geographic profiles of health care service providers, known as 'catchment areas' and 'catchment populations'. This information helps Primary Care Trusts (PCTs) to review how their populations are accessing services, measure inequalities and commission services; likewise it assists Secondary Care Providers (SCPs) to measure and assess potential gains in market share, redesign services, evaluate admission thresholds and plan financial budgets. Unlike PCTs, SCPs do not operate within fixed geographic boundaries. Traditionally, SCPs have used administrative boundaries or arbitrary drive times to model catchment areas. Neither approach satisfactorily represents current patient flows. Furthermore, these techniques are time-consuming and can be challenging for healthcare managers to exploit. This paper presents three different approaches to define catchment areas, each more detailed than the previous method. The first approach 'First Past the Post' defines catchment areas by allocating a dominant SCP to each Census Output Area (OA). The SCP with the highest proportion of activity within each OA is considered the dominant SCP. The second approach 'Proportional Flow' allocates activity proportionally to each OA. This approach allows for cross-boundary flows to be captured in a catchment area. The third and final approach uses a gravity model to define a catchment area, which incorporates drive or travel time into the analysis. Comparing approaches helps healthcare providers to understand whether using more traditional and simplistic approaches to define catchment areas and populations achieves the same or similar results as complex mathematical modelling. This paper has demonstrated, using a case study of Manchester, that when estimating the catchment area of a planned new hospital, the extra level of detail provided by the gravity model may prove necessary. However, in virtually all other applications, the Proportional Flow method produced the optimal model for catchment populations in Manchester, based on several criteria: it produced the smallest RMS error; it addressed cross-boundary flows; the data used to create the catchment was readily available to SCPs; and it was simpler to reproduce than the gravity model method. Further work is needed to address how the Proportional Flow method can be used to reflect service redesign and handle OAs with zero or low activity. A next step should be the rolling out of the method across England and looking at further drill downs of data such as catchment by Healthcare Resource Group (HRG) rather than specialty level.
Dust inputs and bacteria influence dissolved organic matter in clear alpine lakes.

PubMed

Mladenov, N; Sommaruga, R; Morales-Baquero, R; Laurion, I; Camarero, L; Diéguez, M C; Camacho, A; Delgado, A; Torres, O; Chen, Z; Felip, M; Reche, I

2011-07-26

Remote lakes are usually unaffected by direct human influence, yet they receive inputs of atmospheric pollutants, dust, and other aerosols, both inorganic and organic. In remote, alpine lakes, these atmospheric inputs may influence the pool of dissolved organic matter, a critical constituent for the biogeochemical functioning of aquatic ecosystems. Here, to assess this influence, we evaluate factors related to aerosol deposition, climate, catchment properties, and microbial constituents in a global dataset of 86 alpine and polar lakes. We show significant latitudinal trends in dissolved organic matter quantity and quality, and uncover new evidence that this geographic pattern is influenced by dust deposition, flux of incident ultraviolet radiation, and bacterial processing. Our results suggest that changes in land use and climate that result in increasing dust flux, ultraviolet radiation, and air temperature may act to shift the optical quality of dissolved organic matter in clear, alpine lakes. © 2011 Macmillan Publishers Limited. All rights reserved.
Mechanisms underlying export of N from high-elevation catchments during seasonal transitions

USGS Publications Warehouse

Sickman, J.O.; Leydecker, A.L.; Chang, Cecily C.Y.; Kendall, C.; Melack, J.M.; Lucero, D.M.; Schimel, J.

2003-01-01

Mechanisms underlying catchment export of nitrogen (N) during seasonal transitions (i.e., winter to spring and summer to autumn) were investigated in high-elevation catchments of the Sierra Nevada using stable isotopes of nitrate and water, intensive monitoring of stream chemistry and detailed catchment N-budgets. We had four objectives: (1) determine the relative contribution of snowpack and soil nitrate to the spring nitrate pulse, (2) look for evidence of biotic control of N losses at the catchment scale, (3) examine dissolved organic nitrogen (DON) export patterns to gain a better understanding of the biological and hydrological controls on DON loss, and (4) examine the relationship between soil physico-chemical conditions and N export. At the Emerald Lake watershed, nitrogen budgets and isotopic analyses of the spring nitrate pulse indicate that 50 to 70% of the total nitrate exported during snowmelt (ca. April to July) is derived from catchment soils and talus; the remainder is snowpack nitrate. The spring nitrate pulse occurred several weeks after the start of snowmelt and was different from export patterns of less biologically labile compounds such as silica and DON suggesting that: (1) nitrate is produced and released from soils only after intense flushing has occurred and (2) a microbial N-sink is operating in catchment soils during the early stages of snowmelt. DON concentrations varied less than 20-30% during snowmelt, indicating that soil processes tightly controlled DON losses.
Geological setting of the Concordia Trench-Lake system in East Antarctica

NASA Astrophysics Data System (ADS)

Cianfarra, P.; Forieri, A.; Salvini, F.; Tabacco, I. E.; Zirizotti, A.

2009-06-01

This study presents the interpretation of radio echo-sounding (RES) data collected during the 2003 geophysical campaign of PNRA (Italian National Research Project in Antarctica), which focused on the exploration of the Concordia Trench-Lake system in East Antarctica. The data allow us to identify a new lake (ITL-28) at the southern edge of the Concordia Trench and a series of N-S trending subglacial troughs cutting through the Belgica Highlands. We have mapped the bedrock morphology at 3 km resolution, which led to an improved geographical and geomorphological characterization of the Concordia Trench, Concordia Ridge, Concordia Lake and South Hills. Improved knowledge of the Concordia Trench allowed us to model the 3-D geometry of the Concordia fault, suggesting that it played a role in governing the morpho-tectonic evolution of the bedrock in the Dome C region, and to propose a Cenozoic age for its activity. We recognize the importance of catchment basin morphology in hosting subglacial lakes, and discuss the role played by tectonics, glacial scouring and volcanism in the origin of the trench lakes, basin lakes and relief lakes, respectively.
Enhancement and management of eel fisheries affected by hydroelectric dams in New Zealand

USGS Publications Warehouse

Boubee, J.; Chisnall, B.; Watene, E.; Williams, E.; Roper, D.; Haro, A.

2003-01-01

Two freshwater anguillid eel species, Anguilla australis and A. dieffenbachia, form the basis of important traditional, recreational, and commercial fisheries in New Zealand. These fisheries have been affected by the damming of many of the major waterways for hydroelectric generation. To create fisheries in reservoirs that would be otherwise inaccessible, elvers have been transferred from the base of dams into habitats upstream. Operations in three catchments: the Patea River (Lake Rotorangi), Waikato River (eight reservoirs notably the two lowermost, lakes Karapiro and Arapuni), and Rangitaiki River (lakes Matahina and Aniwhenua) are discussed. In all reservoirs, the transfers have successfully established fishable populations within six years of the first transfers and, in Lake Arapuni eels have reached the marketable size of 220 g in less than four years. In comparison, it typically takes from 13 to 17 years before eel populations are fishable in the lower Waikato River where direct access to the sea is available. Telemetry and monitoring at the screens and tailraces of several power stations have been used to determine migration timing, triggers, and pathways of mature eels. Successful downstream transfer of mature migrating adults has been achieved by spillway opening and netting in headraces during rain events in autumn, but means of preventing eels from impinging and entraining at the intakes are still required. An integrated, catchment-wide management system will be required to ensure sustainability of the fisheries. ?? Copyright by the American Fisheries Society 2003.
Attributes for MRB_E2RF1 Catchments by Major River Basins in the Conterminous United States: NLCD 2001 Land Use and Land Cover

USGS Publications Warehouse

Wieczorek, Michael; LaMotte, Andrew E.

2010-01-01

This tabular data set represents the estimated area of land use and land cover from the National Land Cover Dataset 2001 (LaMotte, 2008), compiled for every MRB_E2RF1 catchment of the Major River Basins (MRBs, Crawford and others, 2006). The source data set represents land use and land cover for the conterminous United States for 2001. The National Land Cover Data Set for 2001 was produced through a cooperative project conducted by the Multi-Resolution Land Characteristics (MRLC) Consortium. The MRLC Consortium is a partnership of Federal agencies (http://www.mrlc.gov), consisting of the U.S. Geological Survey (USGS), the National Oceanic and Atmospheric Administration (NOAA), the U.S. Environmental Protection Agency (USEPA), the U.S. Department of Agriculture (USDA), the U.S. Forest Service (USFS), the National Park Service (NPS), the U.S. Fish and Wildlife Service (USFWS), the Bureau of Land Management (BLM), and the USDA Natural Resources Conservation Service (NRCS). The MRB_E2RF1 catchments are based on a modified version of the U.S. Environmental Protection Agency's (USEPA) ERF1_2 and include enhancements to support national and regional-scale surface-water quality modeling (Nolan and others, 2002; Brakebill and others, 2011). Data were compiled for every MRB_E2RF1 catchment for the conterminous United States covering the South Atlantic-Gulf and Tennessee (MRB2), the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy (MRB3), the Missouri (MRB4), the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf (MRB5) and the Pacific Northwest (MRB7) river basins.
Assessing the effects of rural livelihood transition on non-point source pollution: a coupled ABM-IECM model.

PubMed

Yuan, Chengcheng; Liu, Liming; Ye, Jinwei; Ren, Guoping; Zhuo, Dong; Qi, Xiaoxing

2017-05-01

Water pollution caused by anthropogenic activities and driven by changes in rural livelihood strategies in an agricultural system has received increasing attention in recent decades. To simulate the effects of rural household livelihood transition on non-point source (NPS) pollution, a model combining an agent-based model (ABM) and an improved export coefficient model (IECM) was developed. The ABM was adopted to simulate the dynamic process of household livelihood transition, and the IECM was employed to estimate the effects of household livelihood transition on NPS pollution. The coupled model was tested in a small catchment in the Dongting Lake region, China. The simulated results reveal that the transition of household livelihood strategies occurred with the changes in the prices of rice, pig, and labor. Thus, the cropping system, land-use intensity, resident population, and number of pigs changed in the small catchment from 2000 to 2014. As a result of these changes, the total nitrogen load discharged into the river initially increased from 6841.0 kg in 2000 to 8446.3 kg in 2004 and then decreased to 6063.9 kg in 2014. Results also suggest that rural living, livestock, paddy field, and precipitation alternately became the main causes of NPS pollution in the small catchment, and the midstream region of the small catchment was the primary area for NPS pollution from 2000 to 2014. Despite some limitations, the coupled model provides an innovative way to simulate the effects of rural household livelihood transition on NPS pollution with the change of socioeconomic factors, and thereby identify the key factors influencing water pollution to provide valuable suggestions on how agricultural environmental risks can be reduced through the regulation of the behaviors of farming households in the future.

Inverse Geochemical Reaction Path Modelling and the Impact of Climate Change on Hydrologic Structure in Snowmelt-Dominated Catchments in the Southwestern USA

NASA Astrophysics Data System (ADS)

Driscoll, J. M.; Meixner, T.; Molotch, N. P.; Sickman, J. O.; Williams, M. W.; McIntosh, J. C.; Brooks, P. D.

2011-12-01

Snowmelt from alpine catchments provides 70-80% of the American Southwest's water resources. Climate change threatens to alter the timing and duration of snowmelt in high elevation catchments, which may also impact the quantity and the quality of these water resources. Modelling of these systems provides a robust theoretical framework to process the information extracted from the sparse physical measurement available in these sites due to their remote locations. Mass-balance inverse geochemical models (via PHREEQC, developed by the USGS) were applied to two snowmelt-dominated catchments; Green Lake 4 (GL4) in the Rockies and Emerald Lake (EMD) in the Sierra Nevada. Both catchments primarily consist of granite and granodiorite with a similar bulk geochemistry. The inputs for the models were the initial (snowpack) and final (catchment output) hydrochemistry and a catchment-specific suite of mineral weathering reactions. Models were run for wet and dry snow years, for early and late time periods (defined hydrologically as 1/2 of the total volume for the year). Multiple model solutions were reduced to a representative suite of reactions by choosing the model solution with the fewest phases and least overall phase change. The dominant weathering reactions (those which contributed the most solutes) were plagioclase for GL4 and albite for EMD. Results for GL4 show overall more plagioclase weathering during the dry year (214.2g) than wet year (89.9g). Both wet and dry years show more weathering in the early time periods (63% and 56%, respectively). These results show that the snowpack and outlet are chemically more similar during wet years than dry years. A possible hypothesis to explain this difference is a change in contribution from subsurface storage; during the wet year the saturated catchment reduces contact with surface materials that would result in mineral weathering reactions by some combination of reduced infiltration and decreased subsurface transit time. By contrast, during the dry year infiltration and subsequent displacement of stored water that has had longer contact time with minerals and therefore has become more geochemically evolved to produce a greater difference between snowmelt and catchment outlet hydrochemistry. The results for EMD show little distinction between albite weathering for wet and dry years (55.9g and 66.0g, relatively). A hypothesis for this lack of difference in mineral phase changes may be due to less subsurface storage capacity in EMD relative to GL4. The spatial distribution of snowmelt has also been shown to influence the integrated watershed response, and future work includes using the Alpine Hydrochemical Model (AHM) to further investigate catchment response to these spatial data. The AHM will also provide further insight of surface-groundwater interactions through a more integrated model which includes hydrochemical, biological and physical processes to elucidate catchment response to changes in snowmelt dynamics.
Estimation of water storage changes in small endorheic lakes in Burabay National Nature Park (Northern Kazakhstan, Central Asia); the effect of climate change and anthropogenic influences

NASA Astrophysics Data System (ADS)

Yapiyev, Vadim; Sagintayev, Zhanay; Verhoef, Anne; Samarkhanov, Kanat; Jumassultanova, Saltanat

2017-04-01

Both climate change and anthropogenic activities contribute to deterioration of terrestrial water resources and ecosystems worldwide. It has been observed in recent decades that water-limited steppe regions of Central Asia are among ecosystems found to exhibit enhanced responses to climate variability. In fact, the largest share of worldwide net loss of permanent water extent is geographically concentrated in the Central Asia and Middle East regions attributed to both climate variability/change and human activities impacts. We used a digital elevation model, digitized bathymetry maps and high resolution Landsat images to estimate the areal water cover extent and volumetric storage changes in small terminal lakes in Burabay National Nature Park (BNNP), located in Northern Central Asia, for the period 2000-2016. Based on the analysis of long-term climatic data from meteorological stations, hydrometeorological network observations as well as regional climate model projections we evaluate the impacts of past thirty years and future climatic conditions on the water balance of BNNP lake catchments. The anthropogenic water consumption was estimated based on data collected at a local water supply company and regulation authorities. One the one hand historical in-situ observations and future climate projections do not show a significant change in precipitation in BNNP. On the other hand both observations and the model demonstrate steadily rising air temperatures in the area. It is concluded that the long-term decline in water levels for most of these lakes can be largely attributed to climate change (but only via changes in air temperature, causing evaporation to exceed precipitation) and not to direct anthropogenic influences such as increased water withdrawals. In addition, the two largest lakes, showing the highest historical water level decline, do not have sufficient water drainage basin area to sustain water levels under increased evaporation rates.
Historic carbon burial spike in an Amazon floodplain lake linked to riparian deforestation near Santarém, Brazil

NASA Astrophysics Data System (ADS)

Sanders, Luciana M.; Taffs, Kathryn; Stokes, Debra; Sanders, Christian J.; Enrich-Prast, Alex; Amora-Nogueira, Leonardo; Marotta, Humberto

2018-01-01

Forests along the Amazon Basin produce significant quantities of organic material, a portion of which is deposited in floodplain lakes. Deforestation in the watershed may then have potentially important effects on the carbon fluxes. In this study, a sediment core was extracted from an Amazon floodplain lake to examine the relationship between carbon burial and changing land cover and land use. Historical records from the 1930s and satellite data from the 1970s were used to calculate deforestation rates between 1930 to 1970 and 1970 to 2010 in four zones with different distances from the margins of the lake and its tributaries (100, 500, 1000 and 6000 m buffers). A sediment accumulation rate of ˜ 4 mm yr-1 for the previous ˜ 120 years was determined from the 240+239Pu signatures and the excess 210Pb method. The carbon burial rates ranged between 85 and 298 g C m-2 yr-1, with pulses of high carbon burial in the 1950s, originating from the forest vegetation as indicated by δ13C and δ15N signatures. Our results revealed a potentially important spatial dependence of the organic carbon (OC) burial in Amazon lacustrine sediments in relation to deforestation rates in the catchment. These deforestation rates were more intense in the riparian vegetation (100 m buffer) during the period 1930 to 1970 and the larger open water areas (500, 1000 and 6000 m buffer) during 1970 to 2010. The continued removal of vegetation from the interior of the forest was not related to the peak of OC burial in the lake, but only the riparian deforestation which peaked during the 1950s. Therefore, this supports the conservation priority of riparian forests as an important management practice for Amazon flooded areas. Our findings suggest the importance of abrupt and temporary events in which some of the biomass released by deforestation, especially restricted to areas along open water edges, might reach the depositional environments in the floodplain of the Amazon Basin.
Initial geochemistry data of the Lake Ohrid (Macedonia, Albania) "DEEP" site sediment record: The ICDP SCOPSCO drilling project

NASA Astrophysics Data System (ADS)

Francke, Alexander; Wagner, Bernd; Krastel, Sebastian; Lindhorst, Katja; Mantke, Nicole; Klinghardt, Dorothea

2014-05-01

Lake Ohrid, located at the border of Macedonia and Albania is about 30 km long, 15 km wide and up to 290 m deep. Formed within a tectonic graben, Lake Ohrid is considered to be the oldest lake in Europe. The ICDP SCOPSCO (Scientific Collaboration of Past Speciation Conditions in Lake Ohrid) deep drilling campaign at Lake Ohrid in spring 2013 aimed (a) to obtain more precise information about the age and origin of the lake, (b) to unravel the seismotectonic history of the lake area including effects of major earthquakes and associated mass wasting events, (c) to obtain a continuous record containing information on volcanic activities and climate changes in the central northern Mediterranean region, and (d) to better understand the impact of major geological/environmental events on general evolutionary patterns and shaping an extraordinary degree of endemic biodiversity as a matter of global significance. Drilling was carried out by DOSECC (Salt Lake City, USA) using the DLDS (Deep Lake Drilling System) with a hydraulic piston corer for surface sediments and rotation drilling for harder, deeper sediments. Overall, about 2,100 m of sediment were recovered from 4 drill sites. At the "DEEP" site in the center of the lake, seismic data indicated a maximum sediment fill of ca. 700 m, of which the uppermost 568 m sediment were recovered. Initial data from core catcher samples and on-site susceptibility measurements indicate that the sediment sequence covers more than 1.2 million years and provides a continuous archive of environmental and climatological variability in the area. Currently, core opening, core description, XRF and MSCL -scanning, core correlation, and sub-sampling of the sediment cores from the "DEEP" site is conducted at the University of Cologne. High-resolution geochemical data obtained from XRF-scanning imply that the sediments from the "DEEP" site are highly sensitive to climate and environmental variations in the Balkan area over the last few glacial-interglacial cycles. Interglacial periods are characterized by high Ca counts, likely associated with a high content of calcite in the sediments. Previous studies have shown that the calcite contents in sediments from Lake Ohrid are predominantly triggered by precipitation of endogenic calcite resulting from enhanced photosynthesis and higher temperatures. Moreover, high Ca counts mostly correspond to low K counts indicating reduced clastic input and a denser vegetation cover in the catchment. In contrast, high K and low Ca counts characterize glacial periods, indicating reduced precipitation of endognic calcite and enhanced deposition of clastic material. The variations in Ca and K counts mainly represent climatic variations on a glacial-interglacial timescale. Inorganic geochemistry data shall also be used to improve the age control of the "DEEP" site sequence. First findings of macroscopic tephra horizons allow a preliminary age control on the sediment succession, and peaks in K, Sr, Zr, and magnetic susceptibility might indicate the occurrence of cryptotephralayers in the sediment sequence.
High temporal resolution water chemistry information for catchment understanding and management

NASA Astrophysics Data System (ADS)

Reaney, S. M.; Deasy, C.; Ockenden, M.; Perks, M.; Quinton, J.

2013-12-01

Many rivers and lakes are currently not meeting their full ecological potential due to environmental pressures including non-point source pollution from the catchment. These pressures include sediment, nitrogen and phosphorus from agriculture and other sources. Each of these pollutants is transferred through the landscape with different hydrological processes and along different pathways. Therefore, to effectively select and spatially target mitigation actions in the landscape, an understanding of the dominant hydrological processes and dynamics which are causing the transfer of material is required. Recent advances in environmental monitoring have enabled the collection of new rich datasets with a high temporal sampling frequency. In the UK, these techniques have been implemented in the Defra Demonstration Test Catchments project and with Natural England for targeted site investigations. Measurements include weather, hydrological flows, sediment, oxygen isotopes, nitrogen and phosphorus from a combination of in-field labs, water chemistry sondes and storm samplers. The detailed time series data can then be analysed to give insights into catchment processes through the analysis of the measured process dynamics. For example, evidence of the transfer of material along surface (or pipe) flow paths can be found from the co-incident timing of the sediment and flow record, or the timing of temperature variations after a storm event can give insight into the contribution of shallow groundwater. Given this evidence of catchment hydrological dynamics it is possible to determine the probable pathways which are transferring pollutants and hence it is possible to select suitable mitigation options in the landscape to improve the river or lake. For example, evidence of a pollutant transfer occurring as shallow soil flows suggests that buffer strips would not be an effective solution since these measures intercept surface pathways. Information on catchment residence time not only gives insight into the pathway but also gives information on the likely amount of time required for an improvement in water quality to occur. Therefore, the success or failure of a scheme can be assessed at an appropriate time after the works rather than prematurely. These insights into catchment processes enable us to understand the systems in greater depth and crucially to communicate this understanding to the local stakeholders. The greater evidence of the system behaviour can then be used to prompt uptake of the mitigation features and hence lead to environmental and ecological improvements. Funding from Defra UK and Natural England, UK.
Multi-trophic resilience of boreal lake ecosystems to forest fires

USGS Publications Warehouse

Lewis, Tyler L.; Lindberg, Mark S.; Schmutz, Joel A.; Bertram, M.R.

2014-01-01

Fires are the major natural disturbance in the boreal forest, and their frequency and intensity will likely increase as the climate warms. Terrestrial nutrients released by fires may be transported to boreal lakes, stimulating increased primary productivity, which may radiate through multiple trophic levels. Using a before-after-control-impact (BACI) design, with pre- and postfire data from burned and unburned areas, we examined effects of a natural fire across several trophic levels of boreal lakes, from nutrient and chlorophyll levels, to macroinvertebrates, to waterbirds. Concentrations of total nitrogen and phosphorus were not affected by the fire. Chlorophyll levels were also unaffected, likely reflecting the stable nutrient concentrations. For aquatic invertebrates, we found that densities of three functional feeding groups did not respond to the fire (filterers, gatherers, scrapers), while two groups increased (shredders, predators). Amphipods accounted for 98% of shredder numbers, and we hypothesize that fire-mediated habitat changes may have favored their generalist feeding and habitat ecology. This increase in amphipods may, in turn, have driven increased predator densities, as amphipods were the most numerous invertebrate in our lakes and are commonly taken as prey. Finally, abundance of waterbird young, which feed primarily on aquatic invertebrates, was not affected by the fire. Overall, ecosystems of our study lakes were largely resilient to forest fires, likely due to their high initial nutrient concentrations and small catchment sizes. Moreover, this resilience spanned multiple trophic levels, a significant result for ecologically similar boreal regions, especially given the high potential for increased fires with future climate change.
Multi-trophic resilience of boreal lake ecosystems to forest fires.

PubMed

Lewis, Tyler L; Lindberg, Mark S; Schmutz, Joel A; Bertram, Mark R

2014-05-01

Fires are the major natural disturbance in the boreal forest, and their frequency and intensity will likely increase as the climate warms. Terrestrial nutrients released by fires may be transported to boreal lakes, stimulating increased primary productivity, which may radiate through multiple trophic levels. Using a before-after-control-impact (BACI) design, with pre- and postfire data from burned and unburned areas, we examined effects of a natural fire across several trophic levels of boreal lakes, from nutrient and chlorophyll levels, to macroinvertebrates, to waterbirds. Concentrations of total nitrogen and phosphorus were not affected by the fire. Chlorophyll a levels were also unaffected, likely reflecting the stable nutrient concentrations. For aquatic invertebrates, we found that densities of three functional feeding groups did not respond to the fire (filterers, gatherers, scrapers), while two groups increased (shredders, predators). Amphipods accounted for 98% of shredder numbers, and we hypothesize that fire-mediated habitat changes may have favored their generalist feeding and habitat ecology. This increase in amphipods may, in turn, have driven increased predator densities, as amphipods were the most numerous invertebrate in our lakes and are commonly taken as prey. Finally, abundance of waterbird young, which feed primarily on aquatic invertebrates, was not affected by the fire. Overall, ecosystems of our study lakes were largely resilient to forest fires, likely due to their high initial nutrient concentrations and small catchment sizes. Moreover, this resilience spanned multiple trophic levels, a significant result for ecologically similar boreal regions, especially given the high potential for increased fires with future climate change.
Paleo-hydrological changes in the Chew Bahir area during the past 50 ka inferred from isotope signatures in aquatic microfossils

NASA Astrophysics Data System (ADS)

Junginger, Annett

2017-04-01

A major challenge in paleo-anthropology is to understand the impact of climatic changes on human evolution. The Hominin Sites and Paleo-lakes Drilling Project (HSPDP) is currently meeting that challenge by providing records that cover the last 3.7 Ma of paleoenvironmental change all located in close proximity to key paleo-anthropological findings in East Africa. One of the cored climatic archives comes from the Chew Bahir basin in southern Ethiopia, where duplicate sediment cores provide valuable insights about East African environmental variability during the last 550 ka. The lake basins in the eastern branch of the East African Rift System today contain mainly shallow and alkaline lakes. However, paleo-shorelines in the form of wave cut notches, shell beds, and beach ridges are common morphological evidences for deep freshwater lakes that have filled the basins up to their overflow level during pronounced humid episodes, such as the African Humid Period (15-5 ka). Unfortunately, further back in time, many of those morphological features disappear due to erosion and the estimation of paleo-water depths depend merely on qualitative proxies from core analyses. We here present a method that shows high potential to translate qualitative proxy signals from sediment core analyses to quantitative climate signals in the Ethiopian Rift. The method aims at water level reconstruction in the Chew Bahir basin using strontium isotope ratios (87Sr/86Sr, SIR) in lacustrine microfossils. SIR reflect the lithology of the drained catchment. SIR have changed pronouncedly when higher elevated paleo-lakes Abaya, Chamo and Awassa were overflowing into paleo-lake Chew Bahir. This new method may help to quantify paleo-lake levels beyond the past 20 ka and may also detect migrational barriers or routes due to the occurrence of synchronous large, connected and deep paleo-lakes.
Alpine glacier-fed turbid lakes are discontinuous cold polymictic rather than dimictic

PubMed Central

Peter, Hannes; Sommaruga, Ruben

2017-01-01

Abstract Glacier retreat as a consequence of climate change influences freshwater ecosystems in manifold ways, yet the physical and chemical bases of these effects are poorly studied. Here, we characterize how water temperature differs between alpine lakes with and without direct glacier influence on seasonal and diurnal timescales. Using high temporal resolution monitoring of temperature in 4 lakes located in a catchment influenced by glacier retreat, we reported unexpectedly high surface temperatures, even in proglacial lakes located 2600 m a.s.l. Cold glacier meltwater and low nighttime air temperatures caused a distinct diurnal pattern of water temperature in the water column of glacier-influenced lakes. Precipitation onto glacier surfaces apparently leads to rapid cooling of the glacier-fed lakes and disrupts the thermal stratification with several mixing events during the summer. Taken together, these mechanisms contribute to the unique seasonal and diurnal dynamics of glacier-influenced lakes that contrast with the typical dimictic pattern of clear alpine lakes and represent an example of discontinuous cold polymictic lake type. This work contributes to the basic description of how climate and meteorology affect the physical properties of an increasingly common lake type. PMID:28690780
Characterization of surface and ground water δ18O seasonal variation and its use for estimating groundwater residence times

USGS Publications Warehouse

Reddy, Michael M.; Schuster, Paul; Kendall, Carol; Reddy, Micaela B.

2006-01-01

18O is an ideal tracer for characterizing hydrological processes because it can be reliably measured in several watershed hydrological compartments. Here, we present multiyear isotopic data, i.e. 18O variations (δ18O), for precipitation inputs, surface water and groundwater in the Shingobee River Headwaters Area (SRHA), a well-instrumented research catchment in north-central Minnesota. SRHA surface waters exhibit δ18O seasonal variations similar to those of groundwaters, and seasonal δ18O variations plotted versus time fit seasonal sine functions. These seasonal δ18O variations were interpreted to estimate surface water and groundwater mean residence times (MRTs) at sampling locations near topographically closed-basin lakes. MRT variations of about 1 to 16 years have been estimated over an area covering about 9 km2 from the basin boundary to the most downgradient well. Estimated MRT error (±0·3 to ±0·7 years) is small for short MRTs and is much larger (±10 years) for a well with an MRT (16 years) near the limit of the method. Groundwater transit time estimates based on Darcy's law, tritium content, and the seasonal δ18O amplitude approach appear to be consistent within the limits of each method. The results from this study suggest that use of the δ18O seasonal variation method to determine MRTs can help assess groundwater recharge areas in small headwaters catchments.
Characterization of surface and ground water δ18O seasonal variation and its use for estimating groundwater residence times

USGS Publications Warehouse

Reddy, Michael M.; Schuster, Paul F.; Kendall, Carol; Reddy, Micaela B.

2006-01-01

18O is an ideal tracer for characterizing hydrological processes because it can be reliably measured in several watershed hydrological compartments. Here, we present multiyear isotopic data, i.e. 18O variations (δ18O), for precipitation inputs, surface water and groundwater in the Shingobee River Headwaters Area (SRHA), a well-instrumented research catchment in north-central Minnesota. SRHA surface waters exhibit δ18O seasonal variations similar to those of groundwaters, and seasonal δ18O variations plotted versus time fit seasonal sine functions. These seasonal δ18O variations were interpreted to estimate surface water and groundwater mean residence times (MRTs) at sampling locations near topographically closed-basin lakes. MRT variations of about 1 to 16 years have been estimated over an area covering about 9 km2 from the basin boundary to the most downgradient well. Estimated MRT error (±0·3 to ±0·7 years) is small for short MRTs and is much larger (±10 years) for a well with an MRT (16 years) near the limit of the method. Groundwater transit time estimates based on Darcy's law, tritium content, and the seasonal δ18O amplitude approach appear to be consistent within the limits of each method. The results from this study suggest that use of the δ18O seasonal variation method to determine MRTs can help assess groundwater recharge areas in small headwaters catchments.
An evaluation of catchment-scale phosphorus mitigation using load apportionment modelling.

PubMed

Greene, S; Taylor, D; McElarney, Y R; Foy, R H; Jordan, P

2011-05-01

Functional relationships between phosphorus (P) discharge and concentration mechanisms were explored using a load apportionment model (LAM) developed for use in a freshwater catchment in Ireland with fourteen years of data (1995-2008). The aim of model conceptualisation was to infer changes in point and diffuse sources from catchment P loading during P mitigation, based upon a dataset comprising geospatial and water quality data from a 256km(2) lake catchment in an intensively farmed drumlin region of the midlands of Ireland. The model was calibrated using river total P (TP), molybdate reactive P (MRP) and runoff data from seven subcatchments. Temporal and spatial heterogeneity of P sources existed within and between subcatchments; these were attributed to differences in agricultural intensity, soil type and anthropogenically-sourced effluent P loading. Catchment rivers were sensitive to flow regime, which can result in eutrophication of rivers during summer and lake enrichment from frequent flood events. For one sewage impacted river, the LAM estimated that point sourced P contributed up to of 90% of annual MRP load delivered during a hydrological year and in this river point P sources dominated flows up to 92% of days. In the other rivers, despite diffuse P forming a majority of the annual P exports, point sources of P dominated flows for up to 64% of a hydrological year. The calibrated model demonstrated that lower P export rates followed specific P mitigation measures. The LAM estimated up to 80% decreases in point MRP load after enhanced P removal at waste water treatments plants in urban subcatchments and the implementation of septic tank and agricultural bye-laws in rural subcatchments. The LAM approach provides a way to assess the long-term effectiveness of further measures to reduce P loadings in EU (International) River Basin Districts and subcatchments. Copyright © 2011 Elsevier B.V. All rights reserved.
The combined effects of topography and vegetation on catchment connectivity

NASA Astrophysics Data System (ADS)

Nippgen, F.; McGlynn, B. L.; Emanuel, R. E.

2012-12-01

The deconvolution of whole catchment runoff response into its temporally dynamic source areas is a grand challenge in hydrology. The extent to which the intersection of static and dynamic catchment characteristics (e.g. topography and vegetation) influences water redistribution within a catchment and the hydrologic connectivity of hillslopes to the riparian and stream system is largely unknown. Over time, patterns of catchment storage shift and, because of threshold connectivity behavior, catchment areas become disconnected from the stream network. We developed a simple but spatially distributed modeling framework that explicitly incorporates static (topography) and dynamic (vegetation) catchment structure to document the evolution of catchment connectivity over the course of a water year. We employed directly measured eddy-covariance evapotranspiration data co-located within a highly instrumented (>150 recording groundwater wells) and gauged catchment to parse the effect of current and zero vegetation scenarios on the temporal evolution of hydrologic connectivity. In the absence of vegetation, and thus in the absence of evapotranspiration, modeled absolute connectivity was 4.5% greater during peak flow and 3.9% greater during late summer baseflow when compared to the actual vegetation scenario. The most significant differences in connected catchment area between current and zero vegetation (14.9%) occurred during the recession period in early July, when water and energy availability were at an optimum. However, the greatest relative difference in connected area occurs during the late summer baseflow period when the absence of evapotranspiration results in a connected area approximately 500% greater than when vegetation is present, while the relative increase during peak flow is just 6%. Changes in connected areas ultimately lead to propose a biologically modified geomorphic width function. This biogeomorphic width function is the result of lateral water redistribution driven by topography and water uptake by vegetation.
Determining health-care facility catchment areas in Uganda using data on malaria-related visits

PubMed Central

Charland, Katia; Kigozi, Ruth; Dorsey, Grant; Kamya, Moses R; Buckeridge, David L

2014-01-01

Abstract Objective To illustrate the use of a new method for defining the catchment areas of health-care facilities based on their utilization. Methods The catchment areas of six health-care facilities in Uganda were determined using the cumulative case ratio: the ratio of the observed to expected utilization of a facility for a particular condition by patients from small administrative areas. The cumulative case ratio for malaria-related visits to these facilities was determined using data from the Uganda Malaria Surveillance Project. Catchment areas were also derived using various straight line and road network distances from the facility. Subsequently, the 1-year cumulative malaria case rate was calculated for each catchment area, as determined using the three methods. Findings The 1-year cumulative malaria case rate varied considerably with the method used to define the catchment areas. With the cumulative case ratio approach, the catchment area could include noncontiguous areas. With the distance approaches, the denominator increased substantially with distance, whereas the numerator increased only slightly. The largest cumulative case rate per 1000 population was for the Kamwezi facility: 234.9 (95% confidence interval, CI: 226.2–243.8) for a straight-line distance of 5 km, 193.1 (95% CI: 186.8–199.6) for the cumulative case ratio approach and 156.1 (95% CI: 150.9–161.4) for a road network distance of 5 km. Conclusion Use of the cumulative case ratio for malaria-related visits to determine health-care facility catchment areas was feasible. Moreover, this approach took into account patients’ actual addresses, whereas using distance from the facility did not. PMID:24700977
Integrative analysis of the Lake Simcoe watershed (Ontario, Canada) as a socio-ecological system.

PubMed

Neumann, Alex; Kim, Dong-Kyun; Perhar, Gurbir; Arhonditsis, George B

2017-03-01

Striving for long-term sustainability in catchments dominated by human activities requires development of interdisciplinary research methods to account for the interplay between environmental concerns and socio-economic pressures. In this study, we present an integrative analysis of the Lake Simcoe watershed, Ontario, Canada, as viewed from the perspective of a socio-ecological system. Key features of our analysis are (i) the equally weighted consideration of environmental attributes with socioeconomic priorities and (ii) the identification of the minimal number of key socio-hydrological variables that should be included in a parsimonious watershed management framework, aiming to establish linkages between urbanization trends and nutrient export. Drawing parallels with the concept of Hydrological Response Units, we used Self-Organizing Mapping to delineate spatial organizations with similar socio-economic and environmental attributes, also referred to as Socio-Environmental Management Units (SEMUs). Our analysis provides evidence of two SEMUs with contrasting features, the "undisturbed" and "anthropogenically-influenced", within the Lake Simcoe watershed. The "undisturbed" cluster occupies approximately half of the Lake Simcoe catchment (45%) and is characterized by low landscape diversity and low average population density <0.4 humans ha -1 . By contrast, the socio-environmental functional properties of the "anthropogenically-influenced" cluster highlight the likelihood of a stability loss in the long-run, as inferred from the distinct signature of urbanization activities on the tributary nutrient export, and the loss of subwatershed sensitivity to natural mechanisms that may ameliorate the degradation patterns. Our study also examines how the SEMU concept can augment the contemporary integrated watershed management practices and provides directions in order to promote environmental programs for lake conservation and to increase public awareness and engagement in stewardship initiatives. Copyright © 2016 Elsevier Ltd. All rights reserved.
60,000 years of vegetation and climate change in eastern, lowland Bolivia

NASA Astrophysics Data System (ADS)

Whitney, B. S.; Mayle, F. E.

2006-12-01

Presented here is a late Quaternary pollen record from Laguna La Gaiba (17°45`S, 57°35`W), a 55 km2 lake located at the western margin of the Pantanal basin, the world's largest tropical wetland, and the eastern limit of the Bolivian Chiquitano dry forest. A suite of 12 AMS radiocarbon dates on terrestrial macrofossils demonstrates a continuous sediment record spanning at least the last 60,000 years. Today, upland areas of the lake catchment are blanketed by closed-canopy semi-deciduous forest. However, arboreal pollen was largely absent from glacial-age sediments, indicative of a climate drier than present, and a landscape dominated by open, herbaceous savanna. Tropical forest appeared during the glacial-Holocene transition, pointing to increased precipitation, but was floristically different from those of the Holocene. Seasonally-dry tropical forest, floristically similar to that of today, appeared during the early Holocene. Changes in proportions of key dry forest taxa point to rising precipitation in the mid-late Holocene, consistent with other records from the southern hemisphere lowlands, as well as the tropical Andes. However, our evidence for reduced precipitation in the lowlands during the Last Glacial Maximum contrasts with high water- levels at Lake Titicaca and other sites on the Altiplano.
Lacustrine Records of Holocene Mountain Glacier Fluctuations from Western Greenland

NASA Astrophysics Data System (ADS)

Schweinsberg, A.; Briner, J. P.; Bennike, O.

2014-12-01

Recent studies have focused on documenting fluctuations of the Greenland Ice Sheet margin throughout the Holocene but few data exist that constrain past changes of local glaciers independent of the ice sheet. Our research combines proglacial lake sediment analysis with cosmogenic 10Be dating of Holocene moraines and radiocarbon dating of ice-cap-killed vegetation with an overall objective to use this multi-proxy approach to generate a detailed record of the coupled climate-glacier system through the Holocene. Here, we present lacustrine records of mountain glacier variability from continuous pro-glacial lake sediment sequences recovered from two glaciated catchments in northeastern Nuussuaq, western Greenland. We use radiocarbon-dated sediments from Sikuiui and Pauiaivik lakes to reconstruct the timing of advance and retreat of local glaciers. Sediments were characterized with magnetic susceptibility (MS), gamma density, Itrax XRF and visible reflectance spectroscopy at 0.2 cm intervals and sediment organic matter at 0.5 cm intervals. Basal radiocarbon ages provide minimum-age constraints on deglaciation from Sikuiui and Pauiaivik lakes of ~9.6 and 8.7 ka, respectively. Organic-rich gyttja from deglaciation until ~5.0 ka in Pauiaivik Lake suggests minimal glacial extent there while slightly elevated MS values from ~9.0 - 7.0 ka in Sikuiui Lake may reflect early Holocene glacial advances. Minerogenic sediment input gradually increases starting at ~5.0 ka in Pauiaivik Lake, which we interpret as the onset of Neoglaciation in the catchment. Furthermore, a distinct episode of enhanced glacial activity from ~4.0 - 2.2 ka in Sikuiui Lake may be correlative to a period of persistent snowline lowering evidenced by radiocarbon dates of ice-killed vegetation from nearby ice cap margins. Results from these lacustrine records and our ice-killed vegetation dataset suggest a middle Holocene onset of Neoglaciation ~5.0 - 4.0 ka in this region. We are supplementing these records with cosmogenic 10Be exposure dating to further constrain the timing of deglaciation. In addition, these sedimentary archives will continue to be compared to radiocarbon dates of ice-killed vegetation along adjacent ice cap margins to determine if times of persistent snowline lowering are correlative to periods of glacier advance.
Lake ecosystem response to rapid lateglacial climate changes in lake sediments from northern Poland

NASA Astrophysics Data System (ADS)

Słowiński, Michał; Zawiska, Izabela; Ott, Florian; Noryśkiewicz, Agnieszka M.; Apolinarska, Karina; Lutyńska, Monika; Michczyńska, Danuta J.; Brauer, Achim; Wulf, Sabine; Skubała, Piotr; Błaszkiewicz, Mirosław

2013-04-01

During the Late Glacial Period environment changes were triggered by climatic oscillations which in turn controlled processes like, for example, permafrost thawing, vegetation development and ground water circulation. These environmental changes are ideally recorded in lake sediments and thus can be reconstructed applying a multi-poxy approach. Here, we present the results from the Trzechowskie paleolake, located in the northern Polish lowlands (eastern part of the Pomeranian Lakeland). The site is situated on the outwash plain of the Wda River, which was formed during the Pomeranian phase of the Vistulian glaciation ca 16,000 14C yrs BP. The depression of the Trzechowskie lake basin formed after melting of a buried ice block during the Allerød (13903±170 cal yrs BP). We reconstructed environmental changes in the Trzechowskie paleolake and its catchment using biotic proxies (macrofossils, pollen, cladocera, diatoms, oribatidae mite) and geochemical proxies (δ18O, δ13C, loss-on-ignition (LOI), CaCO3 content). In addition, we carried out µ-XRF element core scanning. The chronology has been established by means of biostratigraphyAMS14C dating on plant macro remains, varve counting in laminated intervals and the late Allerød Laacher See Tephra isochrone. Our results showed that biogenic accumulation in the lake started during the Bølling. Development of coniferous forest during the Allerød with dominance of Pinus sylvestris lead to leaching of carbonates in the catchment due to low pH increasing the flux of Ca ions into the lake. In consequence calcite precipitating in the lake increased as evidences by increasing CaCO3 contents. Both biotic and physical proxies clearly reflect the rapid decrease in productivity at the onset of the Younger Dryas. We compare the data from the Trzechowskie paleolake with the Meerfelder Maar and Rehwiese lake records based on tephrochronological synchronization using the Laacher See Tephra. This study is a contribution to the Virtual Institute ICLEA (Integrated Climate and Landscape Evolution Analysis) funded by the Helmholtz Association.
Tracking Changes in Iron Mineralogy Through Time in Gale Crater and Terrestrial Analogues

NASA Astrophysics Data System (ADS)

Sheppard, R.; Milliken, R.; Russell, J. M.

2017-12-01

Iron and other redox-sensitive elements measured in ancient mudstones of Gale Crater, Mars by the Curiosity rover can provide information on past climate and interactions between water and the early atmosphere. Preserved ferrous mineralogy can constrain lake bottom water conditions and potentially the relative position of the oxycline and/or shoreline through the stratigraphic section. Multiple oxidation states in a given assemblage may also indicate a potential energy source for microbes. The X-ray amorphous fraction of all rocks measured in Gale Crater to date is also enigmatic: it can constitute up to 50 wt% of the sediment but the precise composition and formation conditions are unknown. Features similar to those in the martian mudstones are seen in sediments from the terrestrial redox-stratified Lake Towuti, including alternating ferrous and ferric mineralogy and an abundant Fe-rich X-ray amorphous phase. To constrain conditions in the water column and early diagenetic processes, we present trends in chemistry and mineralogy for sediment acquired from soils in the mafic/ultramafic catchment and lake bottom/core samples. The soils contain high abundances of crystalline Fe-oxides (e.g. magnetite, goethite, hematite), whereas sediment from the very surface of the lake bottom maintain high Fe but not in crystalline form based on XRD. This suggests Fe is being rapidly cycled to form amorphous phases after entering the lake. Sequential extractions to isolate highly reactive iron (e.g. ferrihydrite) will be used to confirm the relative abundance of poorly crystalline phases in catchment versus lake sediment. Sediments from a 150 m core representing 1 Myr lake history also maintain high Fe content and distinct alternating bands of red and green sediment, but there are no crystalline Fe-oxides discernible in XRD data. The process(es) and timescale for this switching is not yet known, but understanding the conditions that allow ferrous vs. ferric iron to form, and what other changes happen concurrently with silicates such as clay minerals, may help constrain how to interpret lake sediment chemistry and mineralogy in terms of climate on Earth and Mars.
Holocene evolution of a montane lake catchment inferred from multiproxy sediment analysis : climatic and anthropic impacts in french prealps

NASA Astrophysics Data System (ADS)

Bajard, Manon; Sabatier, Pierre; Poulenard, Jérôme; David, Fernand; Arnaud, Fabien; Develle, Anne-Lise; Reyss, Jean-Louis; Fanget, Bernard; Malet, Emmanuel; Crouzet, Christian

2015-04-01

Lake La Thuile in the Massif des Bauges (874 m a.s.l. French Alps) provides a 18 meters sedimentary sequence. Due to its mid-altitude position, this lake is one of the first to be formed through the glacial retreat and documents the evolution of its catchment since the Late Glacial Maximum. The first 6 meters of the core cover the last 12 000 years, and allowed to study human/climate/environment interactions in a carbonated environment. This study is the first one to investigate a mid-altitude lake in the French Alps for paleoenvironment reconstruction from lake sediment archive. Its altitudinal position presents the advantage to be very accessible to human activities and allows more developed agriculture than in higher altitude. This study aims to determined how and when is expressed the erosive response of such an environment to human settlement. High resolution multiproxy analysis of the first 6 meters including sedimentological, palynological and geochemical data associated to a well-constrained chronology over the Holocene period allows us to understand the respective impacts of both climate and human on the evolution of Lake La Thuile environment. Five major phases of evolution have been highlighted over this period. From 12 000 to 10 000 yr cal. BP, the vegetation is developing with the onset of hardwood species and the disappearance of Pinus. From 10 000 to 4500 yr cal. BP the warmer climatic conditions of the middle of the Holocene allows the forest to densify and the very low sedimentation rate indicates that the forest stabilizes slopes and prevents from the erosion on the watershed. The climate cooling of the Neoglacial period triggers a first erosive phase with a decreasing of the forest around 3300 cal. BP. Human settlements are suggested at La Thuile from 2500 yr cal. BP by palynological evidence of anthropic taxa. The triggered clearing is accompanied by a second erosive phase related to anthropic activities during the Roman period. Erosion intensified from 1600 cal. BP in a third erosive phase corresponding to agriculture intensification during the Middle Ages. At the end of the Middle Ages, human footprint seems to decrease but the reason of this change is not resolved between social determination or/and climate forcing. These three erosive phases may have completely changed the catchment behavior until the agricultural abandonment in the middle of the 20th century. Lake La Thuile sedimentary infill shows a landscape evolution first controlled by climate and progressively, since 2500 years ago, human activities came to superimpose. The role of human seems to be more important with abrupt and maybe irreversible modifications of the landscape.

An ecohydrological-based management of Lake Beratan in Bedugul, Bali

NASA Astrophysics Data System (ADS)

Atmaja, D. M.; Budiastuti, M. S.; Setyono, P.; Sunarto

2018-04-01

Lake Beratan is one of waterway ecosystems located in the upper land of Bedugul, Bali and has become a tourist object which is visited by many foreign as well as domestic tourists. This is supported by a sufficiently high economic growth which, without the community’s being aware of, has caused environmental problems such as the shallowing of the lake, erosion, and water pollution to such an extent that have resulted in the degradation of the function of the lake as the site of catchment. The degradation of the function of the lake can be overcome by ecohydrological-based management. This study was aimed at developing an integrated and long lasting Lake Beratan environment management concept. The study used a descriptive qualitative approach using a survey, by collecting primary and secondary data. On the basis of those data the mapping of the potentials of the lake and problems of the lake which were then integrated to formulate criteria for sustainable use of Lake Beratan waters environment resources. The determination of zonation of the lake was done based on those criteria and the community’s existence consideration as well as the exising system of the lake waterway environment use. Based on the study in the field, some recommendations could be made concerning Lake Beratan waterway sustainable and integrated management.
Attributes for MRB_E2RF1 Catchments by Major River Basins in the Conterminous United States: Average Daily Maximum Temperature, 2002

USGS Publications Warehouse

Wieczorek, Michael; LaMotte, Andrew E.

2010-01-01

The MRB_E2RF1 catchments are based on a modified version of the Environmental Protection Agency's (USEPA) ERF1_2 and include enhancements to support national and regional-scale surface-water quality modeling (Nolan and others, 2002; Brakebill and others, 2008). Data were compiled for every MRB_E2RF1 catchment for the conterminous United States covering New England and Mid-Atlantic (MRB1), South Atlantic-Gulf and Tennessee (MRB2), the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy (MRB3), the Missouri (MRB4), the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf (MRB5), the Rio Grande, Colorado, and the Great basin (MRB6), the Pacific Northwest (MRB7) river basins, and California (MRB8).
Attributes for MRB_E2RF1 Catchments by Major River Basins in the Conterminous United States: Average Daily Minimum Temperature, 2002

USGS Publications Warehouse

Wieczorek, Michael; LaMotte, Andrew E.

2010-01-01

The MRB_E2RF1 catchments are based on a modified version of the Environmental Protection Agency's (USEPA) ERF1_2 and include enhancements to support national and regional-scale surface-water quality modeling (Nolan and others, 2002; Brakebill and others, 2011). Data were compiled for every MRB_E2RF1 catchment for the conterminous United States covering New England and Mid-Atlantic (MRB1), South Atlantic-Gulf and Tennessee (MRB2), the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy (MRB3), the Missouri (MRB4), the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf (MRB5), the Rio Grande, Colorado, and the Great basin (MRB6), the Pacific Northwest (MRB7) river basins, and California (MRB8).
Exploring the Recurrence of Contributing Area Dynamics

NASA Astrophysics Data System (ADS)

Spence, C.; Mengistu, S. G.

2015-12-01

Recent years have witnessed a progression towards using models as a tool for predicting high frequency contributing area dynamics in catchments. High frequency contributing area modeling can become a viable alternative to the current approach for estimating contributing area in Canadian catchments, which assumes a static portion of the catchment's gross drainage area. The current approach does not consider the spatiotemporal variability of contributing area dynamics, and therefore, represents an important challenge for characterizing the recurrence that saturated areas in the catchment can actively connect and contribute to the main channel in response to runoff producing snowmelt or storm events. Such characterizations are useful to assess the relative importance of different areas within a catchment for runoff generation, and nutrient production and transport. In this study, the PDMROF configuration of Environment Canada's MESH model has been applied to simulate areas actively contributing to daily streamflow from four nested catchments of the Qu'Appelle River basin. The return periods of annual maximum contributing areas were computed using Weibull's equation. The research also evaluates if runoff magnitude is always associated with the same extent and recurrence of contributing area and investigates how contributing area and streamflow return periods relate. This work provides the foundation for evaluating the effect of environmental changes (mainly land use and climate associated changes) on contributing area recurrence by conducting similar investigations under various environmental change scenarios.
Integrating isotopic tracer techniques with Bayesian modelling for improved assessment and management of sedimentation problems in the Gilgel-Gibe catchment, Ethiopia

NASA Astrophysics Data System (ADS)

Dume, Bayu; Amsalu, Nebiyu; Bode, Samuel; Mtei, Kelvin; Munishi, Linus; Navas, Ana; Semmens, Brice; Smith, Hugh; Stock, Brian; Blake, Will; Boeckx, Pascal

2017-04-01

Soil erosion and associated downstream siltation of dams and lakes is becoming serious threat to catchment ecosystem services supporting water, food and energy security in Ethiopia. Sediments originate on catchment hillslopes but mobilisation processes vary depending on land use and terrain. The Gilgel Gibe hydroelectric dam is one of a series of development projects launched by the Federal Government of Ethiopia. The catchment is characterised by erodible, deforested agricultural land which is also overgrazed. Siltation and nutrient enrichment are significant issues given 'hotspot' sheet erosion estimates of 2210 ton per square km. The annual contribution of sediment from the Gilgel Gibe River to the dam was estimated at 277 thousand tons per year leading to accumulations of 3.75 x 107 cubic metres per year of silt behind the dam. The primary driver for mobilisation and translocation to downstream is believed to be erosion on agricultural lands and collapse of steep banks, through landsliding into river channels in the highland headwaters. The relative importance of specific sources of siltation are unknown and sediment source apportionment has been identified as a first essential step before soil conservation measures can be implemented. Knowledge of sediment source and transfer dynamics is critical to inform management policy decisions to maintain and enhance future food, water and energy security To test the applicability of a new combination of Bayesian unmixing modelling with sediment fingerprinting in this terrain (IMIXSED approach) a demonstration sub-catchment was selected through field assessment in the upper Gilgel-Gibe water-supply catchments (Unta River) and sampling strategies designed. Accordingly, sources, i.e. soil samples from landslides (n=40), eroding channel bank (n = 5), cultivated land (n = 30), grasslands (n = 30), wooded areas (n = 10), homestead plots (n = 10) were collected alongside 10 spatially-integrated sediment deposits from the receptor cobble bed river after the 2016 rainy season. In order to extract reliable information on the sources of fine sediment delivered into rivers and dam, new isotopic techniques (e.g., Compound Specific Stable Isotopes (CSSIs)) combined with other isotopic techniques (fallout radionuclides) and geochemical tracer properties (via WD-XRF) were employed to quantify sediment sources. Results from this demonstration catchment are discussed in the context of the wider sediment pressures on the Hydro-Electric Power infrastructure of the Gilgel Gibe system.
Attributes for MRB_E2RF1 Catchments by Major Rivers Basins in the Conterminous United States: Total Precipitation, 2002

USGS Publications Warehouse

Wieczorek, Michael; LaMotte, Andrew E.

2010-01-01

This tabular data set represents the catchment-average total precipitation in millimeters multiplied by 100 for 2002, compiled for every MRB_E2RF1 catchment of selected Major River Basins (MRBs, Crawford and others, 2006). The source data were the Near-Real-Time Monthly High-Resolution Precipitation Climate Data Set for the Conterminous United States (2002) raster data set produced by the Spatial Climate Analysis Service at Oregon State University. The MRB_E2RF1 catchments are based on a modified version of the Environmental Protection Agency's (USEPA) ERF1_2 and include enhancements to support national and regional-scale surface-water quality modeling (Nolan and others, 2002; Brakebill and others, 2011). Data were compiled for every MRB_E2RF1 catchment for the conterminous United States covering New England and Mid-Atlantic (MRB1), South Atlantic-Gulf and Tennessee (MRB2), the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy (MRB3), the Missouri (MRB4), the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf (MRB5), the Rio Grande, Colorado, and the Great basin (MRB6), the Pacific Northwest (MRB7) river basins, and California (MRB8).
Advancing Land-Sea Conservation Planning: Integrating Modelling of Catchments, Land-Use Change, and River Plumes to Prioritise Catchment Management and Protection.

PubMed

Álvarez-Romero, Jorge G; Pressey, Robert L; Ban, Natalie C; Brodie, Jon

2015-01-01

Human-induced changes to river loads of nutrients and sediments pose a significant threat to marine ecosystems. Ongoing land-use change can further increase these loads, and amplify the impacts of land-based threats on vulnerable marine ecosystems. Consequently, there is a need to assess these threats and prioritise actions to mitigate their impacts. A key question regarding prioritisation is whether actions in catchments to maintain coastal-marine water quality can be spatially congruent with actions for other management objectives, such as conserving terrestrial biodiversity. In selected catchments draining into the Gulf of California, Mexico, we employed Land Change Modeller to assess the vulnerability of areas with native vegetation to conversion into crops, pasture, and urban areas. We then used SedNet, a catchment modelling tool, to map the sources and estimate pollutant loads delivered to the Gulf by these catchments. Following these analyses, we used modelled river plumes to identify marine areas likely influenced by land-based pollutants. Finally, we prioritised areas for catchment management based on objectives for conservation of terrestrial biodiversity and objectives for water quality that recognised links between pollutant sources and affected marine areas. Our objectives for coastal-marine water quality were to reduce sediment and nutrient discharges from anthropic areas, and minimise future increases in coastal sedimentation and eutrophication. Our objectives for protection of terrestrial biodiversity covered species of vertebrates. We used Marxan, a conservation planning tool, to prioritise interventions and explore spatial differences in priorities for both objectives. Notable differences in the distributions of land values for terrestrial biodiversity and coastal-marine water quality indicated the likely need for trade-offs between catchment management objectives. However, there were priority areas that contributed to both sets of objectives. Our study demonstrates a practical approach to integrating models of catchments, land-use change, and river plumes with conservation planning software to inform prioritisation of catchment management.
Advancing Land-Sea Conservation Planning: Integrating Modelling of Catchments, Land-Use Change, and River Plumes to Prioritise Catchment Management and Protection

PubMed Central

Álvarez-Romero, Jorge G.; Pressey, Robert L.; Ban, Natalie C.; Brodie, Jon

2015-01-01

Human-induced changes to river loads of nutrients and sediments pose a significant threat to marine ecosystems. Ongoing land-use change can further increase these loads, and amplify the impacts of land-based threats on vulnerable marine ecosystems. Consequently, there is a need to assess these threats and prioritise actions to mitigate their impacts. A key question regarding prioritisation is whether actions in catchments to maintain coastal-marine water quality can be spatially congruent with actions for other management objectives, such as conserving terrestrial biodiversity. In selected catchments draining into the Gulf of California, Mexico, we employed Land Change Modeller to assess the vulnerability of areas with native vegetation to conversion into crops, pasture, and urban areas. We then used SedNet, a catchment modelling tool, to map the sources and estimate pollutant loads delivered to the Gulf by these catchments. Following these analyses, we used modelled river plumes to identify marine areas likely influenced by land-based pollutants. Finally, we prioritised areas for catchment management based on objectives for conservation of terrestrial biodiversity and objectives for water quality that recognised links between pollutant sources and affected marine areas. Our objectives for coastal-marine water quality were to reduce sediment and nutrient discharges from anthropic areas, and minimise future increases in coastal sedimentation and eutrophication. Our objectives for protection of terrestrial biodiversity covered species of vertebrates. We used Marxan, a conservation planning tool, to prioritise interventions and explore spatial differences in priorities for both objectives. Notable differences in the distributions of land values for terrestrial biodiversity and coastal-marine water quality indicated the likely need for trade-offs between catchment management objectives. However, there were priority areas that contributed to both sets of objectives. Our study demonstrates a practical approach to integrating models of catchments, land-use change, and river plumes with conservation planning software to inform prioritisation of catchment management. PMID:26714166
Variation and accumulation patterns of poly- and perfluoroalkyl substances (PFAS) in European perch (Perca fluviatilis) across a gradient of pristine Swedish lakes.

PubMed

Åkerblom, Staffan; Negm, Nesrin; Wu, Pianpian; Bishop, Kevin; Ahrens, Lutz

2017-12-01

This study assessed variations in the concentrations of poly- and perfluoroalkyl substances (PFAS) in European perch (Perca fluviatilis) in Swedish lakes and the extent to which fish size, age and indicators of fish trophic ecology (δ 15 N and δ 13 C) correlate with the sum of individual PFAS concentrations (ΣPFAS). Fish muscle tissue samples (n=80) were taken from six lakes across Sweden and analysed using solid-liquid extraction followed by liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS). PFAS levels in the lakes were affected by atmospheric deposition in relatively pristine areas with no direct point source of PFAS in the catchment. PFTeDA, PFUnDA, PFTriDA, PFDoDA, PFDA, PFOS and 6:2 FTSA were detected with a frequency between 68% and 99% and were included in the statistical evaluation. ΣPFAS differed between lakes (ANOVA: F=50.6, p<0.0001): fish from lakes in southern Sweden (lake Gårdsjön, 58°03'N, 12°01'E) showed elevated levels of PFAS, with a maximum ΣPFAS of 3.4ng g -1 wet weight (ww) (mean±SD: 0.99±0.63ng g -1 ww), while the lowest levels were found in lake Björntjärn (0.31±0.08ng g -1 ww) in northern Sweden (63°54'N, 18°51'E). PFOS was most abundant in perch from south-western Sweden, while other long-chain perfluorocarbons (>10 carbon atoms) were relatively more abundant in lakes in northern Sweden. Pearson correlation coefficients indicated that concentrations of PFAS in perch did not show any relation to fish size or age and were negatively correlated with trophic position of the fish (δ 15 N). It was also found that ΣPFAS were negatively correlated with both latitude and altitude. The PFAS data in this study represent national background concentrations in freshwater fish across Swedish lakes. Copyright © 2017 Elsevier B.V. All rights reserved.
Spatial variations in snowpack chemistry, isotopic composition of NO3- and nitrogen deposition from the ice sheet margin to the coast of western Greenland

NASA Astrophysics Data System (ADS)

Curtis, Chris J.; Kaiser, Jan; Marca, Alina; Anderson, N. John; Simpson, Gavin; Jones, Vivienne; Whiteford, Erika

2018-01-01

The relative roles of anthropogenic nitrogen (N) deposition and climate change in causing ecological change in remote Arctic ecosystems, especially lakes, have been the subject of debate over the last decade. Some palaeoecological studies have cited isotopic signals (δ(15N)) preserved in lake sediments as evidence linking N deposition with ecological change, but a key limitation has been the lack of co-located data on both deposition input fluxes and isotopic composition of deposited nitrate (NO3-). In Arctic lakes, including those in western Greenland, previous palaeolimnological studies have indicated a spatial variation in δ(15N) trends in lake sediments but data are lacking for deposition chemistry, input fluxes and stable isotope composition of NO3-. In the present study, snowpack chemistry, NO3- stable isotopes and net deposition fluxes for the largest ice-free region in Greenland were investigated to determine whether there are spatial gradients from the ice sheet margin to the coast linked to a gradient in precipitation. Late-season snowpack was sampled in March 2011 at eight locations within three lake catchments in each of three regions (ice sheet margin in the east, the central area near Kelly Ville and the coastal zone to the west). At the coast, snowpack accumulation averaged 181 mm snow water equivalent (SWE) compared with 36 mm SWE by the ice sheet. Coastal snowpack showed significantly greater concentrations of marine salts (Na+, Cl-, other major cations), ammonium (NH4+; regional means 1.4-2.7 µmol L-1), total and non-sea-salt sulfate (SO42-; total 1.8-7.7, non-sea-salt 1.0-1.8 µmol L-1) than the two inland regions. Nitrate (1.5-2.4 µmol L-1) showed significantly lower concentrations at the coast. Despite lower concentrations, higher precipitation at the coast results in greater net deposition for NO3- as well as NH4+ and non-sea-salt sulfate (nss-SO42-) relative to the inland regions (lowest at Kelly Ville 6, 4 and 3; highest at coast 9, 17 and 11 mol ha-1 a-1 of NO3-, NH4+ and nss-SO42- respectively). The δ(15N) of snowpack NO3- shows a significant decrease from inland regions (-5.7 ‰ at Kelly Ville) to the coast (-11.3 ‰). We attribute the spatial patterns of δ(15N) in western Greenland to post-depositional processing rather than differing sources because of (1) spatial relationships with precipitation and sublimation, (2) within-catchment isotopic differences between terrestrial snowpack and lake ice snowpack, and (3) similarities between fresh snow (rather than accumulated snowpack) at Kelly Ville and the coast. Hence the δ(15N) of coastal snowpack is most representative of snowfall in western Greenland, but after deposition the effects of photolysis, volatilization and sublimation lead to enrichment of the remaining snowpack with the greatest effect in inland areas of low precipitation and high sublimation losses.
Holocene evolution of aquatic bioactivity and terrestrial erosion inferred from Skorarvatn, Vestfirðir, Iceland: Where is the Little Ice Age?

NASA Astrophysics Data System (ADS)

Harning, D.; Geirsdottir, A.; Miller, G. H.

2016-12-01

Icelandic lake sediment is well suited to provide high-resolution, well-dated continuous archives of North Atlantic climate variability. We provide new insight into the Holocene climate evolution of Vestfirðir, NW Iceland, from a 10.3 ka multi-proxy lake sediment record from non-glacial lake Skorarvatn. Age control is derived from a combination of tephrochronology and 14C-dated macrofossils. Sediment samples were analyzed for both physical (MS, density) and biological (TC, TN, δ13C, δ15N, C/N, BSi) climate proxies, providing a sub-centennial record of aquatic bioactivity and terrestrial landscape stability, and hence, summer temperature. The lake basin was ice free by at least 10.3 ka yet the waning Icelandic Ice Sheet persisted in the catchment until 9.3 ka. The local Holocene Thermal Maximum (HTM), inferred from maximum aquatic bioactivity, spans 8.9 to 7.2 ka but was interrupted by significant cooling at 8.2 ka. In accordance with other Icelandic climate records documenting progressively cooler summers following the HTM, our record reveals reduced aquatic productivity and elevated terrestrial erosion toward the present. Superimposed on this 1st order trend are abrupt episodes of cooling, inferred from low aquatic bioactivity and/or enhanced landscape instability, at 6.4, 4.2, 3, 2.5 and 1.5 ka. Surprisingly, there is no clear indication of the Little Ice Age (LIA) in our record despite evidence for the local ice cap, Drangajökull, attaining maximum areal coverage at this time. Persistently low temperatures inferred from reduced aquatic productivity plateau at 2 ka whereas increasing terrestrial erosion ceases at 1 ka. Lack of a catchment erosion signal during the LIA may be the result of depleted catchment soils and/or perennially frozen ground preventing the mobilization of soil and vegetation. With the exception of the LIA, Skorarvatn's qualitative summer temperature record corresponds closely to summer sea surface temperature and sea ice records on the North Iceland Shelf, supporting previous evidence that the North Atlantic imparts a significant impact of the state of Iceland's terrestrial climate.
Species interactions and response time to climate change: ice-cover and terrestrial run-off shaping Arctic char and brown trout competitive asymmetries

NASA Astrophysics Data System (ADS)

Finstad, A. G.; Palm Helland, I.; Jonsson, B.; Forseth, T.; Foldvik, A.; Hessen, D. O.; Hendrichsen, D. K.; Berg, O. K.; Ulvan, E.; Ugedal, O.

2011-12-01

There has been a growing recognition that single species responses to climate change often mainly are driven by interaction with other organisms and single species studies therefore not are sufficient to recognize and project ecological climate change impacts. Here, we study how performance, relative abundance and the distribution of two common Arctic and sub-Arctic freshwater fishes (brown trout and Arctic char) are driven by competitive interactions. The interactions are modified both by direct climatic effects on temperature and ice-cover, and indirectly through climate forcing of terrestrial vegetation pattern and associated carbon and nutrient run-off. We first use laboratory studies to show that Arctic char, which is the world's most northernmost distributed freshwater fish, outperform trout under low light levels and also have comparable higher growth efficiency. Corresponding to this, a combination of time series and time-for-space analyses show that ice-cover duration and carbon and nutrient load mediated by catchment vegetation properties strongly affected the outcome of the competition and likely drive the species distribution pattern through competitive exclusion. In brief, while shorter ice-cover period and decreased carbon load favored brown trout, increased ice-cover period and increased carbon load favored Arctic char. Length of ice-covered period and export of allochthonous material from catchments are major, but contrasting, climatic drivers of competitive interaction between these two freshwater lake top-predators. While projected climate change lead to decreased ice-cover, corresponding increase in forest and shrub cover amplify carbon and nutrient run-off. Although a likely outcome of future Arctic and sub-arctic climate scenarios are retractions of the Arctic char distribution area caused by competitive exclusion, the main drivers will act on different time scales. While ice-cover will change instantaneously with increasing temperature, changes in catchment vegetation, such as forest-line or shrub advancement affecting carbon and nutrient transport into lakes, act on considerably longer time-scales. This study therefore emphasizes the recurring challenge for ecological climate change studies related to species interactions within and across ecosystem compartments and the response time of ecosystems.
Linking sedimentary total organic carbon to 210Pbex chronology from Changshou Lake in the Three Gorges Reservoir Region, China.

PubMed

Anjum, Raheel; Gao, Jinzhang; Tang, Qiang; He, Xiubin; Zhang, Xinbao; Long, Yi; Shi, Zhonglin; Wang, Mingfeng

2017-05-01

The influences of total organic carbon (TOC) and total nitrogen (TN) on Lead-210 ( 210 Pb) dating have recently been of increasing concern in lacustrine research. Sediment core from Changshou Lake in the Longxi catchment was investigated for influence of TOC on 210 Pb dating. Lead-210 excess ( 210 Pb ex ), Cesium-137 ( 137 Cs) activities, TOC, TN, and particle size were measured. We proposed a dating index based on 137 Cs chronology and particle size distribution of the lake sediment profile and rainfall erosivities calculated from Longxi catchment metrological records. Increasing trends in TOC and TN were specifically caused by commercial cage fish farming after 1989. The statistically significant correlation between 210 Pb ex activity, TOC (0.61, p = 0.04) and TN (0.51, p = 0.04), respectively explained post-1989 210 Pb scavenging. The 210 Pb ex activity was closely related with coupled peaks of TOC and TN from mass depth 5-10 g cm -2 . Higher TOC/TN ratio (8.33) indicated submerged macrophytes and native aquatic algal growth as main source of carbon from enhanced primary productivity because of massive fertilizer use and coherent climate warming. The study supported key hypothesis on vital role of fertilizer usage and algal derived TOC in controlling sedimentary 210 Pb ex activity at Changshou Lake sediment. 137 Cs profile and erosive events as time markers provided reliable and consistent sedimentation rate of (1.6 cm y -1 ). 210 Pb ex activity decayed exponentially after peak at mass depth 5.68 g cm -2 . Therefore, violation of 210 Pb dating primary assumptions made it inappropriate for sediment dating at Changshou Lake. TOC content must be considered while using 210 Pb as dating tool for lake sediment profiles. Copyright © 2017 Elsevier Ltd. All rights reserved.
Hydrology or biology? Modeling simplistic physical constraints on lake carbon biogeochemistry to identify when and where biology is likely to matter

NASA Astrophysics Data System (ADS)

Jones, S.; Zwart, J. A.; Solomon, C.; Kelly, P. T.

2017-12-01

Current efforts to scale lake carbon biogeochemistry rely heavily on empirical observations and rarely consider physical or biological inter-lake heterogeneity that is likely to regulate terrestrial dissolved organic carbon (tDOC) decomposition in lakes. This may in part result from a traditional focus of lake ecologists on in-lake biological processes OR physical-chemical pattern across lake regions, rather than on process AND pattern across scales. To explore the relative importance of local biological processes and physical processes driven by lake hydrologic setting, we created a simple, analytical model of tDOC decomposition in lakes that focuses on the regulating roles of lake size and catchment hydrologic export. Our simplistic model can generally recreate patterns consistent with both local- and regional-scale patterns in tDOC concentration and decomposition. We also see that variation in lake hydrologic setting, including the importance of evaporation as a hydrologic export, generates significant, emergent variation in tDOC decomposition at a given hydrologic residence time, and creates patterns that have been historically attributed to variation in tDOC quality. Comparing predictions of this `biologically null model' to field observations and more biologically complex models could indicate when and where biology is likely to matter most.
Effects of Nitrogen Load on the Function and Diversity of Methanotrophs in the Littoral Wetland of a Boreal Lake

PubMed Central

Siljanen, Henri M. P.; Saari, Anne; Bodrossy, Levente; Martikainen, Pertti J.

2012-01-01

Methane is the second most abundant greenhouse gas in the atmosphere. A major part of the total methane emissions from lake ecosystems is emitted from littoral wetlands. Methane emissions are significantly reduced by methanotrophs, as they use methane as their sole energy and carbon source. Methanotrophic activity can be either activated or inhibited by nitrogen. However, the effects of nitrogen on methanotrophs in littoral wetlands are unknown. Here we report how nitrogen loading in situ affected the function and diversity of methanotrophs in a boreal littoral wetland. Methanotrophic community composition and functional diversity were analyzed with a particulate methane monooxygenase (pmoA) gene targeted microarray. Nitrogen load had no effects on methane oxidation potential and methane fluxes. Nitrogen load activated pmoA gene transcription of type I (Methylobacter, Methylomonas, and LW21-freshwater phylotypes) methanotrophs, but decreased the relative abundance of type II (Methylocystis, Methylosinus trichosporium, and Methylosinus phylotypes) methanotrophs. Hence, the overall activity of a methanotroph community in littoral wetlands is not affected by nitrogen leached from the catchment area. PMID:22363324
Lower Vistula fluvial lakes as possible places of deep groundwaters effluence (Grudziądz Basin, North Central Poland)

NASA Astrophysics Data System (ADS)

Kordowski, Jaroslaw; Kubiak-Wójcicka, Katarzyna; Solarczyk, Adam; Tyszkowski, Sebastian

2014-05-01

Regarding the outflow the Vistula River is the largest river in the Baltic catchment. In its lower course, below Bydgoszcz, in the Late Holocene Vistula channel adopted an weakly anastomosing fluvial pattern destroyed by intensive human hydrotechnical activity and by the regulation which have intensified about 200 years ago. Channel regulation have left many artificially separated fluvial lakes. Part of them infilled rapidly but the majority have persisted to present day almost unchanged. It has also arised the question: what drives the resistence for silting? To solve the problem there were conducted simultaneous hydrological and geomorphological investigations, because there were two concepts: one that the mineral material is removed from fluvial lakes while high stands by flood waters and second that the material is removed due to high groundwater "exchange" rate when the fluvial lake has a sufficient hydrological connectivity to the main Vistula channel. The Vistula valley crosses morainic plains of the last glaciation. On the average it has about 10 km width and is incised about 70 - 80 m deep, compared to neighbouring plains, dissecting all the Quaternary aquifers. On the floodplain area the Quaternary sediments lay with a layer of only 10-20 m thickness over Miocene and Oligocene sands. In favourable conditions, particularly while a low stand there exists the possibility of Tertiary water migration toward the surface of fluvial lakes provided they have not continuous flood sediments cover on their floors. As an example of such a lake with an intensive water exchange rate by supposed deep groundwaters was chosen the Old Vistula lake (Stara Wisła) near Grudziądz town. The lake has an area of 40 ha, mean depth 1,73 m, maximum depth 8 m, length about 4 km and medium width about 100 m. In the years 2011-2014, with two weeks frequency, in its surficial water layer were conducted measures which included temperature, pH, Eh, suspended matter amount, total and carbonaceous mineralization. Similar measurements were also conducted in other fluvial lakes and Vistula tributaries. Investigations carried proved the general similarity between physical and chemical properties of lakes and watercourses analysed. However, there exists distinct gradient of carbonaceous mineralization from small values in the Vistula channel to high values at the valley edges. PH and Eh parameters in the Old Vistula lake were different than in all other surveyed sites what leads to conclusion that it is fed by deeper groundwaters than in the case of other fluvial lakes and Vistula tributaries, particularly in low water stand times. Acknowledgements: This study is a contribution to the Virtual Institute of Integrated Climate and Landscape Evolution (ICLEA) of the Helmholtz Association.
Influence of Monsoon variations on ecosystem changes on the Central Tibetan Plateau during the last 24 ka cal BP (Invited)

NASA Astrophysics Data System (ADS)

Kasper, T.; Haberzettl, T.; Zhu, L.; Maeusbacher, R.

2013-12-01

Lakes as archives of climate and environmental change are well known and well investigated all over the world, also in high mountain areas such as the Tibetan Plateau (TP) which is one of the most important key players in global climate circulation. Lake sediment records in this area, which were subject to lots of paleoenvironmental investigations, are mostly focused on the Holocene, often showing discontinuities due to desiccation or are located at the margin of the TP, such as Lake Qinghai. Here we present the first continuous lake sediment record from the southern central TP from Lake Nam Co, comprising ~24 ka cal BP, i.e., the LGM, the post-Glacial and the entire Holocene. The record reveals environmental changes with varying intensities. Extraordinary high sediment accumulation rates (SAR = 1.3 mm a-1) and quite large quantities of minerogenic input associated with the absence of ostracods during the LGM point to a small lake within a cold and dry environment. Around 19 ka cal BP reduced SAR (~0.3 mm a-1) and the occurrence of ostracods refer to a rising lake level in a moister environment. During the post-Glacial (~16 ka cal BP) changes in the geochemical composition of the sediments and a shift in the pollen composition suggests a change in summer precipitation and wind direction associated with a stronger Indian Ocean Summer Monsoon (IOSM). Major variations in the geochemical parameters between ~12.6 and ~11.6 ka cal BP may reflect the Younger Dryas climate oscillation of the Northern Hemisphere with cool and arid environmental conditions. The most striking hydrological variation within this record occurs at ~9.5 ka cal BP in the early Holocene. A rise in TOC points to enhanced bio-productivity within the lake and the catchment as well as to hampered decomposition of organic matter at the lake floor. Pollen composition refers to alpine meadow vegetation assemblages during this time. This may reflect moist and warm conditions probably associated with a higher lake level and a strong stratification of the water body. Nevertheless, during the mid- and late-Holocene some changes of minor amplitude also occur. Around 4 ka cal BP a short-term increase in Mg points to a dry-event as seen in other monsoon dominated records. The probably most intensive shift to drier conditions with a rapidly falling lake level has been proposed to have occurred around 2 ka cal BP. Even the recent climate warming associated with higher rates of glacier melting, enhanced surface runoff and a rising lake level is reflected by this multi-proxy investigation.
Promise and Pitfalls of Using Grain Size Analysis to Identify Glacial Sediments in Alpine Lake Cores.

NASA Astrophysics Data System (ADS)

Clark, D. H.

2011-12-01

Lakes fed by glacier outwash should have a clastic particle-size record distinct from non-glacial lakes in the same area, but do they? The unique turquoise color of alpine glacial lakes reflects the flux of suspended clastic glacial rock flour to those lakes; conversely, lakes not fed by outwash are generally clear with sediments dominated by organics or slope-wash from nearby hillslopes. This contrast in sediment types and sources should produce a distinct and measureable different in grain sizes between the two settings. Results from a variety of lakes suggest the actual situation is often more subtle and complex. I compare grain size results to other proxies to assess the value of grain size analysis for paleoglacier studies. Over the past 10 years, my colleagues and I have collected and analyzed sediment cores from a wide variety of lakes below small alpine glaciers in an attempt to constrain the timing and magnitude of alpine glaciation in those basins. The basic concept is that these lakes act as continuous catchments for any rock flour produced upstream by glacier abrasion; as a glacier grows, the flux of rock flour to the lake will also increase. If the glacier disappears entirely, rock flour deposition will also cease in short order. We have focused our research in basins with simple sedimentologic settings: mostly small, high-altitude, stripped granitic or metamorphic cirques in which the cirque glaciers are the primary source of clastic sediments. In most cases, the lakes are fed by meltwater from a modern glacier, but were ice free during the earlier Holocene. In such cases, the lake cores should record formation of and changes in activity of the glacier upstream. We used a Malvern Mastersizer 2000 laser particle size analyzer for our grain size analyses, as well as recording magnetic susceptibility, color, and organics for the same cores. The results indicate that although lakes often experience increases in silt and clay-size (<0.63 mm) clastic particles when a glacier is present upstream, the signal can be highly variable and complex, most likely the result of stochastic processes in the basin. Our analyses indicate that although particle size reflects glacier activity upstream, it is rarely the best record of glacier change and is most useful in combination with other proxies, most notably MS, color, and organic content.
Estimation of groundwater recharge via percolation outputs from a rainfall/runoff model for the Verlorenvlei estuarine system, west coast, South Africa

NASA Astrophysics Data System (ADS)

Watson, Andrew; Miller, Jodie; Fleischer, Melanie; de Clercq, Willem

2018-03-01

Wetlands are conservation priorities worldwide, due to their high biodiversity and productivity, but are under threat from agricultural and climate change stresses. To improve the water management practices and resource allocation in these complex systems, a modelling approach has been developed to estimate potential recharge for data poor catchments using rainfall data and basic assumptions regarding soil and aquifer properties. The Verlorenvlei estuarine lake (RAMSAR #525) on the west coast of South Africa is a data poor catchment where rainfall records have been supplemented with farmer's rainfall records. The catchment has multiple competing users. To determine the ecological reserve for the wetlands, the spatial and temporal distribution of recharge had to be well constrained using the J2000 rainfall/runoff model. The majority of rainfall occurs in the mountains (±650 mm/yr) and considerably less in the valley (±280 mm/yr). Percolation was modelled as ∼3.6% of rainfall in the driest parts of the catchment, ∼10% of rainfall in the moderately wet parts of the catchment and ∼8.4% but up to 28.9% of rainfall in the wettest parts of the catchment. The model results are representative of rainfall and water level measurements in the catchment, and compare well with water table fluctuation technique, although estimates are dissimilar to previous estimates within the catchment. This is most likely due to the daily timestep nature of the model, in comparison to other yearly average methods. These results go some way in understanding the fact that although most semi-arid catchments have very low yearly recharge estimates, they are still capable of sustaining high biodiversity levels. This demonstrates the importance of incorporating shorter term recharge event modeling for improving recharge estimates.
History and current safety measures at Laguna Palcacocha, Huaraz, Peru

NASA Astrophysics Data System (ADS)

Salazar Checa, César; Cochachin, Alejo; Frey, Holger; Huggel, Christian; Portocarrero, César

2017-04-01

Laguna Palcacocha is a large glacier lake in the Cordillera Blanca, Peru, located in the Quillcay catchment, above the city of Huaraz, the local capital. On 13 December 1941, the moraine dam lake collapsed, probably after having been impacted by a large ice avalanche, and triggered a major outburst flood. This GLOF destroyed about a third of the city of Huaraz, causing about 2,000 casualties and is therefore one of the deadliest glacier lake outbursts known in history. In 1974, the Glaciology Unit of Peru, responsible for the studying, monitoring and mitigation works related to glacier hazards installed a reinforcement of the natural moraine dam of the newly filled Laguna Palcacocha, with an artificial drainage channel at 7 m below the crest of the reinforced dam. At that time, the lake had an area of 66,800 m2 and a volume of 0.5 x 106 m3. During the past decades, in the course of continued glacier retreat, Laguna Palcacocha has undergone an extreme growth. In February 2016, the lake had an area of 514,000 m2 (7.7 times the area of 1974) and a volume of more than 17 x 106 m3 (more than 34 times the volume of 1974). At the same time, the city of Huaraz, located 20 km downstream of the lake, grew significantly after its almost complete destruction by the 1970 earthquake. Today, about 120,000 people are living in the city. Due to the persisting possibility for large ice avalanches directly above the Palcacocha lake, this constitutes a high-risk situation, requiring new hazard and risk mitigation measures. As an immediate temporal measure, in order to bridge the time until the realization of a more permanent measure, a syphoning system has been installed in 2011, using about ten 700-m pipes with a 10-inch (25.4 cm) diameter. The aim of this syphoning attempt is to lower the lake level by about 7 m, and therefore reduce the lake volume on the one hand, and also reach a higher dam freeboard. However, the system is less effective than assumed, currently the lake level can be reduced by about 4 m below the artificial draining tunnel during the dry season (austral winter, June, July, August), but during the wet season (austral summer, December, January, February), the lake refills to the level of the drainage tunnel. Preparation works and preparatory studies for a more permanent construction are currently ongoing, since 2015 a 12-km access road to Laguna Palcacocha is being built to make the site accessible for construction machines. These structural measures are complemented by non-structural risk reduction measures. A communication system between the lake and the city has been established by radio and satellite phone, and six persons are permanently located at the lake site in order to maintain communication and the syphoning system. In parallel, efforts are currently undertaken to design and implement a technical early warning system, complementing this human monitoring system.

Forest soil erosion prediction as influenced by wildfire and roads

NASA Astrophysics Data System (ADS)

Cao, L.; Brooks, E. S.; Elliot, W.

2017-12-01

Following a wildfire, the risk of erosion is greatly increased. Forest road networks may change the underlying topography and alter natural flow paths. Flow accumulation and energy can be redistributed by roads and alter soil erosion processes. A LiDAR (Light Detection and Ranging) DEM makes it possible to quantify road topography, and estimate how roads influence surface runoff and sediment transport in a fire-disturbed watershed. With GIS technology and a soil erosion model, this study was carried out to evaluate the effect of roads on erosion and sediment yield following the Emerald Fire southwest of Lake Tahoe. The GeoWEPP model was used to estimate onsite erosion and offsite sediment delivery from each hillslope polygon and channel segment before and after fire disturbance in part of the burned area. The GeoWEPP flow path method was used to estimate the post-fire erosion rate of each GIS pixel. A 2-m resolution LiDAR DEM was used as the terrain layer. The Emerald Fire greatly increased onsite soil loss and sediment yields within the fire boundary. Following the fire, 78.71% of the burned area had predicted sediment yields greater than 4 Mg/ha/yr, compared to the preburn condition when 65.3% of the study area was estimated to generate a sediment yield less than 0.25 Mg/ha/yr. Roads had a remarkable influence on the flow path simulation and sub-catchments delineation, affecting sediment transport process spatially. Road segments acted as barriers that intercepted overland runoff and reduced downslope flow energy accumulation, therefore reducing onsite soil loss downslope of the road. Roads also changed the boundary of sub-catchment and defined new hydrological units. Road segments can transport sediment from one sub-catchment to another. This in turn leads to the redistribution of sediment and alters sediment yield for some sub-catchments. Culverts and road drain systems are of vital importance in rerouting runoff and sediment. Conservation structures can be installed to avoid sediment deposition or debris accumulation on the road surface. On the other hand, the outlets of culverts might be at a high risk of increasing downstream channel erosion due to the large amount of runoff. This implies that conservation measurements should be considered to control the runoff and sediment output from culverts.
In situ sulphate stimulation of mercury methylation in a boreal peatland: Toward a link between acid rain and methylmercury contamination in remote environments

NASA Astrophysics Data System (ADS)

Branfireun, Brian A.; Roulet, Nigel T.; Kelly, Carol. A.; Rudd, John W. M.

1999-09-01

Recent studies have found that "pristine" peatlands have high peat and pore water methylmercury (MeHg) concentrations and that peatlands may act as large sources of MeHg to the downstream aquatic system, depending upon the degree of hydrologie connectivity and catchment physiography. Sulphate-reducing bacteria have been implicated as principal methylators of inorganic mercury in many environments with previous research focused primarily on mercury methylation in aquatic sediments. Experiments in a poor fen in the Experimental Lakes Area, northwestern Ontario, Canada, demonstrated that the in situ addition of sulphate to peat and peat pore water resulted in a significant increase in pore water MeHg concentrations. As peatlands cover a large area of the Northern Hemisphere, this finding has potentially far ranging implications for the global mercury cycle, particularly in areas impacted by anthropogenically derived sulphate where the methylmercury fraction of total mercury species may be much larger than in nonimpacted environments.
Sediment budget for Rediu reservoir catchment, North-Eastern Romania

NASA Astrophysics Data System (ADS)

Todosi, Cristian; Niculita, Mihai

2016-04-01

Sediment budgets are a useful tool for geomorphologic analysis, catchment management and environmental assessment, despite the uncertainties related to their assessment. We present the sediment budget construction and validation for a small catchment of 9.5319 kmp (953.19 ha) situated in the North-Eastern part of Romania. The Rediu reservoir was built between 1986 and 1988, on Rediu valley, a left tributary of Bahlui river, north-west from Iasi city. The catchment of the reservoir has 6.5 km in length and 2.5 km in maximum width, the altitudes decreasing from 170 m in the northern part, to 52 m in the southern part. The valley is symmetric, the altitude of the hillslopes going between 200 m to 75 m in one km length, in the transversal section with the maximum width. The floodplain is narrow having between 20 m to 210 m (in the area of confluence with Breazu tributary). The mean slope of the catchment is 6.4 degree, the maximum slope being 24.6 degrees. The length of channels which show banks of up to 2 m is 19.98 km. The land is used predominantly as crops (58.1 %), 16.7 % being covered by pastures (from which over half are eroded), 11.5 % percent of the catchment being covered by planted forests, 9.2 % by rural constructions and roads, 2.9 % by hayfields, 1.5 % by lakes and 0.1 % by orchards. Beside the Rediu reservoir, there are three ponds (15 771, 1761 and 751 sqm) in the catchment. We considered the trap efficiency for the reservoir and the ponds to be 95%. Aerial images from 1963, 1978 , 1984, 2005, 2008, 2010, 2012 and 2014 were used to assess the state of geomorphological processes before and after the reservoir construction. After 1970 a gully system situated in Breazu tributary sub-catchment and several active landslides along the main valley left side were forested. Beside these processes, soil erosion and human impact by constructions are the main processes generating sediment in the study area. The sediment yields were quantified by estimating the quantity of sediments which entered in Rediu reservoir since its construction. The method for volume calculation was the comparison trough geomorphic change detection of two DEMs representing the initial bathymetry (1986 - taken from 1:5 000 scale topographic maps) and a bathymetry surveyed in 2012. The total sediment quantity deposited in the reservoir is 73 947 t (54 776 cbm * 1.35 t/cbm) in the 24 years of operation (1988 to 2012) which means a rate of 3.23 t/ha/y. Soil erosion estimated with RUSEL2 and its routing trough the fluvial system of Rediu reservoir catchment was modelled using WaTEM/SEDEM 2006 model. The modelled quantity of sediments deposited yearly in the Rediu reservoir is 2626 t, which mean 2.75 t/ha. The catchment produce 4803 t, meaning 5.04 t/ha/y from which 2.17 t/ha/y are deposited along the flowpaths, only 0.12 t/ha/y being exported downstream the Rediu reservoir. The difference between the measured and modelled values, 0.48 t/ha/y we argue that is related to the input generated by the human impact, mainly by construction activities. Taking into account that in the near future, the constructions and roads will extend, because of the vicinity with Iasi city, is of great importance to monitor erosion process.
Patterns and predictability in the intra-annual organic carbon variability across the boreal and hemiboreal landscape

USGS Publications Warehouse

Hytteborn, Julia K.; Temnerud, Johan; Alexander, Richard B.; Boyer, Elizabeth W.; Futter, Martyn N.; Fröberg, Mats; Dahné, Joel; Bishop, Kevin H.

2015-01-01

Factors affecting total organic carbon (TOC) concentrations in 215 watercourses across Sweden were investigated using parameter parsimonious regression approaches to explain spatial and temporal variabilities of the TOC water quality responses. We systematically quantified the effects of discharge, seasonality, and long-term trend as factors controlling intra-annual (among year) and inter-annual (within year) variabilities of TOC by evaluating the spatial variability in model coefficients and catchment characteristics (e.g. land cover, retention time, soil type).Catchment area (0.18–47,000 km2) and land cover types (forests, agriculture and alpine terrain) are typical for the boreal and hemiboreal zones across Fennoscandia. Watercourses had at least 6 years of monthly water quality observations between 1990 and 2010. Statistically significant models (p < 0.05) describing variation of TOC in streamflow were identified in 209 of 215 watercourses with a mean Nash-Sutcliffe efficiency index of 0.44. Increasing long-term trends were observed in 149 (70%) of the watercourses, and intra-annual variation in TOC far exceeded inter-annual variation. The average influences of the discharge and seasonality terms on intra-annual variations in daily TOC concentration were 1.4 and 1.3 mg l− 1 (13 and 12% of the mean annual TOC), respectively. The average increase in TOC was 0.17 mg l− 1 year− 1 (1.6% year− 1).Multivariate regression with over 90 different catchment characteristics explained 21% of the spatial variation in the linear trend coefficient, less than 20% of the variation in the discharge coefficient and 73% of the spatial variation in mean TOC. Specific discharge, water residence time, the variance of daily precipitation, and lake area, explained 45% of the spatial variation in the amplitude of the TOC seasonality.Because the main drivers of temporal variability in TOC are seasonality and discharge, first-order estimates of the influences of climatic variability and change on TOC concentration should be predictable if the studied catchments continue to respond similarly.
Aeolian Sediments on the northeastern Tibetan Plateau

NASA Astrophysics Data System (ADS)

Stauch, G.; Lehmkuhl, F.

2013-12-01

The timing and spatial distribution of aeolian sediments on the northeastern Tibetan Plateau have gained increasing interest during the last decades. The formation of the aeolian deposits is often related to cold and dry climate conditions. However, further important parameters are the local geomorphological setting and sediment availability in the source areas of the sediments. Aeolian sediments including loess, sandy loess and sands are widespread in the catchment of the Donggi Cona on the northeastern Tibetan Plateau at around 4000 m asl. Detailed geomorphological mapping of the deposits and geochemical analyses of the sediments revealed varying sources throughout the Holocene. The timing of the sediment deposition is based on 43 OSL (optical stimulated luminescence) ages. Several phases of enhanced aeolian deposition took place during the Holocene. The accumulation of aeolian sands lasted from 10.5 until 7 ka. The main source area of these sands was a large alluvial fan. Parallel to the formation of the dunes loess was deposited on the adjacent slopes from 10.5 until 7.5 ka. These sediments most probably originate in the nearby Qaidam Basin. In contrast to the general linkage of aeolian sediments to dryer climate conditions formation of these aeolian deposits is related to wetter conditions due to a strengthening of the Asian Summer Monsoons. The wetter climate enhanced the trapping and continuous fixation of the aeolian sediments by vegetation. With the further strengthening of the Monsoon fluvial processes eroded the aeolian deposits at least until 6 ka. From about 3 ka to the present a reactivation of aeolian sands and the formation of new dunes took place. This reactivation is related to drier conditions on the north-eastern Tibetan Plateau. Additionally, an increased human influence might have enhanced the aeolian activity. Similar phases of enhanced aeolian activity have been documented in more than 170 available OSL ages from loess and aeolian sands in northeastern Tibet. In the area of the Qinghai Lake enhanced accumulation of sand took place between 16 and 7 ka, while in the Gonghe Basin and the eastern Qaidam Basin sand was deposited between 13 and 7.5 ka. A late Holocene reactivation of sand similar to the Donggi catchment is only known from the Qinghai Lake area. The OSL ages of loess samples are generally younger than the ages of aeolian sand in northeastern Tibet. In the surrounding of the Qinghai Lake loess accumulation took place between 14.5 and 8ka while the loess ages from the eastern Qaidam Basin are mainly between 10.5 and 4.5 ka. In the Gonghe Basin only four ages of late Holocene ages are available. A different picture emerges from the northeastern margin of the study area. Loess accumulation on the northern slopes of the Qilian Shan occurred throughout the Holocene. In this area the nearby desert regions provide a more or less constant supply of silt-sized particles. In all other areas studied on the northeastern Tibetan Plateau the accumulation of aeolian sediments is primarily controlled by environmental conditions in the accumulation areas.
A late Holocene palaeoenvironmental record from Lake Tizong, northern Cameroon using diatom and carbon stable isotope analyses

NASA Astrophysics Data System (ADS)

Nguetsop, Victor François; Bentaleb, Ilham; Favier, Charly; Bietrix, Sophie; Martin, Céline; Servant-Vildary, Simone; Servant, Michel

2013-07-01

A late Holocene record, based on diatom and stable carbon isotopes from Lake Tizong, northern Cameroon, provides a history of environmental changes over the last 4100 years. Several coarser sediment layers among which the two younger ones are of pyroclastic origin interrupt the fine clayey sediment of the core. The detailed chronology of the core supported by 24 radiocarbon 14C dates and proxies data results revealed an erosive phase registered in the sedimentary column from 2200 to 1500 cal BP. The diatom ecological groups suggest that between 4100 and 2800 cal yrs BP, the lake level was much higher than after corresponding to a relatively greater precipitation minus evaporation (P - E) ratio, as well as increased runoff in the lake catchment. These conditions were favourable to the development of C3 plants in the lake catchment as indicated by lower δ13C values and higher C/N ratios than after. This hydrological phase is also characterized by eutrophic, turbid and probably circum-neutral to alkaline waters. After this episode, higher δ13C values between 2800 and 2500 cal BP suggest increased water use efficiency of terrestrial plants and/or potentially more C4 plant debris input into the lake: an indication of savannas patches developing, due probably to changes in the rainfall distribution. Marked lake-level declines are recorded at 2500, 2200-2100, and at 1400-1000 cal yrs BP. These low-stands are characterized by higher inputs of windblown diatoms (up to 4.2%) than before, which confirms that the NE trade-winds were strengthening. This corresponds primarily to a reduction in the P - E ratio, but probably also to greater inter-annual or seasonal variability when drier periods or seasons became more prolonged and intense than previously. Consequently, savannas were maintained as suggested by relatively higher than before δ13C values, as well as independently supported by regional pollen data. After 1000 cal BP, the lake-level rose towards sub-modern conditions, with a deep neutral and eutrophic water column. Carbon stable isotopes suggest a reduction of organic matter input, while savannas were maintained despite the return to more humid conditions. The trends of climatic changes observed in the Lake Tizong reveal the variability in timing, magnitude and regional extent of known climatic events.
The influences of the AMO and NAO on an Iberian alpine lake during the Late Holocene

NASA Astrophysics Data System (ADS)

Hernández, Armand; Leira, Manel; Trigo, Ricardo; Vázquez-Loureiro, David; Carballeira, Rafael; Sáez, Alberto

2017-04-01

High mountain lakes, usually oligotrophic, in the Iberian Peninsula are particularly sensitive to the influence of North Atlantic large-scale modes of climate variability due to their geographical position and the reduced direct anthropic disturbances. In this context, Serra da Estrela (Portugal), in the westernmost of the Sistema Central Range, constitutes a physical barrier to air masses coming from the Atlantic Ocean. However, long-term climate reconstructions have not yet been conducted. We present a climate reconstruction in terms of precipitation and temperature changes of this setting based on facies analysis, X-ray fluorescence core scanning, elemental and isotope geochemistry on bulk organic matter and a preliminary study of diatom assemblages from the sedimentary record of Lake Peixão (1677 m a.s.l.; Serra da Estrela) for the last ca. 3500 years. A multivariate statistical analysis has been performed to recognize the main environmental factors controlling the lake sedimentation. Our results reveal that two main processes explain 70% of the total variance, with PC1 (accumulation of siliciclastic material vs organic matter), and PC2 (variations in lacustrine productivity, related to nutrient inputs from the catchment), explaining 53% and 17% respectively. In mountain lakes, siliciclastic and/or external organic matter accumulation tend to be governed by the snowmelt which, in turn, are frequently controlled by winter and spring temperatures. On the other hand, lake productivity, usually limited by phosphorus and nitrogen, is dependent of internal recycling and/or external inputs, mainly by catchment leaching (climatically driven by summer precipitation) and atmospheric deposition (anthropic influence). The results from Lake Peixão have been compared to other Western Iberia and Northeastern Atlantic records, as well as the Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) indices. Thus, a tentative Late Holocene climate reconstruction from Western Iberia has been performed. Two relative colder phases (ca. 2500-2000 and 550-100 cal yrs BP) and two relative colder events (ca. 1380 and 1200 cal yrs BP) have been identified. These cold periods are likely influenced by negative NAO and AMO phases, whereas relative warmer conditions would be related periods in which NAO and AMO phases are both in positive phase. Additionally, five relative wetter phases (ca. 3600-2850; 2750-2500; 2200-2100; 1500-1400 and 400-150 cal yrs BP) have also been recognised. These relative wetter periods were usually linked to NAO and AMO both in negative phase, whereas background and relative drier conditions would be concurrent with NAO and AMO in positive phase. Hence, our results highlight that although the climate regime in this area is clearly influenced by the NAO, the slow-varying AMO also plays a key role at long-term time-scales. Publication supported by FCTproject UID/GEO/50019/2013 - Instituto Dom Luiz and Spanish Ministry of Economy and Competitiveness project RapidNAO (CGL2013-661 40608-R)
Paramedic Physical Demands Analysis

DTIC Science & Technology

2014-07-01

The five national sites included: British Columbia Ambulance Service (Vancouver, British Columbia - Metro catchment area ), Superior North Emergency...routinely drove within their assigned catchment area between calls, in addition to their driving duties on route to and from a call. Figure 10...been spent driving the ambulance roaming through their catchment area , seated in the ambulance or in a satellite station awaiting a call, or
Hydrologic processes and nutrient dynamics in a pristine mountain catchment

USGS Publications Warehouse

F. Richard Hauer,; Fagre, Daniel B.; Stanford, Jack A.

2002-01-01

Nutrient dynamics in watersheds have been used as an ecosystem-level indicator of overall ecosystem function or response to disturbance (e.g. Borman.N et al. 1974, WEBSTER et al. 1992). The examination of nutrients has been evaluated to determine responses to logging practices or other changes in watershed land use. Nutrient dynamics have been related to changing physical and biological characteristics (Mulholl AND 1992, CHESTNUT & McDowell 2000). Herein, the concentrations and dynamics of nitrogen, phosphorus and particulate organic carbon were examined in a large pristine watershed because they are affected by changes in discharge directly from the catchment and after passage through a large oligotrophic lake.
CDOM variations in Finnish lakes and rivers between 1913 and 2014.

PubMed

Arvola, Lauri; Leppäranta, Matti; Äijälä, Cecilia

2017-12-01

In lakes and rivers, the concentrations of dissolved organic carbon (DOC) and coloured dissolved organic matter (CDOM) are closely related. We analysed three large spectrophotometer data sets of Finnish inland waters from the years 1913-1914, 1913-1931 and 2014 for long-term changes in optical properties. The first data set consists of absorption spectra in the band 467-709nm of 212 filtered water samples, the second one contains 11-19years of data for seven rivers, and the third one contains 153 sites with high resolution spectra over the band 200-750nm. These data sets were supplemented with more recent monitoring data of DOC. The sites represent typical optical inland water types of north-eastern Europe. The results did not show any consistent large-scale changes in CDOM concentrations over the 101-year time period. The statistics of the absorption coefficients in 1913 and 2014 were almost identical, at 467nm they were 1.9±1.0m -1 in 1913 and 1.7±1.2m -1 in 2014, and the shape of the CDOM absorption spectrum was unchanged, proportional to exp(-S·λ), S=0.011nm -1 and λ is wavelength. Catchment properties, primarily lake and peat-land percentages, explained 50% of the variation of CDOM concentration in the lakes, and hydrological conditions explained 50% of the variation of CDOM in the rivers. Both illustrate the importance of catchments and hydrology to CDOM concentrations of boreal inland waters. Copyright © 2017 Elsevier B.V. All rights reserved.
Atmospheric deposition as a source of carbon and nutrients to an alpine catchment of the Colorado Rocky Mountains

NASA Astrophysics Data System (ADS)

Mladenov, N.; Williams, M. W.; Schmidt, S. K.; Cawley, K.

2012-08-01

Many alpine areas are experiencing deglaciation, biogeochemical changes driven by temperature rise, and changes in atmospheric deposition. There is mounting evidence that the water quality of alpine streams may be related to these changes, including rising atmospheric deposition of carbon (C) and nutrients. Given that barren alpine soils can be severely C limited, atmospheric deposition sources may be an important source of C and nutrients for these environments. We evaluated the magnitude of atmospheric deposition of C and nutrients to an alpine site, the Green Lake 4 catchment in the Colorado Rocky Mountains. Using a long-term dataset (2002-2010) of weekly atmospheric wet deposition and snowpack chemistry, we found that volume weighted mean dissolved organic carbon (DOC) concentrations were 1.12 ± 0.19 mg l-1, and weekly concentrations reached peaks as high at 6-10 mg l-1 every summer. Total dissolved nitrogen concentration also peaked in the summer, whereas total dissolved phosphorus and calcium concentrations were highest in the spring. To investigate potential sources of C in atmospheric deposition, we evaluated the chemical quality of dissolved organic matter (DOM) and relationships between DOM and other solutes in wet deposition. Relationships between DOC concentration, fluorescence, and nitrate and sulfate concentrations suggest that pollutants from nearby urban and agricultural sources and organic aerosols derived from sub-alpine vegetation may influence high summer DOC wet deposition concentrations. Interestingly, high DOC concentrations were also recorded during "dust-in-snow" events in the spring, which may reflect an association of DOM with dust. Detailed chemical and spectroscopic analyses conducted for samples collected in 2010 revealed that the DOM in many late spring and summer samples was less aromatic and polydisperse and of lower molecular weight than that of winter and fall samples. Our C budget estimates for the Green Lake 4 catchment illustrated that wet deposition (9.9 kg C ha-1 yr-1) and dry deposition (6.9 kg C ha-1 yr-1) were a combined input of approximately 17 kg C ha-1 yr-1, which could be as high as 24 kg C ha-1 yr-1 in high dust years. This atmospheric C input approached the C input from microbial autotrophic production in barren soils. Atmospheric wet and dry deposition also contributed 4.3 kg N ha-1 yr-1, 0.15 kg P ha-1 yr-1, and 2.7 kg Ca2+ ha-1 yr-1 to this alpine catchment.
Attributes for MRB_E2RF1 Catchments by Major River Basins in the Conterminous United States: Estimated Mean Annual Natural Groundwater Recharge, 2002

USGS Publications Warehouse

Wieczorek, Michael; LaMotte, Andrew E.

2010-01-01

This tabular data set represents the mean annual natural groundwater recharge, in millimeters, compiled for every MRB_E2RF1catchment of selected Major River Basins (MRBs, Crawford and others, 2006). The source data set is Estimated Mean Annual Natural Ground-Water Recharge in the Conterminous United States (Wolock, 2003). The MRB_E2RF1 catchments are based on a modified version of the U.S. Environmental Protection Agency's (USEPA) ERF1_2 and include enhancements to support national and regional-scale surface-water quality modeling (Nolan and others, 2002; Brakebill and others, 2011). Data were compiled for every MRB_E2RF1 catchment for the conterminous United States covering New England and Mid-Atlantic (MRB1), South Atlantic-Gulf and Tennessee (MRB2), the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy (MRB3), the Missouri (MRB4), the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf (MRB5), the Rio Grande, Colorado, and the Great basin (MRB6), the Pacific Northwest (MRB7) river basins, and California (MRB8).
Initial results from the ICDP SCOPSCO drilling project, Lake Ohrid (Macedonia, Albania)

NASA Astrophysics Data System (ADS)

Francke, A.; Wagner, B.; Krastel, S.; Lindhorst, K.; Wilke, T.; Zanchetta, G.; Sulpizio, R.; Grazhdani, A.; Reicherter, K. R.

2013-12-01

Lake Ohrid (Macedonia, Albania) is about 30 km long and 15 km wide and up to 290 m deep. Formed within a tectonic graben, Lake Ohrid is considered to be the oldest lake in Europe, providing a high-resolution, continuous archive of environmental change and tectonic and tephrostratigraphic history in the Eastern Mediterranean Region. The deep drilling campaign at Lake Ohrid in spring 2013 within the scope of the ICDP project SCOPSCO (Scientific Collaboration of Past Speciation Conditions in Lake Ohrid) aimed (a) to obtain more precise information about the age and origin of the lake, (b) to unravel the seismotectonic history of the lake area including effects of major earthquakes and associated mass wasting events, (c) to obtain a continuous record containing information on volcanic activities and climate changes in the central northern Mediterranean region, and (d) to better understand the impact of major geological/environmental events on general evolutionary patterns and shaping an extraordinary degree of endemic biodiversity as a matter of global significance. Drilling was carried out by DOSECC (Salt Lake City, USA) using the DLDS (Deep Lake Drilling System) with a hydraulic piston corer for surface sediments and rotation drilling for harder, deeper sediments. Overall, about 2,100 m of sediment were recovered from 4 drill sites. At the 'DEEP' site in the center of the lake, seismic data implied a maximum sediment fill of ca. 700 m, of which the uppermost 568 m sediment were recovered. Coarse-grained gravel and pebbles underlying clay and shallow water facies sediments hampered deeper penetration. 6 boreholes at the 'DEEP' site resulted in a total of 1526 m of sediment cores and a composite field recovery of 544 m (95%). Initial geochemical and magnetic susceptibility data imply that the sediments from 'DEEP' site are highly sensitive to climate and environmental variations in the Balkan area probably over the last 1.5 Mio years. Long-term climate oscillations on a glacial/interglacial timescale and also short-term events such as Dansgaard-Oescher cycles during the last glacial period can be inferred from the initial data. Although a high amount of greigite complicates the paleomagnetic dating of the recovered sediments, a robust age model can likely be inferred from numerous tephras and cryptotephras, which are indicated by spikes in the magnetic susceptibility data. Three additional sites at lateral parts of Lake Ohrid were drilled to un-ravel lake level fluctuations, catchment dynamics, biodiversity and evolution processes ('Cerava', deepest drilled depth: 90 m), active tectonics and spring dynamics ('Gradiste', deepest drilled depth: 123 m), and the early development of the Ohrid Basin ('Pestani', deepest drilled depth: 194 m). The composite field recovery is >90% at each site. The initial results obtained from the field campaign indicate that Lake Ohrid provides an extraordinary record of environmental change in the northern Mediterranean and will become a key site for a better understanding of speciation triggers.
Abrupt Shift in the Observed Runoff from the Southwest Greenland Ice Sheet?

NASA Astrophysics Data System (ADS)

Ahlstrom, A.; Petersen, D.; Box, J.; Langen, P. P.; Citterio, M.

2016-12-01

Mass loss of the Greenland ice sheet has contributed significantly to sea level rise in recent years and is considered a crucial parameter when estimating the impact of future climate change. Few observational records of sufficient length exist to validate surface mass balance models, especially the estimated runoff. Here we present an observation time series from 1975-2014 of discharge from a large proglacial lake, Tasersiaq, in West Greenland (66.3°N, 50.4°W) with a mainly ice-covered catchment. We argue that the discharge time series is representative measure of ice sheet runoff, making it the only observational record of runoff to exceed the 30-year period needed to assess the climatological state of the ice sheet. We proceed to isolate the runoff part of the signal from precipitation and identified glacial lake outburst floods from a small sub-catchment. Similarly, the impact from major volcanic eruptions is clearly identified. We examine the trend and annual variability in the annual discharge, relating it to likely atmospheric forcing mechanisms and compare the observational time series with modelled runoff from the regional climate model HIRHAM.
Use of a forest sapwood area index to explain long-term variability in mean annual evapotranspiration and streamflow in moist eucalypt forests

NASA Astrophysics Data System (ADS)

Benyon, Richard G.; Lane, Patrick N. J.; Jaskierniak, Dominik; Kuczera, George; Haydon, Shane R.

2015-07-01

Mean sapwood thickness, measured in fifteen 73 year old Eucalyptus regnans and E. delegatensis stands, correlated strongly with forest overstorey stocking density (R2 0.72). This curvilinear relationship was used with routine forest stocking density and basal area measurements to estimate sapwood area of the forest overstorey at various times in 15 research catchments in undisturbed and disturbed forests located in the Great Dividing Range, Victoria, Australia. Up to 45 years of annual precipitation and streamflow data available from the 15 catchments were used to examine relationships between mean annual loss (evapotranspiration estimated as mean annual precipitation minus mean annual streamflow), and sapwood area. Catchment mean sapwood area correlated strongly (R2 0.88) with catchment mean annual loss. Variation in sapwood area accounted for 68% more variation in mean annual streamflow than precipitation alone (R2 0.90 compared with R2 0.22). Changes in sapwood area accounted for 96% of the changes in mean annual loss observed after forest thinning or clear-cutting and regeneration. We conclude that forest inventory data can be used reliably to predict spatial and temporal variation in catchment annual losses and streamflow in response to natural and imposed disturbances in even-aged forests. Consequently, recent advances in mapping of sapwood area using airborne light detection and ranging will enable high resolution spatial and temporal mapping of mean annual loss and mean annual streamflow over large areas of forested catchment. This will be particularly beneficial in management of water resources from forested catchments subject to disturbance but lacking reliable long-term (years to decades) streamflow records.
Attributes for MRB_E2RF1 Catchments by Major River Basins in the Conterminous United States: Average Atmospheric (Wet) Deposition of Inorganic Nitrogen, 2002

USGS Publications Warehouse

Wieczorek, Michael; LaMotte, Andrew E.

2010-01-01

This tabular data set represents the average atmospheric (wet) deposition, in kilograms per square kilometer, of inorganic nitrogen for the year 2002 compiled for every catchment for MRB_E2RF1 of Major River Basins (MRBs, Crawford and others, 2006). The source data set for wet deposition was from the USGS's raster data set atmospheric (wet) deposition of inorganic nitrogen for 2002 (Gronberg, 2005). The MRB_E2RF1 catchments are based on a modified version of the U.S. Environmental Protection Agency's (USEPA) ERF1_2 and include enhancements to support national and regional-scale surface-water quality modeling (Nolan and others, 2002; Brakebill and others, 2011). Data were compiled for every catchment of MRB_E2RF1 catchments for the conterminous United States covering New England and Mid-Atlantic (MRB1), South Atlantic-Gulf and Tennessee (MRB2), the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy (MRB3), the Missouri (MRB4), the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf (MRB5), the Rio Grande, Colorado, and the Great basin (MRB6), the Pacific Northwest (MRB7) river basins, and California (MRB8).
Influence of hydroclimatic variations on solute concentration dynamics in nested subtropical catchments with heterogeneous landscapes.

PubMed

Piazza, Gustavo Antonio; Dupas, Rémi; Gascuel-Odoux, Chantal; Grimaldi, Catherine; Pinheiro, Adilson; Kaufmann, Vander

2018-04-20

Despite global efforts to monitor water quality in catchments worldwide, tropical and subtropical zones still lack data to study the influence of human activities and climate variations on solute dynamics. In this study, we monitored ten solutes every two weeks for six years (2010-2015) in three nested catchments (2 to30 km 2 ), which contained heterogeneous landscapes composed of forests and agricultural land, and one small neighboring forested catchment (0.4 km 2 ). Data analysis revealed that i) rainfall, discharge and solute concentrations displayed no clear seasonal patterns, unlike many catchments of the temperate zone; ii) solute concentrations in the agricultural area were higher than those in the forested area, but both areas displayed similar temporal patterns due to a common hydroclimatic driver; iii) all four catchments displayed a chemostatic export regime for most of the solutes, similar to catchments of the temperate zone; and iv) a positive correlation was observed between anion concentrations and ENSO (El Niño-Southern Oscillation) index. ENSO appeared to influence both hydroclimatic and anion dynamics in these subtropical catchments. Copyright © 2018 Elsevier B.V. All rights reserved.
Using a Data-Driven Approach to Understand the Interaction between Catchment Characteristics and Water Quality Responses

NASA Astrophysics Data System (ADS)

Western, A. W.; Lintern, A.; Liu, S.; Ryu, D.; Webb, J. A.; Leahy, P.; Wilson, P.; Waters, D.; Bende-Michl, U.; Watson, M.

2016-12-01

Many streams, lakes and estuaries are experiencing increasing concentrations and loads of nutrient and sediments. Models that can predict the spatial and temporal variability in water quality of aquatic systems are required to help guide the management and restoration of polluted aquatic systems. We propose that a Bayesian hierarchical modelling framework could be used to predict water quality responses over varying spatial and temporal scales. Stream water quality data and spatial data of catchment characteristics collected throughout Victoria and Queensland (in Australia) over two decades will be used to develop this Bayesian hierarchical model. In this paper, we present the preliminary exploratory data analysis required for the development of the Bayesian hierarchical model. Specifically, we present the results of exploratory data analysis of Total Nitrogen (TN) concentrations in rivers in Victoria (in South-East Australia) to illustrate the catchment characteristics that appear to be influencing spatial variability in (1) mean concentrations of TN; and (2) the relationship between discharge and TN throughout the state. These important catchment characteristics were identified using: (1) monthly TN concentrations measured at 28 water quality gauging stations and (2) climate, land use, topographic and geologic characteristics of the catchments of these 28 sites. Spatial variability in TN concentrations had a positive correlation to fertiliser use in the catchment and average temperature. There were negative correlations between TN concentrations and catchment forest cover, annual runoff, runoff perenniality, soil erosivity and catchment slope. The relationship between discharge and TN concentrations showed spatial variability, possibly resulting from climatic and topographic differences between the sites. The results of this study will feed into the hierarchical Bayesian model of river water quality.
Analysing the impact of urban areas patterns on the mean annual flow of 43 urbanized catchments

NASA Astrophysics Data System (ADS)

Salavati, B.; Oudin, L.; Furusho, C.; Ribstein, P.

2015-06-01

It is often argued that urban areas play a significant role in catchment hydrology, but previous studies reported disparate results of urbanization impacts on stream flow. This might stem either from the difficulty to quantify the historical flow changes attributed to urbanization only (and not climate variability) or from the inability to decipher what type of urban planning is more critical for flows. In this study, we applied a hydrological model on 43 urban catchments in the United States to quantify the flow changes attributable to urbanization. Then, we tried to relate these flow changes to the changes of urban/impervious areas of the catchments. We argue that these spatial changes of urban areas can be more precisely characterized by landscape metrics, which enable analysing the patterns of historical urban growth. Landscape metrics combine the richness (the number) and evenness (the spatial distribution) of patch types represented on the landscape. Urbanization patterns within the framework of patch analysis have been widely studied but, to our knowledge, previous research works had not linked them to catchments hydrological behaviours. Our results showed that the catchments with larger impervious areas and larger mean patch areas are likely to have larger increase of runoff yield.
Lead and Lags of Lake System Responses to Late Allerød and Early Younger Dryas Climatic Fluctuation - an Example from Varved Lake Sediments from Northern Poland (Central Europe)

NASA Astrophysics Data System (ADS)

Slowinski, M. M.; Zawiska, I.; Ott, F.; Noryśkiewicz, A. M.; Plessen, B.; Apolinarska, K.; Lutyńska, M.; Michczynska, D. J.; Wulf, S.; Skubała, P.; Błaszkiewicz, M.; Brauer, A.

2014-12-01

The transition from the warmer Allerød to the cooler Younger Dryas period is well understood to represent sudden and extreme climate changes during the end of the last glaciation. Thus, lake sediment studies within paleoclimatic and paleoecological research on this transition are ideal to enhance the knowledge about "lead and lags" of lake system responses to abrupt climate changes through applying multi-proxy sediment analyses. In this study, we present the results of high-resolution studies on varved late glacial sediments from the Trzechowskie paleolake, located in the northern Poland (center Europe). High-resolution bio-proxies (pollen, macrofossils, Cladocera and diatoms), geochemical analyses (µ-XRF data, TOC, C/N ratios, δ18Ocarb and δ13Corg stable isotopes) and a robust chronology based on varve counting, AMS 14C dating and tephrochronology were used to reconstruct the lake system responses to rapid climatic and environmental changes of Trzechowskie paleolake during the late Allerød - Younger Dryas transition. Paleoecological and geochemical analyses, which were carried out in a 4 to 16 years temporal sample resolution, allowed to defining short-termed shifts of the ecosystem that were triggered by abrupt climate changes. The rapid and pronounced cooling at the beginning of the Younger Dryas had a major impact on the lake and its catchment as clearly reflected by not synchronous changes of both, biotic and geochemical proxies. The results of high-resolution analysis indicate (a) an increased precipitation during the Allerød-YD transition, which is responsible for an increase of soil erosion in the catchment during this period, (b) a delayed response of the vegetation compared to the lake depositional system at the YD onset of 20 years, and (c) a non-synchronicity of vegetation responses between Western (Lake Meerfelder Maar) and Eastern European sites (Trzechowskie palaeolake) at the YD onset. This study is a contribution to the Virtual Institute ICLEA (Integrated Climate and Landscape Evolution Analysis) funded by the Helmholtz Association. The research was supported by the National Science Centre Poland (grants No. NN 306085037 and NCN 2011/01/B/ST10/07367).

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