Hydrometeorology as an Inversion Problem: Can River Discharge Observations Improve the Atmosphere by Ensemble Data Assimilation?

NASA Astrophysics Data System (ADS)

Sawada, Yohei; Nakaegawa, Tosiyuki; Miyoshi, Takemasa

2018-01-01

We examine the potential of assimilating river discharge observations into the atmosphere by strongly coupled river-atmosphere ensemble data assimilation. The Japan Meteorological Agency's Non-Hydrostatic atmospheric Model (JMA-NHM) is first coupled with a simple rainfall-runoff model. Next, the local ensemble transform Kalman filter is used for this coupled model to assimilate the observations of the rainfall-runoff model variables into the JMA-NHM model variables. This system makes it possible to do hydrometeorology backward, i.e., to inversely estimate atmospheric conditions from the information of river flows or a flood on land surfaces. We perform a proof-of-concept Observing System Simulation Experiment, which reveals that the assimilation of river discharge observations into the atmospheric model variables can improve the skill of the short-term severe rainfall forecast.

One-dimensional modelling of the interactions between heavy rainfall-runoff in an urban area and flooding flows from sewer networks and rivers.

PubMed

Kouyi, G Lipeme; Fraisse, D; Rivière, N; Guinot, V; Chocat, B

2009-01-01

Many investigations have been carried out in order to develop models which allow the linking of complex physical processes involved in urban flooding. The modelling of the interactions between overland flows on streets and flooding flows from rivers and sewer networks is one of the main objectives of recent and current research programs in hydraulics and urban hydrology. This paper outlines the original one-dimensional linking of heavy rainfall-runoff in urban areas and flooding flows from rivers and sewer networks under the RIVES project framework (Estimation of Scenario and Risks of Urban Floods). The first part of the paper highlights the capacity of Canoe software to simulate the street flows. In the second part, we show the original method of connection which enables the modelling of interactions between processes in urban flooding. Comparisons between simulated results and the results of Despotovic et al. or Gomez & Mur show a good agreement for the calibrated one-dimensional connection model. The connection operates likes a manhole with the orifice/weir coefficients used as calibration parameters. The influence of flooding flows from river was taken into account as a variable water depth boundary condition.

Trend and variability in western and central Africa streamflow, and their relation to climate variability between 1950 and 2010

NASA Astrophysics Data System (ADS)

Sidibe, Moussa; Dieppois, Bastien; Mahé, Gil; Paturel, Jean-Emmanuel; Rouché, Nathalie; Amoussou, Ernest; Anifowose, Babatunde; Lawler, Damian

2017-04-01

Unprecedented drought episodes that struck western and central Africa between the late 1960s and 1980s. This triggered many studies investigating rainfall variability and its impacts on food production systems. However, most studies were focused at the catchment scale. In this study, we examine how rainfall variability has impacted on river flow at the subcontinental scale between 1950 and 2010, as well as the key large-scale controls on this relationship. For the first time, we establish a complete, gap-filled, monthly streamflow data set, which extends from 1950 to 2010, over the western and central African region. To achieve this, we used linear regression modelling across and between 600 flow gauging stations (see initial database information at http://www.hydrosciences.fr/sierem/index_en.htm). Streamflow trend and variability are then seasonally assessed at this subcontinental scale and compared to those observed in three different rainfall data sets (i.e. CRU TS3.24, GPCC V7, IRD-HSM). Long-term trends and variability in streamflow are mainly consistent with trends in rainfall. However, these relationships may have been moderated by: i) changes in land use; and ii) contributions from groundwater resources. In particular, we note that the recent post 1990s partial recovery in Sahel rainfall could have, at least partially, positively impacted river flows (e.g. the Senegal and Niger rivers). Using multi-temporal trend and continuous wavelet analysis, the time-evolution of western and central African river flows are analysed, and are all characterized by very strong decadal fluctuations, which can be interpreted as modulations in the baseflow. These decadal fluctuations, which are also significantly detected in rainfall, are likely related to large-scale sea-surface temperature (SST) anomaly patterns, such as the tropical Atlantic SST variability, the Atlantic Multidecadal Oscillation, the Interdecadal Pacific Oscillation and/or the Pacific Decadal Oscillation. Furthermore, hitherto-poorly understood hydroclimatic processes related to these teleconnections at decadal timescales will be examined in this study. Influences of the catchment properties (e.g. size, shape, vegetation and landuse cover, soil type, ground-water level, direction of stream flow across climate zones) on these decadal fluctuations in river flows will also be assessed. This study therefore aims to improve the ability of current regional and global climate models to simulate such ranges of variability, to significantly improve regional hydroclimate understanding, as a means for improving the development of future scenarios for water resources in western and central Africa.

Investigating the spatio-temporal variability in groundwater and surface water interactions: a multi-technical approach

NASA Astrophysics Data System (ADS)

Unland, N. P.; Cartwright, I.; Andersen, M. S.; Rau, G. C.; Reed, J.; Gilfedder, B. S.; Atkinson, A. P.; Hofmann, H.

2013-03-01

The interaction between groundwater and surface water along the Tambo and Nicholson Rivers, southeast Australia, was investigated using 222Rn, Cl, differential flow gauging, head gradients, electrical conductivity (EC) and temperature profiling. Head gradients, temperature profiles, Cl concentrations and 222Rn activities all indicate higher groundwater fluxes to the Tambo River in areas of increased topographic variation where the potential to form large groundwater-surface water gradients is greater. Groundwater discharge to the Tambo River calculated by Cl mass balance was significantly lower (1.48 × 104 to 1.41 × 103 m3 day-1) than discharge estimated by 222Rn mass balance (5.35 × 105 to 9.56 × 103 m3 day-1) and differential flow gauging (5.41 × 105 to 6.30 × 103 m3 day-1). While groundwater sampling from the bank of the Tambo River was intended to account for the variability in groundwater chemistry associated with river-bank interaction, the spatial variability under which these interactions occurs remained unaccounted for, limiting the use of Cl as an effective tracer. Groundwater discharge to both the Tambo and Nicholson Rivers was the highest under high flow conditions in the days to weeks following significant rainfall, indicating that the rivers are well connected to a groundwater system that is responsive to rainfall. Groundwater constituted the lowest proportion of river discharge during times of increased rainfall that followed dry periods, while groundwater constituted the highest proportion of river discharge under baseflow conditions (21.4% of the Tambo in April 2010 and 18.9% of the Nicholson in September 2010).

Data-based information gain on the response behaviour of hydrological models at catchment scale

NASA Astrophysics Data System (ADS)

Willems, Patrick

2013-04-01

A data-based approach is presented to analyse the response behaviour of hydrological models at the catchment scale. The approach starts with a number of sequential time series processing steps, applied to available rainfall, ETo and river flow observation series. These include separation of the high frequency (e.g., hourly, daily) river flow series into subflows, split of the series in nearly independent quick and slow flow hydrograph periods, and the extraction of nearly independent peak and low flows. Quick-, inter- and slow-subflow recession behaviour, sub-responses to rainfall and soil water storage are derived from the time series data. This data-based information on the catchment response behaviour can be applied on the basis of: - Model-structure identification and case-specific construction of lumped conceptual models for gauged catchments; or diagnostic evaluation of existing model structures; - Intercomparison of runoff responses for gauged catchments in a river basin, in order to identify similarity or significant differences between stations or between time periods, and relate these differences to spatial differences or temporal changes in catchment characteristics; - (based on the evaluation of the temporal changes in previous point:) Detection of temporal changes/trends and identification of its causes: climate trends, or land use changes; - Identification of asymptotic properties of the rainfall-runoff behaviour towards extreme peak or low flow conditions (for a given catchment) or towards extreme catchment conditions (for regionalization, ungauged basin prediction purposes); hence evaluating the performance of the model in making extrapolations beyond the range of available stations' data; - (based on the evaluation in previous point:) Evaluation of the usefulness of the model for making extrapolations to more extreme climate conditions projected by for instance climate models. Examples are provided for river basins in Belgium, Ethiopia, Kenya, Ecuador, Bolivia and China. References: Van Steenbergen, N., Willems, P. (2012), 'Method for testing the accuracy of rainfall-runoff models in predicting peak flow changes due to rainfall changes, in a climate changing context', Journal of Hydrology, 414-415, 425-434, doi:10.1016/j.jhydrol.2011.11.017 Mora, D., Willems, P. (2012), 'Decadal oscillations in rainfall and air temperature in the Paute River Basin - Southern Andes of Ecuador', Theoretical and Applied Climatology, 108(1), 267-282, doi:0.1007/s00704-011-0527-4 Taye, M.T., Willems, P. (2011). 'Influence of climate variability on representative QDF predictions of the upper Blue Nile Basin', Journal of Hydrology, 411, 355-365, doi:10.1016/j.jhydrol.2011.10.019 Taye, M.T., Willems, P. (2012). 'Temporal variability of hydro-climatic extremes in the Blue Nile basin', Water Resources Research, 48, W03513, 13p. Vansteenkiste, Th., Tavakoli, M., Ntegeka, V., Willems, P., De Smedt, F., Batelaan, O. (in press), 'Climate change impact on river flows and catchment hydrology: a comparison of two spatially distributed models', Hydrological Processes; doi: 10.1002/hyp.9480 [in press

Regularized joint inverse estimation of extreme rainfall amounts in ungauged coastal basins of El Salvador

USGS Publications Warehouse

Friedel, M.J.

2008-01-01

A regularized joint inverse procedure is presented and used to estimate the magnitude of extreme rainfall events in ungauged coastal river basins of El Salvador: Paz, Jiboa, Grande de San Miguel, and Goascoran. Since streamflow measurements reflect temporal and spatial rainfall information, peak-flow discharge is hypothesized to represent a similarity measure suitable for regionalization. To test this hypothesis, peak-flow discharge values determined from streamflow recurrence information (10-year, 25-year, and 100-year) collected outside the study basins are used to develop regional (country-wide) regression equations. Peak-flow discharge derived from these equations together with preferred spatial parameter relations as soft prior information are used to constrain the simultaneous calibration of 20 tributary basin models. The nonlinear range of uncertainty in estimated parameter values (1 curve number and 3 recurrent rainfall amounts for each model) is determined using an inverse calibration-constrained Monte Carlo approach. Cumulative probability distributions for rainfall amounts indicate differences among basins for a given return period and an increase in magnitude and range among basins with increasing return interval. Comparison of the estimated median rainfall amounts for all return periods were reasonable but larger (3.2-26%) than rainfall estimates computed using the frequency-duration (traditional) approach and individual rain gauge data. The observed 25-year recurrence rainfall amount at La Hachadura in the Paz River basin during Hurricane Mitch (1998) is similar in value to, but outside and slightly less than, the estimated rainfall confidence limits. The similarity in joint inverse and traditionally computed rainfall events, however, suggests that the rainfall observation may likely be due to under-catch and not model bias. ?? Springer Science+Business Media B.V. 2007.

Concurrency and climate change signal in Scottish flooding

NASA Astrophysics Data System (ADS)

Harding, A. E.; Butler, A.; Goody, N.; Bertram, D.; Baggaley, N.; Tett, S. F.

2013-12-01

The Scottish Environment Protection Agency maintains a database of river gauging stations and intensity rain-gauges with a 3-hourly resolution that covers the majority of Scotland. Both SEPA and a number of other Scottish agencies are invested in climate change attribution in this data set. SEPA's main interest lies in trend detection and changes in river level (';stage') data throughout Scotland. Emergency response teams are more concerned with the concurrency of multiple flood events that might stretch their ability to respond effectively. Unfortunately, much of the rainfall signal within SEPA's river-gauge data is altered by land use changes, modified by artificial interventions such as reservoirs, compromised by tidal flow, or obscured by measurement issues. Data reduction techniques, indices of extreme rainfall, and hydrology-driven discrimination have been employed to produce a reduced set of flood-relevant information for 24-hour ';flashy' events. Links between this set and North Atlantic circulation have been explored, as have patterns of mutual occurrence across Scotland and location- and seasonally- dependent trends through time. Both frontal systems and summer convective storms have been characterised in terms of subsequent flood-inducing flow regime, their changing behaviour over the last fifty years, and their spatial extent. This is the first stage of an ongoing project that will intelligently expand to take less robust river and rain-gauge stations into account through statistical analysis and hydrological modelling. It is also the first study of its type to analyse a nation-scale dataset of both rainfall and river flow from multiple catchments for flood event concurrency. As rainfall events are expected to intensify across much of Europe, this kind of research is likely to have an increasing degree of relevance for policy-makers. This project demonstrates that productive, policy-relevant and mutually-rewarding partnerships are already underway.

Including local rainfall dynamics and uncertain boundary conditions into a 2-D regional-local flood modelling cascade

NASA Astrophysics Data System (ADS)

Bermúdez, María; Neal, Jeffrey C.; Bates, Paul D.; Coxon, Gemma; Freer, Jim E.; Cea, Luis; Puertas, Jerónimo

2016-04-01

Flood inundation models require appropriate boundary conditions to be specified at the limits of the domain, which commonly consist of upstream flow rate and downstream water level. These data are usually acquired from gauging stations on the river network where measured water levels are converted to discharge via a rating curve. Derived streamflow estimates are therefore subject to uncertainties in this rating curve, including extrapolating beyond the maximum observed ratings magnitude. In addition, the limited number of gauges in reach-scale studies often requires flow to be routed from the nearest upstream gauge to the boundary of the model domain. This introduces additional uncertainty, derived not only from the flow routing method used, but also from the additional lateral rainfall-runoff contributions downstream of the gauging point. Although generally assumed to have a minor impact on discharge in fluvial flood modeling, this local hydrological input may become important in a sparse gauge network or in events with significant local rainfall. In this study, a method to incorporate rating curve uncertainty and the local rainfall-runoff dynamics into the predictions of a reach-scale flood inundation model is proposed. Discharge uncertainty bounds are generated by applying a non-parametric local weighted regression approach to stage-discharge measurements for two gauging stations, while measured rainfall downstream from these locations is cascaded into a hydrological model to quantify additional inflows along the main channel. A regional simplified-physics hydraulic model is then applied to combine these inputs and generate an ensemble of discharge and water elevation time series at the boundaries of a local-scale high complexity hydraulic model. Finally, the effect of these rainfall dynamics and uncertain boundary conditions are evaluated on the local-scale model. Improvements in model performance when incorporating these processes are quantified using observed flood extent data and measured water levels from a 2007 summer flood event on the river Severn. The area of interest is a 7 km reach in which the river passes through the city of Worcester, a low water slope, subcritical reach in which backwater effects are significant. For this domain, the catchment area between flow gauging stations extends over 540 km2. Four hydrological models from the FUSE framework (Framework for Understanding Structural Errors) were set up to simulate the rainfall-runoff process over this area. At this regional scale, a 2-dimensional hydraulic model that solves the local inertial approximation of the shallow water equations was applied to route the flow, whereas the full form of these equations was solved at the local scale to predict the urban flow field. This nested approach hence allows an examination of water fluxes from the catchment to the building scale, while requiring short setup and computational times. An accurate prediction of the magnitude and timing of the flood peak was obtained with the proposed method, in spite of the unusual structure of the rain episode and the complexity of the River Severn system. The findings highlight the importance of estimating boundary condition uncertainty and local rainfall contribution for accurate prediction of river flows and inundation.

Investigating the spatio-temporal variability in groundwater and surface water interactions: a multi-technique approach

NASA Astrophysics Data System (ADS)

Unland, N. P.; Cartwright, I.; Andersen, M. S.; Rau, G. C.; Reed, J.; Gilfedder, B. S.; Atkinson, A. P.; Hofmann, H.

2013-09-01

The interaction between groundwater and surface water along the Tambo and Nicholson rivers, southeast Australia, was investigated using 222Rn, Cl, differential flow gauging, head gradients, electrical conductivity (EC) and temperature profiles. Head gradients, temperature profiles, Cl concentrations and 222Rn activities all indicate higher groundwater fluxes to the Tambo River in areas of increased topographic variation where the potential to form large groundwater-surface water gradients is greater. Groundwater discharge to the Tambo River calculated by Cl mass balance was significantly lower (1.48 × 104 to 1.41 × 103 m3 day-1) than discharge estimated by 222Rn mass balance (5.35 × 105 to 9.56 × 103 m3 day-1) and differential flow gauging (5.41 × 105 to 6.30 × 103 m3 day-1) due to bank return waters. While groundwater sampling from the bank of the Tambo River was intended to account for changes in groundwater chemistry associated with bank infiltration, variations in bank infiltration between sample sites remain unaccounted for, limiting the use of Cl as an effective tracer. Groundwater discharge to both the Tambo and Nicholson rivers was the highest under high-flow conditions in the days to weeks following significant rainfall, indicating that the rivers are well connected to a groundwater system that is responsive to rainfall. Groundwater constituted the lowest proportion of river discharge during times of increased rainfall that followed dry periods, while groundwater constituted the highest proportion of river discharge under baseflow conditions (21.4% of the Tambo in April 2010 and 18.9% of the Nicholson in September 2010).

Hydrological impacts of climate change on the Tejo and Guadiana Rivers

NASA Astrophysics Data System (ADS)

Kilsby, C. G.; Tellier, S. S.; Fowler, H. J.; Howels, T. R.

2007-05-01

A distributed daily rainfall runoff model is applied to the Tejo and Guadiana river basins in Spain and Portugal to simulate the effects of climate change on runoff production, river flows and water resource availability with results aggregated to the monthly level. The model is calibrated, validated and then used for a series of climate change impact assessments for the period 2070 2100. Future scenarios are derived from the HadRM3H regional climate model (RCM) using two techniques: firstly a bias-corrected RCM output, with monthly mean correction factors calculated from observed rainfall records; and, secondly, a circulation-pattern-based stochastic rainfall model. Major reductions in rainfall and streamflow are projected throughout the year; these results differ from those for previous studies where winter increases are projected. Despite uncertainties in the representation of heavily managed river systems, the projected impacts are serious and pose major threats to the maintenance of bipartite water treaties between Spain and Portugal and the supply of water to urban and rural regions of Portugal.

River flow modeling using artificial neural networks in Kapuas river, West Kalimantan, Indonesia

NASA Astrophysics Data System (ADS)

Herawati, Henny; Suripin, Suharyanto

2017-11-01

Kapuas River is located in the province of West Kalimantan. Kapuas river length is 1,086 km and river basin areas about 100,000 Km2. The availability of river flow data in the Long River and very wide catchments are difficult to obtain, while river flow data are essential for planning waterworks. To predict the water flow in the catchment area requires a lot of hydrology coefficient, so it is very difficult to predict and obtain results that closer to the real conditions. This paper demonstrates that artificial neural network (ANN) could be used to predict the water flow. The ANN technique can be used to predict the incidence of water discharge that occurs in the Kapuas River based on rainfall and evaporation data. With the data available to do training on the artificial neural network model is obtained mean square error (MSE) 0.00007. The river flow predictions could be carried out after the training. The results showed differences in water discharge measurement and prediction of about 4%.

Discharge variability and bedrock river incision on the Hawaiian island of Kaua'i

NASA Astrophysics Data System (ADS)

Huppert, K.; Deal, E.; Perron, J. T.; Ferrier, K.; Braun, J.

2017-12-01

Bedrock river incision occurs during floods that generate sufficient shear stress to strip riverbeds of sediment cover and erode underlying bedrock. Thresholds for incision can prevent erosion at low flows and slow down erosion at higher flows that do generate excess shear stress. Because discharge distributions typically display power-law tails, with non-negligible frequencies of floods much greater than the mean, models incorporating stochastic discharge and incision thresholds predict that discharge variability can sometimes have greater effects on long-term incision rates than mean discharge. This occurs when the commonly observed inverse scalings between mean discharge and discharge variability are weak or when incision thresholds are high. Because the effects of thresholds and discharge variability have only been documented in a few locations, their influence on long-term river incision rates remains uncertain. The Hawaiian island of Kaua'i provides an ideal natural laboratory to evaluate the effects of discharge variability and thresholds on bedrock river incision because it has one of Earth's steepest spatial gradients in mean annual rainfall and it also experiences dramatic spatial variations in rainfall and discharge variability, spanning a wide range of the conditions reported on Earth. Kaua'i otherwise has minimal variations in lithology, vertical motion, and other factors that can influence erosion. River incision rates averaged over 1.5 - 4.5 Myr timescales can be estimated along the lengths of Kauaian channels from the depths of river canyons and lava flow ages. We characterize rainfall and discharge variability on Kaua'i using records from an extensive network of rain and stream gauges spanning the past century. We use these characterizations to model long-term bedrock river incision along Kauaian channels with a threshold-dependent incision law, modulated by site-specific discharge-channel width scalings. Our comparisons between modeled and observed erosion rates suggest that variations in river incision rates on Kaua'i are dominated by variations in mean rainfall and discharge, rather than by differences in storminess across the island. We explore the implications of this result for the threshold dependence of river incision across Earth's varied climates.

Debris flows in Grand Canyon National Park, Arizona: magnitude, frequency and effects on the Colorado River

USGS Publications Warehouse

Melis, Theodre S.; Webb, Robert H.; ,

1993-01-01

Debris flows are recurrent sediment-transport processes in 525 tributaries of the Colorado River in Grand Canyon. Arizona. Initiated by slope failures in bedrock and (or) colluvium during intense rainfall, Grand Canyon debris flows are high-magnitude, short-duration floods. Debris flows in these tributaries transport very large boulders into the river where they accumulate on debris fans and form rapids. The frequency of debris flows range from less than 1 per century to 10 or more per century in these tributaries. Before regulation by Glen Canyon Dam in 1963, high-magnitude floods on the Colorado River reworked debris fans by eroding all particles except large boulders. Because flow regulation has substantially decreased the river's competence, debris flows occurring after 1963 have increased accumulation of finer-grained sediments on debris fans and in rapids.

Trend and variability in western and central Africa streamflow, and major drivers of variability between 1950 and 2005

NASA Astrophysics Data System (ADS)

Dieppois, B.; Sidibe, M.; Mahe, G. M.; Paturel, J. E.; Anifowose, B. A.; Lawler, D.; Amoussou, E.

2017-12-01

Unprecedented drought episodes that struck western and central Africa between the late 1960s and 1980s, triggered many studies investigating rainfall variability and its impacts on water resources and food production systems. However, most studies were focused at the catchment scale. In this study, we aim at investigating the key large-scale controls determining and modulating climate-river flows relationships at the subcontinental scale between 1950 and 2005. Using the first complete monthly streamflow data set (1950-2005) over western and central Africa, streamflow trend and variability are seasonally assessed at this subcontinental scale and compared to those observed in other hydroclimatic variables (precipitation, temperature and potential evapotranspiration). Long-term trends and variability in streamflow are mainly consistent with trends in rainfall. In particular, the recent post-1990s partial recovery in Sahel rainfall could have, at least partially, positively impacted river flows (e.g. the Senegal and Niger rivers). However, these relationships may have been moderated by: i) changes in land use; and ii) contributions from groundwater resources. In addition, the time-evolution of river flows is shown to be primarily driven by very strong decadal fluctuations, which can be interpreted as modulations in the baseflow, as determined using multi-temporal trend and continuous wavelet analysis. These decadal fluctuations, which are also significantly detected in rainfall, are likely related to large-scale sea-surface temperature (SST) anomaly patterns (such as the tropical Atlantic SST variability, the Atlantic Multidecadal Oscillation, the Interdecadal Pacific Oscillation and the Pacific Decadal Oscillation), which are together modulating the West African monsoon. Furthermore, influences of the catchment properties (e.g. size, vegetation and land use cover, soil properties, direction of stream flow across climate zones) on these decadal fluctuations in river flows have been examined. This study therefore aims to improve the ability of current global to regional climate models to simulate such ranges of variability and understand regional hydroclimate, as a means for improving the development of future scenarios for water resources in western and central Africa.

Variability in rainfall at monitoring stations and derivation of a long-term rainfall intensity record in the Grand Canyon Region, Arizona, USA

USGS Publications Warehouse

Caster, Joshua J.; Sankey, Joel B.

2016-04-11

In this study, we examine rainfall datasets of varying temporal length, resolution, and spatial distribution to characterize rainfall depth, intensity, and seasonality for monitoring stations along the Colorado River within Marble and Grand Canyons. We identify maximum separation distances between stations at which rainfall measurements might be most useful for inferring rainfall characteristics at other locations. We demonstrate a method for applying relations between daily rainfall depth and intensity, from short-term high-resolution data to lower-resolution longer-term data, to synthesize a long-term record of daily rainfall intensity from 1950–2012. We consider the implications of our spatio-temporal characterization of rainfall for understanding local landscape change in sedimentary deposits and archaeological sites, and for better characterizing past and present rainfall and its potential role in overland flow erosion within the canyons. We find that rainfall measured at stations within the river corridor is spatially correlated at separation distances of tens of kilometers, and is not correlated at the large elevation differences that separate stations along the Colorado River from stations above the canyon rim. These results provide guidance for reasonable separation distances at which rainfall measurements at stations within the Grand Canyon region might be used to infer rainfall at other nearby locations along the river. Like other rugged landscapes, spatial variability between rainfall measured at monitoring stations appears to be influenced by canyon and rim physiography and elevation, with preliminary results suggesting the highest elevation landform in the region, the Kaibab Plateau, may function as an important orographic influence. Stations at specific locations within the canyons and along the river, such as in southern (lower) Marble Canyon and eastern (upper) Grand Canyon, appear to have strong potential to receive high-intensity rainfall that can generate runoff which may erode alluvium. The characterization of past and present rainfall variability in this study will be useful for future studies that evaluate more spatially continuous datasets in order to better understand the rainfall dynamics within this, and potentially other, deep canyons.

Effects of Stormwater and Snowmelt Runoff on ELISA-EQ Concentrations of PCDD/PCDF and Triclosan in an Urban River

PubMed Central

Urbaniak, Magdalena; Tygielska, Adrianna; Krauze, Kinga; Mankiewicz-Boczek, Joanna

2016-01-01

The aim of the study was to determine the effects of stormwater and snowmelt runoff on the ELISA EQ PCDD/PCDF and triclosan concentrations in the small urban Sokołówka River (Central Poland). The obtained results demonstrate the decisive influence of hydrological conditions occurring in the river itself and its catchment on the quoted PCDD/PCDF ELISA EQ concentrations. The lowest PCDD/PCDF values of 87, 60 and 67 ng EQ L-1 in stormwater, the river and its reservoirs, respectively, were associated with the highest river flow of 0.02 m3 s-1 and high precipitation (11.2 mm) occurred five days before sampling. In turn, the highest values of 353, 567 and 343 ng EQ L-1 in stormwater, the river and its reservoirs, respectively, were observed during periods of intensive snow melting (stormwater samples) and spring rainfall preceded by a rainless phase (river and reservoir samples) followed by low and moderate river flows of 0.01 and 0.005 m3 s-1. An analogous situation was observed for triclosan, with higher ELISA EQ concentrations (444 to 499 ng EQ L-1) noted during moderate river flow and precipitation, and the lowest (232 to 288 ng EQ L-1) observed during high river flow and high precipitation preceded by violent storms. Stormwater was also found to influence PCDD/PCDF EQ concentrations of the river and reservoirs, however only during high and moderate flow, and no such effect was observed for triclosan. The study clearly demonstrates that to mitigate the high peaks of the studied pollutants associated with river hydrology, the increased in-site stormwater infiltration and purification, the development of buffering zones along river course and the systematic maintenance of reservoirs to avoid the accumulation of the studied micropollutants and their subsequent release after heavy rainfall are required. PMID:26985830

Effects of Stormwater and Snowmelt Runoff on ELISA-EQ Concentrations of PCDD/PCDF and Triclosan in an Urban River.

PubMed

Urbaniak, Magdalena; Tygielska, Adrianna; Krauze, Kinga; Mankiewicz-Boczek, Joanna

2016-01-01

The aim of the study was to determine the effects of stormwater and snowmelt runoff on the ELISA EQ PCDD/PCDF and triclosan concentrations in the small urban Sokołówka River (Central Poland). The obtained results demonstrate the decisive influence of hydrological conditions occurring in the river itself and its catchment on the quoted PCDD/PCDF ELISA EQ concentrations. The lowest PCDD/PCDF values of 87, 60 and 67 ng EQ L-1 in stormwater, the river and its reservoirs, respectively, were associated with the highest river flow of 0.02 m3 s-1 and high precipitation (11.2 mm) occurred five days before sampling. In turn, the highest values of 353, 567 and 343 ng EQ L-1 in stormwater, the river and its reservoirs, respectively, were observed during periods of intensive snow melting (stormwater samples) and spring rainfall preceded by a rainless phase (river and reservoir samples) followed by low and moderate river flows of 0.01 and 0.005 m3 s-1. An analogous situation was observed for triclosan, with higher ELISA EQ concentrations (444 to 499 ng EQ L-1) noted during moderate river flow and precipitation, and the lowest (232 to 288 ng EQ L-1) observed during high river flow and high precipitation preceded by violent storms. Stormwater was also found to influence PCDD/PCDF EQ concentrations of the river and reservoirs, however only during high and moderate flow, and no such effect was observed for triclosan. The study clearly demonstrates that to mitigate the high peaks of the studied pollutants associated with river hydrology, the increased in-site stormwater infiltration and purification, the development of buffering zones along river course and the systematic maintenance of reservoirs to avoid the accumulation of the studied micropollutants and their subsequent release after heavy rainfall are required.

Adequacy of satellite derived rainfall data for stream flow modeling

USGS Publications Warehouse

Artan, G.; Gadain, Hussein; Smith, Jodie; Asante, Kwasi; Bandaragoda, C.J.; Verdin, J.P.

2007-01-01

Floods are the most common and widespread climate-related hazard on Earth. Flood forecasting can reduce the death toll associated with floods. Satellites offer effective and economical means for calculating areal rainfall estimates in sparsely gauged regions. However, satellite-based rainfall estimates have had limited use in flood forecasting and hydrologic stream flow modeling because the rainfall estimates were considered to be unreliable. In this study we present the calibration and validation results from a spatially distributed hydrologic model driven by daily satellite-based estimates of rainfall for sub-basins of the Nile and Mekong Rivers. The results demonstrate the usefulness of remotely sensed precipitation data for hydrologic modeling when the hydrologic model is calibrated with such data. However, the remotely sensed rainfall estimates cannot be used confidently with hydrologic models that are calibrated with rain gauge measured rainfall, unless the model is recalibrated. ?? Springer Science+Business Media, Inc. 2007.

Future climate scenarios and rainfall--runoff modelling in the Upper Gallego catchment (Spain).

PubMed

Bürger, C M; Kolditz, O; Fowler, H J; Blenkinsop, S

2007-08-01

Global climate change may have large impacts on water supplies, drought or flood frequencies and magnitudes in local and regional hydrologic systems. Water authorities therefore rely on computer models for quantitative impact prediction. In this study we present kernel-based learning machine river flow models for the Upper Gallego catchment of the Ebro basin. Different learning machines were calibrated using daily gauge data. The models posed two major challenges: (1) estimation of the rainfall-runoff transfer function from the available time series is complicated by anthropogenic regulation and mountainous terrain and (2) the river flow model is weak when only climate data are used, but additional antecedent flow data seemed to lead to delayed peak flow estimation. These types of models, together with the presented downscaled climate scenarios, can be used for climate change impact assessment in the Gallego, which is important for the future management of the system.

How is the River Water Quality Response to Climate Change Impacts?

NASA Astrophysics Data System (ADS)

Nguyen, T. T.; Willems, P.

2015-12-01

Water quality and its response to climate change have been become one of the most important issues of our society, which catches the attention of many scientists, environmental activists and policy makers. Climate change influences the river water quality directly and indirectly via rainfall and air temperature. For example, low flow decreases the volume of water for dilution and increases the residence time of the pollutants. By contrast, high flow leads to increases in the amount of pollutants and sediment loads from catchments to rivers. The changes in hydraulic characteristics, i.e. water depth and velocity, affect the transportation and biochemical transformation of pollutants in the river water body. The high air temperature leads to increasing water temperature, shorter growing periods of different crops and water demands from domestic households and industries, which eventually effects the level of river pollution. This study demonstrates the quantification of the variation of the water temperature and pollutant concentrations along the Molse Neet river in the North East of Belgium as a result of the changes in the catchment rainfall-runoff, air temperature and nutrient loads. Firstly, four climate change scenarios were generated based on a large ensemble of available global and regional climate models and statistical downscaling based on a quantile perturbation method. Secondly, the climatic changes to rainfall and temperature were transformed to changes in the evapotranspiration and runoff flow through the conceptual hydrological model PDM. Thirdly, the adjustment in nutrient loads from agriculture due to rainfall and growing periods of crops were calculated by means of the semi-empirical SENTWA model. Water temperature was estimated from air temperature by a stochastic model separating the temperature into long-term annual and short-term residual components. Next, hydrodynamic and water quality models of the river, implemented in InfoWorks RS, were simulated for both historical (2000-2010) and projected future periods (2050-2060). The advection movement and physico-biochemical processes were considered for simulation of the following water quality variables: water temperature, dissolved oxygen, biological oxygen demand, ammonium, nitrate, nitrite and organic nitrogen.

Vallerani Micro-Catchment Infiltration Dynamics and Erosion from Simulated Rainfall and Concentrated Flow

NASA Astrophysics Data System (ADS)

Founds, M. J.; McGwire, K.; Weltz, M.

2017-12-01

Critical research gaps in rangeland hydrology still exist on the impact of conservation practices on erosion and subsequent mobilization of dissolved solids to streams. This study develops the scientific foundation necessary to better understand how a restoration strategy using a Vallerani Plow can be optimized to minimize erosion from rainfall impact and concentrated flow. Use of the Vallerani system has been proposed for use in the Upper Colorado River Basin (UCRB), where rapidly eroding rangelands contribute high salt loads to the Colorado River at a significant economic cost. The poster presentation will document the findings from a series of physical rainfall and concentrated flow simulations taking place at an experimental site northeast of Reno, NV in early August. A Walnut Gulch Rainfall simulator is used to apply variable intensity and duration rainfall events to micro-catchment structures created by the Vallerani Plow. The erosion and deposition caused by simulated rainfall will be captured from multi-angle photography using structure from motion (SFM) to create sub-centimeter 3-D models between each rainfall event. A rill-simulator also will be used to apply large volumes of concentrated flow to Vallerani micro-catchments, testing the point at which their infiltration capacity is exceeded and micro-catchments are overtopped. This information is important to adequately space structures on a given hillslope so that chances of failure are minimized. Measurements of saturated hydraulic conductivity and sorptivity from a Guelph Permeameter will be compared to the experimental results in order to develop an efficient method for surveying new terrain for treatment with the Vallerani plow. The effect of micro-catchments on surface flow and erosion will eventually be incorporated into the process-based Rangeland Hydrology and Erosion Model (RHEM) to create a tool that provides decision makers with quantitative estimates of potential reductions in erosion when using the Vallerani System to restore highly erosive rangelands within the UCRB.

Flood risk reduction and flow buffering as ecosystem services - Part 2: Land use and rainfall intensity effects in Southeast Asia

NASA Astrophysics Data System (ADS)

van Noordwijk, Meine; Tanika, Lisa; Lusiana, Betha

2017-05-01

Watersheds buffer the temporal pattern of river flow relative to the temporal pattern of rainfall. This ecosystem service is inherent to geology and climate, but buffering also responds to human use and misuse of the landscape. Buffering can be part of management feedback loops if salient, credible and legitimate indicators are used. The flow persistence parameter Fp in a parsimonious recursive model of river flow (Part 1, van Noordwijk et al., 2017) couples the transmission of extreme rainfall events (1 - Fp), to the annual base-flow fraction of a watershed (Fp). Here we compare Fp estimates from four meso-scale watersheds in Indonesia (Cidanau, Way Besai and Bialo) and Thailand (Mae Chaem), with varying climate, geology and land cover history, at a decadal timescale. The likely response in each of these four to variation in rainfall properties (including the maximum hourly rainfall intensity) and land cover (comparing scenarios with either more or less forest and tree cover than the current situation) was explored through a basic daily water-balance model, GenRiver. This model was calibrated for each site on existing data, before being used for alternative land cover and rainfall parameter settings. In both data and model runs, the wet-season (3-monthly) Fp values were consistently lower than dry-season values for all four sites. Across the four catchments Fp values decreased with increasing annual rainfall, but specific aspects of watersheds, such as the riparian swamp (peat soils) in Cidanau reduced effects of land use change in the upper watershed. Increasing the mean rainfall intensity (at constant monthly totals for rainfall) around the values considered typical for each landscape was predicted to cause a decrease in Fp values by between 0.047 (Bialo) and 0.261 (Mae Chaem). Sensitivity of Fp to changes in land use change plus changes in rainfall intensity depends on other characteristics of the watersheds, and generalisations made on the basis of one or two case studies may not hold, even within the same climatic zone. A wet-season Fp value above 0.7 was achievable in forest-agroforestry mosaic case studies. Inter-annual variability in Fp is large relative to effects of land cover change. Multiple (5-10) years of paired-plot data would generally be needed to reject no-change null hypotheses on the effects of land use change (degradation and restoration). Fp trends over time serve as a holistic scale-dependent performance indicator of degrading/recovering watershed health and can be tested for acceptability and acceptance in a wider social-ecological context.

Discharge prediction in the Upper Senegal River using remote sensing data

NASA Astrophysics Data System (ADS)

Ceccarini, Iacopo; Raso, Luciano; Steele-Dunne, Susan; Hrachowitz, Markus; Nijzink, Remko; Bodian, Ansoumana; Claps, Pierluigi

2017-04-01

The Upper Senegal River, West Africa, is a poorly gauged basin. Nevertheless, discharge predictions are required in this river for the optimal operation of the downstream Manantali reservoir, flood forecasting, development plans for the entire basin and studies for adaptation to climate change. Despite the need for reliable discharge predictions, currently available rainfall-runoff models for this basin provide only poor performances, particularly during extreme regimes, both low-flow and high-flow. In this research we develop a rainfall-runoff model that combines remote-sensing input data and a-priori knowledge on catchment physical characteristics. This semi-distributed model, is based on conceptual numerical descriptions of hydrological processes at the catchment scale. Because of the lack of reliable input data from ground observations, we use the Tropical Rainfall Measuring Mission (TRMM) remote-sensing data for precipitation and the Global Land Evaporation Amsterdam Model (GLEAM) for the terrestrial potential evaporation. The model parameters are selected by a combination of calibration, by match of observed output and considering a large set of hydrological signatures, as well as a-priori knowledge on the catchment. The Generalized Likelihood Uncertainty Estimation (GLUE) method was used to choose the most likely range in which the parameter sets belong. Analysis of different experiments enhances our understanding on the added value of distributed remote-sensing data and a-priori information in rainfall-runoff modelling. Results of this research will be used for decision making at different scales, contributing to a rational use of water resources in this river.

Flow characteristics and salinity patterns of tidal rivers within the northern Ten Thousand Islands, southwest Florida, water years 2007–14

USGS Publications Warehouse

Booth, Amanda C.; Soderqvist, Lars E.

2016-12-12

Freshwater flow to the Ten Thousand Islands estuary has been altered by the construction of the Tamiami Trail and the Southern Golden Gate Estates. The Picayune Strand Restoration Project, which is associated with the Comprehensive Everglades Restoration Plan, has been implemented to improve freshwater delivery to the Ten Thousand Islands estuary by removing hundreds of miles of roads, emplacing hundreds of canal plugs, removing exotic vegetation, and constructing three pump stations. Quantifying the tributary flows and salinity patterns prior to, during, and after the restoration is essential to assessing the effectiveness of upstream restoration efforts.Tributary flow and salinity patterns during preliminary restoration efforts and prior to the installation of pump stations were analyzed to provide baseline data and preliminary analysis of changes due to restoration efforts. The study assessed streamflow and salinity data for water years1 2007–2014 for the Faka Union River (canal flow included), East River, Little Wood River, Pumpkin River, and Blackwater River. Salinity data from the Palm River and Faka Union Boundary water-quality stations were also assessed.Faka Union River was the dominant contributor of freshwater during water years 2007–14 to the Ten Thousand Islands estuary, followed by Little Wood and East Rivers. Pumpkin River and Blackwater River were the least substantial contributors of freshwater flow. The lowest annual flow volumes, the highest annual mean salinities, and the highest percentage of salinity values greater than 35 parts per thousand (ppt) occurred in water year 2011 at all sites with available data, corresponding with the lowest annual rainfall during the study. The highest annual flow volumes and the lowest percentage of salinities greater than 35 ppt occurred in water year 2013 for all sites with available data, corresponding with the highest rainfall during the study.In water year 2014, the percentage of monitored annual flow contributed by East River increased and the percentage of flow contributed by Faka Union River decreased, compared to the earlier years. No changes in annual flow occurred at any sites west of Faka Union River. No changes in the relative flow contributions were observed during the wet season; however, the relative amounts of streamflow increased during the dry season at East River in 2014. East River had only 1 month of negative flow in 2014 compared to 6 months in 2011 and 7 months in 2008. Higher dry season flows in East River may be in response to restoration efforts. The sites to the west of Faka Union River had higher salinities on average than Faka Union River and East River. Faka Union River had the highest range in salinities, and Faka Union Boundary had the lowest range in salinities. Pumpkin River was the tributary with the lowest range in salinities.1Water year is defined as the 12-month period from October 1, for any given year, through September 30 of the following year.

The remarkable occurrence of large rainfall-induced debris flows at two different locations on July 12, 2008, Southern Sierra Nevada, CA, USA

USGS Publications Warehouse

DeGraff, J.V.; Wagner, D.L.; Gallegos, A.J.; DeRose, M.; Shannon, C.; Ellsworth, T.

2011-01-01

On July 12, 2008, two convective cells about 155 km apart produced a brief period of intense rainfall triggering large debris flows in the southern Sierra Nevada. The northernmost cell was centered over Oak Creek Canyon, an east-flowing drainage, and its tributaries near Independence, CA, USA. About 5:00 P.M., debris flows passed down the South Fork and North Fork of Oak Creek to merge into a large single feature whose passage affected the historic Mt. Whitney Fish hatchery and blocked California State Highway 395. At about the same time, the southernmost cell was largely centered over Erskine Creek, a main tributary of the west-flowing Kern River. Debris flows issued from several branches to coalesce into a large debris flow that passed along Erskine Creek, through the town of Lake Isabella, CA, USA and into the Kern River. It was observed reaching Lake Isabella about 6:30 P.M. Both debris flows caused significant disruption and damage to local communities. ?? 2011 Springer-Verlag.

The Impact of Climate Projection Method on the Analysis of Climate Change in Semi-arid Basins

NASA Astrophysics Data System (ADS)

Halper, E.; Shamir, E.

2016-12-01

In small basins with arid climates, rainfall characteristics are highly variable and stream flow is tightly coupled with the nuances of rainfall events (e.g. hourly precipitation patterns Climate change assessments in these basins typically employ CMIP5 projections downscaled with Bias Corrected Statistical Downscaling and Bias Correction/Constructed Analogs (BCSD-BCCA) methods, but these products have drawbacks. Specifically, BCSD-BCCA these projections do not explicitly account for localized physical precipitation mechanisms (e.g. monsoon and snowfall) that are essential to many hydrological systems in the U. S. Southwest. An investigation of the impact of different types of precipitation projections for two kinds of hydrologic studies is being conducted under the U.S. Bureau of Reclamation's Science and Technology Grant Program. An innovative modeling framework consisting of a weather generator of likely hourly precipitation scenarios, coupled with rainfall-runoff, river routing and groundwater models, has been developed in the Nogales, Arizona area. This framework can simulate the impact of future climate on municipal water operations. This framework allows the rigorous comparison of the BCSD-BCCA methods with alternative approaches including rainfall output from dynamical downscaled Regional Climate Models (RCM), a stochastic rainfall generator forced by either Global Climate Models (GCM) or RCM, and projections using historical records conditioned on either GCM or RCM. The results will provide guide for the use of climate change projections into hydrologic studies of semi-arid areas. The project extends this comparison to analyses of flood control. Large flows on the Bill Williams River are a concern for the operation of dams along the Lower Colorado River. After adapting the weather generator for this region, we will evaluate the model performance for rainfall and stream flow, with emphasis on statistical features important to the specific needs of flood management. The end product of the research is to develop a test to guide selection of a precipitation projection method (including downscaling procedure) for a given region and objective.

Effect of the spatiotemporal variability of rainfall inputs in water quality integrated catchment modelling for dissolved oxygen concentrations

NASA Astrophysics Data System (ADS)

Moreno Ródenas, Antonio Manuel; Cecinati, Francesca; ten Veldhuis, Marie-Claire; Langeveld, Jeroen; Clemens, Francois

2016-04-01

Maintaining water quality standards in highly urbanised hydrological catchments is a worldwide challenge. Water management authorities struggle to cope with changing climate and an increase in pollution pressures. Water quality modelling has been used as a decision support tool for investment and regulatory developments. This approach led to the development of integrated catchment models (ICM), which account for the link between the urban/rural hydrology and the in-river pollutant dynamics. In the modelled system, rainfall triggers the drainage systems of urban areas scattered along a river. When flow exceeds the sewer infrastructure capacity, untreated wastewater enters the natural system by combined sewer overflows. This results in a degradation of the river water quality, depending on the magnitude of the emission and river conditions. Thus, being capable of representing these dynamics in the modelling process is key for a correct assessment of the water quality. In many urbanised hydrological systems the distances between draining sewer infrastructures go beyond the de-correlation length of rainfall processes, especially, for convective summer storms. Hence, spatial and temporal scales of selected rainfall inputs are expected to affect water quality dynamics. The objective of this work is to evaluate how the use of rainfall data from different sources and with different space-time characteristics affects modelled output concentrations of dissolved oxygen in a simplified ICM. The study area is located at the Dommel, a relatively small and sensitive river flowing through the city of Eindhoven (The Netherlands). This river stretch receives the discharge of the 750,000 p.e. WWTP of Eindhoven and from over 200 combined sewer overflows scattered along its length. A pseudo-distributed water quality model has been developed in WEST (mikedhi.com); this is a lumped-physically based model that accounts for urban drainage processes, WWTP and river dynamics for several pollutant typologies. Different rainfall products are tested: 1) Block kriging of a single reliable rain gauge, 2) Block kriging product from a network of 13 rain gauges and, 3) Universal block kriging with 13 rain gauges and KNMI weather radar estimates as a covariate. Different temporal accumulation levels are compared ranging from 10min to 1h. A geostatistical approach is used to allocate the prediction of the rainfall input in each of the urban hydrological units composing the model. The change in model performance is then assessed by contrasting it with dissolved oxygen monitoring data in a series of events.

Regional scale flood modeling using NEXRAD rainfall, GIS, and HEC-HMS/RAS: a case study for the San Antonio River Basin Summer 2002 storm event.

PubMed

Knebl, M R; Yang, Z-L; Hutchison, K; Maidment, D R

2005-06-01

This paper develops a framework for regional scale flood modeling that integrates NEXRAD Level III rainfall, GIS, and a hydrological model (HEC-HMS/RAS). The San Antonio River Basin (about 4000 square miles, 10,000 km2) in Central Texas, USA, is the domain of the study because it is a region subject to frequent occurrences of severe flash flooding. A major flood in the summer of 2002 is chosen as a case to examine the modeling framework. The model consists of a rainfall-runoff model (HEC-HMS) that converts precipitation excess to overland flow and channel runoff, as well as a hydraulic model (HEC-RAS) that models unsteady state flow through the river channel network based on the HEC-HMS-derived hydrographs. HEC-HMS is run on a 4 x 4 km grid in the domain, a resolution consistent with the resolution of NEXRAD rainfall taken from the local river authority. Watershed parameters are calibrated manually to produce a good simulation of discharge at 12 subbasins. With the calibrated discharge, HEC-RAS is capable of producing floodplain polygons that are comparable to the satellite imagery. The modeling framework presented in this study incorporates a portion of the recently developed GIS tool named Map to Map that has been created on a local scale and extends it to a regional scale. The results of this research will benefit future modeling efforts by providing a tool for hydrological forecasts of flooding on a regional scale. While designed for the San Antonio River Basin, this regional scale model may be used as a prototype for model applications in other areas of the country.

Mitigating mass movement caused by earthquakes and typhoons: a case study of central Taiwan

NASA Astrophysics Data System (ADS)

Lin, Jiun-Chuan

2013-04-01

Typhoons caused huge damages to Taiwan at the average of 3.8 times a year in the last 100 years, according to Central Weather Bureau data. After the Chi-Chi earthquake of 1999 at the magnitude of Richard Scale 7.3, typhoons with huge rainfall would cause huge debris flow and deposits at river channels. As a result of earthquakes, loose debris falls and flows became significant hazards in central Taiwan. Analysis of rainfall data and data about the sites of slope failure show that damage from natural hazards was enhanced in the last 20 years, as a result of the Chi-Chi earthquake. There are three main types of mass movement in Central Taiwan: landslides, debris flows and gully erosion. Landslides occurred mainly along hill slopes and river channel banks. Many dams, check dams, housing structures and even river channels can be raised to as high as 60 meters as a result of stacking up floating materials of landslides. Debris flows occurred mainly through typhoon periods and activated ancient debris deposition. New gullies were thus developed from deposits loosened and shaken up by earthquakes. Extreme earthquakes and typhoon events occurred frequently in the last 20 years. This paper analyzes the geological and geomorphologic background for the precarious areas and typhoons in central Taiwan, to make a systematic understanding of mass movement harzards. The mechanism and relations of debris flows and rainfall data in central Taiwan are analyzed. Ways for mitigating mass movement threats are also proposed in this paper. Keywords: mass movement, earthquakes, typhoons, hazard mitigation, central Ta

Real-time flood forecasting

USGS Publications Warehouse

Lai, C.; Tsay, T.-K.; Chien, C.-H.; Wu, I.-L.

2009-01-01

Researchers at the Hydroinformatic Research and Development Team (HIRDT) of the National Taiwan University undertook a project to create a real time flood forecasting model, with an aim to predict the current in the Tamsui River Basin. The model was designed based on deterministic approach with mathematic modeling of complex phenomenon, and specific parameter values operated to produce a discrete result. The project also devised a rainfall-stage model that relates the rate of rainfall upland directly to the change of the state of river, and is further related to another typhoon-rainfall model. The geographic information system (GIS) data, based on precise contour model of the terrain, estimate the regions that were perilous to flooding. The HIRDT, in response to the project's progress, also devoted their application of a deterministic model to unsteady flow of thermodynamics to help predict river authorities issue timely warnings and take other emergency measures.

Intra-annual variation in turbidity in response to terrestrial runoff on near-shore coral reefs of the Great Barrier Reef

NASA Astrophysics Data System (ADS)

Fabricius, Katharina E.; De'ath, Glenn; Humphrey, Craig; Zagorskis, Irena; Schaffelke, Britta

2013-01-01

Seawater turbidity is a fundamental driver of the ecology of coastal marine systems, and is widely used as indicator for environmental reporting. However, the time scales and processes leading to changes in turbidity in tropical coastal waters remain poorly understood. This study investigates the main determinants of inshore turbidity in four inshore regions along ˜1000 km of the Australian Great Barrier Reef, based on ˜3 years of almost continuous in situ turbidity logger data on 14 reefs. Generalized additive mixed models were used to predict spatial and temporal variation in weekly mean turbidity based on variation in resuspension and runoff conditions. At any given wave height, wave period and tidal range, turbidity was significantly affected by river flow and rainfall. Averaged across all reefs, turbidity was 13% lower (range: 5-37%) in weeks with low compared with high rainfall and river flows. Additionally, turbidity was on average 43% lower 250 days into the dry season than at the start of the dry season on reefs with long-term mean turbidity >1.1 NTU. The data suggest the time scale of winnowing or consolidation of newly imported materials in this zone is months to years. In contrast, turbidity returned to low levels within weeks after river flows and rainfall on reefs with long-term mean turbidity of <1.1 NTU. Turbidity was also up to 10-fold higher on reefs near compared to away from river mouths, suggesting inter-annual accumulation of fine resuspendible sediments. The study suggests that a reduction in the river loads of fine sediments and nutrients through improved land management should lead to measurably improved inshore water clarity in the most turbid parts of the GBR.

Simulating Daily and Sub-daily Water Flow in Large, Semi-arid Watershed Using SWAT: A Case Study of Nueces River Basin, Texas

NASA Astrophysics Data System (ADS)

Bassam, S.; Ren, J.

2015-12-01

Runoff generated during heavy rainfall imposes quick, but often intense, changes in the flow of streams, which increase the chance of flash floods in the vicinity of the streams. Understanding the temporal response of streams to heavy rainfall requires a hydrological model that considers meteorological, hydrological, and geological components of the streams and their watersheds. SWAT is a physically-based, semi-distributed model that is capable of simulating water flow within watersheds with both long-term, i.e. annually and monthly, and short-term (daily and sub-daily) time scales. However, the capability of SWAT in sub-daily water flow modeling within large watersheds has not been studied much, compare to long-term and daily time scales. In this study we are investigating the water flow in a large, semi-arid watershed, Nueces River Basin (NRB) with the drainage area of 16950 mi2 located in South Texas, with daily and sub-daily time scales. The objectives of this study are: (1) simulating the response of streams to heavy, and often quick, rainfall, (2) evaluating SWAT performance in sub-daily modeling of water flow within a large watershed, and (3) examining means for model performance improvement during model calibration and verification based on results of sensitivity and uncertainty analysis. The results of this study can provide important information for water resources planning during flood seasons.

Nutrient Dynamics of Estuarine Invertebrates Are Shaped by Feeding Guild Rather than Seasonal River Flow

PubMed Central

Ortega-Cisneros, Kelly; Scharler, Ursula M.

2015-01-01

This study aimed to determine the variability of carbon and nitrogen elemental content, stoichiometry and diet proportions of invertebrates in two sub-tropical estuaries in South Africa experiencing seasonal changes in rainfall and river inflow. The elemental ratios and stable isotopes of abiotic sources, zooplankton and macrozoobenthos taxa were analyzed over a dry/wet seasonal cycle. Nutrient content (C, N) and stoichiometry of suspended particulate matter exhibited significant spatio-temporal variations in both estuaries, which were explained by the variability in river inflow. Sediment particulate matter (%C, %N and C:N) was also influenced by the variability in river flow but to a lesser extent. The nutrient content and ratios of the analyzed invertebrates did not significantly vary among seasons with the exception of the copepod Pseudodiaptomus spp. (C:N) and the tanaid Apseudes digitalis (%N, C:N). These changes did not track the seasonal variations of the suspended or sediment particulate matter. Our results suggest that invertebrates managed to maintain their stoichiometry independent of the seasonality in river flow. A significant variability in nitrogen content among estuarine invertebrates was recorded, with highest % N recorded from predators and lowest %N from detritivores. Due to the otherwise general lack of seasonal differences in elemental content and stoichiometry, feeding guild was a major factor shaping the nutrient dynamics of the estuarine invertebrates. The nutrient richer suspended particulate matter was the preferred food source over sediment particulate matter for most invertebrate consumers in many, but not all seasons. The most distinct preference for suspended POM as a food source was apparent from the temporarily open/closed system after the estuary had breached, highlighting the importance of river flow as a driver of invertebrate nutrient dynamics under extreme events conditions. Moreover, our data showed that estuarine invertebrates concentrated C and N between 10–100 fold from trophic level I (POM) to trophic level II (detritivores/deposit feeders) and thus highlighted their importance not only as links to higher trophic level organisms in the food web, but also as providers of a stoichiometrically homeostatic food source for such consumers. As climate change scenarios for the east coast of South Africa predict increased rainfall as a higher number of rainy days and days with higher rainfall, our results suggest that future changes in rainfall and river inflow will have measurable effects on the nutrient content and stoichiometry of food sources and possibly also in estuarine consumers. PMID:26352433

Nutrient Dynamics of Estuarine Invertebrates Are Shaped by Feeding Guild Rather than Seasonal River Flow.

PubMed

Ortega-Cisneros, Kelly; Scharler, Ursula M

2015-01-01

This study aimed to determine the variability of carbon and nitrogen elemental content, stoichiometry and diet proportions of invertebrates in two sub-tropical estuaries in South Africa experiencing seasonal changes in rainfall and river inflow. The elemental ratios and stable isotopes of abiotic sources, zooplankton and macrozoobenthos taxa were analyzed over a dry/wet seasonal cycle. Nutrient content (C, N) and stoichiometry of suspended particulate matter exhibited significant spatio-temporal variations in both estuaries, which were explained by the variability in river inflow. Sediment particulate matter (%C, %N and C:N) was also influenced by the variability in river flow but to a lesser extent. The nutrient content and ratios of the analyzed invertebrates did not significantly vary among seasons with the exception of the copepod Pseudodiaptomus spp. (C:N) and the tanaid Apseudes digitalis (%N, C:N). These changes did not track the seasonal variations of the suspended or sediment particulate matter. Our results suggest that invertebrates managed to maintain their stoichiometry independent of the seasonality in river flow. A significant variability in nitrogen content among estuarine invertebrates was recorded, with highest % N recorded from predators and lowest %N from detritivores. Due to the otherwise general lack of seasonal differences in elemental content and stoichiometry, feeding guild was a major factor shaping the nutrient dynamics of the estuarine invertebrates. The nutrient richer suspended particulate matter was the preferred food source over sediment particulate matter for most invertebrate consumers in many, but not all seasons. The most distinct preference for suspended POM as a food source was apparent from the temporarily open/closed system after the estuary had breached, highlighting the importance of river flow as a driver of invertebrate nutrient dynamics under extreme events conditions. Moreover, our data showed that estuarine invertebrates concentrated C and N between 10-100 fold from trophic level I (POM) to trophic level II (detritivores/deposit feeders) and thus highlighted their importance not only as links to higher trophic level organisms in the food web, but also as providers of a stoichiometrically homeostatic food source for such consumers. As climate change scenarios for the east coast of South Africa predict increased rainfall as a higher number of rainy days and days with higher rainfall, our results suggest that future changes in rainfall and river inflow will have measurable effects on the nutrient content and stoichiometry of food sources and possibly also in estuarine consumers.

Corps Water Management System (CWMS) Decision Support Modeling and Integration Use in the June 2007 Texas Floods

NASA Astrophysics Data System (ADS)

Charley, W. J.; Luna, M.

2007-12-01

The U.S. Army Corps of Engineers Corps Water Management System (CWMS) is a comprehensive data acquisition and hydrologic modeling system for short-term decision support of water control operations in real time. It encompasses data collection, validation and transformation, data storage, visualization, real time model simulation for decision-making support, and data dissemination. CWMS uses an Oracle database and Sun Solaris workstations for data processes, storage and the execution of models, with a client application (the Control and Visualization Interface, or CAVI) that can run on a Windows PC. CWMS was used by the Lower Colorado River Authority (LCRA) to make hydrologic forecasts of flows on the Lower Colorado River and operate reservoirs during the June 2007 event in Texas. The LCRA receives real-time observed gridded spatial rainfall data from OneRain, Inc. that which is a result of adjusting NexRad rainfall data with precipitation gages. This data is used, along with future precipitation estimates, for hydrologic forecasting by the rainfall-runoff modeling program HEC-HMS. Forecasted flows from HEC-HMS and combined with observed flows and reservoir information to simulate LCRA's reservoir operations and help engineers make release decisions based on the results. The river hydraulics program, HEC-RAS, computes river stages and water surface profiles for the computed flow. An inundation boundary and depth map of water in the flood plain can be calculated from the HEC-RAS results using ArcInfo. By varying future precipitation and releases, engineers can evaluate different "What if?" scenarios. What was described as an "extraordinary cluster of thunderstorms" that stalled over Burnet and Llano counties in Texas on June 27, 2007, dropped 17 to 19 inches of rainfall over a 6-hour period. The storm was classified over a 500-year event and the resulting flow over some of the smaller tributaries as a 100-year or better. CWMS was used by LCRA for flood forecasting and reservoir operations. The models accurately forecasting the flows and allowed engineers to determine that only four floodgates needed to be opened for Mansfield dam, in the Chain of Highland lakes. CWMS also forecasted the peak of the flood well before it happened. Smaller rain storms continued for a period of weeks and CWMS was used throughout the event calculating lake levels, closing of gates along with a hydro-generation schedule.

Modelling Inland Flood Events for Hazard Maps in Taiwan

NASA Astrophysics Data System (ADS)

Ghosh, S.; Nzerem, K.; Sassi, M.; Hilberts, A.; Assteerawatt, A.; Tillmanns, S.; Mathur, P.; Mitas, C.; Rafique, F.

2015-12-01

Taiwan experiences significant inland flooding, driven by torrential rainfall from plum rain storms and typhoons during summer and fall. From last 13 to 16 years data, 3,000 buildings were damaged by such floods annually with a loss US$0.41 billion (Water Resources Agency). This long, narrow island nation with mostly hilly/mountainous topography is located at tropical-subtropical zone with annual average typhoon-hit-frequency of 3-4 (Central Weather Bureau) and annual average precipitation of 2502mm (WRA) - 2.5 times of the world's average. Spatial and temporal distributions of countrywide precipitation are uneven, with very high local extreme rainfall intensities. Annual average precipitation is 3000-5000mm in the mountainous regions, 78% of it falls in May-October, and the 1-hour to 3-day maximum rainfall are about 85 to 93% of the world records (WRA). Rivers in Taiwan are short with small upstream areas and high runoff coefficients of watersheds. These rivers have the steepest slopes, the shortest response time with rapid flows, and the largest peak flows as well as specific flood peak discharge (WRA) in the world. RMS has recently developed a countrywide inland flood model for Taiwan, producing hazard return period maps at 1arcsec grid resolution. These can be the basis for evaluating and managing flood risk, its economic impacts, and insured flood losses. The model is initiated with sub-daily historical meteorological forcings and calibrated to daily discharge observations at about 50 river gauges over the period 2003-2013. Simulations of hydrologic processes, via rainfall-runoff and routing models, are subsequently performed based on a 10000 year set of stochastic forcing. The rainfall-runoff model is physically based continuous, semi-distributed model for catchment hydrology. The 1-D wave propagation hydraulic model considers catchment runoff in routing and describes large-scale transport processes along the river. It also accounts for reservoir storage. Major historical flood events have been successfully simulated along with spatial patterns of flows. Comparison of stochastic discharge statistics w.r.t. observed ones from Hydrological Year Books of Taiwan over all recorded years are also in good agreement.

Extreme Rainfall Analysis using Bayesian Hierarchical Modeling in the Willamette River Basin, Oregon

NASA Astrophysics Data System (ADS)

Love, C. A.; Skahill, B. E.; AghaKouchak, A.; Karlovits, G. S.; England, J. F.; Duren, A. M.

2016-12-01

We present preliminary results of ongoing research directed at evaluating the worth of including various covariate data to support extreme rainfall analysis in the Willamette River basin using Bayesian hierarchical modeling (BHM). We also compare the BHM derived extreme rainfall estimates with their respective counterparts obtained from a traditional regional frequency analysis (RFA) using the same set of rain gage extreme rainfall data. The U.S. Army Corps of Engineers (USACE) Portland District operates thirteen dams in the 11,478 square mile Willamette River basin (WRB) located in northwestern Oregon, a major tributary of the Columbia River whose 187 miles long main stem, the Willamette River, flows northward between the Coastal and Cascade Ranges. The WRB contains approximately two-thirds of Oregon's population and 20 of the 25 most populous cities in the state. Extreme rainfall estimates are required to support risk-informed hydrologic analyses for these projects as part of the USACE Dam Safety Program. We analyze daily annual rainfall maxima data for the WRB utilizing the spatial BHM R package "spatial.gev.bma", which has been shown to be efficient in developing coherent maps of extreme rainfall by return level. Our intent is to profile for the USACE an alternate methodology to a RFA which was developed in 2008 due to the lack of an official NOAA Atlas 14 update for the state of Oregon. Unlike RFA, the advantage of a BHM-based analysis of hydrometeorological extremes is its ability to account for non-stationarity while providing robust estimates of uncertainty. BHM also allows for the inclusion of geographical and climatological factors which we show for the WRB influence regional rainfall extremes. Moreover, the Bayesian framework permits one to combine additional data types into the analysis; for example, information derived via elicitation and causal information expansion data, both being additional opportunities for future related research.

Attribution of extreme precipitation in the lower reaches of the Yangtze River during May 2016

NASA Astrophysics Data System (ADS)

Li, Chunxiang; Tian, Qinhua; Yu, Rong; Zhou, Baiquan; Xia, Jiangjiang; Burke, Claire; Dong, Buwen; Tett, Simon F. B.; Freychet, Nicolas; Lott, Fraser; Ciavarella, Andrew

2018-01-01

May 2016 was the third wettest May on record since 1961 over central eastern China based on station observations, with total monthly rainfall 40% more than the climatological mean for 1961-2013. Accompanying disasters such as waterlogging, landslides and debris flow struck part of the lower reaches of the Yangtze River. Causal influence of anthropogenic forcings on this event is investigated using the newly updated Met Office Hadley Centre system for attribution of extreme weather and climate events. Results indicate that there is a significant increase in May 2016 rainfall in model simulations relative to the climatological period, but this increase is largely attributable to natural variability. El Niño years have been found to be correlated with extreme rainfall in the Yangtze River region in previous studies—the strong El Niño of 2015-2016 may account for the extreme precipitation event in 2016. However, on smaller spatial scales we find that anthropogenic forcing has likely played a role in increasing the risk of extreme rainfall to the north of the Yangtze and decreasing it to the south.

A new hydrological model for estimating extreme floods in the Alps

NASA Astrophysics Data System (ADS)

Receanu, R. G.; Hertig, J.-A.; Fallot, J.-M.

2012-04-01

Protection against flooding is very important for a country like Switzerland with a varied topography and many rivers and lakes. Because of the potential danger caused by extreme precipitation, structural and functional safety of large dams must be guaranteed to withstand the passage of an extreme flood. We introduce a new distributed hydrological model to calculate the PMF from a PMP which is spatially and temporally distributed using clouds. This model has permitted the estimation of extreme floods based on the distributed PMP and the taking into account of the specifics of alpine catchments, in particular the small size of the basins, the complex topography, the large lakes, snowmelt and glaciers. This is an important evolution compared to other models described in the literature, as they mainly use a uniform distribution of extreme precipitation all over the watershed. This paper presents the results of calculation with the developed rainfall-runoff model, taking into account measured rainfall and comparing results to observed flood events. This model includes three parts: surface runoff, underground flow and melting snow. Two Swiss watersheds are studied, for which rainfall data and flow rates are available for a considerably long period, including several episodes of heavy rainfall with high flow events. From these events, several simulations are performed to estimate the input model parameters such as soil roughness and average width of rivers in case of surface runoff. Following the same procedure, the parameters used in the underground flow simulation are also estimated indirectly, since direct underground flow and exfiltration measurements are difficult to obtain. A sensitivity analysis of the parameters is performed at the first step to define more precisely the boundary and initial conditions. The results for the two alpine basins, validated with the Nash equation, show a good correlation between the simulated and observed flows. This good correlation shows that the model is valid and gives us the confidence that the results can be extrapolated to phenomena of extreme rainfall of PMP type.

2D Flood Modelling Using Advanced Terrain Analysis Techniques And A Fully Continuous DEM-Based Rainfall-Runoff Algorithm

NASA Astrophysics Data System (ADS)

Nardi, F.; Grimaldi, S.; Petroselli, A.

2012-12-01

Remotely sensed Digital Elevation Models (DEMs), largely available at high resolution, and advanced terrain analysis techniques built in Geographic Information Systems (GIS), provide unique opportunities for DEM-based hydrologic and hydraulic modelling in data-scarce river basins paving the way for flood mapping at the global scale. This research is based on the implementation of a fully continuous hydrologic-hydraulic modelling optimized for ungauged basins with limited river flow measurements. The proposed procedure is characterized by a rainfall generator that feeds a continuous rainfall-runoff model producing flow time series that are routed along the channel using a bidimensional hydraulic model for the detailed representation of the inundation process. The main advantage of the proposed approach is the characterization of the entire physical process during hydrologic extreme events of channel runoff generation, propagation, and overland flow within the floodplain domain. This physically-based model neglects the need for synthetic design hyetograph and hydrograph estimation that constitute the main source of subjective analysis and uncertainty of standard methods for flood mapping. Selected case studies show results and performances of the proposed procedure as respect to standard event-based approaches.

Why was the strengthening of rainfall in summer over the Yangtze River valley in 2016 less pronounced than that in 1998 under similar preceding El Niño events?—Role of midlatitude circulation in August

NASA Astrophysics Data System (ADS)

Li, Chaofan; Chen, Wei; Hong, Xiaowei; Lu, Riyu

2017-11-01

It is widely recognized that rainfall over the Yangtze River valley (YRV) strengthens considerably during the decaying summer of El Niño, as demonstrated by the catastrophic flooding suffered in the summer of 1998. Nevertheless, the rainfall over the YRV in the summer of 2016 was much weaker than that in 1998, despite the intensity of the 2016 El Niño having been as strong as that in 1998. A thorough comparison of the YRV summer rainfall anomaly between 2016 and 1998 suggests that the difference was caused by the sub-seasonal variation in the YRV rainfall anomaly between these two years, principally in August. The precipitation anomaly was negative in August 2016—different to the positive anomaly of 1998. Further analysis suggests that the weaker YRV rainfall in August 2016 could be attributable to the distinct circulation anomalies over the midlatitudes. The intensified "Silk Road Pattern" and upper-tropospheric geopotential height over the Urals region, both at their strongest since 1980, resulted in an anticyclonic circulation anomaly over midlatitude East Asia with anomalous easterly flow over the middle-to-lower reaches of the YRV in the lower troposphere. This easterly flow reduced the climatological wind, weakened the water vapor transport, and induced the weaker YRV rainfall in August 2016, as compared to that in 1998. Given the unique sub-seasonal variation of the YRV rainfall in summer 2016, more attention should be paid to midlatitude circulation—besides the signal in the tropics—to further our understanding of the predictability and variation of YRV summer rainfall.

Satellite-derived temperature data for monitoring water status in a floodplain forest of the Upper Sabine River, Texas

USGS Publications Warehouse

Lemon, Mary Grace T.; Allen, Scott T.; Edwards, Brandon L.; King, Sammy L.; Keim, Richard F.

2016-01-01

Decreased water availability due to hydrologic modifications, groundwater withdrawal, and climate change threaten bottomland hardwood (BLH) forest communities. We used satellite-derived (MODIS) land-surface temperature (LST) data to investigate spatial heterogeneity of canopy temperature (an indicator of plant-water status) in a floodplain forest of the upper Sabine River for 2008–2014. High LST pixels were generally further from the river and at higher topographic locations, indicating lower water-availability. Increasing rainfall-derived soil moisture corresponded with decreased heterogeneity of LST between pixels but there was weaker association between Sabine River stage and heterogeneity. Stronger dependence of LST convergence on rainfall rather than river flow suggests that some regions are less hydrologically connected to the river, and vegetation may rely on local precipitation and other contributions to the riparian aquifer to replenish soil moisture. Observed LST variations associated with hydrology encourage further investigation of the utility of this approach for monitoring forest stress, especially with considerations of climate change and continued river management.

Application of satellite-based rainfall and medium range meteorological forecast in real-time flood forecasting in the Mahanadi River basin

NASA Astrophysics Data System (ADS)

Nanda, Trushnamayee; Beria, Harsh; Sahoo, Bhabagrahi; Chatterjee, Chandranath

2016-04-01

Increasing frequency of hydrologic extremes in a warming climate call for the development of reliable flood forecasting systems. The unavailability of meteorological parameters in real-time, especially in the developing parts of the world, makes it a challenging task to accurately predict flood, even at short lead times. The satellite-based Tropical Rainfall Measuring Mission (TRMM) provides an alternative to the real-time precipitation data scarcity. Moreover, rainfall forecasts by the numerical weather prediction models such as the medium term forecasts issued by the European Center for Medium range Weather Forecasts (ECMWF) are promising for multistep-ahead flow forecasts. We systematically evaluate these rainfall products over a large catchment in Eastern India (Mahanadi River basin). We found spatially coherent trends, with both the real-time TRMM rainfall and ECMWF rainfall forecast products overestimating low rainfall events and underestimating high rainfall events. However, no significant bias was found for the medium rainfall events. Another key finding was that these rainfall products captured the phase of the storms pretty well, but suffered from consistent under-prediction. The utility of the real-time TRMM and ECMWF forecast products are evaluated by rainfall-runoff modeling using different artificial neural network (ANN)-based models up to 3-days ahead. Keywords: TRMM; ECMWF; forecast; ANN; rainfall-runoff modeling

The effects of large-scale afforestation and climate change on water allocation in the Macquarie River catchment, NSW, Australia.

PubMed

Herron, Natasha; Davis, Richard; Jones, Roger

2002-08-01

Widespread afforestation has been proposed as one means of addressing the increasing dryland and stream salinity problem in Australia. However, modelling results presented here suggest that large-scale tree planting will substantially reduce river flows and impose costs on downstream water users if planted in areas of high runoff yield. Streamflow reductions in the Macquarie River, NSW, Australia are estimated for a number of tree planting scenarios and global warming forecasts. The modelling framework includes the Sacramento rainfall-runoff model and IQQM, a streamflow routing tool, as well as various global climate model outputs from which daily rainfall and potential evaporation data files have been generated in OzClim, a climate scenario generator. For a 10% increase in tree cover in the headwaters of the Macquarie, we estimate a 17% reduction in inflows to Burrendong Dam. The drying trend for a mid-range scenario of regional rainfall and potential evaporation caused by a global warming of 0.5 degree C may cause an additional 5% reduction in 2030. These flow reductions will decrease the frequency of bird-breeding events in Macquarie Marshes (a RAMSAR protected wetland) and reduce the security of supply to irrigation areas downstream. Inter-decadal climate variability is predicted to have a very significant influence on catchment hydrologic behaviour. A further 20% reduction in flows from the long-term historical mean is possible, should we move into an extended period of below average rainfall years, such as occurred in eastern Australia between 1890 and 1948. Because current consumptive water use is largely adapted to the wetter conditions of post 1949, a return to prolonged dry periods would cause significant environmental stress given the agricultural and domestic water developments that have been instituted.

[Characteristics of nutrient loss by runoff in sloping arable land of yellow-brown under different rainfall intensities].

PubMed

Chen, Ling; Liu, De-Fu; Song, Lin-Xu; Cui, Yu-Jie; Zhang, Gei

2013-06-01

In order to investigate the loss characteristics of N and P through surface flow and interflow under different rainfall intensities, a field experiment was conducted on the sloping arable land covered by typical yellow-brown soils inXiangxi River watershed by artificial rainfall. The results showed that the discharge of surface flow, total runoff and sediment increased with the increase of rain intensity, while the interflow was negatively correlated with rain intensity under the same total rainfall. TN, DN and DP were all flushed at the very beginning in surface flow underdifferent rainfall intensities; TP fluctuated and kept consistent in surface flow without obvious downtrend. While TN, DN and DP in interflow kept relatively stable in the whole runoff process, TP was high at the early stage, then rapidly decreased with time and kept steady finally. P was directly influenced by rainfall intensity, its concentration in the runoff increased with the increase of the rainfall intensity, the average concentration of N and P both exceeded the threshold of eutrophication of freshwater. The higher the amount of P loss was, the higher the rain intensity. The change of N loss was the opposite. The contribution rate of TN loss carried by surface flow increased from 36.5% to 57.6% with the increase of rainfall intensity, but surface flow was the primary form of P loss which contributed above 90.0%. Thus, it is crucial to control interflow in order to reduce N loss. In addition, measures should be taken to effectively manage soil erosion to mitigate P loss. The proportion of dissolved nitrogen in surface flow elevated with the decrease of rainfall intensity, but in interflow, dissolved form was predominant. P was exported mainly in the form of particulate under different rainfall intensities and runoff conditions.

Preliminary assessment of Eflows on Lucanian Rivers through IHA implementation

NASA Astrophysics Data System (ADS)

Greco, Michele; Martino, Giovanni

2016-04-01

According to the WFD, the ecological flow (Eflow) is assumed to be the hydrological regime consistent with the achievement of the environmental objectives of "good quality status" in natural surface water bodies. As well known, the hydrological regime of natural flow plays a primary and crucial role influencing the physical conditions of habitats, which in turn determines the biotic composition and sustainability of aquatic ecosystems. Furthermore, the simple assumption to supply a minimum instream during dry periods is not enough anymore in order to protect the river environment. The recent hydro-ecological knowledge provides that all flow components must be included as operational targets for water quantitative management from base flows (including low flows) to high and flood regimes in terms of magnitude, frequency, duration, timing and rate of change. Several conceptual and numerical codes have been developed and applied on different case studies in order to define common tools to be implemented for the Eflow assessment. In such a frame, the work deals with the application of the Indicators of Hydrologic Alteration methodology (IHA by TNC) to main Lucanian rivers to assess the ecological flow to be assumed in each monitoring cross section. The analyses have been carried on monthly discharge data derived through a simple rainfall-runoff applied at the basin scale and based on the precipitation measurements obtained by the regional rainfall gauge stations.

Design of Environmental Flows Below Diversion Hydropower Dams: Is There Benefit to Advanced Streamflow Prediction in Sparse Data Landscapes?

NASA Astrophysics Data System (ADS)

Kibler, K. M.; Alipour, M.

2017-12-01

Diversion hydropower has been shown to significantly alter river flow regimes by dewatering diversion bypass reaches. Data scarcity is one of the foremost challenges to establishing environmental flow regimes below diversion hydropower dams, especially in regions of sparse hydro-meteorological observation. Herein, we test two prediction strategies for generating daily flows in rivers developed with diversion hydropower: a catchment similarity model, and a rainfall-runoff model selected by multi-objective optimization based on soft data. While both methods are designed for ungauged rivers embedded within large regions of sparse hydrologic observation, one is more complex and computationally-intensive. The objective of this study is to assess the benefit of using complex modeling tools in data-sparse landscapes to support design of environmental flow regimes. Models were tested in gauged catchments and then used to simulate a 28-year record of daily flows in 32 ungauged rivers. After perturbing flows with the hydropower diversion, we detect alteration using Indicators of Hydrologic Alteration (IHA) metrics and compare outcomes of the two modeling approaches. The catchment similarity model simulates low flows well (Nash-Sutcliff efficiency (NSE) = 0.91), but poorly represents moderate to high flows (overall NSE = 0.25). The multi-objective rainfall-runoff model performs well overall (NSE = 0.72). Both models agree that flow magnitudes and variability consistently decrease following diversion as temporally-dynamic flows are replaced by static minimal flows. Mean duration of events sustained below the pre-diversion Q75 and mean hydrograph rise and fall rates increase. While we see broad areas of agreement, significant effects and thresholds vary between models, particularly in the representation of moderate flows. Thus, use of simplified streamflow models may bias detected alterations or inadequately characterize pre-regulation flow regimes, providing inaccurate information as a basis for flow regime design. As an alternative, the multi-objective framework can be applied globally, and is robust to common challenges of flow prediction in ungauged rivers, such as equifinality and hydrologic dissimilarity of reference catchments.

Out of Africa: the importance of rivers as human migration corridors

NASA Astrophysics Data System (ADS)

Ramirez, J. A.; Coulthard, T. J.; Rogerson, M.; Barton, N.; Bruecher, T.

2013-12-01

The route and timing of Homo sapiens exiting Africa remains uncertain. Corridors leading out of Africa through the Sahara, the Nile Valley, and the Red Sea coast have been proposed as migration routes for anatomically modern humans 80,000-130,000 years ago. During this time climate conditions in the Sahara were wetter than present day, and monsoon rainfall fed rivers that flowed across the desert landscape. The location and timing of these rivers may have supported human migration northward from central Africa to the Mediterranean coast, and onwards to Europe or Asia. Here, we use palaeoclimate rainfall and a hydrological model to spatially simulate and quantitatively test the existence of three major rivers crossing the Sahara from south to north during the time of human migration. We provide evidence that, given realistic underlying climatology, the well-known Sahabi and Kufrah rivers very likely flowed across modern day Libya and reached the coast. More unexpectedly an additional river crossed the core of the Sahara through Algeria (Irharhar river) and flowed into the Chotts basin. The Irharhar river is unique, because it links locations in central Africa experiencing monsoon climates with temperate coastal Mediterranean environments where food and resources were likely abundant. From an ecological perspective, this little-known corridor may prove to be the most parsimonious migration route. Support for the Irharar as a viable migration corridor is provided by its geographic proximity to middle Stone Age archaeological artefacts found in North Africa. Our new, highly novel approach provides the first quantitative analysis of the likelihood that rivers occurred during the critical period of human migration out of Africa. Simulated probability of surface water in North Africa during the last interglacial and the location of tools and ornaments from the Middle Stone Age.

The Cumberland River Flood of 2010 and Corps Reservoir Operations

NASA Astrophysics Data System (ADS)

Charley, W.; Hanbali, F.; Rohrbach, B.

2010-12-01

On Saturday, May 1, 2010, heavy rain began falling in the Cumberland River Valley and continued through the following day. 13.5 inches was measured at Nashville, an unprecedented amount that doubled the previous 2-day record, and exceeded the May monthly total record of 11 inches. Elsewhere in the valley, amounts of over 19 inches were measured. The frequency of this storm was estimated to exceed the one-thousand year event. This historic rainfall brought large scale flooding to the Cumberland-Ohio-Tennessee River Valleys, and caused over 2 billion dollars in damages, despite the numerous flood control projects in the area, including eight U.S. Army Corps of Engineers projects. The vast majority of rainfall occurred in drainage areas that are uncontrolled by Corps flood control projects, which lead to the wide area flooding. However, preliminary analysis indicates that operations of the Corps projects reduced the Cumberland River flood crest in Nashville by approximately five feet. With funding from the American Recovery and Reinvestment Act (ARRA) of 2009, hydrologic, hydraulic and reservoir simulation models have just been completed for the Cumberland-Ohio-Tennessee River Valleys. These models are being implemented in the Corps Water Management System (CWMS), a comprehensive data acquisition and hydrologic modeling system for short-term decision support of water control operations in real time. The CWMS modeling component uses observed rainfall and forecasted rainfall to compute forecasts of river flows into and downstream of reservoirs, using HEC-HMS. Simulation of reservoir operations, utilizing either the HEC-ResSim or CADSWES RiverWare program, uses these flow scenarios to provide operational decision information for the engineer. The river hydraulics program, HEC-RAS, computes river stages and water surface profiles for these scenarios. An inundation boundary and depth map of water in the flood plain can be calculated from the HEC-RAS results using ArcInfo. The economic impacts of the different inundation depths are computed by HEC-FIA. The user-configurable sequence of modeling software allows engineers to evaluate operational decisions for reservoirs and other control structures, and view and compare hydraulic and economic impacts for various “what if?” scenarios. This paper reviews the Cumberland River May 2010 event, the impact of Corps reservoirs and reservoir operations and the expected future benefits and effects of the ARRA funded models and CWMS on future events for this area.

The CI-Flow Project: A System for Total Water Level Prediction from the Summit to the Sea

DTIC Science & Technology

2011-11-01

round and may be applied to all types of coastal storms , including intense cool- season extratropical cyclones (i.e., nor’easters). In addition...associated with waves, tides, storm surge, rivers, and rainfall, including interactions at the tidal/surge interface Within this project, Cl-FLOW addresses...presented for Hurricane Isabel (2003), Hurricane Earl (20I0), and Tropical Storm Nicole (2010) for the Tar -Pamlico and Neuse River basins of North

Environmental water demand assessment under climate change conditions.

PubMed

Sarzaeim, Parisa; Bozorg-Haddad, Omid; Fallah-Mehdipour, Elahe; Loáiciga, Hugo A

2017-07-01

Measures taken to cope with the possible effects of climate change on water resources management are key for the successful adaptation to such change. This work assesses the environmental water demand of the Karkheh river in the reach comprising Karkheh dam to the Hoor-al-Azim wetland, Iran, under climate change during the period 2010-2059. The assessment of the environmental demand applies (1) representative concentration pathways (RCPs) and (2) downscaling methods. The first phase of this work projects temperature and rainfall in the period 2010-2059 under three RCPs and with two downscaling methods. Thus, six climatic scenarios are generated. The results showed that temperature and rainfall average would increase in the range of 1.7-5.2 and 1.9-9.2%, respectively. Subsequently, flows corresponding to the six different climatic scenarios are simulated with the unit hydrographs and component flows from rainfall, evaporation, and stream flow data (IHACRES) rainfall-runoff model and are input to the Karkheh reservoir. The simulation results indicated increases of 0.9-7.7% in the average flow under the six simulation scenarios during the period of analysis. The second phase of this paper's methodology determines the monthly minimum environmental water demands of the Karkheh river associated with the six simulation scenarios using a hydrological method. The determined environmental demands are compared with historical ones. The results show that the temporal variation of monthly environmental demand would change under climate change conditions. Furthermore, some climatic scenarios project environmental water demand larger than and some of them project less than the baseline one.

Neglected sources of pharmaceuticals in river water--footprints of a Reggae festival.

PubMed

Daneshvar, Atlasi; Svanfelt, Jesper; Kronberg, Leif; Weyhenmeyer, Gesa A

2012-02-01

Wastewater treatment plants (WWTPs) are commonly considered as the main source of pharmaceuticals in surface waters. Here, however, we show that an open-air festival, attracting approximately 10,000 visitors per year at the shores of River Fyris upstream of Uppsala WWTP, can temporarily result in a higher pharmaceutical input into the river water than the WWTP. Studying the influence of Uppsala Reggae festival on the occurrence of ten commonly used acidic and basic pharmaceuticals upstream, in the effluent, and downstream of the Uppsala WWTP, we found that occasional heavy rainfalls during the festival in 2008 severely increased the mass flows of all pharmaceuticals at the WWTP upstream site. Also, strong increases in ammonium (210-fold), nitrate (21-fold), and total nitrogen (21-fold) mass flows were observed. The pharmaceutical mass flows at the upstream site were up to 3.4 times higher than those observed in the WWTP effluent. In contrast, in 2009, the festival was not accompanied with rainfalls and no major additional input of pharmaceuticals and nitrogen was observed. The findings of this study give new insights into risk assessments and are relevant for monitoring programmes.

Runoff and leaching of metolachlor from Mississippi River alluvial soil during seasons of average and below-average rainfall.

PubMed

Southwick, Lloyd M; Appelboom, Timothy W; Fouss, James L

2009-02-25

The movement of the herbicide metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] via runoff and leaching from 0.21 ha plots planted to corn on Mississippi River alluvial soil (Commerce silt loam) was measured for a 6-year period, 1995-2000. The first three years received normal rainfall (30 year average); the second three years experienced reduced rainfall. The 4-month periods prior to application plus the following 4 months after application were characterized by 1039 +/- 148 mm of rainfall for 1995-1997 and by 674 +/- 108 mm for 1998-2000. During the normal rainfall years 216 +/- 150 mm of runoff occurred during the study seasons (4 months following herbicide application), accompanied by 76.9 +/- 38.9 mm of leachate. For the low-rainfall years these amounts were 16.2 +/- 18.2 mm of runoff (92% less than the normal years) and 45.1 +/- 25.5 mm of leachate (41% less than the normal seasons). Runoff of metolachlor during the normal-rainfall seasons was 4.5-6.1% of application, whereas leaching was 0.10-0.18%. For the below-normal periods, these losses were 0.07-0.37% of application in runoff and 0.22-0.27% in leachate. When averages over the three normal and the three less-than-normal seasons were taken, a 35% reduction in rainfall was characterized by a 97% reduction in runoff loss and a 71% increase in leachate loss of metolachlor on a percent of application basis. The data indicate an increase in preferential flow in the leaching movement of metolachlor from the surface soil layer during the reduced rainfall periods. Even with increased preferential flow through the soil during the below-average rainfall seasons, leachate loss (percent of application) of the herbicide remained below 0.3%. Compared to the average rainfall seasons of 1995-1997, the below-normal seasons of 1998-2000 were characterized by a 79% reduction in total runoff and leachate flow and by a 93% reduction in corresponding metolachlor movement via these routes. An added observation in the study was that neither runoff of rainfall nor runoff loss of metolachlor was influenced by the presence of subsurface drains, compared to the results from plots without such drains that were described in an earlier paper.

Groundwater dynamics in a two-dimensional aquifer

NASA Astrophysics Data System (ADS)

Jules, Valentin; Devauchelle, Olivier; Lajeunesse, Eric

2017-11-01

During a rain event, water infiltrates into the ground where it flows slowly towards a river. The time scale and the geometry of this flow control the chemical composition and the discharge of the river. We use a tank filled with glass beads to simulate this process in a simplified laboratory experiment. A sprinkler pipe generates rain, which infiltrates into the porous material. Groundwater exits this laboratory aquifer through a side of the tank. Guérin et al. (2014) investigated the case of a quasi-horizontal flow. In nature, however, groundwater often follows non-horizontal flowlines. To create a vertical flow, we place the outlet of our experiment high above its bottom. We find that, during rainfall, the discharge Q increases as the rainfall rate R times the square root of time t (Q Rt 1 / 2). This laboratory aquifer thus responds linearly to the forcing. However, long after the rain has stopped, the discharge decreases as the inverse square of time (Q t-2), although linear systems of finite size typically relax exponentially. We investigate this surprising behavior using a combination of complex analysis and numerical methods.

Reconstructing the Santa Tecla flash flood in the Ondara River (Ebro Basin, NE Spain)

NASA Astrophysics Data System (ADS)

Balasch, J. C.; Tuset, J.; Ramos, M. C.; Martínez-Casasnovas, J. A.

2009-09-01

The Santa Tecla flood may be considered the most catastrophic rainfall event in the modern history of Catalonia (NE Iberian Peninsula), and one of the most important in the Western Mediterranean Basin. This event took place during the night between 22nd and 23rd September 1874, in which torrential convective rainfalls generated significant flash floods in most of the small streams in the southern half of Catalonia (i.e. Ondara, Corb, Francolí and Siurana catchments). More than 570 people died, 150 of which in the town of Tàrrega, by the Ondara River. Despite being one of the last huge floods of the pre-instrumental era and, consequently, without any precipitation or flow data, the event was reconstructed both hydraulically and hydrologically for the Ondara River at Tàrrega (150 km2). Thus, the maximum water level and the temporal evolution of the flood were obtained, respectively, from several epigraphic limnimarks found in Tàrrega and from the event description recorded in historical documents. Additionally, the information from local archaeological sites allowed the reconstruction of the fluvial section at Tàrrega at the end of the 19th century. Finally, some old cellars flooded during the event provided information about sediment concentration at the peak flow. The methodology put into practice for the event reconstruction had two stages. The first stage was the hydraulic modelling, which estimated the peak flow. The input data used were the maximum water level given by the limnimetric marks, a digital terrain model of the river bed shape, and the stream and floodplain roughness and channel slope (which were considered similar to the present ones, according to archaeological data). The hydraulic model used was the unidimensional HEC-RAS (USACE), applied in several cross sections of the Ondara River at Tàrrega. The second stage was the hydrological modelling. The objective of this stage was to derive the event hyetograph from the above calculated peak flow and the hydrologic response of the basin. This hydrologic behaviour, that is the relation between the hyetograph and the hydrograph, was estimated taking into account rainfall duration (6-8 hours according to historical documents), basin characteristics, soil type, soil land use and cover and the antecedent soil moisture, using SCS Curve Number method. After that, a transfer Synthetic Unitary Hydrograph function and a wave propagation method (Muskingum) were applied to describe the discharge evolution and the water routing into the stream channel. The software used in this stage was the HEC-HMS (USACE). The results of the hydraulic simulation at the Sant Agustí street cross section were the following: a) a maximum water depth of 6.16 m above the original river bed, b) a mean water velocity of about 2 m•s-1, c) a peak flow of 996 m3•s-1 (increased by 480 m3•s-1 from the Cercavins River downstream Tàrrega), and d) a specific peak discharge of the event of 6.6 m3•s-1•km-2, which exceeds the values of the 500-year return period floods compiled from the Ebro drainage basin systematic database. From the information obtained in the flooded cellars, the sediment concentration during the peak flow was estimated in 11.2% (in volume), characteristic of a hyperconcentrated flow. The water level reached in the abovepresented cross section is partly explained by the recently discovered Sant Agustí Bridge, buried until now in the river bed. The results of the hydrologic modelling were: a) a surface runoff total volume of 12 hm3, b) a runoff coefficient of about 35.5%, c) a lagtime of 2.5-3 hours, and d) if the previous soil humidity for the Curve Number method was low (situation I), a total rainfall of 225 mm with a peak intensity higher than 100 mm•h-1 is needed; if the previous soil humidity for the Curve Number method was medium (situation II), a total rainfall of 156 mm with a peak intensity of about 70 mm•h-1 occurs. Rainfall values for medium previous moisture condition (II) represent a 1000-year return period according to the regional systematic data.

Climate change and land use drivers of fecal bacteria in tropical Hawaiian rivers

Treesearch

Ayron M. Strauch; Richard A. Mackenzie; Gregory L. Bruland; Ralph Tingley; Christian P. Giardina

2014-01-01

Potential shifts in rainfall driven by climate change are anticipated to affect watershed processes (e.g., soil moisture, runoff, stream flow), yet few model systems exist in the tropics to test hypotheses about how these processes may respond to these shifts. We used a sequence of nine watersheds on Hawaii Island spanning 3000 mm (7500–4500 mm) of mean annual rainfall...

Filling the observational void: Scientific value and quantitative validation of hydrometeorological data from a community-based monitoring programme

NASA Astrophysics Data System (ADS)

Walker, David; Forsythe, Nathan; Parkin, Geoff; Gowing, John

2016-07-01

This study shows how community-based hydrometeorological monitoring programmes can provide reliable high-quality measurements comparable to formal observations. Time series of daily rainfall, river stage and groundwater levels obtained by a local community in Dangila woreda, northwest Ethiopia, have passed accepted quality control standards and have been statistically validated against formal sources. In a region of low-density and declining formal hydrometeorological monitoring networks, a situation shared by much of the developing world, community-based monitoring can fill the observational void providing improved spatial and temporal characterisation of rainfall, river flow and groundwater levels. Such time series data are invaluable in water resource assessment and management, particularly where, as shown here, gridded rainfall datasets provide gross under or over estimations of rainfall and where groundwater level data are non-existent. Discussions with the local community during workshops held at the setup of the monitoring programme and since have demonstrated that the community have become engaged in the project and have benefited from a greater hydrological knowledge and sense of ownership of their resources. This increased understanding and empowerment is at the relevant scale required for effective community-based participatory management of shallow groundwater and river catchments.

Movement of a large, slow-moving landslide in the North Island, New Zealand, controlled by porewater pressure and river flow

NASA Astrophysics Data System (ADS)

McColl, Samuel; Holdsworth, Charlotte; Massey, Chris

2017-04-01

New Zealand has 7000 mapped large (> 2 ha) landslides, most of which occur in the Neogene cover rocks, and many of which are active. Active landslides in New Zealand damage lifeline infrastructure, entire suburbs, agricultural land, and they deliver large but little-quantified sediment load to rivers. Despite their prevalence in the landscape and these impacts, much remains unknown of their initiation, movement patterns and processes, or their contributions to landscape evolution. This research assesses how toe cutting and rainfall at a daily to seasonal timescale drive movement of a large (50 hectare) slow-moving, translational rockslide that is severely damaging a farm in the Rangitikei catchment, central North Island. Geomorphological mapping has been undertaken to define the landslide boundary, drainage lines and to assess zones of movements. Since July 2015, 3-monthly GPS-occupations of a survey mark network, and hourly time-lapse photography of the toe of the landslide have been used to identify the distribution and patterns of landslide movement. Pixel-tracking software is being used to quantify movement at the toe from the time-lapse photography at an daily timescale. Movement data are being compared with river flow data (i.e. toe cutting potential) and local rainfall and groundwater from a nearby site (i.e. a proxy for porewater-pressure changes at the landslide). Results so far indicate movement of several mm to cm per year in the upper part of the landslide through a block sliding mechanism, increasing to several metres per year towards the toe where block-sliding transitions sharply to more mobile earth flow-slide behaviour. In the upper part of the landslide, vertical displacements are larger closer to earth flow-slide zone, expressed as decimetre to metre-scale scarps and mini-grabens. The failure surface is exposed at the toe, which is being actively cut by a major river, and reveals a highly remoulded landslide body 1-3 metres thick, overlaying intact sandstone. Based on existing structural data and the landslide surface morphology it is assumed that the landslide thickens to about 60 m towards the head. The geomorphology suggests extension and thinning of the landslide body - which corroborates the movement data showing movement rates at the head (mm per year) increasing downslope to some metres per year at the toe - and without a zone of compression at the toe, suggesting near-continuous toe-unloading. Movement is fastest in the winter-spring months when water tables are high due to reduced evapotranspiration and slightly greater rainfall. However, this period also coincides with a period of higher river flow and flood events (i.e. toe cutting), and the landslide appears to be particularly sensitive (i.e. surges forward) following high river flow events that cut the toe. This observation suggests that movement is driven by both local and catchment-scale rainfall events.

Estimation of River Discharge at Ungauged Catchment using GIS Map Correlation Method as Applied in Sta. Lucia River in Mauban, Quezon, Philippines

NASA Astrophysics Data System (ADS)

Monjardin, Cris Edward F.; Uy, Francis Aldrine A.; Tan, Fibor J.

2017-06-01

This paper presents use of GIS Map Correlation Method, a novel method of Prediction of Ungauged Basin, which is used to estimate the river flow at an ungauged catchment. The PUB Method used here intends to reduce the time and costs of data gathering procedure since it will just rely on a reference calibrated watershed that has almost the same characteristics in terms of slope, curve number, land cover, climatic condition, and average basin elevation. Furthermore, this utilized a set of modelling software which used digital elevation models (DEM), rainfall and discharge data. The researchers estimated the river flow of Sta. Lucia River in Quezon province, which is the ungauged catchment. The researchers assessed 11 gauged catchments and determined which basin could be correlated to Sta. Lucia. After finding the most correlated basin, the researchers used the data considering adjusted parameters of the gauged catchment. In evaluating the accuracy of the method, the researchers simulated a rainfall event in the said catchment and compared the actual discharge and the generated discharge from HEC-HMS. The researchers found out that method showed a good fit in the compared results, proving GMC Method is effective for use in the calibration of ungauged catchments.

Probability density functions for use when calculating standardised drought indices

NASA Astrophysics Data System (ADS)

Svensson, Cecilia; Prosdocimi, Ilaria; Hannaford, Jamie

2015-04-01

Time series of drought indices like the standardised precipitation index (SPI) and standardised flow index (SFI) require a statistical probability density function to be fitted to the observed (generally monthly) precipitation and river flow data. Once fitted, the quantiles are transformed to a Normal distribution with mean = 0 and standard deviation = 1. These transformed data are the SPI/SFI, which are widely used in drought studies, including for drought monitoring and early warning applications. Different distributions were fitted to rainfall and river flow data accumulated over 1, 3, 6 and 12 months for 121 catchments in the United Kingdom. These catchments represent a range of catchment characteristics in a mid-latitude climate. Both rainfall and river flow data have a lower bound at 0, as rains and flows cannot be negative. Their empirical distributions also tend to have positive skewness, and therefore the Gamma distribution has often been a natural and suitable choice for describing the data statistically. However, after transformation of the data to Normal distributions to obtain the SPIs and SFIs for the 121 catchments, the distributions are rejected in 11% and 19% of cases, respectively, by the Shapiro-Wilk test. Three-parameter distributions traditionally used in hydrological applications, such as the Pearson type 3 for rainfall and the Generalised Logistic and Generalised Extreme Value distributions for river flow, tend to make the transformed data fit better, with rejection rates of 5% or less. However, none of these three-parameter distributions have a lower bound at zero. This means that the lower tail of the fitted distribution may potentially go below zero, which would result in a lower limit to the calculated SPI and SFI values (as observations can never reach into this lower tail of the theoretical distribution). The Tweedie distribution can overcome the problems found when using either the Gamma or the above three-parameter distributions. The Tweedie is a three-parameter distribution which includes the Gamma distribution as a special case. It is bounded below at zero and has enough flexibility to fit most behaviours observed in the data. It does not always outperform the three-parameter distributions, but the rejection rates are similar. In addition, for certain parameter values the Tweedie distribution has a positive mass at zero, which means that ephemeral streams and months with zero rainfall can be modelled. It holds potential for wider application in drought studies in other climates and types of catchment.

Human activities and its Responses to Glacier Melt Water Over Tarim River Basin

NASA Astrophysics Data System (ADS)

He, Hai; Zhou, Shenbei; Bai, Minghao

2017-04-01

Tarim River Basin lies in the south area of Xinjiang Uygur Autonomous Region, the north-west area of China. It is the longest inland river of China. Being far away from ocean and embraced by high mountains, Tarim River Basin is the typical arid region in the world. The intensity of human activities increased rapidly in Tarim River Basin since 1980's and water resources lacking is the major issue restricting the development of social economy. The glacier melt water plays an important role for the regional social and economic development, and it accounts for 40% of mountain-pass runoff. It is a fragile mutual-dependent relationship between local sustainable development and runoff. Under the background of global change glacier melt water process has also changed especially in the arid and semi-arid region. Due to climate change, glacier in Tarim River Basin has melted in an observed way since 1980s, together with increasing trend of annual rainfall and virgin flow in mountain basins. Correspondingly, human activity gets more frequent since 1970s, resulting into the obvious fragile mutual-dependent relationship between basin runoff and water use amount. Through an analysis of meteorological, hydrological and geographical observation data from 1985 to 2015, this thesis make a multi-factor variance analysis of population, cultivation area, industrial development and runoff in upstream and mid-stream of Tarim River under changing conditions. Furthermore, the regulation function of natural factors and water demand management factors on relationship between runoff and water using amount are discussed, including temperature, rainfall, and evaporation, water conservation technology and soil-water exploitation administrative institutions. It concludes that: first, increase in glacier runoff, rainfall amount, and virgin flow haven't notably relieved ecological issue in Tarim River Basin, and even has promoted water use behaviour in different flowing areas and noticeably reduced the influence on water demand management. Second, water demand management factors positively relate to ecological improvement in Tarim River Basin. Third, after a further prediction on glacier melt with fuzzy neural network, it finds that the weaker adjustment influence of glacier runoff would put Tarim River Basin into a much weaker mutual-dependent relationship. The research believes that if short-term activity of society has wrongly adapted to runoff increase from faster glacier melt, it would put social development and ecological recovery of Tarim River Basin into a higher vulnerable way. Key words: Tarim River Basin, Changing Condition, Glacier Melt, mutual-dependent vulnerability

Changing trends of rainfall and sediment fluxes in the Kinta River catchment, Malaysia

NASA Astrophysics Data System (ADS)

Ismail, W. R.; Hashim, M.

2015-03-01

The Kinta River, draining an area of 2566 km2, originates in the Korbu Mountain in Perak, Malaysia, and flows through heterogeneous, mixed land uses ranging from extensive forests to mining, rubber and oil palm plantations, and urban development. A land use change analysis of the Kinta River catchment was carried out together with assessment of the long-term trend in rainfall and sediment fluxes. The Mann-Kendall test was used to examine and assess the long-term trends in rainfall and its relationship with the sediment discharge trend. The land use analysis shows that forests, water bodies and mining land declined whilst built and agricultural land use increased significantly. This has influenced the sediment flux of the catchment. However, most of the rainfall stations and river gauging stations are experiencing an increasing trends, except at Kinta river at Tg. Rambutan. Sediment flux shows a net erosion for the period from 1961 to 1969. The total annual sediment discharge in the Kinta River catchment was low with an average rate of 1,757 t/km2/year. From 1970 to 1985, the annual sediment yield rose to an average rate of 4062 t/km2/year. Afterwards, from 1986 to 1993, the total annual sediment discharge decreased to an average rate of 1,306 t/km2/year and increased back during the period 1994 to 2000 to 2109 t/km2/year. From 2001 to 2006 the average sediment flux rate declined to 865 t/km2/year. The decline was almost 80% from the 1970s. High sediment flux in the early 1970s is partly associated with reduced tin mining activities in the area. This decreasing trend in sediment delivery leaving the Kinta River catchment is expected to continue dropping in the future.

Potential of commercial microwave link network derived rainfall for river runoff simulations

NASA Astrophysics Data System (ADS)

Smiatek, Gerhard; Keis, Felix; Chwala, Christian; Fersch, Benjamin; Kunstmann, Harald

2017-03-01

Commercial microwave link networks allow for the quantification of path integrated precipitation because the attenuation by hydrometeors correlates with rainfall between transmitter and receiver stations. The networks, operated and maintained by cellphone companies, thereby provide completely new and country wide precipitation measurements. As the density of traditional precipitation station networks worldwide is significantly decreasing, microwave link derived precipitation estimates receive increasing attention not only by hydrologists but also by meteorological and hydrological services. We investigate the potential of microwave derived precipitation estimates for streamflow prediction and water balance analyses, exemplarily shown for an orographically complex region in the German Alps (River Ammer). We investigate the additional value of link derived rainfall estimations combined with station observations compared to station and weather radar derived values. Our river runoff simulation system employs a distributed hydrological model at 100 × 100 m grid resolution. We analyze the potential of microwave link derived precipitation estimates for two episodes of 30 days with typically moderate river flow and an episode of extreme flooding. The simulation results indicate the potential of this novel precipitation monitoring method: a significant improvement in hydrograph reproduction has been achieved in the extreme flooding period that was characterized by a large number of local strong precipitation events. The present rainfall monitoring gauges alone were not able to correctly capture these events.

Runoff Analysis Considering Orographical Features Using Dual Polarization Radar Rainfall

NASA Astrophysics Data System (ADS)

Noh, Hui-seong; Shin, Hyun-seok; Kang, Na-rae; Lee, Choong-Ke; Kim, Hung-soo

2013-04-01

Recently, the necessity for rainfall estimation and forecasting using the radar is being highlighted, due to the frequent occurrence of torrential rainfall resulting from abnormal changes of weather. Radar rainfall data represents temporal and spatial distributions properly and replace the existing rain gauge networks. It is also frequently applied in many hydrologic field researches. However, the radar rainfall data has an accuracy limitation since it estimates rainfall, by monitoring clouds and precipitation particles formed around the surface of the earth(1.5-3km above the surface) or the atmosphere. In a condition like Korea where nearly 70% of the land is covered by mountainous areas, there are lots of restrictions to use rainfall radar, because of the occurrence of beam blocking areas by topography. This study is aiming at analyzing runoff and examining the applicability of (R(Z), R(ZDR) and R(KDP)) provided by the Han River Flood Control Office(HRFCO) based on the basin elevation of Nakdong river watershed. For this purpose, the amount of radar rainfall of each rainfall event was estimated according to three sub-basins of Nakdong river watershed with the average basin elevation above 400m which are Namgang dam, Andong dam and Hapcheon dam and also another three sub-basins with the average basin elevation below 150m which are Waegwan, Changryeong and Goryeong. After runoff analysis using a distribution model, Vflo model, the results were reviewed and compared with the observed runoff. This study estimated the rainfall by using the radar-rainfall transform formulas, (R(Z), R(Z,ZDR) and R(Z,ZDR,KDP) for four stormwater events and compared the results with the point rainfall of the rain gauge. As the result, it was overestimated or underestimated, depending on rainfall events. Also, calculation indicates that the values from R(Z,ZDR) and R(Z,ZDR,KDP) relatively showed the most similar results. Moreover the runoff analysis using the estimated radar rainfall is performed. Then hydrologic component of the runoff hydrographs, peak flows and total runoffs from the estimated rainfall and the observed rainfall are compared. The results show that hydrologic components have high fluctuations depending on storm rainfall event. Thus, it is necessary to choose appropriate radar rainfall data derived from the above radar rainfall transform formulas to analyze the runoff of radar rainfall. The simulated hydrograph by radar in the three basins of agricultural areas is more similar to the observed hydrograph than the other three basins of mountainous areas. Especially the peak flow and shape of hydrograph of the agricultural areas is much closer to the observed ones than that of mountainous areas. This result comes from the difference of radar rainfall depending on the basin elevation. Therefore we need the examination of radar rainfall transform formulas following rainfall event and runoff analysis based on basin elevation for the improvement of radar rainfall application. Acknowledgment This study was financially supported by the Construction Technology Innovation Program(08-Tech-Inovation-F01) through the Research Center of Flood Defence Technology for Next Generation in Korea Institute of Construction & Transportation Technology Evaluation and Planning(KICTEP) of Ministry of Land, Transport and Maritime Affairs(MLTM)

Flooding in Clark and Lincoln Counties, Nevada, December 2004 and January 2005

USGS Publications Warehouse

Ryan, Roslyn

2006-01-01

Introduction: A regional storm passed through the Las Vegas Valley, Nevada, on December 28-29, 2004, producing up to 2 inches of rain in a 24-hour period. Due to the intense, sustained rainfall, streamflow along Las Vegas Wash was near the record discharges of July 8, 1999. Additional rainfall in December and in January, combined with an early warming trend, resulted in record flooding along Meadow Valley Wash, Muddy River, and Virgin River, January 10-11, 2005 (figs. 1 and 2). On January 7, this warming trend resulted in about a 15?F (degree Fahrenheit) increase over the previous week (fig. 2). This temperature spike, along with further precipitation, caused much of the snow pack in the surrounding mountain ranges to melt and run off into the valleys. These two factors led to the major flood events in Clark and Lincoln Counties during December 2004 and January 2005. Total flood and storm damage for Lincoln County was estimated at $9.4 million and $4.5 million for Clark County (Manning, 2005). Clark County generally is drained by the Las Vegas and Meadow Valley Washes, and the Muddy and Virgin River systems. Las Vegas Valley is drained by Duck Creek, Tropicana Wash (not in fig. 1), Flamingo Wash, Las Vegas Wash, and several smaller tributaries (fig. 1). Water in these drainages generally flows eastward through Las Vegas to Las Vegas Wash and on toward Lake Mead, an impoundment of the Colorado River. The Virgin River originates in southern Utah, flows past Littlefield, AZ, through Mesquite, NV, and into the Overton Arm of Lake Mead. Meadow Valley Wash flows from Ursine, NV, through Caliente, NV, continues southeast through Moapa Valley, and into the Muddy River at Glendale, NV. The Muddy River flows southeast through Moapa Valley into the Overton Arm of Lake Mead (Kane and Wilson, 2000).

Precipitation, pH and metal load in AMD river basins: an application of fuzzy clustering algorithms to the process characterization.

PubMed

Grande, J A; Andújar, J M; Aroba, J; de la Torre, M L; Beltrán, R

2005-04-01

In the present work, Acid Mine Drainage (AMD) processes in the Chorrito Stream, which flows into the Cobica River (Iberian Pyrite Belt, Southwest Spain) are characterized by means of clustering techniques based on fuzzy logic. Also, pH behavior in contrast to precipitation is clearly explained, proving that the influence of rainfall inputs on the acidity and, as a result, on the metal load of a riverbed undergoing AMD processes highly depends on the moment when it occurs. In general, the riverbed dynamic behavior is the response to the sum of instant stimuli produced by isolated rainfall, the seasonal memory depending on the moment of the target hydrological year and, finally, the own inertia of the river basin, as a result of an accumulation process caused by age-long mining activity.

Opportunities for hydrologic research in the Congo Basin

NASA Astrophysics Data System (ADS)

Alsdorf, Douglas; Beighley, Ed; Laraque, Alain; Lee, Hyongki; Tshimanga, Raphael; O'Loughlin, Fiachra; Mahé, Gil; Dinga, Bienvenu; Moukandi, Guy; Spencer, Robert G. M.

2016-06-01

We review the published results on the Congo Basin hydrology and summarize the historic and ongoing research. Annual rainfall is ~1900 mm/yr along an east-west trend across the basin, decreasing northward and southward to ~1100 mm/yr. Historic studies using lysimeters, pans, and models suggest that the annual potential evapotranspiration varies little across the basin at 1100 to 1200 mm/yr. Over the past century, river discharge data have been collected at hundreds of stream gauges with historic and recent data at 96 locations now publicly available. Congo River discharge at Kinshasa-Brazzaville experienced an increase of 21% during the 1960-1970 decade in comparison to most other decades. Satellite altimetry measurements of high and low flows show that water levels in the "Cuvette Centrale" wetland are 0.5 m to 3.0 m higher in elevation than the immediately adjacent Congo River levels. Wetland water depths are shallow at about a meter and there does not appear to be many sizable channels across the "Cuvette"; thus, wetland flows are diffusive. Cuvette waters alone are estimated to emit about 0.5 Pg CH4 and CO2 equivalents/yr, an amount that is significant compared to global carbon evasions. Using these results, we suggest seven hypotheses that focus on the source of the Cuvette waters and how these leave the wetland, on the river discharge generated by historic rainfall, on the connection between climate change and the rainfall-runoff generated by the migrating "tropical rainbelt," on deforestation and hydroelectric power generation, and on the amount of carbon emitted from Congo waters.

Opportunities for Hydrologic Research in the Congo Basin

NASA Astrophysics Data System (ADS)

Alsdorf, D. E.; Beighley, E.; Laraque, A.; Lee, H.; Tshimanga, R.; O'Loughlin, F.; Mahe, G. M.; Dinga, B. J.; Moukandi, G.; Spencer, R.

2016-12-01

We review the published results on the Congo Basin hydrology and summarize the historic and ongoing research. Annual rainfall is 1900 mm/yr along an east-west trend across the basin, decreasing northward and southward to 1100 mm/yr. Historic studies using lysimeters, pans, and models suggest that the annual potential evapotranspiration varies little across the basin at 1100 to 1200 mm/yr. Over the past century, river discharge data have been collected at hundreds of stream gauges with historic and recent data at 96 locations now publicly available. Congo River discharge at Kinshasa-Brazzaville experienced an increase of 21% during the 1960-1970 decade in comparison to most other decades. Satellite altimetry measurements of high and low flows show that water levels in the "Cuvette Centrale" wetland are 0.5m to 3.0m higher in elevation than the immediately adjacent Congo River levels. Wetland water depths are shallow at about a meter and there does not appear to be many sizable channels across the "Cuvette"; thus, wetland flows are diffusive. Cuvette waters alone are estimated to emit about 0.5 Pg CH4 and CO2 equivalents/yr, an amount that is significant compared to global carbon evasions. Using these results, we suggest seven hypotheses that focus on the source of the Cuvette waters and how these leave the wetland, on the river discharge generated by historic rainfall, on the connection between climate change and the rainfall-runoff generated by the migrating "tropical rainbelt," on deforestation and hydroelectric power generation, and on the amount of carbon emitted from Congo waters.

Comparison of Precipitation from Gauge and Tropical Rainfall Measurement Mission (TRMM) for River Basins of India

NASA Astrophysics Data System (ADS)

Mondal, A.; Chandniha, S. K.; Lakshmi, V.; Kundu, S.; Hashemi, H.

2017-12-01

This study compares the monthly precipitation from the gridded rain gauge data collected by India Meteorological Department (IMD) and the retrievals from the Tropical Rainfall Measurement Mission (TRMM) for the river basins of India using the TRMM Multisatellite Precipitation Analysis (TMPA) version 7 (V7). The IMD and TMPA datasets have the same spatial resolution (0.25°×0.25°) and extend from 1998 to 2013. The TRMM data accuracy for the river basins is assessed by comparison with IMD using root mean square error (RMSE), normalized mean square error (NMSE), Nash-Sutcliffe coefficient (NASH) and correlation coefficient (CC) methods. The Mann-Kendall (MK) and modified Mann-Kendall (MMK) tests have been applied for analyzing the data trend, and the change has been detected by Sen's Slope using both data sets for annual and seasonal time periods. The change in intensity of precipitation is estimated by percentage for comparing actual differences in various river basins. Variation in precipitation is high (>100 mm represents >15% of average annual precipitation) in Brahmaputra, rivers draining into Myanmar (RDM), rivers draining into Bangladesh (RDB), east flowing rivers between Mahanadi and Godavari (EMG), east flowing rivers between Pennar and Cauvery (EPC), Cauvery and Tapi. The NASH and CC values vary between 0.80 to 0.98 and 0.87 to 0.99 in all river basins except area of north Ladakh not draining into Indus (NLI) and east flowing rivers south of Cauvery (ESC), while RMSE and NMSE vary from 15.95 to 101.68 mm and 2.66 to 58.38 mm, respectively. The trends for TMPA and IMD datasets from 1998 to 2013 are quite similar in MK (except 4 river basins) and MMK (except 3 river basins). The estimated results imply that the TMPA precipitation show good agreement and can be used in climate studies and hydrological simulations in locations/river basins where the number of rain gauge stations is not adequate to quantify the spatial variability of precipitation. Keywords: Precipitation data comparison, IMD, TRMM, river basins, Mann-Kendall test

Flood risk reduction and flow buffering as ecosystem services - Part 1: Theory on flow persistence, flashiness and base flow

NASA Astrophysics Data System (ADS)

van Noordwijk, Meine; Tanika, Lisa; Lusiana, Betha

2017-05-01

Flood damage reflects insufficient adaptation of human presence and activity to location and variability of river flow in a given climate. Flood risk increases when landscapes degrade, counteracted or aggravated by engineering solutions. Efforts to maintain and restore buffering as an ecosystem function may help adaptation to climate change, but this require quantification of effectiveness in their specific social-ecological context. However, the specific role of forests, trees, soil and drainage pathways in flow buffering, given geology, land form and climate, remains controversial. When complementing the scarce heavily instrumented catchments with reliable long-term data, especially in the tropics, there is a need for metrics for data-sparse conditions. We present and discuss a flow persistence metric that relates transmission to river flow of peak rainfall events to the base-flow component of the water balance. The dimensionless flow persistence parameter Fp is defined in a recursive flow model and can be estimated from limited time series of observed daily flow, without requiring knowledge of spatially distributed rainfall upstream. The Fp metric (or its change over time from what appears to be the local norm) matches local knowledge concepts. Inter-annual variation in the Fp metric in sample watersheds correlates with variation in the flashiness index used in existing watershed health monitoring programmes, but the relationship between these metrics varies with context. Inter-annual variation in Fp also correlates with common base-flow indicators, but again in a way that varies between watersheds. Further exploration of the responsiveness of Fp in watersheds with different characteristics to the interaction of land cover and the specific realisation of space-time patterns of rainfall in a limited observation period is needed to evaluate interpretation of Fp as an indicator of anthropogenic changes in watershed conditions.

Annual variability of PAH concentrations in the Potomac River watershed

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

Maher, I.L.; Foster, G.D.

1995-12-31

Dynamics of organic contaminant transport in a large river system is influenced by annual variability in organic contaminant concentrations. Surface runoff and groundwater input control the flow of river waters. They are also the two major inputs of contaminants to river waters. The annual variability of contaminant concentrations in rivers may or may not represent similar trends to the flow changes of river waters. The purpose of the research is to define the annual variability in concentrations of polycyclic aromatic hydrocarbons (PAH) in riverine environment. To accomplish this, from March 1992 to March 1995 samples of Potomac River water weremore » collected monthly or bimonthly downstream of the Chesapeake Bay fall line (Chain Bridge) during base flow and main storm flow hydrologic conditions. Concentrations of selected PAHs were measured in the dissolved phase and the particulate phase via GC/MS. The study of the annual variability of PAH concentrations will be performed through comparisons of PAH concentrations seasonally, annually, and through study of PAH concentration river discharge dependency and rainfall dependency. For selected PAHs monthly and annual loadings will be estimated based on their measured concentrations and average daily river discharge. The monthly loadings of selected PAHs will be compared by seasons and annually.« less

Assessing the impacts of climate change and socio-economic changes on flow and phosphorus flux in the Ganga river system.

PubMed

Jin, L; Whitehead, P G; Sarkar, S; Sinha, R; Futter, M N; Butterfield, D; Caesar, J; Crossman, J

2015-06-01

Anthropogenic climate change has impacted and will continue to impact the natural environment and people around the world. Increasing temperatures and altered rainfall patterns combined with socio-economic factors such as population changes, land use changes and water transfers will affect flows and nutrient fluxes in river systems. The Ganga river, one of the largest river systems in the world, supports approximately 10% global population and more than 700 cities. Changes in the Ganga river system are likely to have a significant impact on water availability, water quality, aquatic habitats and people. In order to investigate these potential changes on the flow and water quality of the Ganga river, a multi-branch version of INCA Phosphorus (INCA-P) model has been applied to the entire river system. The model is used to quantify the impacts from a changing climate, population growth, additional agricultural land, pollution control and water transfers for 2041-2060 and 2080-2099. The results provide valuable information about potential effects of different management strategies on catchment water quality.

The effects of Missouri River mainstem reservoir system operations on 2011 flooding using a Precipitation-Runoff Modeling System model: Chapter K in 2011 Floods of the Central United States

USGS Publications Warehouse

Haj, Adel E.; Christiansen, Daniel E.; Viger, Roland J.

2014-01-01

In 2011 the Missouri River Mainstem Reservoir System (Reservoir System) experienced the largest volume of flood waters since the initiation of record-keeping in the nineteenth century. The high levels of runoff from both snowpack and rainfall stressed the Reservoir System’s capacity to control flood waters and caused massive damage and disruption along the river. The flooding and resulting damage along the Missouri River brought increased public attention to the U.S. Army Corps of Engineers (USACE) operation of the Reservoir System. To help understand the effects of Reservoir System operation on the 2011 Missouri River flood flows, the U.S. Geological Survey Precipitation-Runoff Modeling System was used to construct a model of the Missouri River Basin to simulate flows at streamgages and dam locations with the effects of Reservoir System operation (regulation) on flow removed. Statistical tests indicate that the Missouri River Precipitation-Runoff Modeling System model is a good fit for high-flow monthly and annual stream flow estimation. A comparison of simulated unregulated flows and measured regulated flows show that regulation greatly reduced spring peak flow events, consolidated two summer peak flow events to one with a markedly decreased magnitude, and maintained higher than normal base flow beyond the end of water year 2011. Further comparison of results indicate that without regulation, flows greater than those measured would have occurred and been sustained for much longer, frequently in excess of 30 days, and flooding associated with high-flow events would have been more severe.

Rainfall-runoff characteristics and effects of increased urban density on streamflow and infiltration in the eastern part of the San Jacinto River basin, Riverside County, California

USGS Publications Warehouse

Guay, Joel R.

2002-01-01

To better understand the rainfall-runoff characteristics of the eastern part of the San Jacinto River Basin and to estimate the effects of increased urbanization on streamflow, channel infiltration, and land-surface infiltration, a long-term (1950?98) time series of monthly flows in and out of the channels and land surfaces were simulated using the Hydrologic Simulation Program- FORTRAN (HSPF) rainfall-runoff model. Channel and land-surface infiltration includes rainfall or runoff that infiltrates past the zone of evapotranspiration and may become ground-water recharge. The study area encompasses about 256 square miles of the San Jacinto River drainage basin in Riverside County, California. Daily streamflow (for periods with available data between 1950 and 1998), and daily rainfall and evaporation (1950?98) data; monthly reservoir storage data (1961?98); and estimated mean annual reservoir inflow data (for 1974 conditions) were used to calibrate the rainfall-runoff model. Measured and simulated mean annual streamflows for the San Jacinto River near San Jacinto streamflow-gaging station (North-South Fork subbasin) for 1950?91 and 1997?98 were 14,000 and 14,200 acre-feet, respectively, a difference of 1.4 percent. The standard error of the mean for measured and simulated annual streamflow in the North-South Fork subbasin was 3,520 and 3,160 acre-feet, respectively. Measured and simulated mean annual streamflows for the Bautista Creek streamflow-gaging station (Bautista Creek subbasin) for 1950?98 were 980 acre-feet and 991 acre-feet, respectively, a difference of 1.1 percent. The standard error of the mean for measured and simulated annual streamflow in the Bautista Creek subbasin was 299 and 217 acre-feet, respectively. Measured and simulated annual streamflows for the San Jacinto River above State Street near San Jacinto streamflow-gaging station (Poppet subbasin) for 1998 were 23,400 and 23,500 acre-feet, respectively, a difference of 0.4 percent. The simulated mean annual streamflow for the State Street gaging station at the outlet of the study basin and the simulated mean annual basin infiltration (combined infiltration from all the channels and land surfaces) were 8,720 and 41,600 acre-feet, respectively, for water years 1950-98. Simulated annual streamflow at the State Street gaging station ranged from 16.8 acre-feet in water year 1961 to 70,400 acre-feet in water year 1993, and simulated basin infiltration ranged from 2,770 acre-feet in water year 1961 to 149,000 acre-feet in water year 1983.The effects of increased urbanization on the hydrology of the study basin were evaluated by increasing the size of the effective impervious and non-effective impervious urban areas simulated in the calibrated rainfall-runoff model by 50 and 100 percent, respectively. The rainfall-runoff model simulated a long-term time series of monthly flows in and out of the channels and land surfaces using daily rainfall and potential evaporation data for water years 1950?98. Increasing the effective impervious and non-effective impervious urban areas by 100 percent resulted in a 5-percent increase in simulated mean annual streamflow at the State Street gaging station, and a 2.2-percent increase in simulated basin infiltration. Results of a frequency analysis of the simulated annual streamflow at the State Street gaging station showed that when effective impervious and non-effective impervious areas were increased 100 percent, simulated annual streamflow increased about 100 percent for low-flow conditions and was unchanged for high-flow conditions. The simulated increase in streamflow at the State Street gaging station potentially could infiltrate along the stream channel further downstream, outside of the model area.

Hydrological classification of natural flow regimes to support environmental flow assessments in intensively regulated Mediterranean rivers, Segura River Basin (Spain).

PubMed

Belmar, Oscar; Velasco, Josefa; Martinez-Capel, Francisco

2011-05-01

Hydrological classification constitutes the first step of a new holistic framework for developing regional environmental flow criteria: the "Ecological Limits of Hydrologic Alteration (ELOHA)". The aim of this study was to develop a classification for 390 stream sections of the Segura River Basin based on 73 hydrological indices that characterize their natural flow regimes. The hydrological indices were calculated with 25 years of natural monthly flows (1980/81-2005/06) derived from a rainfall-runoff model developed by the Spanish Ministry of Environment and Public Works. These indices included, at a monthly or annual basis, measures of duration of droughts and central tendency and dispersion of flow magnitude (average, low and high flow conditions). Principal Component Analysis (PCA) indicated high redundancy among most hydrological indices, as well as two gradients: flow magnitude for mainstream rivers and temporal variability for tributary streams. A classification with eight flow-regime classes was chosen as the most easily interpretable in the Segura River Basin, which was supported by ANOSIM analyses. These classes can be simplified in 4 broader groups, with different seasonal discharge pattern: large rivers, perennial stable streams, perennial seasonal streams and intermittent and ephemeral streams. They showed a high degree of spatial cohesion, following a gradient associated with climatic aridity from NW to SE, and were well defined in terms of the fundamental variables in Mediterranean streams: magnitude and temporal variability of flows. Therefore, this classification is a fundamental tool to support water management and planning in the Segura River Basin. Future research will allow us to study the flow alteration-ecological response relationship for each river type, and set the basis to design scientifically credible environmental flows following the ELOHA framework.

A national-scale seasonal hydrological forecast system: development and evaluation over Britain

NASA Astrophysics Data System (ADS)

Bell, Victoria A.; Davies, Helen N.; Kay, Alison L.; Brookshaw, Anca; Scaife, Adam A.

2017-09-01

Skilful winter seasonal predictions for the North Atlantic circulation and northern Europe have now been demonstrated and the potential for seasonal hydrological forecasting in the UK is now being explored. One of the techniques being used combines seasonal rainfall forecasts provided by operational weather forecast systems with hydrological modelling tools to provide estimates of seasonal mean river flows up to a few months ahead. The work presented here shows how spatial information contained in a distributed hydrological model typically requiring high-resolution (daily or better) rainfall data can be used to provide an initial condition for a much simpler forecast model tailored to use low-resolution monthly rainfall forecasts. Rainfall forecasts (hindcasts) from the GloSea5 model (1996 to 2009) are used to provide the first assessment of skill in these national-scale flow forecasts. The skill in the combined modelling system is assessed for different seasons and regions of Britain, and compared to what might be achieved using other approaches such as use of an ensemble of historical rainfall in a hydrological model, or a simple flow persistence forecast. The analysis indicates that only limited forecast skill is achievable for Spring and Summer seasonal hydrological forecasts; however, Autumn and Winter flows can be reasonably well forecast using (ensemble mean) rainfall forecasts based on either GloSea5 forecasts or historical rainfall (the preferred type of forecast depends on the region). Flow forecasts using ensemble mean GloSea5 rainfall perform most consistently well across Britain, and provide the most skilful forecasts overall at the 3-month lead time. Much of the skill (64 %) in the 1-month ahead seasonal flow forecasts can be attributed to the hydrological initial condition (particularly in regions with a significant groundwater contribution to flows), whereas for the 3-month ahead lead time, GloSea5 forecasts account for ˜ 70 % of the forecast skill (mostly in areas of high rainfall to the north and west) and only 30 % of the skill arises from hydrological memory (typically groundwater-dominated areas). Given the high spatial heterogeneity in typical patterns of UK rainfall and evaporation, future development of skilful spatially distributed seasonal forecasts could lead to substantial improvements in seasonal flow forecast capability, potentially benefitting practitioners interested in predicting hydrological extremes, not only in the UK but also across Europe.

Coast and river mouths, Columbia, South America

NASA Technical Reports Server (NTRS)

1982-01-01

Numerous rivers in Ecuador and Columbia stand out in this South American Pacific coastal scene (1.5N, 79.0W). This region has one of the highest rainfalls in the world with the consequent heavy cloud cover and it is rare to be able to photograph the surface. The Pacific mountain drainage area is small but produces a large volume of runoff and sediment flow into the ocean.

Use of a constucted wetland to reduce nonpoint-source pesticide contamination of the Lourens River, South America

Treesearch

Ralf Schulz

2000-01-01

The Lourens River, Western Cape, South Africa, and its tributaries situated in an intensively cultivated orchard area receive pesticide contamination during rainfall-induced runoff and during spraydrift. A 0.44-ha constructed wetland, built in 1991 in one of the tributaries (summer flow 0.03 m3 per second), was studied in order to assess its effectiveness in reducing...

Bioengineering Technology to Control River Soil Erosion using Vetiver (Vetiveria Zizaniodes)

NASA Astrophysics Data System (ADS)

Sriwati, M.; Pallu, S.; Selintung, M.; Lopa, R.

2018-04-01

Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock or dissolved material from one location on the earth’s crust, and then transport it away to another location. Bioengineering is an attempt to maximise the use of vegetation components along riverbanks to cope with landslides and erosion of river cliffs and another riverbank damage. This study aims to analyze the bioengineering of Vetiver as a surface layer for soil erosion control using slope of 100, 200, and 300. This study is conducted with 3 variations of rain intensity (I), at 103 mm/hour, 107 mm/hour, and 130 mm/hour by using rainfall simulator tool. In addition, the USLE (Universal Soil Loss Equation) method is used in order to measure the rate of soil erosion. In this study, there are few USLE model parameters were used such as rainfall erosivity factor, soil erodibility factor, length-loss slope and stepness factor, cover management factor, and support practise factor. The results demonstrated that average of reduction of erosion rate using Vetiver, under 3 various rainfalls, namely rainfall intensity 103 mm/hr had reduced 84.971%, rainfall intensity 107 mm/hr had reduced 86.583 %, rainfall intensity 130 mm/hr had reduced 65.851%.

Characterizing fluvial heavy metal pollutions under different rainfall conditions: Implication for aquatic environment protection.

PubMed

Zhang, Lixun; Zhao, Bo; Xu, Gang; Guan, Yuntao

2018-09-01

Globally, fluvial heavy metal (HM) pollution has recently become an increasingly severe problem. However, few studies have investigated the variational characteristics of fluvial HMs after rain over long periods (≥1 year). The Dakan River in Xili Reservoir watershed (China) was selected as a case study to investigate pollution levels, influencing factors, and sources of HMs under different rainfall conditions during 2015 and 2016. Fluvial HMs showed evident spatiotemporal variations attributable to the coupled effects of pollution generation and rainfall diffusion. Fluvial HM concentrations were significantly associated with rainfall characteristics (e.g., rainfall intensity, rainfall amount, and antecedent dry period) and river flow, which influenced the generation and the transmission of fluvial HMs in various ways. Moreover, this interrelationship depended considerably on the HM type and particle size distribution. Mn, Pb, Cr, and Ni were major contributors to high values of the comprehensive pollution index; therefore, they should be afforded special attention. Additionally, quantitative source apportionment of fluvial HMs was conducted by combining principal component analysis with multiple linear regression and chemical mass balance models to obtain comprehensive source profiles. Finally, an environment-friendly control strategy coupling "source elimination" and "transport barriers" was proposed for aquatic environment protection. Copyright © 2018 Elsevier B.V. All rights reserved.

Analysis and mapping of post-fire hydrologic hazards for the 2002 Hayman, Coal Seam, and Missionary Ridge wildfires, Colorado

USGS Publications Warehouse

Elliott, J.G.; Smith, M.E.; Friedel, M.J.; Stevens, M.R.; Bossong, C.R.; Litke, D.W.; Parker, R.S.; Costello, C.; Wagner, J.; Char, S.J.; Bauer, M.A.; Wilds, S.R.

2005-01-01

Wildfires caused extreme changes in the hydrologic, hydraulic, and geomorphologic characteristics of many Colorado drainage basins in the summer of 2002. Detailed assessments were made of the short-term effects of three wildfires on burned and adjacent unburned parts of drainage basins. These were the Hayman, Coal Seam, and Missionary Ridge wildfires. Longer term runoff characteristics that reflect post-fire drainage basin recovery expected to develop over a period of several years also were analyzed for two affected stream reaches: the South Platte River between Deckers and Trumbull, and Mitchell Creek in Glenwood Springs. The 10-, 50-, 100-, and 500-year flood-plain boundaries and water-surface profiles were computed in a detailed hydraulic study of the Deckers-to-Trumbull reach. The Hayman wildfire burned approximately 138,000 acres (216 square miles) in granitic terrain near Denver, and the predominant potential hazard in this area is flooding by sediment-laden water along the large tributaries to and the main stem of the South Platte River. The Coal Seam wildfire burned approximately 12,200 acres (19.1 square miles) near Glenwood Springs, and the Missionary Ridge wildfire burned approximately 70,500 acres (110 square miles) near Durango, both in areas underlain by marine shales where the predominant potential hazard is debris-flow inundation of low-lying areas. Hydrographs and peak discharges for pre-burn and post-burn scenarios were computed for each drainage basin and tributary subbasin by using rainfall-runoff models because streamflow data for most tributary subbasins were not available. An objective rainfall-runoff model calibration method based on nonlinear regression and referred to as the ?objective calibration method? was developed and applied to rainfall-runoff models for three burned areas. The HEC-1 rainfall-runoff model was used to simulate the pre-burn rainfall-runoff processes in response to the 100-year storm, and HEC-HMS was used for runoff hydrograph generation. Post-burn rainfall-runoff parameters were determined by adjusting the runoff-curve numbers on the basis of a weighting procedure derived from the U.S. Soil Conservation Service (now the National Resources Conservation Service) equation for precipitation excess and the effect of burn severity. This weighting procedure was determined to be more appropriate than simple area weighting because of the potentially marked effect of even small burned areas on the runoff hydrograph in individual drainage basins. Computed water-peak discharges from HEC-HMS models were increased volumetrically to account for increased sediment concentrations that are expected as a result of accelerated erosion after burning. Peak discharge estimates for potential floods in the South Platte River were increased by a factor that assumed a volumetric sediment concentration (Cv) of 20 percent. Flood hydrographs for the South Platte River and Mitchell Creek were routed down main-stem channels using watershed-routing algorithms included in the HEC-HMS rainfall-runoff model. In areas subject to debris flows in the Coal Seam and Missionary Ridge burned areas, debris-flow discharges were simulated by 100-year rainfall events, and the inflow hydrographs at tributary mouths were simulated by using the objective calibration method. Sediment concentrations (Cv) used in debris-flow simulations were varied through the event, and were initial Cv 20 percent, mean Cv approximately 31 percent, maximum Cv 48 percent, Cv 43 percent at the time of the water hydrograph peak, and Cv 20 percent for the duration of the event. The FLO-2D flood- and debris-flow routing model was used to delineate the area of unconfined debris-flow inundation on selected alluvial fan and valley floor areas. A method was developed to objectively determine the post-fire recovery period for the Hayman and Coal Seam burned areas using runoff-curve numbers (RCN) for all drainage basins for a 50-year period. A

Downstream aggradation owing to lava dome extrusion and rainfall runoff at Volcán Santiaguito, Guatemala

USGS Publications Warehouse

Harris, Andrew J. L.; Vallance, James W.; Kimberly, Paul; Rose, William I.; Matías, Otoniel; Bunzendahl, Elly; Flynn, Luke P.; Garbeil, Harold

2006-01-01

Persistent lava extrusion at the Santiaguito dome complex (Guatemala) results in continuous lahar activity and river bed aggradation downstream of the volcano. We present a simple method that uses vegetation indices extracted from Landsat Thematic Mapper (TM) data to map impacted zones. Application of this technique to a time series of 21 TM images acquired between 1987 and 2000 allow us to map, measure, and track temporal and spatial variations in the area of lahar impact and river aggradation.In the proximal zone of the fluvial system, these data show a positive correlation between extrusion rate at Santiaguito (E), aggradation area 12 months later (Aprox), and rainfall during the intervening 12 months (Rain12): Aprox=3.92+0.50 E+0.31 ln(Rain12) (r2=0.79). This describes a situation in which an increase in sediment supply (extrusion rate) and/or a means to mobilize this sediment (rainfall) results in an increase in lahar activity (aggraded area). Across the medial zone, we find a positive correlation between extrusion rate and/or area of proximal aggradation and medial aggradation area (Amed): Amed=18.84-0.05 Aprox - 6.15 Rain12 (r2=0.85). Here the correlation between rainfall and aggradation area is negative. This describes a situation in which increased sediment supply results in an increase in lahar activity but, because it is the zone of transport, an increase in rainfall serves to increase the transport efficiency of rivers flowing through this zone. Thus, increased rainfall flushes the medial zone of sediment.These quantitative data allow us to empirically define the links between sediment supply and mobilization in this fluvial system and to derive predictive relationships that use rainfall and extrusion rates to estimate aggradation area 12 months hence.

Simulation of Sediment and Cesium Transport in the Ukedo River and the Ogi Dam Reservoir during a Rainfall Event using the TODAM Code

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

Onishi, Yasuo; Yokuda, Satoru T.; Kurikami, Hiroshi

2014-03-28

The accident at the Fukushima Daiichi Nuclear Power Plant in March 2011 caused widespread environmental contamination. Although decontamination activities have been performed in residential areas of the Fukushima area, decontamination of forests, rivers, and reservoirs is still controversial because of the economical, ecological, and technical difficulties. Thus, an evaluation of contaminant transport in such an environment is important for safety assessment and for implementation of possible countermeasures to reduce radiation exposure to the public. The investigation revealed that heavy rainfall events play a significant role in transporting radioactive cesium deposited on the land surface, via soil erosion and sediment transportmore » in rivers. Therefore, we simulated the sediment and cesium transport in the Ukedo River and its tributaries in Fukushima Prefecture, including the Ogaki Dam Reservoir, and the Ogi Dam Reservoir of the Oginosawa River in Fukushima Prefecture during and after a heavy rainfall event by using the TODAM (Time-dependent, One-dimensional Degradation And Migration) code. The main outcomes are the following: • Suspended sand is mostly deposited on the river bottom. Suspended silt and clay, on the other hand, are hardly deposited in the Ukedo River and its tributaries except in the Ogaki Dam Reservoir in the Ukedo River even in low river discharge conditions. • Cesium migrates mainly during high river discharge periods during heavy rainfall events. Silt and clay play more important roles in cesium transport to the sea than sand does. • The simulation results explain variations in the field data on cesium distributions in the river. Additional field data currently being collected and further modeling with these data may shed more light on the cesium distribution variations. • Effects of 40-hour heavy rainfall events on clay and cesium transport continue for more than a month. This is because these reservoirs slow down the storm-induced high flow moving through these reservoirs. • The reservoirs play a major role as a sink of sediment and cesium in the river systems. Some amounts of sediment pass through them along with cesium in dissolved and clay-sorbed cesium forms. • Effects of countermeasures such as overland decontamination, dam control and sorbent injection were tentatively estimated. The simulation suggested that overland decontamination and sorbent injection would be effective for decreasing the contamination of water in the reservoir and in the river below the dam.« less

Impact of urban WWTP and CSO fluxes on river peak flow extremes under current and future climate conditions.

PubMed

Keupers, Ingrid; Willems, Patrick

2013-01-01

The impact of urban water fluxes on the river system outflow of the Grote Nete catchment (Belgium) was studied. First the impact of the Waste Water Treatment Plant (WWTP) and the Combined Sewer Overflow (CSO) outflows on the river system for the current climatic conditions was determined by simulating the urban fluxes as point sources in a detailed, hydrodynamic river model. Comparison was made of the simulation results on peak flow extremes with and without the urban point sources. In a second step, the impact of climate change scenarios on the urban fluxes and the consequent impacts on the river flow extremes were studied. It is shown that the change in the 10-year return period hourly peak flow discharge due to climate change (-14% to +45%) was in the same order of magnitude as the change due to the urban fluxes (+5%) in current climate conditions. Different climate change scenarios do not change the impact of the urban fluxes much except for the climate scenario that involves a strong increase in rainfall extremes in summer. This scenario leads to a strong increase of the impact of the urban fluxes on the river system.

Numerical simulation of scouring-deposition variations caused by rainfall-induced landslides in the upstream of Zengwun River, Taiwan

NASA Astrophysics Data System (ADS)

Lee, Ming-Hsi; Liao, Yi-Wen; Tsai, Kuang-Jung

2017-04-01

In recent years, the increasing sediment disasters of severe rainfall-induced landslides on human lives and lifeline facilities worldwide have advanced the necessity to find out both economically acceptable and useful techniques to predict the occurrence and destructive power of the disasters. In August 2009, Typhoon Morakot brought a large amount of rainfall with both high intensity and long duration to a vast area of Taiwan. Unfortunately, this resulted in a catastrophic landslide in watershed of Zengwun-River reservoir, southern Taiwan. Meanwhile, large amounts of landslides were formed in the upstream of Zengwun River. The major scope of this study is to apply numerical model to simulate the scouring-deposition variations caused by rainfall-induced landslides that occurred in the upstream of Zengwun River during Typhoon Morakot. This study proposed the relation diagrams of the intermediate diameter (d50), recurrence interval (T) and scouring-deposition depth (D), and applied the diagrams to understand the impacts of the scouring-deposition variations on the structures for water and soil conservation and their measurements. Based on the simulation of scouring-deposition variation at the Da-Bu dam and Da-Bang dam, this study also discussed the scouring-deposition variations of different sections under different scenarios (including flow rate, intermediate diameters and structures). In summary, the result suggested that the diagrams of the intermediate diameter, recurrence interval and scouring-deposition depth could be used as the reference for designing the check dams, ground sills and lateral constructions.

Identification of Renewable Energy Potential in Ciberang River, Cisarua Village, Bogor, West Java

NASA Astrophysics Data System (ADS)

Sari Damayanthi Sebayang, Ika; Hidayat, Acep; Indah, Nur

2018-03-01

This paper presented the analysis of potential energy in Ciberang River, Cisarua Village, Bogor West Java. The objective of this work is to ascertain the availability of water due to rainfall (discharge simulation). The simulation required data in the form of rainfall intensity, climate, evapotranspiration and water discharge. The rainfall station is determined by Thiessen Method and located in Cisalak-Baru Station. Rainfall data from 1997-2012 was used. The area of Ciberang River basin is about 46.19 km2 and not influenced by the change of land area used per year. The height of waterfall allowed was 160 meters due to its topography. The result of water availability was analysed using NRECA method and calibration was done using water data recording (Automatic Water Level Recorder) in downstream of Ciberang-Sabagi station. Calibrated result analysis was then plotted to show the Flow Duration Curve (FDC). Potential capacity of power was obtained from the amount of discharge with the reliability level of 50-60%. At 60% reliability level, calculation of discharge equal to 5.8 m3/s and then was used for design parameter. The generated power capacity is 45,813,400.21 kWh/year with the assumptions of net head 159 meters, generator’s efficiency of 0.95 and turbine’s efficiency of 0.85. The result shows that Ciberang River has a potential to be developed as a hydro power plant.

Water quality assessment of a small peri-urban river using low and high frequency monitoring.

PubMed

Ivanovsky, A; Criquet, J; Dumoulin, D; Alary, C; Prygiel, J; Duponchel, L; Billon, G

2016-05-18

The biogeochemical behaviors of small rivers that pass through suburban areas are difficult to understand because of the multi-origin inputs that can modify their behavior. In this context, a monitoring strategy has been designed for the Marque River, located in Lille Metropolitan area of northern France, that includes both low-frequency monitoring over a one-year period (monthly sampling) and high frequency monitoring (measurements every 10 minutes) in spring and summer. Several environmental and chemical parameters are evaluated including rainfall events, river flow, temperature, dissolved oxygen, turbidity, conductivity, nutritive salts and dissolved organic matter. Our results from the Marque River show that (i) it is impacted by both urban and agricultural inputs, and as a consequence, the concentrations of phosphate and inorganic nitrogen have degraded the water quality; (ii) the classic photosynthesis/respiration processes are disrupted by the inputs of organic matter and nutritive salts; (iii) during dry periods, the urban sewage inputs (treated or not) are more important during the day, as indicated by higher river flows and maximal concentrations of ammonium; (iv) phosphate concentrations depend on oxygen contents in the river; (v) high nutrient concentrations result in eutrophication of the Marque River with lower pH and oxygen concentrations in summer. During rainfalls, additional inputs of ammonium, biodegradable organic matter as well as sediment resuspension result in anoxic events; and finally (vi) concentrations of nitrate are approximately constant over the year, except in winter when higher inputs can be recorded. Having better identified the processes responsible for the observed water quality, a more informed remediation effort can be put forward to move this suburban river to a good status of water quality.

Multifractal characterisation of a simulated surface flow: A case study with Multi-Hydro in Jouy-en-Josas, France

NASA Astrophysics Data System (ADS)

Gires, Auguste; Abbes, Jean-Baptiste; da Silva Rocha Paz, Igor; Tchiguirinskaia, Ioulia; Schertzer, Daniel

2018-03-01

In this paper we suggest to innovatively use scaling laws and more specifically Universal Multifractals (UM) to analyse simulated surface runoff and compare the retrieved scaling features with the rainfall ones. The methodology is tested on a 3 km2 semi-urbanised with a steep slope study area located in the Paris area along the Bièvre River. First Multi-Hydro, a fully distributed model is validated on this catchment for four rainfall events measured with the help of a C-band radar. The uncertainty associated with small scale unmeasured rainfall, i.e. occurring below the 1 km × 1 km × 5 min observation scale, is quantified with the help of stochastic downscaled rainfall fields. It is rather significant for simulated flow and more limited on overland water depth for these rainfall events. Overland depth is found to exhibit a scaling behaviour over small scales (10 m-80 m) which can be related to fractal features of the sewer network. No direct and obvious dependency between the overland depth multifractal features (quality of the scaling and UM parameters) and the rainfall ones was found.

Assessment of catchments' flooding potential: a physically-based analytical tool

NASA Astrophysics Data System (ADS)

Botter, G.; Basso, S.; Schirmer, M.

2016-12-01

The assessment of the flooding potential of river catchments is critical in many research and applied fields, ranging from river science and geomorphology to urban planning and the insurance industry. Predicting magnitude and frequency of floods is key to prevent and mitigate the negative effects of high flows, and has therefore long been the focus of hydrologic research. Here, the recurrence intervals of seasonal flow maxima are estimated through a novel physically-based analytic approach, which links the extremal distribution of streamflows to the stochastic dynamics of daily discharge. An analytical expression of the seasonal flood-frequency curve is provided, whose parameters embody climate and landscape attributes of the contributing catchment and can be estimated from daily rainfall and streamflow data. Only one parameter, which expresses catchment saturation prior to rainfall events, needs to be calibrated on the observed maxima. The method has been tested in a set of catchments featuring heterogeneous daily flow regimes. The model is able to reproduce characteristic shapes of flood-frequency curves emerging in erratic and persistent flow regimes and provides good estimates of seasonal flow maxima in different climatic regions. Performances are steady when the magnitude of events with return times longer than the available sample size is estimated. This makes the approach especially valuable for regions affected by data scarcity.

Estimated probabilities, volumes, and inundation areas depths of potential postwildfire debris flows from Carbonate, Slate, Raspberry, and Milton Creeks, near Marble, Gunnison County, Colorado

USGS Publications Warehouse

Stevens, Michael R.; Flynn, Jennifer L.; Stephens, Verlin C.; Verdin, Kristine L.

2011-01-01

During 2009, the U.S. Geological Survey, in cooperation with Gunnison County, initiated a study to estimate the potential for postwildfire debris flows to occur in the drainage basins occupied by Carbonate, Slate, Raspberry, and Milton Creeks near Marble, Colorado. Currently (2010), these drainage basins are unburned but could be burned by a future wildfire. Empirical models derived from statistical evaluation of data collected from recently burned basins throughout the intermountain western United States were used to estimate the probability of postwildfire debris-flow occurrence and debris-flow volumes for drainage basins occupied by Carbonate, Slate, Raspberry, and Milton Creeks near Marble. Data for the postwildfire debris-flow models included drainage basin area; area burned and burn severity; percentage of burned area; soil properties; rainfall total and intensity for the 5- and 25-year-recurrence, 1-hour-duration-rainfall; and topographic and soil property characteristics of the drainage basins occupied by the four creeks. A quasi-two-dimensional floodplain computer model (FLO-2D) was used to estimate the spatial distribution and the maximum instantaneous depth of the postwildfire debris-flow material during debris flow on the existing debris-flow fans that issue from the outlets of the four major drainage basins. The postwildfire debris-flow probabilities at the outlet of each drainage basin range from 1 to 19 percent for the 5-year-recurrence, 1-hour-duration rainfall, and from 3 to 35 percent for 25-year-recurrence, 1-hour-duration rainfall. The largest probabilities for postwildfire debris flow are estimated for Raspberry Creek (19 and 35 percent), whereas estimated debris-flow probabilities for the three other creeks range from 1 to 6 percent. The estimated postwildfire debris-flow volumes at the outlet of each creek range from 7,500 to 101,000 cubic meters for the 5-year-recurrence, 1-hour-duration rainfall, and from 9,400 to 126,000 cubic meters for the 25-year-recurrence, 1-hour-duration rainfall. The largest postwildfire debris-flow volumes were estimated for Carbonate Creek and Milton Creek drainage basins, for both the 5- and 25-year-recurrence, 1-hour-duration rainfalls. Results from FLO-2D modeling of the 5-year and 25-year recurrence, 1-hour rainfalls indicate that the debris flows from the four drainage basins would reach or nearly reach the Crystal River. The model estimates maximum instantaneous depths of debris-flow material during postwildfire debris flows that exceeded 5 meters in some areas, but the differences in model results between the 5-year and 25-year recurrence, 1-hour rainfalls are small. Existing stream channels or topographic flow paths likely control the distribution of debris-flow material, and the difference in estimated debris-flow volume (about 25 percent more volume for the 25-year-recurrence, 1-hour-duration rainfall compared to the 5-year-recurrence, 1-hour-duration rainfall) does not seem to substantially affect the estimated spatial distribution of debris-flow material. Historically, the Marble area has experienced periodic debris flows in the absence of wildfire. This report estimates the probability and volume of debris flow and maximum instantaneous inundation area depths after hypothetical wildfire and rainfall. This postwildfire debris-flow report does not address the current (2010) prewildfire debris-flow hazards that exist near Marble.

Evidence of equilibrium peak runoff rates in steep tropical terrain on the island of Dominica during Tropical Storm Erika, August 27, 2015

NASA Astrophysics Data System (ADS)

Ogden, Fred L.

2016-11-01

Tropical Storm Erika was a weakly organized tropical storm when its center of circulation passed more than 150 km north of the island of Dominica on August 27, 2015. Hurricane hunter flights had difficulty finding the center of circulation as the storm encountered a high shear environment. Satellite and radar observations showed gyres imbedded within the broader circulation. Radar observations from Guadeloupe show that one of these gyres formed in convergent mid-level flow triggered by orographic convection over the island of Dominica. Gauge-adjusted radar rainfall data indicated between 300 and 750 mm of rainfall on Dominica, most of it over a four hour period. The result was widespread flooding, destruction of property, and loss of life. The extremity of the rainfall on steep watersheds covered with shallow soils was hypothesized to result in near-equilibrium runoff conditions where peak runoff rates equal the watershed-average peak rainfall rate minus a small constant loss rate. Rain gauge adjusted radar rainfall estimates and indirect peak discharge (IPD) measurements from 16 rivers at watershed areas ranging from 0.9 to 31.4 km2 using the USGS Slope-Area method allowed testing of this hypothesis. IPD measurements were compared against the global envelope of maximum observed flood peaks versus drainage area and against simulations using the U.S. Army Corps of Engineers Gridded Surface/Subsurface Hydrologic Analysis (GSSHA) model to detect landslide-affected peak flows. Model parameter values were estimated from the literature. Reasonable agreement was found between GSSHA simulated peak flows and IPD measurements in some watersheds. Results showed that landslide dam failure affected peak flows in 5 of the 16 rivers, with peak flows significantly greater than the envelope curve values for the flood of record for like-sized watersheds on the planet. GSSHA simulated peak discharges showed that the remaining 11 peak flow values were plausible. Simulations of an additional 24 watersheds ranging in size from 2.2 to 75.4 km2 provided confirmation that the IPD measurements varied from 40 to nearly 100% of the envelope curve value depending on storm-total rainfall. Results presented in this paper support the hypothesis that on average, the peak discharges scaled linearly with drainage area, and the constant of proportionality was equivalent to 134 mm h-1, or a unit discharge of 37.22 m3 s-1 km-2. The results also indicate that after the available watershed storage was filled after approximately 450-500 mm of rain fell, runoff efficiencies exceeded 50-60%, and peak runoff rates were more than 80% of the peak rainfall rate minus a small constant loss rate of 20 mm h-1. These findings have important implications for design of resilient infrastructure, and means that rainfall rate was the primary determinant of peak flows once the available storage was filled in the absences of landslide dam failure.

Regionalisation of low flow frequency curves for the Peninsular Malaysia

NASA Astrophysics Data System (ADS)

Mamun, Abdullah A.; Hashim, Alias; Daoud, Jamal I.

2010-02-01

SUMMARYRegional maps and equations for the magnitude and frequency of 1, 7 and 30-day low flows were derived and are presented in this paper. The river gauging stations of neighbouring catchments that produced similar low flow frequency curves were grouped together. As such, the Peninsular Malaysia was divided into seven low flow regions. Regional equations were developed using the multivariate regression technique. An empirical relationship was developed for mean annual minimum flow as a function of catchment area, mean annual rainfall and mean annual evaporation. The regional equations exhibited good coefficient of determination ( R2 > 0.90). Three low flow frequency curves showing the low, mean and high limits for each region were proposed based on a graphical best-fit technique. Knowing the catchment area, mean annual rainfall and evaporation in the region, design low flows of different durations can be easily estimated for the ungauged catchments. This procedure is expected to overcome the problem of data unavailability in estimating low flows in the Peninsular Malaysia.

Smart licensing and environmental flows: Modeling framework and sensitivity testing

NASA Astrophysics Data System (ADS)

Wilby, R. L.; Fenn, C. R.; Wood, P. J.; Timlett, R.; Lequesne, T.

2011-12-01

Adapting to climate change is just one among many challenges facing river managers. The response will involve balancing the long-term water demands of society with the changing needs of the environment in sustainable and cost effective ways. This paper describes a modeling framework for evaluating the sensitivity of low river flows to different configurations of abstraction licensing under both historical climate variability and expected climate change. A rainfall-runoff model is used to quantify trade-offs among environmental flow (e-flow) requirements, potential surface and groundwater abstraction volumes, and the frequency of harmful low-flow conditions. Using the River Itchen in southern England as a case study it is shown that the abstraction volume is more sensitive to uncertainty in the regional climate change projection than to the e-flow target. It is also found that "smarter" licensing arrangements (involving a mix of hands off flows and "rising block" abstraction rules) could achieve e-flow targets more frequently than conventional seasonal abstraction limits, with only modest reductions in average annual yield, even under a hotter, drier climate change scenario.

Global hotspots of river erosion under global warming

NASA Astrophysics Data System (ADS)

Plink-Bjorklund, P.; Reichler, T.

2017-12-01

Extreme precipitation plays a significant role for river hydrology, flood hazards and landscape response. For example, the September 2013 rainstorm in the Colorado Front Range evacuated the equivalent of hundreds to thousands of years of hillslope weathering products. Although promoted by steep topography, the Colorado event is clearly linked to rainfall intensity, since most of the 1100 debris flows occurred within the highest rainfall contour. Additional evidence for a strong link between extreme precipitation and river erosion comes from the sedimentary record, and especially from that of past greenhouse climates. The existence of such a link suggests that information about global rainfall patterns can be used to define regions of increased erosion potential. However, the question arises what rainfall criteria to use and how well the method works. A related question is how ongoing climate change and the corresponding shifts in rainfall might impact the results. Here, we use atmospheric reanalysis and output from a climate model to identify regions that are particularly susceptible to landscape change in response to extreme precipitation. In order to define the regions, we combine several hydroclimatological and geomorphological criteria into a single index of erosion potential. We show that for current climate, our criteria applied to atmospheric reanalysis or to climate model data successfully localize known areas of increased erosion potential, such as the Colorado region. We then apply our criteria to climate model data for future climate to document how the location, extent, and intensity of erosion hotspots are likely to change under global warming.

A new physically-based model considered antecedent rainfall for shallow landslide

NASA Astrophysics Data System (ADS)

Luo, Yu; He, Siming

2017-04-01

Rainfall is the most significant factor to cause landslide especially shallow landslide. In previous studies, rainfall intensity and duration are take part in the physically based model to determining the occurrence of the rainfall-induced landslides, but seldom considered the antecedent rainfall. In this study, antecedent rainfall is took into account to derive a new physically based model for shallow landslides prone area predicting at the basin scale. Based on the Rosso's equation of seepage flow considering the antecedent rainfall to construct the hillslope hydrology model. And then, the infinite slope stability theory is using to construct the slope stability model. At last, the model is apply in the Baisha river basin of Chengdu, Sichuan, China, and the results are compared with the one's from unconsidered antecedent rainfall. The results show that the model is simple, but has the capability of consider antecedent rainfall in the triggering mechanism of shallow landslide. Meanwhile, antecedent rainfall can make an obvious effect on shallow landslides, so in shallow landslide hazard assessment, the influence of the antecedent rainfall can't be ignored.

Evaluating the use of different precipitation datasets in simulating a flood event

NASA Astrophysics Data System (ADS)

Akyurek, Z.; Ozkaya, A.

2016-12-01

Floods caused by convective storms in mountainous regions are sensitive to the temporal and spatial variability of rainfall. Space-time estimates of rainfall from weather radar, satellites and numerical weather prediction models can be a remedy to represent pattern of the rainfall with some inaccuracy. However, there is a strong need for evaluation of the performance and limitations of these estimates in hydrology. This study aims to provide a comparison of gauge, radar, satellite (Hydro-Estimator (HE)) and numerical weather prediciton model (Weather Research and Forecasting (WRF)) precipitation datasets during an extreme flood event (22.11.2014) lasting 40 hours in Samsun-Turkey. For this study, hourly rainfall data from 13 ground observation stations were used in the analyses. This event having a peak discharge of 541 m3/sec created flooding at the downstream of Terme Basin. Comparisons were performed in two parts. First the analysis were performed in areal and point based manner. Secondly, a semi-distributed hydrological model was used to assess the accuracy of the rainfall datasets to simulate river flows for the flood event. Kalman Filtering was used in the bias correction of radar rainfall data compared to gauge measurements. Radar, gauge, corrected radar, HE and WRF rainfall data were used as model inputs. Generally, the HE product underestimates the cumulative rainfall amounts in all stations, radar data underestimates the results in cumulative sense but keeps the consistency in the results. On the other hand, almost all stations in WRF mean statistics computations have better results compared to the HE product but worse than the radar dataset. Results in point comparisons indicated that, trend of the rainfall is captured by the radar rainfall estimation well but radar underestimates the maximum values. According to cumulative gauge value, radar underestimated the cumulative rainfall amount by % 32. Contrary to other datasets, the bias of WRF is positive due to the overestimation of rainfall forecasts. It was seen that radar-based flow predictions demonstrated good potential for successful hydrological modeling. Moreover, flow predictions obtained from bias corrected radar rainfall values produced an increase in the peak flows compared to the ones obtained from radar data itself.

Adaptation of the concept of varying time of concentration within flood modelling: Theoretical and empirical investigations across the Mediterranean

NASA Astrophysics Data System (ADS)

Michailidi, Eleni Maria; Antoniadi, Sylvia; Koukouvinos, Antonis; Bacchi, Baldassare; Efstratiadis, Andreas

2017-04-01

The time of concentration, tc, is a key hydrological concept and often is an essential parameter of rainfall-runoff modelling, which has been traditionally tackled as a characteristic property of the river basin. However, both theoretical proof and empirical evidence imply that tc is a hydraulic quantity that depends on flow, and thus it should be considered as variable and not as constant parameter. Using a kinematic method approach, easily implemented in GIS environment, we first illustrate that the relationship between tc and the effective rainfall produced over the catchment is well-approximated by a power-type law, the exponent of which is associated with the slope of the longest flow path of the river basin. Next, we take advantage of this relationship to adapt the concept of varying time of concentration within flood modelling, and particularly the well-known SCS-CN approach. In this context, the initial abstraction ratio is also considered varying, while the propagation of the effective rainfall is employed through a parametric unit hydrograph, the shape of which is dynamically adjusted according to the runoff produced during the flood event. The above framework is tested in a number of Mediterranean river basins in Greece, Italy and Cyprus, ensuring faithful representation of most of the observed flood events. Based on the outcomes of this extended analysis, we provide guidance for employing this methodology for flood design studies in ungauged basins.

Hydrological modelling of the Mara River Basin, Kenya: Dealing with uncertain data quality and calibrating using river stage

NASA Astrophysics Data System (ADS)

Hulsman, P.; Bogaard, T.; Savenije, H. H. G.

2016-12-01

In hydrology and water resources management, discharge is the main time series for model calibration. Rating curves are needed to derive discharge from continuously measured water levels. However, assuring their quality is demanding due to dynamic changes and problems in accurately deriving discharge at high flows. This is valid everywhere, but even more in African socio-economic context. To cope with these uncertainties, this study proposes to use water levels instead of discharge data for calibration. Also uncertainties in rainfall measurements, especially the spatial heterogeneity needs to be considered. In this study, the semi-distributed rainfall runoff model FLEX-Topo was applied to the Mara River Basin. In this model seven sub-basins were distinguished and four hydrological response units with each a unique model structure based on the expected dominant flow processes. Parameter and process constrains were applied to exclude unrealistic results. To calibrate the model, the water levels were back-calculated from modelled discharges, using cross-section data and the Strickler formula calibrating parameter `k•s1/2', and compared to measured water levels. The model simulated the water depths well for the entire basin and the Nyangores sub-basin in the north. However, the calibrated and observed rating curves differed significantly at the basin outlet, probably due to uncertainties in the measured discharge, but at Nyangores they were almost identical. To assess the effect of rainfall uncertainties on the hydrological model, the representative rainfall in each sub-basin was estimated with three different methods: 1) single station, 2) average precipitation, 3) areal sub-division using Thiessen polygons. All three methods gave on average similar results, but method 1 resulted in more flashy responses, method 2 dampened the water levels due to averaging the rainfall and method 3 was a combination of both. In conclusion, in the case of unreliable rating curves, water level data can be used instead and a new rating curve can be calibrated. The effect of rainfall uncertainties on the hydrological model was insignificant.

The use of distributed hydrological models for the Gard 2002 flash flood event: Analysis of associated hydrological processes

NASA Astrophysics Data System (ADS)

Braud, Isabelle; Roux, Hélène; Anquetin, Sandrine; Maubourguet, Marie-Madeleine; Manus, Claire; Viallet, Pierre; Dartus, Denis

2010-11-01

SummaryThis paper presents a detailed analysis of the September 8-9, 2002 flash flood event in the Gard region (southern France) using two distributed hydrological models: CVN built within the LIQUID® hydrological platform and MARINE. The models differ in terms of spatial discretization, infiltration and water redistribution representation, and river flow transfer. MARINE can also account for subsurface lateral flow. Both models are set up using the same available information, namely a DEM and a pedology map. They are forced with high resolution radar rainfall data over a set of 18 sub-catchments ranging from 2.5 to 99 km2 and are run without calibration. To begin with, models simulations are assessed against post field estimates of the time of peak and the maximum peak discharge showing a fair agreement for both models. The results are then discussed in terms of flow dynamics, runoff coefficients and soil saturation dynamics. The contribution of the subsurface lateral flow is also quantified using the MARINE model. This analysis highlights that rainfall remains the first controlling factor of flash flood dynamics. High rainfall peak intensities are very influential of the maximum peak discharge for both models, but especially for the CVN model which has a simplified overland flow transfer. The river bed roughness also influences the peak intensity and time. Soil spatial representation is shown to have a significant role on runoff coefficients and on the spatial variability of saturation dynamics. Simulated soil saturation is found to be strongly related with soil depth and initial storage deficit maps, due to a full saturation of most of the area at the end of the event. When activated, the signature of subsurface lateral flow is also visible in the spatial patterns of soil saturation with higher values concentrating along the river network. However, the data currently available do not allow the assessment of both patterns. The paper concludes with a set of recommendations for enhancing field observations in order to progress in process understanding and gather a larger set of data to improve the realism of distributed models.

A physically based analytical model of flood frequency curves

NASA Astrophysics Data System (ADS)

Basso, S.; Schirmer, M.; Botter, G.

2016-09-01

Predicting magnitude and frequency of floods is a key issue in hydrology, with implications in many fields ranging from river science and geomorphology to the insurance industry. In this paper, a novel physically based approach is proposed to estimate the recurrence intervals of seasonal flow maxima. The method links the extremal distribution of streamflows to the stochastic dynamics of daily discharge, providing an analytical expression of the seasonal flood frequency curve. The parameters involved in the formulation embody climate and landscape attributes of the contributing catchment and can be estimated from daily rainfall and streamflow data. Only one parameter, which is linked to the antecedent wetness condition in the watershed, needs to be calibrated on the observed maxima. The performance of the method is discussed through a set of applications in four rivers featuring heterogeneous daily flow regimes. The model provides reliable estimates of seasonal maximum flows in different climatic settings and is able to capture diverse shapes of flood frequency curves emerging in erratic and persistent flow regimes. The proposed method exploits experimental information on the full range of discharges experienced by rivers. As a consequence, model performances do not deteriorate when the magnitude of events with return times longer than the available sample size is estimated. The approach provides a framework for the prediction of floods based on short data series of rainfall and daily streamflows that may be especially valuable in data scarce regions of the world.

A method of estimating in-stream residence time of water in rivers

NASA Astrophysics Data System (ADS)

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

2014-05-01

This study develops a method for estimating the average in-stream residence time of water in a river channel and across large catchments, i.e. the time between water entering a river and reaching a downstream monitoring point. The methodology uses river flow gauging data to integrate Manning's equation along a length of channel for different percentile flows. The method was developed and tested for the River Tees in northern England and then applied across the United Kingdom (UK). The study developed methods to predict channel width and main channel length from catchment area. For an 818 km2 catchment with a channel length of 79 km, the in-stream residence time at the 50% exceedence flow was 13.8 h. The method was applied to nine UK river basins and the results showed that in-stream residence time was related to the average slope of a basin and its average annual rainfall. For the UK as a whole, the discharge-weighted in-stream residence time was 26.7 h for the median flow. At median flow, 50% of the discharge-weighted in-stream residence time was due to only 6 out of the 323 catchments considered. Since only a few large rivers dominate the in-stream residence time, these rivers will dominate key biogeochemical processes controlling export at the national scale. The implications of the results for biogeochemistry, especially the turnover of carbon in rivers, are discussed.

Earth observation based assessment of the water production and water consumption of Nile Basin agro-ecosystems

USGS Publications Warehouse

Bastiaanssen, Wim G.M.; Karimi, Poolad; Rebelo, Lisa-Maria; Duan, Zheng; Senay, Gabriel; Muthuwatte, Lal; Smakhtin, Vladimir

2014-01-01

The increasing competition for water resources requires a better understanding of flows, fluxes, stocks, and the services and benefits related to water consumption. This paper explains how public domain Earth Observation data based on Moderate Resolution Imaging Spectroradiometer (MODIS), Second Generation Meteosat (MSG), Tropical Rainfall Measurement Mission (TRMM) and various altimeter measurements can be used to estimate net water production (rainfall (P) > evapotranspiration (ET)) and net water consumption (ET > P) of Nile Basin agro-ecosystems. Rainfall data from TRMM and the Famine Early Warning System Network (FEWS-NET) RainFall Estimates (RFE) products were used in conjunction with actual evapotranspiration from the Operational Simplified Surface Energy Balance (SSEBop) and ETLook models. Water flows laterally between net water production and net water consumption areas as a result of runoff and withdrawals. This lateral flow between the 15 sub-basins of the Nile was estimated, and partitioned into stream flow and non-stream flow using the discharge data. A series of essential water metrics necessary for successful integrated water management are explained and computed. Net water withdrawal estimates (natural and humanly instigated) were assumed to be the difference between net rainfall (Pnet) and actual evapotranspiration (ET) and some first estimates of withdrawals—without flow meters—are provided. Groundwater-dependent ecosystems withdraw large volumes of groundwater, which exceed water withdrawals for the irrigation sector. There is a strong need for the development of more open-access Earth Observation databases, especially for information related to actual ET. The fluxes, flows and storage changes presented form the basis for a global framework to describe monthly and annual water accounts in ungauged river basins.

Channel changes in the Jarama and Tagus rivers (central Spain) over the past 500 years

NASA Astrophysics Data System (ADS)

Uribelarrea, D.; Pérez-González, A.; Benito, G.

2003-10-01

Long-term channel changes of the Tagus and the Jarama Rivers in central Spain were studied in relation to variations in hydroclimatic factors, such as rainfall and flooding, and also with respect to human activities undertaken in their valleys. Data were taken from historical (1580-1823) and topographical (1877-1988) maps, as well as aerial photographs (1945-1999). The available hydroclimatic data consists of a series of monthly rainfall totals (1859-1994) and mean river flow values recorded at gauging stations (1911-1985). In addition, a historical flood record (1550-1947) was produced from documentary sources. Some of the data was incorporated into a geographical information system (GIS) to quantify the changes in the course of the rivers. The results show there have been two distinct periods: before and after human intervention in the river system, which took place around 1950. During the earlier period (1550-1950), a correlation exists between climate, frequency and magnitude of flooding and changes in fluvial geomorphology. Between 1860 and 1892 an increase in flood frequency and magnitude occurred, which produced half of the cut-offs recorded in the study area between 1823 and 1877. The meanders length ( L), width ( W) and radius of curvature (RC) of the Tagus River have decreased since 1750. However, those of the Jarama reached their maximum values during flood periods. Both rivers have different geomorphological responses during flood events, which can explain these different trends. Floods in the Jarama not only led to the cut-offs, but also enlarged the channel size ( L, W and RC). In the second period (1956—present), flow regulation via dams and gravel mining modified the system completely and impeded the natural development of these rivers.

Water allocation assessment in low flow river under data scarce conditions: a study of hydrological simulation in Mediterranean basin.

PubMed

Bangash, Rubab F; Passuello, Ana; Hammond, Michael; Schuhmacher, Marta

2012-12-01

River Francolí is a small river in Catalonia (northeastern Spain) with an average annual low flow (~2 m(3)/s). The purpose of the River Francolí watershed assessments is to support and inform region-wide planning efforts from the perspective of water protection, climate change and water allocation. In this study, a hydrological model of the Francolí River watershed was developed for use as a tool for watershed planning, water resource assessment, and ultimately, water allocation purposes using hydrological data from 2002 to 2006 inclusive. The modeling package selected for this application is DHI's MIKE BASIN. This model is a strategic scale water resource management simulation model, which includes modeling of both land surface and subsurface hydrological processes. Topographic, land use, hydrological, rainfall, and meteorological data were used to develop the model segmentation and input. Due to the unavailability of required catchment runoff data, the NAM rainfall-runoff model was used to calculate runoff of all the sub-watersheds. The results reveal a potential pressure on the availability of groundwater and surface water in the lower part of River Francolí as was expected by the IPCC for Mediterranean river basins. The study also revealed that due to the complex hydrological regime existing in the study area and data scarcity, a comprehensive physically based method was required to better represent the interaction between groundwater and surface water. The combined ArcGIS/MIKE BASIN models appear as a useful tool to assess the hydrological cycle and to better understand water allocation to different sectors in the Francolí River watershed. Copyright © 2012 Elsevier B.V. All rights reserved.

Simulating on water storage and pump capacity of "Kencing" river polder system in Kudus regency, Central Java, Indonesia

NASA Astrophysics Data System (ADS)

Wahyudi, Slamet Imam; Adi, Henny Pratiwi; Santoso, Esti; Heikoop, Rick

2017-03-01

Settlement in the Jati District, Kudus Regency, Central Java Province, Indonesia, is growing rapidly. Previous paddy fields area turns into new residential, industrial and office buildings. The rain water collected in small Kencing river that flows into big Wulan River. But the current condition, during high rain intensity Wulan river water elevation higher than the Kencing river, so that water can not flow gravity and the area inundated. To reduce the flooding, required polder drainage system by providing a long channel as water storage and pumping water into Wulan river. How to get optimal value of water storage volume, drainage system channels and the pump capacity? The result used to be efficient in the operation and maintenance of the polder system. The purpose of this study is to develop some scenarios water storage volume, water gate operation and to get the optimal value of operational pumps removing water from the Kencing River to Wulan River. Research Method is conducted by some steps. The first step, it is done field orientation in detail, then collecting secondary data including maps and rainfall data. The map is processed into Watershed or catchment area, while the rainfall data is processed into runoff discharge. Furthermore, the team collects primary data by measuring topography to determine the surface and volume of water storage. The analysis conducted to determine of flood discharge, water channel hydraulics, water storage volume and pump capacity corresponding. Based on the simulating of long water storage volume and pump capacity with some scenario trying, it can be determined optimum values. The results used to be guideline in to construction proses, operation and maintenance of the drainage polder system.

Using satellite-based rainfall estimates for streamflow modelling: Bagmati Basin

USGS Publications Warehouse

Shrestha, M.S.; Artan, Guleid A.; Bajracharya, S.R.; Sharma, R. R.

2008-01-01

In this study, we have described a hydrologic modelling system that uses satellite-based rainfall estimates and weather forecast data for the Bagmati River Basin of Nepal. The hydrologic model described is the US Geological Survey (USGS) Geospatial Stream Flow Model (GeoSFM). The GeoSFM is a spatially semidistributed, physically based hydrologic model. We have used the GeoSFM to estimate the streamflow of the Bagmati Basin at Pandhera Dovan hydrometric station. To determine the hydrologic connectivity, we have used the USGS Hydro1k DEM dataset. The model was forced by daily estimates of rainfall and evapotranspiration derived from weather model data. The rainfall estimates used for the modelling are those produced by the National Oceanic and Atmospheric Administration Climate Prediction Centre and observed at ground rain gauge stations. The model parameters were estimated from globally available soil and land cover datasets – the Digital Soil Map of the World by FAO and the USGS Global Land Cover dataset. The model predicted the daily streamflow at Pandhera Dovan gauging station. The comparison of the simulated and observed flows at Pandhera Dovan showed that the GeoSFM model performed well in simulating the flows of the Bagmati Basin.

Sediment transport patterns and climate change: the downstream Tuul River case study, Northern Mongolia.

NASA Astrophysics Data System (ADS)

Pietroń, Jan; Jarsjö, Jerker

2014-05-01

Ongoing changes in the Central Asian climate including increasing temperatures can influence the hydrological regimes of rivers and the waterborne transport of sediments. Changes in the latter, especially in combination with adverse human activities, may severely impact water quality and aquatic ecosystems. However, waterborne transport of sediments is a result of complex processes and varies considerably between, and even within, river systems. There is therefore a need to increase our general knowledge about sediment transport under changing climate conditions. The Tuul River, the case site of this study, is located in the upper part of the basin of the Selenga River that is the main tributary to Lake Baikal, a UNESCO World Heritage Site. Like many other rivers located in the steppes of Northern Mongolia, the Tuul River is characterized by a hydrological regime that is not disturbed by engineered structures such as reservoirs and dams. However, the water quality of the downstream Tuul River is increasingly affected by adverse human activities - including placer gold mining. The largest contribution to the annual river discharge occurs during the relatively warm period in May to August. Typically, there are numerous rainfall events during this period that cause considerable river flow peaks. Parallel work has furthermore shown that due to climate change, the daily variability of discharge and numbers of peak flow events in the Tuul River Basin has increased during the past 60 years. This trend is expected to continue. We here aim at increasing our understanding of future sediment transport patterns in the Tuul River, specifically considering the scenario that peak flow events may become more frequent due to climate change. We use a one-dimensional sediment transport model of the downstream reach of the river to simulate natural patterns of sediment transport for a recent hydrological year. In general, the results show that sediment transport varies considerably spatially and temporally. Peak flow events during the warm period contribute largely to the total annual transport of sediments and also to the erosion of stored bed material. These results suggest that if the number of peak flow events will increase further due to climate change, there will be a significant increase in the annual sediment load and consequently in the load of contaminants that are attached to the sediments, in particular downstream of mining sites. The present results are furthermore consistent with parallel studies on sediment transport and climate change showing that increased water discharges and frequencies of rainfall/flow events can lead to enhanced erosion processes. Furthermore, in addition to climate change effects, human activates can change sediment loads in rivers to even greater extent, as pointed out in several studies. Thus, several different challenges can be expected to face the management of Central Asian rivers such as Tuul and their ecosystems in the future.

Modeling multidecadal surface water inundation dynamics and key drivers on large river basin scale using multiple time series of Earth-observation and river flow data

NASA Astrophysics Data System (ADS)

Heimhuber, V.; Tulbure, M. G.; Broich, M.

2017-02-01

Periodically inundated floodplain areas are hot spots of biodiversity and provide a broad range of ecosystem services but have suffered alarming declines in recent history. Despite their importance, their long-term surface water (SW) dynamics and hydroclimatic drivers remain poorly quantified on continental scales. In this study, we used a 26 year time series of Landsat-derived SW maps in combination with river flow data from 68 gauges and spatial time series of rainfall, evapotranspiration and soil moisture to statistically model SW dynamics as a function of key drivers across Australia's Murray-Darling Basin (˜1 million km2). We fitted generalized additive models for 18,521 individual modeling units made up of 10 × 10 km grid cells, each split into floodplain, floodplain-lake, and nonfloodplain area. Average goodness of fit of models was high across floodplains and floodplain-lakes (r2 > 0.65), which were primarily driven by river flow, and was lower for nonfloodplain areas (r2 > 0.24), which were primarily driven by rainfall. Local climate conditions were more relevant for SW dynamics in the northern compared to the southern basin and had the highest influence in the least regulated and most extended floodplains. We further applied the models of two contrasting floodplain areas to predict SW extents of cloud-affected time steps in the Landsat series during the large 2010 floods with high validated accuracy (r2 > 0.97). Our framework is applicable to other complex river basins across the world and enables a more detailed quantification of large floods and drivers of SW dynamics compared to existing methods.

El Niño-southern oscillation influences on the Mahaweli streamflow in Sri Lanka

NASA Astrophysics Data System (ADS)

Zubair, Lareef

2003-01-01

Despite advances over the last two decades in the capacity to predict the evolution of the El Niño-southern oscillation (ENSO) phenomenon and advances in understanding of the relationship between ENSO and climate, there has been little use of climate predictions for water resources management in the tropics. As part of an effort to develop such a prediction scheme, the ENSO influences on streamflow and rainfall in the upper catchment of the Mahaweli river in Sri Lanka were investigated with correlation analysis, composite analysis and contingency tables. El Niño conditions were often associated with decreased annual flows and La Niña with increased flows. The relationship of streamflow and rainfall with the ENSO index of NINO3 contrasted between January to September and October to December. During El Niño episodes the streamflow declines from January to September, but from October to December there is no clear relationship. On the other hand, rainfall shows a clear increase from October to December and declines during January, February, March, July and August. The simultaneous correlations of NINO3 with the aggregate January to September streamflow (r = -0.50), with January to September rainfall (r = -0.44) and with October to December rainfall (r = 0.48) are all significant at the 99% level. The correlation between one-season-in-advance NINO3 with both January to September streamflow and October to December rainfall remained significant at the 99% level.This study demonstrates the potential of using ENSO-based predictors for a seasonal hydro-climatic prediction scheme in the Mahaweli basin. It shows the significant contrasts in ENSO influence on rainfall and streamflow due to various hydrological processes. It has demonstrated that the potential for prediction is improved by investigating ENSO influences for the appropriate season for the given river catchment.

A possible trade-off between clean air and clean water

USDA-ARS?s Scientific Manuscript database

Harmful algal blooms in Lake Erie have increased since 2002, coincidentally during this same period soluble reactive phosphorus loads have increased from rivers that flow into the lake. Also during this time, reductions in atmospheric sulfur emissions have resulted in marked increases in rainfall p...

Temporal and spatial changes of rainfall and streamflow in the Upper Tekezē-Atbara river basin, Ethiopia

NASA Astrophysics Data System (ADS)

Gebremicael, Tesfay G.; Mohamed, Yasir A.; Zaag, Pieter v.; Hagos, Eyasu Y.

2017-04-01

The Upper Tekezē-Atbara river sub-basin, part of the Nile Basin, is characterized by high temporal and spatial variability of rainfall and streamflow. In spite of its importance for sustainable water use and food security, the changing patterns of streamflow and its association with climate change is not well understood. This study aims to improve the understanding of the linkages between rainfall and streamflow trends and identify possible drivers of streamflow variabilities in the basin. Trend analyses and change-point detections of rainfall and streamflow were analysed using Mann-Kendall and Pettitt tests, respectively, using data records for 21 rainfall and 9 streamflow stations. The nature of changes and linkages between rainfall and streamflow were carefully examined for monthly, seasonal and annual flows, as well as indicators of hydrologic alteration (IHA). The trend and change-point analyses found that 19 of the tested 21 rainfall stations did not show statistically significant changes. In contrast, trend analyses on the streamflow showed both significant increasing and decreasing patterns. A decreasing trend in the dry season (October to February), short season (March to May), main rainy season (June to September) and annual totals is dominant in six out of the nine stations. Only one out of nine gauging stations experienced significant increasing flow in the dry and short rainy seasons, attributed to the construction of Tekezē hydropower dam upstream this station in 2009. Overall, streamflow trends and change-point timings were found to be inconsistent among the stations. Changes in streamflow without significant change in rainfall suggests factors other than rainfall drive the change. Most likely the observed changes in streamflow regimes could be due to changes in catchment characteristics of the basin. Further studies are needed to verify and quantify the hydrological changes shown in statistical tests by identifying the physical mechanisms behind those changes. The findings from this study are useful as a prerequisite for studying the effects of catchment management dynamics on the hydrological variabilities in the basin.

Earth Observations taken by Expedition 26 Crewmember

NASA Image and Video Library

2011-01-13

ISS026-E-017421 (13 Jan. 2011) --- Photographed by an Expedition 26 crew member on the International Space Station, this detailed photograph illustrates flooding in suburbs of the Brisbane, Australia metropolitan region. The Brisbane area experienced catastrophic flooding following unusually heavy rainfall on Jan. 10, 2011. With surficial soils already saturated from previous rainfall events, eastward-draining surface flow caused the Brisbane River to flood—inundating an estimated 20,000 homes in suburbs of the capital city of Queensland. Other cities in Queensland have also experienced damaging floods during previous heavy rainfall events this year. The image highlights several suburbs along the Brisbane River in the southern part of the Brisbane metropolitan area. The light-colored rooftops of residences and other structures contrast sharply with green vegetation and brown, sediment laden floodwaters. Most visible low-lying areas are inundated by floodwater, perhaps the most striking being Rocklea at upper left. The suburb of Yeronga (lower left) also has evident regions of flooding, as does a park and golf course located along a bend in the Brisbane River to the south of St. Lucia (center). Flooding becomes less apparent near the higher elevations of Mt. Coot-Tha at right.

Moving towards a new paradigm for global flood risk estimation

NASA Astrophysics Data System (ADS)

Troy, Tara J.; Devineni, Naresh; Lima, Carlos; Lall, Upmanu

2013-04-01

Traditional approaches to flood risk assessment are typically indexed to an instantaneous peak flow event at a specific recording gage on a river, and then extrapolated through hydraulic modeling of that peak flow to the potential area that is likely to be inundated. Recent research shows that property losses tend to be determined as much by the duration of flooding as by the depth and velocity of inundation. The existing notion of a flood return period based on just the instantaneous peak flow rate at a stream gauge consequently needs to be revisited, especially for floods due to persistent rainfall as seen recently in Thailand, Pakistan, the Ohio and the Mississippi Rivers, France, and Germany. Depending on the flood event type considered, different rainfall inducing mechanisms (tropical storm, local convection, frontal system, recurrent tropical waves) may be involved. Each of these will have a characteristic spatial scale, expression and orientation and temporal characteristics. We develop stochastic models that can reproduce these attributes with appropriate intensity-duration-frequency and spatial expression, and hence provide a basis for conditioning basin hydrologic attributes for flood risk assessment. Past work on Non-homogeneous Hidden Markov Models (NHMM) is used as a basis to develop this capability at regional scales. In addition, a dynamic hierarchical Bayesian network model that is continuous and not based on discretization to states is tested and compared against NHMM. The exogenous variables in these models comes from the analysis of key synoptic circulation patterns which will be used as predictors for the regional spatio-temporal models. The stochastic simulations of rainfall are then used as input to a flood modeling system, which consists of a series of physically based models. Rainfall-runoff generation is produced by the Variable Infiltration Capacity (VIC) model. When the modeled streamflow crosses a threshold, a full kinematic wave routing model is implemented at a finer resolution (<=1km) in order to more accurately model streamflow under flood conditions and estimate inundation. This approach allows for efficient computational simulation of the hydrology when not under potential for flooding with high-resolution flood wave modeling when there is flooding potential. We demonstrate the results of this flood risk estimation system for the Ohio River basin in the United States, a large river basin that is historically prone to flooding, with the intention of using it to do global flood risk assessment.

Monitoring stream sediment loads in response to agriculture in Prince Edward Island, Canada.

PubMed

Alberto, Ashley; St-Hilaire, Andre; Courtenay, Simon C; van den Heuvel, Michael R

2016-07-01

Increased agricultural land use leads to accelerated erosion and deposition of fine sediment in surface water. Monitoring of suspended sediment yields has proven challenging due to the spatial and temporal variability of sediment loading. Reliable sediment yield calculations depend on accurate monitoring of these highly episodic sediment loading events. This study aims to quantify precipitation-induced loading of suspended sediments on Prince Edward Island, Canada. Turbidity is considered to be a reasonably accurate proxy for suspended sediment data. In this study, turbidity was used to monitor suspended sediment concentration (SSC) and was measured for 2 years (December 2012-2014) in three subwatersheds with varying degrees of agricultural land use ranging from 10 to 69 %. Comparison of three turbidity meter calibration methods, two using suspended streambed sediment and one using automated sampling during rainfall events, revealed that the use of SSC samples constructed from streambed sediment was not an accurate replacement for water column sampling during rainfall events for calibration. Different particle size distributions in the three rivers produced significant impacts on the calibration methods demonstrating the need for river-specific calibration. Rainfall-induced sediment loading was significantly greater in the most agriculturally impacted site only when the load per rainfall event was corrected for runoff volume (total flow minus baseflow), flow increase intensity (the slope between the start of a runoff event and the peak of the hydrograph), and season. Monitoring turbidity, in combination with sediment modeling, may offer the best option for management purposes.

Informing a hydrological model of the Ogooué with multi-mission remote sensing data

NASA Astrophysics Data System (ADS)

Kittel, Cecile; Bauer-Gottwein, Peter; Nielsen, Karina; Tøttrup, Christian

2017-04-01

Knowledge on hydrological regimes of river basins is crucial for water management. However, data requirements often limit the applicability of hydrological models in basins with scarce in-situ data. Remote sensing provides a unique possibility to acquire information on hydrological variables in these basins. This study explores how multi-mission remote sensing data can inform a hydrological model. The Ogooué basin in Gabon is used as study area. No previous modelling efforts have been conducted for the basin and only historical flow and precipitation observations are available. Publicly available remote sensing observations are used to parametrize, force, calibrate and validate a hydrological model of the Ogooué. The modelling framework used in the study, is a lumped conceptual rainfall-runoff model based on the Budyko framework coupled to a Muskingum routing scheme. Precipitation is a crucial driver of the land-surface water balance, therefore two satellite-based rainfall estimates, Tropical Rainfall Measuring Mission (TRMM) product 3B42 version 7 and Famine Early Warning System - Rainfall Estimate (FEWS-RFE), are compared. The comparison shows good seasonal and spatial agreement between the products; however, TRMM consistently predicts significantly more precipitation: 1726 mm on average per year against 1556 mm for FEWS-RFE. Best modeling results are obtained with the TRMM precipitation forcing. Model calibration combines historical in-situ flow observations and GRACE total water storage observations using the Jet Propulsion Laboratory (JPL) mascon solution in a multi-objective approach. The two models are calibrated using flow duration curves and climatology benchmarks to overcome the lack of simultaneity between simulated and observed discharge. The objectives are aggregated into a global objective function, and the models are calibrated using the Shuffled Complex Evolution Algorithm. Water height observations from drifting orbit altimetry missions are extracted along the river line, using a detailed water mask based on Sentinel-1 SAR imagery. 1399 single CryoSat-2 altimetry observations and 48 ICESat observations are acquired. Additionally, water heights have been measured by the repeat-orbit satellite missions Envisat and Jason-2 at 12 virtual stations along the river. The four missions show generally good agreement in terms of mean annual water height amplitudes. The altimetry observations are used to validate the hydrological model of the Ogooué River. By combining hydrological modelling and remote sensing, new information on an otherwise unstudied basin is obtained. The study shows the potential of using remote sensing observations to parameterize, force, calibrate and validate models of poorly gauged river basins. Specifically, the study shows how Sentinel-1 SAR imagery supports the extraction of satellite altimetry data over rivers. The model can be used to assess climate change scenarios, evaluate hydraulic infrastructure development projects and predict the impact of irrigation diversions.

Simulation of Sediment Transport Caused by Landslide at Nanhua Reservoir Watershed in Southern Taiwan

NASA Astrophysics Data System (ADS)

Lee, Ming-Hsi; Huang, Cong-Gi; Lin, Huan-Hsuan

2016-04-01

As a result of heavy rainfall, steep topography, young and weak geological formations, earthquakes, loose soils, slope land cultivation and other human disturbance, much area in Taiwan are prone to the occurrence of disastrous mass movements such as landslides and sediment disasters. During recent years, the extreme rainfall events brought huge amounts of rainfall and triggered severe changes in watershed environments. Typhoon Morakot in August 2009 caused severe landslides, debris flow, flooding and sediment disasters induced by record-break rainfall. The maximum rainfall of mountain area in Chiayi, Tainan, Kaohsiung and Pingtung County were over 2,900 mm. The study area is located at Nanhua reservoir watershed in southern Taiwan. The numerical model (HEC-RAS 4.1 and FLO-2D) will be used to simulate the sediment transport caused by landslide and the study will find out the separating location of erosion and deposition in the river, the danger area of riverbank, and the safety of the river terrace village under the return period of 50-year, 100-year and 200-year (such as Typhoon Morakot). The results of this study can provide for the disaster risk management of administrative decisions to lessen the impacts of natural hazards and may also be useful for time-space variation of sediment disasters caused by Climate Change.

Water Induced Hazard Mapping in Nepal: A Case Study of East Rapti River Basin

NASA Astrophysics Data System (ADS)

Neupane, N.

2010-12-01

This paper presents illustration on typical water induced hazard mapping of East Rapti River Basin under the DWIDP, GON. The basin covers an area of 2398 sq km. The methodology includes making of base map of water induced disaster in the basin. Landslide hazard maps were prepared by SINMAP approach. Debris flow hazard maps were prepared by considering geology, slope, and saturation. Flood hazard maps were prepared by using two approaches: HEC-RAS and Satellite Imagery Interpretation. The composite water-induced hazard maps were produced by compiling the hazards rendered by landslide, debris flow, and flood. The monsoon average rainfall in the basin is 1907 mm whereas maximum 24 hours precipitation is 456.8 mm. The peak discharge of the Rapati River in the year of 1993 at station was 1220 cu m/sec. This discharge nearly corresponds to the discharge of 100-year return period. The landslides, floods, and debris flows triggered by the heavy rain of July 1993 claimed 265 lives, affected 148516 people, and damaged 1500 houses in the basin. The field investigation and integrated GIS interpretation showed that the very high and high landslide hazard zones collectively cover 38.38% and debris flow hazard zone constitutes 6.58%. High flood hazard zone occupies 4.28% area of the watershed. Mitigation measures are recommendated according to Integrated Watershed Management Approach under which the non-structural and structural measures are proposed. The non-structural measures includes: disaster management training, formulation of evacuation system (arrangement of information plan about disaster), agriculture management practices, protection of water sources, slope protections and removal of excessive bed load from the river channel. Similarly, structural measures such as dike, spur, rehabilitation of existing preventive measures and river training at some locations are recommendated. The major factors that have contributed to induce high incidences of various types of mass movements and inundation in the basin are rock and soil properties, prolonged and high-intensity rainfall, steep topography and various anthropogenic factors.

Conceptual modelling of E. coli in urban stormwater drains, creeks and rivers

NASA Astrophysics Data System (ADS)

Jovanovic, Dusan; Hathaway, Jon; Coleman, Rhys; Deletic, Ana; McCarthy, David T.

2017-12-01

Accurate estimation of faecal microorganism levels in water systems, such as stormwater drains, creeks and rivers, is needed for appropriate assessment of impacts on receiving water bodies and the risks to human health. The underlying hypothesis for this work is that a single conceptual model (the MicroOrganism Prediction in Urban Stormwater model - i.e. MOPUS) can adequately simulate microbial dynamics over a variety of water systems and wide range of scales; something which has not been previously tested. Additionally, the application of radar precipitation data for improvement of the model performance at these scales via more accurate areal averaged rainfall intensities was tested. Six comprehensive Escherichia coli (E. coli) datasets collected from five catchments in south-eastern Australia and one catchment in Raleigh, USA, were used to calibrate the model. The MOPUS rainfall-runoff model performed well at all scales (Nash-Sutcliffe E for instantaneous flow rates between 0.70 and 0.93). Sensitivity analysis showed that wet weather urban stormwater flows can be modelled with only three of the five rainfall runoff model parameters: routing coefficient (K), effective imperviousness (IMP) and time of concentration (TOC). The model's performance for representing instantaneous E. coli fluctuations ranged from 0.17 to 0.45 in catchments drained via pipe or open creek, and was the highest for a large riverine catchment (0.64); performing similarly, if not better, than other microbial models in literature. The model could also capture the variability in event mean concentrations (E = 0.17-0.57) and event loads (E = 0.32-0.97) at all scales. Application of weather radar-derived rainfall inputs caused lower overall performance compared to using gauged rainfall inputs in representing both flow and E. coli levels in urban drain catchments, with the performance improving with increasing catchment size and being comparable to the models that use gauged rainfall inputs at the large riverine catchment. These results demonstrate the potential of the MOPUS model and its ability to be applied to a wide range of catchment scales, including large riverine systems.

Estimation of potential runoff-contributing areas in the Kansas-Lower Republican River Basin, Kansas

USGS Publications Warehouse

Juracek, Kyle E.

1999-01-01

Digital soils and topographic data were used to estimate and compare potential runoff-contributing areas for 19 selected subbasins representing soil, slope, and runoff variability within the Kansas-Lower Republican (KLR) River Basin. Potential runoff-contributing areas were estimated separately and collectively for the processes of infiltration-excess and saturation-excess overland flow using a set of environmental conditions that represented high, moderate, and low potential runoff. For infiltration-excess overland flow, various rainfall intensities and soil permeabilities were used. For saturation-excess overland flow, antecedent soil-moisture conditions and a topographic wetness index were used. Results indicated that the subbasins with relatively high potential runoff are located in the central part of the KLR River Basin. These subbasins are Black Vermillion River, Clarks Creek, Delaware River upstream from Muscotah, Grasshopper Creek, Mill Creek (Wabaunsee County), Soldier Creek, Vermillion Creek (Pottawatomie County), and Wildcat Creek. The subbasins with relatively low potential runoff are located in the western one-third of the KLR River Basin, with one exception, and are Buffalo Creek, Little Blue River upstream from Barnes, Mill Creek (Washington County), Republican River between Concordia and Clay Center, Republican River upstream from Concordia, Wakarusa River downstream from Clinton Lake (exception), and White Rock Creek. The ability to distinguish the subbasins as having relatively high or low potential runoff was possible mostly due to the variability of soil permeability across the KLR River Basin.

Earth Observations taken by the Expedition 10 crew

NASA Image and Video Library

2005-04-07

ISS010-E-23451 (7 April 2005) --- Khartoum, Sudan is featured in this image photographed by an Expedition 10 crewmember on the International Space Station (ISS). Sudan’s capital city Khartoum, which means Elephant’s Trunk, describes the shape of the Nile River where the Blue and the White Nile Rivers meet to form the united Nile that flows northward into Egypt. This image shows the rivers near the end of the dry season. The White Nile (western branch) runs through Sudan from Uganda. The White Nile’s equatorial source produces a flow that runs at a nearly constant rate throughout the year. The nearly dry Blue Nile from the highlands of Ethiopia swells in the late summer and early fall with rains from the summer monsoons. The flow can be so great the Nile flows backward at the junction. In recent years, floods in Khartoum have occurred in August with heavy monsoon rainfall. Khartoum is one of the largest Muslim cities in North Africa, but has a fairly short history.

Macroscale water fluxes 3. Effects of land processes on variability of monthly river discharge

USGS Publications Warehouse

Milly, P.C.D.; Wetherald, R.T.

2002-01-01

A salient characteristic of river discharge is its temporal variability. The time series of flow at a point on a river can be viewed as the superposition of a smooth seasonal cycle and an irregular, random variation. Viewing the random component in the spectral domain facilitates both its characterization and an interpretation of its major physical controls from a global perspective. The power spectral density functions of monthly flow anomalies of many large rivers worldwide are typified by a "red noise" process: the density is higher at low frequencies (e.g., <1 y-1) than at high frequencies, indicating disproportionate (relative to uncorrelated "white noise") contribution of low frequencies to variability of monthly flow. For many high-latitude and arid-region rivers, however, the power is relatively evenly distributed across the frequency spectrum. The power spectrum of monthly flow can be interpreted as the product of the power spectrum of monthly basin total precipitation (which is typically white or slightly red) and several filters that have physical significance. The filters are associated with (1) the conversion of total precipitation (sum of rainfall and snowfall) to effective rainfall (liquid flux to the ground surface from above), (2) the conversion of effective rainfall to soil water excess (runoff), and (3) the conversion of soil water excess to river discharge. Inferences about the roles of each filter can be made through an analysis of observations, complemented by information from a global model of the ocean-atmosphere-land system. The first filter causes a snowmelt-related amplification of high-frequency variability in those basins that receive substantial snowfall. The second filter causes a relatively constant reduction in variability across all frequencies and can be predicted well by means of a semiempirical water balance relation. The third filter, associated with groundwater and surface water storage in the river basin, causes a strong reduction in high-frequency variability of many basins. The strength of this reduction can be quantified by an average residence time of water in storage, which is typically on the order of 20-50 days. The residence time is demonstrably influenced by freezing conditions in the basin, fractional cover of the basin by lakes, and runoff ratio (ratio of mean runoff to mean precipitation). Large lake areas enhance storage and can greatly increase total residence times (100 to several hundred days). Freezing conditions appear to cause bypassing of subsurface storage, thus reducing residence times (0-30 days). Small runoff ratios tend to be associated with arid regions, where the water table is deep, and consequently, most of the runoff is produced by processes that bypass the saturated zone, leading to relatively small residence times for such basins (0-40 days).

Predictive susceptibility analysis of typhoon induced landslides in Central Taiwan

NASA Astrophysics Data System (ADS)

Shou, Keh-Jian; Lin, Zora

2017-04-01

Climate change caused by global warming affects Taiwan significantly for the past decade. The increasing frequency of extreme rainfall events, in which concentrated and intensive rainfalls generally cause geohazards including landslides and debris flows. The extraordinary, such as 2004 Mindulle and 2009 Morakot, hit Taiwan and induced serious flooding and landslides. This study employs rainfall frequency analysis together with the atmospheric general circulation model (AGCM) downscaling estimation to understand the temporal rainfall trends, distributions, and intensities in the adopted Wu River watershed in Central Taiwan. To assess the spatial hazard of the landslides, landslide susceptibility analysis was also applied. Different types of rainfall factors were tested in the susceptibility models for a better accuracy. In addition, the routes of typhoons were also considered in the predictive analysis. The results of predictive analysis can be applied for risk prevention and management in the study area.

Processus et bilan des flux hydriques d'un bassin versant de milieu tropical de socle au Bénin (Donga, haut Ouémé)

NASA Astrophysics Data System (ADS)

Kamagaté, Bamory; Séguis, Luc; Favreau, Guillaume; Seidel, Jean-Luc; Descloitres, Marc; Affaton, Pascal

2007-05-01

Hydrodynamic, geochemical, and subsurface geophysical investigations, for two consecutive years with contrasting rainfall conditions, were used to characterize the hydrological processes occurring, and the water balance of a 586-km 2 watershed in Benin (Africa). The water table's monitoring shows that recharge occurs by direct infiltration of rainfall, and represents between 5 to 24% of the annual rainfall. Both surface water outflow, limited to the rainy season, and water chemistry indicate a weak groundwater contribution to river discharge. This implies that the calculated variations in annual runoff coefficients (of 14 and 28%) are mainly governed by surface and subsurface flows.

Environmental and hydrologic overview of the Yukon River basin, Alaska and Canada

USGS Publications Warehouse

Brabets, Timothy P.; Wang, Bronwen; Meade, Robert H.

2000-01-01

The Yukon River, located in northwestern Canada and central Alaska, drains an area of more than 330,000 square miles, making it the fourth largest drainage basin in North America. Approximately 126,000 people live in this basin and 10 percent of these people maintain a subsistence lifestyle, depending on the basin's fish and game resources. Twenty ecoregions compose the Yukon River Basin, which indicates the large diversity of natural features of the watershed, such as climate, soils, permafrost, and geology. Although the annual mean discharge of the Yukon River near its mouth is more than 200,000 cubic feet per second, most of the flow occurs in the summer months from snowmelt, rainfall, and glacial melt. Eight major rivers flow into the Yukon River. Two of these rivers, the Tanana River and the White River, are glacier-fed rivers and together account for 29 percent of the total water flow of the Yukon. Two others, the Porcupine River and the Koyukuk River, are underlain by continuous permafrost and drain larger areas than the Tanana and the White, but together contribute only 22 percent of the total water flow in the Yukon. At its mouth, the Yukon River transports about 60 million tons of suspended sediment annually into the Bering Sea. However, an estimated 20 million tons annually is deposited on flood plains and in braided reaches of the river. The waters of the main stem of the Yukon River and its tributaries are predominantly calcium magnesium bicarbonate waters with specific conductances generally less than 400 microsiemens per centimeter. Water quality of the Yukon River Basin varies temporally between summer and winter. Water quality also varies spatially among ecoregions

Coupling Radar Rainfall to Hydrological Models for Water Abstraction Management

NASA Astrophysics Data System (ADS)

Asfaw, Alemayehu; Shucksmith, James; Smith, Andrea; MacDonald, Ken

2015-04-01

The impacts of climate change and growing water use are likely to put considerable pressure on water resources and the environment. In the UK, a reform to surface water abstraction policy has recently been proposed which aims to increase the efficiency of using available water resources whilst minimising impacts on the aquatic environment. Key aspects to this reform include the consideration of dynamic rather than static abstraction licensing as well as introducing water trading concepts. Dynamic licensing will permit varying levels of abstraction dependent on environmental conditions (i.e. river flow and quality). The practical implementation of an effective dynamic abstraction strategy requires suitable flow forecasting techniques to inform abstraction asset management. Potentially the predicted availability of water resources within a catchment can be coupled to predicted demand and current storage to inform a cost effective water resource management strategy which minimises environmental impacts. The aim of this work is to use a historical analysis of UK case study catchment to compare potential water resource availability using modelled dynamic abstraction scenario informed by a flow forecasting model, against observed abstraction under a conventional abstraction regime. The work also demonstrates the impacts of modelling uncertainties on the accuracy of predicted water availability over range of forecast lead times. The study utilised a conceptual rainfall-runoff model PDM - Probability-Distributed Model developed by Centre for Ecology & Hydrology - set up in the Dove River catchment (UK) using 1km2 resolution radar rainfall as inputs and 15 min resolution gauged flow data for calibration and validation. Data assimilation procedures are implemented to improve flow predictions using observed flow data. Uncertainties in the radar rainfall data used in the model are quantified using artificial statistical error model described by Gaussian distribution and propagated through the model to assess its influence on the forecasted flow uncertainty. Furthermore, the effects of uncertainties at different forecast lead times on potential abstraction strategies are assessed. The results show that over a 10 year period, an average of approximately 70 ML/d of potential water is missed in the study catchment under a convention abstraction regime. This indicates a considerable potential for the use of flow forecasting models to effectively implement advanced abstraction management and more efficiently utilize available water resources in the study catchment.

A coupled synoptic-hydrological model for climate change impact assessment

NASA Astrophysics Data System (ADS)

Wilby, Robert; Greenfield, Brian; Glenny, Cathy

1994-01-01

A coupled atmospheric-hydrological model is presented. Sequences of daily rainfall occurrence for the 20 year period 1971-1990 at sites in the British Isles are related to the Lamb's Weather Types (LWT) by using conditional probabilities. Time series of circulation patterns and hence rainfall were then generated using a Markov representation of matrices of transition probabilities between weather types. The resultant precipitation data were used as input to a semidistributed catchment model to simulate daily flows. The combined model successfully reproduced aspects of the daily weather, precipitation and flow regimes. A range of synoptic scenarios were further investigated with particular reference to low flows in the River Coln, UK. The modelling approach represents a means of translating general circulation model (GCM) climate change predictions at the macro-scale into hydrological concerns at the catchment scale.

Earthshots: Satellite images of environmental change – Lake Turkana, Kenya and Ethiopia

USGS Publications Warehouse

,

2013-01-01

Ethiopia is constructing a series of dams on the Omo River. The Gibe I and Gibe II dams are completed, and the Gibe III dam began filling its reservoir in 2015. Studies are ongoing to understand the interactions between regulated flows as a result of the dams and rainfall on the water levels of Lake Turkana. Scientists use many years’ worth of data to get a better understanding of the lake’s natural variability and how that variability might be affected by dams, irrigation, and rainfall.

Calculating e-flow using UAV and ground monitoring

NASA Astrophysics Data System (ADS)

Zhao, C. S.; Zhang, C. B.; Yang, S. T.; Liu, C. M.; Xiang, H.; Sun, Y.; Yang, Z. Y.; Zhang, Y.; Yu, X. Y.; Shao, N. F.; Yu, Q.

2017-09-01

Intense human activity has led to serious degradation of basin water ecosystems and severe reduction in the river flow available for aquatic biota. As an important water ecosystem index, environmental flows (e-flows) are crucial for maintaining sustainability. However, most e-flow measurement methods involve long cycles, low efficiency, and transdisciplinary expertise. This makes it impossible to rapidly assess river e-flows at basin or larger scales. This study presents a new method to rapidly assessing e-flows coupling UAV and ground monitorings. UAV was firstly used to calculate river-course cross-sections with high-resolution stereoscopic images. A dominance index was then used to identify key fish species. Afterwards a habitat suitability index, along with biodiversity and integrity indices, was used to determine an appropriate flow velocity with full consideration of the fish spawning period. The cross-sections and flow velocity values were then combined into AEHRA, an e-flow assessment method for studying e-flows and supplying-rate. To verify the results from this new method, the widely used Tennant method was employed. The root-mean-square errors of river cross-sections determined by UAV are less than 0.25 m, which constitutes 3-5% water-depth of the river cross-sections. In the study area of Jinan city, the ecological flow velocity (VE) is equal to or greater than 0.11 m/s, and the ecological water depth (HE) is greater than 0.8 m. The river ecosystem is healthy with the minimum e-flow requirements being always met when it is close to large rivers, which is beneficial for the sustainable development of the water ecosystem. In the south river channel of Jinan, the upstream flow mostly meets the minimum e-flow requirements, and the downstream flow always meets the minimum e-flow requirements. The north of Jinan consists predominantly of artificial river channels used for irrigation. Rainfall rarely meets the minimum e-flow and irrigation water requirements. We suggest that the water shortage problem can be partly solved by diversion of the Yellow River. These results can provide useful information for ecological operations and restoration. The method used in this study for calculating e-flow based on a combination of UAV and ground monitoring can effectively promote research progress into basin e-flow, and provide an important reference for e-flow monitoring around the world.

Water resources of Ponape, Caroline Islands

USGS Publications Warehouse

Van der Brug, Otto

1984-01-01

Ponape is the third largest island in the western Pacific, with a land area of 129 square miles. The island is volcanic, nearly circular in shape, and covered with lush tropical vegetation. The mountainous interior has the highest peaks in the western Pacific. Annual rainfall at Kolonia and other coastal areas is 191 inches. Inland at higher elevations, the rainfall is considerably higher. The upper Nanpil River basin averages about 340 inches annually. Runoff-to-rainfall ratios for Ponapean streams show that about two thirds of the rain falling on the island runs off. Flow-duration curves show the similarity of the geology, vegetation, and rainfall of the drainage basins and indicate little ground-water contribution to surface runoff. Surface-water quality is excellent as shown by 53 chemical anlyses of water from 19 streams. Water of the Nanpil River, the source of water for the central water system, is especially low in dissolved elements and solids. This report summarizes in one volume all the hydrologic data collected and provides analyses that may be used by planning and public works officials as a basis for making decisions on the development and management of their water resources. (USGS)

Assessment of climate change impacts on meteorological and hydrological droughts in the Jucar River Basin

NASA Astrophysics Data System (ADS)

Marcos-Garcia, Patricia; Pulido-Velazquez, Manuel; Lopez-Nicolas, Antonio

2016-04-01

Extreme natural phenomena, and more specifically droughts, constitute a serious environmental, economic and social issue in Southern Mediterranean countries, common in the Mediterranean Spanish basins due to the high temporal and spatial rainfall variability. Drought events are characterized by their complexity, being often difficult to identify and quantify both in time and space, and an universally accepted definition does not even exist. This fact, along with future uncertainty about the duration and intensity of the phenomena on account of climate change, makes necessary increasing the knowledge about the impacts of climate change on droughts in order to design management plans and mitigation strategies. The present abstract aims to evaluate the impact of climate change on both meteorological and hydrological droughts, through the use of a generalization of the Standardized Precipitation Index (SPI). We use the Standardized Flow Index (SFI) to assess the hydrological drought, using flow time series instead of rainfall time series. In the case of the meteorological droughts, the Standardized Precipitation and Evapotranspiration Index (SPEI) has been applied to assess the variability of temperature impacts. In order to characterize climate change impacts on droughts, we have used projections from the CORDEX project (Coordinated Regional Climate Downscaling Experiment). Future rainfall and temperature time series for short (2011-2040) and medium terms (2041-2070) were obtained, applying a quantile mapping method to correct the bias of these time series. Regarding the hydrological drought, the Témez hydrological model has been applied to simulate the impacts of future temperature and rainfall time series on runoff and river discharges. It is a conceptual, lumped and a few parameters hydrological model. Nevertheless, it is necessary to point out the time difference between the meteorological and the hydrological droughts. The case study is the Jucar river basin (Spain), a highly regulated system with a share of 80% of water use for irrigated agriculture. The results show that the climate change would increase the historical drought impacts in the river basin. Acknowledgments The study has been supported by the IMPADAPT project (CGL2013-48424-C2-1-R) with Spanish MINECO (Ministerio de Economía y Competitividad) and European FEDER funds.

On the stationarity of Floods in west African rivers

NASA Astrophysics Data System (ADS)

NKA, B. N.; Oudin, L.; Karambiri, H.; Ribstein, P.; Paturel, J. E.

2014-12-01

West Africa undergoes a big change since the years 1970-1990, characterized by very low precipitation amounts, leading to low stream flows in river basins, except in the Sahelian region where the impact of human activities where pointed out to justify the substantial increase of floods in some catchments. More recently, studies showed an increase in the frequency of intense rainfall events, and according to observations made over the region, increase of flood events is also noticeable during the rainy season. Therefore, the assumption of stationarity on flood events is questionable and the reliability of flood evolution and climatic patterns is justified. In this work, we analyzed the trends of floods events for several catchments in the Sahelian and Sudanian regions of Burkina Faso. We used thirteen tributaries of large river basins (Niger, Nakambe, Mouhoun, Comoé) for which daily rainfall and flow data were collected from national hydrological and meteorological services of the country. We used Mann-Kendall and Pettitt tests to detect trends and break points in the annual time series of 8 rainfall indices and the annual maximum discharge records. We compare the trends of precipitation indices and flood size records to analyze the possible causality link between floods size and rainfall pattern. We also analyze the stationary of the frequency of flood exceeding the ten year return period level. The samples were extracted by a Peak over threshold method and the quantification of change in flood frequency was assessed by using a test developed by Lang M. (1995). The results exhibit two principal behaviors. Generally speaking, no trend is detected on catchments annual maximum discharge, but positive break points are pointed out in a group of three right bank tributaries of the Niger river that are located in the sahelian region between 300mm to 650mm. These same catchments show as well an increase of the yearly number of flood greater than the ten year flood since 1980. However, there is no consistency between rain fall pattern and flood size pattern in the entire region.

Special Flood Hazard Evaluation Report, Maumee River, Defiance and Paulding Counties, Ohio

DTIC Science & Technology

1988-01-01

into the Flood Flow Frequency Analysis (FFFA) computer program (Reference 3) to determine the discharge-frequency relationship for the Maumee River...although the flood may occur in any year. It is based on statistical analysis of streamflow records available for the watershed and analysis of rainfall...C) K) K4 10 ERFODBUDR .S ryEgne itit ufI N - FODA ONAYSEIA LO AADEAUTO 6 ? -F -C )I= ~ - %E )tvXJ. AE LO LVTO MAMERVE CROS SECIONLOCAION DEFINCEAND

Spatial and temporal variation of phytoplankton in a tropical eutrophic river.

PubMed

Santana, L M; Moraes, M E B; Silva, D M L; Ferragut, C

2016-04-19

This study aims to evaluate the environmental factors determining of the changes in phytoplankton structure in spatial (upper, middle and lower course) and seasonal (dry and rainy period) scales in a eutrophic river (Almada River, northeastern Brazil). In the study period, total accumulated rainfall was below of the historic average, resulting in flow reduction, mainly in rainy period. High orthophosphate concentration was found at the sampling sites. Phytoplankton chlorophyll a increased from upstream to downstream. Geitlerinema splendidum (S1) and Chlamydomonas sp. (X2) were the most abundant species in the upper course and several species of diatoms (D), Euglenophyceae (W1, W2) and Chlorophyceae (X1) in the middle and lower course. The functional groups were found to be characteristic of lotic ecosystem, shallow, with low light availability, rich in organic matter and eutrophic environments. We conclude that phytoplankton community structure was sensitive to change of the river flow and nutrient availability in spatial and seasonal scale in a tropical river.

Relations between rainfall–runoff-induced erosion and aeolian deposition at archaeological sites in a semi-arid dam-controlled river corridor

USGS Publications Warehouse

Collins, Brian D.; Bedford, David; Corbett, Skye C.; Fairley, Helen C.; Cronkite-Ratcliff, Collin

2016-01-01

Process dynamics in fluvial-based dryland environments are highly complex with fluvial, aeolian, and alluvial processes all contributing to landscape change. When anthropogenic activities such as dam-building affect fluvial processes, the complexity in local response can be further increased by flood- and sediment-limiting flows. Understanding these complexities is key to predicting landscape behavior in drylands and has important scientific and management implications, including for studies related to paleoclimatology, landscape ecology evolution, and archaeological site context and preservation. Here we use multi-temporal LiDAR surveys, local weather data, and geomorphological observations to identify trends in site change throughout the 446-km-long semi-arid Colorado River corridor in Grand Canyon, Arizona, USA, where archaeological site degradation related to the effects of upstream dam operation is a concern. Using several site case studies, we show the range of landscape responses that might be expected from concomitant occurrence of dam-controlled fluvial sand bar deposition, aeolian sand transport, and rainfall-induced erosion. Empirical rainfall-erosion threshold analyses coupled with a numerical rainfall–runoff–soil erosion model indicate that infiltration-excess overland flow and gullying govern large-scale (centimeter- to decimeter-scale) landscape changes, but that aeolian deposition can in some cases mitigate gully erosion. Whereas threshold analyses identify the normalized rainfall intensity (defined as the ratio of rainfall intensity to hydraulic conductivity) as the primary factor governing hydrologic-driven erosion, assessment of false positives and false negatives in the dataset highlight topographic slope as the next most important parameter governing site response. Analysis of 4+ years of high resolution (four-minute) weather data and 75+ years of low resolution (daily) climate records indicates that dryland erosion is dependent on short-term, storm-driven rainfall intensity rather than cumulative rainfall, and that erosion can occur outside of wet seasons and even wet years. These results can apply to other similar semi-arid landscapes where process complexity may not be fully understood.

Flood control problems

USGS Publications Warehouse

Leopold, Luna Bergere; Maddock, Thomas

1955-01-01

Throughout the world, alluvial soils are among the most fertile and easiest cultivated. Alluvial valleys are routes for transportation either by water or by road and railroad. Rivers are sources of water, a necessity of life. But these river valleys and alluvial deposits, which have so many desirable characteristics and which have increased so greatly in population, are periodically occupied by the river in performing its task of removing the excess of precipitation from the land area and carrying away the products of erosion.How a river behaves and how the river flood plain appears depend on the relationships between water and sediment combined with the existing topography. Thus rivers and their alluvial deposits provide an endless variety of forms which are shaped, to a large extent, by the river flow during periods of rapid removal of debris and of excessive rainfall. The mechanics of river formation are such, however, that the highest discharges are not contained within a limited channel. How much water a channel will carry depends upon the frequency of occurrence of a flow. Low flows, which occur very frequently, are not important in channel formation. Neither are the infrequent discharges of very great magnitude which, although powerful, do not occur often enough to shape the channel. Channel characteristics, are dependent on those discharges of moderate size which combine power with frequency of occurrence to modify the channel from. In the highest discharges of a stream, water rises above the confines of its banks and flows over the flood plain.It must be considered, therefore, that floods are natural phenomena which are characteristic of all rivers. They perform a vital function in the maintenance of river forms and out of bank flow may be expected with a reasonable degree of regularity.

Climate downscaling over South America for 1971-2000: application in SMAP rainfall-runoff model for Grande River Basin

NASA Astrophysics Data System (ADS)

da Silva, Felipe das Neves Roque; Alves, José Luis Drummond; Cataldi, Marcio

2018-03-01

This paper aims to validate inflow simulations concerning the present-day climate at Água Vermelha Hydroelectric Plant (AVHP—located on the Grande River Basin) based on the Soil Moisture Accounting Procedure (SMAP) hydrological model. In order to provide rainfall data to the SMAP model, the RegCM regional climate model was also used working with boundary conditions from the MIROC model. Initially, present-day climate simulation performed by RegCM model was analyzed. It was found that, in terms of rainfall, the model was able to simulate the main patterns observed over South America. A bias correction technique was also used and it was essential to reduce mistakes related to rainfall simulation. Comparison between rainfall simulations from RegCM and MIROC showed improvements when the dynamical downscaling was performed. Then, SMAP, a rainfall-runoff hydrological model, was used to simulate inflows at Água Vermelha Hydroelectric Plant. After calibration with observed rainfall, SMAP simulations were evaluated in two different periods from the one used in calibration. During calibration, SMAP captures the inflow variability observed at AVHP. During validation periods, the hydrological model obtained better results and statistics with observed rainfall. However, in spite of some discrepancies, the use of simulated rainfall without bias correction captured the interannual flow variability. However, the use of bias removal in the simulated rainfall performed by RegCM brought significant improvements to the simulation of natural inflows performed by SMAP. Not only the curve of simulated inflow became more similar to the observed inflow, but also the statistics improved their values. Improvements were also noticed in the inflow simulation when the rainfall was provided by the regional climate model compared to the global model. In general, results obtained so far prove that there was an added value in rainfall when regional climate model was compared to global climate model and that data from regional models must be bias-corrected so as to improve their results.

Natural and mining-related sources of dissolved minerals during low flow in the Upper Animas River Basin, southwestern Colorado

USGS Publications Warehouse

Wright, Winfield G.

1997-01-01

As part of the Clean Water Act of 1972 (Public Law 92-500), all States are required to establish water-quality standards for every river basin in the State. During 1994, the Colorado Department of Public Health and Environment proposed to the Colorado Water Quality Control Commission (CWQCC) an aquatic-life standard of 225 µg/L (micrograms per liter) for the dissolved-zinc concentration in the Animas River downstream from Silverton (fig.1). The CWQCC delayed implementation of this water-quality standard until further information was collected and a plan for the cleanup of abandoned mines was developed. Dissolved-zinc concentrations in this section of the river ranged from about 270 µg/L during high flow, when rainfall and snowmelt runoff dilute the dissolved minerals in the river (U.S. Geological Survey, 1996, p. 431), to 960 µg/L (Colorado Department of Public Health and Environment, written commun., 1996) during low flow (such as late summer and middle winter when natural springs and drainage from mines are the main sources for the streams). Mining sites in the basin were developed between about 1872 and the 1940's, with only a few mines operated until the early 1990's. For local governments, mining sites represent part of the Nation's heritage, tourists are attracted to the historic mining sites, and governments are obligated to protect the historic mining sites according to the National Historic Preservation Act (Public Law 89-665). In the context of this fact sheet, the term "natural sources of dissolved minerals" refers to springs and streams where no effect from mining were determined. "Mining-related sources of dissolved minerals" are assumed to be: (1 ) Water draining from mines , and (2) water seeping from mine-waste dump pile where the waste piles were saturated by water draining from mines. Although rainfall and snowmelt runoff from mine-waste piles might affect water quality in streams, work described in this fact sheet was done during low-flow conditions when springs and drainage from mine were the main sources of dissolved minerals affecting the streams. Data are being collected by the U.S. Geological Survey (USGS) to determine the magnitude and sources of dissolved minerals during rainfall- and snowmelt-runoff periods. This fact sheet presents results of studies done by the USGS in collaboration with the Animas River Stakeholders Group and was prepared in cooperation with the Southwestern Colorado Water Conservation District. The studies were done at selected sites in the Upper Animas River Basin to determine natural and mining-related sources of dissolved minerals and are continuing in the basin with the Animas River Stakeholders Group and as part of the Department of the Interior Abandoned Mine Lands Initiative. The results of these studies will provide useful information for determining water-quality standards in the basin.

Prediction of Flood Warning in Taiwan Using Nonlinear SVM with Simulated Annealing Algorithm

NASA Astrophysics Data System (ADS)

Lee, C.

2013-12-01

The issue of the floods is important in Taiwan. It is because the narrow and high topography of the island make lots of rivers steep in Taiwan. The tropical depression likes typhoon always causes rivers to flood. Prediction of river flow under the extreme rainfall circumstances is important for government to announce the warning of flood. Every time typhoon passed through Taiwan, there were always floods along some rivers. The warning is classified to three levels according to the warning water levels in Taiwan. The propose of this study is to predict the level of floods warning from the information of precipitation, rainfall duration and slope of riverbed. To classify the level of floods warning by the above-mentioned information and modeling the problems, a machine learning model, nonlinear Support vector machine (SVM), is formulated to classify the level of floods warning. In addition, simulated annealing (SA), a probabilistic heuristic algorithm, is used to determine the optimal parameter of the SVM model. A case study of flooding-trend rivers of different gradients in Taiwan is conducted. The contribution of this SVM model with simulated annealing is capable of making efficient announcement for flood warning and keeping the danger of flood from residents along the rivers.

A model-based assessment of the effects of projected climate change on the water resources of Jordan.

PubMed

Wade, A J; Black, E; Brayshaw, D J; El-Bastawesy, M; Holmes, P A C; Butterfield, D; Nuimat, S; Jamjoum, K

2010-11-28

This paper is concerned with the quantification of the likely effect of anthropogenic climate change on the water resources of Jordan by the end of the twenty-first century. Specifically, a suite of hydrological models are used in conjunction with modelled outcomes from a regional climate model, HadRM3, and a weather generator to determine how future flows in the upper River Jordan and in the Wadi Faynan may change. The results indicate that groundwater will play an important role in the water security of the country as irrigation demands increase. Given future projections of reduced winter rainfall and increased near-surface air temperatures, the already low groundwater recharge will decrease further. Interestingly, the modelled discharge at the Wadi Faynan indicates that extreme flood flows will increase in magnitude, despite a decrease in the mean annual rainfall. Simulations projected no increase in flood magnitude in the upper River Jordan. Discussion focuses on the utility of the modelling framework, the problems of making quantitative forecasts and the implications of reduced water availability in Jordan.

Quantity and sources of base flow in the San Pedro River near Tombstone, Arizona

USGS Publications Warehouse

Kennedy, Jeffrey R.; Gungle, Bruce

2010-01-01

Base flow in the upper San Pedro River at the gaging station (USGS station 09471550) near Tombstone, Arizona, is an important factor in the long-term sustainability of the river's riparian ecosystem. Most base flow occurs during the non-summer months (typically, from November to May), because evapotranspiration (ET) is greater than groundwater discharge to the riparian zone during the growing season and typically causes periods of zero flow in the spring and fall. Streamflow during the summer months occurs only as a result of rainfall and runoff. Using a hydrograph separation technique that partitions streamflow into stormflow and base flow, based on the change in runoff from the previous day, median base flow at the Tombstone gage from 1968 to 2009 (1987 to 1996 data absent) is 4,890 acre-ft/yr. Median base flow for the earlier period of record, 1968 to 1986, is 5,830 acre-ft/yr and for the later period, 1997 to 2009, is 2,880 acre-ft/yr. Base flow in the upper San Pedro River is derived from groundwater discharge to the river from the regional and alluvial aquifer. The regional aquifer is defined as having recharge zones away from the river, primarily at mountain fronts and along ephemeral channels. The alluvial aquifer is recharged mainly from stormflow. Based on environmental isotope data, the composition of base flow in the upper San Pedro River at the gaging station near Tombstone is 74 +/- 10 percent regional groundwater and 26 +/- 10 percent summer storm runoff stored as alluvial groundwater for the 2000 to 2009 period. The volume of base flow in a given year is well explained, using multiple regression, by mean daily flow during the previous October and by rainfall during the months of December and January (R2 = 0.9). This does not suggest that streamflow is composed only of these two sources; rather, these two sources control the degree of saturation of the near-stream alluvial aquifer and, therefore, the amount of winter base-flow infiltration that is possible upstream of the Tombstone gaging station. Because of losing conditions upstream of the Tombstone gage, there is no minimum amount of base flow that would be expected in any given year. The regression equation was used to adjust the measured base flow to account for year-to-year variation in precipitation. Adjusted base flows decreased, independent of climate, from the early period of record to the late period of record. In addition to total base flow, other metrics were considered, including the start and end dates of base flow, the number of days of base flow, the 25th percentile mean daily flow, and the number of days of zero flow. Each of these showed a decline in base flow between the early period of record and the late period. The available evidence to evaluate this decrease - hydraulic gradients in the alluvial and regional aquifers and a 10-yr record of streamflow environmental isotope samples - indicates that no reduction in groundwater discharge has occurred over this period of record. Continued regional groundwater pumping will, however, eventually lead to a decline in the contribution of regional groundwater to base flow.

The flash flood event in the catchment of the river Weisseritz (eastern Erzgebirge, Saxony) from 12.-14. August 2002 - meteorological and hydrological reasons, damage assesment and disaster managment

NASA Astrophysics Data System (ADS)

Goldberg, V.; Bernhofer, Ch.

2003-04-01

Between 12. and 14. August 2002 the region of eastern Erzgebirge (Saxony/Eastern Germany) was affected by the heaviest rainfall event recorded since beginning of the measuring period in 1883. The synoptic reason of this event was the advective precipitation due to the strong and very slowly shifting Vb-low "Ilse" combined with a noticeable topographic intensification by north-westerly winds. All stations in the catchment area of the river Weisseritz recorded new all-time records. E.g., at the meteorological station Zinnwald-Georgenfeld situated at the crest of eastern Erzgebirge a daily sum of 312 mm was measured for the 13. August. This value is close to the maximum physically possible rainfall. The intensive rainfall in the catchments of Rote Weisseritz and Wilde Weisseritz led to unexperienced heavy flash floods with large material transport and flow damages. The buffer effect of the existing dam systems was comparatively small because the reserved retaining capacity for flood protection was only about 20 percent of the total capacity. The reservoirs filled quickly due to the very high maximum inflow. So a long-time overflow of the dam system occurred with a maximum of about 300 cubic meters per second at the combined river Weisseritz through the cities of Freital and Dresden (This situation led, e.g., to the flooding of Central Railway Station in Dresden). This water flow is comparable with a medium flow rate of the river Elbe in Dresden, and it is about 300 times higher than the normal drain of the river Weisseritz in Freital! The material damages in the Weisseritz region account for several hundred millions EURO, and several causalties occurred. The damages of the University buildings in Tharandt (including one building of the Department of Meteorology) account for 15 millions EURO alone. The disaster management during the flood was not optimal. For many people, e.g. in Tharandt, there was neither an officially warning nor an organised rescue of movable goods. However, after the flood there was a fast help by the Federal Armed Forces, students and helpers from surrounding villages and municipalities. This flood, as well as the later flood of the Elbe, will be investigated by local and international competence teams to optimize future flood protection.

Integrated Modeling System for Analysis of Watershed Water Balance: A Case Study in the Tims Branch Watershed, South Carolina

NASA Astrophysics Data System (ADS)

Setegn, S. G.; Mahmoudi, M.; Lawrence, A.; Duque, N.

2015-12-01

The Applied Research Center at Florida International University (ARC-FIU) is supporting the soil and groundwater remediation efforts of the U.S. Department of Energy (DOE) Savannah River Site (SRS) by developing a surface water model to simulate the hydrology and the fate and transport of contaminants and sediment in the Tims Branch watershed. Hydrological models are useful tool in water and land resource development and decision-making for watershed management. Moreover, simulation of hydrological processes improves understanding of the environmental dynamics and helps to manage and protect water resources and the environment. MIKE SHE, an advanced integrated modeling system is used to simulate the hydrological processes of the Tim Branch watershed with the objective of developing an integrated modeling system to improve understanding of the physical, chemical and biological processes within the Tims Branch watershed. MIKE SHE simulates water flow in the entire land based phase of the hydrological cycle from rainfall to river flow, via various flow processes such as, overland flow, infiltration, evapotranspiration, and groundwater flow. In this study a MIKE SHE model is developed and applied to the Tim branch watershed to study the watershed response to storm events and understand the water balance of the watershed under different climatic and catchment characteristics. The preliminary result of the integrated model indicated that variation in the depth of overland flow highly depend on the amount and distribution of rainfall in the watershed. The ultimate goal of this project is to couple the MIKE SHE and MIKE 11 models to integrate the hydrological component in the land phase of hydrological cycle and stream flow process. The coupled MIKE SHE/MIKE 11 model will further be integrated with an Ecolab module to represent a range of water quality, contaminant transport, and ecological processes with respect to the stream, surface water and groundwater in the Tims Branch watershed at Savannah River Site.

Linking river nutrient concentrations to land use and rainfall in a paddy agriculture-urban area gradient watershed in southeast China.

PubMed

Xia, Yongqiu; Ti, Chaopu; She, Dongli; Yan, Xiaoyuan

2016-10-01

The effects of land use and land-use changes on river nutrient concentrations are not well understood, especially in the watersheds of developing countries that have a mixed land use of rice paddy fields and developing urban surfaces. Here, we present a three-year study of a paddy agricultural-urban area gradient watershed in southeast China. The annual anthropogenic nitrogen (N) input from the agricultural region to the urban region was high, yet the results showed that the monthly nutrient concentrations in the river were low in the rainy seasons. The nutrient concentrations decreased continuously as the river water passed through the traditional agriculture region (TAR; paddy rice and wheat rotation) and increased substantially in the city region (CR). The traditional agricultural reference region exported most of the nutrient loads at high flows (>1mmd(-1)), the intensified agricultural region (IAR, aquaculture and poultry farming) exported most of the nutrient loads at moderate flows (between 0.5 and 1mmd(-1)), and the CR reference area exported most of the nutrient loads under low to moderate flows. We developed a statistical model to link variations in the nutrient concentrations to the proportion of land-use types and rainfall. The statistical results showed that impervious surfaces, which we interpret as a proxy for urban activities including sewage disposal, were the most important drivers of nutrient concentrations, whereas water surfaces accounted for a substantial proportion of the nutrient sinks. Therefore, to efficiently reduce water pollution, sewage from urban areas must be addressed as a priority, although wetland restoration could also achieve substantial pollutant removal. Copyright © 2016. Published by Elsevier B.V.

Characteristics of radiocesium runoff between five river basins near to the Fukushima Daiichi Nuclear Power Plant over heavy rainfall events

NASA Astrophysics Data System (ADS)

Sakuma, Kazuyuki; Malins, Alex; Kurikami, Hiroshi; Kitamura, Akihiro

2017-04-01

Due to the Fukushima Daiichi Nuclear Power Plant accident triggered by the earthquake and subsequent tsunami on 11 March 2011, many radionuclides were released into environments such as forests, rivers, dam reservoirs, and the ocean. 137Cs is one of the most important radio-contaminants. In order to investigate 137Cs transport and discharge from contaminated basins, in this study we developed a three dimensional model of five river basins near to the Fukushima Daiichi Nuclear Power Plant. We applied the General-purpose Terrestrial fluid-Flow Simulator (GETFLOWS) watershed code to the Odaka, Ukedo, Maeda, Kuma, and Tomioka River basins. The main land uses in these areas are forests, rice paddy fields, crop fields and urban. The Ukedo, Kuma and Tomioka Rivers have relatively large dam reservoirs (>106 m3) in the upper basins. The radiocesium distribution was initiated based on the Second Airborne Monitoring Survey. The simulation periods were 2011 Typhoon Roke, nine heavy rainfall events in 2013, Typhoons Man-yi and Wipha, and tropical storm Etau in 2015. Water, sediment, and radiocesium discharge from the basins was calculated for these events. The characteristics of 137Cs runoff between the different basins were evaluated in terms of land use, the effect of dam reservoirs, geology, and the fraction of the initial radiocesium inventory discharged. The absolute 137Cs discharge from the Ukedo River basin was highest, however the 137Cs discharge ratio was lowest due to the Ogaki Dam and the inventory being mainly concentrated in upstream forests. The results for the water, suspended sediment and radiocesium discharge as a function of total precipitation over the various rainfall events can be used to predict discharges for other typhoons.

Fluvial signatures of modern and paleo orographic rainfall gradients

NASA Astrophysics Data System (ADS)

Schildgen, Taylor; Strecker, Manfred

2016-04-01

The morphology of river profiles is intimately linked to both climate and tectonic forcing. While much interest recently has focused on how river profiles can be inverted to derive uplift histories, here we show how in regions of strong orographic rainfall gradients, rivers may primarily record spatial patterns of precipitation. As a case study, we examine the eastern margin of the Andean plateau in NW Argentina, where the outward (eastward) growth of a broken foreland has led to a eastward shift in the main orographic rainfall gradient over the last several million years. Rivers influenced by the modern rainfall gradient are characterized by normalized river steepness values in tributary valleys that closely track spatial variations in rainfall, with higher steepness values in drier areas and lower steepness values in wetter areas. The same river steepness pattern has been predicted in landscape evolution models that apply a spatial gradient in rainfall to a region of uniform erosivity and uplift rate (e.g., Han et al., 2015). Also, chi plots from river networks on individual ranges affected by the modern orographic rainfall reveal patterns consistent with assymmetric precipitation across the range: the largest channels on the windward slopes are characterized by capture, while the longest channels on the leeward slopes are dominated by beheadings. Because basins on the windward side both lengthen and widen, tributary channels in the lengthening basins are characterized by capture, while tributary channels from neighboring basins on the windward side are dominated by beheadings. These patterns from the rivers influenced by the modern orographic rainfall gradient provide a guide for identifying river morphometric signatures of paleo orographic rainfall gradients. Mountain ranges to the west of the modern orographic rainfall have been interpreted to mark the location of orographic rainfall in the past, but these ranges are now in spatially near-uniform semi-arid to arid precipitation regimes. Indeed, despite uniform lithology and uplift history, we see patterns in river steepness values and in chi plots that are consistest a rainfall gradient on the (former) windward side of the range and asymmetric precipitation across the range. We suggest that morphological aspects of the river networks in such regions are dominated by their history of changing climate. These morphologic signatures appear to persist for millions of years in NW Argentina, most likely because the transition from a wetter to a drier climate has prevented a rapid readjustment to new forcing conditions. Reference: Han, J., Gasparini, N.M., and Johnson, J.P., 2015, Measuring the imprint of orographic rainfall gradients on the morphology of steady-state numerical fluvial landscapes. Earth Surf. Process. Landforms, 40(10), 1334-1350.

Hourly Water Quality Dynamics in Rivers Downstream of Urban Areas: Quantifying Seasonal Variation and Modelling Impacts of Urban Growth

NASA Astrophysics Data System (ADS)

Hutchins, M.; McGrane, S. J.; Miller, J. D.; Hitt, O.; Bowes, M.

2016-12-01

Continuous monitoring of water flows and quality is invaluable in improving understanding of the influence of urban areas on river health. When used to inform predictive modelling, insights can be gained as to how urban growth may affect the chemical and biological quality of rivers as they flow downstream into larger waterbodies. Water flow and quality monitoring in two urbanising sub-catchments (<100 km2) of the River Thames (southern UK) is described. Temperature, conductivity, turbidity, dissolved oxygen (DO) and ammonium (NH4) were measured at downstream locations where long term flow records are available, but particular focus is given to monitoring of an extended set of sites during prolonged winter rainfall. In the Ray sub-catchment streams were monitored in which urban cover varied across a range of 7-78%. A rural-urban gradient in DO was apparent in the low flow period prior to the storms. Transient low DO (< 8 mg L-1) as a response to pollutant first flushes was particularly apparent in urban streams but this was followed by a rapid recovery. Chronic effects lasting for three to four weeks were only seen downstream of a sewage treatment works (STW). In this respect temperature- and respiration-driven DO sags in summer were at least if not more severe than those driven by the winter storms. Likewise, although winter storm NH4 concentrations violated EU legislation downstream of the STW, they were lower than summer concentrations in pollutant flushes following dry spells. In contrast the predominant phenomenon affecting water quality in the Cut during the storms was dilution. Here, a river water quality model was calibrated and applied over the course of a year to capture the importance of periphyton photosynthesis and respiration cycles in determining water quality and to predict the influence of hypothetical urban growth on downstream river health. The periods monitored intensively, dry spells followed by prolonged rainfall, represent: (i) marked changes in conditions likely to become more prevalent in future, (ii) situations under which water quality in urban areas is likely to be particularly vulnerable, being influenced for example by first flush effects followed by capacity exceedance at STW. Despite this, whilst being somewhat long lasting in places, impacts on DO were not severe.

Sediment budget analysis from Landslide debris and river channel change during the extreme event - example of Typhoon Morakot at Laonong river, Taiwan

NASA Astrophysics Data System (ADS)

Chang, Kuo-Jen; Huang, Yu-Ting; Huang, Mei-Jen; Chiang, Yi-Lin; Yeh, En-Chao; Chao, Yu-Jui

2014-05-01

Taiwan, due to the high seismicity and high annual rainfall, numerous landslides triggered every year and severe impacts affect the island. Typhoon Morakot brought extreme and long-time rainfall for Taiwan in August 2009. It further caused huge loss of life and property in central and southern Taiwan. Laonong River is the largest tributary of Gaoping River. It's length is 137 km, and the basin area is 1373 km2. More than 2000mm rainfall brought and maximum rainfall exceeded 100mm/hr in the region by Typhoon Morakot in Aug, 2009. Its heavy rains made many landslides and debris flew into the river and further brought out accumulation and erosion on river banks of different areas. It caused severe disasters within the Laonong River drainage. In the past, the study of sediment blockage of river channel usually relies on field investigation, but due to inconvenient transportation, topographical barriers, or located in remote areas, etc. the survey is hardly to be completed sometimes. In recent years, the rapid development of remote sensing technology improves image resolution and quality significantly. Remote sensing technology can provide a wide range of image data, and provide essential and precious information. Furthermore, although the amount of sediment transportation can be estimated by using data such as rainfall, river flux, and suspended loads, the situation of large debris migration cannot be studied via those data. However, landslides, debris flow and river sediment transportation model in catchment area can be evaluated easily through analyzing the digital terrain model (DTM) . The purpose of this study is to investigate the phenomenon of river migration and to evaluate the amount of migration along Laonong River by analyzing the DEM before and after the typhoon Morakot. The DEMs are built by using the aerial images taken by digital mapping camera (DMC) and by airborne digital scanner 40 (ADS 40) before and after typhoon event. The results show that lateral erosion of the Laonong River caused by the typhoon seriously, especially in Yushan National Park, and midstream region. However, lateral erosion in downstream region is not so obvious. Meanwhile the siltation depth resulted from the Typhoon Morakot is larger in upstream region than in midstream and downstream regions. The amount of landslide debris created by Typhoon Morakot was too excessive to be transported. Materials just siltated in the upstream in place, same as in the middle stream area. Because of the amount of river slope erosion and sediment collapse in the downstream region is less than in upstream and midstream region, the amount of river erosion slightly larger than the amount of river siltation. The goals of this project are trying to decipher the sliding process and morphologic changes of large landslide areas, sediment transport and budgets, and to investigate the phenomenon of river migration. The results of this study provides not only geomatics and GIS dataset of the hazards, but also for essential geomorphologic information for other study, and for hazard mitigation and planning, as well.

Numerical representation of rainfall field in the Yarmouk River Basin

NASA Astrophysics Data System (ADS)

Shentsis, Isabella; Inbar, Nimrod; Magri, Fabien; Rosenthal, Eliyahu

2017-04-01

Rainfall is the decisive factors in evaluating the water balance of river basins and aquifers. Accepted methods rely on interpolation and extrapolation of gauged rain to regular grid with high dependence on the density and regularity of network, considering the relief complexity. We propose an alternative method that makes up to those restrictions by taking into account additional physical features of the rain field. The method applies to areas with (i) complex plain- and mountainous topography, which means inhomogeneity of the rainfall field and (ii) non-uniform distribution of a rain gauge network with partial lack of observations. The rain model is implemented in two steps: 1. Study of the rainfall field, based on the climatic data (mean annual precipitation), its description by the function of elevation and other factors, and estimation of model parameters (normalized coefficients of the Taylor series); 2. Estimation of rainfall in each historical year using the available data (less complete and irregular versus climatic data) as well as the a-priori known parameters (by the basic hypothesis on inter-annual stability of the model parameters). The proposed method was developed by Shentsis (1990) for hydrological forecasting in Central Asia and was later adapted to the Lake Kinneret Basin. Here this model (the first step) is applied to the Yarmouk River Basin. The Yarmouk River is the largest tributary of the Jordan River. Its transboundary basin (6,833 sq. km) extends over Syria (5,257 sq.km), Jordan (1,379 sq. km) and Israel (197 sq. km). Altitude varies from 1800 m (and more) to -235 m asl. The total number of rain stations in use is 36 (17 in Syria, 19 in Jordan). There is evidently lack and non-uniform distribution of a rain gauge network in Syria. The Yarmouk Basin was divided into five regions considering typical relationship between mean annual rain and elevation for each region. Generally, the borders of regions correspond to the common topographic, geomorphologic and climatic division of the basin. Difference between regional curves is comparable with amplitude of rainfall variance within the regions. In general, rainfall increases with altitude and decreases from west to east (south-east). It should be emphasized that (i) Lake Kinneret Basin (2,490 sq. km) was earlier divided into seven "orographic regions" and (ii) the Lake Kinneret Basin and the Yarmouk River Basin are presented by the system of regional curves X = f (Z) as one whole rainfall field in the Upper Jordan River Basin, where the mean annual rain (X) increases with altitude (Z) and decreases from west to east and from north to south. In the Yarmouk Basin there is much less rainfall (344 mm) than in the Lake Kinneret Basin (749 mm), wherein mean annual rain (2,352 MCM versus 1,865 MCM) is shared between Syria, Jordan and Israel as 80%, 15% and 5%, respectively. The provided rainfall data allow more precise estimations of surface water balances and of recharge to the regional aquifers in the Upper Jordan River Basin. The derived rates serve as fundamental input data for numerical modeling of groundwater flow. This method can be applied to other areas at different temporal and spatial scales. The general applicability makes it a very useful tool in several hydrological problems connected with assessment, management and policy-making of water resources, as well as their changes due to climate and anthropogenic factors. Reference: I. Shentsis (1990). Mathematical models for long-term prediction of mountainous river runoff: methods, information and results, Hydrological Sciences Journal, 35:5, 487-500, DOI: 10.1080/02626669009492453

Hydrological and hydrochemical impact studies in the urbanised Petrusse river basin (Luxembourg)

NASA Astrophysics Data System (ADS)

Pfister, L.; Iffly, J.; Guignard, C.; Krein, A.; Matgen, P.; Salvia-Castellvi, M.; van den Bos, R.; Tailliez, C.; Barnich, F.; Hofmmann, L.

2009-04-01

On the basis of ancient topographical maps, the growing urbanisation of the Petrusse river basin (42.9 km2) has been documented on 50-year time steps since 1770. While until the 1950's urban areas remained below 10% of total basin area, they are now close to 50%. This rapid change has consisted mainly in a change from cropland into built areas. As a direct consequence of these considerable changes in landuse, the basin presumably has undergone significant modifications of both its hydrological regime and the quality of the flowing surface waters. In the framework of a national monitoring programme, the Petrusse basin has been progressively equipped with 3 recording streamgauges between 1999 and 2003. Several meteorological stations are located in the immediate vicinity of the basin. The hydrological regime revealed by the 15-minute recordings of the streamgauges is very specific to heavily urbanised basins, i.e. characterised by quick reactions to incoming rainfall, as well as very limited contributions from sub-surface and groundwater reservoirs. A conceptual hydrological model has been used to evaluate roughly the impact of the progressive urbanisation of the Petrusse basin since 1770 on the rainfall-runoff relationship. Major changes were found for summer months, with significantly higher peak discharges and increasingly rapid reactions to rainfall events. However, the limitations of the spatial density of rainfall recordings (only 1 rainfall measurement site available between 1854 - 1949) cause severe shortcomings in the accuracy of the incoming rainfall estimations, especially in the case of convective rainfall events. This in turn also considerably reduces the accuracy of the historical rainfall-runoff simulations. Between 2002 and 2004, several monitoring campaigns have been carried out in the Petrusse basin in order to determine the impact of sewer system contributions from the urbanised areas to the water quality within the Petrusse. The investigations have shown a very strong so-called first-flush effect. During dry sequences, numerous deposits on roads and roofs (heavy metals, oils, etc.) accumulate, before being washed away during the first minutes of rainfall events and being ultimately being transported to the Petrusse river via the sewer systems, causing considerable pollution peaks. Current investigations target a reduction of this pollution. The involved volumes of polluted water are of such extent, that they cannot be dealt with by conventional waste water treatment systems. The currently existing rainfall measurement network around the city of Luxembourg has a spatial resolution that is still too low to capture accurately convective rainfall events. A new rainfall measurement approach will soon be tested to estimate spatio-temporal rainfall dynamics with a high resolution above the city of Luxembourg. Based on a combination of conventional raingauges, weather radar and microwave measurements (via cell-phone networks) this approach is supposed to provide data that might ultimately contribute to a real-time management of the first flush pollutions in the Petrusse river basin.

Visualization of conduit-matrix conductivity differences in a karst aquifer using time-lapse electrical resistivity

NASA Astrophysics Data System (ADS)

Meyerhoff, Steven B.; Karaoulis, Marios; Fiebig, Florian; Maxwell, Reed M.; Revil, André; Martin, Jonathan B.; Graham, Wendy D.

2012-12-01

In the karstic upper Floridan aquifer, surface water flows into conduits of the groundwater system and may exchange with water in the aquifer matrix. This exchange has been hypothesized to occur based on differences in discharge at the Santa Fe River Sink-Rise system, north central Florida, but has yet to be visualized using any geophysical techniques. Using electrical resistivity tomography, we conducted a time-lapse study at two locations with mapped conduits connecting the Santa Fe River Sink to the Santa Fe River Rise to study changes of electrical conductivity during times of varying discharge over a six-week period. Our results show conductivity differences between matrix, conduit changes in resistivity occurring through time at the locations of mapped karst conduits, and changes in electrical conductivity during rainfall infiltration. These observations provide insight into time scales and matrix conduit conductivity differences, illustrating how surface water flow recharged to conduits may flow in a groundwater system in a karst aquifer.

The Response of Sediments and Dissolved Organic Matter to Rapid Rainfall in the Santa Maria da Vitoria Watershed, Espírito Santo, BR

NASA Astrophysics Data System (ADS)

Ward, N. D.; Firme de Almeida, L.; Dias, G.; Gould, R.; Tan, A.; Bianchi, T. S.; Krusche, A. V.; Keil, R. G.; Richey, J. E.

2015-12-01

The Santa Maria da Vitória River supplies over 30% of the water for the greater Vitória, Espírito Santo, BR metropolitan area, which has a population of roughly 1.6 million people. The availability of clean freshwater is severely limited during periods of heavy rainfall because water sanitation facilities are "clogged" by high sediment discharge. The headwaters of the Santa Maria da Vitória River are characterized by relatively pristine forested environments, transitioning into primarily agricultural and rural land uses, and finally reaching the large urban center of Vitória near its marine receiving waters. The discharge of suspended sediments and dissolved organic matter (DOM) was examined at a 3 hour frequency during heavy storm flows from October 2013 to May 2015 in the Santa Maria da Vitória River main channel and a small tributary, the Mangaraí River. Bulk isotopic analyses were used to determine potential sediment sources and whether specific landscape/land use features were functionalized during periods of high runoff. Likewise, time of flight mass spectrometry (GC-ToF-MS) was used to identify a broad suite of DOM compounds that responded positively with river discharge in an effort to determine the influence of land use on the delivery of dissolved components to the river. For example, the abundance of compounds related to specific agricultural settings increased during storm flow along with anthropogenic DOM sources such as plasticizer and pesticide-derived compounds. Suspended sediment concentrations increased by as much as 70 times during peak river discharge relative to base flow several days earlier with similar increases in particulate organic carbon and nitrogen observed. Results from this study and previous field measurements were integrated into a coupled hydrology-sediment transport model, DHSVM, as part of a dynamic information framework with the goal of predicting water/sediment discharge to inform management and policy sectors of the state of Espírito Santo.

Hydrochemical evidence for mixing of river water and groundwater during high-flow conditions, lower Suwannee River basin, Florida, USA

USGS Publications Warehouse

Crandall, C.A.; Katz, B.G.; Hirten, J.J.

1999-01-01

Karstic aquifers are highly susceptible to rapid infiltration of river water, particularly during periods of high flow. Following a period of sustained rainfall in the Suwannee River basin, Florida, USA, the stage of the Suwannee River rose from 3.0 to 5.88 m above mean sea level in April 1996 and discharge peaked at 360 m3/s. During these high-flow conditions, water from the Suwannee River migrated directly into the karstic Upper Floridan aquifer, the main source of water supply for the area. Changes in the chemical composition of groundwater were quantified using naturally occurring geochemical tracers and mass-balance modeling techniques. Mixing of river water with groundwater was indicated by a decrease in the concentrations of calcium, silica, and 222Rn; and by an increase in dissolved organic carbon (DOC), tannic acid, and chloride, compared to low-flow conditions in water from a nearby monitoring well, Wingate Sink, and Little River Springs. The proportion (fraction) of river water in groundwater ranged from 0.13 to 0.65 at Wingate Sink and from 0.5 to 0.99 at well W-17258, based on binary mixing models using various tracers. The effectiveness of a natural tracer in quantifying mixing of river water and groundwater was related to differences in tracer concentration of the two end members and how conservatively the tracer reacted in the mixed water. Solutes with similar concentrations in the two end-member waters (Na, Mg, K, Cl, SO4, SiO2) were not as effective tracers for quantifying mixing of river water and groundwater as those with larger differences in end-member concentrations (Ca, tannic acid, DOC, 222Rn, HCO3). ?? Springer-Verlag.

Global Overview On Delivery Of Sediment To The Coast From Tropical River Basins

NASA Astrophysics Data System (ADS)

Syvitski, J. P.; Kettner, A. J.; Brakenridge, G. R.

2011-12-01

Depending on definition, the tropics occupy between 16% and 19% of the earth's land surface, and discharge ~18.5% of the earth's fluvial water runoff. These flow regimes are driven by three types of sub-regional climate: rainforest, monsoon, and savannah. Even though the tropics include extreme precipitation events, particularly for the SE Asian islands, the general rainfall pattern alternates between wet and dry seasons as the ITCZ follows the sun and where annual monsoonal rain occurs. ITCZ convective rainfall is the dominant style of precipitation but this can be influenced by rare intra-tropical cyclone events, and by atmospheric river events set up by strong monsoonal conditions. Though a rainy season is normal (for example, portions of India discharge in summer may reach 50 times that of winter), the actual rainfall events are in the form of short bursts of precipitation (hours to days) separated by periods of dry (hours to weeks). Some areas of the tropics receive more than 100 thunderstorms per year. Rivers respond to this punctuated weather by seasonal flooding. For the smaller island nations and locales (e.g. Indonesia, Philippines, Borneo, Hainan, PNG, Madagascar, Hawaii, Taiwan) flash floods are common. Larger tropical river systems (Niger, Ganges, Brahmaputra, Congo, Amazon, Orinoco, Magdalena) show typical seasonally modulated discharges. The sediment flux from tropical rivers is approximately 17% to 19% of the global total - however individual river basins offer a wide range in sediment yields reflecting highly variable differences in their hinterland lithology, tectonic activity and volcanism, land-sliding, and relief. Human influences also greatly influence the range for tropical river sediment yield. Some SE Asian Rivers continue to be greatly affected by deforestation, road construction, and monoculture plantations. Sediment flux is more than twice the pre-Anthropocene flux in many of these SE Asian countries, especially where dams and reservoir emplacements do not impact sediment delivery, as is the case in most temperate regions.

Instrumental lahar monitoring at Merapi Volcano, Central Java, Indonesia

USGS Publications Warehouse

Lavigne, Franck; Thouret, J.-C.; Voight, B.; Young, K.; LaHusen, R.; Marso, J.; Suwa, H.; Sumaryono, A.; Sayudi, D.S.; Dejean, M.

2000-01-01

More than 50 volcanic debris flows or lahars were generated around Mt Merapi during the first rainy season following the nuees ardentes of 22 November 1994. The rainfalls that triggered the lahars were analyzed, using such instruments as weather radar and telemetered rain gauges. Lahar dynamics were also monitored, using new non-contact detection instrumentation installed on the slopes of the volcano. These devices include real-time seismic amplitude measurement (RSAM), seismic spectral amplitude measurement (SSAM) and acoustic flow monitoring (AFM) systems. Calibration of the various systems was accomplished by field measurements of flow velocities and discharge, contemporaneously with instrumental monitoring. The 1994–1995 lahars were relatively short events, their duration in the Boyong river commonly ranging between 30 min and 1 h 30 min. The great majority (90%) of the lahars was recognized at Kaliurang village between 13:00 and 17:30 h, due to the predominance of afternoon rainfalls. The observed mean velocity of lahar fronts ranged between 1.1 and 3.4 m/s, whereas the peak velocity of the flows varied from 11 to 15 m/s, under the Gardu Pandang viewpoint location at Kaliurang, to 8–10 m/s at a section 500 m downstream from this site. River slopes vary from 28 to 22 m/km at the two sites. Peak discharges recorded in various events ranged from 33 to 360 m3/s, with the maximum value of peak discharge 360 m3/s, on 20 May 1995. To improve the lahar warning system along Boyong river, some instrumental thresholds were proposed: large and potentially hazardous lahars may be detected by RSAM units exceeding 400, SSAM units exceeding 80 on the highest frequency band, or AFM values greater than 1500 mV on the low-gain, broad-band setting.

Streamflow variation of forest covered catchments

NASA Astrophysics Data System (ADS)

Gribovszki, Z.; Kalicz, P.; Kucsara, M.

2003-04-01

Rainfall concentration and runoff, otherwise rainfall-runoff processes, which cause river water discharge fluctuation, is one of the basic questions of hydrology. Several social-economy demands have a strong connection with small or bigger rivers from the point of view both quantity and quality of the water. Gratification or consideration of these demands is complicated substantially that we have still poor knowledge about our stream-flow regime. Water resources mainly stem from upper watersheds. These upper watersheds are the basis of the water concentration process; therefore we have to improve our knowledge about hydrological processes coming up in these territories. In this article we present runoff regime of two small catchments on the basis of one year data. Both catchments have a similar magnitude 0.6 and 0.9 km^2. We have been analyzed in detail some hydrological elements: features of rainfall, discharge, rainfall induced flooding waves and basic discharge in rainless periods. Variances of these parameters have been analyzed in relation to catchments surface, vegetation coverage and forest management. Result data set well enforce our knowledge about small catchments hydrological processes. On the basis of these fundamentals we can plan more established the management of these lands (forest practices, civil engineering works, and usage of natural water resources).

Flood Hazard Mapping Assessment for El-Awali River Catchment-Lebanon

NASA Astrophysics Data System (ADS)

Hdeib, Rouya; Abdallah, Chadi; Moussa, Roger; Hijazi, Samar

2016-04-01

River flooding prediction and flood forecasting has become an essential stage in the major flood mitigation plans worldwide. Delineation of floodplains resulting from a river flooding event requires coupling between a Hydrological rainfall-runoff model to calculate the resulting outflows of the catchment and a hydraulic model to calculate the corresponding water surface profiles along the river main course. In this study several methods were applied to predict the flood discharge of El-Awali River using the available historical data and gauging records and by conducting several site visits. The HEC-HMS Rainfall-Runoff model was built and applied to calculate the flood hydrographs along several outlets on El-Awali River and calibrated using the storm that took place on January 2013 and caused flooding of the major Lebanese rivers and by conducting additional site visits to calculate proper river sections and record witnesses of the locals. The Hydraulic HEC-RAS model was then applied to calculate the corresponding water surface profiles along El-Awali River main reach. Floodplain delineation and Hazard mapping for 10,50 and 100 years return periods was performed using the Watershed Modeling System WMS. The results first show an underestimation of the flood discharge recorded by the operating gauge stations on El-Awali River, whereas, the discharge of the 100 years flood may reach up to 506 m3/s compared by lower values calculated using the traditional discharge estimation methods. Second any flooding of El-Awali River may be catastrophic especially to the coastal part of the catchment and can cause tragic losses in agricultural lands and properties. Last a major floodplain was noticed in Marj Bisri village this floodplain can reach more than 200 meters in width. Overall, performance was good and the Rainfall-Runoff model can provide valuable information about flows especially on ungauged points and can perform a great aid for the floodplain delineation and flood prediction methods in poorly gauged basins, but further model updates and calibration is always required to compensate the weaknesses in such model and attain better results.

Flood of May 26-27, 1984 in Tulsa, Oklahoma

USGS Publications Warehouse

Bergman, DeRoy L.; Tortorelli, Robert L.

1988-01-01

The greatest flood disaster in the history of Tulsa, Oklahoma occurred during 8 hours from 2030 hours May 26 to 0430 hours May 27, 1984, as a result of intense rainfall centered over the metropolitan area. Storms of the magnitude that caused this flood are not uncommon to the southern great plains. Such storms are seldom documented in large urban areas. Total rainfall depth and rainfall distribution in the Tulsa metropolitan area during the May 26-27 storm were recorded by 16 recording rain gages. This report presents location of recording rain gages with corresponding rainfall histograms and mass curves, lines of equal rainfall depth (map A), and flood magnitudes and inundated areas of selected streams within the city (map B). The limits of the study areas (fig. 1) are the corporate boundaries of Tulsa, an area of about 185 square miles. Streams draining the city are: Dirty Butter, Coal, and Mingo Creeks which drain northward into Bird Creek along the northern boundary of the city; and Cherry, Crow, Harlow, Joe Haikey, Fry, Vensel, Fred, and Mooser Creeks which flow into the Arkansas River along the southern part of the city. Flooding along Haikey, Fry, Fred, Vensel, and Mooser Creeks was not documented for this report. The Arkansas River is regulated by Keystone Dam upstream from Tulsa (fig. 1). The Arkansas River remained below flood stage during the storm. Flooded areas in Tulsa (map B) were delineated on the topographic maps using flood profiles based on surveys of high-water marks identified immediately after the flood. The flood boundaries show the limits of stream flooding. Additional areas flooded because of overfilled storm drains or by sheet runoff are not shown in this report. Data presented in this report, including rainfall duration and frequency, and flood discharges and elevations, provide city officials and consultants a technical basis for making flood-plain management decisions.

Analysis of rainfall distribution in Kelantan river basin, Malaysia

NASA Astrophysics Data System (ADS)

Che Ros, Faizah; Tosaka, Hiroyuki

2018-03-01

Using rainfall gauge on its own as input carries great uncertainties regarding runoff estimation, especially when the area is large and the rainfall is measured and recorded at irregular spaced gauging stations. Hence spatial interpolation is the key to obtain continuous and orderly rainfall distribution at unknown points to be the input to the rainfall runoff processes for distributed and semi-distributed numerical modelling. It is crucial to study and predict the behaviour of rainfall and river runoff to reduce flood damages of the affected area along the Kelantan river. Thus, a good knowledge on rainfall distribution is essential in early flood prediction studies. Forty six rainfall stations and their daily time-series were used to interpolate gridded rainfall surfaces using inverse-distance weighting (IDW), inverse-distance and elevation weighting (IDEW) methods and average rainfall distribution. Sensitivity analysis for distance and elevation parameters were conducted to see the variation produced. The accuracy of these interpolated datasets was examined using cross-validation assessment.

New insights on historic droughts in the UK: Analysis of 200 river flow reconstructions for 1890-2015

NASA Astrophysics Data System (ADS)

Parry, Simon; Barker, Lucy; Hannaford, Jamie; Prudhomme, Christel; Smith, Katie; Svensson, Cecilia; Tanguy, Maliko

2017-04-01

Hydrological droughts of the last 50 years in the UK have been well characterised owing to a relatively dense hydrometric network. Prior to this, observed river flow data were generally limited in their spatial coverage and often subject to considerable uncertainty. Whilst qualitative records indicate the occurrence of severe droughts in the late 19th and early 20th centuries, including scenarios which may cause substantial impacts to contemporary water supply systems, existing observations are not sufficient to describe their spatio-temporal characteristics. As such, insights on drought in the UK are constrained and a range of stakeholders including water companies and regulators would benefit from a more thorough assessment of historic drought characteristics and their variability. The multi-disciplinary Historic Droughts project aims to rigorously characterise droughts in the UK to inform improved drought management and communication. Driven by rainfall and potential evapotranspiration data that have been extended using recovered records, lumped catchment hydrological models are used to reconstruct daily river flows from 1890 to 2015 for more than 200 catchments across the UK. The reconstructions are derived within a state-of-the-art modelling framework which allows a comprehensive assessment of model, structure and parameter uncertainty. Standardised and threshold-based indicators are applied to the river flow reconstructions to identify and characterise hydrological drought events. The reconstructions are most beneficial in comprehensively describing well known but poorly quantified late 19th and early 20th century droughts, placing the spatial and temporal footprint of these often extreme events within the context of modern episodes for the first time. Oscillations between drought-rich and drought-poor periods are shown not to be limited to the recent observational past, providing an increased sample size of events against which to test a range of airflow and oceanic index patterns as potential drivers of streamflow drought. The quantification of changes over time in both the mean and the variability of drought frequency, duration, severity and termination benefits from the temporal extent of the river flow reconstructions, assessing the temporal variability of drought over more prolonged timescales than previous drought trend studies. When considered alongside complimentary reconstructions of rainfall and groundwater levels, the characteristics of propagation from meteorological to hydrological drought are analysed to an extent not previously possible. The unprecedented spatio-temporal coverage of the river flow reconstructions has yielded important new insights on historic droughts in the UK. It is hoped that this more robust assessment of the historical variability of hydrological drought in the UK will underpin enhanced drought planning and management.

Analysis of Compound Water Hazard in Coastal Urbanized Areas under the Future Climate

NASA Astrophysics Data System (ADS)

Shibuo, Y.; Taniguchi, K.; Sanuki, H.; Yoshimura, K.; Lee, S.; Tajima, Y.; Koike, T.; Furumai, H.; Sato, S.

2017-12-01

Several studies indicate the increased frequency and magnitude of heavy rainfalls as well as the sea level rise under the future climate, which implies that coastal low-lying urbanized areas may experience increased risk against flooding. In such areas, where river discharge, tidal fluctuation, and city drainage networks altogether influence urban inundation, it is necessary to consider their potential interference to understand the effect of compound water hazard. For instance, pump stations cannot pump out storm water when the river water level is high, and in the meantime the river water level shall increase when it receives pumped water from cities. At the further downstream, as the tidal fluctuation regulates the water levels in the river, it will also affect the functionality of pump stations and possible inundation from rivers. In this study, we estimate compound water hazard in the coastal low-lying urbanized areas of the Tsurumi river basin under the future climate. We developed the seamlessly integrated river, sewerage, and coastal hydraulic model that can simulate river water levels, water flow in sewerage network, and inundation from the rivers and/or the coast to address the potential interference issue. As a forcing, the pseudo global warming method, which applies the changes in GCM anomaly to re-analysis data, is employed to produce ensemble typhoons to drive the seamlessly integrated model. The results show that heavy rainfalls caused by the observed typhoon generally become stronger under the pseudo global climate condition. It also suggests that the coastal low-lying areas become extensively inundated if the onset of river flooding and storm surge coincides.

Feasibility of estimate sediment yield in the non-sediment monitoring station area - A case study of Alishan River watershed,Taiwan

NASA Astrophysics Data System (ADS)

Chang, ChiaChi; Chan, HsunChuan; Jia, YaFei; Zhang, YaoXin

2017-04-01

Due to the steep topography, frail geology and concentrated rainfall in wet season, slope disaster occurred frequently in Taiwan. In addition, heavy rainfall induced landslides in upper watersheds. The sediment yield on the slopeland affects the sediment transport in the river. Sediment deposits on the river bed reduce the river cross section and change the flow direction. Furthermore, it generates risks to residents' lives and property in the downstream. The Taiwanese government has been devoting increasing efforts on the sedimentary management issues and on reduction in disaster occurrence. However, due to the limited information on the environmental conditions in the upper stream, it is difficult to set up the sedimentary monitoring equipment. This study used the upper stream of the Qingshuei River, the Alishan River, as a study area. In August 2009, Typhoon Morakot caused the sedimentation of midstream and downstream river courses in the Alishan River. Because there is no any sediment monitoring stations within the Alishan River watershed, the sediment yield values are hard to determine. The objective of this study is to establish a method to analyze the event-landslide sediment transport in the river on the upper watershed. This study numerically investigated the sediment transport in the Alishan River by using the KINEROS 2 model developed by the United States Department of Agriculture and the CCHE1D model developed by the National Center for Computational Hydroscience and Engineering. The simulated results represent the morphology changes in the Alishan River during the typhoon events. The results consist of a critical strategy reference for the sedimentary management for the Alishan River watershed.

Hydrological Signature From River-Floodplain Interactions

NASA Astrophysics Data System (ADS)

Paiva, R. C. D.; Fleischmann, A. S.; Collischonn, W.; Sorribas, M.; Pontes, P. R.

2015-12-01

Understanding river-floodplain hydraulic processes is fundamental to promote comprehension of related water paths, biogeochemicalcyclesand ecosystems. Large river basins around the globe present enormous developed floodplains, which strongly affect flood waves and water dynamics. Since most of these river-floodplain interactions are not monitored, it is interesting to develop strategies to understand such processes through characteristic hydrological signatures, e.g. hydrographs. We studied observed hydrographs from large South American rivers and found that in several cases rivers with extensive wetlands present a particular hydrograph shape, with slower rising limb in relation to the receding one, due to storage effects and the associated decrease of wave celerity with stage. A negative asymmetry in the hydrograph is generated, which is higher when more water flows through floodplains upstream of the observed point. Finally, we studied the Amazon basin using gauged information and simulation results from the MGB-IPH regional hydrological model. Major rivers with larger wetland areas (e.g. Purus, Madeira and Juruá) were identified with higher negative asymmetry in their hydrographs. The hydrodynamic model was run in scenarios with and without floodplains, and results supported that floodplain storage affects hydrographs in creating a negative asymmetry, besides attenuating peaks, increasing hydrograph smoothness and increasing minimum flows. Finally, different wetland types could be distinguished with hydrograph shape, e.g. differing wetlands fed by local rainfall from wetlands due to overbank flow (floodplains). These metrics and concepts on hydrograph features have great potential to infer about river-floodplain processes from large rivers and wetland systems.

An investigation of the effects of an arterial drainage scheme on the rainfall-runoff transformation behaviour of the Brosna catchment in Ireland

NASA Astrophysics Data System (ADS)

Bhattarai, K. P.; O'Connor, K. M.

2003-04-01

Inefficient natural land drainage and the consequent frequent flooding of rivers are a problem of particular significance to the Irish economy. Such problems can be attributed less to the amount of annual rainfall, than to the topological configuration of Ireland. Its high maritime rim and relatively flat interior results in poor river gradients, intercepted by many lakes. As a remedial measure to tackle these problems, Arterial Drainage Schemes (ADSs) were started in Ireland from as early as the beginning of the nineteenth century. The major activities carried out under ADSs have been the deepening and widening of channels to increase their discharge-carrying capacity, which naturally affected the hydrological behaviour of the catchments involved. Earlier studies carried out in order to assess the effects of such ADSs on the hydrological behaviour of Irish catchments were concentrated mainly on comparisons of unit hydrographs and relationship between flood peaks of pre- and post-drainage periods. The present study, carried out on the River Brosna catchment in Ireland, concentrates on assessing the changes in the rainfall runoff transformation process, by using the conceptual Soil Moisture Accounting and Routing Model (SMAR), one of the constituent models of the "Galway River Flow Modelling and Forecasting System (GFMFS)" software package. Hydro-meteorological data of the pre-drainage (1942--1947) and post-drainage (1954--2000) periods have been used in this study. The results of the present study show that, for similar patterns of rainfall, the catchment produces higher annual maximum daily flows, and lower annual minimum daily flows in the post-drainage period than in the pre-drainage period. Moreover, the post-drainage unit hydrographs are more "peaky" and have quicker recessions than the pre-drainage counterparts, thus confirming the findings of the earlier studies. It is also observed that, apart from the expected pre-to-post-drainage change, the nature of the catchment response throughout the post-drainage period has not remained the same as it reverted to pre-drainage-like behaviour after the first one-and-a-half decades (around 1969), indicating that the effects of the ADS had died out over that time. This behaviour was also confirmed by comparing the evolving nature of the unit hydrograph produced for a five-year moving calibration window period from 1959 to 1974. It is unclear at this point whether this change was due to the observed reduction in rainfall in the mid-seventies, inefficient maintenance of the channels, land subsidence following drainage, changes in land use, urbanization, climate change, or some other factors or combinations. The results of the present study further show that, during the nineties, the response pattern changed back again to something akin to early post-drainage-like behaviour, the reason for which is even less clear but obviously can not be attributed to the ADS. Further investigations are currently underway to try to explain such changes in the catchment response to rainfall and also to establish if similar changes occurred on other Irish catchments which also underwent arterial drainage schemes.

Overview of surface-water resources at the U.S. Coast Guard Support Center Kodiak, Alaska, 1987-89

USGS Publications Warehouse

Solin, G.L.

1996-01-01

Hydrologic data at a U.S. Coast Guard Support Center on Kodiak Island, Alaska, were collected from 1987 though 1989 to determine hydrologic conditions and if contamination of soils, ground water, or surface water has occurred. This report summarizes the surface-water-discharge data collected during the study and estimates peak, average, and low-flow values for Buskin River near its mouth. Water-discharge measurements were made at least once at 48 sites on streams in or near the Center. Discharges were measured in the Buskin River near its mouth five times during 1987-89 and ranged from 27 to 367 cubic feet per second. Tributaries of Buskin River below Buskin Lake that had discharges greater than 1 cubic foot per second include Bear Creek, Alder Creek, Magazine Creek, Devils Creek and an outlet from Lake Louise. Streams having flows generally greater than 0.1 cubic foot per second but less than 1 cubic foot per second include an unnamed tributary to Buskin River, an unnamed tributary to Lake Catherine and a drainage channel at Kodiak airport. Most other streams flowing into Buskin River, and all streams on Nyman Peninsula, usually had little or no flow except during periods of rainfall or snowmelt. During a low-flow period in February 1989, discharge measurements in Buskin River and its tributaries indicate that three reaches of Buskin River below Buskin Lake lost water to the ground-water system, whereas two reaches gained water; the net gain in streamflow attributed to ground-water inflow at a location near the mouth was estimated to be 2.2 cubic feet per second. The 100-year peak flow for Buskin River near its mouth was estimated to be 4,460 cubic feet per second. Average discharge was estimated to be 125 cubic feet per second and the 7-day 10-year low flow was estimated to be 5.8 cubic feet per second.

South Asia river-flow projections and their implications for water resources

NASA Astrophysics Data System (ADS)

Mathison, C.; Wiltshire, A. J.; Falloon, P.; Challinor, A. J.

2015-12-01

South Asia is a region with a large and rising population, a high dependence on water intense industries, such as agriculture and a highly variable climate. In recent years, fears over the changing Asian summer monsoon (ASM) and rapidly retreating glaciers together with increasing demands for water resources have caused concern over the reliability of water resources and the potential impact on intensely irrigated crops in this region. Despite these concerns, there is a lack of climate simulations with a high enough resolution to capture the complex orography, and water resource analysis is limited by a lack of observations of the water cycle for the region. In this paper we present the first 25 km resolution regional climate projections of river flow for the South Asia region. Two global climate models (GCMs), which represent the ASM reasonably well are downscaled (1960-2100) using a regional climate model (RCM). In the absence of robust observations, ERA-Interim reanalysis is also downscaled providing a constrained estimate of the water balance for the region for comparison against the GCMs (1990-2006). The RCM river flow is routed using a river-routing model to allow analysis of present-day and future river flows through comparison with available river gauge observations. We examine how useful these simulations are for understanding potential changes in water resources for the South Asia region. In general the downscaled GCMs capture the seasonality of the river flows but overestimate the maximum river flows compared to the observations probably due to a positive rainfall bias and a lack of abstraction in the model. The simulations suggest an increasing trend in annual mean river flows for some of the river gauges in this analysis, in some cases almost doubling by the end of the century. The future maximum river-flow rates still occur during the ASM period, with a magnitude in some cases, greater than the present-day natural variability. Increases in river flow could mean additional water resources for irrigation, the largest usage of water in this region, but has implications in terms of inundation risk. These projected increases could be more than countered by changes in demand due to depleted groundwater, increases in domestic use or expansion of water intense industries. Including missing hydrological processes in the model would make these projections more robust but could also change the sign of the projections.

The influence of the macro-sediment from the mountainous area to the river morphology in Taiwan

NASA Astrophysics Data System (ADS)

Chen, S. C.; Wu, C.; Shih, P.

2012-12-01

Chen, Su-Chin scchen@nchu.edu.tw Wu, Chun-Hung* chwu@mail.nchu.edu.tw Dept. Soil & Water Conservation, National Chung Hsing University, Taichung, Taiwan. The Chenyulan River was varied changed with the marco-sediment yielded source area, Shenmu watershed, with 10 debris flow events in the last decade, in Central Taiwan. Multi-term DEMs, the measurement data of the river topographic profile and aerial photos are adopted to analyze the decade influences of the marco-sediment to the river morphology in Chenyulan River. The changes of river morphology by observing the river pattern, calculating the multi-term braided index, and estimating the distribution of sediment deposition and main channel in the river. The response for the macro-sediment from the mountainous areas into the river in the primary stage is the increase in river width, the depth of sediment deposition and volume of sediment transport. The distribution of sediment deposition from upstream landslide and river bank erosion along the river dominates the change of river morphology in the primary stage. The river morphology achieves stable gradually as the river discharge gradually decreases in the later stage. Both of the braided index and the volume of sediment transport decrease, and the river flow maintains in a main channel instead of the braided pattern in this stage. The decade sediment deposition depth is estimated as > 0.5 m, especially > 3.5 m in the sections closed to the sediment-yield source areas, the mean river width increases 15%, and the sediment with a total volume of 8×107 tons has been transported in last decade in Chenyulan River. The river morphology in Chenyulan River maintains a short-term stable, i.e. 2 or 3 years, and changes again because of the flooding events with a large amount of sediment caused by frequently heavy rainfall events in Taiwan. Furthermore, the response of river morphology in Chenyulan River due to the heavy rainfall with a total precipitation of around 860 mm in 3 days in 2009 Typhoon Morakot is also discussed in the study. A extreme river discharge with the return period of 100 year transported the macro sediment with the total volume of around 3.2×107 m3 in 8 days during 2009 Typhoon Morakot, and it also resulted in 18.1% increase of the mean river width and 4 m increase of the mean scouring depth in Chenyulan River, especially the mean increase of 50 m in river width resulted from the total sediment volume of 1.9×107 m3 deposited within 8 km from the sediment-yielded area, i.e. Shenmu watershed. Furthermore, the distribution of sediment deposition in a narrow pass is also discussed in the research. Sediment deposited apparently in the upstream of a narrow pass and also results in the disordered river patterns. The high velocity flow due to the contraction of the river width in the narrow pass section also leads to the headwater erosion in the upstream of the narrow pass section. Contrarily, the unapparent sediment deposition in the downstream of the narrow pass section brings about the stable main channel and swinging flow patterns from our decade observation.

Interconnected ponds operation for flood hazard distribution

NASA Astrophysics Data System (ADS)

Putra, S. S.; Ridwan, B. W.

2016-05-01

The climatic anomaly, which comes with extreme rainfall, will increase the flood hazard in an area within a short period of time. The river capacity in discharging the flood is not continuous along the river stretch and sensitive to the flood peak. This paper contains the alternatives on how to locate the flood retention pond that are physically feasible to reduce the flood peak. The flood ponds were designed based on flood curve number criteria (TR-55, USDA) with the aim of rapid flood peak capturing and gradual flood retuning back to the river. As a case study, the hydrologic condition of upper Ciliwung river basin with several presumed flood pond locations was conceptually designed. A fundamental tank model that reproducing the operation of interconnected ponds was elaborated to achieve the designed flood discharge that will flows to the downstream area. The flood hazard distribution status, as the model performance criteria, will be computed within Ciliwung river reach in Manggarai Sluice Gate spot. The predicted hazard reduction with the operation of the interconnected retention area result had been bench marked with the normal flow condition.

Development of seasonal flow outlook model for Ganges-Brahmaputra Basins in Bangladesh

NASA Astrophysics Data System (ADS)

Hossain, Sazzad; Haque Khan, Raihanul; Gautum, Dilip Kumar; Karmaker, Ripon; Hossain, Amirul

2016-10-01

Bangladesh is crisscrossed by the branches and tributaries of three main river systems, the Ganges, Bramaputra and Meghna (GBM). The temporal variation of water availability of those rivers has an impact on the different water usages such as irrigation, urban water supply, hydropower generation, navigation etc. Thus, seasonal flow outlook can play important role in various aspects of water management. The Flood Forecasting and Warning Center (FFWC) in Bangladesh provides short term and medium term flood forecast, and there is a wide demand from end-users about seasonal flow outlook for agricultural purposes. The objective of this study is to develop a seasonal flow outlook model in Bangladesh based on rainfall forecast. It uses European Centre for Medium-Range Weather Forecasts (ECMWF) seasonal precipitation, temperature forecast to simulate HYDROMAD hydrological model. Present study is limited for Ganges and Brahmaputra River Basins. ARIMA correction is applied to correct the model error. The performance of the model is evaluated using coefficient of determination (R2) and Nash-Sutcliffe Efficiency (NSE). The model result shows good performance with R2 value of 0.78 and NSE of 0.61 for the Brahmaputra River Basin, and R2 value of 0.72 and NSE of 0.59 for the Ganges River Basin for the period of May to July 2015. The result of the study indicates strong potential to make seasonal outlook to be operationalized.

Applications of high resolution rainfall radar data to quantify water temperature dynamics in urban catchments

NASA Astrophysics Data System (ADS)

Croghan, Danny; Van Loon, Anne; Bradley, Chris; Sadler, Jon; Hannnah, David

2017-04-01

Studies relating rainfall events to river water quality are frequently hindered by the lack of high resolution rainfall data. Local studies are particularly vulnerable due to the spatial variability of precipitation, whilst studies in urban environments require precipitation data at high spatial and temporal resolutions. The use of point-source data makes identifying causal effects of storms on water quality problematic and can lead to erroneous interpretations. High spatial and temporal resolution rainfall radar data offers great potential to address these issues. Here we use rainfall radar data with a 1km spatial resolution and 5 minute temporal resolution sourced from the UK Met Office Nimrod system to study the effects of storm events on water temperature (WTemp) in Birmingham, UK. 28 WTemp loggers were placed over 3 catchments on a rural-urban land use gradient to identify trends in WTemp during extreme events within urban environments. Using GIS, the catchment associated with each logger was estimated, and 5 min. rainfall totals and intensities were produced for each sub-catchment. Comparisons of rainfall radar data to meteorological stations in the same grid cell revealed the high accuracy of rainfall radar data in our catchments (<5% difference for studied months). The rainfall radar data revealed substantial differences in rainfall quantity between the three adjacent catchments. The most urban catchment generally received more rainfall, with this effect greatest in the highest intensity storms, suggesting the possibility of urban heat island effects on precipitation dynamics within the catchment. Rainfall radar data provided more accurate sub-catchment rainfall totals allowing better modelled estimates of storm flow, whilst spatial fluctuations in both discharge and WTemp can be simply related to precipitation intensity. Storm flow inputs for each sub-catchment were estimated and linked to changes in WTemp. WTemp showed substantial fluctuations (>1 °C) over short durations (<30 minutes) during storm events in urbanised sub-catchments, however WTemp recovery times were more prolonged. Use of the rainfall radar data allowed increased accuracy in estimates of storm flow timings and rainfall quantities at each sub-catchment, from which the impact of storm flow on WTemp could be quantified. We are currently using the radar data to derive thresholds for rainfall amount and intensity at which these storm deviations occur for each logger, from which the relative effects of land use and other catchment characteristics in each sub-catchment can be assessed. Our use of the rainfall radar data calls into question the validity of using station based data for small scale studies, particularly in urban areas, with high variation apparent in rainfall intensity both spatially and temporally. Variation was particularly high within the heavily urbanised catchment. For water quality studies, high resolution rainfall radar can be implemented to increase the reliability of interpretations of the response of water quality variables to storm water inputs in urban catchments.

Rainfall-runoff model for prediction of waterborne viral contamination in a small river catchment

NASA Astrophysics Data System (ADS)

Gelati, E.; Dommar, C.; Lowe, R.; Polcher, J.; Rodó, X.

2013-12-01

We present a lumped rainfall-runoff model aimed at providing useful information for the prediction of waterborne viral contamination in small rivers. Viral contamination of water bodies may occur because of the discharge of sewage effluents and of surface runoff over areas affected by animal waste loads. Surface runoff is caused by precipitation that cannot infiltrate due to its intensity and to antecedent soil water content. It may transport animal feces to adjacent water bodies and cause viral contamination. We model streamflow by separating it into two components: subsurface flow, which is produced by infiltrated precipitation; and surface runoff. The model estimates infiltrated and non-infiltrated precipitation and uses impulse-response functions to compute the corresponding fractions of streamflow. The developed methodologies are applied to the Glafkos river, whose catchment extends for 102 km2 and includes the city of Patra. Streamflow and precipitation observations are available at a daily time resolution. Waterborne virus concentration measurements were performed approximately every second week from the beginning of 2011 to mid 2012. Samples were taken at several locations: in river water upstream of Patras and in the urban area; in sea water at the river outlet and approximately 2 km south-west of Patras; in sewage effluents before and after treatment. The rainfall-runoff model was calibrated and validated using observed streamflow and precipitation data. The model contribution to waterborne viral contamination prediction was benchmarked by analyzing the virus concentration measurements together with the estimated surface runoff values. The presented methodology may be a first step towards the development of waterborne viral contamination alert systems. Predicting viral contamination of water bodies would benefit sectors such as water supply and tourism.

Hydrological trends in Congo basin (Central Africa)

NASA Astrophysics Data System (ADS)

Laraque, A.

2015-12-01

The last studies concerning some main Congo basin rivers allowed to subdivide their multi-annual flows into several homogeneous phases. As in West Africa, 1970 was the year of the major hydroclimatic event announcing a weaker flowing period. In the absence of long, reliable and available flow series in the whole Congo basin of 3,8 106km2 area, the present study concerns only the Congo River at Brazzaville/Kinshasa and two of the main tributaries of its right bank, Ubangui at Bangui and Sangha at Ouesso, with hydrologic data available from the first half of the 20th century. For Congo River, in comparison with its secular average, after an excess flow noted during the sixties, a significant drop of 10% occurs in the eighties. However, a return to normal conditions is recorded from 1995. For Ubangui and Sangha, the flows remain weaker since 1970. Within the bi-modal hydrological regimes of Sangha and Congo river, because they are equatorial, we also observe since many years a small decline of the secondary flood of april-june. This phenomenon was emphasized especially these last years and is founded in others rivers of Central Africa, where it reflects the variations of de rainfall patterns and the surfaces features. For the Congo basin, the situation is worrying because that affects the inland waterway transport. Moreover that wakes also the project of junction by a canal of the Congo and Chari basins for fighting against the hydrological decline of Lake Chad.

Application of scenario-neutral methods to quantify impacts of climate change on water resources in East Africa

NASA Astrophysics Data System (ADS)

Ascott, M.; Macdonald, D.; Lapworth, D.; Tindimugaya, C.

2017-12-01

Quantification of the impact of climate change on water resources is essential for future resource planning. Unfortunately, climate change impact studies in African regions are often hindered by the extent in variability in future rainfall predictions, which also diverge from current drying trends. To overcome this limitation, "scenario-neutral" methods have been developed which stress a hydrological system using a wide range of climate futures to build a "climate response surface". We developed a hydrological model and scenario-neutral framework to quantify climate change impacts on river flows in the Katonga catchment, Uganda. Using the lumped catchment model GR4J, an acceptable calibration to historic daily flows (1966 - 2010, NSE = 0.69) was achieved. Using a delta change approach, we then systematically changed rainfall and PET inputs to develop response surfaces for key metrics, developed with Ugandan water resources planners (e.g. Q5, Q95). Scenarios from the CMIP5 models for 2030s and 2050s were then overlain on the response surface. The CMIP5 scenarios show consistent increases in temperature but large variability in rainfall increases, which results in substantial variability in increases in river flows. The developed response surface covers a wide range of climate futures beyond the CMIP5 projections, and can help water resources planners understand the sensitivity of water resource systems to future changes. When future climate scenarios are available, these can be directly overlain on the response surface without the need to re-run the hydrological model. Further work will consider using scenario-neutral approaches in more complex, semi-distributed models (e.g. SWAT), and will consider land use and socioeconomic change.

How has climate change altered network connectivity in a mountain stream network?

NASA Astrophysics Data System (ADS)

Ward, A. S.; Schmadel, N.; Wondzell, S. M.; Johnson, S.

2017-12-01

Connectivity along river networks is broadly recognized as dynamic, with seasonal and event-based expansion and contraction of the network extent. Intermittently flowing streams are particularly important as they define a crucial threshold for continuously connected waters that enable migration by aquatic species. In the Pacific northwestern U.S., changes in atmospheric circulation have been found to alter rainfall patterns and result in decreased summer low-flows in the region. However, the impact of this climate dynamic on network connectivity is heretofore unstudied. Thus, we ask: How has connectivity in the riparian corridor changed in response to observed changes in climate? In this study we take the well-studied H.J. Andrews Experimental Forest as representative of mountain river networks in the Pacific northwestern U.S. First, we analyze 63 years of stream gauge information from a network of 11 gauges to document observed changes in timing and magnitude of stream discharge. We found declining magnitudes of seasonal low-flows and shifting seasonality of water export from the catchment, both of which we attribute to changes in precipitation timing and storage as snow vs. rainfall. Next, we use these discharge data to drive a reduced-complexity model of the river network to simulate network connectivity over 63 years. Model results show that network contraction (i.e., minimum network extent) has decreased over the past 63 years. Unexpectedly, the increasing winter peak flows did not correspond with increasing network expansion, suggesting a geologic control on maximum flowing network extent. We find dynamic expansion and contraction of the network primarily occurs during period of catchment discharge less than about 1 m3/s at the outlet, whereas the network extent is generally constant for discharges from 1 to 300 m3/s. Results of our study are of interest to scientists focused on connectivity as a control on ecological processes both directly (e.g., fish migration) and indirectly (e.g., stream temperature modeling). Additionally, our results inform management and regulatory needs such as estimating connectivity for entire river networks as a basis for regulation, and identifying the complexity of a shifting baseline in identifying a regulatory basis.

[Variation characteristics and environmental significant of trace elements under rainfall condition in karst groundwater].

PubMed

Chen, Xue-Bin; Yang, Ping-Heng; Lan, Jia-Cheng; Mo, Xue; Shi, Yang

2014-01-01

Chemical dynamics of Qingmuguan karst groundwater system were continuously monitored during the rainfall events. A series of high-resolution concentrations data on trace elements, such as barium, strontium, iron, manganese, aluminum, and other major elements were acquired. Correlation analysis and analysis of concentration curve were employed to identify the sources and migration path of the trace elements. And the formation process of trace elements in groundwater was discussed with the geological background of underground river basin. Research shows that barium and strontium derived from carbonate dissolution appeared to be stored in features such as fissures and pores. These two ions were recharged into the underground river by diffusion during precipitation, which resulted in small changes in the their concentration. However total iron, total manganese and aluminum derived from soil erosion varied relatively widely with strong response to rainfall, attributing to the migration of total iron and aluminum with overland flow to recharge the subterranean river directly via sinkholes while total manganese via soil-rock porous media. The results showed that concentrations of all the five trace elements were below 1 mg x L(-1), and the highest concentrations of total iron, total manganese and aluminum exceeded the limit of drinking water. To some extent, the concentrations of total iron and aluminum may be an indicator for soil erosion and water quality.

Geomorphology and river dynamics of the lower Copper River, Alaska

USGS Publications Warehouse

Brabets, Timothy P.; Conaway, Jeffrey S.

2009-01-01

Located in south-central Alaska, the Copper River drains an area of more than 24,000 square miles. The average annual flow of the river near its mouth is 63,600 cubic feet per second, but is highly variable between winter and summer. In the winter, flow averages approximately 11,700 cubic feet per second, and in the summer, due to snowmelt, rainfall, and glacial melt, flow averages approximately 113,000 cubic feet per second, an order of magnitude higher. About 15 miles upstream of its mouth, the Copper River flows past the face of Childs Glacier and enters a large, broad, delta. The Copper River Highway traverses this flood plain, and in 2008, 11 bridges were located along this section of the highway. The bridges cross several parts of the Copper River and in recent years, the changing course of the river has seriously damaged some of the bridges.Analysis of aerial photography from 1991, 1996, 2002, 2006, and 2007 indicates the eastward migration of a channel of the Copper River that has resulted in damage to the Copper River Highway near Mile 43.5. Migration of another channel in the flood plain has resulted in damage to the approach of Bridge 339. As a verification of channel change, flow measurements were made at bridges along the Copper River Highway in 2005–07. Analysis of the flow measurements indicate that the total flow of the Copper River has shifted from approximately 50 percent passing through the bridges at Mile 27, near the western edge of the flood plain, and 50 percent passing through the bridges at Mile 36–37 to approximately 5 percent passing through the bridges at Mile 27 and 95 percent through the bridges at Mile 36–37 during average flow periods.The U.S. Geological Survey’s Multi-Dimensional Surface-Water Modeling System was used to simulate water-surface elevation and velocity, and to compute bed shear stress at two areas where the Copper River is affecting the Copper River Highway. After calibration, the model was used to examine the effects that betterments, such as guide banks or bridge extensions, would have on flow conditions and to provide sound conceptual information that could help decide if a proposed betterment will work or determine potential problems that need to be addressed for a particular betterment. The ability of the model to simulate these hydraulic conditions was constrained by the accuracy and level of channel geometry detail, which is constantly changing in the lower Copper River.

Applications of multiscale change point detections to monthly stream flow and rainfall in Xijiang River in southern China, part I: correlation and variance

NASA Astrophysics Data System (ADS)

Zhu, Yuxiang; Jiang, Jianmin; Huang, Changxing; Chen, Yongqin David; Zhang, Qiang

2018-04-01

This article, as part I, introduces three algorithms and applies them to both series of the monthly stream flow and rainfall in Xijiang River, southern China. The three algorithms include (1) normalization of probability distribution, (2) scanning U test for change points in correlation between two time series, and (3) scanning F-test for change points in variances. The normalization algorithm adopts the quantile method to normalize data from a non-normal into the normal probability distribution. The scanning U test and F-test have three common features: grafting the classical statistics onto the wavelet algorithm, adding corrections for independence into each statistic criteria at given confidence respectively, and being almost objective and automatic detection on multiscale time scales. In addition, the coherency analyses between two series are also carried out for changes in variance. The application results show that the changes of the monthly discharge are still controlled by natural precipitation variations in Xijiang's fluvial system. Human activities disturbed the ecological balance perhaps in certain content and in shorter spells but did not violate the natural relationships of correlation and variance changes so far.

The Parana paradox: can a model explain the decadal impacts of climate variability and land-cover change?

NASA Astrophysics Data System (ADS)

Lee, E.; Moorcroft, P. R.; Livino, A.; Briscoe, J.

2013-12-01

Since the 1970s, despite a decrease in rainfall, flow in the Parana river has increased. This paradox is explored using the Ecosystem Demography (ED) model. If there were no change in land cover, the modeled runoff decreased from the 1970s to the 2000s by 11.8% (with 1970 land cover) or 18.8% (with 2008 land cover). When the model is run holding climate constant, the decadal average of the modeled runoff increased by 24.4% (with the 1970s climate) or by 33.6% (with 2000s climate). When the model is run allowing both the actual climate and land-cover changes, the model gives an increase in the decadal average of runoff by 8.5%. This agrees well with 10.5% increase in the actual stream flow as measured at Itaipu. There are three main conclusions from this work. First, the ED model is able to explain a major, paradoxical, reality in the Parana basin. Second, it is necessary to take into account both climate and land use changes when exploring past or future changes in river flows. Third, the ED model, now coupled with a regional climate model (i.e., EDBRAMS), is a sound basis for exploring likely changes in river flows in major South American rivers.

Assessment of relationship between rainfall and Escherichia coli in clams (Chamelea gallina) using the Bayes Factor.

PubMed

Ciccarelli, Cesare; Semeraro, Angela Marisa; Leinoudi, Melina; Trani, Vittoria Di; Murru, Sandra; Capocasa, Piero; Ciccarelli, Elena; Sacchini, Luca

2017-08-16

Consumption of bivalve shellfish harvested from water contaminated with sewage pollution presents a risk of human infections and targeting control measures require a good understanding of environmental factors influencing the transport and the fate of faecal contaminants within the hydrological catchments. Although there has been extensive development of regression models, the point of this paper, focused on the relationship between rainfall events and concentrations of Escherichia coli monitored in clams, was the use of a Bayesian approach, by the Bayes Factor. The study was conducted on clams harvested from the south coast of Marche Region (Italy), a coastal area impacted by continuous treated effluents, intermittent rainfalldependent untreated sewage spillage - as a consequence of stormwater overflowing - and rivers with an ephemeral flow regime. The work compared the different interpretation criteria of Bayes Factor, confirmed that E. coli concentrations in clams from the studied area varied in correlation with rainfall events, and demonstrated the effectiveness of Bayes Factor in the assessment of shellfish quality in coastal marine waters. However, it suggested that further investigations would be warranted to determine which environmental factors provide the better basis for accurate and timely predictions. Furthermore the gathered data could be useful, to the local authorities of Marche Region, in the definition of flexible monitoring programmes, taking into account the atmospheric events that could affect the correct functioning of sewage managing systems and the flow of tributary rivers.

Great expectations: Flow restoration and sediment transport in the Waimea River, Kaua'i

NASA Astrophysics Data System (ADS)

Gomez, Basil

2018-04-01

Conventional and novel observations made in the Waimea River basin between 1960 and 1995 permit the total riverine mass flux to be estimated and the influence that flow restoration will have on sediment dynamics in the river's lower reaches to be assessed. Flows between the threshold for sediment transport ( 6.0 m3 s-1) and the most effective flow (80.7 m3 s-1) recur annually and transport 60% of the Waimea River's suspended sediment load. Discharges of this magnitude essentially were unaffected by plantation era agricultural diversions of 2.3 ± 0.7 m3 s-1. The modern-day mass flux from the Waimea River basin is 155 ± 38 t km-2 y-1, and comparison with an independent cosmogenic nuclide-based estimate implies that it has remained at about this level for the past 10 ky. Previous work indicated that: (i) most of the sand the Waimea River transports to the coast is derived from steep, rapidly eroding, sparsely vegetated, bedrock-dominated hillslopes; and (ii) the sediment transport regime of the Waimea River is supply-limited at very high discharges (recurrence interval > 2.5 years). Consequently, major floods tend to remove sand from the estuary. Climate change has caused a statewide decline in heavy rainfall, and a commensurate decline in the magnitude of peak flows in the basin's pristine, undiverted headwaters over the past 97 years. The effect this secular change in climate presently is having on streamflow was foreshadowed in the late 1970s by a naturally occurring, warm Pacific Decadal Oscillation phase reduction in the magnitude of flows with low exceedance probabilities. Additionally, the controlling base level at the river mouth has risen and been displaced seaward. Simple proportionality approximations show that, for a constant sediment supply, aggradation will occur if either the magnitude of flows with a low exceedance probability declines and/or base level rises. Thus, anthropogenic stresses on Waimea River's lower reaches are not derived from the within-basin influence agricultural diversions exert on the flow regime and will not be resolved by restoring flow to the river. These stresses primarily accrue from extrinsic factors that will continue to influence the river's hydrologic and sediment transport regimes until global, offsetting, climate-ameliorating measures are implemented.

Assessment of Flood Mitigation Solutions Using a Hydrological Model and Refined 2D Hydrodynamic Simulations

NASA Astrophysics Data System (ADS)

Khuat Duy, B.; Archambeau, P.; Dewals, B. J.; Erpicum, S.; Pirotton, M.

2009-04-01

Following recurrent inundation problems on the Berwinne catchment, in Belgium, a combined hydrologic and hydrodynamic study has been carried out in order to find adequate solutions for the floods mitigation. Thanks to detailed 2D simulations, the effectiveness of the solutions can be assessed not only in terms of discharge and height reductions in the river, but also with other aspects such as the inundated surfaces reduction and the decrease of inundated buildings and roads. The study is carried out in successive phases. First, the hydrological runoffs are generated using a physically based and spatially distributed multi-layer model solving depth-integrated equations for overland flow, subsurface flow and baseflow. Real floods events are simulated using rainfall series collected at 8 stations (over 20 years of available data). The hydrological inputs are routed through the river network (and through the sewage network if relevant) with the 1D component of the modelling system, which solves the Saint-Venant equations for both free-surface and pressurized flows in a unified way. On the main part of the river, the measured river cross-sections are included in the modelling, and existing structures along the river (such as bridges, sluices or pipes) are modelled explicitely with specific cross sections. Two gauging stations with over 15 years of continuous measurements allow the calibration of both the hydrologic and hydrodynamic models. Second, the flood mitigation solutions are tested in the simulations in the case of an extreme flooding event, and their effects are assessed using detailed 2D simulations on a few selected sensitive areas. The digital elevation model comes from an airborne laser survey with a spatial resolution of 1 point per square metre and is completed in the river bed with a bathymetry interpolated from cross-section data. The upstream discharge is extracted from the 1D simulation for the selected rainfall event. The study carried out with this methodology allowed to assess the suggested solutions with multiple effectiveness criteria and therefore constitutes a very useful support for decision makers.

Mud Flow - Slow and Fast

NASA Astrophysics Data System (ADS)

Mei, C. C.; Liu, K.-F.; Yuhi, M.

Heavy and persistent rainfalls in mountainous areas can loosen the hillslope and induce mud flows which can move stones, boulders and even trees, with destructive power on their path. In China where 70% of the land surface is covered by mountains, debris flows due to landslides or rainfalls affect over 18.6% of the nation. Over 10,000 debris flow ravines have been identified; hundreds of lives are lost every year [1]. While accurate assessment is still pending, mud flows caused by Hurr icane Mitch in 1998 have incurred devastating floods in Central America. In Honduras alone more than 6000 people perished. Half of the nation's infrastructures were damaged. Mud flows can also be the result of volcanic eruption. Near the volcano, lava and pyroclastic flows dominate. Further downstream solid particles become smaller and can mix with river or lake water, rainfall, melting snow or ice, or eroded soil, resulting in hyperconcentrated mud mixed with rocks. The muddy debris can travel at high speeds over tens of miles down the hill slopes and devastate entire communities. In 1985 the catastrophic eruption of Nevado del Ruiz in Colombia resulted in mud flows which took the life of 23,000 inhabitants in the town of Amero [2]. During the eruption of Mt. Pinatubo in Phillipnes in 1991, one cubic mile of volcanic ash and rock fragments fell on the mountain slopes. Seasonal rain in the following months washed down much of the loose deposits, causing damage to 100,000 villages. These catastrophes have been vividly recorded in the film documentary by Lyons [3].

Satellite-based Flood Modeling Using TRMM-based Rainfall Products

PubMed Central

Harris, Amanda; Rahman, Sayma; Hossain, Faisal; Yarborough, Lance; Bagtzoglou, Amvrossios C.; Easson, Greg

2007-01-01

Increasingly available and a virtually uninterrupted supply of satellite-estimated rainfall data is gradually becoming a cost-effective source of input for flood prediction under a variety of circumstances. However, most real-time and quasi-global satellite rainfall products are currently available at spatial scales ranging from 0.25° to 0.50° and hence, are considered somewhat coarse for dynamic hydrologic modeling of basin-scale flood events. This study assesses the question: what are the hydrologic implications of uncertainty of satellite rainfall data at the coarse scale? We investigated this question on the 970 km2 Upper Cumberland river basin of Kentucky. The satellite rainfall product assessed was NASA's Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA) product called 3B41RT that is available in pseudo real time with a latency of 6-10 hours. We observed that bias adjustment of satellite rainfall data can improve application in flood prediction to some extent with the trade-off of more false alarms in peak flow. However, a more rational and regime-based adjustment procedure needs to be identified before the use of satellite data can be institutionalized among flood modelers. PMID:28903302

Sediment yield during typhoon events in relation to landslides, rainfall, and catchment areas in Taiwan

NASA Astrophysics Data System (ADS)

Chen, Chi-Wen; Oguchi, Takashi; Hayakawa, Yuichi S.; Saito, Hitoshi; Chen, Hongey; Lin, Guan-Wei; Wei, Lun-Wei; Chao, Yi-Chiung

2018-02-01

Debris sourced from landslides will result in environmental problems such as increased sediment discharge in rivers. This study analyzed the sediment discharge of 17 main rivers in Taiwan during 14 typhoon events, selected from the catchment area and river length, that caused landslides according to government reports. The measured suspended sediment and water discharge, collected from hydrometric stations of the Water Resources Agency of Taiwan, were used to establish rating-curve relationships, a power-law relation between them. Then sediment discharge during typhoon events was estimated using the rating-curve method and the measured data of daily water discharge. Positive correlations between sediment discharge and rainfall conditions for each river indicate that sediment discharge increases when a greater amount of rainfall or a higher intensity of rainfall falls during a typhoon event. In addition, the amount of sediment discharge during a typhoon event is mainly controlled by the total amount of rainfall, not by peak rainfall. Differences in correlation equations among the rivers suggest that catchments with larger areas produce more sediment. Catchments with relatively low sediment discharge show more distinct increases in sediment discharge in response to increases in rainfall, owing to the little opportunity for deposition in small catchments with high connectivity to rivers and the transportation of the majority of landslide debris to rivers during typhoon events. Also, differences in geomorphic and geologic conditions among catchments around Taiwan lead to a variety of suspended sediment dynamics and the sediment budget. Positive correlation between average sediment discharge and average area of landslides during typhoon events indicates that when larger landslides are caused by heavier rainfall during a typhoon event, more loose materials from the most recent landslide debris are flushed into rivers, resulting in higher sediment discharge. The high proportion of large landslides in Taiwan contributes significantly to the high annual sediment yield, which is among the world's highest despite the small area of Taiwan.

Estimation of Surface Runoff in the Jucar River Basin from Rainfall Data and SMOS Soil Moisture

NASA Astrophysics Data System (ADS)

Garcia Leal, Julio A.; Estrela, Teodoro; Fidalgo, Arancha; Gabaldo, Onofre; Gonzalez Robles, Maura; Herrera Daza, Eddy; Khodayar, Samiro; Lopez-Baeza, Ernesto

2013-04-01

Surface runoff is the water that flows after soil is infiltrated to full capacity and excess water from rain, meltwater, or other sources flows over the land. When the soil is saturated and the depression storage filled, and rain continues to fall, the rainfall will immediately produce surface runoff. The Soil Conservation Service Curve Number (SCS-CN) method is widely used for determining the approximate direct runoff volume for a given rainfall event in a particular area. The advantage of the method is its simplicity and widespread inclusion in existing computer models. It was originally developed by the US Department of Agriculture, Soil Conservation Service, and documented in detail in the National Engineering Handbook, Sect. 4: Hydrology (NEH-4) (USDA-SCS, 1985). Although the SCS-CN method was originally developed in the United States and mainly for the evaluation of storm runoff in small agricultural watersheds, it soon evolved well beyond its original objective and was adopted for various land uses and became an integral part of more complex, long-term, simulation models. The basic assumption of the SCS-CN method is that, for a single storm, the ratio of actual soil retention after runoff begins to potential maximum retention is equal to the ratio of direct runoff to available rainfall. This relationship, after algebraic manipulation and inclusion of simplifying assumptions, results in the following equation given in USDA-SCS (1985): (P--0,2S)2 Q = (P + 0,8S) where Q is the average runoff (mm), P the effective precipitation (mm) and S is potential maximum retention (mm) after the rainfall event. The study has been applied to the Jucar River Basin area, East of Spain. A selection of recent significant rainfall events has been made corresponding to the periods around 22nd November, 2011 and 28-29 September and 10 October, 2012, from Jucar River Basin Authority rain gauge data. Potential maximum retention values for each point have been assumed as the first SMOS soil moisture values available at the closest DGG node immediately after saturation produced by the rain. The results are shown as maps of precipitation and soil moisture obtained using a V4 integration method between a linear and nearest neighbour methods. Surface runoff maps are consequently obtained using the SCS-CN equation given earlier. These results have also been compared to COSMO-CLM model simulations for the same periods. It is envisaged to obtain precipitation maps from MSG-SEVIRI data.

Simulation of rainfall-runoff for major flash flood events in Karachi

NASA Astrophysics Data System (ADS)

Zafar, Sumaira

2016-07-01

Metropolitan city Karachi has strategic importance for Pakistan. With the each passing decade the city is facing urban sprawl and rapid population growth. These rapid changes directly affecting the natural resources of city including its drainage pattern. Karachi has three major cities Malir River with the catchment area of 2252 sqkm and Lyari River has catchment area about 470.4 sqkm. These are non-perennial rivers and active only during storms. Change of natural surfaces into hard pavement causing an increase in rainfall-runoff response. Curve Number is increased which is now causing flash floods in the urban locality of Karachi. There is only one gauge installed on the upstream of the river but there no record for the discharge. Only one gauge located at the upstream is not sufficient for discharge measurements. To simulate the maximum discharge of Malir River rainfall (1985 to 2014) data were collected from Pakistan meteorological department. Major rainfall events use to simulate the rainfall runoff. Maximum rainfall-runoff response was recorded in during 1994, 2007 and 2013. This runoff causes damages and inundation in floodplain areas of Karachi. These flash flooding events not only damage the property but also cause losses of lives

Indian Summer Monsoon Rainfall: Implications of Contrasting Trends in the Spatial Variability of Means and Extremes

PubMed Central

Ghosh, Subimal; Vittal, H.; Sharma, Tarul; Karmakar, Subhankar; Kasiviswanathan, K. S.; Dhanesh, Y.; Sudheer, K. P.; Gunthe, S. S.

2016-01-01

India’s agricultural output, economy, and societal well-being are strappingly dependent on the stability of summer monsoon rainfall, its variability and extremes. Spatial aggregate of intensity and frequency of extreme rainfall events over Central India are significantly increasing, while at local scale they are spatially non-uniform with increasing spatial variability. The reasons behind such increase in spatial variability of extremes are poorly understood and the trends in mean monsoon rainfall have been greatly overlooked. Here, by using multi-decadal gridded daily rainfall data over entire India, we show that the trend in spatial variability of mean monsoon rainfall is decreasing as exactly opposite to that of extremes. The spatial variability of extremes is attributed to the spatial variability of the convective rainfall component. Contrarily, the decrease in spatial variability of the mean rainfall over India poses a pertinent research question on the applicability of large scale inter-basin water transfer by river inter-linking to address the spatial variability of available water in India. We found a significant decrease in the monsoon rainfall over major water surplus river basins in India. Hydrological simulations using a Variable Infiltration Capacity (VIC) model also revealed that the water yield in surplus river basins is decreasing but it is increasing in deficit basins. These findings contradict the traditional notion of dry areas becoming drier and wet areas becoming wetter in response to climate change in India. This result also calls for a re-evaluation of planning for river inter-linking to supply water from surplus to deficit river basins. PMID:27463092

Indian Summer Monsoon Rainfall: Implications of Contrasting Trends in the Spatial Variability of Means and Extremes.

PubMed

Ghosh, Subimal; Vittal, H; Sharma, Tarul; Karmakar, Subhankar; Kasiviswanathan, K S; Dhanesh, Y; Sudheer, K P; Gunthe, S S

2016-01-01

India's agricultural output, economy, and societal well-being are strappingly dependent on the stability of summer monsoon rainfall, its variability and extremes. Spatial aggregate of intensity and frequency of extreme rainfall events over Central India are significantly increasing, while at local scale they are spatially non-uniform with increasing spatial variability. The reasons behind such increase in spatial variability of extremes are poorly understood and the trends in mean monsoon rainfall have been greatly overlooked. Here, by using multi-decadal gridded daily rainfall data over entire India, we show that the trend in spatial variability of mean monsoon rainfall is decreasing as exactly opposite to that of extremes. The spatial variability of extremes is attributed to the spatial variability of the convective rainfall component. Contrarily, the decrease in spatial variability of the mean rainfall over India poses a pertinent research question on the applicability of large scale inter-basin water transfer by river inter-linking to address the spatial variability of available water in India. We found a significant decrease in the monsoon rainfall over major water surplus river basins in India. Hydrological simulations using a Variable Infiltration Capacity (VIC) model also revealed that the water yield in surplus river basins is decreasing but it is increasing in deficit basins. These findings contradict the traditional notion of dry areas becoming drier and wet areas becoming wetter in response to climate change in India. This result also calls for a re-evaluation of planning for river inter-linking to supply water from surplus to deficit river basins.

Application of Virtual Rain and Stream Gauge Information Service for Improved Flood Early Warning System in Lower Mekong Countries

NASA Astrophysics Data System (ADS)

Basnayake, S. B.; Jayasinghe, S.; Meechaiya, C.; Markert, K. N.; Lee, H.; Towashiraporn, P.; Anderson, E.; Okeowo, M. A.

2017-12-01

Asia is the most vulnerable region in the world to hydro-meteorological extreme events, exacerbated by climate variability and change. Impacts of floods have been on the rapid increase in the recent decades. Myanmar is one of the most vulnerable countries in the lower Mekong region due to its socioeconomic situation (eg; Nargis in 2008, monsoon floods in 2015, etc). Early warning is an effective way to prepare for hydro-meteorological hazards, to minimize disaster risks; however, early warning systems in Myanmar are seriously hampered by limited observation networks. The Virtual Rain and Stream Gauge Information Service (VRSGIS) has been developed by SERVIR-Mekong program of Asian Disaster Preparedness Center (ADPC) to address these gaps and to provide dense, satellite-based rainfall and water level data, which are calibrated and validated with available in-situ observations. This service would enhance decision making in lower Mekong countries, including Myanmar, to minimize impacts of impending disasters. This service contains rainfall data from GPM IMERG and GSMap, CMORPH, TRMM, and CHIRPS, and water levels for 15 locations using Jason-2/3 altimetry. The virtual daily rainfall data sets are being calibrated with Gamma distribution method and are made publicly accessible through a user-friendly web interface.This paper presents a case study of satellite-derived rainfall data accessed from VRSGIS for hydrological modeling in Myanmar, to estimate inundation areas in Kalay township area of Chindwin River basin during the country's worst flood in 2015. Twelve out of fourteen States of Myanmar were severely affected, 103 people were killed, and one million were displaced due to heavy rains associated with Komen cyclone. The aforementioned rainfall data products are used as inputs for HEC-HMS hydrological runoff model to calculate river flows along Chindwin River, and HEC-RAS hydraulic model is used to estimate inundation areas in downstream including Kalay township area. Model results (inundations) are compared with the estimates of water levels of Jason 2/3 measurements from two locations along the river. The results encourage us to use satellite-derived rainfall data over upstream areas to improve flood modeling, which contributes to improved flood early warning in Myanmar and other lower Mekong countries.

Flood of May 2006 in York County, Maine

USGS Publications Warehouse

Stewart, Gregory J.; Kempf, Joshua P.

2008-01-01

A stalled low-pressure system over coastal New England on Mother's Day weekend, May 13-15, 2006, released rainfall in excess of 15 inches. This flood (sometimes referred to as the 'Mother's Day flood') caused widespread damage to homes, businesses, roads, and structures in southern Maine. The damage to public property in York County was estimated to be $7.5 million. As a result of these damages, a presidential disaster declaration was enacted on May 25, 2006, for York County, Maine. Peak-flow recurrence intervals for eight of the nine streams studied were calculated to be greater than 500 years. The peak-flow recurrence interval of the remaining stream was calculated to be between a 100-year and a 500-year interval. This report provides a detailed description of the May 2006 flood in York County, Maine. Information is presented on peak streamflows and peak-flow recurrence intervals on nine streams, peak water-surface elevations for 80 high-water marks at 25 sites, hydrologic conditions before and after the flood, comparisons with published Flood Insurance Studies, and places the May 2006 flood in context with historical floods in York County. At sites on several streams, differences were observed between peak flows published in the Flood Insurance Studies and those calculated for this study. The differences in the peak flows from the published Flood Insurance Studies and the flows calculated for this report are within an acceptable range for flows calculated at ungaged locations, with the exception of those for the Great Works River and Merriland River. For sites on the Mousam River, Blacksmith Brook, Ogunquit River, and Cape Neddick River, water-surface elevations from Flood Insurance Studies differed with documented water-surface elevations from the 2006 flood.

East Asian Summer Monsoon Rainfall: A Historical Perspective of the 1998 Flood over Yangtze River

NASA Technical Reports Server (NTRS)

Weng, H.-Y.; Lau, K.-M.

1999-01-01

One of the main factors that might have caused the disastrous flood in China during 1998 summer is long-term variations that include a trend indicating increasing monsoon rainfall over the Yangtze River Valley. China's 160-station monthly rainfall anomaly for the summers of 1955-98 is analyzed for exploring such long-term variations. Singular value decomposition (SVD) between the summer rainfall and the global sea surface temperature (SST) anomalies reveals that the rainfall over Yangtze River Valley is closely related to global and regional SST variabilities at both interannual and interdecadal timescales. SVD1 mode links the above normal rainfall condition in central China to an El Nino-like SSTA distribution, varying on interannual timescale modified by a trend during the period. SVD3 mode links positive rainfall anomaly in Yangtze River Valley to the warm SST anomaly in the subtropical western Pacific, varying on interannual timescales modified by interdecadal timescales. This link tends to be stronger when the Nino3 area becomes colder and the western subtropical Pacific becomes warmer. The 1998 summer is a transition season when the 1997/98 El Nino event was in its decaying phase, and the SST in the Nino3 area emerged below normal anomaly while the subtropical western Pacific SST above normal. Thus, the first and third SVD modes become dominant in 1998 summer, favoring more Asian summer monsoon rainfall over the Yangtze River Valley.

Use of Iqqm For Management of A Regulated River System

NASA Astrophysics Data System (ADS)

Hameed, T.; Podger, G.; Harrold, T. I.

The Integrated Quantity-Quality Model (IQQM) is a modelling tool for the planning and management of water-sharing issues within regulated and unregulated river sys- tems. IQQM represents the major river system processes, including inflows, rainfall and evaporation, infiltration, and flow routing down river channels and floodplains. It is a water balance model that operates on a daily timestep and can represent reser- voirs, wetlands, surface water/groundwater interaction, and soil moisture deficit for irrigation areas, along with many other features of both natural and regulated systems. IQQM can be customised for any river valley, and has proven to be a useful tool for the development, evaluation, and selection of operational rules for complex river systems. The Lachlan catchment lies within Australia's largest river system, the Murray- Darling Basin. Extensive development in the Murray-Darling Basin within the last 100 years has resulted in land degradation, increased salinity, poor water quality, damage to wetlands, and decline in native fish species. In response to these issues, in 1995 the Murray-Darling Basin Commission (MDBC) imposed restrictions on growth in diver- sions (the "MDBC Cap"), and the New South Wales government has more recently applied its own restrictions (the "River Flow Objectives"). To implement the MDBC Cap and the River Flow Objectives, new operational rules were required. This presen- tation describes how IQQM was used to develop and evaluate these rules for the Lach- lan system. In particular, rules for release of environmental flows were developed and evaluated. The model helped identify the flow window that would be most beneficial to the riverine environment, the critical time of year when environmental releases should be made, and resource constraint conditions when environmental releases should not be made. This process also involved intensive consultations with stakeholders. The role of IQQM within this process was to help the stakeholders understand the inter- action of various users within the valley, and the impacts of the operational rules on them.

Regionalized rainfall-runoff model to estimate low flow indices

NASA Astrophysics Data System (ADS)

Garcia, Florine; Folton, Nathalie; Oudin, Ludovic

2016-04-01

Estimating low flow indices is of paramount importance to manage water resources and risk assessments. These indices are derived from river discharges which are measured at gauged stations. However, the lack of observations at ungauged sites bring the necessity of developing methods to estimate these low flow indices from observed discharges in neighboring catchments and from catchment characteristics. Different estimation methods exist. Regression or geostatistical methods performed on the low flow indices are the most common types of methods. Another less common method consists in regionalizing rainfall-runoff model parameters, from catchment characteristics or by spatial proximity, to estimate low flow indices from simulated hydrographs. Irstea developed GR2M-LoiEau, a conceptual monthly rainfall-runoff model, combined with a regionalized model of snow storage and melt. GR2M-LoiEau relies on only two parameters, which are regionalized and mapped throughout France. This model allows to cartography monthly reference low flow indices. The inputs data come from SAFRAN, the distributed mesoscale atmospheric analysis system, which provides daily solid and liquid precipitation and temperature data from everywhere in the French territory. To exploit fully these data and to estimate daily low flow indices, a new version of GR-LoiEau has been developed at a daily time step. The aim of this work is to develop and regionalize a GR-LoiEau model that can provide any daily, monthly or annual estimations of low flow indices, yet keeping only a few parameters, which is a major advantage to regionalize them. This work includes two parts. On the one hand, a daily conceptual rainfall-runoff model is developed with only three parameters in order to simulate daily and monthly low flow indices, mean annual runoff and seasonality. On the other hand, different regionalization methods, based on spatial proximity and similarity, are tested to estimate the model parameters and to simulate low flow indices in ungauged sites. The analysis is carried out on 691 French catchments that are representative of various hydro-meteorological behaviors. The results are validated with a cross-validation procedure and are compared with the ones obtained with GR4J, a conceptual rainfall-runoff model, which already provides daily estimations, but involves four parameters that cannot easily be regionalized.

How temporal patterns in rainfall determine the geomorphology and carbon fluxes of tropical peatlands.

PubMed

Cobb, Alexander R; Hoyt, Alison M; Gandois, Laure; Eri, Jangarun; Dommain, René; Abu Salim, Kamariah; Kai, Fuu Ming; Haji Su'ut, Nur Salihah; Harvey, Charles F

2017-06-27

Tropical peatlands now emit hundreds of megatons of carbon dioxide per year because of human disruption of the feedbacks that link peat accumulation and groundwater hydrology. However, no quantitative theory has existed for how patterns of carbon storage and release accompanying growth and subsidence of tropical peatlands are affected by climate and disturbance. Using comprehensive data from a pristine peatland in Brunei Darussalam, we show how rainfall and groundwater flow determine a shape parameter (the Laplacian of the peat surface elevation) that specifies, under a given rainfall regime, the ultimate, stable morphology, and hence carbon storage, of a tropical peatland within a network of rivers or canals. We find that peatlands reach their ultimate shape first at the edges of peat domes where they are bounded by rivers, so that the rate of carbon uptake accompanying their growth is proportional to the area of the still-growing dome interior. We use this model to study how tropical peatland carbon storage and fluxes are controlled by changes in climate, sea level, and drainage networks. We find that fluctuations in net precipitation on timescales from hours to years can reduce long-term peat accumulation. Our mathematical and numerical models can be used to predict long-term effects of changes in temporal rainfall patterns and drainage networks on tropical peatland geomorphology and carbon storage.

How temporal patterns in rainfall determine the geomorphology and carbon fluxes of tropical peatlands

PubMed Central

Hoyt, Alison M.; Gandois, Laure; Eri, Jangarun; Dommain, René; Abu Salim, Kamariah; Kai, Fuu Ming; Haji Su’ut, Nur Salihah; Harvey, Charles F.

2017-01-01

Tropical peatlands now emit hundreds of megatons of carbon dioxide per year because of human disruption of the feedbacks that link peat accumulation and groundwater hydrology. However, no quantitative theory has existed for how patterns of carbon storage and release accompanying growth and subsidence of tropical peatlands are affected by climate and disturbance. Using comprehensive data from a pristine peatland in Brunei Darussalam, we show how rainfall and groundwater flow determine a shape parameter (the Laplacian of the peat surface elevation) that specifies, under a given rainfall regime, the ultimate, stable morphology, and hence carbon storage, of a tropical peatland within a network of rivers or canals. We find that peatlands reach their ultimate shape first at the edges of peat domes where they are bounded by rivers, so that the rate of carbon uptake accompanying their growth is proportional to the area of the still-growing dome interior. We use this model to study how tropical peatland carbon storage and fluxes are controlled by changes in climate, sea level, and drainage networks. We find that fluctuations in net precipitation on timescales from hours to years can reduce long-term peat accumulation. Our mathematical and numerical models can be used to predict long-term effects of changes in temporal rainfall patterns and drainage networks on tropical peatland geomorphology and carbon storage. PMID:28607068

Computation of groundwater resources and recharge in Chithar River Basin, South India.

PubMed

Subramani, T; Babu, Savithri; Elango, L

2013-01-01

Groundwater recharge and available groundwater resources in Chithar River basin, Tamil Nadu, India spread over an area of 1,722 km(2) have been estimated by considering various hydrological, geological, and hydrogeological parameters, such as rainfall infiltration, drainage, geomorphic units, land use, rock types, depth of weathered and fractured zones, nature of soil, water level fluctuation, saturated thickness of aquifer, and groundwater abstraction. The digital ground elevation models indicate that the regional slope of the basin is towards east. The Proterozoic (Post-Archaean) basement of the study area consists of quartzite, calc-granulite, crystalline limestone, charnockite, and biotite gneiss with or without garnet. Three major soil types were identified namely, black cotton, deep red, and red sandy soils. The rainfall intensity gradually decreases from west to east. Groundwater occurs under water table conditions in the weathered zone and fluctuates between 0 and 25 m. The water table gains maximum during January after northeast monsoon and attains low during October. Groundwater abstraction for domestic/stock and irrigational needs in Chithar River basin has been estimated as 148.84 MCM (million m(3)). Groundwater recharge due to monsoon rainfall infiltration has been estimated as 170.05 MCM based on the water level rise during monsoon period. It is also estimated as 173.9 MCM using rainfall infiltration factor. An amount of 53.8 MCM of water is contributed to groundwater from surface water bodies. Recharge of groundwater due to return flow from irrigation has been computed as 147.6 MCM. The static groundwater reserve in Chithar River basin is estimated as 466.66 MCM and the dynamic reserve is about 187.7 MCM. In the present scenario, the aquifer is under safe condition for extraction of groundwater for domestic and irrigation purposes. If the existing water bodies are maintained properly, the extraction rate can be increased in future about 10% to 15%.

Land Use Change Impacts to Flows and Hydropower at the Southern Fringe of the Brazilian Amazon: A Regional, Empirical Study of Land-Water-Energy Nexus Dynamics

NASA Astrophysics Data System (ADS)

Levy, M. C.; Thompson, S. E.; Cohn, A.

2014-12-01

Land use/cover change (LUCC) has occurred extensively in the Brazilian Amazon rainforest-savanna transition. Agricultural development-driven LUCC at regional scales can alter surface energy budgets, evapotranspiration (ET) and rainfall; these hydroclimatic changes impact streamflows, and thus hydropower. To date, there is only limited empirical understanding of these complex land-water-energy nexus dynamics, yet understanding is important to developing countries where both agriculture and hydropower are expanding and intensifying. To observe these changes and their interconnections, we synthesize a novel combination of ground network, remotely sensed, and empirically modeled data for LUCC, rainfall, flows, and hydropower potential. We connect the extensive temporal and spatial trends in LUCC occurring from 2000-2012 (and thus observable in the satellite record) to long-term historical flow records and run-of-river hydropower generation potential estimates. Changes in hydrologic condition are observed in terms of dry and wet season moments, extremes, and flow duration curves. Run-of-river hydropower generation potential is modeled at basin gauge points using equation models parameterized with literature-based low-head turbine efficiencies, and simple algorithms establishing optimal head and capacity from elevation and flows, respectively. Regression analyses are used to demonstrate a preliminary causal analysis of LUCC impacts to flow and energy, and discuss extension of the analysis to ungauged basins. The results are transferable to tropical and transitional forest regions worldwide where simultaneous agricultural and hydropower development potentially compete for coupled components of regional water cycles, and where policy makers and planners require an understanding of LUCC impacts to hydroclimate-dependent industries and ecosystems.

Hydrological simulation of Sperchios River basin in Central Greece using the MIKE SHE model and geographic information systems

NASA Astrophysics Data System (ADS)

Paparrizos, Spyridon; Maris, Fotios

2017-05-01

The MIKE SHE model is able to simulate the entire stream flow which includes direct and basic flow. Many models either do not simulate or use simplistic methods to determine the basic flow. The MIKE SHE model takes into account many hydrological data. Since this study was directed towards the simulation of surface runoff and infiltration into saturated and unsaturated zone, the MIKE SHE is an appropriate model for reliable conclusions. In the current research, the MIKE SHE model was used to simulate runoff in the area of Sperchios River basin. Meteorological data from eight rainfall stations within the Sperchios River basin were used as inputs. Vegetation as well as geological data was used to perform the calibration and validation of the physical processes of the model. Additionally, ArcGIS program was used. The results indicated that the model was able to simulate the surface runoff satisfactorily, representing all the hydrological data adequately. Some minor differentiations appeared which can be eliminated with the appropriate adjustments that can be decided by the researcher's experience.

Estimated probability of postwildfire debris flows in the 2012 Whitewater-Baldy Fire burn area, southwestern New Mexico

USGS Publications Warehouse

Tillery, Anne C.; Matherne, Anne Marie; Verdin, Kristine L.

2012-01-01

In May and June 2012, the Whitewater-Baldy Fire burned approximately 1,200 square kilometers (300,000 acres) of the Gila National Forest, in southwestern New Mexico. The burned landscape is now at risk of damage from postwildfire erosion, such as that caused by debris flows and flash floods. This report presents a preliminary hazard assessment of the debris-flow potential from 128 basins burned by the Whitewater-Baldy Fire. A pair of empirical hazard-assessment models developed by using data from recently burned basins throughout the intermountain Western United States was used to estimate the probability of debris-flow occurrence and volume of debris flows along the burned area drainage network and for selected drainage basins within the burned area. The models incorporate measures of areal burned extent and severity, topography, soils, and storm rainfall intensity to estimate the probability and volume of debris flows following the fire. In response to the 2-year-recurrence, 30-minute-duration rainfall, modeling indicated that four basins have high probabilities of debris-flow occurrence (greater than or equal to 80 percent). For the 10-year-recurrence, 30-minute-duration rainfall, an additional 14 basins are included, and for the 25-year-recurrence, 30-minute-duration rainfall, an additional eight basins, 20 percent of the total, have high probabilities of debris-flow occurrence. In addition, probability analysis along the stream segments can identify specific reaches of greatest concern for debris flows within a basin. Basins with a high probability of debris-flow occurrence were concentrated in the west and central parts of the burned area, including tributaries to Whitewater Creek, Mineral Creek, and Willow Creek. Estimated debris-flow volumes ranged from about 3,000-4,000 cubic meters (m3) to greater than 500,000 m3 for all design storms modeled. Drainage basins with estimated volumes greater than 500,000 m3 included tributaries to Whitewater Creek, Willow Creek, Iron Creek, and West Fork Mogollon Creek. Drainage basins with estimated debris-flow volumes greater than 100,000 m3 for the 25-year-recurrence event, 24 percent of the basins modeled, also include tributaries to Deep Creek, Mineral Creek, Gilita Creek, West Fork Gila River, Mogollon Creek, and Turkey Creek, among others. Basins with the highest combined probability and volume relative hazard rankings for the 25-year-recurrence rainfall include tributaries to Whitewater Creek, Mineral Creek, Willow Creek, West Fork Gila River, West Fork Mogollon Creek, and Turkey Creek. Debris flows from Whitewater, Mineral, and Willow Creeks could affect the southwestern New Mexico communities of Glenwood, Alma, and Willow Creek. The maps presented herein may be used to prioritize areas where emergency erosion mitigation or other protective measures may be necessary within a 2- to 3-year period of vulnerability following the Whitewater-Baldy Fire. This work is preliminary and is subject to revision. It is being provided because of the need for timely "best science" information. The assessment herein is provided on the condition that neither the U.S. Geological Survey nor the U.S. Government may be held liable for any damages resulting from the authorized or unauthorized use of the assessment.

Experimental study of water fluxes in a residential area: 2. Road infiltration, runoff and evaporation

NASA Astrophysics Data System (ADS)

Ragab, R.; Rosier, P.; Dixon, A.; Bromley, J.; Cooper, J. D.

2003-08-01

Lack of accurate data has led some hydrologists and city planners to assume that urban infiltration is zero and runoff is 100% of the rainfall. These assumptions lead to an over estimation of road runoff volume and an underestimation of direct recharge to groundwater, which is already rising under some UK cities. This study investigates infiltration and runoff processes and quantifies the percentage of rainfall that contributes to storm drainage, and that which infiltrates through different types of road surface. Access tubes were installed for measuring soil water content using a neutron probe in three car parks, a road and a grass site at the Centre for Ecology and Hydrology, Crowmarsh Gifford, Wallingford. Storm drainage was recorded at the exit of the Thamesmead Estate in Crowmarsh Gifford, just before the drain joins the River Thames at Wallingford. Rainfall and water table depth were also recorded. Weekly measurements of soil moisture content indicated that the top 40 cm layer is not influenced by water-table fluctuations and, therefore, positive changes in soil moisture could be attributed to infiltration of rainfall through the surface. Depending on the nature of the surface, subsurface layers, level of traffic, etc., between 6 and 9% of rainfall was found to infiltrate through the road surfaces studied. The storm drainage generated by road runoff revealed a flow pattern similar to that of the receiving watercourse (River Thames) and increased with the increase of infiltration and soil water content below the road surface. The ratio of runoff to rainfall was 0·7, 0·9 and 0·5 for annual, winter (October-March) and summer (April-September) respectively. As the results of the infiltration indicated that 6 to 9% of annual rainfall infiltrates through the road surface, this means that evaporation represents, 21-24% of annual rainfall, with more evaporation taking place during summer than winter.

Dynamic Water Storage during Flash Flood Events in the Mountainous Area of Rio de Janeiro/Brazil - Case study: Piabanha River Basin

NASA Astrophysics Data System (ADS)

Araujo, L.; Silva, F. P. D.; Moreira, D. M.; Vásquez P, I. L.; Justi da Silva, M. G. A.; Fernandes, N.; Rotunno Filho, O. C.

2017-12-01

Flash floods are characterized by a rapid rise in water levels, high flow rates and large amounts of debris. Several factors have relevance to the occurrence of these phenomena, including high precipitation rates, terrain slope, soil saturation degree, vegetation cover, soil type, among others. In general, the greater the precipitation intensity, the more likely is the occurrence of a significant increase in flow rate. Particularly on steep and rocky plains or heavily urbanized areas, relatively small rain rates can trigger a flash flood event. In addition, high rain rates in short time intervals can temporarily saturate the surface soil layer acting as waterproofing and favoring the occurrence of greater runoff rates due to non-infiltration of rainwater into the soil. Thus, although precipitation is considered the most important factor for flooding, the interaction between rainfall and the soil can sometimes be of greater importance. In this context, this work investigates the dynamic storage of water associated with flash flood events for Quitandinha river watershed, a tributary of Piabanha river, occurred between 2013 and 2014, by means of water balance analyses applied to three watersheds of varying magnitudes (9.25 km², 260 km² and 429 km²) along the rainy season under different time steps (hourly and daily) using remotely sensed and observational precipitation data. The research work is driven by the hypothesis of a hydrologically active bedrock layer, as the watershed is located in a humid region, having intemperate (fractured) rock layer, just below a shallow soil layer, in the higher part of the basin where steep slopes prevail. The results showed a delay of the variation of the dynamic storage in relation to rainfall peaks and water levels. Such behavior indicates that the surface soil layer, which is not very thick in the region, becomes rapidly saturated along rainfall events. Subsequently, the water infiltrates into the rocky layer and the water storage in the fractured bedrock assumes significant role due to its corresponding release to streams as storm flows.

Radar-driven High-resolution Hydrometeorological Forecasts of the 26 September 2007 Venice flash flood

NASA Astrophysics Data System (ADS)

Massimo Rossa, Andrea; Laudanna Del Guerra, Franco; Borga, Marco; Zanon, Francesco; Settin, Tommaso; Leuenberger, Daniel

2010-05-01

Space and time scales of flash floods are such that flash flood forecasting and warning systems depend upon the accurate real-time provision of rainfall information, high-resolution numerical weather prediction (NWP) forecasts and the use of hydrological models. Currently available high-resolution NWP model models can potentially provide warning forecasters information on the future evolution of storms and their internal structure, thereby increasing convective-scale warning lead times. However, it is essential that the model be started with a very accurate representation of on-going convection, which calls for assimilation of high-resolution rainfall data. This study aims to assess the feasibility of using carefully checked radar-derived quantitative precipitation estimates (QPE) for assimilation into NWP and hydrological models. The hydrometeorological modeling chain includes the convection-permitting NWP model COSMO-2 and a hydrologic-hydraulic models built upon the concept of geomorphological transport. Radar rainfall observations are assimilated into the NWP model via the latent heat nudging method. The study is focused on 26 September 2007 extreme flash flood event which impacted the coastal area of north-eastern Italy around Venice. The hydro-meteorological modeling system is implemented over the Dese river, a 90 km2 catchment flowing to the Venice lagoon. The radar rainfall observations are carefully checked for artifacts, including beam attenuation, by means of physics-based correction procedures and comparison with a dense network of raingauges. The impact of the radar QPE in the assimilation cycle of the NWP model is very significant, in that the main individual organized convective systems were successfully introduced into the model state, both in terms of timing and localization. Also, incorrectly localized precipitation in the model reference run without rainfall assimilation was correctly reduced to about the observed levels. On the other hand, the highest rainfall intensities were underestimated by 20% at a scale of 1000 km2, and the local peaks by 50%. The positive impact of the assimilated radar rainfall was carried over into the free forecast for about 2-5 hours, depending on when this forecast was started, and was larger, when the main mesoscale convective system was present in the initial conditions. The improvements of the meteorological model simulations were directly propagated to the river flow simulations, with an extension of the warning lead time up to three hours.

Detecting Human Hydrologic Alteration from Diversion Hydropower Requires Universal Flow Prediction Tools: A Proposed Framework for Flow Prediction in Poorly-gauged, Regulated Rivers

NASA Astrophysics Data System (ADS)

Kibler, K. M.; Alipour, M.

2016-12-01

Achieving the universal energy access Sustainable Development Goal will require great investment in renewable energy infrastructure in the developing world. Much growth in the renewable sector will come from new hydropower projects, including small and diversion hydropower in remote and mountainous regions. Yet, human impacts to hydrological systems from diversion hydropower are poorly described. Diversion hydropower is often implemented in ungauged rivers, thus detection of impact requires flow analysis tools suited to prediction in poorly-gauged and human-altered catchments. We conduct a comprehensive analysis of hydrologic alteration in 32 rivers developed with diversion hydropower in southwestern China. As flow data are sparse, we devise an approach for estimating streamflow during pre- and post-development periods, drawing upon a decade of research into prediction in ungauged basins. We apply a rainfall-runoff model, parameterized and forced exclusively with global-scale data, in hydrologically-similar gauged and ungauged catchments. Uncertain "soft" data are incorporated through fuzzy numbers and confidence-based weighting, and a multi-criteria objective function is applied to evaluate model performance. Testing indicates that the proposed framework returns superior performance (NSE = 0.77) as compared to models parameterized by rote calibration (NSE = 0.62). Confident that the models are providing `the right answer for the right reasons', our analysis of hydrologic alteration based on simulated flows indicates statistically significant hydrologic effects of diversion hydropower across many rivers. Mean annual flows, 7-day minimum and 7-day maximum flows decreased. Frequency and duration of flow exceeding Q25 decreased while duration of flows sustained below the Q75 increased substantially. Hydrograph rise and fall rates and flow constancy increased. The proposed methodology may be applied to improve diversion hydropower design in data-limited regions.

Radar-driven high-resolution hydro-meteorological forecasts of the 26 September 2007 Venice flash flood

NASA Astrophysics Data System (ADS)

Rossa, Andrea M.; Laudanna Del Guerra, Franco; Borga, Marco; Zanon, Francesco; Settin, Tommaso; Leuenberger, Daniel

2010-11-01

SummaryThis study aims to assess the feasibility of assimilating carefully checked radar rainfall estimates into a numerical weather prediction (NWP) to extend the forecasting lead time for an extreme flash flood. The hydro-meteorological modeling chain includes the convection-permitting NWP model COSMO-2 and a coupled hydrological-hydraulic model. Radar rainfall estimates are assimilated into the NWP model via the latent heat nudging method. The study is focused on 26 September 2007 extreme flash flood which impacted the coastal area of North-eastern Italy around Venice. The hydro-meteorological modeling system is implemented over the 90 km2 Dese river basin draining to the Venice Lagoon. The radar rainfall observations are carefully checked for artifacts, including rain-induced signal attenuation, by means of physics-based correction procedures and comparison with a dense network of raingauges. The impact of the radar rainfall estimates in the assimilation cycle of the NWP model is very significant. The main individual organized convective systems are successfully introduced into the model state, both in terms of timing and localization. Also, high-intensity incorrectly localized precipitation is correctly reduced to about the observed levels. On the other hand, the highest rainfall intensities computed after assimilation underestimate the observed values by 20% and 50% at a scale of 20 km and 5 km, respectively. The positive impact of assimilating radar rainfall estimates is carried over into the free forecast for about 2-5 h, depending on when the forecast was started. The positive impact is larger when the main mesoscale convective system is present in the initial conditions. The improvements in the precipitation forecasts are propagated to the river flow simulations, with an extension of the forecasting lead time up to 3 h.

Modelling landscape evolution at the flume scale

NASA Astrophysics Data System (ADS)

Cheraghi, Mohsen; Rinaldo, Andrea; Sander, Graham C.; Barry, D. Andrew

2017-04-01

The ability of a large-scale Landscape Evolution Model (LEM) to simulate the soil surface morphological evolution as observed in a laboratory flume (1-m × 2-m surface area) was investigated. The soil surface was initially smooth, and was subjected to heterogeneous rainfall in an experiment designed to avoid rill formation. Low-cohesive fine sand was placed in the flume while the slope and relief height were 5 % and 20 cm, respectively. Non-uniform rainfall with an average intensity of 85 mm h-1 and a standard deviation of 26 % was applied to the sediment surface for 16 h. We hypothesized that the complex overland water flow can be represented by a drainage discharge network, which was calculated via the micro-morphology and the rainfall distribution. Measurements included high resolution Digital Elevation Models that were captured at intervals during the experiment. The calibrated LEM captured the migration of the main flow path from the low precipitation area into the high precipitation area. Furthermore, both model and experiment showed a steep transition zone in soil elevation that moved upstream during the experiment. We conclude that the LEM is applicable under non-uniform rainfall and in the absence of surface incisions, thereby extending its applicability beyond that shown in previous applications. Keywords: Numerical simulation, Flume experiment, Particle Swarm Optimization, Sediment transport, River network evolution model.

Future Proofing Water Policy and Catchment Management for a Changing Climate: A Case Study of Competing Demands and Water Scarcity in the River Thames and Catchment

NASA Astrophysics Data System (ADS)

Whitehead, P. G.; Crossman, J.; Jin, L.

2011-12-01

The River Thames Catchment is the major water supply system in Southern England and supplies all of London's water supply from either the River Lee (a tributary of the Thames) or the main river abstraction site at Teddington (see Figure 1) or from groundwater sources in London. There has been a measurable change in rainfall patterns over the past 250 years with reducing summer rainfall and, hence flows, over the past 40 years. In 1976, following 3 dry winters, the London Reservoirs were more or less empty and the river flow direction was reversed to ensure a supply of water for London. Recent climate change studies in the Thames catchments suggest an increasing threat to water supply and also damage to river water quality and ecology. In addition to a changing climate, population levels in London have risen in recent years and the catchment is increasingly vulnerable to land use change. Since the 1920s changes in land use have increased the levels of nitrogen and phosphorus in the catchment and this trend is predicted to be exacerbated as climate change reduces freshwater dilution. Also land use is predicted to change as agriculture becomes more intensive as farmers react to higher grain and food prices. At the same time rising water temperatures has exposed the river to the potential for toxic algal blooms, such as cyanobacteria. This doom and gloom story is being managed however using a range of policy instruments, led by central government and public and private organisations such as Thames Water and the Environment Agency. Measures such as new reservoirs, a water transfer scheme from Wales and water metering to reduce demand are all being actively pursued, as are land management measures to control diffuse pollution. In order to assess the effects of climate change on the Thames catchment a major modelling study has been undertaken. The Integrated Catchment Model (INCA) has been set up for the Thames to model flow, nitrogen, phosphorus and ecology. Climate Change simulations predict reduced flow regimes in the river system and changes to the nitrogen patterns. Nitrate is predicted to reduce in summer, due to the lower flows which generate longer water residence times and hence allow more time for denitrification processes to occur. Phosphorus levels increase, however, due to the reduced dilution of effluents with subsequent detrimental effects on ecology. The model has been used to evaluate alternative water management policies such as a new reservoir for London, the transfer of water from the River Severn into the Thames, the reduction in P discharges from Sewage Treatment Works and the control of diffuse runoff by improved land management. Thus using the models to evaluate alternative strategies is very positive contribution to policy and planning.

Satellite-based Flood Modeling Using TRMM-based Rainfall Products.

PubMed

Harris, Amanda; Rahman, Sayma; Hossain, Faisal; Yarborough, Lance; Bagtzoglou, Amvrossios C; Easson, Greg

2007-12-20

Increasingly available and a virtually uninterrupted supply of satellite-estimatedrainfall data is gradually becoming a cost-effective source of input for flood predictionunder a variety of circumstances. However, most real-time and quasi-global satelliterainfall products are currently available at spatial scales ranging from 0.25 o to 0.50 o andhence, are considered somewhat coarse for dynamic hydrologic modeling of basin-scaleflood events. This study assesses the question: what are the hydrologic implications ofuncertainty of satellite rainfall data at the coarse scale? We investigated this question onthe 970 km² Upper Cumberland river basin of Kentucky. The satellite rainfall productassessed was NASA's Tropical Rainfall Measuring Mission (TRMM) Multi-satellitePrecipitation Analysis (TMPA) product called 3B41RT that is available in pseudo real timewith a latency of 6-10 hours. We observed that bias adjustment of satellite rainfall data canimprove application in flood prediction to some extent with the trade-off of more falsealarms in peak flow. However, a more rational and regime-based adjustment procedureneeds to be identified before the use of satellite data can be institutionalized among floodmodelers.

Precipitation Effects on Microbial Pollution in a River: Lag Structures and Seasonal Effect Modification

PubMed Central

Tornevi, Andreas; Bergstedt, Olof; Forsberg, Bertil

2014-01-01

Background The river Göta Älv is a source of freshwater for 0.7 million swedes. The river is subject to contamination from sewer systems discharge and runoff from agricultural lands. Climate models projects an increase in precipitation and heavy rainfall in this region. This study aimed to determine how daily rainfall causes variation in indicators of pathogen loads, to increase knowledge of variations in river water quality and discuss implications for risk management. Methods Data covering 7 years of daily monitoring of river water turbidity and concentrations of E. coli, Clostridium and coliforms were obtained, and their short-term variations in relation with precipitation were analyzed with time series regression and non-linear distributed lag models. We studied how precipitation effects varied with season and compared different weather stations for predictive ability. Results Generally, the lowest raw water quality occurs 2 days after rainfall, with poor raw water quality continuing for several more days. A rainfall event of >15 mm/24-h (local 95 percentile) was associated with a three-fold higher concentration of E. coli and 30% higher turbidity levels (lag 2). Rainfall was associated with exponential increases in concentrations of indicator bacteria while the effect on turbidity attenuated with very heavy rainfall. Clear associations were also observed between consecutive days of wet weather and decreased water quality. The precipitation effect on increased levels of indicator bacteria was significant in all seasons. Conclusions Rainfall elevates microbial risks year-round in this river and freshwater source and acts as the main driver of varying water quality. Heavy rainfall appears to be a better predictor of fecal pollution than water turbidity. An increase of wet weather and extreme events with climate change will lower river water quality even more, indicating greater challenges for drinking water producers, and suggesting better control of sources of pollution. PMID:24874010

Explore the Impacts of River Flow and Water Quality on Fish Communities

NASA Astrophysics Data System (ADS)

Tsai, W. P.; Chang, F. J.; Lin, C. Y.; Hu, J. H.; Yu, C. J.; Chu, T. J.

2015-12-01

Owing to the limitation of geographical environment in Taiwan, the uneven temporal and spatial distribution of rainfall would cause significant impacts on river ecosystems. To pursue sustainable water resources development, integrity and rationality is important to water management planning. The water quality and the flow regimes of rivers are closely related to each other and affect river ecosystems simultaneously. Therefore, this study collects long-term observational heterogeneity data, which includes water quality parameters, stream flow and fish species in the Danshui River of norther Taiwan, and aims to explore the complex impacts of water quality and flow regime on fish communities in order to comprehend the situations of the eco-hydrological system in this river basin. First, this study improves the understanding of the relationship between water quality parameters, flow regime and fish species by using artificial neural networks (ANNs). The Self-organizing feature map (SOM) is an unsupervised learning process used to cluster, analyze and visualize a large number of data. The results of SOM show that nine clusters (3x3) forms the optimum map size based on the local minimum values of both quantization error (QE) and topographic error (TE). Second, the fish diversity indexes are estimated by using the Adapted network-based fuzzy inference system (ANFIS) based on key input factors determined by the Gamma Test (GT), which is a useful tool for reducing model dimension and the structure complexity of ANNs. The result reveals that the constructed models can effectively estimate fish diversity indexes and produce good estimation performance based on the 9 clusters identified by the SOM, in which RMSE is 0.18 and CE is 0.84 for the training data set while RMSE is 0.20 and CE is 0.80 for the testing data set.

Flood Pulse Influence on Export of Terrestrial Organic Matter

NASA Astrophysics Data System (ADS)

Dalzell, B. J.; Harbor, J. M.; Filley, T. R.

2004-12-01

While much attention has been placed on characterizing Terrestrial Organic Matter (TOM) export from large rivers, recent research has shown that in-stream processing of TOM in smaller streams and rivers over shorter time scales can be an important upland component of regional carbon budgets not detected at the outlets of large rivers. With predictions of climate change accompanied by more intense rainfall patterns in some areas, it is important to understand the linkage between flood events and watershed export of TOM. To this end, we have collected water samples from Big Pine Creek watershed, an 850km2 watershed located in west central Indiana. Organic carbon in dissolved, colloidal, and particulate size fractions has been described with molecular and stable carbon isotope techniques to track source, quantity, and compositional changes of TOM over changing flow conditions. Results from these samples show that flood conditions export dramatically more TOM; not only from increases in discharge, but also from increases in concentration of terrestrial organic carbon to all size fractions. While molecular biomarkers show increases in terrestrial organic matter, bulk stable carbon isotope values show that the sources of TOM do not remain constant. Rather, relative contributions from C4 plants (corn in this study area) increase during flood conditions by up to 40 percent. Finally, increases in rainfall intensity are likely to disproportionately increase organic carbon export from terrestrial systems, especially from smaller watersheds where short duration and high intensity flow events dominate annual discharge.

Population and osmoregulatory responses of a euryhaline fish to extreme salinity fluctuations in coastal lagoons of the Coorong, Australia

NASA Astrophysics Data System (ADS)

Wedderburn, Scotte D.; Bailey, Colin P.; Delean, Steven; Paton, David C.

2016-01-01

River flows and salinity are key factors structuring fish assemblages in estuaries. The osmoregulatory ability of a fish determines its capacity to tolerate rising salt levels when dispersal is unfeasible. Estuarine fishes can tolerate minor fluctuations in salinity, but a relatively small number of species in a few families can inhabit extreme hypersaline waters. The Murray-Darling Basin drains an extensive area of south-eastern Australia and river flows end at the mouth of the River Murray. The system is characterized by erratic rainfall and highly variable flows which have been reduced by intensive river regulation and water extraction. The Coorong is a coastal lagoon system extending some 110 km south-eastwards from the mouth. It is an inverted estuary with a salinity gradient that typically ranges from estuarine to triple that of sea water. Hypersalinity in the southern region suits a select suite of biota, including the smallmouth hardyhead Atherinosoma microstoma - a small-bodied, euryhaline fish with an annual life cycle. The population response of A. microstoma in the Coorong was examined during a period of considerable hydrological variation and extreme salinity fluctuations (2001-2014), and the findings were related to its osmoregulatory ability. Most notably, the species was extirpated from over 50% of its range during four continuous years without river flows when salinities exceeded 120 (2007-2010). These salinities exceeded the osmoregulatory ability of A. microstoma. Substantial river flows that reached the Coorong in late 2010 and continued into 2011 led salinities to fall below 100 throughout the Coorong by January 2012. Subsequently, A. microstoma recovered to its former range by January 2012. The findings show that the consequences of prolonged periods of insufficient river flows to temperate inverted estuaries will include substantial declines in the range of highly euryhaline fishes, which also may have wider ecological consequences.

Run-off regime of the small rivers in mountain landscapes (on an example of the mountain "Mongun-taiga

NASA Astrophysics Data System (ADS)

Pryahina, G.; Zelepukina, E.; Guzel, N.

2012-04-01

Hydrological characteristics calculations of the small mountain rivers in the basins with glaciers frequently cause complexity in connection with absence of standard hydrological supervision within remote mountain territories. The unique way of the actual information reception on a water mode of such rivers is field work. The rivers of the mountain Mongun-taiga located on a joint of Altai and Sayan mountains became hydrological researches objects of Russian geographical society complex expeditions in 2010-2011. The Mongun-taiga cluster of international biosphere reserve "Ubsunurskaya hollow" causes heightened interest of researchers — geographers for many years. The original landscape map in scale 1:100000 has been made, hydrological supervision on the rivers East Mugur and ugur, belonging inland basin of Internal Asia are lead. Supervision over the river drain East Mugur runoff were spent in profile of glacier tongue (the freezing area - 22 % (3.2 km2) from the reception basin) and in the closing alignment of the river located on distance of 3,4 km below tongue of glacier. During researches following results have been received. During the ablation period diurnal fluctuations with a strongly shown maximum and minimum of water discharges are typically for the small rivers with considerable share of a glacial food. The run-off maximum from the glacier takes place from 2 to 7 p.m., the run-off minimum is observed early in the morning. High speed of thawed snow running-off from glacier tongue and rather small volume of dynamic stocks water on an ice surface lead to growth of water discharge. In the bottom profile the time of maximum and minimum of water discharge is displaced on the average 2 hours, it depends of the water travel time. Maximum glacial run-off discharge (1.12 m3/s) in the upper profile was registered on July 16 (it was not rain). Volumes of daily runoff in the upper and bottom profiles were 60700-67600 m3 that day. The run-off from nonglacial part of the basin is formed by underground waters and melting snowfields, during the absence of rainfall period the part of one amounted to 10% of the run-off in the lower profile. We suggest that this water discharge corresponds to base flow value in the lower profile because the area of snowfields of the basin was < 0.1 km2 that year. Run-off monitoring has showed that rivers with a small glacial food are characterized by absence of diurnal balance of runoff. During rainfall the water content of river has being increased due to substantial derivation of basin and, as a result, fast flowing rain water into bed of river. The sharp decrease in water content of river during periods of rainfall absence indicates low inventory of soil and groundwater and the low rate of glacial. Thus, glaciers and character of the relief influence the formation of run-off small mountain rivers. Results of researches will be used for mathematical modeling mountain rivers run-off.

Examining the spatial and temporal variation of groundwater inflows to a valley-to-floodplain river using 222Rn, geochemistry and river discharge: the Ovens River, southeast Australia

NASA Astrophysics Data System (ADS)

Yu, M. C. L.; Cartwright, I.; Braden, J. L.; de Bree, S. T.

2013-12-01

Radon (222Rn) and major ion geochemistry were used to define and quantify the catchment-scale groundwater-surface water interactions along the Ovens River in the southeast Murray-Darling Basin, Victoria, Australia, between September 2009 and October 2011. The Ovens River is characterized by the transition from a single channel within a mountain valley in the upper catchment to a multi-channel meandering river on flat alluvial plains in the lower catchment. Overall, the Ovens River is dominated by gaining reaches, receiving groundwater from both alluvial and basement aquifers. The distribution of gaining and losing reaches is governed by catchment morphology and lithology. In the upper catchment, rapid groundwater recharge through the permeable aquifers increases the water table. The rising water table, referred to as hydraulic loading, increases the hydraulic head gradient toward the river and hence causes high baseflow to the river during wet (high flow) periods. In the lower catchment, lower rainfall and finer-gained sediments reduce the magnitude and variability of hydraulic gradient between the aquifer and the river, producing lower but more constant groundwater inflows. The water table in the lower reaches has a shallow gradient, and small changes in river height or groundwater level can result in fluctuating gaining and losing behaviour. The middle catchment represents a transition in river-aquifer interactions from the upper to the lower catchment. High baseflow in some parts of the middle and lower catchments is caused by groundwater flowing over basement highs. Mass balance calculations based on 222Rn activities indicate that groundwater inflows are 2 to 17% of total flow with higher inflows occurring during high flow periods. In comparison to 222Rn activities, estimates of groundwater inflows from Cl concentrations are higher by up to 2000% in the upper and middle catchment but lower by 50 to 100% in the lower catchment. The high baseflow estimates using Cl concentrations may be due to the lack of sufficient difference between groundwater and surface water Cl concentrations. Both hydrograph separation and differential flow gauging yield far higher baseflow fluxes than 222Rn activities and Cl concentrations, probably indicating the input of other sources to the river in additional to regional groundwater, such as bank return flows.

Transient Flow through an Unsaturated Levee Embankment during the 2011 Mississippi River Flood

NASA Astrophysics Data System (ADS)

Jafari, N.; Stark, T.; Vahedifard, F.; Cadigan, J.

2017-12-01

The Mississippi River and corresponding tributaries drain approximately 3.23 million km2 (1.25 million mi2) or the equivalent of 41% of the contiguous United States. Approximately 2,600 km ( 1,600 miles) of earthen levees presently protect major urban cities and agricultural land against the periodic Mississippi River floods within the Lower Mississippi River Valley. The 2011 flood also severely stressed the levees and highlighted the need to evaluate the behavior of levee embankments during high water levels. The performance of earthen levees is complex because of the uncertainties in construction materials, antecedent moisture contents, hydraulic properties, and lack of field monitoring. In particular, calibration of unsaturated and saturated soil properties of levee embankment and foundation layers along with the evaluation of phreatic surface during high river stage is lacking. Due to the formation of sand boils at the Duncan Point Levee in Baton Rouge, LA during the 2011 flood event, a reconnaissance survey was conducted to collect pore-water pressures in the sand foundation using piezometers and identifying the phreatic surface at the peak river level. Transient seepage analyses were performed to calibrate the foundation and levee embankment material properties using field data collected. With this calibrated levee model, numerical experiments were conducted to characterize the effects of rainfall intensity and duration, progression of phreatic surface, and seasonal climate variability prior to floods on the performance of the levee embankment. For example, elevated phreatic surface from river floods are maintained for several months and can be compounded with rainfall to lead to slope instability.

Quantifying downstream impacts of impoundment on flow regime and channel planform, lower Trinity River, Texas

NASA Astrophysics Data System (ADS)

Wellmeyer, Jessica L.; Slattery, Michael C.; Phillips, Jonathan D.

2005-07-01

As human population worldwide has grown, so has interest in harnessing and manipulating the flow of water for the benefit of humans. The Trinity River of eastern Texas is one such watershed greatly impacted by engineering and urbanization. Draining the Dallas-Fort Worth metroplex, just under 30 reservoirs are in operation in the basin, regulating flow while containing public supplies, supporting recreation, and providing flood control. Lake Livingston is the lowest, as well as largest, reservoir in the basin, a mere 95 km above the Trinity's outlet near Galveston Bay. This study seeks to describe and quantify channel activity and flow regime, identifying effects of the 1968 closure of Livingston dam. Using historic daily and peak discharge data from USGS gauging stations, flow duration curves are constructed, identifying pre- and post-dam flow conditions. A digital historic photo archive was also constructed using six sets of aerial photographs spanning from 1938 to 1995, and three measures of channel activity applied using a GIS. Results show no changes in high flow conditions following impoundment, while low flows are elevated. However, the entire post-dam period is characterized by significantly higher rainfall, which may be obscuring the full impact of flow regulation. Channel activity rates do not indicate a more stabilized planform following dam closure; rather they suggest that the Trinity River is adjusting itself to the stress of Livingston dam in a slow, gradual process that may not be apparent in a modern time scale.

iss012e23057

NASA Image and Video Library

2006-03-02

ISS012-E-23057 (2 March 2006) --- Ekuma River and Etosha Pan, Namibia are featured in this close-up image photographed by an Expedition 12 crewmember on the International Space Station. Etosha Pan, northern Namibia, is a large (120 kilometers or 75 mile long) dry lakebed in the Kalahari Desert. The lake and surrounds are protected today as one of Namibia’s largest wildlife parks. Herds of elephant occupy the dense mopane woodland on the south side of the lake. Mopane trees are common throughout south-central Africa, and host the mopane worm (the larval form of the Mopane Emperor Moth)–an important source of protein for rural communities. According to scientists, about 16,000 years ago, when ice sheets were melting across Northern Hemisphere land masses, a wet climate phase in southern Africa filled Etosha Lake. Today, Etosha Pan is seldom seen with even a thin sheet of water covering the salt pan. This view shows the point where the Ekuma River flows into the salt lake. The Ekuma River is almost never seen with water, but in early 2006 rainfall twice the average amount in the river’s catchment generated flow. Greens and browns show vegetation and algae growing in different depths of water where the river enters the dry lake. Typically, little river water or sediment reaches the dry lake because water seeps into the riverbed along its 250 kilometers (155 miles) course, reducing discharge along the way. In this image, there was enough surface flow to reach the Pan, but too little water reached the mouth of the river to flow beyond the inlet bay. The unusual levels of precipitation also filled several small, usually dry lakes to the north of Etosha Pan.

Effects of rainfall patterns and land cover on the subsurface flow generation of sloping Ferralsols in southern China

PubMed Central

Yang, Jie; Tang, Chongjun; Chen, Lihua; Liu, Yaojun; Wang, Lingyun

2017-01-01

Rainfall patterns and land cover are two important factors that affect the runoff generation process. To determine the surface and subsurface flows associated with different rainfall patterns on sloping Ferralsols under different land cover types, observational data related to surface and subsurface flows from 5 m × 15 m plots were collected from 2010 to 2012. The experiment was conducted to assess three land cover types (grass, litter cover and bare land) in the Jiangxi Provincial Soil and Water Conservation Ecological Park. During the study period, 114 natural rainfall events produced subsurface flow and were divided into four groups using k-means clustering according to rainfall duration, rainfall depth and maximum 30-min rainfall intensity. The results showed that the total runoff and surface flow values were highest for bare land under all four rainfall patterns and lowest for the covered plots. However, covered plots generated higher subsurface flow values than bare land. Moreover, the surface and subsurface flows associated with the three land cover types differed significantly under different rainfall patterns. Rainfall patterns with low intensities and long durations created more subsurface flow in the grass and litter cover types, whereas rainfall patterns with high intensities and short durations resulted in greater surface flow over bare land. Rainfall pattern I had the highest surface and subsurface flow values for the grass cover and litter cover types. The highest surface flow value and lowest subsurface flow value for bare land occurred under rainfall pattern IV. Rainfall pattern II generated the highest subsurface flow value for bare land. Therefore, grass or litter cover are able to convert more surface flow into subsurface flow under different rainfall patterns. The rainfall patterns studied had greater effects on subsurface flow than on total runoff and surface flow for covered surfaces, as well as a greater effect on surface flows associated with bare land. PMID:28792507

Analysis of seasonal water pollution based on rainfall feature at Anyang river basin in Korea

NASA Astrophysics Data System (ADS)

Han, J. G.; Lee, Y. K.; Kim, T. H.; Hwang, E. J.

2005-08-01

To determine selected water pollution parameters of the Anyang River (one of the biggest contributory branches of the Han River in Korea) and its main tributaries, the geological and topographical and rainfall features in its basin were investigated, and the resulting data were tabulated. Samples were collected at the upper, mid and down parts of the Anyang River and its branches and were analyzed based on biochemical and chemical methods, Korean biotic index (KBI) and Saprobien systems. Selected parameters of concern include BOD, heavy metals, nonpoint pollution and sewage discharge. The Anyang River basin has a torrential heavy rainfall; however, the rate of rainfall significantly varies from season to season. Water pollution levels in the dry season increase dramatically. The mainstream of the Anyang River is classified as fifth grade polysaprobic water according to Saprobien system. In addition, the biotic index is over 2.5 in overall. General pollution at the junction of the Anyang River and each branch stream varies. Possible countermeasures to improve the water quality of the river include intercept the non-treated waste water and sewage at the Anyang River junction and each branch stream, enforcement of water management during the rainy season, and continuous investment on environmental restoration.

Spatiotemporal floodplain mapping and prediction using HEC-RAS - GIS tools: Case of the Mejerda river, Tunisia

NASA Astrophysics Data System (ADS)

Ben Khalfallah, C.; Saidi, S.

2018-06-01

The floods have become a scourge in recent years (Floods of, 2003, 2006, 2009, 2011, and 2012), increasingly frequent and devastating. Tunisia does not escape flooding problems, the flood management requires basically a better knowledge of the phenomenon (flood), and the use of predictive methods. In order to limit this risk, we became interested in hydrodynamics modeling of Medjerda basin. To reach this aim, rainfall distribution is studied and mapped using GIS tools. In addition, flood and return period estimation of rainfall are calculated using Hyfran. Also, Simulations of recent floods are calculated and mapped using HEC-RAS and HEC-GeoRAS for the most recent flood occurred in February-March 2015 in Medjerda basin. The analysis of the results shows a good correlation between simulated parameters and those measured. There is a flood of the river exceeding 240 m3/s (DGRE, 2015) and more flowing sections are observed in the future simulations; for return periods of 10yr, 20yr and 50yr.

Runoff and Leaching of Metolachlor from Mississippi River Alluvial Soil during Seasons of Average and Below-Average Rainfall

USDA-ARS?s Scientific Manuscript database

The movement of metolachlor via runoff and leaching from plots planted to corn on Mississippi River alluvial soil (Commerce silt loam) was measured for a six-year period, 1995-2000. The first three years were characterized by normal rainfall volume, the second three years by reduced rainfall. The ...

Acute sedimentation response to rainfall following the explosive phase of the 2008-2009 eruption of Chaitén volcano, Chile

USGS Publications Warehouse

Pierson, Thomas C.; Major, Jon J.; Amigo, Álvaro; Moreno, Hugo

2013-01-01

The 10-day explosive phase at the start of the 2008–2009 eruption of Chaitén volcano in southern Chile (42.83°S, 72.65°W) blanketed the steep, rain-forest-cloaked, 77-km2 Chaitén River drainage basin with 3 to >100 cm of tephra; predominantly fine to extremely fine rhyolitic ash fell during the latter half of the explosive phase. Rain falling on this ash blanket within days of cessation of major explosive activity generated a hyperconcentrated-flow lahar, followed closely by a complex, multi-day, muddy flood (streamflow bordering on dilute hyperconcentrated flow). Sediment mobilized in this lahar-flood event filled the Chaitén River channel with up to 7 m of sediment, buried the town of Chaitén (10 km downstream of the volcano) in up to 3 m of sediment, and caused the lower 3 km of the channel to avulse through the town. Although neither the nature nor rate of the sedimentation response is unprecedented, they are unusual in several ways: (1) Nearly 70 percent of the aggradation (almost 5 m) in the 50–70-m-wide Chaitén River channel was caused by a lahar, triggered by an estimated 20 mm of rainfall over a span of about 24 h. An additional 2 m of aggradation occurred in the next 24–36 h. (2) Direct damage to the town was accomplished by the sediment-laden water-flood phase of the lahar-flood event, not the lahar phase. (3) The volume of sediment eroded from hillslopes and delivered to the Chaitén River channel was at least 3–8 × 106 m3—roughly 15–40 % of the minimum tephra volume that mantled the Chaitén River drainage basin. (4) The acute sedimentation response to rainfall appears to have been due to the thickness and fineness of the ash blanket (inhibiting infiltration of rain) and the steepness of the basin’s hillslopes. Other possible factors such as the prior formation of an ash crust, development of a hydrophobic surface layer, or large-scale destruction of rain-intercepting vegetation did not play a role.

Water quality of selected streams in the coal area of southeastern Montana. Water-resources investigations (final)

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

Knapton, J.R.; McKinley, P.W.

1977-08-01

This report summarizes and evaluates water-quality data collected at 35 stream sites in the coal region of southeastern Montana. Sarpy Creek, Armells Creek, and Rosebud Creek sometimes have dissolved-solids concentrations that cause water to be marginal for agricultural purposes. At times of rainfall and snowmelt, the runoff water mixes with the base-flow component to improve the overall quality. Water in the Tongue River generally showed a downstream degradation in which some changes were related to the lithology of the aquifers contributing water to streamflow. Water from Pumpkin Creek and Mizpah Creek is used mostly for cattle watering. To some extentmore » water is used for irrigation although the salinity hazard was often high. The chemical quality of the Powder River changed little during flow downstream. High sediment loads of the river acted as transporting agents for many of the plant nutrients and trace-element constituents.« less

Potentiometric Surface of the Upper Floridan Aquifer in the St. Johns River Water Management District and Vicinity, Florida, May 2009

USGS Publications Warehouse

Kinnaman, Sandra L.; Dixon, Joann F.

2009-01-01

This map depicts the potentiometric surface of the Upper Floridan aquifer in the St. Johns River Water Management District and vicinity for May 2009. Potentiometric contours are based on water-level measurements collected at 625 wells during the period May 14 - May 29, near the end of the dry season. Some contours are inferred from previous potentiometric-surface maps with larger well networks. The potentiometric surface of the carbonate Upper Floridan aquifer responds mainly to rainfall, and more locally, to groundwater withdrawals and spring flow. Potentiometric-surface highs generally correspond to topographic highs where the aquifer is recharged. Springs and areas of diffuse upward leakage naturally discharge water from the aquifer and are most prevalent along the St. Johns River. Areas of discharge are reflected by depressions in the potentiometric surface. Groundwater withdrawals locally have lowered the potentiometric surface. Groundwater in the Upper Floridan aquifer generally flows from potentiometric highs to potentiometric lows in a direction perpendicular to the contours.

Potentiometric Surface of the Upper Floridan Aquifer in the St. Johns River Water Management District and Vicinity, Florida, September 2006

USGS Publications Warehouse

Kinnaman, Sandra L.; Dixon, Joann F.

2007-01-01

Introduction This map depicts the potentiometric surface of the Upper Floridan aquifer in the St. Johns River Water Management District and vicinity for September 2006. Potentiometric contours are based on water-level measurements collected at 571 wells during the period September 11-29, near the end of the wet season. Some contours are inferred from previouspotentiometric-surface maps with larger well networks. The potentiometric surface of the carbonate Upper Floridan aquifer responds mainly to rainfall, and more locally, to ground-water withdrawals and spring flow. Potentiometric-surface highs generally correspond to topographic highs where the aquifer is recharged. Springs and areas of diffuse upward leakage naturally discharge water from the aquifer and are most prevalent along the St. Johns River. Areas of discharge are reflected by depressions in the potentiometric surface. Ground-water withdrawals locally have lowered the potentiometric surface. Ground water in the Upper Floridan aquifer generally flows from potentiometric highs to potentiometric lows in a direction perpendicular to the contours.

Potentiometric Surface of the Upper Floridan Aquifer in the St. Johns River Water Management District and Vicinity, Florida, September 2008

USGS Publications Warehouse

Kinnaman, Sandra L.; Dixon, Joann F.

2009-01-01

This map depicts the potentiometric surface of the Upper Floridan aquifer in the St. Johns River Water Management District and vicinity for September 2008. Potentiometric contours are based on water-level measurements collected at 589 wells during the period September 15-25, near the end of the wet season. Some contours are inferred from previous potentiometric-surface maps with larger well networks. The potentiometric surface of the carbonate Upper Floridan aquifer responds mainly to rainfall, and more locally, to ground-water withdrawals and spring flow. Potentiometric-surface highs generally correspond to topographic highs where the aquifer is recharged. Springs and areas of diffuse upward leakage naturally discharge water from the aquifer and are most prevalent along the St. Johns River. Areas of discharge are reflected by depressions in the potentiometric surface. Ground-water withdrawals locally have lowered the potentiometric surface. Ground water in the Upper Floridan aquifer generally flows from potentiometric highs to potentiometric lows in a direction perpendicular to the contours.

Potentiometric Surface of the Upper Floridan Aquifer in the St. Johns River Water Management District and Vicinity, Florida, September 2007

USGS Publications Warehouse

Kinnaman, Sandra L.; Dixon, Joann F.

2008-01-01

This map depicts the potentiometric surface of the Upper Floridan aquifer in the St. Johns River Water Management District and vicinity for September 2007. Potentiometric contours are based on water-level measurements collected at 554 wells during the period September 15-27, near the end of the wet season. Some contours are inferred from previous potentiometric-surface maps with larger well networks. The potentiometric surface of the carbonate Upper Floridan aquifer responds mainly to rainfall, and more locally, to ground-water withdrawals and spring flow. Potentiometric-surface highs generally correspond to topographic highs where the aquifer is recharged. Springs and areas of diffuse upward leakage naturally discharge water from the aquifer and are most prevalent along the St. Johns River. Areas of discharge are reflected by depressions in the potentiometric surface. Ground-water withdrawals locally have lowered the potentiometric surface. Ground water in the Upper Floridan aquifer generally flows from potentiometric highs to potentiometric lows in a direction perpendicular to the contours.

Effect of dry spells and soil cracking on runoff generation in a semiarid micro watershed under land use change

NASA Astrophysics Data System (ADS)

dos Santos, Julio Cesar Neves; de Andrade, Eunice Maia; Guerreiro, Maria João Simas; Medeiros, Pedro Henrique Augusto; de Queiroz Palácio, Helba Araújo; de Araújo Neto, José Ribeiro

2016-10-01

Soil and water resources effective management and planning in a river basin rely on understanding of runoff generation processes, yield, and their relations to rainfall. This study analyzes the effects of antecedent soil moisture in an expansive soil and the influence of dry spells on soil cracking, runoff generation and yield in a semiarid tropical region in Brazil subject to land use change. Data were collected from 2009 to 2013 in a 2.8 ha watershed, totaling 179 natural rainfall events. In the first year of study (2009), the watershed maintained a typical dry tropical forest cover (arboreal-shrub Caatinga cover). Before the beginning of the second year of study, gamba grass (Andropogon gayanus Kunth) was cultivated after slash and burn of native vegetation. Gamba grass land use was maintained for the rest of the monitoring period. The occurrence of dry spells and the formation of cracks in the Vertisol soil were the most important factors controlling flow generation. Dry spells promoted crack formation in the expansive soil, which acted as preferential flow paths leading to high initial abstractions: average conditions for runoff to be generated included soil moisture content above 20%, rainfall above 70 mm, I30max above 60 mm h-1 and five continuous dry days at the most. The change of vegetation cover in the second year of study did not alter significantly the overall conditions for runoff initiation, showing similar cumulative flow vs. rainfall response, implying that soil conditions, such as humidity and cracks, best explain the flow generation process on the semiarid micro-scale watershed with Vertisol soil.

How would peak rainfall intensity affect runoff predictions using conceptual water balance models?

NASA Astrophysics Data System (ADS)

Yu, B.

2015-06-01

Most hydrological models use continuous daily precipitation and potential evapotranspiration for streamflow estimation. With the projected increase in mean surface temperature, hydrological processes are set to intensify irrespective of the underlying changes to the mean precipitation. The effect of an increase in rainfall intensity on the long-term water balance is, however, not adequately accounted for in the commonly used hydrological models. This study follows from a previous comparative analysis of a non-stationary daily series of stream flow of a forested watershed (River Rimbaud) in the French Alps (area = 1.478 km2) (1966-2006). Non-stationarity in the recorded stream flow occurred as a result of a severe wild fire in 1990. Two daily models (AWBM and SimHyd) were initially calibrated for each of three distinct phases in relation to the well documented land disturbance. At the daily and monthly time scales, both models performed satisfactorily with the Nash-Sutcliffe coefficient of efficiency (NSE) varying from 0.77 to 0.92. When aggregated to the annual time scale, both models underestimated the flow by about 22% with a reduced NSE at about 0.71. Exploratory data analysis was undertaken to relate daily peak hourly rainfall intensity to the discrepancy between the observed and modelled daily runoff amount. Preliminary results show that the effect of peak hourly rainfall intensity on runoff prediction is insignificant, and model performance is unlikely to improve when peak daily precipitation is included. Trend analysis indicated that the large decrease of precipitation when daily precipitation amount exceeded 10-20 mm may have contributed greatly to the decrease in stream flow of this forested watershed.

Hourly runoff forecasting for flood risk management: Application of various computational intelligence models

NASA Astrophysics Data System (ADS)

Badrzadeh, Honey; Sarukkalige, Ranjan; Jayawardena, A. W.

2015-10-01

Reliable river flow forecasts play a key role in flood risk mitigation. Among different approaches of river flow forecasting, data driven approaches have become increasingly popular in recent years due to their minimum information requirements and ability to simulate nonlinear and non-stationary characteristics of hydrological processes. In this study, attempts are made to apply four different types of data driven approaches, namely traditional artificial neural networks (ANN), adaptive neuro-fuzzy inference systems (ANFIS), wavelet neural networks (WNN), and, hybrid ANFIS with multi resolution analysis using wavelets (WNF). Developed models applied for real time flood forecasting at Casino station on Richmond River, Australia which is highly prone to flooding. Hourly rainfall and runoff data were used to drive the models which have been used for forecasting with 1, 6, 12, 24, 36 and 48 h lead-time. The performance of models further improved by adding an upstream river flow data (Wiangaree station), as another effective input. All models perform satisfactorily up to 12 h lead-time. However, the hybrid wavelet-based models significantly outperforming the ANFIS and ANN models in the longer lead-time forecasting. The results confirm the robustness of the proposed structure of the hybrid models for real time runoff forecasting in the study area.

5 years of continuous seismic monitoring of a mountain river in the Pyrenees

NASA Astrophysics Data System (ADS)

Diaz, Jordi; Sanchez-Pastor, Pilar S.; Gallart, Josep

2017-04-01

The analysis of background seismic noise variations in the proximity of river channels has revealed as a useful tool to monitor river flow, even for modest discharges. Nevertheless, this monitoring is usually carried on using temporal deployments of seismic stations. The CANF seismic broad-band station, acquiring data continuously since 2010 and located inside an old railway tunnel in the Central Pyrenees, at about 400 m of the Aragón River channel, provides an excellent opportunity to enlarge this view and present a long term monitoring of a mountain river. Seismic signals in the 2-10 Hz band clearly related to river discharges have been identified in the seismic records. Discharge increases due to rainfall, large storms resulting in floods and snowmelt periods can be discriminated from the analysis of the seismic data. Up to now, two large rainfall events resulting in large discharge and damaging floods have been recorded, both sharing similar properties which can be used to implement automatic procedures to identify seismically potentially damaging floods. Another natural process that can be characterized using continuouly acquired seismic data is mountain snowmelt, as this process results in characteristic discharge patterns which can be identified in the seismic data. The time occurrence and intensity of the snowmelt stages for each season can be identified and the 5 seasons available so far compared to detect possible trends The so-called fluvial seismology can also provide important clues to evaluate the beadload transport in rivers, an important parameter to evaluate erosion rates in mountain environments. Analyzing both the amplitude and frequency variations of the seismic data and its hysteresis cycles, it seems possible to estimate the relative contribution of water flow and bedload transport to the seismic signal. The available results suggest that most of the river-generated seismic signal seems related to bed load transportation, while water turbulence is only significant above a discharge thres.hold Since 2015 we are operating 2 additional stations located beside the Cinca and Segre Rivers, also in the Pyrenean range. First results confirm that the river-generated signal can also be identified at these sites, although wind-related signals are recorded in a close frequency band and hence some further analysis is required to discern between both processes. (Founding: MISTERIOS project, CGL2013-48601-C2-1-R)

Impacts of precipitation and temperature trends on different time scales on the water cycle and water resource availability in mountainous Mediterranean catchments.

NASA Astrophysics Data System (ADS)

José Pérez-Palazón, María; Pimentel, Rafael; Herrero, Javier; José Polo, María

2017-04-01

Climatology trends, precipitation and temperature variations condition the hydrological evolution of the river flow response at basin and sub-basin scales. The link between both climate and flow trends is crucial in mountainous areas, where small variations in temperature can produce significant impacts on precipitation (occurrence as rainfall or snowfall), snowmelt and evaporation, and consequently very different flow signatures. This importance is greater in semiarid regions, where the high variability of the climatic annual and seasonal regimes usually amplifies this impact on river flow. The Sierra Nevada National Park (Southern Spain), with altitudes ranging from 2000 to 3500 m.a.s.l., is part of the global climate change observatories network and a clear example of snow regions in a semiarid environment. This mountain range is head of different catchments, being the Guadalfeo River Basin one of the most influenced by the snow regime. This study shows the observed 55-year (1961-2015) trends of annual precipitation and daily mean temperature, and the associated impacts on snowfall and snow persistence, and the resulting trend of the annual river flow in the Guadalfeo River Basin (Southern Spain), a semiarid abrupt mountainous area (up to 3450 m a.s.l.) facing the Mediterranean Sea where the Alpine and Mediterranean climates coexist in a domain highly influenced by the snow regime, and a significant seasonality in the flow regime. The annual precipitation and annual daily mean temperature experimented a decreasing trend of 2.05 mm/year and an increasing trend of 0.037 °C/year, respectively, during the study period, with a high variability on a decadal basis. However, the torrential precipitation events are more frequent in the last few years of the study period, with an apparently increasing associated dispersion. The estimated annual snowfall trend shows a decreasing trend of 0.24 mm/year, associated to the decrease of precipitation rather than to temperature increase. From the analyses of river flow observations and hydrological modelling, these trends result in an estimated decreasing annual trend of the mean river inflow to reservoirs of 0.091 m3/s, which is equivalent to a mean loss of 2.87 hm3/year during the study period. Nonetheless, these results are associated to a high variability of both extreme values and the annual and decadal values. Moreover, the decrease of the annual inflow is approximately a 25% higher than the loss of precipitation, due to the impact on the different water fluxes from the snowpack associated to the enhanced torrential behaviour of both snowfall/rainfall occurrence and snow persistence. The results show the complexity of hydrological processes in Mediterranean regions, especially under the snow influence, and point out to a significant shift in the precipitation and temperature regime, and thus on the snow-affected hydrological variables in the study area, with a decrease of the available water resource volume in the medium and long term. However, on an annual basis, years with an intense snowfall regime but mild and longer dry periods result in a significant increase of the annual river flow and water storage. Reservoir operation criteria and water allocation should undergo a revision based on hydrological modelling of the snow regions and scenario analysis.

Groundwater resources of the Birim basin in Ghana

NASA Astrophysics Data System (ADS)

Asomaning, G.

1992-11-01

An attempt to assess ground water resources of a medium size (4775 km 2) drainage basin located on the Crystalline Complex in southern Ghana is presented. Mean annual rainfall 1578 mm, total river discharge 1,886,588 064 m 3 a -1, surface runoff 1,320,611,645 m 3 a -1, base flow 565,976,419 m 3 a -1, were determined from 13 meteorological and 1 river gauging stations located within the basin. From these data, the total runoff coefficient was 36%, surface runoff coefficient was 25% and the base flow coefficient was 11%. Then, Permanent Water Reserve, Qt = 5,333.20 × 106 m 3 and Recoverable Water Reserve, 2,133.28 × 10 6 m 3 a -1 for the aquifer of the basement complex aquifer of the basin were calculated from 42 boreholes.

Rainfall-Runoff Parameters Uncertainity

NASA Astrophysics Data System (ADS)

Heidari, A.; Saghafian, B.; Maknoon, R.

2003-04-01

Karkheh river basin, located in southwest of Iran, drains an area of over 40000 km2 and is considered a flood active basin. A flood forecasting system is under development for the basin, which consists of a rainfall-runoff model, a river routing model, a reservior simulation model, and a real time data gathering and processing module. SCS, Clark synthetic unit hydrograph, and Modclark methods are the main subbasin rainfall-runoff transformation options included in the rainfall-runoff model. Infiltration schemes, such as exponentioal and SCS-CN methods, account for infiltration losses. Simulation of snow melt is based on degree day approach. River flood routing is performed by FLDWAV model based on one-dimensional full dynamic equation. Calibration and validation of the rainfall-runoff model on Karkheh subbasins are ongoing while the river routing model awaits cross section surveys.Real time hydrometeological data are collected by a telemetry network. The telemetry network is equipped with automatic sensors and INMARSAT-C comunication system. A geographic information system (GIS) stores and manages the spatial data while a database holds the hydroclimatological historical and updated time series. Rainfall runoff parameters uncertainty is analyzed by Monte Carlo and GLUE approaches.

The Effects of a Changing Climate and Urbanisation on River Flows in the Thames Basin, UK - a Hydrological Modelling Approach

NASA Astrophysics Data System (ADS)

Miller, J. D.; Rickards, N. J.; Kjeldsen, T. R.; Hutchins, M.; Rowland, C.; Prudhomme, C.; Maliko, T.; Fidal, J.; Hagen-Zanker, A.

2016-12-01

The UK population is set to increase by 16% by 2035; it is therefore increasingly important to understand the impact this may have on urban populations, and in turn how this will affect river flow regimes and water quality in urban areas. A growing population is likely to lead to an increase in urban land use and impervious surfaces, the implications of which are not yet fully understood for issues such as future flood risk. The aim of this paper is to develop a greater understanding of the impacts of both an increasing population and urban extent in the context of a changing climate, and to assess the effect these may have on urban streamflow regimes and water security in the future. Flows are modelled for selected catchments in the Thames basin using URBMOD, a lumped rainfall runoff model that is able to represent both pervious and impervious surfaces, reducing infiltration in catchments where there is a greater urban extent. The model uses daily catchment average rainfall and evapotranspiration derived from gridded data, and is calibrated against long-term river flow records. Historic satellite imagery is used to train cellular automata land use models, which are then applied under different scenarios of urban development up to 2035. These changes in land use are combined with a range of climate change scenarios to give an indication of how urban flow regimes may be altered in the Thames basin over the next 20 years. Results suggest an intensification of the hydrological regime in the majority of catchments, with increases in high flow magnitudes (Q10) of up to 5%. The trend for low flows (Q90) is less clear, with some catchments displaying reductions of around 4%, whilst others show slight increased flows. We identify the main drivers behind these changes, from which the fine-scale impacts of urbanisation on water resources can be better understood. Research findings are being used to inform a regional-scale model, coupling water quantity and quality and providing insight to urban planners and stakeholders on the future urban hydrological regime in the Thames basin. Similar approaches are being used to assess impacts of anthropogenic drivers on water resources in the Cauvery basin in India, whereby the applicability of the model under very different climate and urban morphology will be tested.

Integration of climate change in flood prediction: application to the Somme river (France)

NASA Astrophysics Data System (ADS)

Pinault, J.-L.; Amraoui, N.; Noyer, M.-L.

2003-04-01

Exceptional floods that have occurred for the last two years in western and central Europe were very unlikely. The concomitance of such rare events shows that they might be imputable to climate change. The statistical analysis of long rainfall series confirms that both the cumulated annual height and the temporal variability have increased for the last decade. This paper is devoted to the analysis of climate change impact on flood prediction applied to the Somme river. The exceptional pluviometry that occurred from October 2000 to April 2001, about the double of the mean value, entailed catastrophic flood between the high Somme and Abbeville. The flow reached a peak at the beginning of May 2001, involving damages in numerous habitations and communication routes, and economical activity of the region had been flood-bound for more than 2 months. The flood caught unaware the population and caused deep traumas in France since it was the first time such a sudden event was recognized as resulting from groundwater discharge. Mechanisms of flood generation were studied tightly in order to predict the behavior of the Somme catchment and other urbanized basins when the pluviometry is exceptional in winter or in spring, which occurs more and more frequently in the northern part of Europe. The contribution of groundwater in surface water flow was calculated by inverse modeling from piezometers that are representative of aquifers in valleys. They were found on the slopes and near the edge of plateaus in order to characterize the drainage processes of the watertable to the surface water network. For flood prediction, a stochastic process is used, consisting in the generation of both rainfall and PET time series. The precipitation generator uses Markov chain Monte Carlo and simulated annealing from the Hastings -- Metropolis algorithm. Coupling of rainfall and PET generators with transfer enables a new evaluation of the probability of occurrence of floods, taking into account both the memory effect of the Somme basin and the temporal structure of rainfall events.

Elevation of the March - April 2010 flood high water in selected river reaches in central and eastern Massachusetts

USGS Publications Warehouse

Zarriello, Phillip J.; Bent, Gardner C.

2011-01-01

A series of widespread, large, low-pressure systems in southern New England in late February through late March 2010 resulted in record, or near record, rainfall and runoff. The total rainfall in the region during this period ranged from about 17 to 25 inches, which coupled with seasonal low evaporation, resulted in record or near record peak flows at 13 of 37 streamgages in central and eastern Massachusetts. The highest record peaks generally occurred in southeastern Massachusetts in late March - early April; at most other streamgages, the peak was in mid-March. Determination of the flood-peak high-water elevation is a critical part of the recovery operations and post-flood analysis for improving future flood-hazard maps and flood-management practices. High-water marks (HWMs) were identified by the U.S. Geological Survey (USGS) from April 13 through May 10, 2010, and by a consultant for Massachusetts Department of Conservation and Recreation (MADCR) after peak flows in mid-March and again in late March - early April. HWMs were identified at 25 river reaches in 7 designated Massachusetts Executive Office of Energy and Environmental Affairs (EEA) basins by the USGS and at 8 river reaches in 2 designated EEA basins by MADCR. The USGS identified 293 HWMs at 152 sites. A site may have more than one HWM, typically upstream and downstream from a bridge. The MADCR identified 133 HWMs; of these, 98 are at unique locations, and 29 of the 133 HWMs were visited once following the mid-March peak and again following the late March peak. The HWMs identified by the USGS and MADCR covered about 300 river miles, determined from the upstream and downstream HWMs (about 230 and 70 river miles, respectively). Elevation of HWMs was later determined to a standard vertical datum (NAVD 88) using the Global Navigation Satellite System and survey grade Global Positioning System (GPS) receivers along with standard optical surveying equipment.

Rainfall and irrigation controls on groundwater rise and salinity risk in the Ord River Irrigation Area, northern Australia

NASA Astrophysics Data System (ADS)

Smith, Anthony J.

2008-09-01

Groundwater beneath the Ord River Irrigation Area (ORIA) in northern Australia has risen in elevation by 10-20 m during the past 40 years with attendant concerns about water logging and soil salinization. Persistent groundwater accession has been attributed to excessive irrigation and surface water leakage; however, analysis of daily water-table records from the past 10 years yielded a contrary result. On a seasonal basis, water-table elevation typically fell during irrigation (dry) seasons and rose during fallow (wet) seasons, conflicting with the conventional view that irrigation and not rainfall must be the dominant control on groundwater accession. Previous investigations of unexpectedly large infiltration losses through the cracking clay soils provide a plausible explanation for the apparent conundrum. Because rainfall is uncontrolled and occurs independently of the soil moisture condition, there is greater opportunity for incipient ponding and rapid infiltration through preferred flow pathways. In contrast, irrigation is scheduled when needed and applications are stopped after soil wetting is achieved. Contemporary groundwater management in the ORIA is focused on improving irrigation efficiency during dry seasons but additional opportunities may exist to improve groundwater conditions and salinity risk through giving equal attention to the wet-season water balance.

Assessment of snow-glacier melt and rainfall contribution to stream runoff in Baspa Basin, Indian Himalaya.

PubMed

Gaddam, Vinay Kumar; Kulkarni, Anil V; Gupta, Anil Kumar

2018-02-20

Hydrological regimes of most of the Himalayan river catchments are poorly studied due to sparse hydro-meteorological data. Hence, stream runoff assessment becomes difficult for various socio-industrial activities in the Himalaya. Therefore, an attempt is made in this study to assess the stream runoff of Baspa River in Himachal Pradesh, India, by evaluating the contribution from snow-ice melt and rainfall runoff. The total volume of flow was computed for a period of 15 years, from 2000 to 2014, and validated with the long-term field discharge measurements, obtained from Jaipee Hydropower station (31° 32' 35.53″ N, 78° 00' 54.80″ E), at Kuppa barrage in the basin. The observations suggest (1) a good correlation (r 2  > 0.80) between the modeled runoff and field discharge measurements, and (2) out of the total runoff, 81.2% are produced by snowmelt, 11.4% by rainfall, and 7.4% from ice melt. The catchment receives ~75% of its total runoff in the ablation period (i.e., from May to September). In addition, an early snowmelt is observed in accumulation season during study period, indicating the significant influence of natural and anthropogenic factors on high-altitude areas.

Radon as a tracer to characterize the interactions between groundwater and surface water around the ground source heat pump system in riverside area

NASA Astrophysics Data System (ADS)

Kim, Jaeyeon; Lee, Seong-Sun; Lee, Kang-Kun

2016-04-01

The interaction characteristics between groundwater and surface water was examined by using Radon-222 at Han River Environmental Research Center (HRERC) in Korea where a geothermal resource using indirect open loop ground source heat pump (GSHP) has been developed. For designing a high efficiency performance of the open loop system in shallow aquifer, the riverside area was selected for great advantage of full capacity of well. From this reason groundwater properties of the study site can be easily influenced by influx of surrounding Han River. Therefore, 12 groundwater wells were used for monitoring radon concentration and groundwater level with fluctuation of river stage from May, 2014 to Apr., 2015. The short term monitoring data showed that the radon concentration was changed in accordance with flow meter data which was reflected well by the river stage fluctuation. The spatial distribution of radon concentration from long term monitoring data was also found to be affected by water level fluctuation by nearby dam activity and seasonal effect such as heavy rainfall and groundwater pumping. The estimated residence time indicates that river flows to the study site change its direction according to the combined effect of river stage and groundwater hydrology. In the linear regression of the values, flow velocities were yielded around 0.04 to 0.25 m/day which were similar to flow meter data. These results reveal that Radon-222 can be used as an appropriate environmental tracer in examining the characteristics of interaction in consideration of fluctuating river flow on operation of GSHP in the riverside area. ACKNOWLEDGEMENT This work was supported by the research project of "Advanced Technology for Groundwater Development and Application in Riversides (Geowater+) in "Water Resources Management Program (code 11 Technology Innovation C05)" of the MOLIT and the KAIA in Korea.

[Response Mechanism of Trace Metals in the Bishuiyan Subterranean River to the Rainfall and Their Source Analysis].

PubMed

Zou, Yan-e; Jiang, Ping-ping; Zhang, Qiang; Tang, Qing-jia; Kang, Zhi-qiang; Gong, Xiao- ping; Chen, Chang-jie; Yu, Jian-guo

2015-12-01

High-frequency sampling was conducted at the outlet of Guangxi Bishuiyan karst subterranean river using an automatic sampler during the rainfall events. The hydrochemical drymanic variation characteristics of trace metals (Cu, Pb, Zn, Cd) at the outlet of Guangxi Bishuiyan karst subterranean river were analyzed, and the sources of the trace metals in the subterranean river as well as their response to rainfall were explored. The results showed that the rainfall provoked a sharp decrease in the major elements (Ca²⁺, Mg²⁺, HCO₃⁻, etc.) due to dilution and precipitation, while it also caused an increase in the concentrations of dissolved metals including Al, Mn, Cu, Zn and Cd, due to water-rock reaction, sediment remobilization, and soil erosion. The water-rock reaction was more sensitive to rainfall than the others, while the sediment remobilization and soil erosion took the main responsibility for the chemical change of the heavy metals. The curves of the heavy metal concentrations presented multiple peaks, of which the maximum was reached at 9 hours later after the largest precipitation. Different metal sources and the double-inlet structure of the subterranean river were supposed to be the reasons for the formation of multiple peaks. During the monitoring period, the average speed of the solute in the river reached about 0.47 km · h⁻¹, indicating fast migration of the pollutants. Therefore, monitoring the chemical dynamics of the karst subterranean river, mastering the sources and migration characteristics of trace metal components have great significance for the subterranean river environment pollution treatment.

The Use of Radar to Improve Rainfall Estimation over the Tennessee and San Joaquin River Valleys

NASA Technical Reports Server (NTRS)

Petersen, Walter A.; Gatlin, Patrick N.; Felix, Mariana; Carey, Lawrence D.

2010-01-01

This slide presentation provides an overview of the collaborative radar rainfall project between the Tennessee Valley Authority (TVA), the Von Braun Center for Science & Innovation (VCSI), NASA MSFC and UAHuntsville. Two systems were used in this project, Advanced Radar for Meteorological & Operational Research (ARMOR) Rainfall Estimation Processing System (AREPS), a demonstration project of real-time radar rainfall using a research radar and NEXRAD Rainfall Estimation Processing System (NREPS). The objectives, methodology, some results and validation, operational experience and lessons learned are reviewed. The presentation. Another project that is using radar to improve rainfall estimations is in California, specifically the San Joaquin River Valley. This is part of a overall project to develop a integrated tool to assist water management within the San Joaquin River Valley. This involves integrating several components: (1) Radar precipitation estimates, (2) Distributed hydro model, (3) Snowfall measurements and Surface temperature / moisture measurements. NREPS was selected to provide precipitation component.

Prospects for seasonal forecasting of summer drought and low river flow anomalies in England and Wales

NASA Astrophysics Data System (ADS)

Wedgbrow, C. S.; Wilby, R. L.; Fox, H. R.; O'Hare, G.

2002-02-01

Future climate change scenarios suggest enhanced temporal and spatial gradients in water resources across the UK. Provision of seasonal forecast statistics for surface climate variables could alleviate some negative effects of climate change on water resource infrastructure. This paper presents a preliminary investigation of spatial and temporal relationships between large-scale North Atlantic climatic indices, drought severity and river flow anomalies in England and Wales. Potentially useful predictive relationships are explored between winter indices of the Polar-Eurasian (POL) teleconnection pattern, the North Atlantic oscillation (NAO), North Atlantic sea surface temperature anomalies (SSTAs), and the summer Palmer drought severity index (PDSI) and reconstructed river flows in England and Wales. Correlation analyses, coherence testing and an index of forecast potential, demonstrate that preceding winter values of the POL index, SSTA (and to a lesser extent the NAO), provide indications of summer and early autumn drought severity and river flow anomalies in parts of northwest, southwest and southeast England. Correlation analyses demonstrate that positive winter anomalies of T1, POL index and NAO index are associated with negative PDSI (i.e. drought) across eastern parts of the British Isles in summer (r < 0.51). Coherence tests show that a positive winter SSTA (1871-1995) and POL index (1950-95) have preceded below-average summer river flows in the northwest and southwest of England and Wales in 70 to 100% of summers. The same rivers have also experienced below-average flows during autumn following negative winter phases of the NAO index in 64 to 93% of summers (1865-1995). Possible explanations for the predictor-predictand relationships are considered, including the memory of groundwater, and ocean-atmosphere coupling, and regional manifestations of synoptic rainfall processes. However, further research is necessary to increase the number of years and predictor variables from which it is possible to derive rules that may be useful for forecasting.

Role of antecedent conditions on nitrogen and phosphorus mobilisation observed in a lowland arable catchment in eastern England: insights from high-frequency monitoring

NASA Astrophysics Data System (ADS)

Outram, Faye; Hiscock, Kevin; Dugdale, Stephen; Lovett, Andrew

2015-04-01

In order to reduce annual riverine loadings of nutrients which are responsible for degradation of ecosystems downstream and in near coastal areas, it is important to first understand the mobilisation and pathways responsible for transporting them from source to river and how these pathways vary in space and time. The Blackwater tributary of the River Wensum in Norfolk, England, has been equipped with a sensor network as part of the Demonstration Test Catchments project, which has the aim of reducing pollution from agriculture to river systems whilst maintaining food security by the trial of mitigation measures on working farms at the sub-catchment level. The River Wensum is a lowland chalk catchment with intensive arable agriculture and high occurrence of tile drainage on heavier soils. Three hydrological years of high-frequency data have been gathered in the Blackwater since October 2011, including rainfall, half hourly measurements of discharge and groundwater level coupled with hydrochemical parameters including nitrate, total phosphorus (TP) and total reactive phosphorus (TRP). In the three years of data collection, there were distinct departures from long-term rainfall averages as the winter of 2011-12 was extremely dry following a drought from the previous hydrological year, followed by a summer which was unseasonably wet, which continued into the following winter. The relationship between rainfall, storage and discharge was found to be complex, which in turn had an impact on the dominant controls transporting nutrients from the landscape to the river network. Thirty three storms occurred throughout the three year period which have been analysed in the context of the range of hydrometeorological conditions observed throughout the dataset. Discharge-concentration hysteretic responses of nitrogen, TP and TRP have been used alongside statistical analysis of storm characteristics including antecedent hydrological conditions. The nitrate storm response showed distinct seasonal patterns which were greatly impacted by the activation of tile drain flow throughout the winter period and during the fertiliser application window between March-May, with the dry winter in 2011-12 standing apart from the more 'typical' years. Four different storm response categories were identified for nitrate according to dominant flow pathways. The phosphorus response was far less uniform throughout the study period, showing patterns of exhaustion with successive events. Both nitrate and phosphorus loads were disproportionate to flow volume in storm events which occurred after significant dry periods. The data show the importance of antecedent conditions in the storage, mobilisation and transport of nitrogen and phosphorus in agricultural catchments which has important implications for the conceptual understanding of catchment functioning and environmental management.

Evaluating climatic and non-climatic stresses for declining surface water quality in Bagmati River of Nepal.

PubMed

Panthi, Jeeban; Li, Fengting; Wang, Hongtao; Aryal, Suman; Dahal, Piyush; Ghimire, Sheila; Kabenge, Martin

2017-06-01

Both climatic and non-climatic factors affect surface water quality. Similar to its effect across various sectors and areas, climate change has potential to affect surface water quality directly and indirectly. On the one hand, the rise in temperature enhances the microbial activity and decomposition of organic matter in the river system and changes in rainfall alter discharge and water flow in the river ultimately affecting pollution dilution level. On the other hand, the disposal of organic waste and channelizing municipal sewage into the rivers seriously worsen water quality. This study attempts to relate hydro-climatology, water quality, and impact of climatic and non-climatic stresses in affecting river water quality in the upper Bagmati basin in Central Nepal. The results showed that the key water quality indicators such as dissolved oxygen and chemical oxygen demand are getting worse in recent years. No significant relationships were found between the key water quality indicators and changes in key climatic variables. However, the water quality indicators correlated with the increase in urban population and per capita waste production in the city. The findings of this study indicate that dealing with non-climatic stressors such as reducing direct disposal of sewerage and other wastes in the river rather than emphasizing on working with the effects from climate change would largely help to improve water quality in the river flowing from highly populated urban areas.

Daily river flow prediction based on Two-Phase Constructive Fuzzy Systems Modeling: A case of hydrological - meteorological measurements asymmetry

NASA Astrophysics Data System (ADS)

Bou-Fakhreddine, Bassam; Mougharbel, Imad; Faye, Alain; Abou Chakra, Sara; Pollet, Yann

2018-03-01

Accurate daily river flow forecast is essential in many applications of water resources such as hydropower operation, agricultural planning and flood control. This paper presents a forecasting approach to deal with a newly addressed situation where hydrological data exist for a period longer than that of meteorological data (measurements asymmetry). In fact, one of the potential solutions to resolve measurements asymmetry issue is data re-sampling. It is a matter of either considering only the hydrological data or the balanced part of the hydro-meteorological data set during the forecasting process. However, the main disadvantage is that we may lose potentially relevant information from the left-out data. In this research, the key output is a Two-Phase Constructive Fuzzy inference hybrid model that is implemented over the non re-sampled data. The introduced modeling approach must be capable of exploiting the available data efficiently with higher prediction efficiency relative to Constructive Fuzzy model trained over re-sampled data set. The study was applied to Litani River in the Bekaa Valley - Lebanon by using 4 years of rainfall and 24 years of river flow daily measurements. A Constructive Fuzzy System Model (C-FSM) and a Two-Phase Constructive Fuzzy System Model (TPC-FSM) are trained. Upon validating, the second model has shown a primarily competitive performance and accuracy with the ability to preserve a higher day-to-day variability for 1, 3 and 6 days ahead. In fact, for the longest lead period, the C-FSM and TPC-FSM were able of explaining respectively 84.6% and 86.5% of the actual river flow variation. Overall, the results indicate that TPC-FSM model has provided a better tool to capture extreme flows in the process of streamflow prediction.

Analysis of trends in streamflow and its linkages with rainfall and anthropogenic factors in Gomti River basin of North India

NASA Astrophysics Data System (ADS)

Abeysingha, N. S.; Singh, Man; Sehgal, V. K.; Khanna, Manoj; Pathak, Himanshu

2016-02-01

Trend analysis of hydro-climatic variables such as streamflow, rainfall, and temperature provides useful information for effective water resources planning, designing, and management. Trends in observed streamflow at four gauging stations in the Gomti River basin of North India were assessed using the Mann-Kendall and Sen's slope for the 1982 to 2012 period. The relationships between trends in streamflow and rainfall were studied by correlation analyses. There was a gradual decreasing trend of annual, monsoonal, and winter seasonal streamflow ( p < 0.05) from the midstream to the downstream of the river and also a decreasing trend of annual streamflow for the 5-year moving averaged standardized anomalies of streamflow for the entire basin. The declining trend in the streamflow was attributed partly to the increased water withdrawal, to increased air temperature, to higher population, and partly to significant reducing trend of post monsoon rainfall especially at downstream. Upstream gauging station showed a significant increasing trend of streamflow (1.6 m3/s/year) at annual scale, and this trend was attributed to the significant increasing trend of catchment rainfall (9.54 mm/year). It was further evident in the significant coefficient of positive correlation ( ρ = 0.8) between streamflow and catchment rainfall. The decreasing trend in streamflow and post-monsoon rainfall especially towards downstream area with concurrent increasing trend of temperature indicates a drying tendency of the Gomti River basin over the study period. The results of this study may help stakeholders to design streamflow restoration strategies for sustainable water management planning of the Gomti River basin.

2007 Weather and Aeolian Sand-Transport Data from the Colorado River Corridor, Grand Canyon, Arizona

USGS Publications Warehouse

Draut, Amy E.; Andrews, Timothy; Fairley, Helen C.; Brown, Christopher R.

2009-01-01

Weather data constitute an integral part of ecosystem monitoring in the Colorado River corridor and are particularly valuable for understanding processes of landscape change that contribute to the stability of archeological sites. Data collected in 2007 are reported from nine weather stations in the Colorado River corridor through Grand Canyon, Ariz. The stations were deployed in February and March 2007 to measure wind speed and direction, rainfall, air temperature, relative humidity, and barometric pressure. Sand traps near each weather station collect windblown sand, from which daily aeolian sand-transport rates are calculated. The data reported here were collected as part of an ongoing study to test and evaluate methods for quantifying processes that affect the physical integrity of archeological sites along the river corridor; as such, these data can be used to identify rainfall events capable of causing gully incision and to predict likely transport pathways for aeolian sand, two landscape processes integral to the preservation of archeological sites. Weather data also have widespread applications to other studies of physical, cultural, and biological resources in Grand Canyon. Aeolian sand-transport data reported here, collected in the year before the March 2008 High-Flow Experiment (HFE) at Glen Canyon Dam, represent baseline data against which the effects of the 2008 HFE on windblown sand will be compared in future reports.

What Is Driving the Observed Changes in Flooding in the Turkey River in Iowa?

NASA Astrophysics Data System (ADS)

Smith, C.; Yu, G.; Wright, D.

2017-12-01

Flooding can have severe societal, economic, and environmental consequences. In the United States-and worldwide-flooding causes fatalities and billions of dollars in economic loss. Recent research has pointed to changing flood risks in the Midwestern United States. However, we have a limited understanding of what natural and human factors are driving these changes. Researchers have proposed several possible explanations. Increasing intensity of short-duration summertime rainfall, reduced snow cover and earlier snow and soil thaw, changes in land surface evapotranspiration, and the effects of urbanization and agricultural management practices may all play roles in the shifts seen in the hydrologic cycle and flooding in Midwest. This study intends to look at the changes in the region on a smaller scale, whereas most previous research has examined at broad regional trends. Our focus will be on the agricultural Turkey River watershed in northeastern Iowa, where the flood hydroclimatology shows an abrupt shift around the year 1990 toward lower mean annual floods and dramatic increases in the magnitude and frequency of the largest floods. Analyses of land use, temperature, rainfall, river flow, and atmospheric properties, as well as simple continuous hydrologic simulations will aid in our understanding of the flood behavior of Turkey River and its drivers. In doing so, we hope to shed light on the causes of the changes in flooding and hydrology more generally that are taking place throughout the region.

Reduced precipitation over large water bodies in the Brazilian Amazon shown from TRMM data

NASA Astrophysics Data System (ADS)

Paiva, Rodrigo Cauduro Dias; Buarque, Diogo Costa; Clarke, Robin T.; Collischonn, Walter; Allasia, Daniel Gustavo

2011-02-01

Tropical Rainfall Measurement Mission (TRMM) data show lower rainfall over large water bodies in the Brazilian Amazon. Mean annual rainfall (P), number of wet days (rainfall > 2 mm) (W) and annual rainfall accumulated over 3-hour time intervals (P3hr) were computed from TRMM 3B42 data for 1998-2009. Reduced rainfall was marked over the Rio Solimões/Amazon, along most Amazon tributaries and over the Balbina reservoir. In a smaller test area, a heuristic argument showed that P and W were reduced by 5% and 6.5% respectively. Allowing for TRMM 3B42 spatial resolution, the reduction may be locally greater. Analyses of diurnal rainfall patterns showed that rainfall is lowest over large rivers during the afternoon, when most rainfall is convective, but at night and early morning the opposite occurs, with increased rainfall over rivers, although this pattern is less marked. Rainfall patterns reported from studies of smaller Amazonian regions therefore exist more widely.

Artificial neural networks applied to flow prediction scenarios in Tomebamba River - Paute watershed, for flood and water quality control and management at City of Cuenca Ecuador

NASA Astrophysics Data System (ADS)

Cisneros, Felipe; Veintimilla, Jaime

2013-04-01

The main aim of this research is to create a model of Artificial Neural Networks (ANN) that allows predicting the flow in Tomebamba River both, at real time and in a certain day of year. As inputs we are using information of rainfall and flow of the stations along of the river. This information is organized in scenarios and each scenario is prepared to a specific area. The information is acquired from the hydrological stations placed in the watershed using an electronic system developed at real time and it supports any kind or brands of this type of sensors. The prediction works very good three days in advance This research includes two ANN models: Back propagation and a hybrid model between back propagation and OWO-HWO. These last two models have been tested in a preliminary research. To validate the results we are using some error indicators such as: MSE, RMSE, EF, CD and BIAS. The results of this research reached high levels of reliability and the level of error are minimal. These predictions are useful for flood and water quality control and management at City of Cuenca Ecuador

Water Management To Meet Challenges In Food Production ­ An Example From South India

NASA Astrophysics Data System (ADS)

Shadananan, K.

Demands for food and water have been increasing with fast increasing population in many developing countries. Availability of water and fertile land, the two basic requirements for food production do not meet together in certain regions. In such regions, cooperation and efficient management practices can solve the problem to a good extend. The southern states of Kerala and Tamil Nadu of India are divided by the mountain chains, the Western Ghats the orography of which makes Kerala one among the heaviest rainfall region in the World itself and Tamil Nadu a scanty rainfall region. Kerala receives more than 300cm average annual rainfall, giving birth to a number of perennial rivers and other water bodies whereas Tamil Nadu receives rainfall less than100cm. Most of the rivers of Tamil Nadu are seasonal and it depends on interstate water transfer to face the permanent water shortage. Owing to the high density of population, peculiar topography and soil types, agricultural production in Kerala is quite inadequate and the State depends on neighbouring States, especially Tamil Nadu for rice and vegetables, but not willing to share water. According to the Constitution of India, control of rivers is by individual states and this often leads to transboundary water disputes that retard development activities. Around 80% of the rainfall of Kerala wastefully flows into the Sea, when there is acute water shortage in Tamil Nadu. All the rivers in Kerala originate in the Ghats and its steep slopes makes more water storage difficult. Cooperation among the States become essential for meeting the increasing needs in water and food. If some of the water from the catchments in Kerala is diverted into Tamil Nadu, and the States can do joint agriculture, it can meet the challenges due to increase in population and environmental changes and minimize unemployment problems. Water diversion to Tamil Naduwill reduce flood damage and soil erosion in Kerala. The existing socio-economic conditions in these States can be effectively utilised for the overall development. The present research paper is an assessment of the water and food situation in this region, in view of increasing needs associated with rise in population and change in environment. Detailed analysis of the water surpluses and deficiencies has been made using water balance model and suggestions for the better management have been presented.

Comparative Performance Evaluation of Rainfall-runoff Models, Six of Black-box Type and One of Conceptual Type, From The Galway Flow Forecasting System (gffs) Package, Applied On Two Irish Catchments

NASA Astrophysics Data System (ADS)

Goswami, M.; O'Connor, K. M.; Shamseldin, A. Y.

The "Galway Real-Time River Flow Forecasting System" (GFFS) is a software pack- age developed at the Department of Engineering Hydrology, of the National University of Ireland, Galway, Ireland. It is based on a selection of lumped black-box and con- ceptual rainfall-runoff models, all developed in Galway, consisting primarily of both the non-parametric (NP) and parametric (P) forms of two black-box-type rainfall- runoff models, namely, the Simple Linear Model (SLM-NP and SLM-P) and the seasonally-based Linear Perturbation Model (LPM-NP and LPM-P), together with the non-parametric wetness-index-based Linearly Varying Gain Factor Model (LVGFM), the black-box Artificial Neural Network (ANN) Model, and the conceptual Soil Mois- ture Accounting and Routing (SMAR) Model. Comprised of the above suite of mod- els, the system enables the user to calibrate each model individually, initially without updating, and it is capable also of producing combined (i.e. consensus) forecasts us- ing the Simple Average Method (SAM), the Weighted Average Method (WAM), or the Artificial Neural Network Method (NNM). The updating of each model output is achieved using one of four different techniques, namely, simple Auto-Regressive (AR) updating, Linear Transfer Function (LTF) updating, Artificial Neural Network updating (NNU), and updating by the Non-linear Auto-Regressive Exogenous-input method (NARXM). The models exhibit a considerable range of variation in degree of complexity of structure, with corresponding degrees of complication in objective func- tion evaluation. Operating in continuous river-flow simulation and updating modes, these models and techniques have been applied to two Irish catchments, namely, the Fergus and the Brosna. A number of performance evaluation criteria have been used to comparatively assess the model discharge forecast efficiency.

Multiple runoff processes and multiple thresholds control agricultural runoff generation

NASA Astrophysics Data System (ADS)

Saffarpour, Shabnam; Western, Andrew W.; Adams, Russell; McDonnell, Jeffrey J.

2016-11-01

Thresholds and hydrologic connectivity associated with runoff processes are a critical concept for understanding catchment hydrologic response at the event timescale. To date, most attention has focused on single runoff response types, and the role of multiple thresholds and flow path connectivities has not been made explicit. Here we first summarise existing knowledge on the interplay between thresholds, connectivity and runoff processes at the hillslope-small catchment scale into a single figure and use it in examining how runoff response and the catchment threshold response to rainfall affect a suite of runoff generation mechanisms in a small agricultural catchment. A 1.37 ha catchment in the Lang Lang River catchment, Victoria, Australia, was instrumented and hourly data of rainfall, runoff, shallow groundwater level and isotope water samples were collected. The rainfall, runoff and antecedent soil moisture data together with water levels at several shallow piezometers are used to identify runoff processes in the study site. We use isotope and major ion results to further support the findings of the hydrometric data. We analyse 60 rainfall events that produced 38 runoff events over two runoff seasons. Our results show that the catchment hydrologic response was typically controlled by the Antecedent Soil Moisture Index and rainfall characteristics. There was a strong seasonal effect in the antecedent moisture conditions that led to marked seasonal-scale changes in runoff response. Analysis of shallow well data revealed that streamflows early in the runoff season were dominated primarily by saturation excess overland flow from the riparian area. As the runoff season progressed, the catchment soil water storage increased and the hillslopes connected to the riparian area. The hillslopes transferred a significant amount of water to the riparian zone during and following events. Then, during a particularly wet period, this connectivity to the riparian zone, and ultimately to the stream, persisted between events for a period of 1 month. These findings are supported by isotope results which showed the dominance of pre-event water, together with significant contributions of event water early (rising limb and peak) in the event hydrograph. Based on a combination of various hydrometric analyses and some isotope and major ion data, we conclude that event runoff at this site is typically a combination of subsurface event flow and saturation excess overland flow. However, during high intensity rainfall events, flashy catchment flow was observed even though the soil moisture threshold for activation of subsurface flow was not exceeded. We hypothesise that this was due to the activation of infiltration excess overland flow and/or fast lateral flow through preferential pathways on the hillslope and saturation overland flow from the riparian zone.

Developing New Modelling Tools for Environmental Flow Assessment in Regulated Salmon Rivers

NASA Astrophysics Data System (ADS)

Geris, Josie; Soulsby, Chris; Tetzlaff, Doerthe

2013-04-01

There is a strong political drive in Scotland to meet all electricity demands from renewable sources by 2020. In Scotland, hydropower generation has a long history and is a key component of this strategy. However, many rivers sustain freshwater communities that have both high conservation status and support economically important Atlantic salmon fisheries. Both new and existing hydropower schemes must be managed in accordance with the European Union's Water Framework Directive (WFD), which requires that all surface water bodies achieve good ecological status or maintain good ecological potential. Unfortunately, long-term river flow monitoring is sparse in the Scottish Highlands and there are limited data for defining environmental flows. The River Tay is the most heavily regulated catchment in the UK. To support hydropower generation, it has an extensive network of inter- and intra- catchment transfers, in addition to a large number of regulating reservoirs for which abstraction legislation often only requires minimum compensation flows. The Tay is also considered as one of Scotland's most important rivers for Atlantic salmon (Salmo salar), and there is considerable uncertainty as to how best change reservoir operations to improve the ecological potential of the river system. It is now usually considered that environmental flows require more than a minimum compensation flow, and instead should cover a range of hydrological flow aspects that represent ecologically relevant streamflow attributes, including magnitude, timing, duration, frequency and rate of change. For salmon, these hydrological indices are of particular interest, with requirements varying at different stages of their life cycle. To meet the WFD requirements, rationally alter current abstraction licences and provide an evidence base for regulating new hydropower schemes, advanced definitions for abstraction limits and ecologically appropriate flow releases are desirable. However, a good understanding of the natural flow variability and the hydrological impacts of the regulation is unavailable, partly because pre-regulation data of existing hydropower schemes are lacking. Here we develop a novel modelling approach for characterising natural flow regimes and defining hydrological flow indices. This allows us to quantitatively assess the impacts of hydropower to better inform environmental flow requirements for the Atlantic salmon river ecosystem. Results are presented for the River Lyon (390 km2), a regulated headwater catchment of the River Tay. The HBV hydrological rainfall-runoff model is used to simulate flows, based on calibrated parameters from regulated flow data, with the current hydropower scheme active. For this, the HBV model is adapted to be able to incorporate water transfers and regulated flows. The natural hydrological indices are derived from the simulated pre-regulation data, and compared with those of the regulated data to investigate the impact of the regulation on these at different critical times for Atlantic salmon. The sensitivity of the system to change is also investigated to explore the extent to which flow variables can be modified without major degradation to the river's ecosystem, while still maintaining viable hydropower generation. The modelling approach presented will provide the basis for assessing impacts on hydrological flow indices and informing environmental flows in regions with similar heavily regulated mountain river ecosystems.

Disaster mitigation at drainage basin of Kuranji Padang City

NASA Astrophysics Data System (ADS)

Utama, L.; Yamin, M.

2017-06-01

Floods is flooding of effect of exit water groove river because big river debit sudden its accomodation energy, happened swiftly knock over areas which is debasement, in river basin and hollow. Flow debris or which is recognized with galodo have knock over river of Kuranji year 2012 in Padang city. Area is floods disaster are: 19 Sub-District in 7 district, and hard that is district of Pauh and district of Nanggalo. Governmental claim tired loss of Rp 263,9 Billion while Government of Provinsi West Sumatera appraise loss estimated by Fourty Billion Rupiah (Padang Ekspress 28 July 2012), with detail of damage house counted 878 unit, damage religious service house 15 unit, damage irrigation 12 unit, damage bridge 6 unit, damage school 2 unit, damage health post 1 unit. Result of calculation, by using rainfall of year 2003 until year 2015 with method Gumbel, Hasper and Wedwen, got high rainfall plan is 310,00 mm, and method Melchior and Hasper floods is 1125,86 m³ / second. From result of study analyse at Citra map of correlation and image to parameters cause of floods, and use software Watershed Modelling System (WMS) this region have two class that is middle susceptance and low susceptance. Middle susceptance area is there are in middle river and downstream river, with inclination level off. Low susceptance area there is middle river. Area which have potency result the happening of floods is headwaters, because having keen ramp storey level ( 45 - 55%) and is hilly. For the mitigasi of floods disaster determined by three area evacuate that are: Sub-District Of Kelurahan Limau Manis District Of Pauh, Sub-District Of Surau Gadang District Of Nanggalo, and Sub-District Of Lambung Bukik District of Pauh, in the form of map.

Estimation of sediment yield from subsequent expanded landslides after heavy rainfalls : a case study in central Hokkaido, Japan

NASA Astrophysics Data System (ADS)

Koshimizu, K.; Uchida, T.

2015-12-01

Initial large-scale sediment yield caused by heavy rainfall or major storms have made a strong impression on us. Previous studies focusing on landslide management investigated the initial sediment movement and its mechanism. However, integrated management of catchment-scale sediment movements requires estimating the sediment yield, which is produced by the subsequent expanded landslides due to rainfall, in addition to the initial landslide movement. This study presents a quantitative analysis of expanded landslides by surveying the Shukushubetsu River basin, at the foot of the Hidaka mountain range in central Hokkaido, Japan. This area recorded heavy rainfall in 2003, reaching a maximum daily precipitation of 388 mm. We extracted the expanded landslides from 2003 to 2008 using aerial photographs taken over the river area. In particular, we calculated the probability of expansion for each landslide, the ratio of the landslide area in 2008 as compared with that in 2003, and the amount of the expanded landslide area corresponding to the initial landslide area. As a result, it is estimated 24% about probability of expansion for each landslide. In addition, each expanded landslide area is smaller than the initial landslide area. Furthermore, the amount of each expanded landslide area in 2008 is approximately 7% of their landslide area in 2003. Therefore, the sediment yield from subsequent expanded landslides is equal to or slightly greater than the sediment yield in a typical base flow. Thus, we concluded that the amount of sediment yield from subsequent expanded landslides is lower than that of initial large-scale sediment yield caused by a heavy rainfall in terms of effect on management of catchment-scale sediment movement.

Parameter Identification and Uncertainty Analysis for Visual MODFLOW based Groundwater Flow Model in a Small River Basin, Eastern India

NASA Astrophysics Data System (ADS)

Jena, S.

2015-12-01

The overexploitation of groundwater resulted in abandoning many shallow tube wells in the river Basin in Eastern India. For the sustainability of groundwater resources, basin-scale modelling of groundwater flow is essential for the efficient planning and management of the water resources. The main intent of this study is to develope a 3-D groundwater flow model of the study basin using the Visual MODFLOW package and successfully calibrate and validate it using 17 years of observed data. The sensitivity analysis was carried out to quantify the susceptibility of aquifer system to the river bank seepage, recharge from rainfall and agriculture practices, horizontal and vertical hydraulic conductivities, and specific yield. To quantify the impact of parameter uncertainties, Sequential Uncertainty Fitting Algorithm (SUFI-2) and Markov chain Monte Carlo (MCMC) techniques were implemented. Results from the two techniques were compared and the advantages and disadvantages were analysed. Nash-Sutcliffe coefficient (NSE) and coefficient of determination (R2) were adopted as two criteria during calibration and validation of the developed model. NSE and R2 values of groundwater flow model for calibration and validation periods were in acceptable range. Also, the MCMC technique was able to provide more reasonable results than SUFI-2. The calibrated and validated model will be useful to identify the aquifer properties, analyse the groundwater flow dynamics and the change in groundwater levels in future forecasts.

The changing hydro-ecological dynamics of rivers and deltas of the Western Indian Ocean: Anthropogenic and environmental drivers, local adaptation and policy response

NASA Astrophysics Data System (ADS)

Duvail, Stéphanie; Hamerlynck, Olivier; Paron, Paolo; Hervé, Dominique; Nyingi, Wanja D.; Leone, Michele

2017-10-01

The rivers flowing into the Western Indian Ocean have steep headwater gradients and carry high sediment loads. In combination with strong tides and seasonal rainfall, these rivers create dynamic deltas with biodiversity-rich and productive ecosystems that, through flooding, have sustained indigenous use systems for centuries. However, river catchments are rapidly changing due to deforestation. Hydropower dams also increasingly alter flood characteristics, reduce sediment supply and contribute to coastal erosion. These impacts are compounded by climate change. Altogether, these changes affect the livelihoods of the delta users. Here, based on prior works that we and others have conducted in the region, we analyse the drivers of these hydro-ecological changes. We then provide recommendations for improved dam design and operations to sustain the underlying delta-building processes, the ecosystem values and the needs of the users.

A simulation for the gated weir opening of Wonokromo River, Rungkut District, Surabaya

NASA Astrophysics Data System (ADS)

Handajani, N.; Wahjudijanto, I.; Mu'afi, M.

2018-01-01

The gated weir is a weir that the crest elevation could be operated based on the flow through the river. The upstream water level of the gated weir could be controlled with gate opening or closing. This study applied a simulation with HEC-RAS 4,0 program in order to know the river hydraulic condition after the gated weir has built. According to the rainfall intensity from each sub-watershed, Distribution Log Pearson III with return period 50 years (Q50) was determined to calculate the design flood discharge. By using Rational Method, the design flood discharge is 470 m3/s. The Results show that capacity of the river is able to accomodate Q50 with discharge 470 m3/s and the gate should be fully opened during flood. This condition could passed the normal discharge at + 5.00 m elevation.

Real-Time Application of Multi-Satellite Precipitation Analysis for Floods and Landslides

NASA Technical Reports Server (NTRS)

Adler, Robert; Hong, Yang; Huffman, George

2007-01-01

Satellite data acquired and processed in real time now have the potential to provide the spacetime information on rainfall needed to monitor flood and landslide events around the world. This can be achieved by integrating the satellite-derived forcing data with hydrological models and landslide algorithms. Progress in using the TRMM Multi-satellite Precipitation Analysis (TMPA) as input to flood and landslide forecasts is outlined, with a focus on understanding limitations of the rainfall data and impacts of those limitations on flood/landslide analyses. Case studies of both successes and failures will be shown, as well as comparison with ground comparison data sets-- both in terms of rainfall and in terms of flood/landslide events. In addition to potential uses in real-time, the nearly ten years of TMPA data allow retrospective running of the models to examine variations in extreme events. The flood determination algorithm consists of four major components: 1) multi-satellite precipitation estimation; 2) characterization of land surface including digital elevation from NASA SRTM (Shuttle Radar Terrain Mission), topography-derived hydrologic parameters such as flow direction, flow accumulation, basin, and river network etc.; 3) a hydrological model to infiltrate rainfall and route overland runoff; and 4) an implementation interface to relay the input data to the models and display the flood inundation results to potential users and decision-makers, In terms of landslides, the satellite rainfall information is combined with a global landslide susceptibility map, derived from a combination of global surface characteristics (digital elevation topography, slope, soil types, soil texture, and land cover classification etc.) using a weighted linear combination approach. In those areas identified as "susceptible" (based on the surface characteristics), landslides are forecast where and when a rainfall intensity/duration threshold is exceeded. Results are described indicating general agreement with landslide occurrences.

Concentrations of dissolved solids and nutrients in water sources and selected streams of the Santa Ana Basin, California, Octoger 1998 - September 2001

USGS Publications Warehouse

Kent, Robert; Belitz, Kenneth

2004-01-01

Concentrations of total dissolved solids (TDS) and nutrients in selected Santa Ana Basin streams were examined as a function of water source. The principal water sources are mountain runoff, wastewater, urban runoff, and stormflow. Rising ground water also enters basin streams in some reaches. Data were collected from October 1998 to September 2001 from 6 fixed sites (including a mountain site), 6 additional mountain sites (including an alpine indicator site), and more than 20 synoptic sites. The fixed mountain site on the Santa Ana River near Mentone appears to be a good representative of reference conditions for water entering the basin. TDS can be related to water source. The median TDS concentration in base-flow samples from mountain sites was 200 mg/L (milligrams per liter). Base-flow TDS concentrations from sites on the valley floor typically ranged from 400 to 600 mg/L; base flow to most of these sites is predominantly treated wastewater, with minor contributions of rising ground water and urban runoff. Sparse data suggest that TDS concentrations in urban runoff are about 300 mg/L. TDS concentrations appear to increase on a downstream gradient along the main stem of the Santa Ana River, regardless of source inputs. The major-ion compositions observed in samples from the different sites can be related to water source, as well as to in-stream processes in the basin. Water compositions from mountain sites are categorized into two groups: one group had a composition close to that of the alpine indicator site high in the watershed, and another group had ionic characteristics closer to those in tributaries on the valley floor. The water composition at Warm Creek, a tributary urban indicator site, was highly variable but approximately intermediate to the compositions of the upgradient mountain sites. Water compositions at the Prado Dam and Imperial Highway sites, located 11 miles apart on the Santa Ana River, were similar to one another and appeared to be a mixture of the waters of the upstream sites, Santa Ana River at MWD Crossing, Cucamonga Creek, and Warm Creek. Rainfall usually dilutes stream TDS concentrations. The median TDS concentration in all storm-event discrete samples was 260 mg/L. The median flow-weighted average TDS concentration for stormflow, based on continuous measurement of specific conductance and hydrograph separation of the continuous discharge record, was 190 mg/L. However, stormflow TDS concentrations were variable, and depended on whether the storm was associated with a relatively small or large rainfall event. TDS concentrations in stormflow associated with relatively small events ranged from about 50 to 600 mg/L with a median of 220 mg/L, whereas concentrations in stormflow associated with relatively large events ranged from about 40 to 300 mg/L with a median of 100 mg/L. From the perspective of water managers, the nutrient species of highest concern in Santa Ana Basin streams is nitrate. Most mountain streams had median base-flow concentrations of nitrate below 0.3 mg/L as nitrogen. Nitrate concentrations in both urban runoff and stormflow were near 1 mg/L, which is close to the level found in rainfall for the region. In fact, results from this study suggest that much of the nitrate load in urban storm runoff comes from rainwater. Nitrate concentrations in the Santa Ana River and its major tributaries are highest downstream from wastewater inputs, where median base-flow concentrations of nitrite+nitrate ranged from about 5 to 7 mg/L. About 4 percent of samples collected from sites receiving treated wastewater had nitrate concentrations greater than 10 mg/L. Rising ground water also appears to have high nitrate concentrations (greater than 10 mg/L) in some reaches of the river. Concentrations of other nitrogen species were much lower than nitrate concentrations in base-flow samples. However, storm events increased concentrations and the proportion of organic nitro

[Estimation of urban non-point source pollution loading and its factor analysis in the Pearl River Delta].

PubMed

Liao, Yi-Shan; Zhuo, Mu-Ning; Li, Ding-Qiang; Guo, Tai-Long

2013-08-01

In the Pearl Delta region, urban rivers have been seriously polluted, and the input of non-point source pollution materials, such as chemical oxygen demand (COD), into rivers cannot be neglected. During 2009-2010, the water qualities at eight different catchments in the Fenjiang River of Foshan city were monitored, and the COD loads for eight rivulet sewages were calculated in respect of different rainfall conditions. Interesting results were concluded in our paper. The rainfall and landuse type played important roles in the COD loading, with greater influence of rainfall than landuse type. Consequently, a COD loading formula was constructed that was defined as a function of runoff and landuse type that were derived SCS model and land use map. Loading of COD could be evaluated and predicted with the constructed formula. The mean simulation accuracy for single rainfall event was 75.51%. Long-term simulation accuracy was better than that of single rainfall. In 2009, the estimated COD loading and its loading intensity were 8 053 t and 339 kg x (hm2 x a)(-1), and the industrial land was regarded as the main source of COD pollution area. The severe non-point source pollution such as COD in Fenjiang River must be paid more attention in the future.

Chemical weathering as a mechanism for the climatic control of bedrock river incision

NASA Astrophysics Data System (ADS)

Murphy, Brendan P.; Johnson, Joel P. L.; Gasparini, Nicole M.; Sklar, Leonard S.

2016-04-01

Feedbacks between climate, erosion and tectonics influence the rates of chemical weathering reactions, which can consume atmospheric CO2 and modulate global climate. However, quantitative predictions for the coupling of these feedbacks are limited because the specific mechanisms by which climate controls erosion are poorly understood. Here we show that climate-dependent chemical weathering controls the erodibility of bedrock-floored rivers across a rainfall gradient on the Big Island of Hawai‘i. Field data demonstrate that the physical strength of bedrock in streambeds varies with the degree of chemical weathering, which increases systematically with local rainfall rate. We find that incorporating the quantified relationships between local rainfall and erodibility into a commonly used river incision model is necessary to predict the rates and patterns of downcutting of these rivers. In contrast to using only precipitation-dependent river discharge to explain the climatic control of bedrock river incision, the mechanism of chemical weathering can explain strong coupling between local climate and river incision.

Hydrological control of large hurricane-induced lahars: evidence from rainfall-runoff modeling, seismic and video monitoring

NASA Astrophysics Data System (ADS)

Capra, Lucia; Coviello, Velio; Borselli, Lorenzo; Márquez-Ramírez, Víctor-Hugo; Arámbula-Mendoza, Raul

2018-03-01

The Volcán de Colima, one of the most active volcanoes in Mexico, is commonly affected by tropical rains related to hurricanes that form over the Pacific Ocean. In 2011, 2013 and 2015 hurricanes Jova, Manuel and Patricia, respectively, triggered tropical storms that deposited up to 400 mm of rain in 36 h, with maximum intensities of 50 mm h -1. The effects were devastating, with the formation of multiple lahars along La Lumbre and Montegrande ravines, which are the most active channels in sediment delivery on the south-southwest flank of the volcano. Deep erosion along the river channels and several marginal landslides were observed, and the arrival of block-rich flow fronts resulted in damages to bridges and paved roads in the distal reaches of the ravines. The temporal sequence of these flow events is reconstructed and analyzed using monitoring data (including video images, seismic records and rainfall data) with respect to the rainfall characteristics and the hydrologic response of the watersheds based on rainfall-runoff numerical simulation. For the studied events, lahars occurred 5-6 h after the onset of rainfall, lasted several hours and were characterized by several pulses with block-rich fronts and a maximum flow discharge of 900 m3 s -1. Rainfall-runoff simulations were performer using the SCS-curve number and the Green-Ampt infiltration models, providing a similar result in the detection of simulated maximum watershed peaks discharge. Results show different behavior for the arrival times of the first lahar pulses that correlate with the simulated catchment's peak discharge for La Lumbre ravine and with the peaks in rainfall intensity for Montegrande ravine. This different behavior is related to the area and shape of the two watersheds. Nevertheless, in all analyzed cases, the largest lahar pulse always corresponds with the last one and correlates with the simulated maximum peak discharge of these catchments. Data presented here show that flow pulses within a lahar are not randomly distributed in time, and they can be correlated with rainfall peak intensity and/or watershed discharge, depending on the watershed area and shape. This outcome has important implications for hazard assessment during extreme hydro-meteorological events, as it could help in providing real-time alerts. A theoretical rainfall distribution curve was designed for Volcán de Colima based on the rainfall and time distribution of hurricanes Manuel and Patricia. This can be used to run simulations using weather forecasts prior to the actual event, in order to estimate the arrival time of main lahar pulses, usually characterized by block-rich fronts, which are responsible for most of the damage to infrastructure and loss of goods and lives.

Experimental Investigation of Rainfall Impact on Overland Flow Driven Erosion Processes and Flow Hydrodynamics on a Steep Hillslope

NASA Astrophysics Data System (ADS)

Tian, P.; Xu, X.; Pan, C.; Hsu, K. L.; Yang, T.

2016-12-01

Few attempts have been made to investigate the quantitative effects of rainfall on overland flow driven erosion processes and flow hydrodynamics on steep hillslopes under field conditions. Field experiments were performed in flows for six inflow rates (q: 6-36 Lmin-1m-1) with and without rainfall (60 mm h-1) on a steep slope (26°) to investigate: (1) the quantitative effects of rainfall on runoff and sediment yield processes, and flow hydrodynamics; (2) the effect of interaction between rainfall and overland flow on soil loss. Results showed that the rainfall increased runoff coefficients and the fluctuation of temporal variations in runoff. The rainfall significantly increased soil loss (10.6-68.0%), but this increment declined as q increased. When the interrill erosion dominated (q=6 Lmin-1m-1), the increment in the rill erosion was 1.5 times that in the interrill erosion, and the effect of the interaction on soil loss was negative. When the rill erosion dominated (q=6-36 Lmin-1m-1), the increment in the interrill erosion was 1.7-8.8 times that in the rill erosion, and the effect of the interaction on soil loss became positive. The rainfall was conducive to the development of rills especially for low inflow rates. The rainfall always decreased interrill flow velocity, decreased rill flow velocity (q=6-24 Lmin-1m-1), and enhanced the spatial uniformity of the velocity distribution. Under rainfall disturbance, flow depth, Reynolds number (Re) and resistance were increased but Froude number was reduced, and lower Re was needed to transform a laminar flow to turbulent flow. The rainfall significantly increased flow shear stress (τ) and stream power (φ), with the most sensitive parameters to sediment yield being τ (R2=0.994) and φ (R2=0.993), respectively, for non-rainfall and rainfall conditions. Compared to non-rainfall conditions, there was a reduction in the critical hydrodynamic parameters of mean flow velocity, τ, and φ by the rainfall. These findings provide a better understanding on the influence mechanism of rainfall impact on hillslope erosion processes.

Hydrological modelling in sandstone rocks watershed

NASA Astrophysics Data System (ADS)

Ponížilová, Iva; Unucka, Jan

2015-04-01

The contribution is focused on the modelling of surface and subsurface runoff in the Ploučnice basin. The used rainfall-runoff model is HEC-HMS comprising of the method of SCS CN curves and a recession method. The geological subsurface consisting of sandstone is characterised by reduced surface runoff and, on the contrary, it contributes to subsurface runoff. The aim of this paper is comparison of the rate of influence of sandstone on reducing surface runoff. The recession method for subsurface runoff was used to determine the subsurface runoff. The HEC-HMS model allows semi- and fully distributed approaches to schematisation of the watershed and rainfall situations. To determine the volume of runoff the method of SCS CN curves is used, which results depend on hydrological conditions of the soils. The rainfall-runoff model assuming selection of so-called methods of event of the SCS-CN type is used to determine the hydrograph and peak flow rate based on simulation of surface runoff in precipitation exceeding the infiltration capacity of the soil. The recession method is used to solve the baseflow (subsurface) runoff. The method is based on the separation of hydrograph to direct runoff and subsurface or baseflow runoff. The study area for the simulation of runoff using the method of SCS CN curves to determine the hydrological transformation is the Ploučnice basin. The Ploučnice is a hydrologically significant river in the northern part of the Czech Republic, it is a right tributary of the Elbe river with a total basin area of 1.194 km2. The average value of CN curves for the Ploučnice basin is 72. The geological structure of the Ploučnice basin is predominantly formed by Mesozoic sandstone. Despite significant initial loss of rainfall the basin response to the causal rainfall was demonstrated by a rapid rise of the surface runoff from the watershed and reached culmination flow. Basically, only surface runoff occures in the catchment during the initial phase of this extreme event. The increase of the baseflow runoff is slower and remains constant after reaching a certain level. The rise of the baseflow runoff is showed in a descending part of the hydrograph. The recession method in this case shows almost 20 hours delay. Results from the HEC-HMS prove availability of both methods for the runoff modeling in this type of catchment. When simulating extreme short-term rainfall-runoff episodes, the influence of geological subsurface is not significant, but it is manifested. Using more relevant rainfall events would bring more satisfactory results.

Improving the performance of streamflow forecasting model using data-preprocessing technique in Dungun River Basin

NASA Astrophysics Data System (ADS)

Khai Tiu, Ervin Shan; Huang, Yuk Feng; Ling, Lloyd

2018-03-01

An accurate streamflow forecasting model is important for the development of flood mitigation plan as to ensure sustainable development for a river basin. This study adopted Variational Mode Decomposition (VMD) data-preprocessing technique to process and denoise the rainfall data before putting into the Support Vector Machine (SVM) streamflow forecasting model in order to improve the performance of the selected model. Rainfall data and river water level data for the period of 1996-2016 were used for this purpose. Homogeneity tests (Standard Normal Homogeneity Test, the Buishand Range Test, the Pettitt Test and the Von Neumann Ratio Test) and normality tests (Shapiro-Wilk Test, Anderson-Darling Test, Lilliefors Test and Jarque-Bera Test) had been carried out on the rainfall series. Homogenous and non-normally distributed data were found in all the stations, respectively. From the recorded rainfall data, it was observed that Dungun River Basin possessed higher monthly rainfall from November to February, which was during the Northeast Monsoon. Thus, the monthly and seasonal rainfall series of this monsoon would be the main focus for this research as floods usually happen during the Northeast Monsoon period. The predicted water levels from SVM model were assessed with the observed water level using non-parametric statistical tests (Biased Method, Kendall's Tau B Test and Spearman's Rho Test).

A Quantitative Analysis of the Effects of Human Activities and Climate Change on Rainfall-Runoff in Xiaoqing River Basin

NASA Astrophysics Data System (ADS)

Yang, Y.; Cao, S.; Liu, C.; Liu, Y.

2017-12-01

It is a hot topic to study the effects of human activities on the rainfall-runoff relationship and quantitatively analyze the influencing factors. According to the flexibility of Copula function to capture multivariate interdependent structure, the Copula structure between rainfall and runoff was analyzed by using the rainfall-runoff variation test method based on Archimedean Copula function to diagnose the variation of rainfall-runoff relationship. The correlation of rainfall-runoff relationship could be directly analyzed by Copula function, which could intuitively display the change of runoff in the same rainfall before and after the mutation period. The statistical method was used to simulate the underlying surface conditions before the abrupt point, and the effects of climate change and human activities on runoff changes were calculated. It can finally figure out the effects of human activities on the rainfall-runoff relationship. Taking xiaoqing river for example, the results showed that the rainfall-runoff relationship in the Xiaoqing River Basin variated in 1996 mainly due to the continuous increase of water consumption in the watershed and the change of the runoff attenuation caused by the large-scale water conservancy projects. And interannual or annual change of rainfall was not obvious; compared with the year before the variation , the runoff capacity of the basin was weakened under the same rainfall conditions after the variation ; Rainfall and runoff distribution were significantly changed and the same magnitude of rainfall and probability of runoff change were significantly different in different periods; The statistical method was used to simulate the runoff from 1996 to 2016. Compared with that from 1960 to 1995, the result showed that the contribution rate of human activities to runoff reduction was 46.8% and that of climate change was 53.2%. By relevant reference, rainfall-runoff correlation and analysis of human activities, the result was verified to be reasonable. The study can be applied to other watersheds, or used to diagnose the variation of the relationship between meteorological elements and hydrological elements so as to provide scientific basis for rational exploitation and utilization of river water resources, as well as soil and water conservation.

Stochastic modeling of hourly rainfall times series in Campania (Italy)

NASA Astrophysics Data System (ADS)

Giorgio, M.; Greco, R.

2009-04-01

Occurrence of flowslides and floods in small catchments is uneasy to predict, since it is affected by a number of variables, such as mechanical and hydraulic soil properties, slope morphology, vegetation coverage, rainfall spatial and temporal variability. Consequently, landslide risk assessment procedures and early warning systems still rely on simple empirical models based on correlation between recorded rainfall data and observed landslides and/or river discharges. Effectiveness of such systems could be improved by reliable quantitative rainfall prediction, which can allow gaining larger lead-times. Analysis of on-site recorded rainfall height time series represents the most effective approach for a reliable prediction of local temporal evolution of rainfall. Hydrological time series analysis is a widely studied field in hydrology, often carried out by means of autoregressive models, such as AR, ARMA, ARX, ARMAX (e.g. Salas [1992]). Such models gave the best results when applied to the analysis of autocorrelated hydrological time series, like river flow or level time series. Conversely, they are not able to model the behaviour of intermittent time series, like point rainfall height series usually are, especially when recorded with short sampling time intervals. More useful for this issue are the so-called DRIP (Disaggregated Rectangular Intensity Pulse) and NSRP (Neymann-Scott Rectangular Pulse) model [Heneker et al., 2001; Cowpertwait et al., 2002], usually adopted to generate synthetic point rainfall series. In this paper, the DRIP model approach is adopted, in which the sequence of rain storms and dry intervals constituting the structure of rainfall time series is modeled as an alternating renewal process. Final aim of the study is to provide a useful tool to implement an early warning system for hydrogeological risk management. Model calibration has been carried out with hourly rainfall hieght data provided by the rain gauges of Campania Region civil protection agency meteorological warning network. ACKNOWLEDGEMENTS The research was co-financed by the Italian Ministry of University, by means of the PRIN 2006 PRIN program, within the research project entitled ‘Definition of critical rainfall thresholds for destructive landslides for civil protection purposes'. REFERENCES Cowpertwait, P.S.P., Kilsby, C.G. and O'Connell, P.E., 2002. A space-time Neyman-Scott model of rainfall: Empirical analysis of extremes, Water Resources Research, 38(8):1-14. Salas, J.D., 1992. Analysis and modeling of hydrological time series, in D.R. Maidment, ed., Handbook of Hydrology, McGraw-Hill, New York. Heneker, T.M., Lambert, M.F. and Kuczera G., 2001. A point rainfall model for risk-based design, Journal of Hydrology, 247(1-2):54-71.

Geochemical Indicators of Nitrogen flow in a Check-Dam Catchment in the Loess Plateau, China

NASA Astrophysics Data System (ADS)

Wang, Y.; Chen, S.; Huang, Y.; Gao, Y.

2017-12-01

The increasingly fragile ecological environment and associative nitrogen (N) biogeochemical cycle have become critical environmental and ecological issues in China's Loess Plateau. However, N flow and N source for typical catchments remains poorly understood in the Loess Plateau. In this study, we measured concentrations and isotopic signatures of N, hydrogen (H), and oxygen (O) in both rainfall and river water. Results showed that baseflow variation in total nitrogen (TN) concentrations ranged from 0.16 to 32.70 mg·L-1. Monthly TN deposition and monthly N wet deposition concentrations to river water were from 0.05 to 2.91 kg·hm-2 and from 0.28 to 11.26 kg, respectively, with significant variations between rainy and dry seasons. The range of variation in δ2H values for rainfall and baseflow were from -90.0‰ to +19.8‰ and from -67.2‰ to -38.4‰, respectively, while δ18O-H2O values ranged from -12.1‰ to +2.7‰ and from -9.3‰ to -3.6‰, respectively. Furthermore, NO3- δ15N and δ18O values in baseflow ranged from -2.0‰ to +20.5‰ and from +8.0‰ to +15.6‰, respectively. The results indicated that rainfall was affected by below-cloud secondary evaporation and caused strong isotopic kinetic fractionation to occur during the falling process. The NO3-in runoff mainly derived from the nitrification of soil organic matter (SOM), for which the proportion of manure or sewage was from 50.5% to 83%.

Temporal pattern of toxicity in runoff from the Tijuana River Watershed.

PubMed

Gersberg, Richard M; Daft, Daniel; Yorkey, Darryl

2004-02-01

Samples were collected from the Tijuana River under both dry weather (baseflow) conditions and during wet weather, and tested for toxicity using Ceriodaphnia dubia tests. Toxicity of waters in the Tijuana River was generally low under baseflow conditions, but increased markedly during high flow runoff events. In order to determine the temporal pattern of toxicity during individual rain events, sequential grab samples were collected using an autosampler at 5-7 h intervals after the start of the rain event, and tested for acute toxicity. In all cases, peak toxicity values (ranging from 2.8 to 5.8TU) for each storm occurred within the first 1-2 h of initiation of the rain event, and were statistically higher (using the 95% CL) for each of the pre-storm base flow values. However, there was no statistically significant correlation (p<0.05) between flow rate and toxicity when all storm data was pooled. Additionally, we used toxicity identification evaluation (TIE) procedures to attempt to identify the classes of chemicals that account for this early storm toxicity. Solid phase extraction was the only treatment that showed consistent and significant (P<0.05) removal of toxicity. These TIEs, conducted on the most toxic sample of the river's flow during runoff events, suggest that non-polar organics may be responsible for such toxicity. The temporal pattern of toxicity, both during a given storm event and seasonally, indicates that wash-off from the watershed by rainfall may deplete the supply of toxicity available for wash-off in subsequent events, so that a clearly consistent relationship between flow and toxicity was not evident.

Estimation of the Probable Maximum Flood for a Small Lowland River in Poland

NASA Astrophysics Data System (ADS)

Banasik, K.; Hejduk, L.

2009-04-01

The planning, designe and use of hydrotechnical structures often requires the assesment of maximu flood potentials. The most common term applied to this upper limit of flooding is the probable maximum flood (PMF). The PMP/UH (probable maximum precipitation/unit hydrograph) method has been used in the study to predict PMF from a small agricultural lowland river basin of Zagozdzonka (left tributary of Vistula river) in Poland. The river basin, located about 100 km south of Warsaw, with an area - upstream the gauge of Plachty - of 82 km2, has been investigated by Department of Water Engineering and Environmenal Restoration of Warsaw University of Life Sciences - SGGW since 1962. Over 40-year flow record was used in previous investigation for predicting T-year flood discharge (Banasik et al., 2003). The objective here was to estimate the PMF using the PMP/UH method and to compare the results with the 100-year flood. A new relation of depth-duration curve of PMP for the local climatic condition has been developed based on Polish maximum observed rainfall data (Ozga-Zielinska & Ozga-Zielinski, 2003). Exponential formula, with the value of exponent of 0.47, i.e. close to the exponent in formula for world PMP and also in the formula of PMP for Great Britain (Wilson, 1993), gives the rainfall depth about 40% lower than the Wilson's one. The effective rainfall (runoff volume) has been estimated from the PMP of various duration using the CN-method (USDA-SCS, 1986). The CN value as well as parameters of the IUH model (Nash, 1957) have been established from the 27 rainfall-runoff events, recorded in the river basin in the period 1980-2004. Varibility of the parameter values with the size of the events will be discussed in the paper. The results of the analyse have shown that the peak discharge of the PMF is 4.5 times larger then 100-year flood, and volume ratio of the respective direct hydrographs caused by rainfall events of critical duration is 4.0. References 1.Banasik K., Byczkowski A., Gładecki J., 2003: Prediction of T-year flood discharge from a small river basin using direct and indirect methods. Annals of Warsaw Agricultural University - SGGW, Land Reclamation, No 34, p. 3 - 8. 2.Nash J.E., 1957. The form of the instantaneous unit hydrograph. Publ. IAHS, nr 59, p.202-213. 3.Ozga-Zielińska M. & Ozga-Zielinski B., 2003. The floodgenerativity of rivers as a measure of danger for hydrotechnical structures and determination of flood protection zones (in Polish with English summary). Gospodarka Wodna, no 1, p. 10-17. 4.Shalaby A.,I., 1995. Sensitivity to probable maximum flood. Journal of Irrigation and Drainage Engineering. Vol. 121, No. 5, p. 327-337. 5.USDA-SCS (Soil Conservation Service), 1986. TR-55: Urban hydrolgy for small watershed. Wasington, D.C. 6.Wilson E.M., 1993. Engineering hydrology. MacMillan, London.

Estimation of the Probable Maximum Flood for a Small Lowland River in Poland

NASA Astrophysics Data System (ADS)

Banasik, K.; Hejduk, L.

2009-04-01

The planning, designe and use of hydrotechnical structures often requires the assesment of maximu flood potentials. The most common term applied to this upper limit of flooding is the probable maximum flood (PMF). The PMP/UH (probable maximum precipitation/unit hydrograph) method has been used in the study to predict PMF from a small agricultural lowland river basin of Zagozdzonka (left tributary of Vistula river) in Poland. The river basin, located about 100 km south of Warsaw, with an area - upstream the gauge of Plachty - of 82 km2, has been investigated by Department of Water Engineering and Environmenal Restoration of Warsaw University of Life Sciences - SGGW since 1962. Over 40-year flow record was used in previous investigation for predicting T-year flood discharge (Banasik et al., 2003). The objective here was to estimate the PMF using the PMP/UH method and to compare the results with the 100-year flood. A new relation of depth-duration curve of PMP for the local climatic condition has been developed based on Polish maximum observed rainfall data (Ozga-Zielinska & Ozga-Zielinski, 2003). Exponential formula, with the value of exponent of 0.47, i.e. close to the exponent in formula for world PMP and also in the formula of PMP for Great Britain (Wilson, 1993), gives the rainfall depth about 40% lower than the Wilson's one. The effective rainfall (runoff volume) has been estimated from the PMP of various duration using the CN-method (USDA-SCS, 1986). The CN value as well as parameters of the IUH model (Nash, 1957) have been established from the 27 rainfall-runoff events, recorded in the river basin in the period 1980-2004. Varibility of the parameter values with the size of the events will be discussed in the paper. The results of the analyse have shown that the peak discharge of the PMF is 4.5 times larger then 100-year flood, and volume ratio of the respective direct hydrographs caused by rainfall events of critical duration is 4.0. References 1.Banasik K., Byczkowski A., Gładecki J., 2003: Prediction of T-year flood discharge from a small river basin using direct and indirect methods. Annals of Warsaw Agricultural University - SGGW, Land Reclamation, No 34, p. 3 - 8. 2.Nash J.E., 1957. The form of the instantaneous unit hydrograph. Publ. IAHS, nr 59, p.202-213. 3.Ozga-Zielińska M. & Ozga-Zielinski B., 2003. The floodgenerativity of rivers as a measure of danger for hydrotechnical structures and determination of flood protection zones (in Polish with English summary). Gospodarka Wodna, no 1, p. 10-17. 4.Shalaby A.,I., 1995. Sensitivity to probable maximum flood. Journal of Irrigation and Drainage Engineering. Vol. 121, No. 5, p. 327-337. 5.USDA-SCS (Soil Conservation Service), 1986. TR-55: Urban hydrolgy for small watershed. Wasington, D.C. 6. Wilson E.M., 1993. Engineering hydrology. MacMillan, London.

Synthetic generation of spatially high resolution extreme rainfall in Japan using Monte Carlo simulation with AMeDAS analyzed rainfall data sets

NASA Astrophysics Data System (ADS)

Haruki, W.; Iseri, Y.; Takegawa, S.; Sasaki, O.; Yoshikawa, S.; Kanae, S.

2016-12-01

Natural disasters caused by heavy rainfall occur every year in Japan. Effective countermeasures against such events are important. In 2015, a catastrophic flood occurred in Kinu river basin, which locates in the northern part of Kanto region. The remarkable feature of this flood event was not only in the intensity of rainfall but also in the spatial characteristics of heavy rainfall area. The flood was caused by continuous overlapping of heavy rainfall area over the Kinu river basin, suggesting consideration of spatial extent is quite important to assess impacts of heavy rainfall events. However, the spatial extent of heavy rainfall events cannot be properly measured through rainfall measurement by rain gauges at observation points. On the other hand, rainfall measurements by radar observations provide spatially and temporarily high resolution rainfall data which would be useful to catch the characteristics of heavy rainfall events. For long term effective countermeasure, extreme heavy rainfall scenario considering rainfall area and distribution is required. In this study, a new method for generating extreme heavy rainfall events using Monte Carlo Simulation has been developed in order to produce extreme heavy rainfall scenario. This study used AMeDAS analyzed precipitation data which is high resolution grid precipitation data made by Japan Meteorological Agency. Depth area duration (DAD) analysis has been conducted to extract extreme rainfall events in the past, considering time and spatial scale. In the Monte Carlo Simulation, extreme rainfall event is generated based on events extracted by DAD analysis. Extreme heavy rainfall events are generated in specific region in Japan and the types of generated extreme heavy rainfall events can be changed by varying the parameter. For application of this method, we focused on Kanto region in Japan. As a result, 3000 years rainfall data are generated. 100 -year probable rainfall and return period of flood in Kinu River Basin (2015) are obtained using generated data. We compared 100-year probable rainfall calculated by this method with other traditional method. New developed method enables us to generate extreme rainfall events considering time and spatial scale and produce extreme rainfall scenario.

Rainfall characteristics and thresholds for periglacial debris flows in the Parlung Zangbo Basin, southeast Tibetan Plateau

NASA Astrophysics Data System (ADS)

Deng, Mingfeng; Chen, Ningsheng; Ding, Haitao

2018-02-01

The Parlung Zangbo Basin in the southeastern Tibet Plateau is affected by the summer monsoon from the Indian Ocean, which produces large rainfall gradients in the basin. Rainfall data during 2012-2015 from five new meteorological stations are used to analyse the rainfall characteristics. The daily rainfall, rainfall duration, mean rainfall intensity, and peak rainfall intensity are consistent, but sometimes contrasting. For example, these values decrease with increasing altitude, and the gradient is large downstream and small upstream, respectively. Moreover, the rainfall intensity peaks between 01:00 and 06:00 and increases during the afternoon. Based on the analysis of 14 debris flow cases in the basin, differences in the rainfall threshold differ depending on the location as sediment varieties. The sediment in the middle portions of the basin is wet and well structured; thus, long-duration, high-intensity rainfall is required to generate debris flows. Ravels in the upstream area are arid and not well structured, and short-duration rainfall is required to trigger debris flows. Between the above two locations, either long-duration, low-intensity rainfall or short-duration, high-intensity rainfall could provoke debris flows. Clearly, differences in rainfall characteristics and rainfall thresholds that are associated with the location must be considered in debris flow monitoring and warnings.

Evidence of an emerging levee failure mechanism causing disastrous floods in Italy

NASA Astrophysics Data System (ADS)

Orlandini, Stefano; Moretti, Giovanni; Albertson, John D.

2015-10-01

A levee failure occurred along the Secchia River, Northern Italy, on 19 January 2014, resulting in flood damage in excess of $500 million. In response to this failure, immediate surveillance of other levees in the region led to the identification of a second breach developing on the neighboring Panaro River, where rapid mitigation efforts were successful in averting a full levee failure. The paired breach events that occurred along the Secchia and Panaro Rivers provided an excellent window on an emerging levee failure mechanism. In the Secchia River, by combining the information content of photographs taken from helicopters in the early stage of breach development and 10 cm resolution aerial photographs taken in 2010 and 2012, animal burrows were found to exist in the precise levee location where the breach originated. In the Panaro River, internal erosion was observed to occur at a location where a crested porcupine den was known to exist and this erosion led to the collapse of the levee top. This paper uses detailed numerical modeling of rainfall, river flow, and variably saturated flow in the levee to explore the hydraulic and geotechnical mechanisms that were triggered along the Secchia and Panaro Rivers by activities of burrowing animals leading to levee failures. As habitats become more fragmented and constrained along river corridors, it is possible that this failure mechanism could become more prevalent and, therefore, will demand greater attention in both the design and maintenance of earthen hydraulic structures as well as in wildlife management.

Evidence of an emerging levee failure mechanism causing disastrous floods in Italy

NASA Astrophysics Data System (ADS)

Orlandini, Stefano; Moretti, Giovanni; Albertson, John

2017-04-01

A levee failure occurred along the Secchia River, Northern Italy, on January 19, 2014, resulting in flood damage in excess of 500 Million. In response to this failure, immediate surveillance of other levees in the region led to the identification of a second breach developing on the neighboring Panaro River, where rapid mitigation efforts were successful in averting a full levee failure. The paired breach events that occurred along the Secchia and Panaro Rivers provided an excellent window on an emerging levee failure mechanism. In the Secchia River, by combining the information content of photographs taken from helicopters in the early stage of breach development and 10-cm resolution aerial photographs taken in 2010 and 2012, animal burrows were found to exist in the precise levee location where the breach originated. In the Panaro River, internal erosion was observed to occur at a location where a crested porcupine den was known to exist and this erosion led to the collapse of the levee top. This paper uses detailed numerical modeling of rainfall, river flow, and variably saturated flow in the levee to explore the hydraulic and geotechnical mechanisms that were triggered along the Secchia and Panaro Rivers by activities of burrowing animals leading to levee failures. As habitats become more fragmented and constrained along river corridors it is possible that this failure mechanism could become more prevalent and, therefore, will demand greater attention in both the design and maintenance of earthen hydraulic structures as well as in wildlife management.

Hydrogeology of the western part of the Salt River Valley area, Maricopa County, Arizona

USGS Publications Warehouse

Brown, James G.; Pool, D.R.

1989-01-01

The Salt River Valley is a major population and agricultural center of more than 3,000 mi2 in central Arizona (fig. 1). The western part of the Salt River Valley area (area of this report) covers about 1,500 mi2. The Phoenix metropolitan area with a population of more than 1.6 million in 1985 (Valley National Bank, 1987) is located within the valley. The watersheds of the Salt, Verde, and Agua Fria Rivers provide the valley with a reliable but limited surface-water supply that must be augmented with ground water even in years of plentiful rainfall. Large-scale ground-water withdrawals began in the Salt River Valley in the early part of the 20th century; between 1915 and 1983, the total estimated ground-water pumpage was 81 million acre-ft (U.S. Geological Survey, 1984). Because of the low average annual rainfall and high potential evapotranspiration, the principal sources of ground-water recharge are urban runoff, excess irrigation, canal seepage and surface-water flows during years of higher-than-normal rainfall. Withdrawals greatly exceed recharge and, in some area, ground-water levels have declines as much as 350 ft (Laney and other, 1978; Ross, 1978). In the study area, ground-water declines of more than 300 ft have occurred in Deer Valley and from Luke Air Force Base north to Beardsley. As a result, a large depression of the water table has developed west of Luke Air Force Base (fig. 2). Ground-water use has decreased in recent years because precipitation and surface-water supplies have been greater than normal. Increased precipitation also caused large quantities of runoff to be released into the normally dry Salt and Gila River channels. From February 1978 to June 1980, streamflow losses of at least 90,000 acre-ft occurred between Jointhead Dam near the east boundary of the study area and Gillespie Dam several miles southwest of the west edge of the study area (Mann and Rhone, 1983). Consequently, ground-water declines in a large part of the basin have slowed, and ground-water levels in some sarea have risen significantly. In many areas along the Salt River and northeast of the confluence of the Salt and Agua Fria River, ground-water levels rose more than 25 ft between 1978 and 1984 (Reeter and Remick, 1986).

Series of Storms Battering California Tracked by NASA AIRS Instrument

NASA Image and Video Library

2017-01-13

A series of atmospheric rivers that brought drought-relieving rains, heavy snowfall and flooding to California this week is highlighted in a new movie created with satellite data from the Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua satellite. The images of atmospheric water vapor were collected by AIRS between January 7 and 11. They show the amount of moisture present in the atmosphere and its movement across the Pacific Ocean to the United States, where much of it fell as rain or snow. In early January 2017, the Western U.S. experienced rain and flooding from a series of storms flowing to America on multiple streams of moist air, each individually known as an atmospheric river. Atmospheric rivers are typically 250 to 375 miles (400 to 600 kilometers) wide. The term "Pineapple Express" refers to atmospheric rivers that originate near or just east of the Hawaiian Islands and terminate along the West Coast of North America. Other atmospheric rivers originate in the tropical Western Pacific Ocean and take on a more west-to-east orientation near the U.S. West Coast. Several distinct plumes of moisture are apparent in the AIRS imagery. The first of three atmospheric river events occurred on January 7 and 8. This was a classic Pineapple Express, featuring an uninterrupted supply of heavy moisture drawn up from the deep tropics. This was the wettest storm of the series, producing very heavy rainfall, more than 1 foot (0.3 meter), in parts of Central and Northern California, with relatively smaller amounts of snow at the highest elevations of the Sierra Nevada. The second blob of heavy moisture, from January 8 to 10 to the west of California, likely originated thousands of miles to the west, in the tropical Western Pacific. This atmospheric river did not maintain its tropical connection. However, it still produced prodigious rainfall totals in Northern California and much more snow than the first event, since the storm had a more northern and colder trajectory. A third storm, the coldest of the three events, moved through California on January 11 and 12, producing significant rainfall, as well as snow at higher elevations. The movie ends with another atmospheric river attempting to form on January 11 and 12 to the west of Hawaii, transporting moisture into the storm track. Movies are availalbe at http://photojournal.jpl.nasa.gov/catalog/PIA21209

Streamflow profile classification using functional data analysis: A case study on the Kelantan River Basin

NASA Astrophysics Data System (ADS)

Jamaludin, Suhaila

2017-05-01

Extreme rainfall events such as floods and prolonged dry spells have become common phenomena in tropical countries like Malaysia. Floods are regular natural disasters in Malaysia, and happen nearly every year during the monsoon season. Recently, the magnitude of streamflow seems to have altered frequently, both spatially and temporally. Therefore, in order to have effective planning and an efficient water management system, it is advisable that streamflow data are analysed continuously over a period of time. If the data are treated as a set of functions rather than as a set of discrete values, then this ensures that they are not restricted by physical time. In addition, the derivatives of the functions may themselves be treated as functional data, which provides new information. The objective of this study is to develop a functional framework for hydrological applications using streamflow as the functional data. The daily flow series from the Kelantan River Basin were used as the main input in this study. Seven streamflow stations were employed in the analysis. Classification between the stations was done using the functional principal component, which was based on the results of the factor scores. The results indicated that two stations, namely the Kelantan River (Guillemard Bridge) and the Galas River, have a different flow pattern from the other streamflow stations. The flow curves of these two rivers are considered as the extreme curves because of their different magnitude and shape.

Characterising the hydrological regime of an ungauged temporary river system: a case study.

PubMed

D'Ambrosio, Ersilia; De Girolamo, Anna Maria; Barca, Emanuele; Ielpo, Pierina; Rulli, Maria Cristina

2017-06-01

Temporary streams are characterised by specific hydrological regimes, which influence ecosystem processes, groundwater and surface water interactions, sediment regime, nutrient delivery, water quality and ecological status. This paper presents a methodology to characterise and classify the regime of a temporary river in Southern Italy based on hydrological indicators (HIs) computed with long-term daily flow records. By using a principal component analysis (PCA), a set of non-redundant indices were identified describing the main characteristics of the hydrological regime in the study area. The indicators identified were the annual maximum 30- and 90-day mean (DH4 and DH5), the number of zero flow days (DL6), flow permanence (MF) and the 6-month seasonal predictability of dry periods (SD6). A methodology was also tested to estimate selected HIs in ungauged river reaches. Watershed characteristics such as catchment area, gauging station elevation, mean watershed slope, mean annual rainfall, land use, soil hydraulic conductivity and available water content were derived for each site. Selected indicators were then linked to the catchment characteristics using a regression analysis. Finally, MF and SD6 were used to classify the river reaches on the basis of their degree of intermittency. The methodology presented in this paper constitutes a useful tool for ecologists and water resource managers in the Water Framework Directive implementation process, which requires a characterisation of the hydrological regime and a 'river type' classification for all water bodies.

Importance of measuring discharge and sediment transport in lesser tributaries when closing sediment budgets

NASA Astrophysics Data System (ADS)

Griffiths, Ronald E.; Topping, David J.

2017-11-01

Sediment budgets are an important tool for understanding how riverine ecosystems respond to perturbations. Changes in the quantity and grain size distribution of sediment within river systems affect the channel morphology and related habitat resources. It is therefore important for resource managers to know if a river reach is in a state of sediment accumulation, deficit or stasis. Many sediment-budget studies have estimated the sediment loads of ungaged tributaries using regional sediment-yield equations or other similar techniques. While these approaches may be valid in regions where rainfall and geology are uniform over large areas, use of sediment-yield equations may lead to poor estimations of loads in regions where rainfall events, contributing geology, and vegetation have large spatial and/or temporal variability. Previous estimates of the combined mean-annual sediment load of all ungaged tributaries to the Colorado River downstream from Glen Canyon Dam vary by over a factor of three; this range in estimated sediment loads has resulted in different researchers reaching opposite conclusions on the sign (accumulation or deficit) of the sediment budget for particular reaches of the Colorado River. To better evaluate the supply of fine sediment (sand, silt, and clay) from these tributaries to the Colorado River, eight gages were established on previously ungaged tributaries in Glen, Marble, and Grand canyons. Results from this sediment-monitoring network show that previous estimates of the annual sediment loads of these tributaries were too high and that the sediment budget for the Colorado River below Glen Canyon Dam is more negative than previously calculated by most researchers. As a result of locally intense rainfall events with footprints smaller than the receiving basin, floods from a single tributary in semi-arid regions can have large (≥ 10 ×) differences in sediment concentrations between equal magnitude flows. Because sediment loads do not necessarily correlate with drainage size, and may vary by two orders of magnitude on an annual basis, using techniques such as sediment-yield equations to estimate the sediment loads of ungaged tributaries may lead to large errors in sediment budgets.

Importance of measuring discharge and sediment transport in lesser tributaries when closing sediment budgets

USGS Publications Warehouse

Griffiths, Ronald; Topping, David

2017-01-01

Sediment budgets are an important tool for understanding how riverine ecosystems respond to perturbations. Changes in the quantity and grain size distribution of sediment within river systems affect the channel morphology and related habitat resources. It is therefore important for resource managers to know if a river reach is in a state of sediment accumulation, deficit or stasis. Many sediment-budget studies have estimated the sediment loads of ungaged tributaries using regional sediment-yield equations or other similar techniques. While these approaches may be valid in regions where rainfall and geology are uniform over large areas, use of sediment-yield equations may lead to poor estimations of loads in regions where rainfall events, contributing geology, and vegetation have large spatial and/or temporal variability.Previous estimates of the combined mean-annual sediment load of all ungaged tributaries to the Colorado River downstream from Glen Canyon Dam vary by over a factor of three; this range in estimated sediment loads has resulted in different researchers reaching opposite conclusions on the sign (accumulation or deficit) of the sediment budget for particular reaches of the Colorado River. To better evaluate the supply of fine sediment (sand, silt, and clay) from these tributaries to the Colorado River, eight gages were established on previously ungaged tributaries in Glen, Marble, and Grand canyons. Results from this sediment-monitoring network show that previous estimates of the annual sediment loads of these tributaries were too high and that the sediment budget for the Colorado River below Glen Canyon Dam is more negative than previously calculated by most researchers. As a result of locally intense rainfall events with footprints smaller than the receiving basin, floods from a single tributary in semi-arid regions can have large (≥ 10 ×) differences in sediment concentrations between equal magnitude flows. Because sediment loads do not necessarily correlate with drainage size, and may vary by two orders of magnitude on an annual basis, using techniques such as sediment-yield equations to estimate the sediment loads of ungaged tributaries may lead to large errors in sediment budgets.

Analysis the flash floods occurred in the South Tyne river watershed (United Kingdom) on the 17th of July 2007

NASA Astrophysics Data System (ADS)

Bain, V.; Milan, D.; Preciso, E.; Gaume, E.

2009-04-01

On the 17th, 19th and 23rd of July 2007, a series of local thunderstorms induced flash floods in the upper part of the South Tyne river in Northumberland, a rural area located near the border between England and Scotland. These events led to moderate damages in the villages and losses of livestock in local farms. They were shadowed in comparison to the widespread lowland floods that occurred throughout the UK during the same period but were nevertheless extreme events for the region. One of the affected streams, the Thinhope Burn, has been surveyed by the University of Gloucestershire during recent years. It is an active river from a geomorphological point of view. A survey conducted after the 2007 flood revealed that many of the boulders along the banks of the river, which had been deposited 50 to 100 years before, had been displaced, indicating a high return period for the flood (see EGU abstract EGU2008-A-04713). A complementary survey was conducted in July 2008 with the objective of gathering information on the discharges, the rainfall amounts and the active runoff processes. 14 cross-sections were surveyed, pictures were collected enabling a validation of peak discharge estimates, 5 witnesses were interviewed and additional rainfall data and geomorphological evidence were collected. This survey revealed that the peak discharges exceeded 5 m3/s/km2 in the most affected areas. Unfortunately, no rainfall measurements are available that would enable further analysis, including the computation of runoff rates. Nevertheless, witness accounts and field observations give a good insight into the hydrological processes indicating a significant initial storage capacity of the peat layer covering the affected watersheds. Concerning the boulders, the field observations suggest surprising and unexplained transport processes. Blocks of up to one meter diameter were displaced over short distances and deposited on the river banks without any sign of established debris flow, as if short debris pulses occurred along the river course. This work is conducted within the European research project HYDRATE (Contract GOCE 037024).

Modeling of the Contaminated Sediment in the Erft River

NASA Astrophysics Data System (ADS)

Hu, Wei; Westrich, Bernhard; Rode, Michael

2010-05-01

Sediment transport processes play an important role in the surface water systems coupled with rainfall-runoff and contaminant transport. Pollutants like heavy metals adsorbed mainly by fine sediment particles can be deposited, eroded or transported further downstream. When the toxic pollutants deposited before and covered by cleaner sediment are remobilized by large flow events such as floods, they pose a hidden threat to the human health and environment. In the Erft River, due to mining activities in the past, the heavy metals release from the tributary Veybach on the downstream water and sediment quality is significant. Recent measurements prove the decreasing concentration trend of heavy metals in the river bed sediment from the Veybach. One-dimensional hydrodynamic model COSMOS is used to model the complicated water flow, sediment erosion, deposition and contaminant mixing and transport in the mainstream of the Erft River. It is based on a finite-difference formulation and consists of one-dimensional, unsteady sub-model of flow and transport, coupled with a sub-model of the layered sediment bed. The model accounts for the following governing physical-chemical processes: convective and dispersive transport, turbulent mixing deposited sediment surface, deposition, consolidation, aging and erosion of sediment, adsorption-desorption of pollutants to suspended particles and losses of pollutants due to decay or volatilization. The results reproduce the decreasing profile of the pollutant concentration in the river bed sediment nicely. Further modeling is to analysis the influence of the mixing process at the water-riverbed interface on the contaminant transport, hydrological scenarios impact on the remobilization of the sink of pollutant and its negative consequences on the river basin.

Estimation of Stream Flow Losses to the Highland Lakes Inflows during the Recent Period of Run-off Non-stationarity

NASA Astrophysics Data System (ADS)

Anderson, R.; Rose, B.; Oliver, L.

2015-12-01

The Highland Lakes are operated by the Lower Colorado River Authority (LCRA) in Texas to provide water supply to municipal, industrial, agricultural users and environmental flows for the river and Matagorda Bay. The Highland Lakes also provide for hydroelectric generation and recreation. Subject to extended droughts interrupted by intense rainfall, the region has the nickname of Flash Flood Alley. Recently the Lower Colorado River has experienced a seven year historic drought. While precipitation have been 80% of average, runoff into the Highland lakes have been at historic lows. Multiple regression relationships were developed to predict runoff to the LCRA lakes from rainfall and other factors which explain about 2/3 of the variation of observed inflows. This explanation is good considering the inherent error in stream flow measurement and inflow estimation. It is also comparable to the skill of much more complex dynamical models. Review of the residuals from the relationships reveals periods of unfavorable non-stationarity in inflows after accounting for statistically significant climate and seasonality variables. In particular the periods from 1977 to 1987 as well as 2002 to present showed uncharacteristically low runoff as can be seen in the figure below. Through use of dummy variables for the periods of apparent non-stationarity, the effects of climate and non-stationarity can be quantitatively estimated. At a 90% confidence level, the excess losses in run-off from 2002 to 2015 that can be attributed to lower than median rainfall ranges from 101,000 to 137,000 acre-feet. About another 32,200 to 45,300 acre-feet annually of unrealized inflows can be attributed to typical drought processes. Finally, about another 182,000 to 478,000 acre-feet per year of unrealized inflows can be attributed to unexplained factors in this recent period. These losses are in contrast to runoff during the calendar year of 2011 in which low runoff was better described by extreme climatic conditions. While the statistical significant variables of the exceptional conditions allows estimation of the impacts of non-stationarity, it does not identify a specific cause. Additional research is needed to understand the drivers of these periods of non-stationarity and the return to typical conditions.

Event-based rainfall-runoff modelling of the Kelantan River Basin

NASA Astrophysics Data System (ADS)

Basarudin, Z.; Adnan, N. A.; Latif, A. R. A.; Tahir, W.; Syafiqah, N.

2014-02-01

Flood is one of the most common natural disasters in Malaysia. According to hydrologists there are many causes that contribute to flood events. The two most dominant factors are the meteorology factor (i.e climate change) and change in land use. These two factors contributed to floods in recent decade especially in the monsoonal catchment such as Malaysia. This paper intends to quantify the influence of rainfall during extreme rainfall events on the hydrological model in the Kelantan River catchment. Therefore, two dynamic inputs were used in the study: rainfall and river discharge. The extreme flood events in 2008 and 2004 were compared based on rainfall data for both years. The events were modeled via a semi-distributed HEC-HMS hydrological model. Land use change was not incorporated in the study because the study only tries to quantify rainfall changes during these two events to simulate the discharge and runoff value. Therefore, the land use data representing the year 2004 were used as inputs in the 2008 runoff model. The study managed to demonstrate that rainfall change has a significant impact to determine the peak discharge and runoff depth for the study area.

Comparison of Conventional and ANN Models for River Flow Forecasting

NASA Astrophysics Data System (ADS)

Jain, A.; Ganti, R.

2011-12-01

Hydrological models are useful in many water resources applications such as flood control, irrigation and drainage, hydro power generation, water supply, erosion and sediment control, etc. Estimates of runoff are needed in many water resources planning, design development, operation and maintenance activities. River flow is generally estimated using time series or rainfall-runoff models. Recently, soft artificial intelligence tools such as Artificial Neural Networks (ANNs) have become popular for research purposes but have not been extensively adopted in operational hydrological forecasts. There is a strong need to develop ANN models based on real catchment data and compare them with the conventional models. In this paper, a comparative study has been carried out for river flow forecasting using the conventional and ANN models. Among the conventional models, multiple linear, and non linear regression, and time series models of auto regressive (AR) type have been developed. Feed forward neural network model structure trained using the back propagation algorithm, a gradient search method, was adopted. The daily river flow data derived from Godavari Basin @ Polavaram, Andhra Pradesh, India have been employed to develop all the models included here. Two inputs, flows at two past time steps, (Q(t-1) and Q(t-2)) were selected using partial auto correlation analysis for forecasting flow at time t, Q(t). A wide range of error statistics have been used to evaluate the performance of all the models developed in this study. It has been found that the regression and AR models performed comparably, and the ANN model performed the best amongst all the models investigated in this study. It is concluded that ANN model should be adopted in real catchments for hydrological modeling and forecasting.

Phytoplankton bloom in Spencer Gulf, South Australia

NASA Technical Reports Server (NTRS)

2002-01-01

Summer in southern Australia is the dry season, and in this true-color MODIS image of South Australia and the Spencer Gulf from October 20,2001, the area's vegetation is losing much of the lushness it possessed in the winter rainy season (See image from September 19, 2001). In southern hemisphere summer, the high pressure systems that dominate the continent's weather move south, and block the rain-bearing westerly winds. The resulting changes in seasonal rainfall are extreme. Many of the rivers are impermanent, and flow into dry or impermanent salt lakes, such as Lake Torrens (long, thin lake bed, roughly in the center of the image), and Lake Eyre (pink and white lake bed to the northwest of Torrens). Between the Eyre Peninsula (lower left) and the Yorke Peninsula further east lies the Spencer Gulf, showing the blue-green swirls that indicate a phytoplankton bloom. Australia gets less rainfall than any continent except Antarctica, and the low and seasonal flows contribute to problems with salinity and algal blooms in the continent's surface waters.

Dynamics of an experimental unconfined aquifer

NASA Astrophysics Data System (ADS)

Lajeunesse, E.; Guérin, A.; Devauchelle, O.

2015-12-01

During a rain event, water infiltrates into the ground where it flows slowly towards rivers. We use a tank filled with glass beads to simulate this process in a simplified laboratory experiment. A sprinkler pipe generates rain, which infiltrates into the porous material. Groundwater exits this laboratory aquifer through one side of the tank. The resulting water discharge increases rapidly during rainfall, and decays slowly after the rain has stopped.A theoretical analysis based on Darcy's law and the shallow-water approximation reveals two asymptotic regimes. At the beginning of a rain event, the water discharge increases linearly with time, with a slope proportional to the rainfall rate at the power of 3/2. Long after the rain has stopped, it decreases as the inverse time squared, as predicted by Polubarinova-Kochina (1962). These predictions compare well against our experimental data.Field measurements from two distinct catchments exhibit the same asymptotic behaviours as our experiment. This observation suggests that, despite the simplicity of the setup, our experimental results could be extended to natural groundwater flows.

Salinity of the Delaware Estuary

USGS Publications Warehouse

Cohen, Bernard; McCarthy, Leo T.

1962-01-01

The purpose of this investigation was to obtain data on and study the factors affecting the salinity of the Delaware River from Philadelphia, Pa., to the Appoquinimink River, Del. The general chemical quality of water in the estuary is described, including changes in salinity in the river cross section and profile, diurnal and seasonal changes, and the effects of rainfall, sea level, and winds on salinity. Relationships are established of the concentrations of chloride and dissolved solids to specific conductance. In addition to chloride profiles and isochlor plots, time series are plotted for salinity or some quantity representing salinity, fresh-water discharge, mean river level, and mean sea level. The two major variables which appear to have the greatest effect on the salinity of the estuary are the fresh-water flow of the river and sea level. The most favorable combination of these variables for salt-water encroachment occurs from August to early October and the least favorable combination occurs between December and May.

A web-based Tamsui River flood early-warning system with correction of real-time water stage using monitoring data

NASA Astrophysics Data System (ADS)

Liao, H. Y.; Lin, Y. J.; Chang, H. K.; Shang, R. K.; Kuo, H. C.; Lai, J. S.; Tan, Y. C.

2017-12-01

Taiwan encounters heavy rainfalls frequently. There are three to four typhoons striking Taiwan every year. To provide lead time for reducing flood damage, this study attempt to build a flood early-warning system (FEWS) in Tanshui River using time series correction techniques. The predicted rainfall is used as the input for the rainfall-runoff model. Then, the discharges calculated by the rainfall-runoff model is converted to the 1-D river routing model. The 1-D river routing model will output the simulating water stages in 487 cross sections for the future 48-hr. The downstream water stage at the estuary in 1-D river routing model is provided by storm surge simulation. Next, the water stages of 487 cross sections are corrected by time series model such as autoregressive (AR) model using real-time water stage measurements to improve the predicted accuracy. The results of simulated water stages are displayed on a web-based platform. In addition, the models can be performed remotely by any users with web browsers through a user interface. The on-line video surveillance images, real-time monitoring water stages, and rainfalls can also be shown on this platform. If the simulated water stage exceeds the embankments of Tanshui River, the alerting lights of FEWS will be flashing on the screen. This platform runs periodically and automatically to generate the simulation graphic data of flood water stages for flood disaster prevention and decision making.

Statistical analysis of trends in monthly precipitation at the Limbang River Basin, Sarawak (NW Borneo), Malaysia

NASA Astrophysics Data System (ADS)

Krishnan, M. V. Ninu; Prasanna, M. V.; Vijith, H.

2018-05-01

Effect of climate change in a region can be characterised by the analysis of rainfall trends. In the present research, monthly rainfall trends at Limbang River Basin (LRB) in Sarawak, Malaysia for a period of 45 years (1970-2015) were characterised through the non-parametric Mann-Kendall and Spearman's Rho tests and relative seasonality index. Statistically processed monthly rainfall of 12 well distributed rain gauging stations in LRB shows almost equal amount of rainfall in all months. Mann-Kendall and Spearman's Rho tests revealed a specific pattern of rainfall trend with a definite boundary marked in the months of January and August with positive trends in all stations. Among the stations, Limbang DID, Long Napir and Ukong showed positive (increasing) trends in all months with a maximum increase of 4.06 mm/year (p = 0.01) in November. All other stations showed varying trends (both increasing and decreasing). Significant (p = 0.05) decreasing trend was noticed in Ulu Medalam and Setuan during September (- 1.67 and - 1.79 mm/year) and October (- 1.59 and - 1.68 mm/year) in Mann-Kendall and Spearman's Rho tests. Spatial pattern of monthly rainfall trends showed two clusters of increasing rainfalls (maximas) in upper and lower part of the river basin separated with a dominant decreasing rainfall corridor. The results indicate a generally increasing trend of rainfall in Sarawak, Borneo.

Scarcity of Fresh Water Resources in the Ganges Delta of Bangladesh

NASA Astrophysics Data System (ADS)

Murshed, S. B.; Kaluarachchi, J. J.

2017-12-01

The Ganges Delta in Bangladesh is a classical example of water insecurity in a transboundary river basin where limitations in quantity, quality and timing of available water is producing disastrous conditions. Two opposite extreme water conditions, i.e., fresh water scarcity and floods are common in this region during dry and wet seasons, respectively. The purpose of this study is to manage fresh water requirement of people and environment considering the seasonal availability of surface water (SW) and ground water (GW). SW availability was analyzed by incoming stream flow including the effects of upstream water diversion, rainfall, temperature, evapotranspiration (ET). Flow duration curves (FDC), and rainfall and temperature elasticity are used to assess the change of incoming upstream flow. Groundwater data were collected from 285 piezometers and monitoring wells established by Bangladesh water development board. Variation of groundwater depth shows major withdrawals of GW are mostly concentrated in the north part of the study area. Irrigation is the largest sector of off-stream (irrigation, industrial and domestic) water use which occupies 82% SW and 17% GW of total water consumption. Although domestic water use is entirely depend on GW but arsenic pollution is limiting the GW use. FDC depicts a substantial difference between high flow threshold (20%) and low flow threshold (70%) in the Bangladesh part of Ganges River. A large variation of around 83% is observed for instream water volume between wet and dry seasons. The reduction of upstream fresh water flow increased the extent and intensity of salinity intrusion. Presently GW is also contaminated by saline water. This fresh water scarcity is reducing the livelihood options considerably and indirectly forcing population migration from the delta region. This study provides insight to the changes in hydrology and limitations to freshwater availability enabling better formulation of water resources management in the region.

Floods in southwest-central Florida from hurricane Frances, September 2004

USGS Publications Warehouse

Kane, Richard L.

2005-01-01

Hurricane Frances brought heavy rainfall and widespread flooding to southwest-central Florida September 4-14, 2004. The center of Hurricane Frances made landfall on the east coast of Florida on September 5 as a category 2 hurricane on the Saffir-Simpson scale, then moved west-northwestward through central Florida before exiting Pasco County into the Gulf of Mexico on September 6 (fig. 1; National Weather Service, 2004). The hurricane moved across the Florida Peninsula generating 5 to 11 inches of rain over already saturated ground (table 1). Record flooding occurred in parts of Hardee, Hillsborough, Pasco, and Polk Counties (fig. 1). The hurricane and resulting floods caused an estimated $4-5 billion in damage to public and private property (Harrington, 2004), and 23 deaths were attributed to Hurricane Frances (National Weather Service, 2004). Several watersheds drain counties in southwest-central Florida that were affected by Hurricane Frances. De Soto, Hardee, and Polk Counties generally are drained by the Peace River system, which flows southwestward to Charlotte Harbor and the Gulf of Mexico. Hillsborough and Pasco Counties generally are drained by the Alafia, Hillsborough, Anclote, and Pithlachascotee River systems. Water in the Hillsborough and Alafia River watersheds flows west to Tampa Bay and water in the Anclote and Pithlachascotee River watersheds flows west to the Gulf of Mexico. (fig. 1, http://water.usgs.gov/pubs/fs/2005/3028/#fig1).

Occurrence of steroid estrogens, endocrine-disrupting phenols, and acid pharmaceutical residues in urban riverine water of the Pearl River Delta, South China.

PubMed

Peng, Xianzhi; Yu, Yiyi; Tang, Caiming; Tan, Jianhua; Huang, Qiuxin; Wang, Zhendi

2008-07-01

A scoping study was conducted to investigate the residues of nineteen pharmaceuticals and personal care products (PPCPs), including 4 natural and 3 synthetic steroid estrogens, 7 endocrine-disrupting phenols, and 5 acid pharmaceuticals in three urban streams and the Major Pearl River at Guangzhou, a megapolis in the Pearl River Delta, South China. Estrone was detected in >60% water samples with a maximum concentration of 65 ng L(-1). Endocrine-disrupting phenols (nonylphenol, bisphenol A, triclosan, 2-phenylphenol, methyparaben, and propylparaben) were found to be widely present at rather high concentrations in the urban riverine water of Guangzhou. Salicylic acid, clofibric acid and ibuprofen were detected in most water samples with maximum concentrations of 2098, 248 and 1417 ng L(-1) respectively, whereas naproxen was less frequently detected and also at lower concentration. Both the detection frequencies and median concentrations of the PPCPs appeared higher during the low-flow season than during the high-flow season. The seasonal difference in PPCPs occurrence was probably attributed to the dilution effect caused by the rainfall. PPCPs in the urban riverine water of Guangzhou originated mainly from random discharge and/or leakage of municipal wastewater. PPCPs contamination in the Major Pearl River may be of a potential environmental issue, especially during the low-flow season.

Integrating Flow, Form, and Function for Improved Environmental Water Management

NASA Astrophysics Data System (ADS)

Albin Lane, Belize Arela

Rivers are complex, dynamic natural systems. The performance of river ecosystem functions, such as habitat availability and sediment transport, depends on the interplay of hydrologic dynamics (flow) and geomorphic settings (form). However, most river restoration studies evaluate the role of either flow or form without regard for their dynamic interactions. Despite substantial recent interest in quantifying environmental water requirements to support integrated water management efforts, the absence of quantitative, transferable relationships between river flow, form, and ecosystem functions remains a major limitation. This research proposes a novel, process-driven methodology for evaluating river flow-form-function linkages in support of basin-scale environmental water management. This methodology utilizes publically available geospatial and time-series data and targeted field data collection to improve basic understanding of river systems with limited data and resource requirements. First, a hydrologic classification system is developed to characterize natural hydrologic variability across a highly altered, physio-climatically diverse landscape. Next, a statistical analysis is used to characterize reach-scale geomorphic variability and to investigate the utility of topographic variability attributes (TVAs, subreach-scale undulations in channel width and depth), alongside traditional reach-averaged attributes, for distinguishing dominant geomorphic forms and processes across a hydroscape. Finally, the interacting roles of flow (hydrologic regime, water year type, and hydrologic impairment) and form (channel morphology) are quantitatively evaluated with respect to ecosystem functions related to hydrogeomorphic processes, aquatic habitat, and riparian habitat. Synthetic river corridor generation is used to evaluate and isolate the role of distinct geomorphic attributes without the need for intensive topographic surveying. This three-part methodology was successfully applied in the Sacramento Basin of California, USA, a large, heavily altered Mediterranean-montane basin. A spatially-explicit hydrologic classification of California distinguished eight natural hydrologic regimes representing distinct flow sources, hydrologic characteristics, and rainfall-runoff controls. A hydro-geomorphic sub-classification of the Sacramento Basin based on stratified random field surveys of 161 stream reaches distinguished nine channel types consisting of both previously identified and new channel types. Results indicate that TVAs provide a quantitative basis for interpreting non-uniform as well as uniform geomorphic processes to better distinguish linked channel forms and functions of ecological significance. Finally, evaluation of six ecosystem functions across alternative flow-form scenarios in the Yuba River watershed highlights critical tradeoffs in ecosystem performance and emphasizes the significance of spatiotemporal diversity of flow and form for maintaining ecosystem integrity. The methodology developed in this dissertation is broadly applicable and extensible to other river systems and ecosystem functions, where findings can be used to characterize complex controls on river ecosystems, assess impacts of proposed flow and form alterations, and inform river restoration strategies. Overall, this research improves scientific understanding of the linkages between hydrology, geomorphology, and river ecosystems to more efficiently allocate scare water resources for human and environmental objectives across natural and built landscapes.

Investigating the impact of land cover change on peak river flow in UK upland peat catchments, based on modelled scenarios

NASA Astrophysics Data System (ADS)

Gao, Jihui; Holden, Joseph; Kirkby, Mike

2014-05-01

Changes to land cover can influence the velocity of overland flow. In headwater peatlands, saturation means that overland flow is a dominant source of runoff, particularly during heavy rainfall events. Human modifications in headwater peatlands may include removal of vegetation (e.g. by erosion processes, fire, pollution, overgrazing) or pro-active revegetation of peat with sedges such as Eriophorum or mosses such as Sphagnum. How these modifications affect the river flow, and in particular the flood peak, in headwater peatlands is a key problem for land management. In particular, the impact of the spatial distribution of land cover change (e.g. different locations and sizes of land cover change area) on river flow is not clear. In this presentation a new fully distributed version of TOPMODEL, which represents the effects of distributed land cover change on river discharge, was employed to investigate land cover change impacts in three UK upland peat catchments (Trout Beck in the North Pennines, the Wye in mid-Wales and the East Dart in southwest England). Land cover scenarios with three typical land covers (i.e. Eriophorum, Sphagnum and bare peat) having different surface roughness in upland peatlands were designed for these catchments to investigate land cover impacts on river flow through simulation runs of the distributed model. As a result of hypothesis testing three land cover principles emerged from the work as follows: Principle (1): Well vegetated buffer strips are important for reducing flow peaks. A wider bare peat strip nearer to the river channel gives a higher flow peak and reduces the delay to peak; conversely, a wider buffer strip with higher density vegetation (e.g. Sphagnum) leads to a lower peak and postpones the peak. In both cases, a narrower buffer strip surrounding upstream and downstream channels has a greater effect than a thicker buffer strip just based around the downstream river network. Principle (2): When the area of change is equal, the size of land cover change patches has no effect on river flow for patch sizes up to 40000m2. Principle (3): Bare peat on gentle slopes gives a faster flow response and higher peak value at the catchment outlet, while high density vegetation or re-vegetation on a gentle slope area has larger positive impact on peak river flow delay when compared with the same practices on steeper slopes. These simple principles should be useful to planners who wish to determine resource efficiency and optimisation for peatland protection and restoration works in headwater systems. If practitioners require further detail on impacts of specific spatial changes to land cover in a catchment then this modelling approach can be applied to new catchments of concern.

Rainfall forecast in the Upper Mahaweli basin in Sri Lanka using RegCM model

NASA Astrophysics Data System (ADS)

Muhammadh, K. M.; Mafas, M. M. M.; Weerakoon, S. B.

2017-04-01

The Upper Mahaweli basin is the upper most sub basin of 788 km2 in size above Polgolla barrage in the Mahaweli River, the longest river in Sri Lanka which starts from the central hills of the island and drains to the sea at the North-east coast. Rainfall forecast in the Upper Mahaweli basin is important for issuing flood warning in the river downstream of the reservoirs, landslide warning in the settlements in hilly areas. Anticipatory water management in the basin including reservoir operations, barrage gate operation for releasing water for irrigation and flood control also require reliable rainfall and runoff prediction in the sub basin. In this study, the Regional Climate Model (RegCM V4.4.5.11) is calibrated for the basin to dynamically downscale reanalysis weather data of Global Climate Model (GCM) to forecast the rainfall in the basin. Observed rainfalls at gauging stations within the basin were used for model calibration and validation. The observed rainfall data was analysed using ARC GIS and the output of RegCM was analysed using GrADS tool. The output of the model and the observed precipitation were obtained on grids of size 0.1 degrees and the accuracy of the predictions were analysed using RMSE and Mean Model Absolute Error percentage (MAME %). The predictions by the calibrated RegCM model for the basin is shown to be satisfactory. The model is a useful tool for rainfall forecast in the Upper Mahaweli River basin.

Hydraulic modeling of flow impact on bridge structures: a case study on Citarum bridge

NASA Astrophysics Data System (ADS)

Siregar, R. I.

2018-02-01

Flood waves because of the rapid catchment response to high intense rainfall, breaches of flood defenses may induce huge impact forces on structures, causing structural damage or even failures. Overflowing stream that passes over the bridge, it means to discharge flood water level is smaller than the capacity of the river flow. In this study, the researches present the methodological approach of flood modeling on bridge structures. The amount of force that obtained because of the hydrostatic pressure received by the bridge at the time of the flood caused the bridge structure disrupted. This paper presents simulation of flow impact on bridge structures with some event flood conditions. Estimating the hydrostatic pressure developed new model components, to quantify the flow impact on structures. Flow parameters applied the model for analyzing, such as discharge, velocity, and water level or head that effect of bridge structures. The simulation will illustrate the capability of bridge structures with some event flood river and observe the behavior of the flow that occurred during the flood. Hydraulic flood modeling use HEC-RAS for simulation. This modeling will describe the impact on bridge structures. Based on the above modelling resulted, in 2008 has flood effect more than other years on the Citarum Bridge, because its flow overflow on the bridge.

River sedimentation and channel bed characteristics in northern Ethiopia

NASA Astrophysics Data System (ADS)

Demissie, Biadgilgn; Billi, Paolo; Frankl, Amaury; Haile, Mitiku; Lanckriet, Sil; Nyssen, Jan

2016-04-01

Excessive sedimentation and flood hazard are common in ephemeral streams which are characterized by flashy floods. The purposes of this study was to investigate the temporal variability of bio-climatic factors in controlling sediment supply to downstream channel reaches and the effect of bridges on local hydro-geomorphic conditions in causing the excess sedimentation and flood hazard in ephemeral rivers of the Raya graben (northern Ethiopia). Normalized Difference Vegetation Index (NDVI) was analyzed for the study area using Landsat imageries of 1972, 1986, 2000, 2005, 2010, and 2012). Middle term, 1993-2011, daily rainfall data of three meteorological stations, namely, Alamata, Korem and Maychew, were considered to analyse the temporal trends and to calculate the return time intervals of rainfall intensity in 24 hours for 2, 5, 10 and 20 years using the log-normal and the Gumbel extreme events method. Streambed gradient and bed material grain size were measured in 22 river reaches (at bridges and upstream). In the study catchments, the maximum NDVI values were recorded in the time interval from 2000 to 2010, i.e. the decade during which the study bridges experienced the most severe excess sedimentation problems. The time series analysis for a few rainfall parameters do not show any evidence of rainfall pattern accountable for an increase in sediment delivery from the headwaters nor for the generation of higher floods with larger bedload transport capacities. Stream bed gradient and bed material grain size data were measured in order to investigate the effect of the marked decrease in width from the wide upstream channels to the narrow recently constructed bridges. The study found the narrowing of the channels due to the bridges as the main cause of the thick sedimentation that has been clogging the study bridges and increasing the frequency of overbank flows during the last 15 years. Key terms: sedimentation, ephemeral streams, sediment size, bridge clogging

Bayesian Assessment of the Uncertainties of Estimates of a Conceptual Rainfall-Runoff Model Parameters

NASA Astrophysics Data System (ADS)

Silva, F. E. O. E.; Naghettini, M. D. C.; Fernandes, W.

2014-12-01

This paper evaluated the uncertainties associated with the estimation of the parameters of a conceptual rainfall-runoff model, through the use of Bayesian inference techniques by Monte Carlo simulation. The Pará River sub-basin, located in the upper São Francisco river basin, in southeastern Brazil, was selected for developing the studies. In this paper, we used the Rio Grande conceptual hydrologic model (EHR/UFMG, 2001) and the Markov Chain Monte Carlo simulation method named DREAM (VRUGT, 2008a). Two probabilistic models for the residues were analyzed: (i) the classic [Normal likelihood - r ≈ N (0, σ²)]; and (ii) a generalized likelihood (SCHOUPS & VRUGT, 2010), in which it is assumed that the differences between observed and simulated flows are correlated, non-stationary, and distributed as a Skew Exponential Power density. The assumptions made for both models were checked to ensure that the estimation of uncertainties in the parameters was not biased. The results showed that the Bayesian approach proved to be adequate to the proposed objectives, enabling and reinforcing the importance of assessing the uncertainties associated with hydrological modeling.

Spatio-temporal variation of water flow and sediment discharge in the Mahanadi River, India

NASA Astrophysics Data System (ADS)

Bastia, Fakira; Equeenuddin, Sk. Md.

2016-09-01

The transport of sediments by rivers to the oceans represents an important link between the terrestrial and marine ecosystem. Therefore, this work aims to study spatio-temporal variation of the sediment discharge and erosion rate in the Mahanadi river, one of the biggest rivers in India, over past three decades vis-à-vis their controlling factors. To understand the sediment load variation, the trend analysis in the time series data of rainfall, water and sediment discharge of the Mahanadi river were also attempted. The non-parametric Mann-Kendall and Sen's methods were used to determine whether there was a positive or negative trend in the time series data with their statistical significance. The occurrence of abrupt changes was detected using Pettitt test. The trend test result represents that sediment load delivered from the Mahanadi river to the global ocean has decreased sharply at the rate of 0.515 × 106 tons/year between 1980 and 2010. Water discharge and rainfall in the basin showed no significant decreasing trend except at only one tributary. The decline in sediment discharge from the basin to the Bay of Bengal is mainly due to the increase in the number of dams, which has recorded the increase from 70 to 253 during the period of 1980 to 2010. Over the past 30 years the Mahanadi river has discharged about 49.0 ± 20.5 km3 of water and 17.4 ± 12.7 × 106 tons of sediment annually to the Bay of Bengal whereas the mean erosional rate is 265 ± 125 tons/km2/year over the period of 30 years in the basin. Based on the current data (2000-2001 to 2009-2010), sediment flux and water discharge to the ocean are 12 ± 5 × 106 tons/year and 49 ± 16 km3/year respectively; and ranking Mahanadi river second in terms of water discharge and sediment flux to the ocean among the peninsular rivers in India.

Channel Processes and Sedimentology of a Boulder-Bed Ephemeral Stream

NASA Astrophysics Data System (ADS)

Billi, Paolo

2014-05-01

Very few papers report about the geomorphology and sedimentology of modern very coarse-grained, ephemeral streams. Other than the relevance of shedding some light on fluvial processes in dryland, boulder-bed rivers, this paper aims to provide some insight on their sedimentological characteristics as a diagnostic tool in the interpretation of old deposits. A field study on such topics is carried out on the Golina River, a sandy boulder-bed ephemeral stream of the Kobo basin in northern Ethiopia, subjected to intermittent flow generated by isolated, high intensity rainfall. Though the main gemorphological characteristics of the braid bars and channels are apparently similar to those of perennial counterparts, field investigations show the general physiographic setting and the sedimentology of the study reach result from very different depositional/erosion processes. A model based on the superimposition of coarse-grained bedload sheets, with the characteristics described by Whiting et la. (1988), and subsequent dissection during the receding flood flow is considered. This model was found to well explain the morphological and sedimentological features of the study river reach.

Geomorphology of the lower Copper River, Alaska

USGS Publications Warehouse

Brabets, T.P.

1996-01-01

The Copper River, located in southcentral Alaska, drains an area of more than 24,000 square miles. About 30 miles above its mouth, this large river enters Miles Lake, a proglacial lake formed by the retreat of Miles Glacier. Downstream from the outlet of Miles Lake, the Copper River flows past the face of Childs Glacier before it enters a large, broad, alluvial flood plain. The Copper River Highway traverses this flood plain and in 1996, 11 bridges were located along this section of the highway. These bridges cross parts or all of the Copper River and in recent years, some of these bridges have sustained serious damage due to the changing course of the Copper River. Although the annual mean discharge of the lower Copper River is 57,400 cubic feet per second, most of the flow occurs during the summer months from snowmelt, rainfall, and glacial melt. Approximately every six years, an outburst flood from Van Cleve Lake, a glacier-dammed lake formed by Miles Glacier, releases approximately 1 million acre-feet of water into the Copper River. At the peak outflow rate from Van Cleve Lake, the flow of the Copper River will increase an additional 140,000 and 190,000 cubic feet per second. Bedload sampling and continuous seismic reflection were used to show that Miles Lake traps virtually all the bedload being transported by the Copper River as it enters the lake from the north. The reservoir-like effect of Miles Lake results in the armoring of the channel of the Copper River downstream from Miles Lakes, past Childs Glacier, until it reaches the alluvial flood plain. At this point, bedload transport begins again. The lower Copper River transports 69 million tons per year of suspended sediment, approximately the same quantity as the Yukon River, which drains an area of more than 300,000 square miles. By correlating concurrent flows from a long-term streamflow- gaging station on the Copper River with a short-term streamflow-gaging station at the outlet of Miles Lake, long-term flow characteristics of the lower Copper River were synthesized. Historical discharge and cross-section data indicate that as late as 1970, most of the flow of the lower Copper River was through the first three bridges of the Copper River Highway as it begins to traverse the alluvial flood plain. In the mid 1980's, a percentage of the flow had shifted away from these three bridges and in 1995, only 51 percent of the flow of the Copper River passed through them. Eight different years of aerial photography of the lower Copper River were analyzed using Geographical Information System techniques. This analysis indicated that no major channel changes were caused by the 1964 earthquake. A flood in 1981 that had a recurrence interval of more than 100 years caused significant channel changes in the lower Copper River. A probability analysis of the lower Copper River indicated stable areas and the long-term locations of channels. By knowing the number of times a particular area has been occupied by water and the last year an area was occupied by water, areas of instability can be located. A Markov analysis of the lower Copper River indicated that the tendency of the flood plain is to remain in its current state. Large floods of the magnitude of the 1981 event are believed to be the cause of major changes in the lower Copper River.

Geomorphology of the lower Copper River, Alaska

USGS Publications Warehouse

Brabets, Timothy P.

1997-01-01

The Copper River, located in southcentral Alaska, drains an area of more than 24,000 square miles. About 30 miles above its mouth, this large river enters Miles Lake, a proglacial lake formed by the retreat of Miles Glacier. Downstream from the outlet of Miles Lake, the Copper River flows past the face of Childs Glacier before it enters a large, broad, alluvial flood plain. The Copper River Highway traverses this flood plain and in 1995, 11 bridges were located along this section of the highway. These bridges cross parts of the Copper River and in recent years, some of these bridges have sustained serious damage due to the changing course of the Copper River. Although the annual mean discharge of the lower Copper River is 57,400 cubic feet per second, most of the flow occurs during the summer months from snowmelt, rainfall, and glacial melt. Approximately every six years, an outburst flood from Van Cleve Lake, a glacier-dammed lake formed by Miles Glacier, releases approximately 1 million acre-feet of water into the Copper River. When the outflow rate from Van Cleve Lake reaches it peak, the flow of the Copper River will increase between 150,000 to 190,000 cubic feet per second. Data collected by bedload sampling and continuous seismic reflection indicated that Miles Lake traps virtually all the bedload being transported by the Copper River as it enters the lake from the north. The reservoir-like effect of Miles Lake results in the armoring of the channel of the Copper River downstream from Miles Lake, past Childs Glacier, until it reaches the alluvial flood plain. At this point, bedload transport begins again. The lower Copper River transports 69 million tons per year of suspended sediment, approximately the same quantity as the Yukon River, which drains an area of more than 300,000 square miles. By correlating concurrent flows from a long-term streamflow-gaging station on the Copper River with a short-term streamflow-gaging station at the outlet of Miles Lake, long-term flow characteristics of the lower Copper River were synthesized. Historical discharge and cross-section data indicate that as late as 1970, most of the flow of the lower Copper River was through the first three bridges of the Copper River Highway as it begins to traverse the alluvial flood plain. In the mid 1980's, a percentage of the flow had shifted away from these three bridges and in 1995, only 51 percent of the flow of the Copper River passed through them. Eight different years of aerial photography of the lower Copper River were analyzed using Geographical Information System techniques. This analysis indicated that no major channel changes were caused by the 1964 earthquake. However, a flood in 1981 that had a recurrence interval of more than 100 years caused significant channel changes in the lower Copper River. A probability analysis of the lower Copper River indicated stable areas and the long-term locations of channels. By knowing the number of times a particular area has been occupied by water and the last year an area was occupied by water, areas of instability can be located. A Markov analysis of the lower Copper River indicated that the tendency of the flood plain is to remain in its current state. Large floods of the magnitude of the 1981 event are believed to be the cause of major changes in the lower Copper River.

South Asia river flow projections and their implications for water resources

NASA Astrophysics Data System (ADS)

Mathison, C.; Wiltshire, A. J.; Falloon, P.; Challinor, A. J.

2015-06-01

South Asia is a region with a large and rising population and a high dependance on industries sensitive to water resource such as agriculture. The climate is hugely variable with the region relying on both the Asian Summer Monsoon (ASM) and glaciers for its supply of fresh water. In recent years, changes in the ASM, fears over the rapid retreat of glaciers and the increasing demand for water resources for domestic and industrial use, have caused concern over the reliability of water resources both in the present day and future for this region. The climate of South Asia means it is one of the most irrigated agricultural regions in the world, therefore pressures on water resource affecting the availability of water for irrigation could adversely affect crop yields and therefore food production. In this paper we present the first 25 km resolution regional climate projections of river flow for the South Asia region. ERA-Interim, together with two global climate models (GCMs), which represent the present day processes, particularly the monsoon, reasonably well are downscaled using a regional climate model (RCM) for the periods; 1990-2006 for ERA-Interim and 1960-2100 for the two GCMs. The RCM river flow is routed using a river-routing model to allow analysis of present day and future river flows through comparison with river gauge observations, where available. In this analysis we compare the river flow rate for 12 gauges selected to represent the largest river basins for this region; Ganges, Indus and Brahmaputra basins and characterize the changing conditions from east to west across the Himalayan arc. Observations of precipitation and runoff in this region have large or unknown uncertainties, are short in length or are outside the simulation period, hindering model development and validation designed to improve understanding of the water cycle for this region. In the absence of robust observations for South Asia, a downscaled ERA-Interim RCM simulation provides a benchmark for comparison against the downscaled GCMs. On the basis that these simulations are among the highest resolution climate simulations available we examine how useful they are for understanding the changes in water resources for the South Asia region. In general the downscaled GCMs capture the seasonality of the river flows, with timing of maximum river flows broadly matching the available observations and the downscaled ERA-Interim simulation. Typically the RCM simulations over-estimate the maximum river flows compared to the observations probably due to a positive rainfall bias and a lack of abstraction in the model although comparison with the downscaled ERA-Interim simulation is more mixed with only a couple of the gauges showing a bias compared with the downscaled GCM runs. The simulations suggest an increasing trend in annual mean river flows for some of the river gauges in this analysis, in some cases almost doubling by the end of the century; this trend is generally masked by the large annual variability of river flows for this region. The future seasonality of river flows does not change with the future maximum river flow rates still occuring during the ASM period, with a magnitude in some cases, greater than the present day natural variability. Increases in river flow during peak flow periods means additional water resource for irrigation, the largest usage of water in this region, but also has implications in terms of inundation risk. Low flow rates also increase which is likely to be important at times of the year when water is historically more scarce. However these projected increases in resource from rivers could be more than countered by changes in demand due to reductions in the quantity and quality of water available from groundwater, increases in domestic use due to a rising population or expansion of other industries such as hydro-electric power generation.

Opportunities for Hydrologic Research in the Congo Basin

NASA Astrophysics Data System (ADS)

Alsdorf, D. E.; Beighley, E., II; Lee, H.; Tshimanga, R.; Spencer, R. G.; O'Loughlin, F.

2014-12-01

We review the published results on the Congo Basin hydrology and find that there are historic data, ongoing measurement recording efforts, and important model results. Annual rainfall is ~2000 mm/yr along an east-west trend, decreasing northward and southward to ~1100 mm/yr. While some studies show rain gauges at specific locations with declines in P greater than 10% from 1960 to 1990, other studies suggest that basin wide decreases from 1951 to 1993 are modest at 4.5% or that the trend is minimal. Studies during the 1950s using lysimeters, pans, and models suggest that the annual potential ET varies little across the basin at a 1100 mm/yr to 1200 mm/yr. Over the past century, river discharge data has been collected at 100s of stream gauges with historic and recent data at 96 locations now publicly available. Discharge of the Congo River at Kinshasa-Brazzaville experienced an increase of 21% during 1960-1970 in comparison to background values of the previous decades and of today. There does not appear to be a long-term discharge trend over the century of record. Satellite altimetry measurements collected during high and low flows show that the Cuvette Centrale wetland water levels are consistently 0.5m to 3m higher in elevation than the immediately adjacent Congo River levels. Wetland water depths are shallow at about 1m whereas the Congo is typically less than 15m deep everywhere upstream of Kinshasa. The wetlands do not appear to be marked by sizable channels such that the flows are diffusive. CO2 and CH4 evasion from the Congo waters directly to the atmosphere are estimated at 1.6 to 3.2 Tg/yr for CH4 from the Cuvette wetland waters and 105 to 204 g C/m2/yr for CO2 from waters of the Oubangui River. Using these published results, we suggest seven hypotheses that may lead to important water and carbon cycle discoveries. These hypotheses focus on the source of the Cuvette waters and how those waters leave the wetland; on river discharge generated by historic rainfall; on the connection between climate change and the rainfall-runoff generated by the ITCZ; on deforestation and hydroelectric power generation; and on the amount of carbon emitted from Congo waters. To address these hypotheses, the Congo research community will need to work together to host meetings, share ideas, access data, ensure funding, and provide infrastructural support.

Nutrient Uptake and Cycles of Change: the Ventura River in Southern California

NASA Astrophysics Data System (ADS)

Leydecker, A.; Simpson, J.; Grabowski, L.

2003-12-01

Watersheds in Mediterranean climates are characterized by extreme seasonal and inter-annual rainfall variability. This variability engenders cycles of sediment deposition and removal, algal growth, and the advance and retreat of riparian and aquatic vegetation. In turn, these changes dramatically alter the appearance and biological functioning of rivers and streams, regulating the uptake of nutrients. The Ventura River drains 580 sq. km of mountainous coastal watershed 100 km northwest of Los Angles, Ca. More than 90 % of the average annual rainfall of 500 mm falls between December and March with most of the annual runoff occurring within a few days. Since 1930, annual runoff has varied from 0.01 to 70 cm/ha, with a mean of 12 and median of 4 cm. We have been measuring dissolved nutrient concentrations at four locations on the lower 9 kilometers of the river for the past 3 years (annual runoff of 19, 0.6 and 14 cm, respectively) and quantifying the relative abundance of plants and algae during 2003. A subsequent decrease in nutrient concentrations below a treated sewage outfall at km 8 provides estimates of nutrient uptake under changing conditions. Nitrate concentrations on the river peak in early winter, presumably from mineralization and mobilization after the advent of the rainy season, and decrease to a minimum by late summer. Phosphate, controlled by dry-season treatment plant outflows, has an opposite pattern. The seasonal variation in both is considerable (0 to 380 microM for nitrate, 0 to 35 microM for phosphate). Major winter storms, such as occur during severe El Nino years (peak flows > 1000 cms), begin a transformational cycle by completely scouring the channel of vegetation and fine sediment; this occurs, on average, once every 10 to 12 years (the interval has varied from 3 to 30 years). The scoured channel, with warmer water temperatures, the absence of shade and a nutrient rich environment, becomes dominated by filamentous algae (principally Cladophora, Rhizoclonium, Enteromorpha and Spirogyra spp.). In contrast, drought years occasion exuberant plant growth and the competitive replacement of algae by aquatic vegetation. Absent scouring winter flows, perennial aquatic plants become established, trapping fine sediment and narrowing the wetted channel; the rapid growth of riparian vegetation (Arundo donax and Salix spp.) provides increased shade to the narrowed waterway. These processes increasingly stabilize the channel and elevate the threshold flow of a scouring storm; the major storm of 2003, following the 2002 drought year (peak flow of 5 cms), produced appreciably less channel transformation than a similarly-sized storm in 2001 (peak flow of 500 cms). During the 2002 drought year, dry-season nitrate concentrations at the river mouth were reduced to near zero, likely due to reduced flows, extensive vascular plant growth supporting high rates of denitrification and vegetative uptake, and enhanced sediment processes from increased fine sediment entrapment. Higher nitrate concentrations at the same location in 2003 (circa 60 microM) exhibited a 3-fold increase compared with 2001, an algal dominated year with a similar flow regime, and N uptake below the treatment plant appears to be substantially decreased.

Design rainfall depth estimation through two regional frequency analysis methods in Hanjiang River Basin, China

NASA Astrophysics Data System (ADS)

Xu, Yue-Ping; Yu, Chaofeng; Zhang, Xujie; Zhang, Qingqing; Xu, Xiao

2012-02-01

Hydrological predictions in ungauged basins are of significant importance for water resources management. In hydrological frequency analysis, regional methods are regarded as useful tools in estimating design rainfall/flood for areas with only little data available. The purpose of this paper is to investigate the performance of two regional methods, namely the Hosking's approach and the cokriging approach, in hydrological frequency analysis. These two methods are employed to estimate 24-h design rainfall depths in Hanjiang River Basin, one of the largest tributaries of Yangtze River, China. Validation is made through comparing the results to those calculated from the provincial handbook approach which uses hundreds of rainfall gauge stations. Also for validation purpose, five hypothetically ungauged sites from the middle basin are chosen. The final results show that compared to the provincial handbook approach, the Hosking's approach often overestimated the 24-h design rainfall depths while the cokriging approach most of the time underestimated. Overall, the Hosking' approach produced more accurate results than the cokriging approach.

Hazard assessment of landslide and debris flow in the Rjeina river valley, Croatia

NASA Astrophysics Data System (ADS)

Wang, Chunxiang; Watanabe, Naoki; Marui, Hideaki

2013-04-01

The Rječina River extends approximately 18.7km long and flows into the Adriatic Sea at the center of Rijeka City, Croatia. Landslide, debris flow and rockfall are main geohazards in the middle part of the Rječina river basin. The zone between the Valići reservoir dam and the Pasac Bridge is particularly the most unstable and hazardous area in the river basin. The Grohovo landslide in the middle part of the river basin is located on the valley's slope facing southwest and situated at just downstream of the Valići dam. This landslide is the largest active landslide along the Adriatic Sea coast in Croatia. Assuming that serious heavy rainfall or earthquake occurs, it is most likely to occur two types of geohazard event. One scenario is that the debris deposited on the Grohovo landslide will move down to the channel of the Rječina River and dam up the river course. Another scenario is that the slope deposits on the landslide will be mixed with water and subsequently turn into a debris flow reaching to Rijeka City. We simulate both two cases of the formation of landslide-dam and the occurrence of debris-flow by two integrated models using GIS to represent the dynamic process across 3D terrains. In the case of the formation of landslide-dam, it is assumed that slope deposits will move downhill after failing along a shear zone. GIS-based revised Hovland's 3D limit equilibrium model is used to simulate the movement and stoppage of the slope deposits to form landslide-dam. The 3D factor of safety will be calculated step by step during the sliding process simulation. Stoppage is defined by the factor of safety much greater than one and the velocity equal to zero. The simulation result shows that the height of the landslide-dam will be nine meters. In case of debris flow, the mixture of slope deposits and water will be differentiated from landslide by fluid-like deformation of the mobilized material. GIS-based depth-averaged 2D numerical model is used to predict the runout distance and inundated area of the debris flow. The simulation result displays the propagation and deposition of the debris flow across the complex topography and shows that the debris flow takes about 16 minutes to travel about 6 km along the Rječina River and consequently reaches to Rijeka City.

A Spatially Distributed Hydrological Model For The Okavango Delta, Botswana

NASA Astrophysics Data System (ADS)

Bauer, P.; Kinzelbach, W.; Thabeng, G.

2003-04-01

The Okavango Delta is a large (˜30 000 km^2) inland delta situated in northern Botswana. It is subject to annual flooding due to the strong seasonality of the inflowing Okavango River and of local rainfall. The inflowing waters spread out over vast perennial and seasonal floodplains and partially infiltrate into the underlying sand aquifer. Ultimately, the water is consumed by evapotranspiration, there is no significant outflow from the Delta. The system's response to the annual flood in the Okavango River as well as local rainfall and evapotranspiration is modelled within a finite difference scheme based on MODFLOW. The wetland and the underlying sand aquifer are incorporated as two separate layers. In the superficial layer, either steady uniform channel flow (Darcy-Weisbach equation) or potential flow (Darcy flow) can be chosen on a cell-by-cell basis. The coarse spatial resolution does not capture the small-scale variation in the topographic elevation. Therefore, upscaling techniques are applied to incorporate the statistics of that variation into effective parameters for the hydraulic conductivity, the storage coefficient and the evapotranspiration. Modelled flooding patterns are compared with flooding patterns derived from NOAA-AVHRR and other remote sensing data (1 km resolution). Good correspondence between the two is achieved based on parameters chosen according to prior knowledge and field data. Global indicators like the average size of the Delta and the temporal variance of its size are closely reproduced. Ultimately, the remotely sensed flooding patterns will be used to calibrate the model. Apart from flooding patterns, model outputs include cell-by-cell flow terms. Water balances can be calculated for arbitrary sub-regions of the grid. Other monitoring data like water levels in rivers and boreholes as well as discharges at gauging points may be used for validation of the model. The Okavango Delta is one of the prime conservation areas in Africa and a top-destination for international tourism. It is the principal freshwater resource for the local people. Furthermore, three countries (Angola, Namibia and Botswana) share the river basin and most of the runoff in the river is actually generated in Angola. Some intricate management problems arise in this complex set-up of interests and stakeholders (dam building in Angola, water abstraction, morphological engineering in the Delta etc.). In some cases, scenario calculations may help to assess the impacts of the planned actions and to analyse their sustainability prior to implementation.

Organic matter dynamics and stable isotope signature as tracers of the sources of suspended sediment

NASA Astrophysics Data System (ADS)

Schindler Wildhaber, Y.; Liechti, R.; Alewell, C.

2012-06-01

Suspended sediment (SS) and organic matter in rivers can harm brown trout Salmo trutta by affecting the health and fitness of free swimming fish and by causing siltation of the riverbed. The temporal and spatial dynamics of sediment, carbon (C), and nitrogen (N) during the brown trout spawning season in a small river of the Swiss Plateau were assessed and C isotopes as well as the C/N atomic ratio were used to distinguish autochthonous and allochthonous sources of organic matter in SS loads. The visual basic program IsoSource with 13Ctot and 15N as input isotopes was used to quantify the temporal and spatial sources of SS. Organic matter concentrations in the infiltrated and suspended sediment were highest during low flow periods with small sediment loads and lowest during high flow periods with high sediment loads. Peak values in nitrate and dissolved organic C were measured during high flow and high rainfall, probably due to leaching from pasture and arable land. The organic matter was of allochthonous sources as indicated by the C/N atomic ratio and δ13Corg. Organic matter in SS increased from up- to downstream due to an increase of pasture and arable land downstream of the river. The mean fraction of SS originating from upper watershed riverbed sediment decreased from up to downstream and increased during high flow at all measuring sites along the course of the river. During base flow conditions, the major sources of SS are pasture, forest and arable land. The latter increased during rainy and warmer winter periods, most likely because both triggered snow melt and thus erosion. The measured increase in DOC and nitrate concentrations during high flow support these modeling results. Enhanced soil erosion processes on pasture and arable land are expected with increasing heavy rain events and less snow during winter seasons due to climate change. Consequently, SS and organic matter in the river will increase, which will possibly affect brown trout negatively.

Distribution of Large Wood Within River Corridors in Relation to Flow Regime in the Semiarid Western US

NASA Astrophysics Data System (ADS)

Wohl, Ellen; Cadol, Daniel; Pfeiffer, Andrew; Jackson, Karen; Laurel, DeAnna

2018-03-01

The cumulative volume and spatial distribution of large wood (LW) along river corridors (channels and floodplains) reflect interactions between rates and volumes of LW recruitment and channel transport capacity through time. Rivers of the semiarid interior western US can have relatively low-magnitude disturbances associated with annual snowmelt or relatively high-magnitude disturbances associated with episodic rainfall runoff, especially following wildfires. We use characteristics of LW from 25 river segments in four regions of New Mexico and Colorado to analyze wood loads and spatial patterns of wood distribution in relation to disturbance regime. High-magnitude disturbances move LW onto floodplains and create longitudinally nonuniform LW distributions with aggregated (closer together than random) LW pieces and abundant LW jams in the floodplain. Sites with low-magnitude disturbances have a greater proportion of LW in the channel and much of this wood is within segregated (farther apart than random) jams. These results imply that river management, which typically focuses on LW within channels, should focus on floodplain as well as in-channel LW in rivers with high-magnitude disturbances. The results also indicate that the proportions of LW loads in channels versus floodplains can differ significantly among rivers with different disturbance regimes that are otherwise similar in terms of forest type or drainage area. This is particularly relevant to mountainous regions with elevation-related changes in flow and disturbance regime. River management that reintroduces LW to river corridors will be most effective if it incorporates the mobility and spatial distribution of LW.

Self-organization, preferential flow and rainfall runoff behavior - is there a connection?

NASA Astrophysics Data System (ADS)

Zehe, Erwin; Blume, Theresa; Kleidon, Axel; Ehret, Uwe; Scherer, Ulrike; Westhoff, Martijn

2013-04-01

In line with the studies of Kleidon et al. (2012) and Zehe et al. (2010) the proposed study analyzes mass flow related flows of free energy in open hydrological systems - hillslopes and small catchments - using thermodynamics methods. Why a thermodynamic treatment? A small part of the kinetic energy input from incoming rainfall is dissipated into heat and to break up soil aggregates. Depending on the partitioning of the incoming rainfall into overland flow and soil water, the remaining part of the incoming kinetic energy is partly transformed into potential energy of surface water and subsequently partly exported as kinetic energy of overland flow from the system; the rest is dissipated by frictional losses. The other part of rainfall infiltrates thereby increasing potential energy of soil water but depleting at the same time (gradients in) capillary binding energy of soil water, which again comprises energy dissipation into heat of immersion. Although, these mass fluxes are not associated with large heat fluxes, they reflect the overall conservation of energy as well as the second law of thermodynamics. They require thus a thermodynamic treatment, because tiny amounts of kinetic energy, surface energy and potential energy are dissipated into heat: this implies irreversibility and explains why water does not flow uphill. Soil hydraulic equilibrium (HE), arising from a balance in potential and capillary binding energy in soil, can be interpreted as a state of maximum entropy in soil. Soil water potential, defined as sum of matric potential and gravity potential, is in HE equal to zero along the soil profile. This corresponds to a state of maximum entropy due to a zero potential gradient, which implies due to Zehe et al. (2010) a state of minimum (Helmholtz) free energy. Our first main objective is to quantify to which extent connected preferential flow path, in our case vertical macropores and the river network enhance flow velocities at a given driving gradient and thus power in the associated mass fluxes. This implies either an enhanced export of free energy in form of kinetic energy in case of the river net, or an accelerated reduction of potential energy of infiltrating surface water which implies a reduction free energy in form of capillary binding energy of soil water. We hypothesize (H1) that network like structures act as dissipative structures "serving the purpose" of reducing the relaxation time to a state of lower "free" energy in the entire system. This is because they minimize dissipative losses of kinetic energy along their extent. This faster relaxation towards a state of smaller free energy is deemed to be favorable for mechanic stability of the entire hydrological system because a) mass flows perform due to the enhanced export of kinetic energy less work on the system itself and b) mechanical stress from ponded surface water is quickly reduced by fast infiltration and preferential flow. Our second main objective is, in line with the study of Zehe et al. (2010), the search for thermodynamic optimal hillslope architectures both with respect to the surface density of vertical macropores in soil and with respect to the spatial arrangement of soil types and macropores at the hillslope scale. In line with H1 we suggest (H2) that a hydro-geo-ecosystem is closer to a functional optimum than other possible configurations if it dissipates and exports more of the kinetic energy input from incoming rainfall by redistributing water against internal gradients and exporting water against macroscale geo-potential gradients. Note that H2 does not postulate that functionally optimal hillslope architectures necessarily exist, if they exist H2 implies however that they maximize entropy production and thus reduction of total free energy of the system at a "wisely" selected time scale. The surface density of apparent macropores does for instance control the tradeoff between Hortonian overland flow formation and infiltration, which implies a tradeoff between the amount of kinetic energy input from rainfall that is converted in to power associated with overland flow and power associated with soil water flows depleting gradients in soil water potential. Does this tradeoff imply an optimum surface density of macropores at the hillslope scale in the sense that power in soil water flow is maximized or reduction of free energy is maximized? In case such an optimum hillslope architecture existed, and in case that the evolution of the hydrological systems of interested was indeed in accordance with hypothesis H2, this optimal architecture should allow an acceptable uncalibrated simulation of the systems rainfall -runoff behavior (if the selected model structure can properly represent this architecture). We will address these questions and test the main implications of our hypotheses by means of numerical experiments with the physically based hydrological model CATFLOW. We use behavioral model structures as basic model setup, which have been shown to closely portray system behavior and its architecture in a sense that they reproduce distributed observations of soil moisture and catchment scale discharge and represent the observed structural and textural signatures of soils, flow networks and vegetation. Our test areas are the Weiherbach (Germany) and the Malalcahuello research headwaters (Chile), which are located in distinctly different hydro-climatic and hydro-pedological settings. Within the numerical experiments we will simulate the full concert of hydrological processes at the hillslope and headwater scales for meaningful perturbations of the behavioral model structure and compare them with respect to dynamics of free energy and production of power. These perturbations affect a) the river network and the geomorphology of the Weiherbach catchment, b) surface density of macropores in both catchments c) the spatial arrangement of soils and preferential pathways at the hillslope scale in the Weiherbach catchment. References: Kleidon, A., Zehe, E., Ehret, U., and Scherer, U.: Thermodynamics, maximum power, and the dynamics of preferential river flow structures on continents, Hydrol. Earth Syst. Sci. Discuss., 9, 7317-7378, 10.5194/hessd-9-7317-2012, 2012. Zehe, E., Blume, T., and Blöschl, G.: The principle of 'maximum energy dissipation': a novel thermodynamic perspective on rapid water flow in connected soil structures, Phil. Trans. R. Soc. B, 1-10, doi:10.1098/rstb.2009.0308, 2010.

Cansiglio Karst Plateau: 10 Years of Geodetic-Hydrological Observations in Seismically Active Northeast Italy

NASA Astrophysics Data System (ADS)

Grillo, Barbara; Braitenberg, Carla; Nagy, Ildikó; Devoti, Roberto; Zuliani, David; Fabris, Paolo

2018-04-01

Ten years' geodetic observations (2006-2016) in a natural cave of the Cansiglio Plateau (Bus de la Genziana), a limestone karstic area in northeastern Italy, are discussed. The area is of medium-high seismic risk: a strong earthquake in 1936 below the plateau (M m = 6.2) and the 1976 disastrous Friuli earthquake (M m = 6.5) are recent events. At the foothills of the karstic massif, three springs emerge, with average flow from 5 to 10 m3/s, and which are the sources of a river. The tiltmeter station is set in a natural cavity that is part of a karstic system. From March 2013, a multiparametric logger (temperature, stage, electrical conductivity) was installed in the siphon at the bottom of the cave to discover the underground hydrodynamics. The tilt records include signals induced by hydrologic and tectonic effects. The tiltmeter signals have a clear correlation to the rainfall, the discharge series of the river and the data recorded by multiparametric loggers. Additionally, the data of a permanent GPS station located on the southern slopes of the Cansiglio Massif (CANV) show also a clear correspondence with the river level. The fast water infiltration into the epikarst, closely related to daily rainfall, is distinguished in the tilt records from the characteristic time evolution of the karstic springs, which have an impulsive level increase with successive exponential decay. It demonstrates the usefulness of geodetic measurements to reveal the hydrological response of the karst. One outcome of the work is that the tiltmeters can be used as proxies for the presence of flow channels and the pressure that builds up due to the water flow. With 10 years of data, a new multidisciplinary frontier was opened between the geodetic studies and the karstic hydrogeology to obtain a more complete geologic description of the karst plateau.

Cansiglio Karst Plateau: 10 Years of Geodetic-Hydrological Observations in Seismically Active Northeast Italy

NASA Astrophysics Data System (ADS)

Grillo, Barbara; Braitenberg, Carla; Nagy, Ildikó; Devoti, Roberto; Zuliani, David; Fabris, Paolo

2018-05-01

Ten years' geodetic observations (2006-2016) in a natural cave of the Cansiglio Plateau (Bus de la Genziana), a limestone karstic area in northeastern Italy, are discussed. The area is of medium-high seismic risk: a strong earthquake in 1936 below the plateau ( M m = 6.2) and the 1976 disastrous Friuli earthquake ( M m = 6.5) are recent events. At the foothills of the karstic massif, three springs emerge, with average flow from 5 to 10 m3/s, and which are the sources of a river. The tiltmeter station is set in a natural cavity that is part of a karstic system. From March 2013, a multiparametric logger (temperature, stage, electrical conductivity) was installed in the siphon at the bottom of the cave to discover the underground hydrodynamics. The tilt records include signals induced by hydrologic and tectonic effects. The tiltmeter signals have a clear correlation to the rainfall, the discharge series of the river and the data recorded by multiparametric loggers. Additionally, the data of a permanent GPS station located on the southern slopes of the Cansiglio Massif (CANV) show also a clear correspondence with the river level. The fast water infiltration into the epikarst, closely related to daily rainfall, is distinguished in the tilt records from the characteristic time evolution of the karstic springs, which have an impulsive level increase with successive exponential decay. It demonstrates the usefulness of geodetic measurements to reveal the hydrological response of the karst. One outcome of the work is that the tiltmeters can be used as proxies for the presence of flow channels and the pressure that builds up due to the water flow. With 10 years of data, a new multidisciplinary frontier was opened between the geodetic studies and the karstic hydrogeology to obtain a more complete geologic description of the karst plateau.

Magnitude and frequency data for historic debris flows in Grand Canyon National Park and vicinity, Arizona

USGS Publications Warehouse

Melis, T.S.; Webb, R.H.; Griffiths, P.G.; Wise, T.J.

1995-01-01

Debris flows occur in 529 tributaries of the Colorado River in Grand Canyon between Lees Ferry and Diamond Creek, Arizona (river miles 0 to 225). An episodic type of flash flood, debris flows transport poorly-sorted sediment ranging in size from clay to boulders into the Colorado River. Debris flows create and maintain debris fans and the hundreds of associated riffles and rapids that control the geomorphic framework of the Colorado River downstream from Glen Canyon Dam. Between 1984 and 1994, debris flows created 4 new rapids and enlarged 17 existing rapids and riffles. Debris flows in Grand Canyon are initiated by slope failures that occur during intense rainfall. Three of these mechanisms of slope failure are documented. Failures in weathered bedrock, particularly in the Hermit Shale and Supai Group, have initiated many historic debris flows in Grand Canyon. A second mechanism, termed the fire-hose effect, occurs when runoff pours over cliffs onto unconsolidated colluvial wedges, triggering a failure. A third initiation mechanism occurs when intense precipitation causes failures in colluvium overlying bedrock. Multiple source areas and extreme topographic relief in Grand Canyon commonly result in combinations of these three initiation mechanisms. Interpretation of 1,107 historical photographs spanning 120 years, supplemented with aerial photography made between 1935 and 1994, yielded information on the frequency of debris flows in 168 of the 529 tributaries (32 percent) of the Colorado River in Grand Canyon. Of the 168 tributaries, 96 contain evidence of debris flows that have occurred since 1872, whereas 72 tributaries have not had a debris flow during the last century. The oldest debris flow we have documented in Grand Canyon occurred 5,400 years ago in an unnamed tributary at river mile 63.3-R. Our results indicate that the frequency of debris flows ranges from one every 10 to 15 years in certain eastern tributaries, to less than one per century in other drainage basins. On average, debris flows may recur approximately every 30 to 50 years in individual tributaries, although adjacent tributaries may have considerably different histories. Peak discharges were estimated in 18 drainages for debris flows that occurred between 1939 and 1994. Typically, discharges range from about 100 to 300 cubic meters per second (m3/s). The largest debris flow in Grand Canyon during the last century, which occurred in Prospect Canyon in 1939, had a peak discharge of about 1,000 m3/s. Debris-flow deposits generally contain 15 to 30 percent sand-and-finer sediment; however, the variability of sand-and-finer sediment contained by recent debris flows is large. Reconstitution of debris-flow samples indicates a range in water content of 10 to 25 percent by weight;. Before flow regulation of the Colorado River began, debris fans aggraded by debris flows were periodically reworked by large river floods that may have been as large as 11,000 m3/s. Impoundment of the river by Glen Canyon Dam in 1963, and subsequent operation of the reservoir have reduced the magnitude of these floods. Flow releases from the dam since 1963 have only partly reworked recently-aggraded debris fans. Significant reworking of new debris-flow deposits now occurs only during river discharges higher than typical power plant releases, which currently range between 142 and 510 m3/s.

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.

Soil erosion assessment of a Himalayan river basin using TRMM data

NASA Astrophysics Data System (ADS)

Pandey, A.; Mishra, S. K.; Gautam, A. K.; Kumar, D.

2015-04-01

In this study, an attempt has been made to assess the soil erosion of a Himalayan river basin, the Karnali basin, Nepal, using rainfall erosivity (R-factor) derived from satellite-based rainfall estimates (TRMM-3B42 V7). Average annual sediment yield was estimated using the well-known Universal Soil Loss Equation (USLE). The eight-year annual average rainfall erosivity factor (R) for the Karnali River basin was found to be 2620.84 MJ mm ha-1 h-1 year-1. Using intensity-erosivity relationships and eight years of the TRMM daily rainfall dataset (1998-2005), average annual soil erosion was also estimated for Karnali River basin. The minimum and maximum values of the rainfall erosivity factor were 1108.7 and 4868.49 MJ mm ha-1 h-1 year-1, respectively, during the assessment period. The average annual soil loss of the Karnali River basin was found to be 38.17 t ha-1 year-1. Finally, the basin area was categorized according to the following scale of erosion severity classes: Slight (0 to 5 t ha-1 year-1), Moderate (5 to 10 t ha-1 year-1), High (10 to 20 t ha-1 year-1), Very High (20 to 40 t ha-1 year-1), Severe (40 to 80 t ha-1 year-1) and Very Severe (>80 t ha-1 year-1). About 30.86% of the river basin area was found to be in the slight erosion class. The areas covered by the moderate, high, very high, severe and very severe erosion potential zones were 13.09%, 6.36%, 11.09%, 22.02% and 16.64% respectively. The study revealed that approximately 69% of the Karnali River basin needs immediate attention from a soil conservation point of view.

Postwildfire debris-flow hazard assessment of the area burned by the 2013 West Fork Fire Complex, southwestern Colorado

USGS Publications Warehouse

Verdin, Kristine L.; Dupree, Jean A.; Stevens, Michael R.

2013-01-01

This report presents a preliminary emergency assessment of the debris-flow hazards from drainage basins burned by the 2013 West Fork Fire Complex near South Fork in southwestern Colorado. Empirical models derived from statistical evaluation of data collected from recently burned basins throughout the intermountain western United States were used to estimate the probability of debris-flow occurrence, potential volume of debris flows, and the combined debris-flow hazard ranking along the drainage network within and just downstream from the burned area, and to estimate the same for 54 drainage basins of interest within the perimeter of the burned area. Input data for the debris-flow models included topographic variables, soil characteristics, burn severity, and rainfall totals and intensities for a (1) 2-year-recurrence, 1-hour-duration rainfall, referred to as a 2-year storm; (2) 10-year-recurrence, 1-hour-duration rainfall, referred to as a 10-year storm; and (3) 25-year-recurrence, 1-hour-duration rainfall, referred to as a 25-year storm. Estimated debris-flow probabilities at the pour points of the 54 drainage basins of interest ranged from less than 1 to 65 percent in response to the 2-year storm; from 1 to 77 percent in response to the 10-year storm; and from 1 to 83 percent in response to the 25-year storm. Twelve of the 54 drainage basins of interest have a 30-percent probability or greater of producing a debris flow in response to the 25-year storm. Estimated debris-flow volumes for all rainfalls modeled range from a low of 2,400 cubic meters to a high of greater than 100,000 cubic meters. Estimated debris-flow volumes increase with basin size and distance along the drainage network, but some smaller drainages also were predicted to produce substantial debris flows. One of the 54 drainage basins of interest had the highest combined hazard ranking, while 9 other basins had the second highest combined hazard ranking. Of these 10 basins with the 2 highest combined hazard rankings, 7 basins had predicted debris-flow volumes exceeding 100,000 cubic meters, while 3 had predicted probabilities of debris flows exceeding 60 percent. The 10 basins with high combined hazard ranking include 3 tributaries in the headwaters of Trout Creek, four tributaries to the West Fork San Juan River, Hope Creek draining toward a county road on the eastern edge of the burn, Lake Fork draining to U.S. Highway 160, and Leopard Creek on the northern edge of the burn. The probabilities and volumes for the modeled storms indicate a potential for debris-flow impacts on structures, reservoirs, roads, bridges, and culverts located within and immediately downstream from the burned area. U.S. Highway 160, on the eastern edge of the burn area, also is susceptible to impacts from debris flows.

A field study of colloid transport in surface and subsurface flows

NASA Astrophysics Data System (ADS)

Zhang, Wei; Tang, Xiang-Yu; Xian, Qing-Song; Weisbrod, Noam; Yang, Jae E.; Wang, Hong-Lan

2016-11-01

Colloids have been recognized to enhance the migration of strongly-sorbing contaminants. However, few field investigations have examined combined colloid transport via surface runoff and subsurface flows. In a headwater catchment of the upper Yangtze River, a 6 m (L) by 4 m (W) sloping (6°) farmland plot was built by cement walls to form no-flow side boundaries. The plot was monitored in the summer of 2014 for the release and transport of natural colloids via surface runoff and subsurface flows (i.e., the interflow from the soil-mudrock interface and fracture flow from the mudrock-sandstone interface) in response to rain events. The water sources of the subsurface flows were apportioned to individual rain events using a two end-member model (i.e., mobile pre-event soil water extracted by a suction-cup sampler vs. rainwater (event water)) based on δ18O measurements. For rain events with high preceding soil moisture, mobile pre-event soil water was the main contributor (generally >60%) to the fracture flow. The colloid concentration in the surface runoff was 1-2 orders of magnitude higher than that in the subsurface flows. The lowest colloid concentration was found in the subsurface interflow, which was probably the result of pore-scale colloid straining mechanisms. The rainfall intensity and its temporal variation govern the dynamics of the colloid concentrations in both surface runoff and subsurface flows. The duration of the antecedent dry period affected not only the relative contributions of the rainwater and the mobile pre-event soil water to the subsurface flows but also the peak colloid concentration, particularly in the fracture flow. The <10 μm fine colloid size fraction accounted for more than 80% of the total suspended particles in the surface runoff, while the colloid size distributions of both the interflow and the fracture flow shifted towards larger diameters. These results highlight the need to avoid the application of strongly-sorbing agrochemicals (e.g., pesticides, phosphorus fertilizers) immediately before rainfall following a long no-rain period because their transport in association with colloids may occur rapidly over long distances via both surface runoff and subsurface flows with rainfall.

Meteorological influences on algal bloom potential in a nutrient-rich blackwater river

EPA Science Inventory

The effect of variability in rainfall on the potential for algal blooms was examined for the St. Johns River in northeast Florida. Water chemistry and phytoplankton data were collected at selected sites monthly from 1993 through 2003. Information on rainfall and estimates ofw at...

Yangon River Geomorphology Identification and its Enviromental Imapacts Analsysi by Optical and Radar Sensing Techniques

NASA Astrophysics Data System (ADS)

Lwin, A.; Khaing, M. M.

2012-07-01

The Yangon river, also known as the Rangoon river, is about 40 km long (25miles), and flows from southern Myanmar as an outlet of the Irrawaddy (Ayeyarwady) river into the Ayeyarwady delta. The Yangon river drains the Pegu Mountains; both the Yangon and the Pathein rivers enter the Ayeyarwady at the delta. Fluvial geomorphology is based primarily on rivers of manageable dimensions. The emphasis is on geomorphology, sedimentology of Yangon river and techniques for their identification and management. Present techniques such as remote sensing have made it easier to investigate and interpret in details analysis of river geomorphology. In this paper, attempt has been made the complicated issues of geomorphology, sedimentation patterns and management of river system and evolution studied. The analysis was carried out for the impact of land use/ land cover (LULC) changes on stream flow patterns. The hydrologic response to intense, flood producing rainfall events bears the signatures of the geomorphic structure of the channel network and of the characteristic slope lengths defining the drainage density of the basin. The interpretation of the hydrologic response as the travel time distribution of a water particle randomly injected in a distributed manner across the landscape inspired many geomorphic insights. In 2008, Cyclone Nargis was seriously damaged to mangrove area and its biodiversity system in and around of Yangon river terraces. A combination of digital image processing techniques was employed for enhancement and classification process. It is observed from the study that middle infra red band (0.77mm - 0.86mm) is highly suitable for mapping mangroves. Two major classes of mangroves, dense and open mangroves were delineated from the digital data.

Tempo-spatial dynamics of water quality and its response to river flow in estuary of Taihu Lake based on GOCI imagery.

PubMed

Du, Chenggong; Li, Yunmei; Wang, Qiao; Liu, Ge; Zheng, Zhubin; Mu, Meng; Li, Yuan

2017-12-01

Knowledge of tempo-spatial dynamics of water quality and its response to river flow is important for the management of lake water quality because river discharge associated with rainstorms can be an important source of pollutants to the estuary. Total phosphorus (TP), chlorophyll a (Chl-a), and total suspended matter (TSM) are important indexes of water quality and important factors influencing eutrophication and algal blooms. In this study, remote sensing was used to monitor these indexes to investigate the effects of river discharge on the estuary of Taihu Lake by the largest inflow river which is Chendong River using a total of 136 Geostationary Ocean Color Images (GOCI). In situ datasets collected during the four cruise experiments on Taihu Lake between 2011 and 2015 were used to develop the TP, Chl-a, and TSM inversion models based on simple empirical algorithms: 154 points for TP (mg/L), 114 for Chl-a (μg/L), and 181 for TSM (mg/L). The spatial and temporal changes of the concentration of the three parameters in the Chendong River estuary were analyzed by combining the GOCI data, the flow of the Chendong River, and meteorological data throughout the year in 2014. The several key findings are as follows: (1) In summer and autumn, TP, Chl-a, and TSM contents were significantly higher than in winter and spring. TP and Chl-a have a few similar distribution characteristics. And organic suspended matter in summer was the main reason for the increase of the TSM concentration. (2) The severe surface erosion in the rivers cannot be ignored; the high erodibility is an important factor in the increase of TP and TSM concentrations in the estuary. The concentration of the water quality parameter showed exponential decay with distance from the shore. The concentration decreased slowly after 12 km and then remained essentially constant. (3) TP content in the Chendong River estuary decreased under steady flow inputs and dramatically increased when the flow became large. The increase in Chl-a content was linked to higher levels of TP and good weather conditions after the rain event. Higher flow rates mainly play a dilution role for the Chl-a concentration. Erosion of the surface soil via rainfall is a major source of TSM to the estuary. This paper firstly analyzes tempo-spatial dynamics of water quality and its response to river flow in estuary of Taihu Lake, helps to further understand the impact of river input on lake water quality, and is important for lake eutrophication.

Summer rainfall over the southwestern Tibetan Plateau controlled by deep convection over the Indian subcontinent

PubMed Central

Dong, Wenhao; Lin, Yanluan; Wright, Jonathon S.; Ming, Yi; Xie, Yuanyu; Wang, Bin; Luo, Yong; Huang, Wenyu; Huang, Jianbin; Wang, Lei; Tian, Lide; Peng, Yiran; Xu, Fanghua

2016-01-01

Despite the importance of precipitation and moisture transport over the Tibetan Plateau for glacier mass balance, river runoff and local ecology, changes in these quantities remain highly uncertain and poorly understood. Here we use observational data and model simulations to explore the close relationship between summer rainfall variability over the southwestern Tibetan Plateau (SWTP) and that over central-eastern India (CEI), which exists despite the separation of these two regions by the Himalayas. We show that this relationship is maintained primarily by ‘up-and-over' moisture transport, in which hydrometeors and moisture are lifted by convective storms over CEI and the Himalayan foothills and then swept over the SWTP by the mid-tropospheric circulation, rather than by upslope flow over the Himalayas. Sensitivity simulations confirm the importance of up-and-over transport at event scales, and an objective storm classification indicates that this pathway accounts for approximately half of total summer rainfall over the SWTP. PMID:26948491

Water-quality characteristics indicative of wastewater in selected streams in the upper Neuse River Basin, Durham and Orange Counties, North Carolina, from 2004 to 2013

USGS Publications Warehouse

Ferrell, Gloria M.; Yearout, Matthew S.; Grimes, Barbara H.; Graves, Alexandria K.; Fitzgerald, Sharon A.; Meyer, Michael T.

2014-01-01

During the third phase of data collection, May 2012 to January 2013, data were collected to address the suitability of optical brighteners as tracers of wastewater in small streams during streamflow recession. Samples were collected at five small streams following periods of rainfall and analyzed for optical brighteners, specific conductance nutrients, and selected hormones. Optical brighteners were absent in the undeveloped catchment but were present in the recession period after rainfall events in catchments with centralized though possibly leaky sewage treatment and areas with onsite treatment. Sand filter systems in areas with onsite treatment appear to change the effluent flow and retention characteristics such that optical brighteners were present both before and after rainfall events. Nitrate plus nitrite, as nitrogen concentrations in samples from this last study phase generally were larger than those collected during baseflow conditions in the previous phases of this study.

Temporal Dynamics in the Concentration, Flux, and Optical Properties of Tree-derived Dissolved Organic Matter (Tree-DOM) in an Epiphyte-laden Oak-cedar Forest.

NASA Astrophysics Data System (ADS)

Whitetree, A.; Van Stan, J. T., II; Wagner, S.; Guillemette, F.; Lewis, J.; Silva, L.; Stubbins, A.

2017-12-01

Studies on the fate and transport of dissolved organic matter (DOM) along the rainfall-to-discharge flow pathway typically begin in streams or soils, neglecting the initial enrichment of rainfall with DOM during contact with plant canopies. However, rain water can gather significant amounts of tree-derived DOM (tree-DOM) when it drains from the canopy, as throughfall, and down the stem, as stemflow. We examined the temporal variability of event-scale tree-DOM concentrations, yield, and optical (light absorbance and fluorescence) characteristics from an epiphyte-laden Quercus virginiana-Juniperus virginiana forest on Skidaway Island, Savannah, Georgia (USA). All tree-DOM fluxes were highly enriched compared to rainfall and epiphytes further increased concentrations. Stemflow DOC concentrations were greater than throughfall across study species, yet larger throughfall water yields produced greater DOC yields versus stemflow. Tree-DOM optical characteristics indicate it is aromatic-rich with FDOM dominated by humic-like fluorescence, containing 10-20% protein-like (tryptophan-like) fluorescence. Storm size was the only storm condition that strongly correlated with tree-DOM concentration and flux; however, throughfall and stemflow optical characteristics varied little across a wide range of storm conditions (from low magnitude events to intense tropical storms). Annual tree-DOM yields from the study forest (0.8-46 g-C m-2 yr-1) compared well to other yields along the rainfall-to- discharge flow pathway, exceeding DOM yields from some river watersheds.

Hydrological influences on the water quality trends in Tamiraparani Basin, South India.

PubMed

Ravichandran, S

2003-09-01

Water quality variables--Turbidity, pH, Electrical Conductivity (EC), Chlorides and Total Hardness (TH) were monitored at a downstream location in the Tamiraparani River during 1978-1992. The observations were made at weekly intervals in a water treatment and supply plant using standard methods. Graphical and statistical analyses were used for data exploration, trend detection and assessment. Box-Whisker plots of annual and seasonal changes in variables indicated apparent trends being present in the data and their response to the seasonal influence of the monsoon rainfall. Further, the examination of the median values of the variables indicated that changes in the direction of trend occurred during 1985-1986, especially in pH, EC and TH. The statistical analyses were done using non-parametric methods, the ANCOVA on rank transformed data and the Seasonal Man-Kendall test. The presence of monotonic trend in all the water quality variables was confirmed, however, with independent direction of change. The trend line was fitted by the method of least squares. The estimated values indicated significant increases in EC (28 microS cm(-1)) while significant decreases were observed in turbidity (90 NTU), pH (0.78), and total hardness (23 ppm) in a span of 15 years. The changes induced in river flow by the addition of a stabilizing reservoir, the influence of seasonal and spatial pattern of monsoon rainfall across the river basin and the increased agriculture appear causative factors for the water quality trends seen in the Tamiraparani River system.

Determination of first flush criteria using dynamic EMCs (event mean concentrations) on highway stormwater runoff.

PubMed

Kim, L H; Jeong, S M; Ko, S O

2007-01-01

Recently the Ministry of Environment in Korea has developed the total maximum daily load program in accordance with the target pollutant and its concentration goal on four major large rivers. Since the program is largely related to regional development, nonpoint source control is both important and topical. Of the various nonpoint sources, highways are stormwater intensive land uses since they are impervious and have high pollutant mass emissions from vehicular activity. The event mean concentration (EMC) is useful in estimating the loadings to receiving water bodies. However, the EMC does not provide information on the time varying changes in pollutant concentration or mass emissions, which are often important for best management practice development, or understanding shock loads. Therefore, in this study a new concept, the dynamic EMC determination method, will be introduced to clearly verify the relationship between EMC and the first flush effect. Three monitoring sites in Daejeon metropolitan city areas were equipped with an automatic rainfall gauge and a flow meter for accumulating the data such as rainfall and runoff flow. The dynamic EMC method was applied to more than 17 events, and the improved first flush criteria were determined on the ranges of storm duration and accumulated rainfall.

Modeling the effects of river flow on population dynamics of piping plovers (Charadrius melodus) and least terns (Sternula antillarum) nesting on the Missouri River

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

Buenau, Kate E.; Hiller, Tim L.; Tyre, Andrew J.

Humans make extensive use of rivers and floodplains for economic benefits including agriculture, hydropower, commerce and recreation. Economic development of floodplains subsequently requires control of river levels to avoid flood damage. This process began in the Missouri River basin in the 1890s with the construction of a series of hydropower dams in Montana and escalated to new levels with the approval of the Pick-Sloan plan in the 1944 Flood Control Act. Maximizing these human uses of the river led to changes in and losses of hydrological and ecological processes, ultimately resulting in the federal listing of three fish and wildlifemore » species under the Endangered Species Act: the pallid sturgeon (Scaphirhyncus albus; 1983), the piping plover (Charadrius melodus; 1984), and the interior population of least tern (Sternula antillarum; 1985). The listing of terns and plovers did not affect river management until the United States Army Corps of Engineers (USACE) proposed to modify the governing document of the Missouri River Mainstem System, the Master Manual, a process which was completed in 2003. Although there was little disagreement over the habitat conditions that terns and plovers used for nesting, there was substantial disagreement over the amount of habitat necessary for terns and plovers to meet population recovery goals. Answering this question requires forecasting species-specific population responses to dynamic habitat affected by both human actions (reservoir management and habitat restoration) and natural variability in precipitation. Piping plovers and least terns nest along the Missouri River from Fort Peck, Montana to just north of Sioux City, Iowa (Figure 1). Both species prefer to nest on sand and fine gravel substrates with no or sparse vegetation cover (Prindiville Gaines and Ryan, 1988; Sherfy et al., 2012), such as riverine sandbars (emergent sandbar habitat; ESH). Piping plovers also nest on reservoir shorelines that lack vegetation cover (Anteau et al., 2012). The amount of ESH available for nesting in a given year is strongly affected by the amount of water entering the Missouri River system through precipitation and the management of water flow from six reservoirs operated by the USACE on the mainstem Missouri River. Prior to the construction of dams, the Missouri River experienced bimodal peak flows in spring and early summer in concordance with the melting of plains and mountain snowpack (Galat and Lipkin, 2000). Flows decreased during summer months, with river stage then dependent upon rainfall. The combination of consistent high flows and occasional extreme high flows, together with the meandering characteristic of the river, regularly reshaped and scoured vegetation from ESH.« less

Mountain river meanders and typhoon strike frequency in the western Pacific

NASA Astrophysics Data System (ADS)

Stark, C. P.; Barbour, J.; Hsieh, M.; Hovius, N.; Jen, C.; Chen, M.

2004-12-01

Bedrock-floored mountain rivers are shaped by erosion processes that ultimately control the evolution of the landscape on geological time scales. In mountains across the western Pacific, meanders in bedrock channels are common and often emerge during incision rather than inherit their sinuosity from a past alluvial form. Incising emergent meanders are important because they reveal a process of lateral channel erosion at least as fast as the vertical rate erosion. Here we report a remarkable link between incised meander development and typhoon strike frequency, a good proxy for extreme rainfall and flood discharge. Using satellite imagery, shuttle-radar topographic data and a 58~year inventory of typhoon tracks, we mapped meander abundance and quantified regional densities of mountain river sinuosity and typhoon strikes. Our analysis shows that eroding meanders are most common in the typhoon-prone islands of Japan, Taiwan and the Philippines, and in rivers incising weak lithologies. One might expect that the faster the erosion rate, the greater the meandering, but we have found that monthly mean rainfall - and therefore mean discharge - correlates very poorly with sinuosity. Instead, the variability of rainfall, and presumably discharge, about the mean explains bedrock meander development much better. Mountain river sinuosity, for geologically similar bedrock, increases in a roughly linear fashion with typhoon strike frequency. The coefficient of variation of monthly rainfall (standard deviation normalized by the mean) exhibits a similar trend. We deduce that extreme flood discharge, e.g. driven by typhoon rainfall, accelerates lateral erosion rates and spurs meander development in mountain rivers.

Coastal Ocean Variability Off the Coast of Taiwan in Response toTyphoon Morakot: River Forcing, Atmospheric Forcing, and Cold Dome Dynamics

DTIC Science & Technology

2014-09-01

very short time period and in this research, we model and study the effects of this rainfall on Taiwan?s coastal oceans as a result of river discharge...model and study the effects of this rainfall on Taiwan’s coastal oceans as a result of river discharge. We do this through the use of a river discharge... Effects of Footprint Shape on the Bulk Mixing Model . . . . . . . . . 57 4.2 Effects of the Horizontal Extent of the Bulk Mixing Model . . . . . . 59

Rainfall control of debris-flow triggering in the Réal Torrent, Southern French Prealps

NASA Astrophysics Data System (ADS)

Bel, Coraline; Liébault, Frédéric; Navratil, Oldrich; Eckert, Nicolas; Bellot, Hervé; Fontaine, Firmin; Laigle, Dominique

2017-08-01

This paper investigates the occurrence of debris flow due to rainfall forcing in the Réal Torrent, a very active debris flow-prone catchment in the Southern French Prealps. The study is supported by a 4-year record of flow responses and rainfall events, from three high-frequency monitoring stations equipped with geophones, flow stage sensors, digital cameras, and rain gauges measuring rainfall at 5-min intervals. The classic method of rainfall intensity-duration (ID) threshold was used, and a specific emphasis was placed on the objective identification of rainfall events, as well as on the discrimination of flow responses observed above the ID threshold. The results show that parameters used to identify rainfall events significantly affect the ID threshold and are likely to explain part of the threshold variability reported in the literature. This is especially the case regarding the minimum duration of rain interruption (MDRI) between two distinct rainfall events. In the Réal Torrent, a 3-h MDRI appears to be representative of the local rainfall regime. A systematic increase in the ID threshold with drainage area was also observed from the comparison of the three stations, as well as from the compilation of data from experimental debris-flow catchments. A logistic regression used to separate flow responses above the ID threshold, revealed that the best predictors are the 5-min maximum rainfall intensity, the 48-h antecedent rainfall, the rainfall amount and the number of days elapsed since the end of winter (used as a proxy of sediment supply). This emphasizes the critical role played by short intense rainfall sequences that are only detectable using high time-resolution rainfall records. It also highlights the significant influence of antecedent conditions and the seasonal fluctuations of sediment supply.

Surface water / groundwater interactions and their spatial variability, an example from the Avon River, South-East Australia

NASA Astrophysics Data System (ADS)

Hofmann, Harald; Cartwright, Ian; Gilfedder, Benjamin

2013-04-01

Understanding the interaction between river water and regional groundwater has significant importance for water management and resource allocation. The dynamics of groundwater/surface water interactions also have implications for ecosystems, pollutant transport, and the quality and quantity of water supply for domestic, agriculture and recreational purposes. After general assumptions and for management purposes rivers are classified in loosing or gaining rivers. However, many streams alternate between gaining and loosing conditions on a range of temporal and spatial scales due to factors including: 1) river water levels in relation to groundwater head; 2) the relative response of the groundwater and river system to rainfall; 3) heterogeneities in alluvial sediments that can lead to alternation of areas of exfiltration and infiltration along a river stretch; and 4) differences in near river reservoirs, such parafluvial flow and bank storage. Spatial variability of groundwater discharge to rivers is rarely accounted for as it is assumed that groundwater discharge is constant over river stretches and only changes with the seasonal river water levels. Riverbank storage and parafluvial flow are generally not taken in consideration. Bank storage has short-term cycles and can contribute significantly to the total discharge, especially after flood events. In this study we used hydrogeochemistry to constrain spatial and temporal differences in gaining and loosing conditions in rivers and investigate potential sources. Environmental tracers, such as major ion chemistry, stables isotopes and Radon are useful tools to characterise these sources. Surface water and ground water samples were taken in the Avon River in the Gippsland Basin, Southwest Australia. Increasing TDS along the flow path from 70 to 250 mg/l, show that the Avon is a net gaining stream. The radon concentration along the river is variable and does not show a general increase downstream, but isolated peaks in some areas instead. Radon concentrations are in general low (under 0.5 Bq/l), but rise significantly when groundwater discharges to the river (up to 3 Bq/l). By using high resolution radon mapping with a water-air-gas-exchanger in combination with EC mapping on a boat we were able to show that groundwater discharge to the river is diffuse on river reaches of about 1 km length where it occurs. The discharge areas are along large alluvial riverbed deposits and are likely to be a mixture of local groundwater and parafluvial flow. High resolution radon mapping has only been used in coastal areas and this is the first study where the method was applied to river systems.

Climate Change and River Ecosystems: Protection and Adaptation Options

NASA Astrophysics Data System (ADS)

Palmer, Margaret A.; Lettenmaier, Dennis P.; Poff, N. Leroy; Postel, Sandra L.; Richter, Brian; Warner, Richard

2009-12-01

Rivers provide a special suite of goods and services valued highly by the public that are inextricably linked to their flow dynamics and the interaction of flow with the landscape. Yet most rivers are within watersheds that are stressed to some extent by human activities including development, dams, or extractive uses. Climate change will add to and magnify risks that are already present through its potential to alter rainfall, temperature, runoff patterns, and to disrupt biological communities and sever ecological linkages. We provide an overview of the predicted impacts based on published studies to date, discuss both reactive and proactive management responses, and outline six categories of management actions that will contribute substantially to the protection of valuable river assets. To be effective, management must be place-based focusing on local watershed scales that are most relevant to management scales. The first priority should be enhancing environmental monitoring of changes and river responses coupled with the development of local scenario-building exercises that take land use and water use into account. Protection of a greater number of rivers and riparian corridors is essential, as is conjunctive groundwater/surface water management. This will require collaborations among multiple partners in the respective river basins and wise land use planning to minimize additional development in watersheds with valued rivers. Ensuring environmental flows by purchasing or leasing water rights and/or altering reservoir release patterns will be needed for many rivers. Implementing restoration projects proactively can be used to protect existing resources so that expensive reactive restoration to repair damage associated with a changing climate is minimized. Special attention should be given to diversifying and replicating habitats of special importance and to monitoring populations at high risk or of special value so that management interventions can occur if the risks to habitats or species increase significantly over time.

The development of an hourly gridded rainfall product for hydrological applications in England and Wales

NASA Astrophysics Data System (ADS)

Liguori, Sara; O'Loughlin, Fiachra; Souvignet, Maxime; Coxon, Gemma; Freer, Jim; Woods, Ross

2014-05-01

This research presents a newly developed observed sub-daily gridded precipitation product for England and Wales. Importantly our analysis specifically allows a quantification of rainfall errors from grid to the catchment scale, useful for hydrological model simulation and the evaluation of prediction uncertainties. Our methodology involves the disaggregation of the current one kilometre daily gridded precipitation records available for the United Kingdom[1]. The hourly product is created using information from: 1) 2000 tipping-bucket rain gauges; and 2) the United Kingdom Met-Office weather radar network. These two independent datasets provide rainfall estimates at temporal resolutions much smaller than the current daily gridded rainfall product; thus allowing the disaggregation of the daily rainfall records to an hourly timestep. Our analysis is conducted for the period 2004 to 2008, limited by the current availability of the datasets. We analyse the uncertainty components affecting the accuracy of this product. Specifically we explore how these uncertainties vary spatially, temporally and with climatic regimes. Preliminary results indicate scope for improvement of hydrological model performance by the utilisation of this new hourly gridded rainfall product. Such product will improve our ability to diagnose and identify structural errors in hydrological modelling by including the quantification of input errors. References [1] Keller V, Young AR, Morris D, Davies H (2006) Continuous Estimation of River Flows. Technical Report: Estimation of Precipitation Inputs. in Agency E (ed.). Environmental Agency.

Variation of Probable Maximum Precipitation in Brazos River Basin, TX

NASA Astrophysics Data System (ADS)

Bhatia, N.; Singh, V. P.

2017-12-01

The Brazos River basin, the second-largest river basin by area in Texas, generates the highest amount of flow volume of any river in a given year in Texas. With its headwaters located at the confluence of Double Mountain and Salt forks in Stonewall County, the third-longest flowline of the Brazos River traverses within narrow valleys in the area of rolling topography of west Texas, and flows through rugged terrains in mainly featureless plains of central Texas, before its confluence with Gulf of Mexico. Along its major flow network, the river basin covers six different climate regions characterized on the basis of similar attributes of vegetation, temperature, humidity, rainfall, and seasonal weather changes, by National Oceanic and Atmospheric Administration (NOAA). Our previous research on Texas climatology illustrated intensified precipitation regimes, which tend to result in extreme flood events. Such events have caused huge losses of lives and infrastructure in the Brazos River basin. Therefore, a region-specific investigation is required for analyzing precipitation regimes along the geographically-diverse river network. Owing to the topographical and hydroclimatological variations along the flow network, 24-hour Probable Maximum Precipitation (PMP) was estimated for different hydrologic units along the river network, using the revised Hershfield's method devised by Lan et al. (2017). The method incorporates the use of a standardized variable describing the maximum deviation from the average of a sample scaled by the standard deviation of the sample. The hydrometeorological literature identifies this method as more reasonable and consistent with the frequency equation. With respect to the calculation of stable data size required for statistically reliable results, this study also quantified the respective uncertainty associated with PMP values in different hydrologic units. The corresponding range of return periods of PMPs in different hydrologic units was further evaluated using the inverse CDF functions of the most appropriate probability distributions. The analysis will aid regional water boards in designing hydraulic structures, such as dams, spillways, levees, and in identifying and implementing prevention and control mechanisms for extreme flood events resulting from the PMPs.

Dynamic modeling of the Ganga river system: impacts of future climate and socio-economic change on flows and nitrogen fluxes in India and Bangladesh.

PubMed

Whitehead, P G; Sarkar, S; Jin, L; Futter, M N; Caesar, J; Barbour, E; Butterfield, D; Sinha, R; Nicholls, R; Hutton, C; Leckie, H D

2015-06-01

This study investigates the potential impacts of future climate and socio-economic change on the flow and nitrogen fluxes of the Ganga river system. This is the first basin scale water quality study for the Ganga considering climate change at 25 km resolution together with socio-economic scenarios. The revised dynamic, process-based INCA model was used to simulate hydrology and water quality within the complex multi-branched river basins. All climate realizations utilized in the study predict increases in temperature and rainfall by the 2050s with significant increase by the 2090s. These changes generate associated increases in monsoon flows and increased availability of water for groundwater recharge and irrigation, but also more frequent flooding. Decreased concentrations of nitrate and ammonia are expected due to increased dilution. Different future socio-economic scenarios were found to have a significant impact on water quality at the downstream end of the Ganga. A less sustainable future resulted in a deterioration of water quality due to the pressures from higher population growth, land use change, increased sewage treatment discharges, enhanced atmospheric nitrogen deposition, and water abstraction. However, water quality was found to improve under a more sustainable strategy as envisaged in the Ganga clean-up plan.

Combined use of isotopic and hydrometric data to conceptualize ecohydrological processes in a high-elevation tropical ecosystem

USGS Publications Warehouse

Mosquera, Giovanny M; Celleri, Rolando; Lazo, Patricio X; Vache, Kellie B; Perakis, Steven; Crespo, Patricio

2016-01-01

Few high-elevation tropical catchments worldwide are gauged and even fewer are studied using combined hydrometric and isotopic data. Consequently, we lack information needed to understand processes governing rainfall-runoff dynamics and to predict their influence on downstream ecosystem functioning. To address this need, we present a combination of hydrometric and water stable isotopic observations in the wet Andean páramo ecosystem of the Zhurucay Ecohydrological Observatory (7.53 km2). The catchment is located in the Andes of south Ecuador between 3400 and 3900 m a.s.l. Water samples for stable isotopic analysis were collected during 2 years (May 2011 – May 2013), while rainfall and runoff measurements were continuously recorded since late 2010. The isotopic data reveal that Andosol soils predominantly situated on hillslopes drain laterally to Histosols (Andean páramo wetlands) mainly located at the valley bottom. Histosols, in turn, feed water to creeks and small rivers throughout the year, establishing hydrologic connectivity between wetlands and the drainage network. Runoff is primarily comprised of pre-event water stored in the Histosols, which is replenished by rainfall that infiltrates through the Andosols. Contributions from the mineral horizon and the top of the fractured bedrock are small and only seem to influence discharge in small catchments during low flow generation (non-exceedance flows < Q35). Variations in source contributions are controlled by antecedent soil moisture, rainfall intensity, and duration of rainy periods. Saturated hydraulic conductivity of the soils, higher than the year-round low precipitation intensity, indicates that Hortonian overland flow rarely occurs during high intensity precipitation events. Deep groundwater contributions to discharge seem to be minimal. These results suggest that, in this high-elevation tropical ecosystem: 1) subsurface flow is a dominant hydrological process and 2) (Histosols) wetlands are the major source of stream runoff. Our study highlights that detailed isotopic characterization during short time periods provides valuable information about ecohydrological processes in regions where very few basins are gauged.

Seasonal variation of nitrogen-concentration in the surface water and its relationship with land use in a catchment of northern China.

PubMed

Chen, Li-ding; Peng, Hong-jia; Fu, Bo-Jie; Qiu, Jun; Zhang, Shu-rong

2005-01-01

Surface waters can be contaminated by human activities in two ways: (1) by point sources, such as sewage treatment discharge and storm-water runoff; and (2) by non-point sources, such as runoff from urban and agricultural areas. With point-source pollution effectively controlled, non-point source pollution has become the most important environmental concern in the world. The formation of non-point source pollution is related to both the sources such as soil nutrient, the amount of fertilizer and pesticide applied, the amount of refuse, and the spatial complex combination of land uses within a heterogeneous landscape. Land-use change, dominated by human activities, has a significant impact on water resources and quality. In this study, fifteen surface water monitoring points in the Yuqiao Reservoir Basin, Zunhua, Hebei Province, northern China, were chosen to study the seasonal variation of nitrogen concentration in the surface water. Water samples were collected in low-flow period (June), high-flow period (July) and mean-flow period (October) from 1999 to 2000. The results indicated that the seasonal variation of nitrogen concentration in the surface water among the fifteen monitoring points in the rainfall-rich year is more complex than that in the rainfall-deficit year. It was found that the land use, the characteristics of the surface river system, rainfall, and human activities play an important role in the seasonal variation of N-concentration in surface water.

Spatial and temporal dynamic of surface water and vegetation dynamic using remotely sensed data in the Murray -Darling Basin, Australia

NASA Astrophysics Data System (ADS)

Tulbure, M. G.; Kingsford, R.; Broich, M.

2012-12-01

Australia is the driest inhabited continent and river systems have highly variable flows in space and time. The Murray-Darling Basin (MDB), a catchment covering 14% of the continent contains the nation's largest rivers and important groundwater systems. The basin has highly variable rainfall patterns in space and time and the vast majority of rainfall is lost to evapotranspiration with only 4% becoming runoff. The basin is home to several wetlands of high hydrological and ecological value with a number of them being recognised as wetlands of international importance. The basin produces more than a third of Australia's food supply, making it the most important agricultural area in the country. However, variation in surface and ground water availability exacerbated by a long period of drought, combined with high water demands for irrigation and in several major cities, and the need for water to maintain ecosystem health in the floodplains have led to the need of managing water resources in an integrated fashion. Several dams have been constructed in the basin, which store water during wet periods which is released during dry periods as environmental flows. Assessment of water resources and understanding of the effectiveness of environmental flows requires knowledge of 1) long term trends in occurrence and extent of surface water, 2) what is the vegetation response to flooding and 3) whether water reached target vegetation communities. However, such information does not exist at the basin level. Satellite remote sensing is the only viable way for synoptically mapping and monitoring the extent and dynamic of flooding and vegetation response to flooding. Moreover, recent La Nina -induced, extreme flooding broke a decade long of drought and made 2010 the wettest calendar year on record in the MDB and across vast areas of Australia. This represents a unique opportunity to develop predictive models relating flow regime to vegetation response and identify trends over long term and across a large space in a drying yet variable climate. Using an internally consistent method, Landsat TM and ETM+ data were used to synoptically map the extent and dynamic of surface water bodies and track the response of vegetation communities to flooding in space and time at selected sites. Per pixel trajectory of surface water and vegetation index time series were used. Results show high interannual variability in number and size of flooded areas and a positive relationship with rainfall. Response of vegetation communities to flooding varied in space and time and with vegetation types and densities. Knowledge of the spatial and temporal dynamic of flooding and the response of vegetation communities to flooding is important for management of floodplain wetlands and vegetation communities and for investigating effectiveness of environmental flows and flow regimes in the MDB. The approach presented here can be transferred to other river systems around the world where high demand for water requires informed management decisions.

Floods of June 4 and 12, 1976, at Culbertson, Montana

USGS Publications Warehouse

Johnson, M.V.

1978-01-01

Runoff from rainfall caused flooding in the town of Culbertson, Montana, on June 4 and 12, 1976. Flood damage was mostly to business and residential structures within Culberston. Two small drainage contributed the peak flows, which at one site exceeded 1,200 cubic feet per second per square mile of contributing area. Flow from the Missouri River tributary No 5 at Culbertson consisted of flow through a pipe-arch at the State Highway 16 crossing and flow that overtopped the right bank of the main channel. Maximum combined pipe-arch and bypass flow for the June 12 flood was 1,30030 cubic feet per second. Flow from Diamond Creek consisted of flow through a culvert at the U.S. Highway 2 crossing west of Culbertson and flow that overtopped a road. Maximum combined culvert and bypass flow for the June 4 flood was 1,320 cubic feet per second. Failure of small dam increased the flow volume of the flood.

Analysis of long-term groundwater storage trends in the Wairau aquifer, New Zealand

NASA Astrophysics Data System (ADS)

Wöhling, Thomas; Gosses, Moritz; Davidson, Peter; Wilson, Scott

2016-04-01

The Wairau Aquifer covers a small proportion of the Wairau catchment in the Marlborough District of New Zealand just prior to the river discharging into the sea. The aquifer is almost exclusively recharged by surface water from the Wairau River and serves as the major drinking water resource for Blenheim and the surrounding settlements on the Wairau Plain. Because a small but constantly declining trend in aquifer levels and spring flows have been observed over the past decades, it has been made a high priority by the Marlborough District Council to better understand the limits and the mechanics of the recharge mechanism. While previous research efforts have been centred at water budgets during low-flow conditions and steady-state modelling, this study aims at understanding the dynamics of river-groundwater exchange fluxes using information of Wairau river flows at three new gauging stations, time series of groundwater observations, spring flows and qualitative (soft-)knowledge. Both qualitative and quantitative observations were integrated into a transient numerical MODFLOW model and simulations were conducted with the calibrated model for a 20-year time period. The gravels of the Wairau aquifer are highly conductive with estimated lateral conductivity values exceeding 1km per day. Although there is also evidence for anisotropy of the aquifer materials, it was found that river recharge at the upper slopes of the Wairau aquifer was consistently happening under perched conditions. In addition, exchange fluxes seem to have a functional relationship with river discharge only under low flow conditions while the exchange fluxes appear to be capped at about 16-20 m³/s for medium and large river flows. Therefore, the Wairau aquifer storage seems to be vulnerable more to the occurrence and duration of extreme low flow periods. To analyse this further, we have analysed the frequency and re-occurrence of low flow periods from the Wairau river record and found that the days of flow below a critical threshold in a given year have increased in recent years. To link the river flow record to large-scale climatic drivers, we analysed the precipitation record from several rainfall stations in the Wairau catchment as well as daily time series of precipitation data from the National Institute of Water and Atmospheric Research (NIWA) virtual climate station (VCS) network. The areal annual precipitation totals calculated from the VCS station data show a clear decline of precipitation since 1960. Shorter precipitation records from weather stations in the hilly ranges of the Wairau catchment seem to confirm the trend, while data from stations in the valleys or the Wairau Plains doesn't support the trend. The decline in areal precipitation and the corresponding increase in low flow periods of the Wairau river flows have a strong correspondence to the long-term trend in Wairau aquifer water levels, but other factors such as changes in the river bed morphology could also contribute. The reason for the decline of precipitation in the Wairau catchment is not yet known.

Impact of climate change on low flow characteristics in a small catchment of central Poland

NASA Astrophysics Data System (ADS)

Banasik, K.; Kaznowska, E.

2016-12-01

The Zagozdzonka catchment (left tributary of Vistula River) is a small lowland agricultural catchment, located in central Poland, about 100 km south of Warsaw. Hydrological investigations of the Zagozdzonka River at Plachty (N51°26'43.8''; E21°27'35.6''), have been carried out by the Department of River Engineering of Warsaw University of Life Science (WULS) since 1962. The catchment area is 82.4 km2 at the Plachty river gauging station. Annual data of temperature, annual and seasonal rainfall and runoff characteristics, as well as annual N-day (1-, 2-, 3-, 7-, 14- and 30-day) low flow from the catchment of the period of 53-year (1963-2015) were analysed. Mann-Kendall test was used for trend analysis. Analysis has revealed a long term decrease in annual discharge and in all of the analysed N-day low flows from the catchment, as well as a corresponding increase in annul temperature (1.61ºC/50 years) for this area of Poland. No trend was detected for annual precipitation nor summer/winter half year precipitation. There was little land use change in the catchment but remarkable increase of crop yields from the arable land in this region of Poland in the last 50 years, due to fertilisation. So the long term decrease of annual discharge and N-day low flows is assumed to be effect of higher evapotranspiration. The decrease of water resources in summer periods may cause problems when more intensive agriculture practice is planned (and water for irrigation is needed).

Impacts of rainfall spatial variability on hydrogeological response

NASA Astrophysics Data System (ADS)

Sapriza-Azuri, Gonzalo; Jódar, Jorge; Navarro, Vicente; Slooten, Luit Jan; Carrera, Jesús; Gupta, Hoshin V.

2015-02-01

There is currently no general consensus on how the spatial variability of rainfall impacts and propagates through complex hydrogeological systems. Most studies to date have focused on the effects of rainfall spatial variability (RSV) on river discharge, while paying little attention to other important aspects of system response. Here, we study the impacts of RSV on several responses of a hydrological model of an overexploited system. To this end, we drive a spatially distributed hydrogeological model for the semiarid Upper Guadiana basin in central Spain with stochastic daily rainfall fields defined at three different spatial resolutions (fine → 2.5 km × 2.5 km, medium → 50 km × 50 km, large → lumped). This enables us to investigate how (i) RSV at different spatial resolutions, and (ii) rainfall uncertainty, are propagated through the hydrogeological model of the system. Our results demonstrate that RSV has a significant impact on the modeled response of the system, by specifically affecting groundwater recharge and runoff generation, and thereby propagating through to various other related hydrological responses (river discharge, river-aquifer exchange, groundwater levels). These results call into question the validity of management decisions made using hydrological models calibrated or forced with spatially lumped rainfall.

ModABa Model: Annual Flow Duration Curves Assessment in Ephemeral Basins

NASA Astrophysics Data System (ADS)

Pumo, Dario; Viola, Francesco; Noto, Leonardo V.

2013-04-01

A representation of the streamflow regime for a river basin is required for a variety of hydrological analyses and engineering applications, from the water resource allocation and utilization to the environmental flow management. The flow duration curve (FDC) represents a comprehensive signature of temporal runoff variability often used to synthesize catchment rainfall-runoff responses. Several models aimed to the theoretical reconstruction of the FDC have been recently developed under different approaches, and a relevant scientific knowledge specific to this topic has been already acquired. In this work, a new model for the probabilistic characterization of the daily streamflows in perennial and ephemeral catchments is introduced. The ModABa model (MODel for Annual flow duration curves assessment in intermittent BAsins) can be thought as a wide mosaic whose tesserae are frameworks, models or conceptual schemes separately developed in different recent studies. Such tesserae are harmoniously placed and interconnected, concurring together towards a unique final aim that is the reproduction of the FDC of daily streamflows in a river basin. Two separated periods within the year are firstly identified: a non-zero period, typically characterized by significant streamflows, and a dry period, that, in the cases of ephemeral basins, is the period typically characterized by absence of streamflow. The proportion of time the river is dry, providing an estimation of the probability of zero flow occurring, is empirically estimated. Then, an analysis concerning the non-zero period is performed, considering the streamflow disaggregated into a slow subsuperficial component and a fast superficial component. A recent analytical model is adopted to derive the non zero FDC relative to the subsuperficial component; this last is considered to be generated by the soil water excess over the field capacity in the permeable portion of the basin. The non zero FDC relative to the fast streamflow component is directly derived from the precipitation duration curve through a simple filter model. The fast component of streamflow is considered to be formed by two contributions that are the entire amount of rainfall falling onto the impervious portion of the basin and the excess of rainfall over a fixed threshold, defining heavy rain events, falling onto the permeable portion. The two obtained FDCs are then overlapped, providing a unique non-zero FDC relative to the total streamflow. Finally, once the probability that the river is dry and the non zero FDC are known, the annual FDC of the daily total streamflow is derived applying the theory of total probability. The model is calibrated on a small catchment with ephemeral streamflows using a long period of daily precipitation, temperature and streamflow measurements, and it is successively validated in the same basin using two different time periods. The high model performances obtained in both the validation periods, demonstrate how the model, once calibrated, is able to accurately reproduce the empirical FDC starting from easily derivable parameters arising from a basic ecohydrological knowledge of the basin and commonly available climatic data such as daily precipitation and temperatures. In this sense, the model reveals itself as a valid tool for streamflow predictions in ungauged basins.

Predictability of Western Himalayan river flow: melt seasonal inflow into Bhakra Reservoir in northern India

NASA Astrophysics Data System (ADS)

Pal, I.; Lall, U.; Robertson, A. W.; Cane, M. A.; Bansal, R.

2013-06-01

Snowmelt-dominated streamflow of the Western Himalayan rivers is an important water resource during the dry pre-monsoon spring months to meet the irrigation and hydropower needs in northern India. Here we study the seasonal prediction of melt-dominated total inflow into the Bhakra Dam in northern India based on statistical relationships with meteorological variables during the preceding winter. Total inflow into the Bhakra Dam includes the Satluj River flow together with a flow diversion from its tributary, the Beas River. Both are tributaries of the Indus River that originate from the Western Himalayas, which is an under-studied region. Average measured winter snow volume at the upper-elevation stations and corresponding lower-elevation rainfall and temperature of the Satluj River basin were considered as empirical predictors. Akaike information criteria (AIC) and Bayesian information criteria (BIC) were used to select the best subset of inputs from all the possible combinations of predictors for a multiple linear regression framework. To test for potential issues arising due to multicollinearity of the predictor variables, cross-validated prediction skills of the best subset were also compared with the prediction skills of principal component regression (PCR) and partial least squares regression (PLSR) techniques, which yielded broadly similar results. As a whole, the forecasts of the melt season at the end of winter and as the melt season commences were shown to have potential skill for guiding the development of stochastic optimization models to manage the trade-off between irrigation and hydropower releases versus flood control during the annual fill cycle of the Bhakra Reservoir, a major energy and irrigation source in the region.

Potential climate change impacts on a tropical estuary: Hilo Bay, Hawaii

NASA Astrophysics Data System (ADS)

Adolf, J.; LaPinta, J.; Marusek, J.; Pascoe, K.; Pugh, A.

2016-02-01

Hilo Bay is a tropical estuarine ecosystem on the northeast (windward) coast of Hawai`i Island that is potentially vulnerable to climate change effects mediated through elevated water temperatures and/or changing rainfall patterns that impact river and groundwater fluxes. Here, we document trends in water temperature, river flow and phytoplankton dynamics in Hilo Bay. Hilo Bay is fed by two major rivers, Wailuku and Honoli`i, both of which have shown long term declines in output over their 85 and 38 year monitoring periods (USGS), respectively. Time series of groundwater inputs to Hilo Bay do not exist, but the average estimated rate rivals that of average river inputs. Daily average Hilo Bay water temperatures have increased at a rate of 0.35 degrees C per year (p < 0.001) since measurement by the Hilo Bay water quality buoy began in 2010, with the warmest temperatures on record recorded Sept 2015. Salinity did not show a trend over this same time period. Phytoplankton showed a pronounced seasonal cycle in Hilo Bay with a long term average of 3.7 mg m-3 and dominance by diatoms that exploit the co-availability of silica and nitrate in this environment. On shorter time scales of days to < 1 week, flood events dramatically reduce Hilo Bay salinity, temperature and phytoplankton biomass. Coincidental atmospheric warming, SST warming in the adjacent North Pacific ocean, and declining river flows will likely work together to result in elevated SST in Hilo Bay if observed trends continue. The El Nino event that started this year is expected to exacerbate this warming through reduce river flow and warmer regional SST.

Expected irrigation reductions using multiple-inlet rice irrigation under rainfall conditions in the lower Mississippi River Valley.

USDA-ARS?s Scientific Manuscript database

A model was developed to compare irrigation applications made using single-inlet and multiple-inlet rice flood distribution practices commonly used in the Lower Mississippi River Valley. The model was used to determine potential irrigation reductions under a wide range of natural rainfall amounts an...

Correlation analysis of Standardized Precipitation Index (SPI) for the water debit and level of the Cisadane River during El Niño and La Niña years

NASA Astrophysics Data System (ADS)

Khoir, A. N.; Rohmah, M.; Nuryadi

2018-03-01

Hydrometeorological factor causes most disaster in Indonesia, and two of them are drought and flood. This study aims to correlate Standardized Precipitation Index (SPI) 3-monthly to water debit and water level in the Cisadane River. The monthly rainfall data from Serpong and Pasar Baru rain station from 2009 to 2011 when moderate El Niño and moderate La Niña happened. The correlation analysis between debit and water level to SPI 3-monthly used rain post of Serpong to represent the condition of the upstream area and rain post of Pasar Baru to represent the condition of the downstream area. The results showed that during La Niña year, the rainfall on the upstream area of the Cisadane River influenced the increase and the decrease in water debit and water level. Meanwhile, the rainfall on the downstream area of the river has an opposite effect on the increase and the decrease of debit and water level of the Pasar Baru. On the upstream area, the correlation between rainfall and water debit is 0.8, and the correlation between rainfall and water level is also 0.8. During El Niño year, the correlation was less than 0.5.

Improving River Flow Predictions from the NOAA NCRFC Forecasting Model by Incorporating Satellite Observations

NASA Astrophysics Data System (ADS)

Tuttle, S. E.; Jacobs, J. M.; Restrepo, P. J.; Deweese, M. M.; Connelly, B.; Buan, S.

2016-12-01

The NOAA National Weather Service North Central River Forecast Center (NCRFC) is responsible for issuing river flow forecasts for parts of the Upper Mississippi, Great Lakes, and Hudson Bay drainages, including the Red River of the North basin (RRB). The NCRFC uses an operational hydrologic modeling infrastructure called the Community Hydrologic Prediction System (CHPS) for its operational forecasts, which currently links the SNOW-17 snow accumulation and ablation model, to the Sacramento-Soil Moisture Accounting (SAC-SMA) rainfall-runoff model, to a number of hydrologic and hydraulic flow routing models. The operational model is lumped and requires only area-averaged precipitation and air temperature as inputs. NCRFC forecasters use observational data of hydrological state variables as a source of supplemental information during forecasting, and can use professional judgment to modify the model states in real time. In a few recent years (e.g. 2009, 2013), the RRB exhibited unexpected anomalous hydrologic behavior, resulting in overestimation of peak flood discharge by up to 70% and highlighting the need for observations with high temporal and spatial coverage. Unfortunately, observations of hydrological states (e.g. soil moisture, snow water equivalent (SWE)) are relatively scarce in the RRB. Satellite remote sensing can fill this need. We use Minnesota's Buffalo River watershed within the RRB as a test case and update the operational CHPS model using modifications based on satellite observations, including AMSR-E SWE and SMOS soil moisture estimates. We evaluate the added forecasting skill of the satellite-enhanced model compared to measured streamflow using hindcasts from 2010-2013.

Impact of the Syrian refugee crisis on land use and transboundary freshwater resources.

PubMed

Müller, Marc François; Yoon, Jim; Gorelick, Steven M; Avisse, Nicolas; Tilmant, Amaury

2016-12-27

Since 2013, hundreds of thousands of refugees have migrated southward to Jordan to escape the Syrian civil war that began in mid-2011. Evaluating impacts of conflict and migration on land use and transboundary water resources in an active war zone remains a challenge. However, spatial and statistical analyses of satellite imagery for the recent period of Syrian refugee mass migration provide evidence of rapid changes in land use, water use, and water management in the Yarmouk-Jordan river watershed shared by Syria, Jordan, and Israel. Conflict and consequent migration caused ∼50% decreases in both irrigated agriculture in Syria and retention of winter rainfall in Syrian dams, which gave rise to unexpected additional stream flow to downstream Jordan during the refugee migration period. Comparing premigration and postmigration periods, Syrian abandonment of irrigated agriculture accounts for half of the stream flow increase, with the other half attributable to recovery from a severe drought. Despite this increase, the Yarmouk River flow into Jordan is still substantially below the volume that was expected by Jordan under the 1953, 1987, and 2001 bilateral agreements with Syria.

Impact of the Syrian refugee crisis on land use and transboundary freshwater resources

PubMed Central

Müller, Marc François; Yoon, Jim; Gorelick, Steven M.; Avisse, Nicolas; Tilmant, Amaury

2016-01-01

Since 2013, hundreds of thousands of refugees have migrated southward to Jordan to escape the Syrian civil war that began in mid-2011. Evaluating impacts of conflict and migration on land use and transboundary water resources in an active war zone remains a challenge. However, spatial and statistical analyses of satellite imagery for the recent period of Syrian refugee mass migration provide evidence of rapid changes in land use, water use, and water management in the Yarmouk–Jordan river watershed shared by Syria, Jordan, and Israel. Conflict and consequent migration caused ∼50% decreases in both irrigated agriculture in Syria and retention of winter rainfall in Syrian dams, which gave rise to unexpected additional stream flow to downstream Jordan during the refugee migration period. Comparing premigration and postmigration periods, Syrian abandonment of irrigated agriculture accounts for half of the stream flow increase, with the other half attributable to recovery from a severe drought. Despite this increase, the Yarmouk River flow into Jordan is still substantially below the volume that was expected by Jordan under the 1953, 1987, and 2001 bilateral agreements with Syria. PMID:27930317

Modeling the Evolution of Riparian Woodlands Facing Climate Change in Three European Rivers with Contrasting Flow Regimes

PubMed Central

Rivaes, Rui P.; Rodríguez-González, Patricia M.; Ferreira, Maria Teresa; Pinheiro, António N.; Politti, Emilio; Egger, Gregory; García-Arias, Alicia; Francés, Felix

2014-01-01

Global circulation models forecasts indicate a future temperature and rainfall pattern modification worldwide. Such phenomena will become particularly evident in Europe where climate modifications could be more severe than the average change at the global level. As such, river flow regimes are expected to change, with resultant impacts on aquatic and riparian ecosystems. Riparian woodlands are among the most endangered ecosystems on earth and provide vital services to interconnected ecosystems and human societies. However, they have not been the object of many studies designed to spatially and temporally quantify how these ecosystems will react to climate change-induced flow regimes. Our goal was to assess the effects of climate-changed flow regimes on the existing riparian vegetation of three different European flow regimes. Cases studies were selected in the light of the most common watershed alimentation modes occurring across European regions, with the objective of appraising expected alterations in the riparian elements of fluvial systems due to climate change. Riparian vegetation modeling was performed using the CASiMiR-vegetation model, which bases its computation on the fluvial disturbance of the riparian patch mosaic. Modeling results show that riparian woodlands may undergo not only at least moderate changes for all flow regimes, but also some dramatic adjustments in specific areas of particular vegetation development stages. There are circumstances in which complete annihilation is feasible. Pluvial flow regimes, like the ones in southern European rivers, are those likely to experience more pronounced changes. Furthermore, regardless of the flow regime, younger and more water-dependent individuals are expected to be the most affected by climate change. PMID:25330151

Modelling Hydrologic Processes in the Mekong River Basin Using a Distributed Model Driven by Satellite Precipitation and Rain Gauge Observations

PubMed Central

Wang, Wei; Lu, Hui; Yang, Dawen; Sothea, Khem; Jiao, Yang; Gao, Bin; Peng, Xueting; Pang, Zhiguo

2016-01-01

The Mekong River is the most important river in Southeast Asia. It has increasingly suffered from water-related problems due to economic development, population growth and climate change in the surrounding areas. In this study, we built a distributed Geomorphology-Based Hydrological Model (GBHM) of the Mekong River using remote sensing data and other publicly available data. Two numerical experiments were conducted using different rainfall data sets as model inputs. The data sets included rain gauge data from the Mekong River Commission (MRC) and remote sensing rainfall data from the Tropic Rainfall Measurement Mission (TRMM 3B42V7). Model calibration and validation were conducted for the two rainfall data sets. Compared to the observed discharge, both the gauge simulation and TRMM simulation performed well during the calibration period (1998–2001). However, the performance of the gauge simulation was worse than that of the TRMM simulation during the validation period (2002–2012). The TRMM simulation is more stable and reliable at different scales. Moreover, the calibration period was changed to 2, 4, and 8 years to test the impact of the calibration period length on the two simulations. The results suggest that longer calibration periods improved the GBHM performance during validation periods. In addition, the TRMM simulation is more stable and less sensitive to the calibration period length than is the gauge simulation. Further analysis reveals that the uneven distribution of rain gauges makes the input rainfall data less representative and more heterogeneous, worsening the simulation performance. Our results indicate that remotely sensed rainfall data may be more suitable for driving distributed hydrologic models, especially in basins with poor data quality or limited gauge availability. PMID:27010692

Modelling Hydrologic Processes in the Mekong River Basin Using a Distributed Model Driven by Satellite Precipitation and Rain Gauge Observations.

PubMed

Wang, Wei; Lu, Hui; Yang, Dawen; Sothea, Khem; Jiao, Yang; Gao, Bin; Peng, Xueting; Pang, Zhiguo

2016-01-01

The Mekong River is the most important river in Southeast Asia. It has increasingly suffered from water-related problems due to economic development, population growth and climate change in the surrounding areas. In this study, we built a distributed Geomorphology-Based Hydrological Model (GBHM) of the Mekong River using remote sensing data and other publicly available data. Two numerical experiments were conducted using different rainfall data sets as model inputs. The data sets included rain gauge data from the Mekong River Commission (MRC) and remote sensing rainfall data from the Tropic Rainfall Measurement Mission (TRMM 3B42V7). Model calibration and validation were conducted for the two rainfall data sets. Compared to the observed discharge, both the gauge simulation and TRMM simulation performed well during the calibration period (1998-2001). However, the performance of the gauge simulation was worse than that of the TRMM simulation during the validation period (2002-2012). The TRMM simulation is more stable and reliable at different scales. Moreover, the calibration period was changed to 2, 4, and 8 years to test the impact of the calibration period length on the two simulations. The results suggest that longer calibration periods improved the GBHM performance during validation periods. In addition, the TRMM simulation is more stable and less sensitive to the calibration period length than is the gauge simulation. Further analysis reveals that the uneven distribution of rain gauges makes the input rainfall data less representative and more heterogeneous, worsening the simulation performance. Our results indicate that remotely sensed rainfall data may be more suitable for driving distributed hydrologic models, especially in basins with poor data quality or limited gauge availability.

Projecting impacts of climate change on water availability using artificial neural network techniques

USGS Publications Warehouse

Swain, Eric D.; Gomez-Fragoso, Julieta; Torres-Gonzalez, Sigfredo

2017-01-01

Lago Loíza reservoir in east-central Puerto Rico is one of the primary sources of public water supply for the San Juan metropolitan area. To evaluate and predict the Lago Loíza water budget, an artificial neural network (ANN) technique is trained to predict river inflows. A method is developed to combine ANN-predicted daily flows with ANN-predicted 30-day cumulative flows to improve flow estimates. The ANN application trains well for representing 2007–2012 and the drier 1994–1997 periods. Rainfall data downscaled from global circulation model (GCM) simulations are used to predict 2050–2055 conditions. Evapotranspiration is estimated with the Hargreaves equation using minimum and maximum air temperatures from the downscaled GCM data. These simulated 2050–2055 river flows are input to a water budget formulation for the Lago Loíza reservoir for comparison with 2007–2012. The ANN scenarios require far less computational effort than a numerical model application, yet produce results with sufficient accuracy to evaluate and compare hydrologic scenarios. This hydrologic tool will be useful for future evaluations of the Lago Loíza reservoir and water supply to the San Juan metropolitan area.

Climatic and hydrologic aspects of the 2008 Midwest floods

NASA Astrophysics Data System (ADS)

Budikova, D.; Coleman, J.; Strope, S. A.

2010-12-01

Between May and June 2008 the Midwest region of the United States (U.S.) experienced record flooding. The event was produced by distinct hydroclimatic conditions that included saturated antecedent soil moisture conditions and atmospheric circulation that guided moist air from the Gulf of Mexico into the area between late May and mid-June. The latter included a well-developed trough over the central/west U.S., a strong Great Plains Low Level Jet (GPLLJ), and unseasonably strong westerlies that promoted upper level divergence in regions of positive vorticity advection. The flooding coincided with a strongly negative phase of the North Atlantic Oscillation linked to the strength of the GPLLJ. The atmospheric flow contributed to flooding within three river basins across nine states. Iowa, southern Wisconsin, and central Indiana located within the Upper Mississippi River Basin (UMRB) and the Wabash River Basin were most impacted and also recorded the greatest anomalies in rainfall. Record rainfall, persistent multi-day precipitation events, high frequency of localized high-intensity rainfall events all contributed to the severity of the flooding. Conditions peaked between May 21 and June 13 when rain fell somewhere within the region each day. River discharge rates reached record levels in June at many locations; return periods throughout Iowa, southern Wisconsin and in central Indiana were estimated to exceed 100 years, and often times 200 years. Record river stage levels were observed during this time in similar areas. Conditions began to recover into July and August. The timing of occurrence of the precipitation and hydrological anomalies towards late spring and into early summer in the Midwest was rather unusual. The 2008 flood event occurred 15 years after the infamous 1993 event. The importance of its occurrence is underscored by the observed increasing trends in extreme and flood-related precipitation characteristics during the 20th century and the anticipated changes under future anthropogenic warming scenarios. If changes in such extremes can be understood or even anticipated, society can begin to take measures towards proactive adaptation and risk management to limit future impacts.

A century of changing flows: Forest management changed flow magnitudes and warming advanced the timing of flow in a southwestern US river

PubMed Central

2017-01-01

The continued provision of water from rivers in the southwestern United States to downstream cities, natural communities and species is at risk due to higher temperatures and drought conditions in recent decades. Snowpack and snowfall levels have declined, snowmelt and peak spring flows are arriving earlier, and summer flows have declined. Concurrent to climate change and variation, a century of fire suppression has resulted in dramatic changes to forest conditions, and yet, few studies have focused on determining the degree to which changing forests have altered flows. In this study, we evaluated changes in flow, climate, and forest conditions in the Salt River in central Arizona from 1914–2012 to compare and evaluate the effects of changing forest conditions and temperatures on flows. After using linear regression models to remove the influence of precipitation and temperature, we estimated that annual flows declined by 8–29% from 1914–1963, coincident with a 2-fold increase in basal area, a 2-3-fold increase in canopy cover, and at least a 10-fold increase in forest density within ponderosa pine forests. Streamflow volumes declined by 37–56% in summer and fall months during this period. Declines in climate-adjusted flows reversed at mid-century when spring and annual flows increased by 10–31% from 1964–2012, perhaps due to more winter rainfall. Additionally, peak spring flows occurred about 12 days earlier in this period than in the previous period, coincident with winter and spring temperatures that increased by 1–2°C. While uncertainties remain, this study adds to the knowledge gained in other regions that forest change has had effects on flow that were on par with climate variability and, in the case of mid-century declines, well before the influence of anthropogenic warming. Current large-scale forest restoration projects hold some promise of recovering seasonal flows. PMID:29176868

Long-Term Ground-Water Levels and Transmissivity in the Blackstone River Basin, Northern Rhode Island

USGS Publications Warehouse

Eggleston, Jack R.; Church, Peter E.; Barbaro, Jeffrey R.

2007-01-01

Ground water provides about 7.7 million gallons per day, or 28 percent of total water use in the Rhode Island part of the Blackstone River Basin. Primary aquifers in the basin are stratified glacial deposits, composed mostly of sand and gravel along valley bottoms. The ground-water and surface-water system in the Blackstone River Basin is under stress due to population growth, out-of-basin water transfers, industrialization, and changing land-use patterns. Streamflow periodically drops below the Aquatic Base Flow standard, and ground-water withdrawals add to stress on aquatic habitat during low-flow periods. Existing hydrogeologic data were reviewed to examine historical water-level trends and to generate contour maps of water-table altitudes and transmissivity of the sand and gravel aquifer in the Blackstone River Basin in Rhode Island. On the basis of data from four long-term observation wells, water levels appear to have risen slightly in the study area during the past 55 years. Analysis of available data indicates that increased rainfall during the same period is a likely contributor to the water-level rise. Spatial patterns of transmissivity are shown over larger areas and have been refined on the basis of more detailed data coverage as compared to previous mapping studies.

Role of hydrological events in sediment and sediment-associated heavy metals transport within a continental transboundary river system - Tuul River case study (Mongolia)

NASA Astrophysics Data System (ADS)

Pietroń, Jan; Jarsjö, Jerker

2013-04-01

The concentration of heavy metals in rivers is often greater in the sediment load than in the water solution. Overall, heavy metal conveyance with sediment transport is a significant contributor to the global transport of heavy metals. Heavy metals once released to a river system may remain in the deposits of the river from short to very long times, for instance depending on to which extent erosion and deposition can influence the sediment mass stored in the river bed. In general, the mobility of contaminated sediments to downstream water recipients may to large extent be governed by natural sediment transport dynamics during hydrological events, such as flow peaks following heavy rainfalls. The Tuul River (Northern Mongolia) belongs to a Tuul River-Orkhon River-Selenga River- transboundary river system that discharges into Lake Baikal. The river system is largely characterized by its natural hydrological regime with numerous rapid peak flow events of the spring-summer periods. However, recent studies indicate contamination of fine sediment with heavy metals coming from placer gold mining area (Zaamar Goldfield) located along the downstream Tuul River. In this work, the general idea is to create a one-dimensional sediment transport model of the downstream Tuul River, and use field-data supported modeling to investigate natural erosion-deposition rates and the role of peak flows in natural sediment transport at 14 km reach just downstream the gold mining area. The model results show that the sediment load of the finest investigated grain size has a great potential to be eroded from the bed of the studied reach, especially during the main peak flow events. However, the same events are associated with a significant deposition of the finest material. The model results also show different hysteresis behavior of the sediment load rating curves (clockwise and counter-clockwise) during the main peak flow events. These are interpreted as effects of changing in-channel sediment supplies due to sorting method applied in the model. More generally, the modelling may increase our knowledge about the sediment transport patterns of the reach downstream the mining area. This part of the river may be considered as a temporal sink of heavy metals which may accumulate and store sediments. The deposition in such sinks can considerably support attenuation of contaminated sediment loads. On the other hand, sediments that are accumulated in sinks can increase the concentration of contaminated sediment loads during peak flow events. Information about the rates of eroded and accumulated contaminated material in such sinks is important for future water protection planning, especially under changing climate conditions. This work may also provide scientific input to discussions on both adverse environmental consequences of placer mining, and suitable designs of sediment control measures in the Zaamar Goldfield and other continental river systems.

Climate impacts on connectivity of snowmelt to flow in the ...

EPA Pesticide Factsheets

Much of the water that people in Western Oregon rely on comes from snowpack in the Cascade Range, and this snowpack is expected to decrease in coming years with climate change. In fact, the past 6 years have shown dramatic variation in snowpack, from a high of 174% of normal in 2010-11 to a low of 11% for 2014-15, one of the lowest on record. During this timeframe, we have monitored the stable isotopes of water within the Willamette River twice monthly, and mapped the spatial variation of water isotopes across the basin. Within the Willamette Basin, stable isotopes of water in precipitation vary strongly with elevation and provide a marker for determining the mean elevation from which water in the Willamette River is derived. In winter, when snow accumulates in the mountains, low elevation precipitation (primarily rain) contributes the largest proportion of water to the Willamette River. During summer, when rainfall is scarce and demand for water is the greatest, water in the Willamette River is mainly derived from high elevation snowmelt. Our data indicate that the proportion of water from high elevation decreased with decreasing snowpack. We combine this information with river flow data to estimate the volume reduction related to snowpack reduction during the dry summer. Observed reductions in the contribution of high elevation water to the Willamette River after just 2 years of diminished snowpack indicate that the hydrologic system responds relatively

Hot Spots and Hot Moments of Nitrogen in a Riparian Corridor

NASA Astrophysics Data System (ADS)

Dwivedi, Dipankar; Arora, Bhavna; Steefel, Carl I.; Dafflon, Baptiste; Versteeg, Roelof

2018-01-01

We use 3-D high-resolution reactive transport modeling to investigate whether the spatial distribution of organic-carbon-rich and chemically reduced sediments located in the riparian zone and temporal variability in groundwater flow direction impact the formation and distribution of nitrogen hot spots (regions that exhibit higher reaction rates when compared to other locations nearby) and hot moments (times that exhibit high reaction rates as compared to longer intervening time periods) within the Rifle floodplain in Colorado. Groundwater flows primarily toward the Colorado River from the floodplain but changes direction at times of high river stage. The result is that oxic river water infiltrates the Rifle floodplain during these relatively short-term events. Simulation results indicate that episodic rainfall in the summer season leads to the formation of nitrogen hot moments associated with Colorado River rise and resulting river infiltration into the floodplain. The results further demonstrate that the naturally reduced zones (NRZs) present in sediments of the Rifle floodplain have a higher potential for nitrate removal, approximately 70% greater than non-NRZs for typical hydrological conditions. During river water infiltration, nitrate reduction capacity remains the same within the NRZs, however, these conditions impact non-NRZs to a greater extent (approximately 95% less nitrate removal). Model simulations indicate chemolithoautotrophs are primarily responsible for the removal of nitrate in the Rifle floodplain. These nitrogen hot spots and hot moments are sustained by microbial respiration and the chemolithoautotrophic oxidation of reduced minerals in the riparian zone.

TREHS: An open-access software tool for investigating and evaluating temporary river regimes as a first step for their ecological status assessment.

PubMed

Gallart, Francesc; Cid, Núria; Latron, Jérôme; Llorens, Pilar; Bonada, Núria; Jeuffroy, Justin; Jiménez-Argudo, Sara-María; Vega, Rosa-María; Solà, Carolina; Soria, Maria; Bardina, Mònica; Hernández-Casahuga, Antoni-Josep; Fidalgo, Aránzazu; Estrela, Teodoro; Munné, Antoni; Prat, Narcís

2017-12-31

When the regime of a river is not perennial, there are four main difficulties with the use of hydrographs for assessing hydrological alteration: i) the main hydrological features relevant for biological communities are not quantitative (discharges) but qualitative (phases such as flowing water, stagnant pools or lack of surface water), ii) stream flow records do not inform on the temporal occurrence of stagnant pools, iii) as most of the temporary streams are ungauged, their regime has to be evaluated by alternative methods such as remote sensing or citizen science, and iv) the biological quality assessment of the ecological status of a temporary stream must follow a sampling schedule and references adapted to the flow- pool-dry regime. To overcome these challenges within an operational approach, the freely available software tool TREHS has been developed within the EU LIFE TRIVERS project. This software permits the input of information from flow simulations obtained with any rainfall-runoff model (to set an unimpacted reference stream regime) and compares this with the information obtained from flow gauging records (if available) and interviews with local people, as well as instantaneous observations by individuals and interpretation of ground-level or aerial photographs. Up to six metrics defining the permanence of water flow, the presence of stagnant pools and their temporal patterns of occurrence are used to determine natural and observed river regimes and to assess the degree of hydrological alteration. A new regime classification specifically designed for temporary rivers was developed using the metrics that measure the relative permanence of the three main phases: flow, disconnected pools and dry stream bed. Finally, the software characterizes the differences between the natural and actual regimes, diagnoses the hydrological status (degree of hydrological alteration), assesses the significance and robustness of the diagnosis and recommends the best periods for biological quality samplings. Copyright © 2017 Elsevier B.V. All rights reserved.

Simulation of streamflow, evapotranspiration, and groundwater recharge in the Lower Frio River watershed, south Texas, 1961-2008

USGS Publications Warehouse

Lizarraga, Joy S.; Ockerman, Darwin J.

2011-01-01

The U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engineers, Fort Worth District; the City of Corpus Christi; the Guadalupe-Blanco River Authority; the San Antonio River Authority; and the San Antonio Water System, configured, calibrated, and tested a watershed model for a study area consisting of about 5,490 mi2 of the Frio River watershed in south Texas. The purpose of the model is to contribute to the understanding of watershed processes and hydrologic conditions in the lower Frio River watershed. The model simulates streamflow, evapotranspiration (ET), and groundwater recharge by using a numerical representation of physical characteristics of the landscape, and meteorological and streamflow data. Additional time-series inputs to the model include wastewater-treatment-plant discharges, surface-water withdrawals, and estimated groundwater inflow from Leona Springs. Model simulations of streamflow, ET, and groundwater recharge were done for various periods of record depending upon available measured data for input and comparison, starting as early as 1961. Because of the large size of the study area, the lower Frio River watershed was divided into 12 subwatersheds; separate Hydrological Simulation Program-FORTRAN models were developed for each subwatershed. Simulation of the overall study area involved running simulations in downstream order. Output from the model was summarized by subwatershed, point locations, reservoir reaches, and the Carrizo-Wilcox aquifer outcrop. Four long-term U.S. Geological Survey streamflow-gaging stations and two short-term streamflow-gaging stations were used for streamflow model calibration and testing with data from 1991-2008. Calibration was based on data from 2000-08, and testing was based on data from 1991-99. Choke Canyon Reservoir stage data from 1992-2008 and monthly evaporation estimates from 1999-2008 also were used for model calibration. Additionally, 2006-08 ET data from a U.S. Geological Survey meteorological station in Medina County were used for calibration. Streamflow and ET calibration were considered good or very good. For the 2000-08 calibration period, total simulated flow volume and the flow volume of the highest 10 percent of simulated daily flows were calibrated to within about 10 percent of measured volumes at six U.S. Geological Survey streamflow-gaging stations. The flow volume of the lowest 50 percent of daily flows was not simulated as accurately but represented a small percent of the total flow volume. The model-fit efficiency for the weekly mean streamflow during the calibration periods ranged from 0.60 to 0.91, and the root mean square error ranged from 16 to 271 percent of the mean flow rate. The simulated total flow volumes during the testing periods at the long-term gaging stations exceeded the measured total flow volumes by approximately 22 to 50 percent at three stations and were within 7 percent of the measured total flow volumes at one station. For the longer 1961-2008 simulation period at the long-term stations, simulated total flow volumes were within about 3 to 18 percent of measured total flow volumes. The calibrations made by using Choke Canyon reservoir volume for 1992-2008, reservoir evaporation for 1999-2008, and ET in Medina County for 2006-08, are considered very good. Model limitations include possible errors related to model conceptualization and parameter variability, lack of data to better quantify certain model inputs, and measurement errors. Uncertainty regarding the degree to which available rainfall data represent actual rainfall is potentially the most serious source of measurement error. A sensitivity analysis was performed for the Upper San Miguel subwatershed model to show the effect of changes to model parameters on the estimated mean recharge, ET, and surface runoff from that part of the Carrizo-Wilcox aquifer outcrop. Simulated recharge was most sensitive to the changes in the lower-zone ET (LZ

Rainfall threshold calculation for debris flow early warning in areas with scarcity of data

NASA Astrophysics Data System (ADS)

Pan, Hua-Li; Jiang, Yuan-Jun; Wang, Jun; Ou, Guo-Qiang

2018-05-01

Debris flows are natural disasters that frequently occur in mountainous areas, usually accompanied by serious loss of lives and properties. One of the most commonly used approaches to mitigate the risk associated with debris flows is the implementation of early warning systems based on well-calibrated rainfall thresholds. However, many mountainous areas have little data regarding rainfall and hazards, especially in debris-flow-forming regions. Therefore, the traditional statistical analysis method that determines the empirical relationship between rainstorms and debris flow events cannot be effectively used to calculate reliable rainfall thresholds in these areas. After the severe Wenchuan earthquake, there were plenty of deposits deposited in the gullies, which resulted in several debris flow events. The triggering rainfall threshold has decreased obviously. To get a reliable and accurate rainfall threshold and improve the accuracy of debris flow early warning, this paper developed a quantitative method, which is suitable for debris flow triggering mechanisms in meizoseismal areas, to identify rainfall threshold for debris flow early warning in areas with a scarcity of data based on the initiation mechanism of hydraulic-driven debris flow. First, we studied the characteristics of the study area, including meteorology, hydrology, topography and physical characteristics of the loose solid materials. Then, the rainfall threshold was calculated by the initiation mechanism of the hydraulic debris flow. The comparison with other models and with alternate configurations demonstrates that the proposed rainfall threshold curve is a function of the antecedent precipitation index (API) and 1 h rainfall. To test the proposed method, we selected the Guojuanyan gully, a typical debris flow valley that during the 2008-2013 period experienced several debris flow events, located in the meizoseismal areas of the Wenchuan earthquake, as a case study. The comparison with other threshold models and configurations shows that the selected approach is the most promising starting point for further studies on debris flow early warning systems in areas with a scarcity of data.

Variation of Temperature and Precipitation in Urban Agglomeration and Prevention Suggestion of Waterlogging in Middle and Lower Reaches of Yangtze River

NASA Astrophysics Data System (ADS)

Na, Liu; Youjie, Jin; Jiaqi, Dai

2018-03-01

The variation trend of temperature and precipitation during flood season in the middle and lower reaches of the Yangtze River basin in recent 50 years and change characteristics of rainfall in five typical flood prone cities are analysed. Aiming at waterlogging problems in the urban agglomeration of middle and lower reaches of the Yangtze River, the comprehensive prevention and control suggestions are put forward. The results showed that: the temperature trend in the basin decreased and then increased, and the precipitation showed a downward-rising-downward trend, no mutation occurred; The incidence of heavy rainfall events in the five typical cities with daily rainfall more than 50mm showed an upward trend, and increased significantly after 2002. The intensity of precipitation increased gradually. Climate change makes urban agglomeration waterlogging disasters become increasingly prominent in the middle and lower reaches of the Yangtze River.

Sediment Transportation Induced by Deep-Seated Landslides in a Debris Flow Basin in Taiwan

NASA Astrophysics Data System (ADS)

Lin, Meei Ling; Chen, Te Wei; Chen, Yong Sheng; Sin Jhuang, Han

2016-04-01

Typhoon Morakot brought huge amount of rainfall to the southern Taiwan in 2009 and caused severe landslides and debris flow hazard. After Typhoon Morakot, it was found that the volume of sediment transported by the debris flow and its effects on the affected area were much more significant compared to previous case history, which may due to the huge amount of rainfall causing significant deep-seated landslides in the basin. In this study, the effects and tendency of the sediment transportation in a river basin following deep-seated landslides caused by typhoon Morakot were evaluated. We used LiDAR, DEM, and aerial photo to identify characteristics of deep-seated landslides in a debris flow river basin, KSDF079 in Liuoguey District, Kaohsiung City, Taiwan. Eight deep-seated landslides were identified in the basin. To estimate the potential landslide volume associated with the deep-seated landslides, the stability analysis was conducted to locate the critical sliding surface, and the potential landside volume was estimated based on the estimation equation proposed by the International Geotechnical Societies' UNESCO Working Party on World Landslide Inventory (WP/WLI, 1990). The total potential landslide volume of the eight deep-seated landslides in KSDF079 basin was about 28,906,856 m3. Topographic analysis was performed by using DEM before and LiDAR derived DEM after typhoon Morakot to calculate the landslide volume transported. The result of erosion volume and deposition volume lead to a run out volume of 5,832,433 m3. The results appeared to consist well with the field condition and aerial photo. Comparing the potential landslide volume and run out volume of eight deep-seated landslides, it was found that the remaining potential landslide volume was about 80%. Field investigation and topographic analysis of the KSDF079 debris flow revealed that a significant amount of sediment deposition remained in the river channel ranging from the middle to the downstream section of the channel, and the channel has been widen. Such large proportion of landslide volume remained in the basin on deep-seated landslide scars and debris flow river channel would likely to cause further debris transportation in the future events. The stability analysis used in this study provided a feasible method and satisfactory results for estimating sediment volume transportation associated with the deep-seated landslides in the study area. Combination of the stability analysis results and the topographic analysis provided estimation of sediment transportation caused by the deep-seated landslides, and trend variation of further sediment transport of the basin, which could provide vital information for hazard mitigation. Keyword: deep-seated landslide, sediment transport, DEM, LiDAR, stability analysis

The changing flow regime and sediment load of the Red River, Viet Nam

NASA Astrophysics Data System (ADS)

Le, Thi Phuong Quynh; Garnier, Josette; Gilles, Billen; Sylvain, Théry; Van Minh, Chau

2007-02-01

SummarySouth-East Asian Rivers contribute very significantly to the global sediment load to the ocean, hence to global biogeochemical cycles, and are subject to rapid changes owing to recent population and economic growth. The Red River system (Viet Nam and China) offers a good example of these changes. Previous estimates (before the year 1980) of the suspended matter loading of the Red River ranged from 100 to 170 × 10 6 t yr -1, i.e. from 640 to 1060 t km -2 yr -1. The strong dependence of suspended solid transport on hydrology results in a large year-to-year variability. Based on the available hydrological data from the period 1997-2004, and on a one-year survey of daily suspended matter of the three main tributaries of the Red River system in 2003, a simplified modeling approach, distinguishing between surface runoff and base flow, is established to estimate the mean suspended loading of the Red River under present conditions. The obtained value is 40 × 10 6 t yr -1, corresponding to a specific load of 280 t km -2 yr -1. It reflects a 70% decrease of the total suspended load since the impoundment of the Hoa Binh and Thac Ba reservoirs in the 1980s. Following the planned construction of two additional reservoirs, the model predicts a further reduction by 20% of the suspended load of the Red River, which might be compensated by an expected increase in suspended loading due to enhanced rainfall induced by climate change. Using measurements of the total phosphorus content of the suspended material in the different Red River tributaries, the present phosphorus delivery by the Red River can be estimated as 36 × 10 6 kgP yr -1.

Total pollution effect of urban surface runoff.

PubMed

Luo, Hongbing; Luo, Lin; Huang, Gu; Liu, Ping; Li, Jingxian; Hu, Sheng; Wang, Fuxiang; Xu, Rui; Huang, Xiaoxue

2009-01-01

For pollution research with regard to urban surface runoff, most sampling strategies to date have focused on differences in land usage. With single land-use sampling, total surface runoff pollution effect cannot be evaluated unless every land usage spot is monitored. Through a new sampling strategy known as mixed stormwater sampling for a street community at discharge outlet adjacent to river, this study assessed the total urban surface runoff pollution effect caused by a variety of land uses and the pollutants washed off from the rain pipe system in the Futian River watershed in Shenzhen City of China. The water quality monitoring indices were COD (chemical oxygen demand), TSS (total suspend solid), TP (total phosphorus), TN (total nitrogen) and BOD (biochemical oxygen demand). The sums of total pollution loads discharged into the river for the four indices of COD, TSS, TN, and TP over all seven rainfall events were very different. The mathematical model for simulating total pollution loads was established from discharge outlet mixed stormwater sampling of total pollution loads on the basis of four parameters: rainfall intensity, total land area, impervious land area, and pervious land area. In order to treat surface runoff pollution, the values of MFF30 (mass first flush ratio) and FF30 (first 30% of runoff volume) can be considered as split-flow control criteria to obtain more effective and economical design of structural BMPs (best management practices) facilities.

Assessing the impacts of climate change and dams on floodplain inundation and wetland connectivity in the wet-dry tropics of northern Australia

NASA Astrophysics Data System (ADS)

Karim, Fazlul; Dutta, Dushmanta; Marvanek, Steve; Petheram, Cuan; Ticehurst, Catherine; Lerat, Julien; Kim, Shaun; Yang, Ang

2015-03-01

Floodplain wetlands and their hydrological connectivity with main river channels in the Australian wet-dry tropics are under increasing pressure from global climate change and water resource development, and there is a need for modelling tools to estimate the time dynamics of connectivity. This paper describes an integrated modelling framework combining conceptual rainfall-runoff modelling, river system modelling and hydrodynamic (HD) modelling to estimate hydrological connectivity between wetlands and rivers in the Flinders and Gilbert river catchments in northern Australia. Three historical flood events ranging from a mean annual flood to a 35-year return period flood were investigated using a two dimensional HD model (MIKE 21). Inflows from upstream catchments were estimated using a river network model. Local runoff within the HD modelling domain was simulated using the Sacramento rainfall-runoff model. The Shuttle Radar Topography Mission (SRTM) derived 30 m DEM was used to reproduce floodplain topography, stream networks and wetlands in the HD model. The HD model was calibrated using stream gauge data and inundation maps derived from satellite (MODIS: MODerate resolution Imaging Spectroradiometer) imagery. An algorithm was developed to combine the simulated water heights with the DEM to quantify inundation and flow connection between wetlands and rivers. The connectivity of 18 ecologically important wetlands on the Flinders floodplain and 7 on the Gilbert floodplain were quantified. The impacts of climate change and water resource development on connectivity to individual wetlands were assessed under a projected dry climate (2nd driest of 15 GCMs), wet climate (2nd wettest of 15 GCMs) and dam conditions. The results indicate that changes in rainfall under a wetter and drier future climate could have large impacts on area, duration and frequency of inundation and connectivity. Topographic relief, river bank elevation and flood magnitude were found to be the key factors contributing to the level of connectivity. Under a wetter future climate the average duration of connection of wetlands to the main river channel increased by 7% and under a drier climate it decreased by 18%. Construction of a 248 GL dam in the Flinders catchment and two (498 and 271 GL capacity) in the Gilbert catchment could reduce the average duration of connectivity by 1% and 2% in the Flinders and Gilbert catchments respectively. This information is potentially useful to future studies on the flood-dependent ecology in this region.

HYDROSCAPE: A SCAlable and ParallelizablE Rainfall Runoff Model for Hydrological Applications

NASA Astrophysics Data System (ADS)

Piccolroaz, S.; Di Lazzaro, M.; Zarlenga, A.; Majone, B.; Bellin, A.; Fiori, A.

2015-12-01

In this work we present HYDROSCAPE, an innovative streamflow routing method based on the travel time approach, and modeled through a fine-scale geomorphological description of hydrological flow paths. The model is designed aimed at being easily coupled with weather forecast or climate models providing the hydrological forcing, and at the same time preserving the geomorphological dispersion of the river network, which is kept unchanged independently on the grid size of rainfall input. This makes HYDROSCAPE particularly suitable for multi-scale applications, ranging from medium size catchments up to the continental scale, and to investigate the effects of extreme rainfall events that require an accurate description of basin response timing. Key feature of the model is its computational efficiency, which allows performing a large number of simulations for sensitivity/uncertainty analyses in a Monte Carlo framework. Further, the model is highly parsimonious, involving the calibration of only three parameters: one defining the residence time of hillslope response, one for channel velocity, and a multiplicative factor accounting for uncertainties in the identification of the potential maximum soil moisture retention in the SCS-CN method. HYDROSCAPE is designed with a simple and flexible modular structure, which makes it particularly prone to massive parallelization, customization according to the specific user needs and preferences (e.g., rainfall-runoff model), and continuous development and improvement. Finally, the possibility to specify the desired computational time step and evaluate streamflow at any location in the domain, makes HYDROSCAPE an attractive tool for many hydrological applications, and a valuable alternative to more complex and highly parametrized large scale hydrological models. Together with model development and features, we present an application to the Upper Tiber River basin (Italy), providing a practical example of model performance and characteristics.

A Prototype Visualization of Real-time River Drainage Network Response to Rainfall

NASA Astrophysics Data System (ADS)

Demir, I.; Krajewski, W. F.

2011-12-01

The Iowa Flood Information System (IFIS) is a web-based platform developed by the Iowa Flood Center (IFC) to provide access to and visualization of flood inundation maps, real-time flood conditions, flood forecasts both short-term and seasonal, and other flood-related data for communities in Iowa. The key element of the system's architecture is the notion of community. Locations of the communities, those near streams and rivers, define basin boundaries. The IFIS streams rainfall data from NEXRAD radar, and provides three interfaces including animation for rainfall intensity, daily rainfall totals and rainfall accumulations for past 14 days for Iowa. A real-time interactive visualization interface is developed using past rainfall intensity data. The interface creates community-based rainfall products on-demand using watershed boundaries of each community as a mask. Each individual rainfall pixel is tracked in the interface along the drainage network, and the ones drains to same pixel location are accumulated. The interface loads recent rainfall data in five minute intervals that are combined with current values. Latest web technologies are utilized for the development of the interface including HTML 5 Canvas, and JavaScript. The performance of the interface is optimized to run smoothly on modern web browsers. The interface controls allow users to change internal parameters of the system, and operation conditions of the animation. The interface will help communities understand the effects of rainfall on water transport in stream and river networks and make better-informed decisions regarding the threat of floods. This presentation provides an overview of a unique visualization interface and discusses future plans for real-time dynamic presentations of streamflow forecasting.

A Web-based Data Intensive Visualization of Real-time River Drainage Network Response to Rainfall

NASA Astrophysics Data System (ADS)

Demir, I.; Krajewski, W. F.

2012-04-01

The Iowa Flood Information System (IFIS) is a web-based platform developed by the Iowa Flood Center (IFC) to provide access to and visualization of flood inundation maps, real-time flood conditions, flood forecasts both short-term and seasonal, and other flood-related data for communities in Iowa. The key element of the system's architecture is the notion of community. Locations of the communities, those near streams and rivers, define basin boundaries. The IFIS streams rainfall data from NEXRAD radar, and provides three interfaces including animation for rainfall intensity, daily rainfall totals and rainfall accumulations for past 14 days for Iowa. A real-time interactive visualization interface is developed using past rainfall intensity data. The interface creates community-based rainfall products on-demand using watershed boundaries of each community as a mask. Each individual rainfall pixel is tracked in the interface along the drainage network, and the ones drains to same pixel location are accumulated. The interface loads recent rainfall data in five minute intervals that are combined with current values. Latest web technologies are utilized for the development of the interface including HTML 5 Canvas, and JavaScript. The performance of the interface is optimized to run smoothly on modern web browsers. The interface controls allow users to change internal parameters of the system, and operation conditions of the animation. The interface will help communities understand the effects of rainfall on water transport in stream and river networks and make better-informed decisions regarding the threat of floods. This presentation provides an overview of a unique visualization interface and discusses future plans for real-time dynamic presentations of streamflow forecasting.

Spatio-temporal trends of rainfall across Indian river basins

NASA Astrophysics Data System (ADS)

Bisht, Deepak Singh; Chatterjee, Chandranath; Raghuwanshi, Narendra Singh; Sridhar, Venkataramana

2018-04-01

Daily gridded high-resolution rainfall data of India Meteorological Department at 0.25° spatial resolution (1901-2015) was analyzed to detect the trend in seasonal, annual, and maximum cumulative rainfall for 1, 2, 3, and 5 days. The present study was carried out for 85 river basins of India during 1901-2015 and pre- and post-urbanization era, i.e., 1901-1970 and 1971-2015, respectively. Mann-Kendall ( α = 0.05) and Theil-Sen's tests were employed for detecting the trend and percentage of change over the period of time, respectively. Daily extreme rainfall events, above 95 and 99 percentile threshold, were also analyzed to detect any trend in their magnitude and number of occurrences. The upward trend was found for the majority of the sub-basins for 1-, 2-, 3-, and 5-day maximum cumulative rainfall during the post-urbanization era. The magnitude of extreme threshold events is also found to be increasing in the majority of the river basins during the post-urbanization era. A 30-year moving window analysis further revealed a widespread upward trend in a number of extreme threshold rainfall events possibly due to urbanization and climatic factors. Overall trends studied against intra-basin trend across Ganga basin reveal the mixed pattern of trends due to inherent spatial heterogeneity of rainfall, therefore, highlighting the importance of scale for such studies.

Application of Radar-Based Accumulated Rainfall Products for Early Detection of Heavy Rainfall Occurrence

NASA Astrophysics Data System (ADS)

Nishiyama, K.; Wakimizu, K.; Yokota, I.; Tsukahara, K.; Moriyama, T.

2016-12-01

In Japan, river and debris flow disasters have been frequently caused by heavy rainfall occurrence under the influence of the activity of a stationary front and associated inflow of a large amount of moisture into the front. However, it is very difficult to predict numerically-based heavy rainfall and associated landslide accurately. Therefore, the use of meteorological radar information is required for enhancing decision-making ability to urge the evacuation of local residents by local government staffs prior to the occurrence of the heavy rainfall disaster. It is also desirable that the local residents acquire the ability to determine the evacuation immediately after confirming radar information by themselves. Actually, it is difficult for untrained local residents and local government staffs to easily recognize where heavy rainfall occurs locally for a couple of hours. This reason is that the image of radar echoes is equivalent to instant electromagnetic distribution measured per a couple of minutes, and the distribution of the radar echoes moves together with the movement of a synoptic system. Therefore, in this study, considering that the movement of radar echoes also may stop in a specific area if stationary front system becomes dominant, radar-based accumulated rainfall information is defined here. The rainfall product is derived by the integration of radar intensity measured every ten minutes during previous 1 hours. Using this product, it was investigated whether and how the radar-based accumulated rainfall displayed at an interval of ten minutes can be applied for early detection of heavy rainfall occurrence. The results are summarized as follows. 1) Radar-based accumulated rainfall products could confirm that some of stationary heavy rainfall systems had already appeared prior to disaster occurrence, and clearly identify the movement of heavy rainfall area. 2) Moreover, accumulated area of rainfall could be visually and easily identified, compared with time-series (movie) of real-time radar-based rainfall intensity. Therefore, the accumulated rainfall distribution provides effective information for early detection of heavy rainfall causing disasters through the training of local residents and local government staffs who have no meteorologically-technical knowledge.

iss012e15035

NASA Image and Video Library

2006-01-12

ISS012-E-15035 (12 Jan. 2006) --- The confluence of the Ohio and Mississippi Rivers at Cairo, Illinois is featured in this image photographed by an Expedition 12 crew member on the International Space Station. The Ohio River becomes a tributary of the Mississippi River directly to the south of Cairo, Illinois, a small city on the spit of land where the rivers converge (at center of image). Brown sediment-laden water flowing generally northeast to south from the Ohio River is distinct from the green and relatively sediment-poor water (northwest- to south-flowing) of the Mississippi River. The coloration of the rivers in this image is reversed from the usual condition of a green Ohio and a brown Mississippi. According to scientists, this suggests that recent precipitation in the Ohio River watershed, with very high rainfall over the Appalachians and the northeastern United States in December 2005, has led to a greater sediment load in the Ohio waters. The distinct boundary between the two river’s waters indicates that little to no mixing occurs even 3-4 miles (5-6 kilometers) downstream. The city of Cairo became a prosperous port following the Civil War due to increased riverboat and railroad commerce. Small features on the Ohio are river barges and indicate the continued importance of Cairo as a transport hub. Flooding of the Ohio and Mississippi Rivers presents a continual danger to the city; this danger is lessened by the Birds Point-New Madrid Floodway that begins directly to the south of the river confluence. The floodway lowers flood stages upstream (such as at Cairo) and adjacent to the floodway during major flood events. Part of the extensive levee system associated with flood control of the Mississippi River is visible in the image. Barlow Bottoms (image right), located in adjacent Kentucky, are a wetlands bird watching location that is replenished by periodic floods and releases of Ohio River water.

Submesoscale features and their interaction with fronts and internal tides in a high-resolution coupled atmosphere-ocean-wave model of the Bay of Bengal

NASA Astrophysics Data System (ADS)

Jensen, Tommy G.; Shulman, Igor; Wijesekera, Hemantha W.; Anderson, Stephanie; Ladner, Sherwin

2018-03-01

Large freshwater fluxes into the Bay of Bengal by rainfall and river discharges result in strong salinity fronts in the bay. In this study, a high-resolution coupled atmosphere-ocean-wave model with comprehensive physics is used to model the weather, ocean circulation, and wave field in the Bay of Bengal. Our objective is to explore the submesoscale activity that occurs in a realistic coupled model that resolves mesoscales and allows part of the submesoscale field. Horizontal resolution in the atmosphere varies from 2 to 6 km and is 13 km for surface waves, while the ocean model is submesoscale permitting with resolutions as high as 1.5 km and a vertical resolution of 0.5 m in the upper 10 m. In this paper, three different cases of oceanic submesoscale features are discussed. In the first case, heavy rainfall and intense downdrafts produced by atmospheric convection are found to force submesoscale currents, temperature, and salinity anomalies in the oceanic mixed layer and impact the mesoscale flow. In a second case, strong solitary-like waves are generated by semidiurnal tides in the Andaman Sea and interact with mesoscale flows and fronts and affect submesoscale features generated along fronts. A third source of submesoscale variability is found further north in the Bay of Bengal where river outflows help maintain strong salinity gradients throughout the year. For that case, a comparison with satellite observations of sea surface height anomalies, sea surface temperature, and chlorophyll shows that the model captures the observed mesoscale eddy features of the flow field, but in addition, submesoscale upwelling and downwelling patterns associated with ageostrophic secondary circulations along density fronts are also captured by the model.

Implications of climate change for potamodromous fishes.

PubMed

Beatty, Stephen J; Morgan, David L; Lymbery, Alan J

2014-06-01

There is little understanding of how climate change will impact potamodromous freshwater fishes. Since the mid 1970s, a decline in annual rainfall in south-western Australia (a globally recognized biodiversity hotspot) has resulted in the rivers of the region undergoing severe reductions in surface flows (ca. 50%). There is universal agreement amongst Global Climate Models that rainfall will continue to decline in this region. Limited data are available on the movement patterns of the endemic freshwater fishes of south-western Australia or on the relationship between their life histories and hydrology. We used this region as a model to determine how dramatic hydrological change may impact potamodromous freshwater fishes. Migration patterns of fishes in the largest river in south-western Australia were quantified over a 4 year period and were related to a number of key environmental variables including discharge, temperature, pH, conductivity and dissolved oxygen. Most of the endemic freshwater fishes were potamodromous, displaying lateral seasonal spawning migrations from the main channel into tributaries, and there were significant temporal differences in movement patterns between species. Using a model averaging approach, amount of discharge was clearly the best predictor of upstream and downstream movement for most species. Given past and projected reductions in surface flow and groundwater, the findings have major implications for future recruitment rates and population viabilities of potamodromous fishes. Freshwater ecosystems in drying climatic regions can only be managed effectively if such hydro-ecological relationships are considered. Proactive management and addressing existing anthropogenic stressors on aquatic ecosystems associated with the development of surface and groundwater resources and land use is required to increase the resistance and resilience of potamodromous fishes to ongoing flow reductions. © 2013 John Wiley & Sons Ltd.

A semi-urban case study of small scale variability of rainfall and run-off, with C- and X-band radars and the fully distributed hydrological model Multi-Hydro

NASA Astrophysics Data System (ADS)

Alves de Souza, Bianca; da Silva Rocha Paz, Igor; Gires, Auguste; Tchiguirinskaia, Ioulia; Schertzer, Daniel

2016-04-01

The complexity of urban hydrology results both from that of urban systems and the extreme rainfall variability. The latter can display strongly localised rain cells that can be extremely damaging when hitting vulnerable parts of urban systems. This paper investigates this complexity on a semi-urban sub-catchment - located in Massy (South of Paris, France) - of the Bievre river, which is known for its frequent flashfloods. Advanced geo-processing techniques were used to find the ideal pixel size for this 6.326km2 basin. C-band and X-band radar data are multifractally downscaled at various resolutions and input to the fully distributed hydrological model Multi-Hydro. The latter has been developed at Ecole des Ponts ParisTech. It integrates validated modules dealing with surface flow, saturated and unsaturated surface flow, and sewer flow. The C-band radar is located in Trappes, approx. 21km East of the catchment, is operated by Méteo-France and has a resolution of 1km x 1km x 5min. The X-band radar operated by Ecole des Ponts Paris Tech on its campus has a resolution of 125m x 125m x 3.4min. The performed multifractal downscaling enables both the generation of large ensemble realizations and easy change of resolution (e.g. down to 10 m in the present study). This in turn allows a detailed analysis of the impacts of small scale variability and the required resolution to obtain accurate simulations, therefore predictions. This will be shown on two rainy episodes over the chosen sub-catchment of the Bievre river.

Application of Multi-Satellite Precipitation Analysis to Floods and Landslides

NASA Technical Reports Server (NTRS)

Adler, Robert; Hong, Yang; Huffman, George

2007-01-01

Satellite data acquired and processed in real time now have the potential to provide the spacetime information on rainfall needed to monitor flood and landslide events around the world. This can be achieved by integrating the satellite-derived forcing data with hydrological models and landslide algorithms. Progress in using the TRMM Multi-satellite Precipitation Analysis (TMPA) as input to flood and landslide forecasts is outlined, with a focus on understanding limitations of the rainfall data and impacts of those limitations on flood/landslide analyses. Case studies of both successes and failures will be shown, as well as comparison with ground comparison data sets both in terms of rainfall and in terms of flood/landslide events. In addition to potential uses in real-time, the nearly ten years of TMPA data allow retrospective running of the models to examine variations in extreme events. The flood determination algorithm consists of four major components: 1) multi-satellite precipitation estimation; 2) characterization of land surface including digital elevation from NASA SRTM (Shuttle Radar Terrain Mission), topography-derived hydrologic parameters such as flow direction, flow accumulation, basin, and river network etc.; 3) a hydrological model to infiltrate rainfall and route overland runoff; and 4) an implementation interface to relay the input data to the models and display the flood inundation results to potential users and decision-makers. In terms of landslides, the satellite rainfall information is combined with a global landslide susceptibility map, derived from a combination of global surface characteristics (digital elevation topography, slope, soil types, soil texture, and land cover classification etc.) using a weighted linear combination approach. In those areas identified as "susceptible" (based on the surface characteristics), landslides are forecast where and when a rainfall intensity/duration threshold is exceeded. Results are described indicating general agreement with landslide occurrences. However, difficulties in comparing landslide event information (mostly from news reports) with the satellite-based forecasts are analyzed.

Prediction of spatially explicit rainfall intensity-duration thresholds for post-fire debris-flow generation in the western United States

NASA Astrophysics Data System (ADS)

Staley, Dennis; Negri, Jacquelyn; Kean, Jason

2016-04-01

Population expansion into fire-prone steeplands has resulted in an increase in post-fire debris-flow risk in the western United States. Logistic regression methods for determining debris-flow likelihood and the calculation of empirical rainfall intensity-duration thresholds for debris-flow initiation represent two common approaches for characterizing hazard and reducing risk. Logistic regression models are currently being used to rapidly assess debris-flow hazard in response to design storms of known intensities (e.g. a 10-year recurrence interval rainstorm). Empirical rainfall intensity-duration thresholds comprise a major component of the United States Geological Survey (USGS) and the National Weather Service (NWS) debris-flow early warning system at a regional scale in southern California. However, these two modeling approaches remain independent, with each approach having limitations that do not allow for synergistic local-scale (e.g. drainage-basin scale) characterization of debris-flow hazard during intense rainfall. The current logistic regression equations consider rainfall a unique independent variable, which prevents the direct calculation of the relation between rainfall intensity and debris-flow likelihood. Regional (e.g. mountain range or physiographic province scale) rainfall intensity-duration thresholds fail to provide insight into the basin-scale variability of post-fire debris-flow hazard and require an extensive database of historical debris-flow occurrence and rainfall characteristics. Here, we present a new approach that combines traditional logistic regression and intensity-duration threshold methodologies. This method allows for local characterization of both the likelihood that a debris-flow will occur at a given rainfall intensity, the direct calculation of the rainfall rates that will result in a given likelihood, and the ability to calculate spatially explicit rainfall intensity-duration thresholds for debris-flow generation in recently burned areas. Our approach synthesizes the two methods by incorporating measured rainfall intensity into each model variable (based on measures of topographic steepness, burn severity and surface properties) within the logistic regression equation. This approach provides a more realistic representation of the relation between rainfall intensity and debris-flow likelihood, as likelihood values asymptotically approach zero when rainfall intensity approaches 0 mm/h, and increase with more intense rainfall. Model performance was evaluated by comparing predictions to several existing regional thresholds. The model, based upon training data collected in southern California, USA, has proven to accurately predict rainfall intensity-duration thresholds for other areas in the western United States not included in the original training dataset. In addition, the improved logistic regression model shows promise for emergency planning purposes and real-time, site-specific early warning. With further validation, this model may permit the prediction of spatially-explicit intensity-duration thresholds for debris-flow generation in areas where empirically derived regional thresholds do not exist. This improvement would permit the expansion of the early-warning system into other regions susceptible to post-fire debris flow.

On the non-uniqueness of sediment yield

NASA Astrophysics Data System (ADS)

Kim, J.; Ivanov, V. Y.; Katopodes, N.

2012-12-01

Estimation of sediment yield at the catchment scale plays an important role for optimal design of hydraulic structures, such as bridges, culverts, reservoirs, and detention basins, as well as making informed decisions in environmental management. Many experimental studies focused on obtaining flow and sediment data in search of unique relationships between runoff (specifically, volume and peak) and sediment characteristics. These relationships were employed to predict sediment yield from flow information. However, despite the same flow volume, the actual sediment yield produced by river basins can vary significantly depending on several conditions: (i) the catchment size, (ii) land use, topography, and soil type, (iii) climatic variations or characteristics , and (iv) initial conditions of soil moisture and soil surface . Additionally, shield formation by relatively larger particles can be one of the possible controllers of erosion and net sediment transport. Smaller particles have low settling velocities and tend to move far from their original position of detachment. Conversely, larger particles can settle quickly near their original locations. Eventually, such particles can form a shield on soil bed and protect underlying soil from rainfall detachment and runoff entrainment. The shield formation and temporal development can be influenced by rainfall intensity, frequency, and volume. Rainfall influences the generation of runoff leading to different conditions of flow depth and velocity that can perturb intact soil into a loose condition. In this study, we numerically investigate the effects of precipitation patterns on the generation of sediment yield. In particular, we address reasons of non-uniqueness of basin sediment yield for the same runoff volume as well as causes of unsteady phenomena in erosion processes under steady state flow conditions. For numerical simulations, the two-dimensional Hairsine-Rose model coupled with a fully distributed hydrology and hydraulics model (tRIBS-OFM: Triangulated irregular network - based Real time Integrated Basin Simulator-Overland Flow Model) is used.

The experimental study of hydrodynamic characteristics of the overland flow on a slope with three-dimensional Geomat

NASA Astrophysics Data System (ADS)

Wang, Guang-yue; Sun, Guo-rui; Li, Jian-kang; Li, Jiong

2018-02-01

The hydrodynamic characteristics of the overland flow on a slope with a three-dimensional Geomat are studied for different rainfall intensities and slope gradients. The rainfall intensity is adjusted in the rainfall simulation system. It is shown that the velocity of the overland flow has a strong positive correlation with the slope length and the rainfall intensity, the scour depth decreases with the increase of the slope gradient for a given rainfall intensity, and the scour depth increases with the increase of the rainfall intensity for a given slope gradient, the overland flow starts with a transitional flow on the top and finishes with a turbulent flow on the bottom on the slope with the three-dimensional Geomat for different rainfall intensities and slope gradients, the resistance coefficient and the turbulent flow Reynolds number are in positively related logarithmic functions, the resistance coefficient and the slope gradient are in positively related power functions, and the trend becomes leveled with the increase of the rainfall intensity. This study provides some important theoretical insight for further studies of the hydrodynamic process of the erosion on the slope surface with a three-dimensional Geomat.

Application of Statistical Downscaling Techniques to Predict Rainfall and Its Spatial Analysis Over Subansiri River Basin of Assam, India

NASA Astrophysics Data System (ADS)

Barman, S.; Bhattacharjya, R. K.

2017-12-01

The River Subansiri is the major north bank tributary of river Brahmaputra. It originates from the range of Himalayas beyond the Great Himalayan range at an altitude of approximately 5340m. Subansiri basin extends from tropical to temperate zones and hence exhibits a great diversity in rainfall characteristics. In the Northern and Central Himalayan tracts, precipitation is scarce on account of high altitudes. On the other hand, Southeast part of the Subansiri basin comprising the sub-Himalayan and the plain tract in Arunachal Pradesh and Assam, lies in the tropics. Due to Northeast as well as Southwest monsoon, precipitation occurs in this region in abundant quantities. Particularly, Southwest monsoon causes very heavy precipitation in the entire Subansiri basin during May to October. In this study, the rainfall over Subansiri basin has been studied at 24 different locations by multiple linear and non-linear regression based statistical downscaling techniques and by Artificial Neural Network based model. APHRODITE's gridded rainfall data of 0.25˚ x 0.25˚ resolutions and climatic parameters of HadCM3 GCM of resolution 2.5˚ x 3.75˚ (latitude by longitude) have been used in this study. It has been found that multiple non-linear regression based statistical downscaling technique outperformed the other techniques. Using this method, the future rainfall pattern over the Subansiri basin has been analyzed up to the year 2099 for four different time periods, viz., 2020-39, 2040-59, 2060-79, and 2080-99 at all the 24 locations. On the basis of historical rainfall, the months have been categorized as wet months, months with moderate rainfall and dry months. The spatial changes in rainfall patterns for all these three types of months have also been analyzed over the basin. Potential decrease of rainfall in the wet months and months with moderate rainfall and increase of rainfall in the dry months are observed for the future rainfall pattern of the Subansiri basin.

Are erosion regimes in SE Australian forests responding to anthropogenic climate change?

NASA Astrophysics Data System (ADS)

Nyman, P.; Rutherfurd, I.; Lane, P. N. J.; Sheridan, G. J.

2017-12-01

In southeast Australia a series of exceptional climate events over the last decade have resulted in widespread debris flow activity across the region. The Millennium Drought (1996-2010), extreme fire-weather and record breaking rainfall in the La Nina year of 2011 have all contributed to an intensification of processes such as runoff production and mass failures that lead to debris flows. Debris flows in landmark locations such as the Grampians and Wilsons Promontory National Parks in 2011 were triggered by mass failure as a result of large volumes of intense summer rainfall. Runoff generated debris flows in burned areas have been occurring regularly and in large numbers along the East Coast Dividing Range from the Warrumbungle Mountains (New South Wales) in the north to Kinglake (Victoria) in the south. In northeast Victoria debris flows have been delivering sediment to the Ovens River following wildfires in 2003, 2007, 2009 and in 2013. The impact of these erosion events on infrastructure, water quality and aquatic ecosystems are considerable and important questions are emerging around i) how frequently events have occurred in the past, ii) the importance of fire as a geomorphic agent, and iii) the effects of climate change on erosion regimes. In this paper we investigate the conditions under which these debris flows occurred, and examine the underlying climatic events in context of historical records. Using data on rainfall distributions and fire history dating back to the 1960s we quantify the frequency with which catchments are primed for extreme erosion events. With these data we begin to speculate on whether or not current catchment conditions (e.g. soil depths, colluvial storage and accumulation rate) is consistent with the erosion regimes we observe. The broader aim of our research is to quantify debris flow thresholds using geophysical response models and use these models to determine the sensitivity of debris flow frequency to climatic forcing. In the presentation we outline a conceptual framework for combining such models with data on past debris flow activity to conduct an attribution study into the effect of anthropogenic climate change on erosion regimes in southeast Australian temperate forests.

The variation of riverbed material due to tropical storms in Shi-Wen River, Taiwan.

PubMed

Lin, Chin-Ping; Wang, Yu-Min; Tfwala, Samkele S; Chen, Ching-Nuo

2014-01-01

Taiwan, because of its location, is a flood prone region and is characterised by typhoons which brings about two-thirds to three quarters of the annual rainfall amount. Consequently, enormous flows result in rivers and entrain some fractions of the grains that constitute the riverbed. Hence, the purpose of the study is to quantify the impacts of these enormous flows on the distribution of grain size in riverbeds. The characteristics of riverbed material prior to and after the typhoon season are compared in Shi-Wen River located at southern Taiwan. These include grain size variation, bimodality, and roughness coefficient. A decrease (65%) and increase (50%) in geometric mean size of grains were observed for subsurface and surface bed material, respectively. Geometric standard deviation decreased in all sites after typhoon. Subsurface material was bimodal prior to typhoons and polymodal after. For surface material, modal class is in the gravel class, while after typhoons it shifts towards cobble class. The reduction in geometric mean resulted to a decrease in roughness coefficient by up to 30%. Finally, the relationship of Shields and Froude numbers are studied and a change in the bed form to antidunes and transition form is observed, respectively.

The Variation of Riverbed Material due to Tropical Storms in Shi-Wen River, Taiwan

PubMed Central

Lin, Chin-Ping; Tfwala, Samkele S.; Chen, Ching-Nuo

2014-01-01

Taiwan, because of its location, is a flood prone region and is characterised by typhoons which brings about two-thirds to three quarters of the annual rainfall amount. Consequently, enormous flows result in rivers and entrain some fractions of the grains that constitute the riverbed. Hence, the purpose of the study is to quantify the impacts of these enormous flows on the distribution of grain size in riverbeds. The characteristics of riverbed material prior to and after the typhoon season are compared in Shi-Wen River located at southern Taiwan. These include grain size variation, bimodality, and roughness coefficient. A decrease (65%) and increase (50%) in geometric mean size of grains were observed for subsurface and surface bed material, respectively. Geometric standard deviation decreased in all sites after typhoon. Subsurface material was bimodal prior to typhoons and polymodal after. For surface material, modal class is in the gravel class, while after typhoons it shifts towards cobble class. The reduction in geometric mean resulted to a decrease in roughness coefficient by up to 30%. Finally, the relationship of Shields and Froude numbers are studied and a change in the bed form to antidunes and transition form is observed, respectively. PMID:24526910

Potentiometric Surface of the Upper Floridan Aquifer in the St. Johns River Water Management District and Vicinity, Florida, May 2007

USGS Publications Warehouse

Kinnaman, Sandra L.; Dixon, Joann F.

2007-01-01

Introduction This map depicts the potentiometric surface of the Upper Floridan aquifer in the St. Johns River Water Management District and vicinity for May 2007. Potentiometric contours are based on water-level measurements collected at 566 wells during the period May 4-June 11 near the end of the dry season, however most of the water level data for this map were collected by the U.S. Geological Survey during the period May 21-25, 2007. Some contours are inferred from previous potentiometric-surface maps with larger well networks. The potentiometric surface of the carbonate Upper Floridan aquifer responds mainly to rainfall, and more locally, to ground-water withdrawals and spring flow. Potentiometric-surface highs generally correspond to topographic highs where the aquifer is recharged. Springs and areas of diffuse upward leakage naturally discharge water from the aquifer and are most prevalent along the St. Johns River. Areas of discharge are reflected by depressions in the potentiometric surface. Ground-water withdrawals locally have lowered the potentiometric surface. Ground water in the Upper Floridan aquifer generally flows from potentiometric highs to potentiometric lows in a direction perpendicular to the contours.

River catchment rainfall series analysis using additive Holt-Winters method

NASA Astrophysics Data System (ADS)

Puah, Yan Jun; Huang, Yuk Feng; Chua, Kuan Chin; Lee, Teang Shui

2016-03-01

Climate change is receiving more attention from researchers as the frequency of occurrence of severe natural disasters is getting higher. Tropical countries like Malaysia have no distinct four seasons; rainfall has become the popular parameter to assess climate change. Conventional ways that determine rainfall trends can only provide a general result in single direction for the whole study period. In this study, rainfall series were modelled using additive Holt-Winters method to examine the rainfall pattern in Langat River Basin, Malaysia. Nine homogeneous series of more than 25 years data and less than 10% missing data were selected. Goodness of fit of the forecasted models was measured. It was found that seasonal rainfall model forecasts are generally better than the monthly rainfall model forecasts. Three stations in the western region exhibited increasing trend. Rainfall in southern region showed fluctuation. Increasing trends were discovered at stations in the south-eastern region except the seasonal analysis at station 45253. Decreasing trend was found at station 2818110 in the east, while increasing trend was shown at station 44320 that represents the north-eastern region. The accuracies of both rainfall model forecasts were tested using the recorded data of years 2010-2012. Most of the forecasts are acceptable.

Influence of Environmental Factors and Human Activity on the Presence of Salmonella Serovars in a Marine Environment

PubMed Central

Martinez-Urtaza, Jaime; Saco, Montserrat; de Novoa, Jacobo; Perez-Piñeiro, Pelayo; Peiteado, Jesus; Lozano-Leon, Antonio; Garcia-Martin, Oscar

2004-01-01

The temporal and spatial distribution of Salmonella contamination in the coastal waters of Galicia (northwestern Spain) relative to contamination events with different environmental factors (temperature, wind, hours of sunlight, rainfall, and river flow) were investigated over a 4-year period. Salmonellae were isolated from 127 of 5,384 samples of molluscs and seawater (2.4%), and no significant differences (P < 0.05) between isolates obtained in different years were observed. The incidence of salmonellae was significantly higher in water column samples (2.9%) than in those taken from the marine benthos (0.7%). Of the 127 strains of Salmonella isolated, 20 different serovars were identified. Salmonella enterica serovar Senftenberg was the predominant serovar, being represented by 54 isolates (42.5%), followed by serovar Typhimurium (19 isolates [15%]) and serovar Agona (12 isolates [9.4%]). Serovar Senftenberg was detected at specific points on the coast and could not be related to any of the environmental parameters analyzed. All serovars except Salmonella serovar Senftenberg were found principally in the southern coastal areas close to the mouths of rivers, and their incidence was associated with high southwestern wind and rainfall. Using multiple logistic regression analysis models, the prevalence of salmonellae was best explained by environmental parameters on the day prior to sampling. Understanding this relationship may be useful for the control of molluscan shellfish harvests, with wind and rainfall serving as triggers for closure. PMID:15066800

Hydrogeological characterization and environmental effects of the deteriorating urban karst groundwater in a karst trough valley: Nanshan, SW China

NASA Astrophysics Data System (ADS)

Jiang, Yongjun; Cao, Min; Yuan, Daoxian; Zhang, Yuanzhu; He, Qiufang

2018-02-01

The unique hydrogeology of karst makes the associated groundwater respond quickly to rainfall events and vulnerable to anthropogenic pollutions. In this study, high-frequency monitoring of spring discharge, temperature, electrical conductivity (EC) and pH, along with monthly hydrochemical and microbial analyses, was undertaken at the outlet of Laolondong karst underground river in Nanshan, southwestern China. The aim was to explore the environmental effects of the catchment's urban area on the karst groundwater resources. The monitoring data of a tracer test and the response of discharge to rainfall events demonstrate that conduits and narrow fissures coexist in the Laolongdong karst aquifer. The EC, Na+, Cl- and SO4 2- values (840 μS/cm, 33.7, 38.6 and 137.2 μg/L, respectively), along with high concentrations of fecal coliform bacteria, at the outlet indicate considerable urban pollution in this area. The contaminants sulfate and nitrate showed different relationships with discharge and EC in different stages of a rainfall event. This behavior provided information about aquifer structure and the influence of transport properties. Meanwhile, the hydrological processes of groundwater flow could be modified by urbanization and result in increasing magnitude of urban floods in the underground river. In addition, sulfuric and nitric acids introduced by urbanization not only impact the karst groundwater quality, but also result in a significant perturbation to the carbon cycling system in the karst area.

W-band spaceborne radar observations of atmospheric river events

NASA Astrophysics Data System (ADS)

Matrosov, S. Y.

2010-12-01

While the main objective of the world first W-band radar aboard the CloudSat satellite is to provide vertically resolved information on clouds, it proved to be a valuable tool for observing precipitation. The CloudSat radar is generally able to resolve precipitating cloud systems in their vertical entirety. Although measurements from the liquid hydrometer layer containing rainfall are strongly attenuated, special retrieval approaches can be used to estimate rainfall parameters. These approaches are based on vertical gradients of observed radar reflectivity factor rather than on absolute estimates of reflectivity. Concurrent independent estimations of ice cloud parameters in the same vertical column allow characterization of precipitating systems and provide information on coupling between clouds and rainfall they produce. The potential of CloudSat for observations atmospheric river events affecting the West Coast of North America is evaluated. It is shown that spaceborne radar measurements can provide high resolution information on the height of the freezing level thus separating areas of rainfall and snowfall. CloudSat precipitation rate estimates complement information from the surface-based radars. Observations of atmospheric rivers at different locations above the ocean and during landfall help to understand evolutions of atmospheric rivers and their structures.

The implications of using large ensembles of climate scenarios for the management of river ecology in an English chalk stream

NASA Astrophysics Data System (ADS)

Fung, C. F.; Lopez, A.; New, M.

2009-04-01

Climate change is likely to impact on freshwater ecology, the delivery of regulatory commitments to ecological status and the management of water resources. It is becoming increasingly important for European environment agencies to use and develop methods to aid planning and abstraction licensing procedures and policies in the face of climate change and with the introduction of the Water Framework Directive. Studies have been carried out in the past to investigate the implications of climate change for biodiversity. However, predicting the future is fraught with uncertainty, an area which has not been dealt with in great depth in the past. This study has been undertaken to draw on the results of new methodologies to address the uncertainties inherent in modelling future climate and assess their usability for decision-making in water resources allocations specifically in considering interactions between flow and invertebrate communities The River Itchen was chosen as the case study catchment on the strength of having a long-term coupled ecological and flow dataset and having been an area of intensive study in the past. It is a chalk stream located in the south of England and a candidate Special Area of Conservation. It has also been designated a Special Site of Scientific Interest achieved due to the number of rare species, and the richness of the macro-invertebrate community in the river catchment. An ensemble of 246 transient simulations for future climate was obtained from ClimatePrediction.net which were then used to drive a rainfall-runoff model. In order to link the modelled river flow to ecology, the Lotic Invertebrate Flow Evaluation score has been used where the invertebrate community is linked to flow largely through sensitivity to water velocity and siltation, driven by flow variability at sites with fixed channel dimensions The large ensemble of climate scenarios and thereby flow and ecological indices allows the exploration of the risk of the river of not meeting environmental flow targets in the future. Three sets of environmental flow targets which were drawn up by the Environment Agency for England and Wales for the River Itchen were tested and show that it may be difficult to maintain a natural chalk stream invertebrate community in the River Itchen in the future. The ensemble also shows low flows regularly extending from August to December which could result in the loss of a high proportion of individuals recruited that year. This would in turn lead to diminished over-wintering populations, with potentially catastrophic consequences for the following years breeding and recruitment programme. Due to a paucity of quantitative data for the response of macroinvertebrates to multi-year droughts, to provide a richer story, a matrix has been proposed for analysing the effects on biodiversity of the river which combines both the thresholds derived previously and expert opinion on how the ecology of the River Itchen will react to climate change. The matrices also provide a more accessible way of communicating rather complex information to a wider community of decision-makers. Should large changes in flow arise in the future it is likely that some form of action will be taken to mitigate or adapt to the impacts of climate change. Maintaining the ecological status of the river throug river support, i.e. augmenting river flow by pumping from the groundwater aquifer, has also been investigated. However, by augmenting the flow, the high flows are also reduced which can be important for scouring the river bed and removing silt to the benefit of the invertebrate community. Therefore at some point further augmentation may need to be curtailed in order to maintain high flows.

A water balance approach to enhance national (GB) Daily Landslide Hazard Assessments

NASA Astrophysics Data System (ADS)

Dijkstra, Tom; Reeves, Helen; Freeborough, Katy; Dashwood, Claire; Pennington, Catherine; Jordan, Hannah; Hobbs, Peter; Richardson, Jennifer; Banks, Vanessa; Cole, Steven; Wells, Steven; Moore, Robert

2017-04-01

The British Geological Survey (BGS) is a member of the Natural Hazards Partnership (NHP) and delivers a national (GB) daily landslide hazard assessment (DLHA). The DLHA is based largely on 'expert' driven evaluations of the likelihood of landslides in response to antecedent ground conditions, adverse weather and reported landslide events. It concentrates on shallow translational slides and debris flows - events that most frequently have societal consequences by disrupting transport infrastructure and affecting buildings. Considerable experience with the issuing of DLHAs has been gained since 2012. However, it remains very difficult to appropriately assess changing ground conditions throughout GB even when good quality precipitation forecasts are available. Soil moisture sensors are available, but the network is sparse and not yet capable of covering GB to the detail required to underpin the forecasts. Therefore, we developed an approach where temporal and spatial variations in soil moisture can be obtained from a water balance model, representing processes in the near-surface and configured on a relatively coarse grid of 1 km2. Model outputs are not intended to be relevant to the slope scale. The assumption is that the likelihood of landslides being triggered by rainfall is dependent upon the soil moisture conditions of the near-surface, in combination with how much rain is forecast to occur for the following day. These variables form the basis for establishing thresholds to guide the issuing of DLHA and early warnings. The main aim is to obtain an insight into regional patterns of change and threshold exceedance. The BGS water balance model is still in its infancy and it requires substantial work to fine-tune and validate it. To test the performance of the BGS model we focused on an analysis of Scottish landslides (2004-2015) comprising translational slides and debris flows where the BGS model is conditionally evaluated against the Grid-to-Grid (G2G) Model. G2G is a physical-conceptual distributed hydrological model developed by the Centre for Ecology & Hydrology, also an NHP member. G2G is especially suited to simulate river flows over ungauged areas and has the capability to forecast fluvial river flows at any location across a gridded model domain. This is achieved by using spatial datasets on landscape properties - terrain, land-cover, soil and geology - in combination with gridded time-series of rainfall to shape a rainfall pattern into a river flow response over the model domain. G2G is operational on a 1 km2 grid over the GB and outputs soil moisture estimates that take some account of terrain slope in its water balance calculation. This research is part of an evolutionary process where capabilities of establishing the likelihood of landslides will develop as datasets are becoming increasingly detailed (and accessible) and the representation of hydrogeological and geotechnical processes continues to develop.

Definition of Pluviometric Thresholds For A Real Time Flood Forecasting System In The Arno Watershed

NASA Astrophysics Data System (ADS)

Amadio, P.; Mancini, M.; Mazzetti, P.; Menduni, G.; Nativi, S.; Rabuffetti, D.; Ravazzani, G.; Rosso, R.

The pluviometric flood forecasting thresholds are an easy method that helps river flood emergency management collecting data from limited area meteorologic model or telemetric raingauges. The thresholds represent the cumulated rainfall depth which generate critic discharge for a particular section. The thresholds were calculated for different sections of Arno river and for different antecedent moisture condition using the flood event distributed hydrologic model FEST. The model inputs were syntethic hietographs with different shape and duration. The system realibility has been verified by generating 500 year syntethic rainfall for 3 important subwatersheds of the studied area. A new technique to consider spatial variability of rainfall and soil properties effects on hydrograph has been investigated. The "Geomorphologic Weights" were so calculated. The alarm system has been implemented in a dedicated software (MIMI) that gets measured and forecast rainfall data from Autorità di Bacino and defines the state of the alert of the river sections.

Comparison and applicability of landslide susceptibility models based on landslide ratio-based logistic regression, frequency ratio, weight of evidence, and instability index methods in an extreme rainfall event

NASA Astrophysics Data System (ADS)

Wu, Chunhung

2016-04-01

Few researches have discussed about the applicability of applying the statistical landslide susceptibility (LS) model for extreme rainfall-induced landslide events. The researches focuses on the comparison and applicability of LS models based on four methods, including landslide ratio-based logistic regression (LRBLR), frequency ratio (FR), weight of evidence (WOE), and instability index (II) methods, in an extreme rainfall-induced landslide cases. The landslide inventory in the Chishan river watershed, Southwestern Taiwan, after 2009 Typhoon Morakot is the main materials in this research. The Chishan river watershed is a tributary watershed of Kaoping river watershed, which is a landslide- and erosion-prone watershed with the annual average suspended load of 3.6×107 MT/yr (ranks 11th in the world). Typhoon Morakot struck Southern Taiwan from Aug. 6-10 in 2009 and dumped nearly 2,000 mm of rainfall in the Chishan river watershed. The 24-hour, 48-hour, and 72-hours accumulated rainfall in the Chishan river watershed exceeded the 200-year return period accumulated rainfall. 2,389 landslide polygons in the Chishan river watershed were extracted from SPOT 5 images after 2009 Typhoon Morakot. The total landslide area is around 33.5 km2, equals to the landslide ratio of 4.1%. The main landslide types based on Varnes' (1978) classification are rotational and translational slides. The two characteristics of extreme rainfall-induced landslide event are dense landslide distribution and large occupation of downslope landslide areas owing to headward erosion and bank erosion in the flooding processes. The area of downslope landslide in the Chishan river watershed after 2009 Typhoon Morakot is 3.2 times higher than that of upslope landslide areas. The prediction accuracy of LS models based on LRBLR, FR, WOE, and II methods have been proven over 70%. The model performance and applicability of four models in a landslide-prone watershed with dense distribution of rainfall-induced landslide are interesting and meaningful. Eight landslide-related factors, including elevation, slope, aspect, geology, accumulated rainfall during 2009 Typhoon Morakot, landuse, distance to the fault, and distance to the rivers, were considered in this research. The research builds and compares the difference of the LS maps based on four methods. The average LS value from each method is 0.27 for LRBLR, 0.368 for FR, 0.553 for WOE, and 0.498 for II. The correlation analysis was conducted to identify similarities between the four LS maps. The correlation coefficients are 0.913, 0.829, 0.930, 0.756, 0.729, and 0.652 for the LRBLR vs FR, LRBLR vs WOE, FR vs WOE, LRBLR vs II, FR vs II, and WOE vs II. The research compares the model performance of four LS maps by calculating the AUC value (area under the ROC curve) and ACR value (average correct-predicted ratio). The AUC values of LS maps based on LRBLR, FR, WOE, and II methods are 0.819, 0.819, 0.822 and 0.785. The ACR values of LS maps based on LRBLR, FR, WOE, and II methods are 75.1%, 73.7%, 68.4%, and 64.2%. The results indicate that the model performance based on LRBLR method in an extreme rainfall-landslide event is better than that based on the other three methods.

Sediment source detection by stable isotope analysis, carbon and nitrogen content and CSSI in a small river of the Swiss Plateau

NASA Astrophysics Data System (ADS)

SchindlerWildhaber, Yael; Alewell, Christine; Birkholz, Axel

2014-05-01

Suspended sediment (SS) and organic matter in rivers can harm the fauna by affecting health and fitness of free swimming fish and by causing siltation of the riverbed. The temporal and spatial dynamics of sediment, carbon (C) and nitrogen (N) during the brown trout spawning season in a small river of the Swiss Plateau were assessed and C isotopes as well as the C/N atomic ratio were used to distinguish autochthonous and allochthonous sources of organic matter in SS loads. The visual basic program IsoSource with 13Ctot and 15N as input isotopes was used to quantify the temporal and spatial sources of SS. We determined compound specific stable carbon isotopes (CSSI) in fatty acids of possible sediment source areas to the stream in addition and compared them to SS from selected high flow and low flow events. Organic matter concentrations in the infiltrated and suspended sediment were highest during low flow periods with small sediment loads and lowest during high flow periods with high sediment loads. Peak values in nitrate and dissolved organic C were measured during high flow and high rainfall, probably due to leaching from pasture and arable land. The organic matter was of allochthonous sources as indicated by the C/N atomic ratio and δ13Corg. Organic matter in SS increased from up- to downstream due to an increase in sediment delivery from pasture and arable land downstream of the river. While the major sources of SS are pasture and arable land during base flow conditions, SS from forest soils increased during heavy rain events and warmer winter periods most likely due to snow melt which triggered erosion. Preliminary results of CSSI analysis of sediment source areas and comparison to SS of selected events indicate that differences in d13C values of individual fatty acids are too small to differentiate unambiguously between sediment sources.

Discharge data assimilation in a distributed hydrologic model for flood forecasting purposes

NASA Astrophysics Data System (ADS)

Ercolani, G.; Castelli, F.

2017-12-01

Flood early warning systems benefit from accurate river flow forecasts, and data assimilation may improve their reliability. However, the actual enhancement that can be obtained in the operational practice should be investigated in detail and quantified. In this work we assess the benefits that the simultaneous assimilation of discharge observations at multiple locations can bring to flow forecasting through a distributed hydrologic model. The distributed model, MOBIDIC, is part of the operational flood forecasting chain of Tuscany Region in Central Italy. The assimilation system adopts a mixed variational-Monte Carlo approach to update efficiently initial river flow, soil moisture, and a parameter related to runoff production. The evaluation of the system is based on numerous hindcast experiments of real events. The events are characterized by significant rainfall that resulted in both high and relatively low flow in the river network. The area of study is the main basin of Tuscany Region, i.e. Arno river basin, which extends over about 8300 km2 and whose mean annual precipitation is around 800 mm. Arno's mainstream, with its nearly 240 km length, passes through major Tuscan cities, as Florence and Pisa, that are vulnerable to floods (e.g. flood of November 1966). The assimilation tests follow the usage of the model in the forecasting chain, employing the operational resolution in both space and time (500 m and 15 minutes respectively) and releasing new flow forecasts every 6 hours. The assimilation strategy is evaluated in respect to open loop simulations, i.e. runs that do not exploit discharge observations through data assimilation. We compare hydrographs in their entirety, as well as classical performance indexes, as error on peak flow and Nash-Sutcliffe efficiency. The dependence of performances on lead time and location is assessed. Results indicate that the operational forecasting chain can benefit from the developed assimilation system, although with a significant variability due to the specific characteristics of any single event, and with downstream locations more sensitive to observations than upstream sites.

Rainfall runoff modelling of the Upper Ganga and Brahmaputra basins using PERSiST.

PubMed

Futter, M N; Whitehead, P G; Sarkar, S; Rodda, H; Crossman, J

2015-06-01

There are ongoing discussions about the appropriate level of complexity and sources of uncertainty in rainfall runoff models. Simulations for operational hydrology, flood forecasting or nutrient transport all warrant different levels of complexity in the modelling approach. More complex model structures are appropriate for simulations of land-cover dependent nutrient transport while more parsimonious model structures may be adequate for runoff simulation. The appropriate level of complexity is also dependent on data availability. Here, we use PERSiST; a simple, semi-distributed dynamic rainfall-runoff modelling toolkit to simulate flows in the Upper Ganges and Brahmaputra rivers. We present two sets of simulations driven by single time series of daily precipitation and temperature using simple (A) and complex (B) model structures based on uniform and hydrochemically relevant land covers respectively. Models were compared based on ensembles of Bayesian Information Criterion (BIC) statistics. Equifinality was observed for parameters but not for model structures. Model performance was better for the more complex (B) structural representations than for parsimonious model structures. The results show that structural uncertainty is more important than parameter uncertainty. The ensembles of BIC statistics suggested that neither structural representation was preferable in a statistical sense. Simulations presented here confirm that relatively simple models with limited data requirements can be used to credibly simulate flows and water balance components needed for nutrient flux modelling in large, data-poor basins.

Evaluation of statistical and rainfall-runoff models for predicting historical daily streamflow time series in the Des Moines and Iowa River watersheds

USGS Publications Warehouse

Farmer, William H.; Knight, Rodney R.; Eash, David A.; Kasey J. Hutchinson,; Linhart, S. Mike; Christiansen, Daniel E.; Archfield, Stacey A.; Over, Thomas M.; Kiang, Julie E.

2015-08-24

Daily records of streamflow are essential to understanding hydrologic systems and managing the interactions between human and natural systems. Many watersheds and locations lack streamgages to provide accurate and reliable records of daily streamflow. In such ungaged watersheds, statistical tools and rainfall-runoff models are used to estimate daily streamflow. Previous work compared 19 different techniques for predicting daily streamflow records in the southeastern United States. Here, five of the better-performing methods are compared in a different hydroclimatic region of the United States, in Iowa. The methods fall into three classes: (1) drainage-area ratio methods, (2) nonlinear spatial interpolations using flow duration curves, and (3) mechanistic rainfall-runoff models. The first two classes are each applied with nearest-neighbor and map-correlated index streamgages. Using a threefold validation and robust rank-based evaluation, the methods are assessed for overall goodness of fit of the hydrograph of daily streamflow, the ability to reproduce a daily, no-fail storage-yield curve, and the ability to reproduce key streamflow statistics. As in the Southeast study, a nonlinear spatial interpolation of daily streamflow using flow duration curves is found to be a method with the best predictive accuracy. Comparisons with previous work in Iowa show that the accuracy of mechanistic models with at-site calibration is substantially degraded in the ungaged framework.

Impacts of river-bed aggradation and lahar activity downstream of Santiaguito Volcano, Guatemala: a Landsat Thematic Mapper perspective

NASA Astrophysics Data System (ADS)

Flynn, L. P.; Harris, A. J.; Davies, M. A.; Vallence, J. W.; Rose, W. I.

2002-12-01

Lava extrusion at Santiaguito volcano, Guatemala and rainfall runoff cause lahars and river-bed aggradation downstream of the volcano. We present a method that uses vegetation indices extracted from Landsat Thematic Mapper (TM) data to identify zones of impact. The method differentiates vegetation-free and vegetated pixels, constrains areas affected by aggradation, and generates catchment-wide aggradation maps. Application of the technique to 22 TM images acquired between 1987 and 2000 helped us to measure, map and track temporal and spatial variations in the area of lahar impact and river aggradation. To verify our TM-based analyses we carried out 3 field campaigns between 2000 and 2002, during which we focused on a segment of aggraded river beds ~8 km from Santiaguito. We then used our TM and field-based studies to document and validate changes at this location, as follows: (1) Time varying effects of aggradation. The main river to head at Santiaguito is R¡o Nima II. The TM analysis indicated development of a new channel cutting across farm land on the western edge of R¡o Nima II between 1996 and 2000. Field checking showed that development of an aggraded, convex, bed profile caused channels to flow westward away from the aggraded river-channel system. (2) Emplacement of lava flows. The TM time series indicated that a new lava flow extended into the upper reaches of the Rio Nima I during 1996 and triggered aggradation. Field checking confirmed that a new supply of volcaniclastic material had extended aggradation into this previously unaffected drainage. (3) River capture. Capture of R¡o Nima I by R¡o Samal has increased aggradation of along new sections of R¡o Samal , an effect evident in our TM mapping. Field checking showed that, although R¡o Samala does not head at Santiaguito, the new supply of material from R¡o Nima I triggered rapid aggradation of R¡o Samal after 1996.

Potentially dangerous 24-hour rainfall in the Provadiyska vally system at the end of the 20th and early 21st Centuries

NASA Astrophysics Data System (ADS)

Vladev, Dimitar

2018-03-01

Extreme rainfalls are of paramount importance for the formation of river springs and, consequently, the occurrence of spills and floods. The article presents the results of a case study of the potentially dangerous 24-hour eruptions in the Provadiyska valley system from the end of the 20th and the beginning of the 21st century. Particular attention is paid to the morphometric parameters and the configuration of the river-valley supply network of the Provadiyska river. On this basis, there are defined areas in which there are favorable conditions for forming high river waves.

Sediment and Phosphorus losses by Surface Runoff from a Catchment in the Humid Pampa Landscape, Argentina Republic

NASA Astrophysics Data System (ADS)

Méndez M., A.; Díaz E., L.; Lenzi M., L.; Lado, M.; Vidal-Vázquez, E.

2015-04-01

The estimation of sediment and phosphorus transfers from soil into watersheds as a result of agricultural activity is a key aspect for characterizing the sustainability of current land use systems. The objective of the present study was to quantify the temporal evolution of suspended sediment and dissolved phosphorus losses from the upper basin of the Gualeguaychú River. The studied catchment has an area of 483 Km2 and is located in the Entre Ríos province, Argentina Republic. The climate is subtropical humid with average annual rainfall of 1200 mm. Soils are characterized by very low infiltration rates. Land use was assessed by remote sensing and GIS tools, and consists of: 31% abandoned rice fields, 20% naturalized fields, 20% soybean (second cycle), 10% soybean (first cycle), 7% rice, 4% Pasture, and the remaining 7% is devoted to civil and road works, native forests and other crops. Low soil infiltration capacity, together with landscape geomorphological traits of the studied landscape and zonal rainfall regime, typically originates periods with high surface runoff volumes, mainly in autumn, spring and summer months. The study was conducted during a period of eight years. Instantaneous water flow measurements (discharge) were estimated in a control section of Gualeguaychú River from hydrometer reading and the rating curve of height-flow. In addition, 134 water samples of 2000 cm3 were collected during the study period to analyze the concentration of suspended sediments and dissolved phosphorus. The instantaneous flow was estimated with the hydrometer reading and the application of curve of height - flow. The discharge range was from 0.14 to 128 m3/sec, indicating a high variability in the response of the catchment to seasonal rainfall. On average suspended sediment and dissolved phosphorus losses of the experimental catchment were 1.42 Mg and 0.335 Kg per hectare/year, respectively. It was also shown that few events of high rainfall that generate excess runoff were responsible for the most of recorded losses of sediment and phosphorus. Moreover, the highest exportation of sediments and phosphorus from soil to streamflow occurred in the spring and summer period. The daily losses of phosphorus or sediments were mainly explained by the amount of precipitation accumulated during the five days prior to sampling, as shown by regression analysis, and a higher coefficient of determination was obtained for samples extracted during the summer season. This response mainly has been demonstrated to be produced in periods with higher amounts of precipitation equal or greater than 35 mm arising in this season, which are characteristic for summer storms with high rain intensities, and therefore greater erosive power.

Impacts of climate change on rainfall, seasonal flooding, and evapotranspiration in the Okavango Delta, Botswana

NASA Astrophysics Data System (ADS)

Konecky, B. L.; Noone, D.; Mosimanyana, E.; Gondwe, M.

2016-12-01

The Okavango Delta in northern Botswana is one of the world's richest biodiversity hotspots. A UNESCO World Heritage Site, the Delta is known for its unique annual flood pulse, whereby the wetland and its neighboring river systems are inundated with waters that travel nearly 1000 km before reaching this subtropical, semi-arid destination. The livelihoods of northern Botswana's ecosystems and human populations rely on these floods to supplement the short and variable rainy season, which in many years is too minimal to ameliorate regional drought. However, anthropogenic climate change is reducing the amount of water that reaches the delta by increasing evaporation from soils and rivers, and transpiration by vegetation, during its long transit to Botswana. Future changes in rainfall patterns, extreme events, and increased upstream water use could exacerbate this water stress. Unfortunately, it remains difficult to assess the impacts of climate change on the delta because few data exist to constrain its complex climatic and seasonal water cycling regimes. This study presents a novel characterization of the water cycle in and around the Okavango Delta based on a survey of free-flowing surface waters, stagnant pools, precipitation, and groundwater carried out during the 2016 rainy and early-flood season. We use stable isotope and water quality data to assess local moisture sources, transport, evaporation, wetland flushing, and land-atmosphere exchanges, all of which are subject to change under global warming. We find a strong evaporation gradient and a progressive flushing of stagnant swamp waters along the northeastern and northwestern channels of the Delta. The evaporation gradient is more limited in nearby rivers with more limited wetlands. We contrast results with a survey of the Delta performed in the 1970's in order to assess changes over the past 40 years. Since some of these changes may arise from rainfall supply, we also present new analysis of rainfall moisture sources and transport characteristics during 2016's unusually-late wet season, using both in situ and satellite data. Implications are discussed for the large-scale water cycling over the southern African continental interior. These data serve as a baseline for future monitoring under climate change.

Monitoring Multitemporal Soil Moisture, Rainfall, and ET in Lake Manatee Watershed, South Florida under Global Changes

NASA Astrophysics Data System (ADS)

Chang, N.

2009-12-01

Ni-Bin Chang1, Ammarin Daranpob 1, and Y. Jeffrey Yang2 1Civil, Environmental, and Construction Engineering Department, University of Central Florida, Orlando FL, USA 2Water Supply and Water Resources Division, National Risk Management Research Laboratory, U.S. EPA, Cincinnati, Ohio, USA ASBTRACT: Global climate change and its related impacts on water supply are universally recognized. The Atlantic Multidecadal Oscillation (AMO), which is based on long term changes in the temperature of the surface of the North Atlantic Ocean, is a source of changes in river flow patterns in Florida. The AMO has a multi-decadal frequency. Under its impact, several distinct types of river patterns were identified within Florida, including a Southern River Pattern (SRP), a Northern River Pattern (NRP), a Bimodal River Pattern (BRP), etc. (Kelley and Gore, 2008). Some SRPs are present in the South Florida Water Management District (SFWMD). Changes in river flows occur because significant sea surface temperature (SST) changes affect continental rainfall patterns. It had been observed that, between AMO warm (i.e., from 1939 to 1968) and cold phases (i.e., from 1969 to 1993), the average daily inflow to Lake Okeechobee varies by 40% in the transition from the warm to cold phases in South Florida. The Manatee County is located in the Southern Water Use Caution Area (SWUCA) due to the depletion of the Upper Floridian Aquifer and its entire western portion of the County is designated as part of the Most Impacted Area (MIA) within the Eastern Tampa Bay Water Use Caution Area relative to the SWUCA. Major source of Manatee County’s water is an 332 Km2 (82,000-acre) watershed (i.e., Lake Manatee Watershed) that drains into the man-made Lake Manatee Reservoir. The lake has a total volume of 0.21 billion m3 (7.5 billion gallons) and will cover 7.3 Km2 (1,800 acres) when full. The proper use of remote sensing images and sensor network technologies can provide information on both spatial and temporal distributions of key variables in the hydrological cycle, such as soil moisture, evapotranspiration (ET) and precipitation. The multi-sensor platform may include not only in-situ sensor network, ground-based radar, air-borne aircraft, but also even space-borne satellites. The use of a decadal-scale historical record from 1998 to 2008 to support such a trend analysis via NEXRAD (Rainfall), GOES (ET), and MODIS (soil moisture) satellite images may uniquely support middle-term and long-term water resources management in the near future. This study confirms that the potential of using remotely sensed time-series biophysical and ecohydrological states of landscape to characterize soil moisture condition, ET, and other states should be further investigated based on the pros and cons of each type of satellite imageries so as to maximize the beneficial use of remote sensing.

Distribution Patterns of Land Surface Water from Hurricanes Katrina and Rita

NASA Image and Video Library

2005-10-12

The above images, derived from NASA QuikScat satellite data, show the extensive pattern of rain water deposited by Hurricanes Katrina and Rita on land surfaces over several states in the southern and eastern United States. These results demonstrate the capability of satellite scatterometers to monitor changes in surface water on land. The color scale depicts increases in radar backscatter (in decibels) between the current measurement and the mean of measurements obtained during the previous two weeks. The backscatter can be calibrated to measure increases in surface soil moisture resulting from rainfall. The yellow color corresponds to an increase of approximately 10 percent or more in surface soil moisture according to the calibration site of Lonoke, Ark. The two hurricanes deposited excessive rainfall over extensive regions of the Mississippi River basin. Basins the size of the Mississippi can take up to several weeks before such excess rainfall significantly increases the amount of river discharge in large rivers such as the Mississippi. With hurricane season not over until November 30, the potential exists for significant flooding, particularly if new rain water is deposited by new hurricanes when river discharge peaks up as a result of previous rainfalls. River discharge should be closely monitored to account for this factor in evaluating potential flood conditions in the event of further hurricanes. http://photojournal.jpl.nasa.gov/catalog/PIA03029

Modeling the Effects of Land Use and Climate Change on Streamflow in the Delaware River Basin

NASA Astrophysics Data System (ADS)

Kwon, P. Y. S.; Endreny, T. A.; Kroll, C. N.; Williamson, T. N.

2014-12-01

Forest-cover loss and drinking-water reservoirs in the upper Delaware River Basin of New York may alter summer low streamflows, which could degrade the in-stream habitat for the endangered dwarf wedgemussel. Our project analyzes how flow statistics change with land-cover change for 30-year increments of model-simulated streamflow hydrographs for three watersheds of concern to the National Park Service: the East Branch, West Branch, and main stem of the Delaware River. We use four treatments for land cover ranging from historical high to low forest cover. We subject each land cover to adjusted GCM climate scenarios for 1600, 1900, 1940, and 2040 to isolate land cover from potential climate-change effects. Hydrographs are simulated using the Water Availability Tool for Environmental Resources (WATER), a TOPMODEL-based United States Geological Survey hydrologic decision-support tool, which uses the variable-source-area concept and water budgets to generate streamflow. Model parameters for each watershed change with land-use, and capture differences in soil-physical properties that control how rainfall infiltrates, evaporates, transpires, is stored in the soil, and moves to the stream. Our results analyze flow statistics used as indicators of hydrologic alteration, and access streamflow events below the critical flow needed to provide sustainable habitat for dwarf wedgemussels. These metrics will demonstrate how changes in climate and land use might affect flow statistics. Initial results show that the 1940 WATER simulation outputs generally match observed unregulated low flows from that time period, while performance for regulated flow from the same time period and from 1600, 1900, and 2040 require model input adjustments. Our study will illustrate how increased forest cover could potentially restore in-stream habitat for the endangered dwarf wedgemussel for current and future climate conditions.

Representing macropore flow at the catchment scale: a comparative modeling study

NASA Astrophysics Data System (ADS)

Liu, D.; Li, H. Y.; Tian, F.; Leung, L. R.

2017-12-01

Macropore flow is an important hydrological process that generally enhances the soil infiltration capacity and velocity of subsurface water. Up till now, macropore flow is mostly simulated with high-resolution models. One possible drawback of this modeling approach is the difficulty to effectively represent the overall typology and connectivity of the macropore networks. We hypothesize that modeling macropore flow directly at the catchment scale may be complementary to the existing modeling strategy and offer some new insights. Tsinghua Representative Elementary Watershed model (THREW model) is a semi-distributed hydrology model, where the fundamental building blocks are representative elementary watersheds (REW) linked by the river channel network. In THREW, all the hydrological processes are described with constitutive relationships established directly at the REW level, i.e., catchment scale. In this study, the constitutive relationship of macropore flow drainage is established as part of THREW. The enhanced THREW model is then applied at two catchments with deep soils but distinct climates, the humid Asu catchment in the Amazon River basin, and the arid Wei catchment in the Yellow River basin. The Asu catchment has an area of 12.43km2 with mean annual precipitation of 2442mm. The larger Wei catchment has an area of 24800km2 but with mean annual precipitation of only 512mm. The rainfall-runoff processes are simulated at a hourly time step from 2002 to 2005 in the Asu catchment and from 2001 to 2012 in the Wei catchment. The role of macropore flow on the catchment hydrology will be analyzed comparatively over the Asu and Wei catchments against the observed streamflow, evapotranspiration and other auxiliary data.

Evaluating LSM-Based Water Budgets Over a West African Basin Assisted with a River Routing Scheme

NASA Technical Reports Server (NTRS)

Getirana, Augusto C. V.; Boone, Aaron; Peugeot, Christophe

2014-01-01

Within the framework of the African Monsoon Multidisciplinary Analysis (AMMA) Land Surface Model Intercomparison Project phase 2 (ALMIP-2), this study evaluates the water balance simulated by the Interactions between Soil, Biosphere, and Atmosphere (ISBA) over the upper Oum River basin, in Benin, using a mesoscale river routing scheme (RRS). The RRS is based on the nonlinear Muskingum Cunge method coupled with two linear reservoirs that simulate the time delay of both surface runoff and base flow that are produced by land surface models. On the basis of the evidence of a deep water-table recharge in that region,a reservoir representing the deep-water infiltration (DWI) is introduced. The hydrological processes of the basin are simulated for the 2005-08 AMMA field campaign period during which rainfall and stream flow data were intensively collected over the study area. Optimal RRS parameter sets were determined for three optimization experiments that were performed using daily stream flow at five gauges within the basin. Results demonstrate that the RRS simulates stream flow at all gauges with relative errors varying from -22% to 3% and Nash-Sutcliffe coefficients varying from 0.62 to 0.90. DWI varies from 24% to 67% of the base flow as a function of the sub-basin. The relatively simple reservoir DWI approach is quite robust, and further improvements would likely necessitate more complex solutions (e.g., considering seasonality and soil type in ISBA); thus, such modifications are recommended for future studies. Although the evaluation shows that the simulated stream flows are generally satisfactory, further field investigations are necessary to confirm some of the model assumptions.

Sediment processes modelling below hydraulic mining: towards environmental impact mitigation

NASA Astrophysics Data System (ADS)

Chalov, Sergey R.

2010-05-01

Placer mining sites are located in the river valleys so the rivers are influenced by mining operations. Frequently the existing mining sites are characterized by low contribution to the environmental technologies. Therefore hydraulic mining alters stream hydrology and sediment processes and increases water turbidity. The most serious environmental sequences of the sediment yield increase occur in the rivers populated by salmon fish community because salmon species prefer clean water with low turbidity. For instance, the placer mining in Kamchatka peninsula (Far East of Russia) which is regarded to be the last global gene pool of wild salmon Oncorhynchus threatens the rivers ecosystems. System of man-made impact mitigation could be done through the exact recognition of the human role in hydrological processes and sediment transport especially. Sediment budget of rivers below mining sites is transformed according to the appearance of the man-made non-point and point sediment sources. Non-point source pollution occurs due to soil erosion on the exposed hillsides and erosion in the channel diversions. Slope wash on the hillsides is absent during summer days without rainfalls and is many times increased during rainfalls and snow melting. The nearness of the sources of material and the rivers leads to the small time of suspended load increase after rainfalls. The average time of material intake from exposed hillsides to the rivers is less than 1 hour. The main reason of the incision in the channel diversion is river-channel straightening. The increase of channel slopes and transport capacity leads to the intensive incision of flow. Point source pollution is performed by effluents both from mining site (mainly brief effluents) and from settling ponds (permanent effluents), groundwater seepage from tailing pits or from quarries. High rate of groundwater runoff is the main reason of the technological ponds overfilling. Intensive filtration from channel to ponds because of their nearness determines the water mass increase inside mining site. The predictive models were suggested to assess each of the mane-made processes contribution into the total sediment budget of the rivers below mining sites. The empirical data and theoretical and laboratory-derived correlations were used to obtain the predictive models for each processes of sediment supply. It was challenging to estimate specific erosion rate of washed exposed hillsides, channel incision, water supply conditions. Climatic and anthropogenic changes of water runoff also were simulated to decrease uncertainty of the proposed model. Application of the given approach to the hydraulic platinum-mining located in the Kamchatka peninsula (Koryak plateau, tributaries of the Vivenka River) gave the sediment budget of the placer-mined rivers and the total sediment yield supplied into the ocean from river basin. Polluted placer-mined rivers contribute about 30 % of the whole sediment yield of the Vivenka River. At the same time the catchment area of these rivers is less than 0,03 % from the whole Vivenka catchment area. Based on the sediment transport modeling the decision making system for controlling water pollution and stream community preservation was developed. Due to exposed hillside erosion prevention and settling pond system optimization the total decrease of sediment yield was up to 75 %.

Summer Leeside Rainfall Maxima over the Island of Hawaii

NASA Astrophysics Data System (ADS)

Huang, Y. F.; Chen, Y. L.

2016-12-01

The Kona area on the leeside in the island of Hawaii has distinctive summer rainfall maxima. The primary physical processes for the summer rainfall maxima in Kona are analyzed by comparing it with the winter rainfall. The annual and diurnal cycles there are investigated by employing the Fifth-generation Pennsylvania State University-NCAR Mesoscale Model coupled with the advanced land surface model from June 2004 and February 2010. During the summer, the nocturnal rainfall maximum adjacent to the Kona coast is larger than in winter because of the stronger, moister westerly reversed flow and offshore flow in summer. Comparisons between winter trade-wind days and winter mean show that the leeside Kona rainfall offshore in winter mainly occurs under trade-wind conditions. Moreover, the model results also attest to the impact of moisture content on the Kona leeside rainfall offshore. Comparisons between winter and summer trade-wind days indicate that upslope flows on the Kona slopes are stronger and the moisture content from the westerly reversed flow is higher in summer than in winter. The rainfall maximum on the lower Kona slopes is more pronounced in summer than in winter as a result of enhanced orographic lifting due to stronger upslope flow in the afternoon hours and the moister westerly reversed flow offshore, which merges with the upslope flow inland.

Assessing hydrological changes in a regulated river system over the last 90 years in Rimac Basin (Peru)

NASA Astrophysics Data System (ADS)

Vega-Jácome, Fiorella; Lavado-Casimiro, Waldo Sven; Felipe-Obando, Oscar Gustavo

2018-04-01

Hydrological changes were assessed considering possible changes in precipitation and regulation or hydraulic diversion projects developed in the basin since 1960s in terms of improving water supply of the Rimac River, which is the main source of fresh water of Peru's capital. To achieve this objective, a trend analysis of precipitation and flow series was assessed using the Mann-Kendall test. Subsequently, the Eco-flow and Indicators of Hydrologic Alteration (IHA) methods were applied for the characterization and quantification of the hydrological change in the basin, considering for the analysis, a natural period (1920-1960) and an altered period (1961-2012). Under this focus, daily hydrologic information of the "Chosica R-2" station (from 1920 to 2013) and monthly rainfall information related to 14 stations (from 1964 to 2013) were collected. The results show variations in the flow seasonality of the altered period in relation to the natural period and a significant trend to increase (decrease) minimum flows (maximum flows) during the analyzed period. The Eco-flow assessment shows a predominance of Eco-deficit from December to May (rainy season), strongly related to negative anomalies of precipitation. In addition, a predominance of Eco-surplus was found from June to November (dry season) with a behavior opposite to precipitation, attributed to the regulations and diversion in the basin during that period. In terms of magnitude, the IHA assessment identified an increase of 51% in the average flows during the dry season and a reduction of 10% in the average flows during the rainy season (except December and May). Furthermore, the minimum flows increased by 35% with shorter duration and frequency, and maximum flows decreased by 29% with more frequency but less duration. Although there are benefits of regulation and diversion for developing anthropic activities, the fact that hydrologic alterations may result in significant modifications in the Rimac River ecosystem must be taken into account.

Improving runoff risk estimates: Formulating runoff as a bivariate process using the SCS curve number method

NASA Astrophysics Data System (ADS)

Shaw, Stephen B.; Walter, M. Todd

2009-03-01

The Soil Conservation Service curve number (SCS-CN) method is widely used to predict storm runoff for hydraulic design purposes, such as sizing culverts and detention basins. As traditionally used, the probability of calculated runoff is equated to the probability of the causative rainfall event, an assumption that fails to account for the influence of variations in soil moisture on runoff generation. We propose a modification to the SCS-CN method that explicitly incorporates rainfall return periods and the frequency of different soil moisture states to quantify storm runoff risks. Soil moisture status is assumed to be correlated to stream base flow. Fundamentally, this approach treats runoff as the outcome of a bivariate process instead of dictating a 1:1 relationship between causative rainfall and resulting runoff volumes. Using data from the Fall Creek watershed in western New York and the headwaters of the French Broad River in the mountains of North Carolina, we show that our modified SCS-CN method improves frequency discharge predictions in medium-sized watersheds in the eastern United States in comparison to the traditional application of the method.

Coupled prediction of flood response and debris flow initiation during warm and cold season events in the Southern Appalachians, USA

NASA Astrophysics Data System (ADS)

Tao, J.; Barros, A. P.

2013-07-01

Debris flows associated with rainstorms are a frequent and devastating hazard in the Southern Appalachians in the United States. Whereas warm season events are clearly associated with heavy rainfall intensity, the same cannot be said for the cold season events. Instead, there is a relationship between large (cumulative) rainfall events independently of season, and thus hydrometeorological regime, and debris flows. This suggests that the dynamics of subsurface hydrologic processes play an important role as a trigger mechanism, specifically through soil moisture redistribution by interflow. The first objective of this study is to investigate this hypothesis. The second objective is to assess the physical basis for a regional coupled flood prediction and debris flow warning system. For this purpose, uncalibrated model simulations of well-documented debris flows in headwater catchments of the Southern Appalachians using a 3-D surface-groundwater hydrologic model coupled with slope stability models are examined in detail. Specifically, we focus on two vulnerable headwater catchments that experience frequent debris flows, the Big Creek and the Jonathan Creek in the Upper Pigeon River Basin, North Carolina, and three distinct weather systems: an extremely heavy summertime convective storm in 2011; a persistent winter storm lasting several days; and a severe winter storm in 2009. These events were selected due to the optimal availability of rainfall observations, availability of detailed field surveys of the landslides shortly after they occurred, which can be used to evaluate model predictions, and because they are representative of events that cause major economic losses in the region. The model results substantiate that interflow is a useful prognostic of conditions necessary for the initiation of slope instability, and should therefore be considered explicitly in landslide hazard assessments. Moreover, the relationships between slope stability and interflow are strongly modulated by the topography and catchment specific geomorphologic features that determine subsurface flow convergence zones. The three case-studies demonstrate the value of coupled prediction of flood response and debris flow initiation potential in the context of developing a regional hazard warning system.

Sediment Spews from Connecticut River

NASA Image and Video Library

2017-12-08

NASA image acquired September 2, 2011 To download the full high res go to: earthobservatory.nasa.gov/IOTD/view.php?id=52059 Nearly a week after Hurricane Irene drenched New England with rainfall in late August 2011, the Connecticut River was spewing muddy sediment into Long Island Sound and wrecking the region's farmland just before harvest. The Thematic Mapper on the Landsat 5 satellite acquired this true-color satellite image on September 2, 2011. With its headwaters near the Canadian border, the Connecticut River drains nearly 11,000 square miles (28,500 square kilometers) and receives water from at least 33 tributaries in Vermont, New Hampshire, Massachusetts, and Connecticut. The 410-mile river—New England's longest—enters Long Island Sound near Old Lyme, Connecticut, and is estimated to provide 70 percent of the fresh water entering the Sound. When Irene blew through the region on August 27-28, substantial portions of the Connecticut River watershed received more than 6 to 8 inches (15-20 centimeters) of rainfall, and several locations received more than 10 inches (25 centimeters). Whole towns were cut off from overland transportation—particularly upstream in Vermont, which suffered its worst flooding in 80 years. Thousands of people saw their homes flooded, if not washed off their foundations, at a time of year when rivers are usually at their lowest. Preliminary estimates of river flow at Thompsonville, Connecticut, (not shown in this image) reached 128,000 cubic feet per second (cfs) on August 30, nearly 64 times the usual flow (2,000 cfs) for early fall and the highest flow rate since May 1984. At the mouth of the river—where flow is tidal, and therefore not gauged—the peak water height reached 6.9 feet (2.1 meters) above sea level, almost a foot higher than at any time in the past 10 years. According to Suzanne O'Connell, an environmental scientist working along the Connecticut River at Wesleyan University, the torrent of water coursing through New England picked up silt and clay from the river valleys, giving it the tan color shown in the image above. At Essex, Connecticut, the turbidity (muddiness) of the water was 50 times higher than pre-Irene values. To the east, the Thames River appears to be carrying very little sediment at all on September 2. According to O'Connell, the Thames "drains glaciated terrain, so fine sediment was removed long ago." Most of the land surface in the Thames basin is "just bedrock, till, and glacial erratics." Unlike the Connecticut, areas within the Thames watershed only received 2 to 4 inches of rain in most locations. The flooding that occurred in the aftermath of Hurricane Irene inundated farmland in Massachusetts and Connecticut just before harvest time, the Associated Press noted. Crops were drowned under inches to feet of water. The substantial amounts of soil, sediment, and water deposited on land during the flood could also pose trouble for farmers in coming seasons. "It's notable that whole segments of river bank are just gone," said Andrew Fisk of the Connecticut River Watershed Council. "That's not just loss of sediment. That's land disappearing down river." NASA Earth Observatory image by Robert Simmon, using Landsat 5 data from the U.S. Geological Survey Global Visualization Viewer. Caption by Michael Carlowicz, with interpretation help from Suzanne O'Connell, Wesleyan University, and Andrew Fisk, Connecticut River Watershed Council. Instrument: Landsat 5 - TM Credit: NASA Earth Observatory NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Skiff-based Sonar/LiDAR Survey to Calibrate Reservoir Volumes for Watershed Sediment Yield Studies: Carmel River Example

NASA Astrophysics Data System (ADS)

Smith, D. P.; Kvitek, R.; Quan, S.; Iampietro, P.; Paddock, E.; Richmond, S. F.; Gomez, K.; Aiello, I. W.; Consulo, P.

2009-12-01

Models of watershed sediment yield are complicated by spatial and temporal variability of geologic substrate, land cover, and precipitation parameters. Episodic events such as ENSO cycles and severe wildfire are frequent enough to matter in the long-term average yield, and they can produce short-lived, extreme geomorphic responses. The sediment yield from extreme events is difficult to accurately capture because of the obvious dangers associated with field measurements during flood conditions, but it is critical to include extreme values for developing realistic models of rainfall-sediment yield relations, and for calculating long term average denudation rates. Dammed rivers provide a time-honored natural laboratory for quantifying average annual sediment yield and extreme-event sediment yield. While lead-line surveys of the past provided crude estimates of reservoir sediment trapping, recent advances in geospatial technology now provide unprecedented opportunities to improve volume change measurements. High-precision digital elevation models surveyed on an annual basis, or before-and-after specific rainfall-runoff events can be used to quantify relations between rainfall and sediment yield as a function of landscape parameters, including spatially explicit fire intensity. The Basin-Complex Fire of June and July 2008 resulted in moderate to severe burns in the 114 km^2 portion of the Carmel River watershed above Los Padres Dam. The US Geological Survey produced a debris flow probability/volume model for the region indicating that the reservoir could lose considerable capacity if intense enough precipitation occurred in the 2009-10 winter. Loss of Los Padres reservoir capacity has implications for endangered steelhead and red-legged frogs, and groundwater on municipal water supply. In anticipation of potentially catastrophic erosion, we produced an accurate volume calculation of the Los Padres reservoir in fall 2009, and locally monitored hillslope and fluvial processes during winter months. The pre-runoff reservoir volume was developed by collecting and merging sonar and LiDAR data from a small research skiff equipped with a high-precision positioning and attitude-correcting system. The terrestrial LiDAR data were augmented with shore-based total station positioning. Watershed monitoring included benchmarked serial stream surveys and semi-quantitative assessment of a variety of near-channel colluvial processes. Rainfall in the 2009-10 water year was not intense enough to trigger widespread debris flows of slope failure in the burned watershed, but dry ravel was apparently accelerated. The geomorphic analysis showed that sediment yield was not significantly higher during this low-rainfall year, despite the wide-spread presence of very steep, fire-impacted slopes. Because there was little to no increase in sediment yield this year, we have postponed our second reservoir survey. A predicted ENSO event that might bring very intense rains to the watershed is currently predicted for winter 2009-10.

Physical modelling of rainfall-induced flow failures in loose granular soils

NASA Astrophysics Data System (ADS)

Take, W. A.; Beddoe, R. A.

2015-09-01

The tragic consequences of the March 2014 Oso landslide in Washington, USA were particularly high due to the mobility of the landslide debris. Confusingly, a landslide occurred at that exact same location a number of years earlier, but simply slumped into the river at the toe of the slope. Why did these two events differ so drastically in their mobility? Considerable questions remain regarding the conditions required to generate flow failures in loose soils. Geotechnical centrifuge testing, in combination with high-speed cameras and advanced image analysis has now provided the landslides research community with a powerful new tool to experimentally investigate the complex mechanics leading to high mobility landslides. This paper highlights recent advances in our understanding of the process of static liquefaction in loose granular soil slopes achieved through observations of highly-instrumented physical models. In particular, the paper summarises experimental results aimed to identify the point of initiation of the chain-reaction required to trigger liquefaction flow failures, to assess the effect of slope inclination on the likelihood of a flowslide being triggered, and to quantify the effect of antecedent groundwater levels on the distal reach of landslide debris with the objective of beginning to explain why neighbouring slopes can exhibit such a wide variation in landslide travel distance upon rainfall-triggering.

Reconstruction of Long-Term Discharge Data in a Snow Dominant Region considering Uncertainty in Snow Measurement

NASA Astrophysics Data System (ADS)

Kim, S.

2016-12-01

This study to improve the accuracy of discharge simulation at the head water of the Tone River Basin (Yagisawa Dam Basin; 167 km2 and Naramata Dam Basin; 67 km2), Japan, where the river discharge is governed by the snowmelt and thus much uncertainty was originated in our previous study (Kim et al, 2011). To decrease the uncertainty in our hydrological modeling and simulation, snowmelt amounts are estimated rigorously using an improved degree-day method. The degree-day method, which is the simplest method to estimate snowmelt, is adopted with an improved degree-day factor estimation method. The degree-day factor for the target area is estimated using the observed temperature and the observed river discharge of the snowmelt season. Using long-term observed data, the unique relationship between the degree-day factor and temperature are extracted, and the estimated degree-day factor as a function of temperature is applied for the winter season discharge simulation. Rainfall-runoff simulation for the rest of season is done by the kinematic wave model based on the stage-discharge relationship, considering surface-subsurface flow generation. Finally, long-term (1979-2008) simulation output for the dam inflow is reconstructed and compared with the observed one. ( Kim, S., Tachikawa, Y., Nakakita, E., Yorozu, K. and Shiiba, M. 2011. Climate change impact on river flow of the Tone river basin, Japan, Annual Journal of Hydraulic Engneering, JSCE, 55:S_85-S_90.)

Warm season heavy rainfall events over the Huaihe River Valley and their linkage with wintertime thermal condition of the tropical oceans

NASA Astrophysics Data System (ADS)

Li, Laifang; Li, Wenhong; Tang, Qiuhong; Zhang, Pengfei; Liu, Yimin

2016-01-01

Warm season heavy rainfall events over the Huaihe River Valley (HRV) of China are amongst the top causes of agriculture and economic loss in this region. Thus, there is a pressing need for accurate seasonal prediction of HRV heavy rainfall events. This study improves the seasonal prediction of HRV heavy rainfall by implementing a novel rainfall framework, which overcomes the limitation of traditional probability models and advances the statistical inference on HRV heavy rainfall events. The framework is built on a three-cluster Normal mixture model, whose distribution parameters are sampled using Bayesian inference and Markov Chain Monte Carlo algorithm. The three rainfall clusters reflect probability behaviors of light, moderate, and heavy rainfall, respectively. Our analysis indicates that heavy rainfall events make the largest contribution to the total amount of seasonal precipitation. Furthermore, the interannual variation of summer precipitation is attributable to the variation of heavy rainfall frequency over the HRV. The heavy rainfall frequency, in turn, is influenced by sea surface temperature anomalies (SSTAs) over the north Indian Ocean, equatorial western Pacific, and the tropical Atlantic. The tropical SSTAs modulate the HRV heavy rainfall events by influencing atmospheric circulation favorable for the onset and maintenance of heavy rainfall events. Occurring 5 months prior to the summer season, these tropical SSTAs provide potential sources of prediction skill for heavy rainfall events over the HRV. Using these preceding SSTA signals, we show that the support vector machine algorithm can predict HRV heavy rainfall satisfactorily. The improved prediction skill has important implication for the nation's disaster early warning system.

Identifying fine sediment sources to alleviate flood risk caused by fine sediments through catchment connectivity analysis

NASA Astrophysics Data System (ADS)

Twohig, Sarah; Pattison, Ian; Sander, Graham

2017-04-01

Fine sediment poses a significant threat to UK river systems in terms of vegetation, aquatic habitats and morphology. Deposition of fine sediment onto the river bed reduces channel capacity resulting in decreased volume to contain high flow events. Once the in channel problem has been identified managers are under pressure to sustainably mitigate flood risk. With climate change and land use adaptations increasing future pressures on river catchments it is important to consider the connectivity of fine sediment throughout the river catchment and its influence on channel capacity, particularly in systems experiencing long term aggradation. Fine sediment erosion is a continuing concern in the River Eye, Leicestershire. The predominately rural catchment has a history of flooding within the town of Melton Mowbray. Fine sediment from agricultural fields has been identified as a major contributor of sediment delivery into the channel. Current mitigation measures are not sustainable or successful in preventing the continuum of sediment throughout the catchment. Identifying the potential sources and connections of fine sediment would provide insight into targeted catchment management. 'Sensitive Catchment Integrated Modelling Analysis Platforms' (SCIMAP) is a tool often used by UK catchment managers to identify potential sources and routes of sediment within a catchment. SCIMAP is a risk based model that combines hydrological (rainfall) and geomorphic controls (slope, land cover) to identify the risk of fine sediment being transported from source into the channel. A desktop version of SCIMAP was run for the River Eye at a catchment scale using 5m terrain, rainfall and land cover data. A series of SCIMAP model runs were conducted changing individual parameters to determine the sensitivity of the model. Climate Change prediction data for the catchment was used to identify potential areas of future connectivity and erosion risk for catchment managers. The results have been subjected to field validation as part of a wider research project which provides an indication of the robustness of widespread models as effective management tools.

Modelling Atmospheric Rivers and the Potential for Southeast Texas Flooding: A Case Study of the Maya Express and the March 2016 Sabine River Flood

NASA Astrophysics Data System (ADS)

McIntosh, J.; Lander, K.

2016-12-01

For three days in March of 2016, southeast Texas was inundated with up to 19 inches of rainfall, swelling the Sabine River to record flood stages. This event was attributed to an atmospheric river (AR), regionally known as the "Maya Express," which carried moisture from the Gulf of Mexico into the Sabine River Basin. Studies by the NOAA/NWS Climate Prediction Center have shown that ARs are occurring more frequently due to the intensification of El Niño that increases the available moisture in the atmosphere. In this study, we analyzed the hydrological and meteorological setup of the event on the Sabine River to characterize the flood threat associated with AR rainfall and simulated how an equivalent AR event would impact an urban basin in Houston, Texas. Our primary data sources included WSR-88D radar-based rainfall estimates and observed data at USGS river gauges. Furthermore, the land surface parameters evaluated included land cover, soil types, basin topology, model-derived soil moisture states, and topography. The spatial distribution of precipitation from the storm was then translated west over the Houston and used to force a hydrologic model to assess the impact of an event comparable to the March 2016 event on Houston's San Jacinto River Basin. The results indicate that AR precipitation poses a flood risk to urbanized areas in southeast Texas because of the low lying topography, impervious pavement, and limited flood control. Due to this hydrologic setup, intense AR rainfall can yield a rapid urban runoff response that overwhelms the river system, potentially endangering the lives and property of millions of people in the Houston area. Ultimately, if the frequency of AR development increases, regional flood potential may increase. Given the consequences established in this study, more research should be conducted in order to better predict the rate of recurrence and effects of Maya Express generated precipitation.

CREST v2.1 Refined by a Distributed Linear Reservoir Routing Scheme

NASA Astrophysics Data System (ADS)

Shen, X.; Hong, Y.; Zhang, K.; Hao, Z.; Wang, D.

2014-12-01

Hydrologic modeling is important in water resources management, and flooding disaster warning and management. Routing scheme is among the most important components of a hydrologic model. In this study, we replace the lumped LRR (linear reservoir routing) scheme used in previous versions of the distributed hydrological model, CREST (coupled routing and excess storage) by a newly proposed distributed LRR method, which is theoretically more suitable for distributed hydrological models. Consequently, we have effectively solved the problems of: 1) low values of channel flow in daily simulation, 2) discontinuous flow value along the river network during flood events and 3) irrational model parameters. The CREST model equipped with both the routing schemes have been tested in the Gan River basin. The distributed LRR scheme has been confirmed to outperform the lumped counterpart by two comparisons, hydrograph validation and visual speculation of the continuity of stream flow along the river: 1) The CREST v2.1 (version 2.1) with the implementation of the distributed LRR achieved excellent result of [NSCE(Nash coefficient), CC (correlation coefficient), bias] =[0.897, 0.947 -1.57%] while the original CREST v2.0 produced only negative NSCE, close to zero CC and large bias. 2) CREST v2.1 produced more naturally smooth river flow pattern along the river network while v2.0 simulated bumping and discontinuous discharge along the mainstream. Moreover, we further observe that by using the distributed LRR method, 1) all model parameters fell within their reasonable region after an automatic optimization; 2) CREST forced by satellite-based precipitation and PET products produces a reasonably well result, i.e., (NSCE, CC, bias) = (0.756, 0.871, -0.669%) in the case study, although there is still room to improve regarding their low spatial resolution and underestimation of the heavy rainfall events in the satellite products.

Characteristics and seasonal variation of hydrochemistry in the Tangra Yumco basin, central Tibetan Plateau, and its response to Indian summer monsoon

NASA Astrophysics Data System (ADS)

Wang, Junbo; Qiao, Baojin; Huang, Lei; Zhu, Liping

2016-04-01

Lake Tangra Yumco, located in central Tibetan Plateau, is the deepest lake recorded on the Plateau with a maximum water depth of 230m. Several studies have been conducted focused on paleoenvironmental changes utilizing lake sediemts cores and high lake terraces. The results revealed a significant lake level decreasing up to 180m from early Holocene and Tangra Yumco was separated from two other adjacent lakes since then. A high resolution continuous lake sediment record covering the past 17.4 cal ka has been established. However, compared with the high lake level and paleoenvironmental studies, modern investigations on the water in this basin are still lack. A comprehensive investigation of hydrochemistry is helpful to understand the modern environment and its response to climate change. This study focuses on the characteristics, seasonal variation and controlling mechanism of hydrochemistry in Tangra Yumco basin, including lake water, river water and rainfall water. Lake water, river water and rainfall water were collected for analyzing major ionic composition in Tangra Yumco basin during 2013-2014. The results showed that Na+ is the major cation of lake water; Ca2+ is the major cation of river and rainfall water, whereas the major anion of all samples is HCO3-. Comparison of the concentration of calcium in river water, lake water and surface sediments reveals a significant carbonate precipitation process within the lake. The chemical composition of lake is mainly controlled by evaporation and crystallization, whereas river water and rainfall water are mainly controlled by carbonate weathering. Among all rivers, DR10 and DR1 locate in the north and west part of Tangra Yumco where dense local populations live nearby show the highest and second highest total dissolved solid (TDS) with a small catchment and a high content of SO42-, indicating that anthropogenic input and planting have likely a strong influence on chemical compositions of both rivers. The TDS of lake water and river water is much higher during Indian summer monsoon (ISM) period than the pre-monsoon period. The TDS concentration of lake water shows a rapid increase from early August and reaches 2.5 times of pre-monsoon period within one month indicating that due to the rise of temperature and increase of rainfall, rock weathering is enhanced, thus the runoff could take much more chemical composition into the river and the lake. During the post-monsoon period, the TDS of lake water is still keeping in a high level as in monsoon period, probably resulting from the balance between concentration of ions due to lake water loss and decrease of terrestrial ion input. K+ and Cl- of rainfall may originate from evaporation of lake water and mineral aerosols, and the dissolved carbonates are responsible for the chemical composition of rainfall water.

Isotopic values of the Amazon headwaters in Peru: comparison of the wet upper Río Madre de Dios watershed with the dry Urubamba-Apurimac river system.

PubMed

Lambs, L; Horwath, A; Otto, T; Julien, F; Antoine, P-O

2012-04-15

The Amazon River is a huge network of long tributaries, and little is known about the headwaters. Here we present a study of one wet tropical Amazon forest side, and one dry and cold Atiplano plateau, originating from the same cordillera. The aim is to see how this difference affects the water characteristics. Different kind of water (spring, lake, river, rainfall) were sampled to determine their stable isotopes ratios (oxygen 18/16 and hydrogen 2/1) by continuous flow isotope ratio mass spectrometry (IRMS). These ratios coupled with chemical analysis enabled us to determine the origin of the water, the evaporation process and the water recycling over the Amazon plain forest and montane cloud forest. Our study shows that the water flowing in the upper Madre de Dios basin comes mainly from the foothill humid forest, with a characteristic water recycling process signature, and not from higher glacier melt. On the contrary, the water flowing in the Altiplano Rivers is mainly from glacier melts, with a high evaporation process. This snow and glacier are fed mainly by Atlantic moisture which transits over the large Amazon forest. The Atlantic moisture and its recycling over this huge tropical forest display a progressive isotopic gradient, as a function of distance from the ocean. At the level of the montane cloud forest and on the altiplano, respectively, additional water recycling and evaporation occur, but they are insignificant in the total water discharge. Copyright © 2012 John Wiley & Sons, Ltd.

Contribution of piezometric measurement on knowledge and management of low water levels

NASA Astrophysics Data System (ADS)

Bessiere, Hélène; Stollsteiner, Philippe; Allier, Delphine; Nicolas, Jérôme; Gourcy, Laurence

2014-05-01

This article is based on a BRGM study on piezometric indicators, threshold values of discharges and groundwater levels for the assessment of potentially pumpable volumes of chalky watersheds. A method for estimating low water levels from groundwater levels is presented from three examples of chalk aquifer; the first one is located in Picardy and the two other in the Champagne Ardennes region. Piezometers with "annual" cycles, used in these examples, are supposed to be representative of the aquifer hydrodynamics. The analysis leads to relatively precise and satisfactory relationships between groundwater levels and observed discharges for this chalky context. These relationships may be useful for monitoring, validation, extension or reconstruction of the low water flow. On the one hand, they allow defining the piezometric levels corresponding to the different alert thresholds of river discharges. On the other hand, they clarify the distribution of low water flow from runoff or the draining of the aquifer. Finally, these correlations give an assessment of the minimum flow for the coming weeks using of the rate of draining of the aquifer. Nevertheless the use of these correlations does not allow to optimize the value of pumpable volumes because it seems to be difficult to integrate the amount of the effective rainfall that may occur during the draining period. In addition, these relationships cannot be exploited for multi-annual cycle systems. In these cases, the solution seems to lie on the realization of a rainfall-runoff-piezometric level model. Therefore, two possibilities are possible. The first one is to achieve each year, on a given date, a forecast for the days or months to come with various frequential distributions rainfalls. However, the forecast must be reiterated each year depending on climatic conditions. The principle of the second method is to simulate forecasts for different rainfall intensities and following different initial conditions. The results are presented in chart form. In addition, this last method is currently tested for the problem of floods by groundwater level rise.

Drought analysis in the Tons River Basin, India during 1969-2008

NASA Astrophysics Data System (ADS)

Meshram, Sarita Gajbhiye; Gautam, Randhir; Kahya, Ercan

2018-05-01

The primary focus of this study is the analysis of droughts in the Tons River Basin during the period 1969-2008. Precipitation data observed at four gauging stations are used to identify drought over the study area. The event of drought is derived from the standardized precipitation index (SPI) on a 3-month scale. Our results indicated that severe drought occurred in the Allahabad, Rewa, and Satna stations in the years 1973 and 1979. The droughts in this region had occurred mainly due to erratic behavior in monsoons, especially due to long breaks between monsoons. During the drought years, the deficiency of the annual rainfall in the analysis of annual rainfall departure had varied from -26% in 1976 to -60% in 1973 at Allahabad station in the basin. The maximum deficiency of annual and seasonal rainfall recorded in the basin is 60%. The maximum seasonal rainfall departure observed in the basin is in the order of -60% at Allahabad station in 1973, while maximum annual rainfall departure had been recorded as -60% during 1979 at the Satna station. Extreme dry events ( z score <-2) were detected during July, August, and September. Moreover, severe dry events were observed in August, September, and October. The drought conditions in the Tons River Basin are dominantly driven by total rainfall throughout the period between June and November.

Causes and Model Skill of the Persistent Intense Rainfall and Flooding in Paraguay during the Austral Summer 2015-2016

NASA Astrophysics Data System (ADS)

Doss-Gollin, J.; Munoz, A. G.; Pastén, M.

2017-12-01

During the austral summer 2015-16 severe flooding displaced over 150,000 people on the Paraguay River system in Paraguay, Argentina, and Southern Brazil. This flooding was out of phase with the typical seasonal cycle of the Paraguay River, and was driven by repeated intense rainfall events in the Lower Paraguay River basin. Using a weather typing approach within a diagnostic framework, we show that enhanced moisture inflow from the low-level jet and local convergence associated with baroclinic systems favored the development of mesoscale convective activity and enhanced precipitation. The observed circulation patterns were made more likely by the cross-timescale interactions of multiple climate mechanisms including the strong, mature El Niño event and an active Madden-Julien Oscillation in phases four and five. We also perform a comparison of the rainfall predictability using seasonal forecasts from the Latin American Observatory of Climate Events (OLE2) and sub-seasonal forecasts produced by the ECMWF. We find that the model output precipitation field exhibited limited skill at lead times beyond the synoptic timescale, but that a Model Output Statistics (MOS) approach, in which the leading principal components of the observed rainfall field are regressed on the leading principal components of model-simulated rainfall fields, substantially improves spatial representation of rainfall forecasts. Possible implications for flood preparedness are briefly discussed.

Tracking the evolution of stream DOM source during storm events using end member mixing analysis based on DOM quality

NASA Astrophysics Data System (ADS)

Yang, Liyang; Chang, Soon-Woong; Shin, Hyun-Sang; Hur, Jin

2015-04-01

The source of river dissolved organic matter (DOM) during storm events has not been well constrained, which is critical in determining the quality and reactivity of DOM. This study assessed temporal changes in the contributions of four end members (weeds, leaf litter, soil, and groundwater), which exist in a small forested watershed (the Ehwa Brook, South Korea), to the stream DOM during two storm events, using end member mixing analysis (EMMA) based on spectroscopic properties of DOM. The instantaneous export fluxes of dissolved organic carbon (DOC), chromophoric DOM (CDOM), and fluorescent components were all enhanced during peak flows. The DOC concentration increased with the flow rate, while CDOM and humic-like fluorescent components were diluted around the peak flows. Leaf litter was dominant for the DOM source in event 2 with a higher rainfall, although there were temporal variations in the contributions of the four end members to the stream DOM for both events. The contribution of leaf litter peaked while that of deeper soils decreased to minima at peak flows. Our results demonstrated that EMMA based on DOM properties could be used to trace the DOM source, which is of fundamental importance for understanding the factors responsible for river DOM dynamics during storm events.

Uncertainty in surface water flood risk modelling

NASA Astrophysics Data System (ADS)

Butler, J. B.; Martin, D. N.; Roberts, E.; Domuah, R.

2009-04-01

Two thirds of the flooding that occurred in the UK during summer 2007 was as a result of surface water (otherwise known as ‘pluvial') rather than river or coastal flooding. In response, the Environment Agency and Interim Pitt Reviews have highlighted the need for surface water risk mapping and warning tools to identify, and prepare for, flooding induced by heavy rainfall events. This need is compounded by the likely increase in rainfall intensities due to climate change. The Association of British Insurers has called for the Environment Agency to commission nationwide flood risk maps showing the relative risk of flooding from all sources. At the wider European scale, the recently-published EC Directive on the assessment and management of flood risks will require Member States to evaluate, map and model flood risk from a variety of sources. As such, there is now a clear and immediate requirement for the development of techniques for assessing and managing surface water flood risk across large areas. This paper describes an approach for integrating rainfall, drainage network and high-resolution topographic data using Flowroute™, a high-resolution flood mapping and modelling platform, to produce deterministic surface water flood risk maps. Information is provided from UK case studies to enable assessment and validation of modelled results using historical flood information and insurance claims data. Flowroute was co-developed with flood scientists at Cambridge University specifically to simulate river dynamics and floodplain inundation in complex, congested urban areas in a highly computationally efficient manner. It utilises high-resolution topographic information to route flows around individual buildings so as to enable the prediction of flood depths, extents, durations and velocities. As such, the model forms an ideal platform for the development of surface water flood risk modelling and mapping capabilities. The 2-dimensional component of Flowroute employs uniform flow formulae (Manning's Equation) to direct flow over the model domain, sourcing water from the channel or sea so as to provide a detailed representation of river and coastal flood risk. The initial development step was to include spatially-distributed rainfall as a new source term within the model domain. This required optimisation to improve computational efficiency, given the ubiquity of ‘wet' cells early on in the simulation. Collaboration with UK water companies has provided detailed drainage information, and from this a simplified representation of the drainage system has been included in the model via the inclusion of sinks and sources of water from the drainage network. This approach has clear advantages relative to a fully coupled method both in terms of reduced input data requirements and computational overhead. Further, given the difficulties associated with obtaining drainage information over large areas, tests were conducted to evaluate uncertainties associated with excluding drainage information and the impact that this has upon flood model predictions. This information can be used, for example, to inform insurance underwriting strategies and loss estimation as well as for emergency response and planning purposes. The Flowroute surface-water flood risk platform enables efficient mapping of areas sensitive to flooding from high-intensity rainfall events due to topography and drainage infrastructure. As such, the technology has widespread potential for use as a risk mapping tool by the UK Environment Agency, European Member States, water authorities, local governments and the insurance industry. Keywords: Surface water flooding, Model Uncertainty, Insurance Underwriting, Flood inundation modelling, Risk mapping.

Hybrid Forecasting of Daily River Discharges Considering Autoregressive Heteroscedasticity

NASA Astrophysics Data System (ADS)

Szolgayová, Elena Peksová; Danačová, Michaela; Komorniková, Magda; Szolgay, Ján

2017-06-01

It is widely acknowledged that in the hydrological and meteorological communities, there is a continuing need to improve the quality of quantitative rainfall and river flow forecasts. A hybrid (combined deterministic-stochastic) modelling approach is proposed here that combines the advantages offered by modelling the system dynamics with a deterministic model and a deterministic forecasting error series with a data-driven model in parallel. Since the processes to be modelled are generally nonlinear and the model error series may exhibit nonstationarity and heteroscedasticity, GARCH-type nonlinear time series models are considered here. The fitting, forecasting and simulation performance of such models have to be explored on a case-by-case basis. The goal of this paper is to test and develop an appropriate methodology for model fitting and forecasting applicable for daily river discharge forecast error data from the GARCH family of time series models. We concentrated on verifying whether the use of a GARCH-type model is suitable for modelling and forecasting a hydrological model error time series on the Hron and Morava Rivers in Slovakia. For this purpose we verified the presence of heteroscedasticity in the simulation error series of the KLN multilinear flow routing model; then we fitted the GARCH-type models to the data and compared their fit with that of an ARMA - type model. We produced one-stepahead forecasts from the fitted models and again provided comparisons of the model's performance.

Risk analysis for the flood control capacity of dikes under climate change

NASA Astrophysics Data System (ADS)

Wei, Hsiao Ping; Yeh, Keh-Chia; Hsiao, Yi-Hua

2017-04-01

Climate change is the major reason for many extreme disaster events. In recent years, scientists have revealed many findings and most of them agree that the frequency of extreme weather and its corresponding hydrological impact will increase due to climate change. In such situation, the current hydrologic designs based upon historical observation, which could be changed, are necessary to review again under the scenario of climate change. It is for this reason that this study uses Kao-Ping River Basin as an example, using high resolution dynamical downscaling data (base period, near future, and end of the century) to simulate changes in hourly flow rate of typhoon events in each of the three 25-year periods. Results are further compared with the design flow rate announced by the competent authority of water resources, as well as recorded river water levels of the most severe typhoon event in history and risk analysis basic on factors, to evaluate the risk and impact of river flooding under climate change.From the simulation results, the frequency of exceeding design discharge in Kao-ping river catchment will increase in the end of century. The water level at these LI-LIN BRIDGE and SAN-TI-MEN gauges could be obviously influenced due to the extreme rainfall events, so that their flood control capacity should be assessed and improved.

Small hydropower spot prediction using SWAT and a diversion algorithm, case study: Upper Citarum Basin

NASA Astrophysics Data System (ADS)

Kardhana, Hadi; Arya, Doni Khaira; Hadihardaja, Iwan K.; Widyaningtyas, Riawan, Edi; Lubis, Atika

2017-11-01

Small-Scale Hydropower (SHP) had been important electric energy power source in Indonesia. Indonesia is vast countries, consists of more than 17.000 islands. It has large fresh water resource about 3 m of rainfall and 2 m of runoff. Much of its topography is mountainous, remote but abundant with potential energy. Millions of people do not have sufficient access to electricity, some live in the remote places. Recently, SHP development was encouraged for energy supply of the places. Development of global hydrology data provides opportunity to predict distribution of hydropower potential. In this paper, we demonstrate run-of-river type SHP spot prediction tool using SWAT and a river diversion algorithm. The use of Soil and Water Assessment Tool (SWAT) with input of CFSR (Climate Forecast System Re-analysis) of 10 years period had been implemented to predict spatially distributed flow cumulative distribution function (CDF). A simple algorithm to maximize potential head of a location by a river diversion expressing head race and penstock had been applied. Firm flow and power of the SHP were estimated from the CDF and the algorithm. The tool applied to Upper Citarum River Basin and three out of four existing hydropower locations had been well predicted. The result implies that this tool is able to support acceleration of SHP development at earlier phase.

Scaling of peak flows with constant flow velocity in random self-similar networks

USGS Publications Warehouse

Troutman, Brent M.; Mantilla, Ricardo; Gupta, Vijay K.

2011-01-01

A methodology is presented to understand the role of the statistical self-similar topology of real river networks on scaling, or power law, in peak flows for rainfall-runoff events. We created Monte Carlo generated sets of ensembles of 1000 random self-similar networks (RSNs) with geometrically distributed interior and exterior generators having parameters pi and pe, respectively. The parameter values were chosen to replicate the observed topology of real river networks. We calculated flow hydrographs in each of these networks by numerically solving the link-based mass and momentum conservation equation under the assumption of constant flow velocity. From these simulated RSNs and hydrographs, the scaling exponents β and φ characterizing power laws with respect to drainage area, and corresponding to the width functions and flow hydrographs respectively, were estimated. We found that, in general, φ > β, which supports a similar finding first reported for simulations in the river network of the Walnut Gulch basin, Arizona. Theoretical estimation of β and φ in RSNs is a complex open problem. Therefore, using results for a simpler problem associated with the expected width function and expected hydrograph for an ensemble of RSNs, we give heuristic arguments for theoretical derivations of the scaling exponents β(E) and φ(E) that depend on the Horton ratios for stream lengths and areas. These ratios in turn have a known dependence on the parameters of the geometric distributions of RSN generators. Good agreement was found between the analytically conjectured values of β(E) and φ(E) and the values estimated by the simulated ensembles of RSNs and hydrographs. The independence of the scaling exponents φ(E) and φ with respect to the value of flow velocity and runoff intensity implies an interesting connection between unit hydrograph theory and flow dynamics. Our results provide a reference framework to study scaling exponents under more complex scenarios of flow dynamics and runoff generation processes using ensembles of RSNs.

Increasing trends in rainfall-runoff erosivity in the Source Region of the Three Rivers, 1961-2012.

PubMed

Wang, Yousheng; Cheng, Congcong; Xie, Yun; Liu, Baoyuan; Yin, Shuiqing; Liu, Yingna; Hao, Yanfang

2017-08-15

As the head source of the two longest rivers in China and the longest river in Southeast Asia, the East Qinghai-Tibetan Plateau (QTP) is experiencing increasing thaw snowmelt and more heavy precipitation events under global warming, which might lead to soil erosion risk. To understand the potential driving force of soil erosion and its relationship with precipitation in the context of climate change, this study analyzed long-term variations in annual rainfall-runoff erosivity, a climatic index of soil erosion, by using the Mann-Kendall statistical test and Theil and Sen's approach in the Source Region of the Three Rivers during 1961-2012. The results showed the followings: (i) increasing annual rainfall-runoff erosivity was observed over the past 52years, with a mean relative trend index (RT 1 ) value of 12.1%. The increasing trend was more obvious for the latest two decades: RT 1 was nearly three times larger than that over the entire period; (ii) more precipitation events and a higher precipitation amount were the major forces for the increasing rainfall-runoff erosivity; (iii) similar rising trends in sediment yields, which corresponded to rainfall-runoff erosivity under slightly increasing vegetation coverage in the study area, implied a large contribution of rainfall-runoff erosivity to the increasing sediment yields; and (iv) high warming rates increased the risk of soil destruction, soil erosion and sediment yields. Conservation measures, such as enclosing grassland, returning grazing land to grassland and rotation grazing since the 1980s, have maintained vegetation coverage and should be continued and strengthened. Copyright © 2017 Elsevier B.V. All rights reserved.

DEFORESTATION AND LANDSLIDES IN YUNNAN, CHINA.

USGS Publications Warehouse

Wieczorek, Gerald F.; Wu, Jishan; Li, Tianchi

1987-01-01

Landslides historically have caused severe erosion problems in the Xiao River drainage region of northeastern Yunnan Province, China, that hence resulted in serious economic and social consequences. Owing to monsoonal storms of high rainfall intensity, the erosion potential is high in this mountainous, seismically active region. Landslides transported large quantities of materials into the ravines. During intense storms, high runoff from the deforested areas has mobilized this material into debris flows. Where these flows emerged onto flatter slopes in the lower parts of the watersheds, the channels were too small to hold them, so farmland and villages were inundated. Debris flows in this region during June-August 1985 killed 12 people, damaged roads and the main rail line to Kunming, the capital of Yunnan Province, inundated farmland, and overflowed debris-retention structures. To mitigate these severe erosion problems, several different methods have been used.

Modeling and evaluation of compliance to water quality regulations in bathing areas on the Daoulas catchment and estuary (France).

PubMed

Bougeard, M; Le Saux, J C; Jouan, M; Durand, G; Pommepuy, M

2010-01-01

The microbiological quality of waters in estuaries determines their acceptability for recreational uses. Microbiological contamination often results from urban wastewater discharges or non-point source pollution (manure spreading), and can cause bathing zones to be closed. European regulations (EC/7/2006) have proposed standards (500 E. coli/100 ml) for the acceptability areas for bathing. In this study, two models were associated to simulate contamination: SWAT on a catchment and MARS 2D in the downstream estuary. After river flow calibration and validation, two scenarios were simulated in SWAT, and E. coli fluxes obtained at the main outlet of the catchment were then introduced into MARS 2D to follow E. coli concentrations in the estuary. An annual evaluation of compliance to bathing area water quality standards was then calculated, linked with daily rainfall classes. Water quality in the estuary was below the standard on 13 days, including 5 days with rainfall superior to 10 mm, due to faecal contamination from soil leaching by rain, and 5 days with rainfall ranging from 0.1 to 5 mm/day, due to the high frequency of this level of rainfall. To conclude, this study allowed us to demonstrate the efficiency of models to gain a better understanding on water quality degradation factors.

Prediction of spatially explicit rainfall intensity–duration thresholds for post-fire debris-flow generation in the western United States

USGS Publications Warehouse

Staley, Dennis M.; Negri, Jacquelyn; Kean, Jason W.; Laber, Jayme L.; Tillery, Anne C.; Youberg, Ann M.

2017-01-01

Early warning of post-fire debris-flow occurrence during intense rainfall has traditionally relied upon a library of regionally specific empirical rainfall intensity–duration thresholds. Development of this library and the calculation of rainfall intensity-duration thresholds often require several years of monitoring local rainfall and hydrologic response to rainstorms, a time-consuming approach where results are often only applicable to the specific region where data were collected. Here, we present a new, fully predictive approach that utilizes rainfall, hydrologic response, and readily available geospatial data to predict rainfall intensity–duration thresholds for debris-flow generation in recently burned locations in the western United States. Unlike the traditional approach to defining regional thresholds from historical data, the proposed methodology permits the direct calculation of rainfall intensity–duration thresholds for areas where no such data exist. The thresholds calculated by this method are demonstrated to provide predictions that are of similar accuracy, and in some cases outperform, previously published regional intensity–duration thresholds. The method also provides improved predictions of debris-flow likelihood, which can be incorporated into existing approaches for post-fire debris-flow hazard assessment. Our results also provide guidance for the operational expansion of post-fire debris-flow early warning systems in areas where empirically defined regional rainfall intensity–duration thresholds do not currently exist.

Prediction of spatially explicit rainfall intensity-duration thresholds for post-fire debris-flow generation in the western United States

NASA Astrophysics Data System (ADS)

Staley, Dennis M.; Negri, Jacquelyn A.; Kean, Jason W.; Laber, Jayme L.; Tillery, Anne C.; Youberg, Ann M.

2017-02-01

Early warning of post-fire debris-flow occurrence during intense rainfall has traditionally relied upon a library of regionally specific empirical rainfall intensity-duration thresholds. Development of this library and the calculation of rainfall intensity-duration thresholds often require several years of monitoring local rainfall and hydrologic response to rainstorms, a time-consuming approach where results are often only applicable to the specific region where data were collected. Here, we present a new, fully predictive approach that utilizes rainfall, hydrologic response, and readily available geospatial data to predict rainfall intensity-duration thresholds for debris-flow generation in recently burned locations in the western United States. Unlike the traditional approach to defining regional thresholds from historical data, the proposed methodology permits the direct calculation of rainfall intensity-duration thresholds for areas where no such data exist. The thresholds calculated by this method are demonstrated to provide predictions that are of similar accuracy, and in some cases outperform, previously published regional intensity-duration thresholds. The method also provides improved predictions of debris-flow likelihood, which can be incorporated into existing approaches for post-fire debris-flow hazard assessment. Our results also provide guidance for the operational expansion of post-fire debris-flow early warning systems in areas where empirically defined regional rainfall intensity-duration thresholds do not currently exist.

Flow and habitat effects on juvenile fish abundance in natural and altered flow regimes

USGS Publications Warehouse

Freeman, Mary C.; Bowen, Z.H.; Bovee, K.D.; Irwin, E.R.

2001-01-01

Conserving biological resources native to large river systems increasingly depends on how flow-regulated segments of these rivers are managed. Improving management will require a better understanding of linkages between river biota and temporal variability of flow and instream habitat. However, few studies have quantified responses of native fish populations to multiyear (>2 yr) patterns of hydrologic or habitat variability in flow-regulated systems. To provide these data, we quantified young-of-year (YOY) fish abundance during four years in relation to hydrologic and habitat variability in two segments of the Tallapoosa River in the southeastern United States. One segment had an unregulated flow regime, whereas the other was flow-regulated by a peak-load generating hydropower dam. We sampled fishes annually and explored how continuously recorded flow data and physical habitat simulation models (PHABSIM) for spring (April-June) and summer (July-August) preceding each sample explained fish abundances. Patterns of YOY abundance in relation to habitat availability (median area) and habitat persistence (longest period with habitat area continuously above the long-term median area) differed between unregulated and flow-regulated sites. At the unregulated site, YOY abundances were most frequently correlated with availability of shallow-slow habitat in summer (10 species) and persistence of shallow-slow and shallow-fast habitat in spring (nine species). Additionally, abundances were negatively correlated with 1-h maximum flow in summer (five species). At the flow-regulated site, YOY abundances were more frequently correlated with persistence of shallow-water habitats (four species in spring; six species in summer) than with habitat availability or magnitude of flow extremes. The associations of YOY with habitat persistence at the flow-regulated site corresponded to the effects of flow regulation on habitat patterns. Flow regulation reduced median flows during spring and summer, which resulted in median availability of shallow-water habitats comparable to the unregulated site. However, habitat persistence was severely reduced by flow fluctuations resulting from pulsed water releases for peak-load power generation. Habitat persistence, comparable to levels in the unregulated site, only occurred during summer when low rainfall or other factors occasionally curtailed power generation. As a consequence, summer-spawning species numerically dominated the fish assemblage at the flow-regulated site; five of six spring-spawning species occurring at both study sites were significantly less abundant at the flow-regulated site. Persistence of native fishes in flow-regulated systems depends, in part, on the seasonal occurrence of stable habitat conditions that facilitate reproduction and YOY survival.

Support vector machine-an alternative to artificial neuron network for water quality forecasting in an agricultural nonpoint source polluted river?

PubMed

Liu, Mei; Lu, Jun

2014-09-01

Water quality forecasting in agricultural drainage river basins is difficult because of the complicated nonpoint source (NPS) pollution transport processes and river self-purification processes involved in highly nonlinear problems. Artificial neural network (ANN) and support vector model (SVM) were developed to predict total nitrogen (TN) and total phosphorus (TP) concentrations for any location of the river polluted by agricultural NPS pollution in eastern China. River flow, water temperature, flow travel time, rainfall, dissolved oxygen, and upstream TN or TP concentrations were selected as initial inputs of the two models. Monthly, bimonthly, and trimonthly datasets were selected to train the two models, respectively, and the same monthly dataset which had not been used for training was chosen to test the models in order to compare their generalization performance. Trial and error analysis and genetic algorisms (GA) were employed to optimize the parameters of ANN and SVM models, respectively. The results indicated that the proposed SVM models performed better generalization ability due to avoiding the occurrence of overtraining and optimizing fewer parameters based on structural risk minimization (SRM) principle. Furthermore, both TN and TP SVM models trained by trimonthly datasets achieved greater forecasting accuracy than corresponding ANN models. Thus, SVM models will be a powerful alternative method because it is an efficient and economic tool to accurately predict water quality with low risk. The sensitivity analyses of two models indicated that decreasing upstream input concentrations during the dry season and NPS emission along the reach during average or flood season should be an effective way to improve Changle River water quality. If the necessary water quality and hydrology data and even trimonthly data are available, the SVM methodology developed here can easily be applied to other NPS-polluted rivers.

The impact of snowpack decline on high elevation surface-water flow in the Willamette River: a stable isotope perspective

NASA Astrophysics Data System (ADS)

Brooks, J. R.; Johnson, H.; Cline, S. P.; Rugh, W.

2015-12-01

Much of the water that people in Western Oregon rely on comes from the snowpack in the Cascade Range, and this snowpack is expected to decrease in coming years with climate change. In fact, the past five years have shown dramatic variation in snowpack from a high of 174% of normal in 2010-11 to a low of 11% for 2014-15, one of the lowest on record. During this timeframe, we have monitored the stable isotopes of water within the Willamette River twice monthly, and mapped the spatial variation of water isotopes across the basin. Within the Willamette Basin, stable isotopes of water in precipitation vary strongly with elevation and provide a marker for determining the mean elevation from which water in the Willamette River is derived. In the winter when snow accumulates in the mountains, low elevation precipitation (primarily rain) contributes the largest proportion of water to the Willamette River. During summer when rainfall is scarce and demand for water is the greatest, water in the Willamette River is mainly derived from high elevation snowmelt. Our data indicate that the proportion of water from high elevation decreased with decreasing snowpack. We combine this information with the river flow data to estimate the volume reduction related to snow pack reduction during the dry summer. Observed reductions in the contribution of high elevation water to the Willamette River after just two years of diminished snowpack indicate that the hydrologic system responds relatively rapidly to changing snowpack volume. Reconciling the demands between human use and biological instream requirements during summer will be challenging under climatic conditions in which winter snowpack is reduced compared to historical amounts.

An ECOMAG-based Regional Hydrological Model for the Mackenzie River basin

NASA Astrophysics Data System (ADS)

Motovilov, Yury; Kalugin, Andrey; Gelfan, Alexander

2017-04-01

A physically-based distributed model of runoff generation has been developed for the Mackenzie River basin (the catchment area is 1 660 000 km2). The model is based on the ECOMAG (ECOlogical Model for Applied Geophysics) hydrological modeling platform and describes processes of interception of rainfall/snowfall by the canopy, snow accumulation and melt, soil freezing and thawing, water infiltration into unfrozen and frozen soil, evapotranspiration, thermal and water regime of soil, overland, subsurface and ground flow, flow routing through a channel network accounting for flow regulation by lakes and reservoirs. The governing model's equations are derived from integration of the basic hydro- and thermodynamics equations of water and heat vertical transfer in snowpack, frozen/unfrozen soil, horizontal water flow under and over catchment slopes, etc. The Mackenzie basin's schematization was performed on the basis of the global DEM data (1-km resolution) from the HYDRO1K database of the U.S. Geological Survey. Most of the model parameters are physically meaningful and derived through the global datasets of the basin characteristics: FAO/IIASA Harmonized World Soil Database, USGS EROS Global Land Cover Characteristics project, etc. The 0.5ox0.5o WATCH reanalysis daily precipitation, air temperature and air humidity data were used as the model input for the period of 1971-2002. The daily discharge data provided by the Water Survey of Canada for 10 streamflow gauges, which are located at the Mackenzie River and the main tributaries (Peel River, Great Bear River, Liard River, Slave River and Athabasca River), were used for calibration (1991-2001) and validation (1971-1990) of the model. The gauges' catchment areas vary from 70600 km2 (Peel River above Fort Mopherson) to 1 660 000 km2 (Mackenzie River at Arctic Red River). The model demonstrated satisfactory performance in terms of Nash-and Sutcliffe efficiency (NSE(daily)0.60 and NSE(monthly)0.70) and percent bias (PBIAS15%) for 8 gauges of 10. Weaker results were obtained for Great Bear River at outlet of Great Bear Lake and Peace River at Peace Point. Possibilities of a model approach for the construction of mean annual hydrological fields (maps) using meteorological data for the large river basins are shown. Spatial fields of the 32-year mean annual runoff and evaporation (1971-2002) for the Mackenzie River basin were simulated by the distributed model and the corresponding maps were compared with that provided by Hydrological Atlas of Canada (1972) for 30-year period (1941-1970). Analysis of fields conformity is made and possible sources of errors are discussed.

Deep nitrogen acquisition in warming permafrost soils: Contributions of belowground plant traits and fungal symbioses in the permafrost carbon feedback to climate

NASA Astrophysics Data System (ADS)

Hartnett, H. E.; Palta, M. M.; Grimm, N. B.; Ruhi, A.; van Shaijik, M.

2016-12-01

Tempe Town Lake (TTL) is a hydrologically-regulated reservoir in Tempe, Arizona. The lake has high primary production and receives dissolved organic carbon (DOC) from rainfall, storm flow, and upstream river discharge. We applied an ARIMA time-series model to a three-year period for which we have high-frequency chemistry, meteorology, and streamflow data and analyzed external (rainfall, stream flow) and internal (dissolved O2) drivers of DOC content and composition. DOC composition was represented by fluorescence-based indices (fluorescence index, humification index, freshness) related to DOC source (microbially- vs. terrestrially-derived) and reactivity DOC. Patterns in DOC concentration and composition suggest carbon cycling in the lake responds to both meteorological events and to anthropogenic activity. The fluorescence-derived DOC composition is consistent with seasonally-distinct inputs of algal- and terrestrially-derived carbon. For example, Tempe Town Lake is supersaturated in O2 over 70% of the time, suggesting the system is autotrophic and primary productivity (i.e., O2 saturation state) was the strongest driver of DOC concentration. In contrast, external drivers (rainfall pattern, streamflow) were the strongest determinants of DOC composition. Biological processes (e.g., algal growth) generate carbon in the lake during spring and summer, and high Fluorescence Index and Freshness values at this time are indicative of algal-derived material; these parameters generally decrease with rain or flow suggesting algal-derived carbon is diluted by external water inputs. During dry periods, carbon builds up on the land surface and subsequent rainfall events deliver terrestrial carbon to the lake. Further evidence that rain and streamflow deliver land-derived material are increases in the Humification Index (an indicator of terrestrial material) following rain/flow events. Our results indicate that Tempe Town Lake generates autochthonous carbon and has the capacity to process allochthonous carbon from the urban environment. Ongoing work is comparing these results to other periods in the 10-year time series to test if the driver-DOC relationships are robust over longer time-scales and evaluating how changes in lake management and climate have altered DOC over time.

Temporal Patterns in Dissolved Organic Carbon Composition in an Urban Lake

NASA Astrophysics Data System (ADS)

Hartnett, H. E.; Palta, M. M.; Grimm, N. B.; Ruhi, A.; van Shaijik, M.

2017-12-01

Tempe Town Lake (TTL) is a hydrologically-regulated reservoir in Tempe, Arizona. The lake has high primary production and receives dissolved organic carbon (DOC) from rainfall, storm flow, and upstream river discharge. We applied an ARIMA time-series model to a three-year period for which we have high-frequency chemistry, meteorology, and streamflow data and analyzed external (rainfall, stream flow) and internal (dissolved O2) drivers of DOC content and composition. DOC composition was represented by fluorescence-based indices (fluorescence index, humification index, freshness) related to DOC source (microbially- vs. terrestrially-derived) and reactivity DOC. Patterns in DOC concentration and composition suggest carbon cycling in the lake responds to both meteorological events and to anthropogenic activity. The fluorescence-derived DOC composition is consistent with seasonally-distinct inputs of algal- and terrestrially-derived carbon. For example, Tempe Town Lake is supersaturated in O2 over 70% of the time, suggesting the system is autotrophic and primary productivity (i.e., O2 saturation state) was the strongest driver of DOC concentration. In contrast, external drivers (rainfall pattern, streamflow) were the strongest determinants of DOC composition. Biological processes (e.g., algal growth) generate carbon in the lake during spring and summer, and high Fluorescence Index and Freshness values at this time are indicative of algal-derived material; these parameters generally decrease with rain or flow suggesting algal-derived carbon is diluted by external water inputs. During dry periods, carbon builds up on the land surface and subsequent rainfall events deliver terrestrial carbon to the lake. Further evidence that rain and streamflow deliver land-derived material are increases in the Humification Index (an indicator of terrestrial material) following rain/flow events. Our results indicate that Tempe Town Lake generates autochthonous carbon and has the capacity to process allochthonous carbon from the urban environment. Ongoing work is comparing these results to other periods in the 10-year time series to test if the driver-DOC relationships are robust over longer time-scales and evaluating how changes in lake management and climate have altered DOC over time.

From drought to flooding: understanding the abrupt 2010-11 hydrological annual cycle in the Amazonas River and tributaries

NASA Astrophysics Data System (ADS)

Carlo Espinoza, Jhan; Ronchail, Josyane; Loup Guyot, Jean; Junquas, Clementine; Drapeau, Guillaume; Martinez, Jean Michel; Santini, William; Vauchel, Philippe; Lavado, Waldo; Ordoñez, Julio; Espinoza, Raúl

2012-06-01

In this work we document and analyze the hydrological annual cycles characterized by a rapid transition between low and high flows in the Amazonas River (Peruvian Amazon) and we show how these events, which may impact vulnerable riverside residents, are related to regional climate variability. Our analysis is based on comprehensive discharge, rainfall and average suspended sediment data sets. Particular attention is paid to the 2010-11 hydrological year, when an unprecedented abrupt transition from the extreme September 2010 drought (8300 m3 s-1) to one of the four highest discharges in April 2011 (49 500 m3 s-1) was recorded at Tamshiyacu (Amazonas River). This unusual transition is also observed in average suspended sediments. Years with a rapid increase in discharge are characterized by negative sea surface temperature anomalies in the central equatorial Pacific during austral summer, corresponding to a La Niña-like mode. It originates a geopotential height wave train over the subtropical South Pacific and southeastern South America, with a negative anomaly along the southern Amazon and the southeastern South Atlantic convergence zone region. As a consequence, the monsoon flux is retained over the Amazon and a strong convergence of humidity occurs in the Peruvian Amazon basin, favoring high rainfall and discharge. These features are also reported during the 2010-11 austral summer, when an intense La Niña event characterized the equatorial Pacific.

Characterization of rainfall events and correlation with reported disasters: A case in Cali, Colombia

NASA Astrophysics Data System (ADS)

Canon, C. C.; Tischbein, B.; Bogardi, J.

2017-12-01

Flood maps generally display the area that a river might overflow after a rainfall event takes place, under different scenarios of climate, land use/land cover, and/or failure of dams and dikes. However, rainfall is not limited to feed runoff and enlarge the river: it also causes minor disasters outside the map's highlighted area. The city of Cali in Colombia illustrates very well this situation: its flat topography and its major critical infrastructure near the river make it flood-risk prone; a heavy rainfall event would potentially deplete drinking water, electrical power and drainage capacity, and trigger outbreaks of water-borne diseases in the whole city, not only in the flooded area. Unfortunately, the government's disaster prevention strategies focus on the floodplain and usually overlook the aftermath of these minor disasters for being milder and scattered. Predicted losses in flood maps are potentially big, while those from minor disasters over the city are small but real, and citizens, utility companies and urban maintenance funds must constantly take them over. Mitigation and prevention of such minor disasters can save money for the development of the city in other aspects. This paper characterizes hundreds of rainfall events selected from 10-min step time series from 2006 to 2017, and finds their correlation with reported rainfall-related disasters throughout Cali, identified by date and neighborhood. Results show which rainfall parameters are most likely to indicate the occurrence of such disasters and their approximate location in the urban area of Cali. These results, when coupled with real-time observations of rainfall data and simulations of drainage network response, may help citizens and emergency bodies prioritize zones to assist during heavy storms. In the long term, stakeholders may also implement low impact development solutions in these zones to reduce flood risks.

In situ measurements of post-fire debris flows in southern California: Comparisons of the timing and magnitude of 24 debris-flow events with rainfall and soil moisture conditions

USGS Publications Warehouse

Kean, J.W.; Staley, D.M.; Cannon, S.H.

2011-01-01

Debris flows often occur in burned steeplands of southern California, sometimes causing property damage and loss of life. In an effort to better understand the hydrologic controls on post-fire debris-flow initiation, timing and magnitude, we measured the flow stage, rainfall, channel bed pore fluid pressure and hillslope soil-moisture accompanying 24 debris flows recorded in five different watersheds burned in the 2009 Station and Jesusita Fires (San Gabriel and Santa Ynez Mountains). The measurements show substantial differences in debris-flow dynamics between sites and between sequential events at the same site. Despite these differences, the timing and magnitude of all events were consistently associated with local peaks in short duration (< = 30 min) rainfall intensity. Overall, debris-flow stage was best cross-correlated with time series of 5-min rainfall intensity, and lagged the rainfall by an average of just 5 min. An index of debris-flow volume was also best correlated with short-duration rainfall intensity, but found to be poorly correlated with storm cumulative rainfall and hillslope soil water content. Post-event observations of erosion and slope stability modeling suggest that the debris flows initiated primarily by processes related to surface water runoff, rather than shallow landslides. By identifying the storm characteristics most closely associated with post-fire debris flows, these measurements provide valuable guidance for warning operations and important constraints for developing and testing models of post-fire debris flows. copyright. 2011 by the American Geophysical Union.

Streamflow and Erosion Response to Prolonged Intense Rainfall of November 1-2, 2000, Island of Hawaii, Hawaii

USGS Publications Warehouse

Fontaine, Richard A.; Hill, Barry R.

2002-01-01

A combination of several meteorologic and topographic factors produced extreme rainfall over the eastern part of the island of Hawaii on November 1-2, 2000. Storm rainfall was concentrated in two distinct areas, the Waiakea and Kapapala areas, where maximum rainfall totals of 32.47 and 38.97 inches were recorded. Resultant flooding caused damages in excess of 70 million dollars, among the highest totals associated with flooding in the State's history. Storm rainfall had recurrence intervals that ranged from 10 years or less for maximum 1-hour totals to 100 years or more for maximum 24-hour totals As part of this study, peak flow and/or erosion data were collected at 41 sites. Analyses of these data indicated that peak discharges of record occurred at 6 of 12 sites where historic data were available. Peak flows with estimated recurrence intervals from 50 to over 100 years were recorded at 4 of 11 sites. Peak flows were poorly correlated with total storm rainfall. Critical rainfall durations associated with peak flows ranged from 1 to 12 hours and were about 3 hours at most sites. Rainfall-runoff computations and field observations indicated that infiltration-excess overland flow alone was not sufficient to have caused the observed flood peaks and therefore saturation-excess overland flow and subsurface flow probably contributed to peak flows at most sites Most hillslope erosion associated with the storm took place along or near the Kaoiki Pali in the Kapapala area. Hillslope erosion was predominately caused by overland flow.

Critical rainfall conditions for the initiation of torrential flows. Results from the Rebaixader catchment (Central Pyrenees)

NASA Astrophysics Data System (ADS)

Abancó, Clàudia; Hürlimann, Marcel; Moya, José; Berenguer, Marc

2016-10-01

Torrential flows like debris flows or debris floods are fast movements formed by a mix of water and different amounts of unsorted solid material. They generally occur in steep torrents and pose high risk in mountainous areas. Rainfall is their most common triggering factor and the analysis of the critical rainfall conditions is a fundamental research task. Due to their wide use in warning systems, rainfall thresholds for the triggering of torrential flows are an important outcome of such analysis and are empirically derived using data from past events. In 2009, a monitoring system was installed in the Rebaixader catchment, Central Pyrenees (Spain). Since then, rainfall data of 25 torrential flows (;TRIG rainfalls;) were recorded, with a 5-min sampling frequency. Other 142 rainfalls that did not trigger torrential flows (;NonTRIG rainfalls;) were also collected and analyzed. The goal of this work was threefold: (i) characterize rainfall episodes in the Rebaixader catchment and compare rainfall data that triggered torrential flows and others that did not; (ii) define and test Intensity-Duration (ID) thresholds using rainfall data measured inside the catchment by with different techniques; (iii) analyze how the criterion used for defining the rainfall duration and the spatial variability of rainfall influences the value obtained for the thresholds. The statistical analysis of the rainfall characteristics showed that the parameters that discriminate better the TRIG and NonTRIG rainfalls are the rainfall intensities, the mean rainfall and the total rainfall amount. The antecedent rainfall was not significantly different between TRIG and NonTRIG rainfalls, as it can be expected when the source material is very pervious (a sandy glacial soil in the study site). Thresholds were derived from data collected at one rain gauge located inside the catchment. Two different methods were applied to calculate the duration and intensity of rainfall: (i) using total duration, Dtot, and mean intensity, Imean, of the rainfall event, and (ii) using floating durations, D, and intensities, Ifl, based on the maximum values over floating periods of different duration. The resulting thresholds are considerably different (Imean = 6.20 Dtot-0.36 and Ifl_90% = 5.49 D-0.75, respectively) showing a strong dependence on the applied methodology. On the other hand, the definition of the thresholds is affected by several types of uncertainties. Data from both rain gauges and weather radar were used to analyze the uncertainty associated with the spatial variability of the triggering rainfalls. The analysis indicates that the precipitation recorded by the nearby rain gauges can introduce major uncertainties, especially for convective summer storms. Thus, incorporating radar rainfall can significantly improve the accuracy of the measured triggering rainfall. Finally, thresholds were also derived according to three different criteria for the definition of the duration of the triggering rainfall: (i) the duration until the peak intensity, (ii) the duration until the end of the rainfall; and, (iii) the duration until the trigger of the torrential flow. An important contribution of this work is the assessment of the threshold relationships obtained using the third definition of duration. Moreover, important differences are observed in the obtained thresholds, showing that ID relationships are significantly dependent on the applied methodology.

Estimating the GIS-based soil loss and sediment delivery ratio to the sea for four major basins in South Korea.

PubMed

Lee, S E; Kang, S H

2013-01-01

This paper describes a sediment delivery ratio (SDR) using the Geographic Information System (GIS)-based Revised Universal Soil Loss Equation (RUSLE), to calculate the soil loss and sediment rating curve (SRC) basis of measured data in the six basins of Four Rivers, South Korea. The data set for calculating SDR was prepared during 3 years from 2008 to 2010. Mean soil loss in the six basins of Four Rivers was 515-869 t km(-2) yr(-1) and mean specific sediment yield (SSY) was 20-208 t km(-2) yr(-1) with basin size. The SDR ranged from 0.03 to 0.33 in the six rivers. Most sediment flows in the monsoon period from June to September (mean Max.: >97%; mean Min.: >84%), but SDR is lower than those of similar continental river basins. This is due to environmental factors, for example rainfall characteristics and associated run-off, soil characteristics and cultivated patterns with increasing basin size. This research provides the first application of SDR based on the observed field data in South Korea.

Detecting the hydrological impacts of forest cover change in tropical mountain areas: need for detrending time series of rainfall and streamflow data.

NASA Astrophysics Data System (ADS)

Molina, A.; Vanacker, V.; Brisson, E.; Balthazar, V.

2012-04-01

Interactions between human activities and the physical environment have increasingly transformed the hydrological functioning of Andean ecosystems. In these human-modified landscapes, land use/-cover change may have a profound effect on riverine water and sediment fluxes. The hydrological impacts of land use/-cover change are diverse, as changes in vegetation affect the various components of the hydrological cycle including evapotranspiration, infiltration and surface runoff. Quantitative data for tropical mountain regions are scarce, as few long time series on rainfall, water discharge and land use are available. Furthermore, time series of rainfall and streamflow data in tropical mountains are often highly influenced by large inter- and intra-annual variability. In this paper, we analyse the hydrological response to complex forest cover change for a catchment of 280 km2 located in the Ecuadorian Andes. Forest cover change in the Pangor catchment was reconstructed based on airphotos (1963, 1977), LANDSAT TM (1991) and ETM+ data (2001, 2009). From 1963, natural vegetation was converted to agricultural land and pine plantations: forests decreased by a factor 2, and paramo decreased by 20 km2 between 1963 and 2009. For this catchment, there exists an exceptionally long record of rainfall and streamflow data that dates back from the '70s till now, but large variability in hydrometeorological data exists that is partly related to ENSO events. Given the nonstationary and nonlinear character of the ENSO-related changes in rainfall, we used the Hilbert-Huang transformation to detrend the time series of the river flow data from inter- and intra-annual fluctuations in rainfall. After applying adaptive data analysis based on empirical model decomposition techniques, it becomes apparent that the long-term trend in streamflow is different from the long-term trend in rainfall data. While the streamflow data show a long-term decrease in monthly flow, the rainfall data have a trend of increasing and then decreasing precipitation amounts. These results suggest that the land use changes had an important impact on the total water yield of the catchment. Interestingly, the effect of reforestation in the upper part of the catchment with its associated decrease in water yield seems to be dominant over the effect of deforestation in the lower part of the basin.

Evidence of an Emerging Disturbance of Earthen Levees Causing Disastrous Floods in Italy

NASA Astrophysics Data System (ADS)

Orlandini, S.; Moretti, G.; Albertson, J. D.

2015-12-01

A levee failure occurred along the Secchia River, Northern Italy, on January 19, 2014, resulting in flood damage in excess of $500 Million (Figure). In response to this failure, immediate surveillance of other levees in the region led to the identification of a second breach developing on the neighboring Panaro River, where rapid mitigation efforts were successful in averting a full levee failure. The paired breach events that occurred along the Secchia and Panaro Rivers provided an excellent window on an emerging disturbance of levees and related failure mechanism. In the Secchia River, by combining the information content of photographs taken from helicopters in the early stage of breach development and 10-cm resolution aerial photographs taken in 2010 and 2012, animal burrows were found to exist in the precise levee location where the breach originated. In the Panaro River, internal erosion was observed to occur at a location where a crested porcupine den was known to exist and this erosion led to the collapse of the levee top. Evidence collected suggested that it is quite likely that the levee failure of the Secchia River was of a similar mechanism as the observed failure of the Panaro River. Detailed numerical modeling of rainfall, river flow, and variably saturated flow occurring in disturbed levees in response to complex hydroclimatic forcing indicated that the levee failure of the Secchia River may have been triggered by direct river inflow into the den system or collapse of a hypothetical den separated by a 1-m earthen wall from the levee riverside, which saturated during the hydroclimatic event. It is important to bring these processes to the attention of hydrologists and geotechnical engineers as well as to trigger an interdisciplinary discussion on habitat fragmentation and wildlife shifts due to development and climate pressures. These disturbances come together with changes in extreme events to inform the broader concern of risk analysis due to floods.

A new method for quantifying and modeling large scale surface water inundation dynamics and key drivers using multiple time series of Earth observation and river flow data. A case study for Australia's Murray-Darling Basin

NASA Astrophysics Data System (ADS)

Heimhuber, Valentin; Tulbure, Mirela G.; Broich, Mark

2017-04-01

Periodically inundated surface water (SW) areas such as floodplains are hotspots of biodiversity and provide a broad range of ecosystem services but have suffered alarming declines in recent history. Large scale flooding events govern the dynamics of these areas and are a critical component of the terrestrial water cycle, but their propagation through river systems and the corresponding long term SW dynamics remain poorly quantified on continental or global scales. In this research, we used an unprecedented Landsat-based time series of SW maps (1986-2011), to develop statistical inundation models and quantify the role of driver variables across the Murray-Darling Basin (MDB) (1 million square-km), which is Australia's bread basket and subject to competing demands over limited water resources. We fitted generalized additive models (GAM) between SW extent as the dependent variable and river flow data from 68 gauges, spatial time series of rainfall (P; interpolated gauge data), evapotranspiration (ET; AWRA-L land surface model) and soil moisture (SM; active passive microwave satellite remote sensing) as predictor variables. We used a fully directed and connected river network (Australian Geofabric) in combination with ancillary data, to develop a spatial modeling framework consisting of 18,521 individual modeling units. We then fitted individual models for all modeling units, which were made up of 10x10 km grid cells split into floodplain, floodplain-lake and non-floodplain areas, depending on the type of water body and its hydrologic connectivity to a gauged river. We applied the framework to quantify flood propagation times for all major river and floodplain systems across the MDB, which were in good accordance with observed travel times. After incorporating these flow lag times into the models, average goodness of fit was high across floodplains and floodplain-lake modeling units (r-squared > 0.65), which were primarily driven by river flow, and lower for non-floodplain areas (r-squared > 0.24), which were primarily driven by local rainfall. Our results indicate that local climate conditions (i.e. P, ET, SM) had more influence on SW dynamics in the northern compared to the southern MDB and were the most influential in the least regulated and most extended floodplains in the north-west. We also applied the statistical models of two floodplain areas with contrasting flooding regimes to predict SW extents of cloud-affected time steps in the Landsat time series during the large 2010 floods with high validated accuracy (r-squared > 0.97). Our findings illustrate that integrating multi-decadal time series of Earth observation data and in situ measurements with statistical modeling techniques can provide cost-effective tools for improving the management of limited SW resources and floods. The data-driven method is applicable to other large river basins and provides statistical models that can predict SW extent for cloud-affected Landsat observations or during the peak of floods and hence, allows a more detailed quantification of the dynamics of large floods compared to existing approaches. Future research will investigate the potential of image fusion techniques (i.e. ESTARFM) for improving the quantification of rapid changes in SW distribution by combining MODIS and Landsat imagery.

Flood of April 2-4, 2005, Delaware River Main Stem from Port Jervis, New York, to Cinnaminson, New Jersey

USGS Publications Warehouse

Reed, Timothy J.; Protz, Amy R.

2007-01-01

Several conditions, including saturated soils, snowmelt, and heavy rains, caused flooding on the Delaware River on April 2-4, 2005. The event occurred 50 years after the historic 1955 Delaware River flood, and only six months after a smaller but equally notable flood on September 18-19, 2004. The Delaware River flooded for a third time in 22 months in June, 2006. The peak flows and elevations of the 2005 flood were similar to those on June 28-29, 2006. The following report describes the April 2-4, 2005, Delaware River flood, and includes the associated precipitation amounts, peak flows and elevations, and flood frequencies. A comparison of historic Delaware River floods also is presented. The appendix of the report contains detailed information for 156 high-water mark elevations obtained on the main stem of the Delaware River from Port Jervis, New York, to Cinnaminson, New Jersey, for the April 2-4, 2005 flood. The April 2005 event originated with frequent precipitation from December 2004 to March 2005 which saturated the soils in the upper Delaware River Basin. The cold winter froze some of the soils and left a snowpack at higher elevations equivalent to as much as 10 inches of water in some areas. Temperatures rose above freezing, and heavy rains averaging 1 to 3 inches on March 27, 2005, melted some of the snow, causing the Delaware River to rise; however, peak elevations were still 2 to 7 feet below flood stage. Another round of rainfall averaging 2-5 inches in the basin on April 2, 2005, melted the remaining snowpack. The combination of snowmelt and runoff from the two storms produced flood conditions along the main stem of the Delaware River. Flood frequencies of flows at selected tributaries to the Delaware River did not exceed the 35-year recurrence intervals. The Delaware River main stem peak-flow recurrence intervals ranged from 40 to 80 years; flows were approximately 20 percent less than those from the peak of record in 1955. Peak elevations exceeded National Weather Service flood stages defined at continuous-record streamflow-gaging stations by 5 to 7 feet, but were on average 3 to 5 feet lower than the peak of record in August 1955. Peak elevations determined at 48 sites along the main stem of the Delaware River defined the flood profile between the gaging stations. The peak elevation in the tide-effected portion of the Delaware (downstream of Trenton, New Jersey), occurred on April 2, 2 days before the riverine peak, as a result of water pushed into the bay by a low-pressure system situated just off the coast. Every county located along the main stem of the Delaware River was declared a Federal disaster area. Property damage estimates in Pennsylvania, New York, and New Jersey exceeded $200 million.

Storm and flood of July 31-August 1, 1976, in the Big Thompson River and Cache la Poudre River basins, Larimer and Weld Counties, Colorado

USGS Publications Warehouse

McCain, Jerald F.; Shroba, R.R.

1979-01-01

PART A: Devastating flash floods swept through the canyon section of Larimer County in north-central Colorado during the night of July 31-August I, 1976, causing 139 deaths, 5 missing persons, and more than $35 million in total damages. The brunt of the storms occurred over the Big Thompson River basin between Drake and Estes Park with rainfall amounts as much as 12 inches being reported during the storm period. In the Cache la Poudre River basin to the north, a rainfall amount of 10 inches was reported for one locality while 6 inches fell over a widespread area near the central part of the basin. The storms developed when strong low-level easterly winds to the rear of a polar front pushed a moist, conditionally unstable airmass upslope into the Front Range of the Rocky Mountains. Orographic uplift released the convective instability, and light south-southeasterly winds at middle and upper levels allowed the storm complex to remain nearly stationary over the foothills for several hours. Minimal entrainment of relatively moist air at middle and upper levels, very low cloud bases, and a slightly tilted updraft structure contributed to a high precipitation efficiency. Intense rainfall began soon after 1900 MDT (Mountain Daylight Time) in the Big Thompson River and the North Fork Cache la Poudre River basins. A cumulative rainfall curve developed for Glen Comfort from radar data indicates that 7.5 inches of rain fell during the period 1930-2040 MDT on July 31. In the central part of the storm area west of Fort Collins, the heaviest rainfall began about 2200 MDT on July 31 and continued until 0100 MDT on August 1. Peak discharges were extremely large on many streams in the storm area-exceeding previously recorded maximum discharges at several locations. The peak discharge of the Big Thompson River at the gaging station at the canyon mouth, near Drake was 31,200 cubic feet per second or more than four times the previous maximum discharge of 7,600 cubic feet per second at the site during 88 years of flood history. At the gaging station on the North Fork Big Thompson River at Drake, the peak discharge on July 31 was 8,710 cubic feet per second as compared to the previous maximum discharge during 29 years of record of 1,290 cubic feet per second. Peak discharges for three small tributaries near the area of heaviest rainfall northeast of Estes Park exceeded previously recorded maximum discharges for basins of less than 4 square miles in Colorado. Stream velocities were rapid along the tributaries near the storm center and on the Big Thompson River in the canyon section, with average velocities of 20-25 feet per second being common. The flood crest on the Big Thompson River moved through the 7.7-mile reach between Drake and the canyon mouth in about 30 minutes for an average travel rate of 15 miles per hour, or about 23 feet per second. The peak discharge of the flood on the Big Thompson River at the canyon mouth exceeded the 100-year flood discharge for the site by a ratio of 1.8. Upstream in the Big Thompson River basin, the flood was even more rare being 3.8 times the estimated 100-year flood discharge at the site on the Big Thompson River just upstream from Drake. In the Cache la Poudre River basin, recurrence intervals were computed to be 100 years for the flood on Deadman Creek and 16 years for Rist Canyon and the Cache la Poudre River at the canyon mouth near Fort Collins. Although the rainfall and flood discharges were unusually large, they are not unprecedented for some areas along the eastern foothills and plains of Colorado. The May 1935 and June 1965 floods on some streams along the eastern plains greatly exceeded the 1976 flood peaks in the storm area. Prior floods on several other streams in the foothills have approximately equaled the 1976 peak discharges. PART B: Intense rainfall from the Big Thompson thunderstorm complex on the evening of July 31,1976, and the ensuing floods that evening and the fol

Rainfall-runoff modelling of the Okavango River catchment to assess impacts of land use change on runoff and downstream ecosystems

NASA Astrophysics Data System (ADS)

Milzow, Christian; Bauer-Gottwein, Peter

2010-05-01

The competition between human water use and ecosystem water use is one of the major challenges for water resources management at the global scale. We analyse the situation for the Okavango River basin of southern Africa. The Okavango River is representative for many large rivers throughout the developing world in that it is ungauged and poorly studied. The Okavango basin - spanning over Angola, Namibia and Botswana - represents a multi-objective problem in an international setting. Economic benefits of agricultural development and conservation of ecosystem services call for opposed actions. A semi-distributed rainfall-runoff model of the Okavango catchment is set up using the Soil and Water Assessment Tool (SWAT). The model is sufficiently physically based to simulate the impact on runoff of extent of agricultural use, crop types and management practices. Precipitation and temperature inputs are taken from datasets covering large parts of the globe. The methodology can thus easily be applied for other ungauged catchments. For temperature we use the ERA-Interim reanalysis product of the European Centre for Medium-Range Weather Forecasts and for precipitation the Famine Early Warning Systems Network data (FEWS-Net). Tropical Rainfall Measurement Mission (TRMM) data resulted in poor model performance compared to the FEWS-Net data. Presently, the upstream catchment in Angola is largely pristine and agriculture is basically restricted to dry land subsistence farming. But economic growth in Angola is likely to result in agricultural development and consequent impacts on catchment runoff. Land use scenarios that are simulated include large scale irrigated agriculture with water extractions from the river and the shallow aquifer. Climate change impacts are also studied and compared to land use change impacts. The downstream part of the basin consists of the large Okavango Wetlands, which are a biodiversity hotspot of global importance and, through tourism, an important source of economic income for Botswana. A second hydrological model simulating flow through the wetlands is used to study the impact of catchment runoff changes on the hydrology and ecology of the wetlands. The final goal of the project is to demonstrate the relation between economic benefits of water abstractions in the upstream and downstream environmental impact. Furthermore the results will provide a basis for defining adequate compensations for upstream stakeholders who forego benefits of agricultural intensification to ensure the conservation of downstream ecosystem services.

Coastal Ocean Variability off the Coast of Taiwan in Response to Typhoon Morakot: River Forcing, Atmospheric Forcing, and Cold Dome Dynamics

DTIC Science & Technology

2014-09-01

within a very short time period and in this research, we model and study the effects of this rainfall on Taiwan?s coastal oceans as a result of river...and in this research, we model and study the effects of this rainfall on Taiwan’s coastal oceans as a result of river discharge. We do this through...54 4 Results 57 4.1 Effects of Footprint Shape on the Bulk Mixing Model . . . . . . . . . 57 4.2 Effects of the Horizontal Extent of the Bulk

The Impacts of California's San Francisco Bay Area Gap on Precipitation Observed in the Sierra Nevada during Hmt and Calwater

NASA Astrophysics Data System (ADS)

White, A. B.; Neiman, P. J.; Creamean, J.; Coleman, T.; Ralph, F. M.; Prather, K. A.

2014-12-01

The National Oceanic and Atmospheric Administration (NOAA)'s Hydrometeorology Testbed (HMT; hmt.noaa.gov) conducts research on the meteorological and microphysical processes contributing to orographically enhanced precipitation. Some of HMT's precipitation research has been focused on a shallow rainfall process driven by collision-coalescence that often is undetected by the National Weather Service's operational scanning radar network, especially in the Western U.S., but that can produce rain rates that are capable of creating floods. Originally it was believed that this shallow rainfall process would occur more prevalently over the coastal mountain ranges than over the Sierra Nevada, since the higher mountains of the Sierra would force deeper atmospheric ascent and produce deeper precipitating cloud systems that extend well above the melting level. This notion was disproved when it was recently discovered that a site in the northern Sierra had nearly as large of a contribution to seasonal rainfall from this shallow rainfall process, on average, as did a habitually wet site in the coast range of Sonoma County north of San Francisco. This work examines this apparent paradox using observations collected during HMT and CalWater field campaigns. In particular, a case study from CalWater is used to highlight the interaction between a landfalling atmospheric river (AR) and the Sierra Barrier Jet (SBJ). The gap in coastal terrain associated with the San Francisco Bay area is shown to allow unprocessed, moisture-enhanced flow in the AR to reach the northern Sierra site, where the SBJ provides a lifting mechanism to create enhanced orographic precipitation as compared to a site in the southern Sierra, where AR-associated dynamics are weaker and AR flow is modified by upstream coastal terrain.

The biogeochemistry of arsenic in a remote UK upland site: trends in rainfall and runoff, and comparisons with urban rivers.

PubMed

Rowland, A P; Neal, C; Reynolds, B; Jarvie, H P; Sleep, D; Lawlor, A J; Neal, M

2011-05-01

Ten years of monitoring of rainfall and streams in the remote acidic and acid sensitive moorland and afforested moorland of upland mid-Wales reveals concentrations of arsenic (As) typically <1 µg L(-1). On average, the lowest concentrations occur within rainfall and they have declined over time probably in response to reductions in global emissions. There is a corresponding reduction within the streams except for forested systems where concentrations up to doubled following clear-fell. Within the streams there are both annual cycling and diurnal cycling of As. The annual cycling gives maxima during the summer months and this probably reflects the importance of groundwater inputs and mineralisation/desorption from the surface soil layers. Correspondingly, the diurnal cycling occurs during the summer months at low flow periods with As concentrations highest in the afternoon/evening. For the urban/industrial basins of northern England with historically a much higher As deposition, land contamination and effluent discharges, comparative data indicate As concentrations around three fold higher: strong seasonal patterns are observed for the same reasons as with the uplands. Across the sites, the As concentrations are over an order of magnitude lower than that of environmental concern. Nonetheless, the results clearly show the effects of declining emissions on rainfall deposition and some indication of areas of historic contamination. Arsenic is mainly present in the <0.45 fraction, but cross-flow filtration indicates that approx. 43% is in the colloidal phase at the clean water sites, and 16% in the colloidal phase at the contaminated sites. Part of this colloidal component may well be associated with organic carbon.

Effects of variable regolith depth, hydraulic properties, and rainfall on debris-flow initiation during the September 2013 northern Colorado Front Range rainstorm

NASA Astrophysics Data System (ADS)

Baum, R. L.; Coe, J. A.; Kean, J. W.; Jones, E. S.; Godt, J.

2015-12-01

Heavy rainfall during 9 - 13 September 2013 induced about 1100 debris flows in the foothills and mountains of the northern Colorado Front Range. Weathered bedrock was partially exposed in the basal surfaces of many of the shallow source areas at depths ranging from 0.2 to 5 m. Typical values of saturated hydraulic conductivity of soils and regolith units mapped in the source areas range from about 10-4 - 10-6 m/s, with a median value of 2.8 x 10-5 m/s based on number of source areas in each map unit. Rainfall intensities varied spatially and temporally, from 0 to 2.5 x 10-5 m/s (90 mm/hour), with two periods of relatively heavy rainfall on September 12 - 13. The distribution of debris flows appears to correlate with total storm rainfall, and reported times of greatest landslide activity coincide with times of heaviest rainfall. Process-based models of rainfall infiltration and slope stability (TRIGRS) representing the observed ranges of regolith depth, hydraulic conductivity, and rainfall intensity, provide additional insights about the timing and distribution of debris flows from this storm. For example, small debris flows from shallower source areas (<2 m) occurred late on September 11 and in the early morning of September 12, whereas large debris flows from deeper (3 - 5 m) source areas in the western part of the affected area occurred late on September 12. Timing of these flows can be understood in terms of the time required for pore pressure rise depending on regolith depth and rainfall intensity. The variable hydraulic properties combined with variable regolith depth and slope angles account for much of the observed range in timing in areas of similar rainfall intensity and duration. Modeling indicates that the greatest and most rapid pore pressure rise likely occurred in areas of highest rainfall intensity and amount. This is consistent with the largest numbers of debris flows occurring on steep canyon walls in areas of high total storm rainfall.

Hydroclimate temporal variability in a coastal Mediterranean watershed: the Tafna basin, North-West Algeria

NASA Astrophysics Data System (ADS)

Boulariah, Ouafik; Longobardi, Antonia; Meddi, Mohamed

2017-04-01

One of the major challenges scientists, practitioners and stakeholders are nowadays involved in, is to provide the worldwide population with reliable water supplies, protecting, at the same time, the freshwater ecosystems quality and quantity. Climate and land use changes undermine the balance between water demand and water availability, causing alteration of rivers flow regime. Knowledge of hydro-climate variables temporal and spatial variability is clearly helpful to plan drought and flood hazard mitigation strategies but also to adapt them to future environmental scenarios. The present study relates to the coastal semi-arid Tafna catchment, located in the North-West of Algeria, within the Mediterranean basin. The aim is the investigation of streamflow and rainfall indices temporal variability in six sub-basins of the large catchment Tafna, attempting to relate streamflow and rainfall changes. Rainfall and streamflow time series have been preliminary tested for data quality and homogeneity, through the coupled application of two-tailed t test, Pettitt test and Cumsum tests (significance level of 0.1, 0.05 and 0.01). Subsequently maximum annual daily rainfall and streamflow and average daily annual rainfall and streamflow time series have been derived and tested for temporal variability, through the application of the Mann Kendall and Sen's test. Overall maximum annual daily streamflow time series exhibit a negative trend which is however significant for only 30% of the station. Maximum annual daily rainfall also e exhibit a negative trend which is intend significant for the 80% of the stations. In the case of average daily annual streamflow and rainfall, the tendency for decrease in time is unclear and, in both cases, appear significant for 60% of stations.

Flooding on California's Russian River: Role of atmospheric rivers

USGS Publications Warehouse

Ralph, F.M.; Neiman, P.J.; Wick, G.A.; Gutman, S.I.; Dettinger, M.D.; Cayan, D.R.; White, A.B.

2006-01-01

Experimental observations collected during meteorological field studies conducted by the National Oceanic and Atmospheric Administration near the Russian River of coastal northern California are combined with SSM/I satellite observations offshore to examine the role of landfalling atmospheric rivers in the creation of flooding. While recent studies have documented the characteristics and importance of narrow regions of strong meridional water vapor transport over the eastern Pacific Ocean (recently referred to as atmospheric rivers), this study describes their impact when they strike the U.S. West Coast. A detailed case study is presented, along with an assessment of all 7 floods on the Russian River since the experimental data were first available in October 1997. In all 7 floods, atmospheric river conditions were present and caused heavy rainfall through orographic precipitation. Not only do atmospheric rivers play a crucial role in the global water budget, they can also lead to heavy coastal rainfall and flooding, and thus represent a key phenomenon linkingweather and climate. Copyright 2006 by the American Geophysical Union.

On the use of MODIS and TRMM products to simulate hydrological processes in the La Plata Basin

NASA Astrophysics Data System (ADS)

Saavedra Valeriano, O. C.; Koike, T.; Berbery, E. H.

2009-12-01

La Plata basin is targeted to establish a distributed water-energy balance model using NASA and JAXA satellite products to estimate fluxes like the river discharge at sub-basin scales. The coupled model is called the Water and Energy Budget-based Distributed Hydrological Model (WEB-DHM), already tested with success in the Little Washita basin, Oklahoma, and the upper Tone River in Japan. The model demonstrated the ability to reproduce point-scale energy fluxes, CO2 flux, and river discharges. Moreover, the model showed the ability to predict the basin-scale surface soil moisture evolution in a spatially distributed fashion. In the context of the La Plata Basin, the first step was to set-up the water balance component of the distributed hydrological model of the entire basin using available global geographical data sets. The geomorphology of the basin was extracted using 1-km DEM resolution (obtained from EROS, Hydro 1K). The total delineated watershed reached 3.246 millions km2, identifying 145 sub-basins with a computing grid of 10-km. The distribution of land cover, land surface temperature, LAI and FPAR were obtained from MODIS products. In a first instance, the model was forced by gridded rainfall from the Climate Prediction Center (derived from available rain gauges) and satellite precipitation from TRMM 3B42 (NASA & JAXA). The simulated river discharge using both sources of data was compared and the overall low flow and normal peaks were identified. It was found that the extreme peaks tend to be overestimated when using TRMM 3B42. However, TRMM data allows tracking rainfall patterns which might be missed by the sparse distribution of rain gauges over some areas of the basin.

Quantifying water requirements of riparian river red gum (Eucalyptus camaldulensis) in the Murray-Darling Basin, Australia: Implications for the management of environmental flows

USGS Publications Warehouse

Doody, Tanya M.; Colloff, Matthew J.; Davies, Micah; Koul, Vijay; Benyon, Richard G.; Nagler, Pamela L.

2015-01-01

Water resource development and drought have altered river flow regimes, increasing average flood return intervals across floodplains in the Murray-Darling Basin, Australia, causing health declines in riparian river red gum (Eucalyptus camaldulensis) forests and woodlands. Environmental flow allocations helped to alleviate water stress during the recent Millennium Drought (1997–2010), however, quantification of the flood frequency required to support healthy E. camaldulensis communities is still needed. We quantified water requirements of E. camaldulensis for two years across a flood gradient (trees inundated at frequencies of 1:2, 1:5 and 1:10 years) at Yanga National Park, New South Wales to help inform management decision-making and design of environmental flows. Sap flow, evaporative losses and soil moisture measurements were used to determine transpiration, evapotranspiration and plant-available soil water before and after flooding. A formula was developed using plant-available soil water post-flooding and average annual rainfall, to estimate maintenance time of soil water reserves in each flood frequency zone. Results indicated that soil water reserves could sustain 1:2 and 1:5 trees for 15 months and six years, respectively. Trees regulated their transpiration rates, allowing them to persist within their flood frequency zone, and showed reduction in active sapwood area and transpiration rates when flood frequencies exceeded 1:2 years. A leaf area index of 0.5 was identified as a potential threshold indicator of severe drought stress. Our results suggest environmental water managers may have greater flexibility to adaptively manage floodplains in order to sustain E. camaldulensis forests and woodlands than has been appreciated hitherto.

Is there a `universal' dynamic zero-parameter hydrological model? Evaluation of a dynamic Budyko model in US and India

NASA Astrophysics Data System (ADS)

Patnaik, S.; Biswal, B.; Sharma, V. C.

2017-12-01

River flow varies greatly in space and time, and the single biggest challenge for hydrologists and ecologists around the world is the fact that most rivers are either ungauged or poorly gauged. Although it is relatively easier to predict long-term average flow of a river using the `universal' zero-parameter Budyko model, lack of data hinders short-term flow prediction at ungauged locations using traditional hydrological models as they require observed flow data for model calibration. Flow prediction in ungauged basins thus requires a dynamic 'zero-parameter' hydrological model. One way to achieve this is to regionalize a dynamic hydrological model's parameters. However, a regionalization method based zero-parameter dynamic hydrological model is not `universal'. An alternative attempt was made recently to develop a zero-parameter dynamic model by defining an instantaneous dryness index as a function of antecedent rainfall and solar energy inputs with the help of a decay function and using the original Budyko function. The model was tested first in 63 US catchments and later in 50 Indian catchments. The median Nash-Sutcliffe efficiency (NSE) was found to be close to 0.4 in both the cases. Although improvements need to be incorporated in order to use the model for reliable prediction, the main aim of this study was to rather understand hydrological processes. The overall results here seem to suggest that the dynamic zero-parameter Budyko model is `universal.' In other words natural catchments around the world are strikingly similar to each other in the way they respond to hydrologic inputs; we thus need to focus more on utilizing catchment similarities in hydrological modelling instead of over parameterizing our models.

Post-fire debris-flow hazard assessment of the area burned by the 2013 Beaver Creek Fire near Hailey, central Idaho

USGS Publications Warehouse

Skinner, Kenneth D.

2013-01-01

A preliminary hazard assessment was developed for debris-flow hazards in the 465 square-kilometer (115,000 acres) area burned by the 2013 Beaver Creek fire near Hailey in central Idaho. The burn area covers all or part of six watersheds and selected basins draining to the Big Wood River and is at risk of substantial post-fire erosion, such as that caused by debris flows. Empirical models derived from statistical evaluation of data collected from recently burned basins throughout the Intermountain Region in Western United States were used to estimate the probability of debris-flow occurrence, potential volume of debris flows, and the combined debris-flow hazard ranking along the drainage network within the burn area and to estimate the same for analyzed drainage basins within the burn area. Input data for the empirical models included topographic parameters, soil characteristics, burn severity, and rainfall totals and intensities for a (1) 2-year-recurrence, 1-hour-duration rainfall, referred to as a 2-year storm (13 mm); (2) 10-year-recurrence, 1-hour-duration rainfall, referred to as a 10-year storm (19 mm); and (3) 25-year-recurrence, 1-hour-duration rainfall, referred to as a 25-year storm (22 mm). Estimated debris-flow probabilities for drainage basins upstream of 130 selected basin outlets ranged from less than 1 to 78 percent with the probabilities increasing with each increase in storm magnitude. Probabilities were high in three of the six watersheds. For the 25-year storm, probabilities were greater than 60 percent for 11 basin outlets and ranged from 50 to 60 percent for an additional 12 basin outlets. Probability estimates for stream segments within the drainage network can vary within a basin. For the 25-year storm, probabilities for stream segments within 33 basins were higher than the basin outlet, emphasizing the importance of evaluating the drainage network as well as basin outlets. Estimated debris-flow volumes for the three modeled storms range from a minimal debris flow volume of 10 cubic meters [m3]) to greater than 100,000 m3. Estimated debris-flow volumes increased with basin size and distance downstream. For the 25-year storm, estimated debris-flow volumes were greater than 100,000 m3 for 4 basins and between 50,000 and 100,000 m3 for 10 basins. The debris-flow hazard rankings did not result in the highest hazard ranking of 5, indicating that none of the basins had a high probability of debris-flow occurrence and a high debris-flow volume estimate. The hazard ranking was 4 for one basin using the 10-year-recurrence storm model and for three basins using the 25-year-recurrence storm model. The maps presented herein may be used to prioritize areas where post-wildfire remediation efforts should take place within the 2- to 3-year period of increased erosional vulnerability.

Debris-flow and flooding hazards associated with the December 1999 storm in coastal Venezuela and strategies for mitigation

USGS Publications Warehouse

Wieczorek, G.F.; Larsen, M.C.; Eaton, L.S.; Morgan, B.A.; Blair, J.L.

2001-01-01

Heavy rainfall from the storm of December 14-16, 1999 triggered thousands of landslides on steep slopes of the Sierra de Avila north of Caracas, Venezuela. In addition to landslides, heavy rainfall caused flooding and massive debris flows that damaged coastal communities in the State of Vargas along the Caribbean Sea. Examination of the rainfall pattern obtained from the GOES-8 satellite showed that the pattern of damage was generally consistent with the area of heaviest rainfall. Field observations of the severely affected drainage basins and historical records indicate that previous flooding and massive debris-flow events of similar magnitude to that of December 1999 have occurred throughout this region. The volume of debris-flow deposits and the large boulders that the flows transported qualifies the 1999 event amongst the largest historical rainfall-induced debris flows documented worldwide.

Different kernel functions due to rainfall response from borehole strainmeter in Taiwan

NASA Astrophysics Data System (ADS)

Yen Chen, Chih; Hu, Jyr Ching; LIu, Chi Ching

2014-05-01

In order to realize reasons inducing earthquakes, project of monitoring of the fault activity using 3-component Gladwin Tensor Strainmeter (GTSM) has been initiated since 2003 in Taiwan, which is one of the most active seismic regions in the world. Observed strain contains several different effects within including barometric, tidal, groundwater, precipitation, tectonics, seismic and other irregular noise. After removing the response of tides and air pressure on strain, we still can find some anomalies highly related to the rainfall in short time in days. The strain response induced by rainfall can be separated into two parts as observation in groundwater, slow response and quick response, respectively. Quick response reflects the strain responding to the load of falling water drops on the ground surface. A kernel function shows the continual response induced by unit precipitation water in time domain. We split the quick response from data removing tidal and barometric response, and then calculate the kernel function by use of deconvolution method. More, an average kernel function was calculated to reduce the noise level. There are five of the sites installed by CGS Taiwan were selected to calculate kernel functions for individual sites. The results show there may be different on rainfall response in different environmental settings. In the case of stations site on gentle terrain, kernel function for each site shows the similar trend, it rises quickly to maximum in 1 to 2 hrs, and then goes down near to zero gently in period of 2-3 days. But in the case of sites settled side by the rivers, there will be 2nd peak of function when collected water in the catchment flows along by the sites related to the hydrograph of creeks. More, landslides will occur in some sites in hazard of landslide with more rainfall stored on, just like DARB in ChiaYi. The curve of kernel function will be controlled by landslides and debris flows.

Potentiometric Surface of the Upper Floridan Aquifer in the St. Johns River Water Management District and Vicinity, Florida, May 2005

USGS Publications Warehouse

Kinnaman, Sandra L.

2006-01-01

INTRODUCTION This map depicts the potentiometric surface of the upper Floridan aquifer in the St. Johns River Water Management District and vicinity for May 2005. Potentiometric contours are based on water level measurements collected at 598 wens during the period May 5 - 31, near the end of the dry season. Some contours are inferred from previous potentiometric-surface maps with larger well networks. The potentiometric surface of the carbonate upper Floridan aquifer responds mainly to rainfall, and more locally, to ground water withdrawals. Potentiometric-surface highs generally correspond to topographic highs where the aquifer is recharged. Springs and areas of diffuse upward leakage naturally discharge water from the aquifer and are most prevalent along the St. Johns River. Areas of discharge are reflected by depressions in the potentiometric surface. Ground water withdrawals locally have lowered the potentiometric surface. Ground water in the upper Floridan aquifer generally flows from potentiometric highs to potentiometric lows in a direction perpendicular to the contours.

Potentiometric Surface of the Upper Floridan Aquifer in the St. Johns River Water Management District and Vicinity, Florida, May 2006

USGS Publications Warehouse

Kinnaman, Sandra L.

2006-01-01

Introduction: This map depicts the potentiometric surface of the Upper Floridan aquifer in the St. Johns River Water Management District and vicinity for May 2006. Potentiometric contours are based on water-level measurements collected at 599 wells during the period May 14-31, near the end of the dry season. Some contours are inferred from previous potentiometric-surface maps with larger well networks. The potentiometric surface of the carbonate Upper Floridan aquifer responds mainly to rainfall, and more locally, to ground-water withdrawals and springflow. Potentiometric-surface highs generally correspond to topographic highs where the aquifer is recharged. Springs and areas of diffuse upward leakage naturally discharge water from the aquifer and are most prevalent along the St. Johns River. Areas of discharge are reflected by depressions in the potentiometric surface. Ground-water withdrawals locally have lowered the potentiometric surface. Ground water in the Upper Floridan aquifer generally flows from potentiometric highs to potentiometric lows in a direction perpendicular to the contours.

Potentiometric surface of the Upper Floridan aquifer in the St. Johns River water management district and vicinity, Florida, September 2005

USGS Publications Warehouse

Kinnaman, Sandra L.

2006-01-01

This map depicts the potentiometric surface of the Upper Floridan aquifer in the St. Johns River Water Management District and vicinity for September 2005. Potentiometric contours are based on water-level measurements collected at 643 wells during the period September 12-28, near the end of the wet season. Some contours are inferred from previous potentiometric-surface maps with larger well networks. The potentiometric surface of the carbonate Upper Floridan aquifer responds mainly to rainfall, and more locally, to ground-water withdrawals and springflow. Potentiometric-surface highs generally correspond to topographic highs where the aquifer is recharged. Springs and areas of diffuse upward leakage naturally discharge water from the aquifer and are most prevalent along the St. Johns River. Areas of discharge are reflected by depressions in the potentiometric surface. Ground-water withdrawals locally have lowered the potentiometric surface. Ground water in the Upper Floridan aquifer generally flows from potentiometric highs to potentiometric lows in a direction perpendicular to the contours.

Hydrologic data for urban storm runoff in the Denver metropolitan area, Colorado

USGS Publications Warehouse

Gibbs, Johnnie W.; Doefer, John T.

1982-01-01

Urban storm-runoff data collected from April through September 1981 from nine Denver Nationwide Urban Runoff Program sites, urban storm-runoff data collected from April 1980 through September 1981 from ten South Platte River Study sites, and rainfall-runoff simulation data from two sites for June 1980 and May 1981 are presented in this report. The Denver Nationwide Urban Runoff Program sites were two single-family residential areas, two multifamily residential areas, one commercial area (shopping center), one mixed commercial and multifamily residential area, one natural area (open space), and two detention ponds. The South Platte River Study sites were six tributaries of the South Platte River and four instream sites on the South Platte River. The tributary sites were Bear Creek at mouth, at Sheridan; Harvard Gulch at Harvard Park, at Denver; Sanderson Gulch at mouth, at Denver; Weir Gulch at mouth, at Denver; Lakewood Gulch at mouth, at Denver; and Cherry Creek at Denver. The instream sites were South Platte River at Littleton; South Platte River at Florida Avenue, at Denver; South Platte River at Denver; and South Platte River at 50th Avenue, at Denver. The rainfall-runoff simulation sites were North Avenue at Denver Federal Center, at Lakewood and Rooney Gulch at Rooney Ranch, near Morrison. Precipitation, rainfall-runoff, water-quality data, and basin characteristics were collected at the urban storm-runoff sites. The urban storm-runoff data may be used to characterize runoff loading for various land-use types in Denver and other semiarid regions. (USGS)

Evaluation of rainfall structure on hydrograph simulation: Comparison of radar and interpolated methods, a study case in a tropical catchment

NASA Astrophysics Data System (ADS)

Velasquez, N.; Ochoa, A.; Castillo, S.; Hoyos Ortiz, C. D.

2017-12-01

The skill of river discharge simulation using hydrological models strongly depends on the quality and spatio-temporal representativeness of precipitation during storm events. All precipitation measurement strategies have their own strengths and weaknesses that translate into discharge simulation uncertainties. Distributed hydrological models are based on evolving rainfall fields in the same time scale as the hydrological simulation. In general, rainfall measurements from a dense and well maintained rain gauge network provide a very good estimation of the total volume for each rainfall event, however, the spatial structure relies on interpolation strategies introducing considerable uncertainty in the simulation process. On the other hand, rainfall retrievals from radar reflectivity achieve a better spatial structure representation but with higher uncertainty in the surface precipitation intensity and volume depending on the vertical rainfall characteristics and radar scan strategy. To assess the impact of both rainfall measurement methodologies on hydrological simulations, and in particular the effects of the rainfall spatio-temporal variability, a numerical modeling experiment is proposed including the use of a novel QPE (Quantitative Precipitation Estimation) method based on disdrometer data in order to estimate surface rainfall from radar reflectivity. The experiment is based on the simulation of 84 storms, the hydrological simulations are carried out using radar QPE and two different interpolation methods (IDW and TIN), and the assessment of simulated peak flow. Results show significant rainfall differences between radar QPE and the interpolated fields, evidencing a poor representation of storms in the interpolated fields, which tend to miss the precise location of the intense precipitation cores, and to artificially generate rainfall in some areas of the catchment. Regarding streamflow modelling, the potential improvement achieved by using radar QPE depends on the density of the rain gauge network and its distribution relative to the precipitation events. The results for the 84 storms show a better model skill using radar QPE than the interpolated fields. Results using interpolated fields are highly affected by the dominant rainfall type and the basin scale.

Magnitude and timing of downstream channel aggradation and degradation in response to a dome-building eruption at Mount Hood, Oregon

USGS Publications Warehouse

Pierson, Thomas C.; Pringle, Patrick T.; Cameron, Kenneth A.

2011-01-01

A dome-building eruption at Mount Hood, Oregon, starting in A.D. 1781 and lasting until ca. 1793, produced dome-collapse lithic pyroclastic flows that triggered lahars and intermittently fed 108 m3 of coarse volcaniclastic sediment to sediment reservoirs in headwater canyons of the Sandy River. Mobilization of dominantly sandy sediment from these reservoirs by lahars and seasonal floods initiated downstream migration of a sediment wave that resulted in a profound cycle of aggradation and degradation in the lowermost reach of the river (depositional reach), 61-87 km from the source. Stratigraphic and sedimentologic relations in the alluvial fill, together with dendrochronologic dating of degradation terraces, demonstrate that (1) channel aggradation in response to sediment loading in the headwater canyons raised the river bed in this reach at least 23 m in a decade or less; (2) the transition from aggradation to degradation in the upper part of this reach roughly coincided with the end of the dome-building eruption; (3) fluvial sediment transport and deposition, augmented by one lahar, achieved a minimum average aggradation rate of ~2 m/yr; (4) the degradation phase of the cycle was more prolonged than the aggradation phase, requiring more than half a century for the river to reach its present bed elevation; and (5) the present longitudinal profile of the Sandy River in this reach is at least 3 m above the pre-eruption profile. The pattern and rate of channel response and recovery in the Sandy River following heavy sediment loading resemble those of other rivers similarly subjected to very large sediment inputs. The magnitude of channel aggradation in the lower Sandy River, greater than that achieved at other volcanoes following much larger eruptions, was likely enhanced by lateral confinement of the channel within a narrow incised valley. A combination of at least one lahar and winter floods from frequent moderate-magnitude rainstorms and infrequent very large storms was responsible for flushing large volumes of sediment to the depositional reach. These conditions permitted a sedimentation response in the Sandy River that approached the magnitude of channel aggradation resulting elsewhere from large explosive eruptions and high-intensity rainfall regimes, despite the fact that the Sandy River aggradation was in response to an unremarkable dome-building eruption in a climate dominated by low to moderate rainfall intensities.

Impact of the 2008 Wenchuan earthquake in China on subsequent long-term debris flow activities in the epicentral area

NASA Astrophysics Data System (ADS)

Zhang, S.; Zhang, L. M.

2017-01-01

The 2008 Wenchuan earthquake triggered the largest number of landslides among the recent strong earthquake events around the world. The loose landslide materials were retained on steep terrains and deep gullies. In the period from 2008 to 2015, numerous debris flows occurred during rainstorms along the Provincial Road 303 (PR303) near the epicentre of the earthquake, causing serious damage to the reconstructed highway. Approximately 5.24 × 106 m3 of debris-flow sediment was deposited shortly after the earthquake. This paper evaluates the evolution of the debris flows that occurred after the Wenchuan earthquake, which helps understand long-term landscape evolution and cascading effects in regions impacted by mega earthquakes. With the aid of a GIS platform combined with field investigations, we continuously tracked movements of the loose deposit materials in all the debris flow gullies along an 18 km reach of PR303 and the characteristics of the regional debris flows during several storms in the past seven years. This paper presents five important aspects of the evolution of debris flows: (1) supply of debris flow materials; (2) triggering rainfall; (3) initiation mechanisms and types of debris flows; (4) runout characteristics; and (5) elevated riverbed due to the deposited materials from the debris flows. The hillslope soil deposits gradually evolved into channel deposits and the solid materials in the channels moved towards the ravine mouth. Accordingly, channelized debris flows became dominant gradually. Due to the decreasing source material volume and changes in debris flow characteristics, the triggering rainfall tends to increase from 30 mm h- 1 in 2008 to 64 mm h- 1 in 2013, and the runout distance tends to decrease over time. The runout materials blocked the river and elevated the riverbed by at least 30 m in parts of the study area. The changes in the post-seismic debris flow activity can be categorized into three stages, i.e., active, unstable, and recession.

Effect of Spatio-Temporal Variability of Rainfall on Stream flow Prediction of Birr Watershed

NASA Astrophysics Data System (ADS)

Demisse, N. S.; Bitew, M. M.; Gebremichael, M.

2012-12-01

The effect of rainfall variability on our ability to forecast flooding events was poorly studied in complex terrain region of Ethiopia. In order to establish relation between rainfall variability and stream flow, we deployed 24 rain gauges across Birr watershed. Birr watershed is a medium size mountainous watershed with an area of 3000 km2 and elevation ranging between 1435 m.a.s.l and 3400 m.a.s.l in the central Ethiopia highlands. One summer monsoon rainfall of 2012 recorded at high temporal scale of 15 minutes interval and stream flow recorded at an hourly interval in three sub-watershed locations representing different scales were used in this study. Based on the data obtained from the rain gauges and stream flow observations, we quantify extent of temporal and spatial variability of rainfall across the watershed using standard statistical measures including mean, standard deviation and coefficient of variation. We also establish rainfall-runoff modeling system using a physically distributed hydrological model: the Soil and Water Assessment Tool (SWAT) and examine the effect of rainfall variability on stream flow prediction. The accuracy of predicted stream flow is measured through direct comparison with observed flooding events. The results demonstrate the significance of relation between stream flow prediction and rainfall variability in the understanding of runoff generation mechanisms at watershed scale, determination of dominant water balance components, and effect of variability on accuracy of flood forecasting activities.

The RHYTMME system: an operational real-time warning and mapping system for flash floods, debris flows, landslide and rock falls in Southeastern France.

NASA Astrophysics Data System (ADS)

Fouchier, Catherine; Mériaux, Patrice; Atger, Frédéric; Ecrepont, Stéphane; Liébault, Frédéric; Bertrand, Mélanie; Bel, Coraline; Batista, Dominique; Azemard, Pierre; Saint-Martin, Clotilde; Javelle, Pierre

2016-04-01

Almost all municipalities of Southeastern France are concerned by natural hazards triggered by heavy rainfalls such as floods, debris flows, landslides and rock falls. Although some tools exist to forecast and monitor heavy rains and floods in France, their spatial resolution sometimes does not meet the needs of local risk managers who have to monitor events at a small spatial scale. In order to improve the risk management in the mountainous and Mediterranean areas of Southeastern France, Irstea and Météo-France have led the RHYTMME project. The goal of this project is to improve the ability to forecast and localize high-risk rainfall-induced hazards in the Provence-Alpes-Côte d'Azur administrative area. This goal is currently under achievement thanks to the implementation of a real-time warning and mapping system for rainfall induced natural hazards, fed by radar data and whose outputs are made available via the Internet to operators in charge of risk management (local and regional authorities, emergency and rescue services, road and rail networks managers, ...). This system provides maps which display in real-time: - the radar estimations of rainfall for different rain durations and at the spatial resolution of 1 km² (Westrelin et al., 2013), - the estimation of the scarcity of these rainfall estimations, also at the spatial resolution of 1 km², thanks to a comparison with threshold values provided by a regionalized stochastic hourly point rainfall generator (Arnaud et al., 2007), - an anticipation of the rivers discharges, computed at the outlet of 1700 watersheds of Southeastern France thanks to the AIGA warning system which combines a rainfall runoff model and an estimation of the scarcity of the discharges thanks to a comparison with threshold values (Javelle et al., 2014). Maps of susceptibility to debris flow, landslide and rock falls can also be displayed in the RHYTMME warning system along with the real time maps of rainfall hazard (Batista, 2013a, 2013b; Bertrand, 2014). It enables to identify, during intense events, the reaches the more likely to generate and/or to spread debris flow and the areas the more likely to generate landslide and/or rock falls. The RHYTMME warning and mapping system is now fully operational. It is currently being provided to local authorities (City councils, River boards, …) as well as State authorities in charge of risk managements in the Provence-Alpes-Côte d'Azur administrative area. Training sessions are organized in order to help these end-users to handle the system. References Arnaud P., Fine J.-A. and Lavabre J. (2007). An hourly rainfall generation model applicable to all types of climate. Atmospheric Research 85(2): 230-242. Batista D., Azémard P., Boutry M. (2013). Prévision de l'aléa glissement de terrain et analyse statistique des facteurs de prédisposition par l'outil SIG, sur la région Provence-Alpes-Côte d'Azur. Journées Aléas Gravitaires, 17 et 18/9/2013 - Grenoble, 11 p. Batista D., Azémard P., Rougé A.C., Dumalin M., Rault C. (2013). Prévision de l'aléa chute de blocs, analyse statistique des facteurs de prédisposition et des critères de déclenchement sur la région Provence-Alpes-Côte d'Azur. Journées Aléas Gravitaires, 17 et 18/9/2013 - Grenoble, 11 p. Bertrand M. (2014). Approches régionales de la susceptibilité torrentielle dans les Alpes du Sud. Thèse de Doctorat, École Normale Supérieure de Lyon, 162 pp. Javelle P., Demargne J., Defrance D., Pansu J., Arnaud P. (2014). Evaluating flash-flood warnings at ungauged locations using post-event surveys: A case study with the AIGA warning system. Hydrological Sciences Journal 59 (7): 1390-1402. Westrelin S., Mériaux P., Dalle S., Fradon B., Jamet G. (2013). Déploiement d'un réseau de radars pour anticiper les risques hydro-météorologiques, La Météorologie 8 (83): 69-79.

Benefits and limitations of using the weather radar for the definition of rainfall thresholds for debris flows. Case study from Catalonia (Spain).

NASA Astrophysics Data System (ADS)

Abancó, C.; Hürlimann, M.; Sempere, D.; Berenguer, M.

2012-04-01

Torrential processes such as debris flows or hyperconcentrated flows are fast movements formed by a mix of water and different amounts of unsorted solid material. They occur in steep torrents and suppose a high risk for the human settlements. Rainfall is the most common triggering factor for debris flows. The rainfall threshold defines the rainfall conditions that, when reached or exceeded, are likely to provoke one or more events. Many different types of empirical rainfall thresholds for landslide triggering have been defined. Direct measurements of rainfall data are normally not available from a point next to or in the surroundings of the initiation area of the landslide. For this reason, most of the thresholds published for debris flows have been established by data measured at the nearest rain gauges (often located several km far from the landslide). Only in very few cases, the rainfall data to analyse the triggering conditions of the debris flows have been obtained by weather (Doppler) radar. Radar devices present certain limitations in mountainous regions due to undesired reboots, but their main advantage is that radar data can be obtained for any point of the territory. The objective of this work was to test the use of the weather radar data for the definition of rainfall thresholds for debris-flow triggering. Thus, rainfall data obtained from 3 to 5 rain gauges and from radar were compared for a dataset of events occurred in Catalonia (Spain). The goal was to determine in which cases the description of the rainfall episode (in particular the maximum intensity) had been more accurate. The analysed dataset consists of: 1) three events occurred in the Rebaixader debris-flow monitoring station (Axial Pyrenees) including two hyperconcentrated flows and one debris flow; 2) one debris-flow event occurred in the Port Ainé ski resort (Axial Pyrenees); 3) one debris-flow event in Montserrat (Mediterranean Coastal range). The comparison of the hyetographs from the different devices showed that the reliability of the radar is higher for short, high intensity storms more than for long lasting, medium intensity ones. Additionally, the best fit corresponds to the situations where the storm nucleus is located near the source area of the debris flow. The results of the comparison between different rain gauges show similar trends. The ones located in the same valley as the debris flow usually show good results, but if there are orographic elements in-between the debris-flow torrent and the rain gauge or the distance is large, the results can imply a great error in the definition of rainfall intensity. Therefore, we can state that the reliability of the use of the weather radar to define rainfall thresholds is strongly depending on the type of the storm and the distance between the source area and the nucleus of the storm.

Effects of extreme rainfall events on the distribution of selected emerging contaminants in surface and groundwater: The Guadalete River basin (SW, Spain).

PubMed

Corada-Fernández, Carmen; Candela, Lucila; Torres-Fuentes, Nivis; Pintado-Herrera, Marina G; Paniw, Maria; González-Mazo, Eduardo

2017-12-15

This study is focused on the Guadalete River basin (SW, Spain), where extreme weather conditions have become common, with and alternation between periods of drought and extreme rainfall events. Combined sewer overflows (CSOs) occur when heavy rainfall events exceed the capacity of the wastewater treatment plants (WWTP), as well as pollution episodes in parts of the basin due to uncontrolled sewage spills and the use of reclaimed water and sludge from the local WWTP. The sampling was carried out along two seasons and three campaigns during dry (March 2007) and extreme rainfall (April and December 2010) in the Guadalete River, alluvial aquifer and Jerez de la Frontera aquifer. Results showed minimum concentrations for synthetic surfactants in groundwater (<37.4μg·L -1 ) during the first campaign (dry weather conditions), whereas groundwater contaminants increased in December 2010 as the heavy rainfall caused the river to overflow. In surface water, surfactant concentrations showed similar trends to groundwater observations. In addition to surfactants, pharmaceuticals and personal care products (PPCPs) were analyzed in the third campaign, 22 of which were detected in surface waters. Two fragrances (OTNE and galaxolide) and one analgesic/anti-inflammatory (ibuprofen) were the most abundant PPCPs (up to 6540, 2748 and 1747ng·L -1 , respectively). Regarding groundwater, most PPCPs were detected in Jerez de la Frontera aquifer, where a synthetic fragrance (OTNE) was predominant (up to 1285ng·L -1 ). Copyright © 2017 Elsevier B.V. All rights reserved.