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1

Impacts of Urbanization on Groundwater Quality and Recharge in a Semi-arid Alluvial Basin  

Technology Transfer Automated Retrieval System (TEKTRAN)

The management of groundwater resources is paramount in semi-arid regions experiencing urban development. In the southwestern United States, enhancing recharge of urban storm runoff has been identified as a strategy for augmenting groundwater resources. An understanding of how urbanization may impac...

2

Estimating the surface age of arid-zone alluvial fans using spaceborne radar data  

NASA Astrophysics Data System (ADS)

Alluvial fans constitute important recorders of tectonic and climatic signals. Thus, determining the age of alluvial deposits is a common and pivotal component in many quantitative studies of recent tectonic activity, past climatic variations and landscape evolution processes. In this study we build on the established relation between surface age and surface roughness and examine the use of radar backscatter data as a calibrated proxy for constraining the age of alluvial surfaces in such environments. This study was conducted in the hyper-arid environment of the southern Arava rift valley north of the Gulf of Aqaba. ALOS-PALSAR L-Band dual-polarized (i.e., HH, HV) data with different incidence angles (24°, 38°) and resolutions (6.25m, 12.5m) were examined for 11 alluvial surfaces, for which surface ages ranging from 5-160 ka were previously determined. As expected, radar backscatter in such low-relief hyper-arid desert environments responded primarily to SR at pixel-scales and below. Nonetheless, measured backscatter values for single pixels were found to be unsuitable proxies for surface age because of the natural variability in SR across alluvial units of a given age. Instead, we found the statistical properties of radar pixel populations within a given unit to be the most effective proxies for surface age. Our results show that the mean backscatter value within representativeROI's (region of interest) provided the best predictor for surface age: Lower mean backscatter values correlated well with older and smoother alluvial surfaces. The HHpolarized image with ~38° incidence angle and 6.25 m/pixel resolution allowed the best separation of surface ages. This radar-based approach allows us to quantitatively constrain the age of alluvial surfaces in the studied region at comparable uncertainty to that of "conventional" surface dating techniques commonly used.

Hetz, Guy; Mushkin, Amit; Blumberg, Dan G.; Baer, Gidi

2013-10-01

3

Unraveling fan-climate relationships: Milankovitch cyclicity in a Miocene alluvial fan (Teruel Basin, Spain)  

NASA Astrophysics Data System (ADS)

The role of climate change in alluvial fan sedimentation is often evident in geomorphological studies dealing with Quaternary successions, but remains hard to assess in the pre-Quaternary stratigraphic record, for which an additional obstacle is represented by detailed chronologies difficult to established within coarse clastic systems. The Teruel Basin (eastern Spain) is an extensional trough whose main tectonic activity spanned from late Oligocene to Pliocene times. Permanent internal drainage and a Mediterranean semi-arid climate made the basin and its sedimentary signatures highly sensitive to climate fluctuations, especially in terms of hydrological balance. Recent studies have proved orbital control on the development of facies sequences from low-energy, basinal settings in Teruel. In particular, high-resolution chronological and paleoclimatic information has been derived by orbital tuning of mudflat to ephemeral lake deposits in the Prado area (Villastar), linking basic facies rhythms to alternating, relatively humid/arid phases paced mainly by climatic precession. Clastic lobes from a coeval alluvial fan distally interfinger with this reference section. Stratigraphic relationships show how fan sedimentation patterns were also influenced by climate cyclicity. Highest volumes of debris transfer towards the distal mudflat repeatedly coincide with relatively humid periods. Furthermore, distal to medial fan outcrops feature prominent rhythms of distinct, alternating coarse and fine clastic packages. Such a highly organized architecture, unusual in alluvial fan successions, points to the influence of a rhythmic forcing mechanism which might have been climate variability, as evidenced by the adjacent reference section. Rather than on processes of sediment transport basinwards, climate change would have acted on sediment production and availability at the source, within the fan catchment.

Ventra, D.; Abels, H. A.; Hilgen, F. J.; de Boer, P. L.

2009-04-01

4

Interpretation of floodplain pollen in alluvial sediments from an Arid Region*1  

NASA Astrophysics Data System (ADS)

Pollen was collected from modern alluvium and from the atmosphere to document the nature and amount of paleoenvironmental information reflected by alluvial pollen chronologies. Results indicate that pollen in alluvium is a homogeneous mixture derived almost entirely from the floodplain itself. The few pollen grains derived from nonfloodplain plant communities and preserved in alluvial sediments are so well mixed that their frequencies no longer reflect the geographic distribution of the specific plant communities in which they originated. In contrast, the abundance of alluvial pollen grains, derived from the major floodplain taxa (Chenopodiineae, Ambrosia type), varies with summer and winter climate. This annual variation is preserved in alluvial pollen assemblages through a combination of processes within sedimentation basins involving discontinuous deposition events and mechanical pollen degradation. The high-frequency, wide-amplitude pollen variance in alluvial pollen assemblages contrasts with the low-frequency, narrow-amplitude pollen variance in sediments of lakes and ponds. The slight geographic variance in alluvial pollen assemblages, in contrast to the large variance in soil pollen, allows use of alluvial pollen to infer climate throughout the watershed in which pollen is sampled.

Solomon, Allen M.; Blasing, T. J.; Solomon, J. A.

1982-07-01

5

Variation in sedimentology and architecture of Eocene alluvial strata, Wind River and Washakie basins, Wyoming  

SciTech Connect

Eocene continental, alluvial strata of the Wind River Formation (Wind River Basin) and the Cathedral Bluffs Member of the Wasatch Formation (Washakie basin) provide two examples of Laramide intermontane basin aggradation. These alluvial sediments primarily represent overbank flood deposits marginal to channel complexes. Their sedimentology and architecture, although grossly similar, appear to vary somewhat with proximity to Laramide uplifts. In both cases, repetitive sedimentation on the floodplain produced a succession of depositional couplets, each composed of a light-gray sand overlain by a red clay-rich silt or sand. The lower sands are tabular bodies that, near their distal margins, taper discernibly. They commonly display planar and ripple-drift laminations. Upper clay-rich layers, which are laminated, are also generally tabular. Those floodplain strata depositional proximal to Laramide uplifts show little evidence of scouring prior to deposition of the next, overlying couplet. Most of these sedimentary layers, therefore, are laterally continuous (up to 2 km). This alluvial architecture results in relatively uniform porosity laterally within depositional units but variable porosity stratigraphically through the sequence. In contrast, alluvial sediments deposited farther from the Laramide uplifts have undergone sporadic incision (either during rising flood stage or subsequently) followed by aggradation. As a result, many of these floodplain couplets are discontinuous laterally and, hence, exhibit large-scale lateral variability in porosity. Both alluvial sequences have undergone similar types and extents of burial diagenesis.

Patterson, P.E.; Larson, E.E. (Univ. of Colorado, Boulder (United States))

1991-03-01

6

Orbital forcing in the early Miocene alluvial sediments of the western Ebro Basin, Northeast Spain  

NASA Astrophysics Data System (ADS)

Paleoclimatic reconstructions from terrestrial records are crucial to assess the regional variability of past climates. Despite the apparent direct connection between continental sedimentary environments and climate, interpreting the climatic signature in ancient non-marine sedimentary sequences is often overprinted by source-area related signals. In this regard, foreland basins appear as non-ideal targets as tectonically-driven subsidence and uplift play a major control on the distribution and evolution of sedimentary environments and facies. Foreland basins, however, often yield among the thickest and most continuous stratigraphic records available on continents. The Ebro Basin (north-eastern Spain) is of particular interest among the circum-mediterranean alpine foreland basins because it evolved into a land-locked closed basin since the late Eocene, leading to the accumulation of an exceptionally thick (>5500 m) and continuous sequence of alluvial-lacustrine sediments over a period of about 25 Myr. In this paper we present a detailed cyclostratigraphic study of a 115 m thick section in the Bardenas Reales de Navarra region (western Ebro Basin) in order to test orbital forcing in the Milankovitch frequency band. The study section corresponds to the distal alluvial-playa mud flats which developed in the central sector of the western Ebro Basin, with sediments sourced from both the Pyrenean and Iberian Ranges. Sediments consist of brown-red alluvial clay packages containing minor fine-grained laminated sandstones sheet-beds and channels, grey marls and thin bedded lacustrine limestones arranged in 10 to 20 m thick fining-upwards sequences. Red clayed intervals contain abundant nodular gypsum interpreted as representing a phase of arid and low lake level conditions, while grey marls and limestones indicate wetter intervals recording the expansion of the inner shallow lakes. A magnetostratigraphy-based chronology indicates that the Peñarroya section represents a time interval of about 500 kyr centered around chron C6r, although inferred absolute ages diverge depending on the assumed calibration of geomagnetic reversals with the astronomical time scale (Billups et al., 2004, Lourens et al., 2004). The section was sampled with a portable drill at regular intervals of about 30 cms, representing a time resolution of near 1 kyr. Spectral analysis of different measured parameters (lithology code, color, magnetic susceptibility and other rock magnetic parameters) revealed significant power at 20.4 m, 9.6 m and 4.2 m, which correspond to a ratio of 1:2.1:4.9 similar to that given by the Milankovitch cycles of eccentricity, obliquity and precession. Maximum power in the spetrum is focused in the eccentricity and obliquity bands while signal corresponding to precession is weakly expressed. The existing uncertainties in the astronomical tuning of the Early Miocene geomagnetic polarity time scale prevents us from using magnetostratigraphy to anchor the Peñarroya record with the astronomical solutions (Laskar et al., 2004). Instead, we have tried the expression of the eccentricity cycle to tune the Peñarroya section. We correlated the thick red clayed (dry phase) intervals with eccentricity minima, a phase relationship which is in agreement with that derived from earlier studies in marine and continental records from the Miocene of the Iberian plate (Abels et al., 2008, Sierro et al., 2000). The resulting tuning of the Peñarroya section yields an age for the base of geomagnetic chron C6r which fits with earlier work of Billups et al., (2004), while the top of C6r gives a significantly younger age. References Abels, H., Abdul Aziz, A., Calvo, J.P. and Tuenter, E., 2008. Shallow lacustrine carbonate microfacies document orbitally paced lake-level history in the Miocene Teruel Basin (North-East Spain), Sedimentology doi: 10.1111/j.1365-3091.2008.00976.x. Billups, K., Pälike, H., Channell, J.E.T., Zachos, J. and Shackleton, N.J., 2004. Astronomic calibration of the late Oligocene through early Miocene geomagnetic polarity time sca

Garces, M.; Larrasoaña, J. C.; Muñoz, A.; Margalef, O.; Murelaga, X.

2009-04-01

7

Occurrence of saltwater in the alluvial aquifer in the Boeuf-Tensas Basin, Arkansas  

USGS Publications Warehouse

The occurrence of saline water in the alluvial aquifer in the Boeuf-Tensas basin in southeastern Arkansas has been of increasing concern. A band of saline water containing chloride concentrations of greater than 50 milligrams per liter extends through the entire length of the basin. The most severely affected area is located in the southern part of the basin where chloride concentrations are as high as 1,360 milligrams per liter. The origin of the saline water in the alluvial aquifer is not definitely known, but can probably be attributed at least in part, to both upward movement from the Arkansas River. Upward instrusion of saline ground water has probably occurred through one or more of the following: 1) leakage where the Jackson confining unit is thinned or absent, 2) leakage along a fault, and 3) movement through abandoned oil and gas test holes. (USGS)

Fitzpatrick, D.J.

1985-01-01

8

Extreme Flood-Driven Dynamics of a mixed bedrock-alluvial Influenced Semi-Arid River  

NASA Astrophysics Data System (ADS)

Many of the large rivers draining southern Africa are characterised by incised bedrock ';macrochannels' cut 10-20 m into ancient planation surfaces but with variable amounts of unconsolidated sediment infill. Variations in lithology, structure, flow regime, sediment supply, and vegetation assemblages have created morphologically diverse river systems, many of which have been characterised by extended periods of alluviation on an historic timescale, thereby leading to the development of an increasingly alluviated set of channel types that commonly mask the underlying bedrock. However, cyclone-driven extreme flows are known to cause extensive erosion along these systems and may exert the primary control over their morphologic development. This paper reports on two significant cyclone events (2000 and 2012) that have impacted on the rivers of the Kruger National Park, with floods on the Sabie and Olifants estimated as among the largest documented Holocene floods for any South African river. Prior to the floods, both rivers displayed a diverse but well-ordered set of channel types (e.g. braided, anastomosed), with considerable lengths of both systems exhibiting fully alluvial conditions. Evaluation of post-flood aerial imagery has shown that the extreme flows have stripped this sediment, exposing and eroding the underlying weathered bedrock, particularly along the Olifants. This response suggests that although alluviation occurs over short timescales, the systems remain highly susceptible to alluvial and bedrock erosion during extreme floods. This is demonstrated by the results of a 2D hydraulic modelling study of the rivers. Simulation of the peak flood flow conditions shows that extreme shear stresses capable of eroding cohesive, well-vegetated sediments were predicted extensively within the macrochannels. Where remnant deposits remained from the 2000 floods, these areas were seen to be particularly vulnerable to erosion in the 2012 floods, due principally to their increased exposure to fluid forces. The ephemeral nature of the sediment infill is also supported by OSL dating, with preliminary ages from remnant bars, islands and floodplains suggesting that no deposits older than around 500 years can be found along the rivers. Together, the results imply that although periods of extensive alluviation may have been witnessed historically, on a longer (late Quaternary) timescale the alluvial morphologies are frequently reworked, with the geological setting and extreme climatic influence creating conditions conducive to the continuing erosion and development of the bedrock macrochannel template.

Entwistle, N. S.; Heritage, G. L.; Tooth, S.; Milan, D. J.

2013-12-01

9

Groundwater and Surface Water Interaction of Several Irrigation Systems in the Mississippi River Basin Alluvial Aquifer  

NASA Astrophysics Data System (ADS)

The Lower Mississippi River Basin alluvial aquifer provides irrigation water for agriculture in most of eastern Arkansas, western Tennessee, southeastern Missouri, western Mississippi and northeastern Louisiana. The alluvial aquifer depth to water has been declining by approximately 1 foot per year due to unsustainable pumping levels. Replacing groundwater with surface water sources in the Lower Mississippi River Basin is one of the many solutions to declining groundwater stores that has taken root in the region, especially in eastern Arkansas. Surface water irrigation systems consist of an on-farm reservoir and tailwater recovery. The reservoir is used to store water for later use during wet periods of the year and the tailwater recovery creates a closed basin of the irrigation system, allowing for use and re-use of irrigation water. Several irrigation systems were instrumented to further understand the interaction between surface water and groundwater in alluvial aquifer region. Three reservoirs, 9 streams and ditches, and 8 groundwater wells were instrumented in fall of 2011. Groundwater potentiometric surface under the storage reservoirs showed a rebound while a potentiometric surface falls sharply south and west moving away from the storage reservoirs. Preliminary results from the findings from these sites are presented.

Reba, M. L.; Rigby, J.; Czarnecki, J.; Rawlings, L.

2013-12-01

10

Geologic Characterization of Young Alluvial Basin-Fill Deposits from Drill Hole Data in Yucca Flat, Nye County, Nevada.  

SciTech Connect

Yucca Flat is a topographic and structural basin in the northeastern part of the Nevada Test Site (NTS) in Nye County, Nevada, that has been the site of numerous underground nuclear tests; many of these tests occurred within the young alluvial basin-fill deposits. The migration of radionuclides to the Paleozoic carbonate aquifer involves passage through this thick, heterogeneous section of Tertiary and Quaternary rock. An understanding of the lateral and vertical changes in the material properties of young alluvial basin-fill deposits will aid in the further development of the hydrogeologic framework and the delineation of hydrostratigraphic units and hydraulic properties required for simulating ground-water flow in the Yucca Flat area. This report by the U.S. Geological Survey, in cooperation with the U.S. Department of Energy, presents data and interpretation regarding the three-dimensional variability of the shallow alluvial aquifers in areas of testing at Yucca Flat, data that are potentially useful in the understanding of the subsurface flow system. This report includes a summary and interpretation of alluvial basin-fill stratigraphy in the Yucca Flat area based on drill hole data from 285 selected drill holes. Spatial variations in lithology and grain size of the Neogene basin-fill sediments can be established when data from numerous drill holes are considered together. Lithologic variations are related to different depositional environments within the basin including alluvial fan, channel, basin axis, and playa deposits.

Donald S. Sweetkind; Ronald M. Drake II

2007-01-22

11

Evaluation of groundwater recharge in Choushui River alluvial fan and Mingchu Basin for specific rainfall events  

NASA Astrophysics Data System (ADS)

Sound groundwater resources planning and management are lack in the Choushui River alluvial fan, resulting in the occurrence of serious land subsidence and seawater intrusion. Even the disasters induced by overpumping of groundwater pose a potential threat on the Taiwan High Speed Rail. In addition to improving the water resources management in the alluvial fan, the development of groundwater resources in the neighboring hills. Mingchu Basin, which is located on the midstream segment of the Choushui River and comprised of the gravel formation of Pleistocene, is an effective solution to resolve the problem in limited water resources. Moreover, the Dongpurui River and Qingshui River both converge into Choushui River in this basin. Because of wide drainage areas and good hydrogeological conditions, the Mingchu Basin is considered a high potential recharging region of groundwater. This work is to evaluate the groundwater recharge in the Choushui River alluvial fan and Mingchu Basin, using the WASH123D model equipped with the Groundwater Modeling System (GMS) to simulate the interaction of surface water and groundwater for specific five rainfall events. This study particularly focuses on the simulation of the groundwater flow, and evaluates the effect of different rainfall events on the groundwater recharge. First, to meet in-situ hydrogeological structure and hydraulic parameters, the GMS is used to construct hydrogeological database, mesh, hydrogeological parameters, initial condition and boundary conditions. Then, simulated parameters, such as hydraulic conductivity and pumping rates, need to be calibrated and verified in the model. After the calibration and verification, the simulated groundwater flow can reflect actual groundwater situation. Finally, when specific five rainfall events impose on the ground, groundwater recharge can be determined using the groundwater model.

Lin, Zong Sheng; Chen, Jui-Sheng; Jang, Cheng-Shin

2014-05-01

12

Sedimentary and tectonic evolution of Plio Pleistocene alluvial and lacustrine deposits of Fucino Basin (central Italy)  

NASA Astrophysics Data System (ADS)

The Fucino Basin was the greatest lake of the central Italy, which was completely drained at the end of 19th century. The basin is an intramontane half-graben filled by Plio-Quaternary alluvial and lacustrine deposits located in the central part of the Apennines chain, which was formed in Upper Pliocene and in Quaternary time by the extensional tectonic activity. The analysis of the geological surface data allows the definition of several stratigraphic units grouped in Lower Units and Upper Units. The Lower Units (Upper Pliocene) are exposed along the northern and north-eastern basin margins. They consist of open to marginal lacustrine deposits, breccia deposits and fluvial deposits. The Upper Units (Lower Pliocene-Holocene) consist of interbedded marginal lacustrine deposits and fluvial deposits; thick coarse-grained fan-delta deposits are interfingered at the foot of the main relief with fluvial-lacustrine deposits. Most of the thickness of the lacustrine sequences (more than 1000-m thick) is buried below the central part of the Fucino Plain. The basin is bounded by E-W, WSW-ENE and NW-SE fault systems: Velino-Magnola Fault (E-W) and Tremonti-Celano-Aielli Fault (WSW-ENE) and S. Potito-Celano Fault (NW-SE) in the north; the Trasacco Fault, the Pescina-Celano Fault and the Serrone Fault (NW-SE) in the south-east. The geometry and kinematic indicators of these faults indicate normal or oblique movements. The study of industrial seismic profiles across the Fucino Basin gives a clear picture of the subsurface basin geometry; the basin shows triangular-shaped basin-fill geometry, with the maximum deposits thickness toward the main east boundary fault zones that dip south-westward (Serrone Fault, Trasacco Fault, Pescina-Celano Fault). On the basis of geological surface data, borehole stratigraphy and seismic data analysis, it is possible to recognize and to correlate sedimentary and seismic facies. The bottom of the basin is well recognized in the seismic lines available from the good and continuous signals of the top of Meso-Cenozoic carbonate rocks. The shape of sedimentary bodies indicates that the filling of the basin was mainly controlled by normal slip along the NW-SE boundary faults. In fact, the continental deposits are frequently in on-lap contact over the carbonate substratum; several disconformable contacts occurred during the sedimentary evolution of the basin. The main faults (with antithetic and synthetic fault planes) displace the whole sedimentary sequence up to the surface indicating a recent faults' activity (1915 Avezzano earthquake, Ms=7.0). The stratigraphic and tectonic setting of the Fucino Basin and neighboring areas indicates that the extensional tectonic events have had an important role in driving the structural-sedimentary evolution of the Plio-Quaternary deposits. The geometry of the depositional bodies, of the fault planes and their relationships indicate that the Fucino Basin was formed as a half-graben type structure during Plio-Quaternary extensional events. Some internal complexities are probably related to the fold-and-thrust structures of the Apenninic orogeny formed in Messinian time, in this area, and to a different activity timing of the E-W and WSW-ENE fault systems and the NW-SE fault systems. We believe, based on the similarity of the surface characteristics, that the structural setting of the Fucino Basin can be extrapolated to the other great intramontane basins in Central Italy (e.g. Rieti, L'Aquila, Sulmona, Sora, Isernia basins).

Cavinato, Gian Paolo; Carusi, Claudio; Dall'Asta, Massimo; Miccadei, Enrico; Piacentini, Tommaso

2002-04-01

13

Modern sediment yield compared to geologic rates of sediment production in a semi-arid basin, New Mexico: Assessing the human impact  

USGS Publications Warehouse

In the semi-arid Arroyo Chavez basin of New Mexico, a 2.28 km2 sub-basin of the Rio Puerco, we contrasted short-term rates (3 years) of sediment yield measured with sediment traps and dams with long-term, geologic rates (???10 000 years) of sediment production measured using 10Be. Examination of erosion rates at different time-scales provides the opportunity to contrast the human impact on erosion with background or geologic rates of sediment production. Arroyo Chavez is grazed and we were interested in whether differences in erosion rates observed at the two time-scales are due to grazing. The geologic rate of sediment production, 0-27 kg m-2 a -1 is similar to the modern sediment yields measured for geomorphic surfaces including colluvial slopes, gently sloping hillslopes, and the mesa top which ranged from 0.12 to 1.03 kg m -2 a-1. The differences between modern sediment yield and geologic rates of sediment production were most noticeable for the alluvial valley floor, which had modern sediment yields as high as 3.35 kg m-2 a-1. The hydraulic state of the arroyo determines whether the alluvial valley floor is aggrading or degrading. Arroyo Chavez is incised and the alluvial valley floor is gullied and piped and is a source of sediment. The alluvial valley floor is also the portion of the basin most modified by human disturbance including grazing and gas pipeline activity, both of which serve to increase erosion rates. ?? 2004 John Wiley and Sons, Ltd.

Gellis, A.C.; Pavich, M.J.; Bierman, P.R.; Clapp, E.M.; Ellevein, A.; Aby, S.

2004-01-01

14

Response of active tectonics on the alluvial Baghmati River, Himalayan foreland basin, eastern India  

NASA Astrophysics Data System (ADS)

Active tectonics in a basin plays an important role in controlling a fluvial system through the change in channel slope. The Baghmati, an anabranching, foothills-fed river system, draining the plains of north Bihar in eastern India has responded to ongoing tectonic deformation in the basin. The relatively flat alluvial plains are traversed by several active subsurface faults, which divide the area in four tectonic blocks. Each tectonic block is characterized by association of fluvial anomalies viz. compressed meanders, knick point in longitudinal profiles, channel incision, anomalous sinuosity variations, sudden change in river flow direction, river flow against the local gradient and distribution of overbank flooding, lakes, and waterlogged area. Such fluvial anomalies have been identified on the repetitive satellite images and maps and interpreted through DEM and field observations to understand the nature of vertical movements in the area. The sub-surface faults in the Baghmati plains cut across the river channel and also run parallel which have allowed us to observe the effects of longitudinal and lateral tilting manifested in avulsions and morphological changes.

Jain, Vikrant; Sinha, R.

2005-09-01

15

Alluvial fan response to climatic change: Insights from numerical modeling (Invited)  

Microsoft Academic Search

Alluvial fans in the western U.S. exhibit a regionally correlative sequence of Plio-Quaternary deposits. Cosmogenic and U-series dating has greatly improved the age control on these deposits and their associated terraces and generally strengthened the case for aggradation during humid-to-arid transitions. Still, the linkages between climate change, upland basin response, and alluvial fan response are not well constrained. Fans may

J. D. Pelletier

2009-01-01

16

Palaeohydrological and palaeoecological studies on South Cameroonian alluvial sedimentary basins - New evidence on the palaeoenvironmental evolution of western Central Africa since the Late Pleistocene  

NASA Astrophysics Data System (ADS)

A new valuable and innovative contribution will be presented to ascertain the timing and extension of climatic and ecological changes in western equatorial Africa. Main focus is laid on the dynamics of climate, fluvial systems and the high sensitive tropical ecosystems (dense evergreen and semi-deciduous rain forest and savanna-rain forest margin) since the Late Pleistocene (~50 kyrs. BP). For this purpose extended fieldworks were carried out in South Cameroon (2004-2008) by the ReSaKo-Project (sub-project of DFG-Project 510) with abundant investigations on alluvial sedimentary basins of equatorial tropical fluvial systems. Suitable alluvial sediment-archives for palaeoenvironmental research were uncovered along selected braiding, meandering and anabranching/anastomosing reaches of major southwestern, into the Gulf of Guinea (Ntem, Nyong and Sanaga) and southeastern, into the Congo basin (Boumba, Dja and Ngoko) draining rivers (RUNGE et al. 2006, SANGEN 2008). Among geomorphological investigations and cross section discussions, 150 corings (Edelman, 20 cm layers) reaching maximum depths of 550 cm were carried out on river benches, levees, cut-off and periodical branches, islands and terraces as well as in seasonal inundated floodplains and backswamps. Corresponding sedimentary profiles and catenae recovered multilayered, sandy to clayey alluvia containing sedimentary form-units and palaeosurfaces which contribute to the reconstruction of palaeoenvironmental conditions in western equatorial Africa. Several (59) radiocarbon (AMS) dated samples (Erlangen and Lecce) from fossil organic layers and macro-rests embedded in these units yielded Late Pleistocene to recent ages (14C-ages around 48 to 0.2 kyrs. BP), spanning also the Last Glacial Maximum (LGM) and Holocene record. Abrupt grain-size modifications and alternating form-units (sandy and clayey layers, palaeosurfaces) in the stratigraphic records display fluctuations in the fluvial-morphological response of the fluvial systems to climatic variability and other extrinsic and intrinsic impacts. Although the sedimentary record varies among the studied river reaches, fossil organic sediment layers (palaeosurfaces) containing valuable proxy data were found in almost all alluvia basins of examined southern Cameroonian rivers. Around 56 ^13C-values corresponding to the dated samples (-31.4 to -18.0 ) evidence that despite major disturbances of the African rain forest over geological times (MALEY 2001) mainly rain forest ecosystems have prevailed during the corresponding time periods, presumably as gallery forests, which were able to persist in this fluvial habitat ("fluvial refuge"), even during arid periods (e.g. LGM). The results are consistent with earlier findings from lacustrine (SERVANT & SERVANT-VILDARY 2000), marine (WELDEAB et al. 2007) and additional sediment archives (GASSE et al. 2008) and will add additional insights and information to the unravelling of the complex respond of the African monsoon, the Central African ecosystems and fluvial systems to Late Quaternary climatic and environmental fluctuations within a globally teleconnected system. References: GASSE, F., CHALIé, F., VINCENS, A., WILLIAMS, M.A.J. & WILLIAMSON, D. (2008): Climatic patterns in equatorial and southern Africa from 30,000 to 10,000 years ago reconstructed from terrestrial and near-shore proxy data. Quaternary Science Reviews, 27 (25-26), 2316-2340. MALEY, J. (2001): The impact of arid phases on the African rain forest through geological history. In: WEBER, W., WHITE, L., VEDDER, A., NAUGHTON-TREVES, L. (Eds.): African rain forest ecology and conservation - An interdisciplinary perspective. Yale University Press, New Haven, 68-87. RUNGE, J., EISENBERG, J., SANGEN, M. (2006): Geomorphic evolution of the Ntem alluvial basin and physiogeographic evidence for Holocene environmental changes in the rain forest of SW Cameroon (Central Africa) - preliminary results. Z. Geomorph. N.F., Suppl. Bd. 145, 63-79. SERVANT, M. & SERVANT-VILDARY, S. (2000): Dynamique à long terme des

Sangen, M.

2009-04-01

17

Changes in alluvial architecture associated with Eocene hyperthermals: Preliminary results from the Bighorn Basin Coring Project  

NASA Astrophysics Data System (ADS)

The Paleocene-Eocene Thermal Maximum (PETM) was followed by two lesser hyperthermal events: ETM2 and H2 both at ~53.7 Ma. The carbon isotope excursion for ETM2 was approximately half that of the PETM and the H2 excursion even smaller, indicating lower increases in temperature than during the PETM. The paleohydrologic responses to these events are less well understood than the response to PETM warming. Although the ETM2 and H2 events are better known from marine than continental strata, both events have been identified from outcrops of the alluvial Willwood Formation from the Deer Creek and Gilmore Hill areas of the Bighorn Basin, Wyoming (Abels et al., 2012). Here, we analyze two cores drilled from stratigraphically equivalent Willwood strata from Gilmore Hill. The cores provide an opportunity to examine the impact of these events on the architecture of fluvial strata. Willwood strata are composed largely of channel sandstones, heterolithic deposits generated by channel avulsion, and paleosols that formed on overbank deposits. The paleosols provide qualitative and quantitative information on changes in soil moisture and precipitation through this interval. The cores also show a distinct change in the stacking of paleosols The core is subdivided into three parts: (1) the lowest ~third has thinner, more densely spaced paleosols, (2) the middle has thicker paleosols that are more widely spaced, and (3) the upper third has thicker and more common channel sandstones interspersed with avulsion deposits and fewer red paleosols; this corresponds to the hyperthermal interval. In particular, a ~20 m thick sandstone complex caps the section and appears to truncate part of the hyperthermal interval. Although vertical variations in alluvial architecture can reflect tectonic or climatic change, the correspondence of the sandstone-rich part of the cores with the hyperthermals suggests climate was the major control on their formation. Thick purple paleosols associated with the hyperthermals at Deer Creek suggest wetter conditions, and our preliminary interpretation is that a change to wetter conditions caused increased discharge and deposition of coarser (sandy) sediment. The thick sandstone complex at Gilmore Hill is underlain by paleosols with abundant calcrete nodules, which indicate drier soil conditions prior to deposition of the sandstone, and the change from drier to wetter conditions probably also caused increased sediment yield.

Acks, R.; Kraus, M. J.

2012-12-01

18

Avulsion Clusters in Alluvial Systems: An Example of Large-Scale Self-Organization in Ancient and Experimental Basins  

NASA Astrophysics Data System (ADS)

The stratigraphic record of at least some alluvial basins exhibits a spatial structure that may reflect long time- scale (103-105 yr in natural basins) autogenic organization of river avulsions. Current models of avulsion-dominated alluvial sequences emphasize the spatial and temporal distribution of coarse-grained channel-belt deposits amid fine-grained floodplain materials. These models typically assume that individual avulsions move, either randomly or deterministically, to low spots distributed throughout the model space. However, our observations of ancient deposits and experimental stratigraphy indicate a previously unrecognized pattern of channel-belt organization, where clusters of closely-spaced channel-belt deposits are separated from each other by extensive intervals of overbank deposits. We explore potential causes of and controls on avulsion clustering with outcrop and subsurface data from Late Cretaceous/Early Paleogene fluvial deposits in the Rocky Mountains (including the Ferris, Lance, and Fort Union formations of Wyoming) and results of physical stratigraphy experiments from the St. Anthony Falls Lab, University of Minnesota. We use Ripley's K-function to determine the degree and scales of clustering in these basins with results that show moderate statistical clustering in experimental deposits and strong clustering in the Ferris Formation (Hanna Basin, Wyoming). External controls (base level, subsidence rate, and sediment/water supplies) were not varied during the experiment, and therefore not factors in cluster formation. Likewise, the stratigraphic context of the ancient system (including the absence of incised valleys and lack of faulting) suggests that obvious extrinsic controls, such as base level change and local tectonics, were not major influences on the development of clusters. We propose that avulsion clusters, as seen in this study, reflect a scale of self-organization in alluvial basins that is not usually recognized in stratigraphy. However cursory examination of other ancient systems suggests that such structure may be common in the rock record. Understanding mechanisms driving avulsion clustering will shed light on the dominant processes in alluvial basins over long time scales. Furthermore, characterizing autogenic avulsion clusters will be an important factor to consider when interpreting allogenic signals in ancient basin fills.

Hajek, E.; Heller, P.; Huzurbazar, S.; Sheets, B.; Paola, C.

2006-12-01

19

Generalized Diffuse Field Within a 2d Alluvial Basin: a Numerical Example  

NASA Astrophysics Data System (ADS)

Since the pioneering work of Aki (1957), the seismic noise has been used to infer the wave velocity distribution of soil formations. Later, diffuse-field concepts from room acoustics began to be used in elastodynamics by Weaver (1982) and flourished in many applications thanks to the contributions of Campillo and coworkers. It was established that diffusion like regimes are obtained when the field is produced by equipartitioned, uniform illumination. Within an elastodynamic diffuse-field the average correlation of the displacement field between two stations is proportional to the Green function of the system for those points. Usually, the surface waves can be interpreted by means of the retrieved Green function, from which very important information about the properties in depth can be obtained. Seismic noise and coda are frequently considered as diffuse-fields. This assumption is well supported by ideas of multiple scattering of waves and the resultant energy equipartition. There are few examples of numerically generated diffuse-fields. Some are based on random distributed forces (e.g. Sánchez-Sesma et al., 2006), while others used a set of plane waves with varying incidence angles and polarization (e.g. Sánchez-Sesma and Campillo 2006; Kawase et al. 2011). In this work we generate numerically a diffuse field within the Kawase and Aki (1989) 2D model using a random set of independent and uncorrelated incident plane P, SV and Rayleigh waves. For the simulations we use the indirect boundary element method (IBEM). Thus, we obtained the Green function for pairs of receivers by averaging correlations between different stations on the surface. In order to validate our results we compute the model's Green function as the response for a unit point load using the IBEM. Our numerical experiment provides guidelines for actual calculations of earthquakes in real alluvial basins.

Molina Villegas, J.; Baena, M.; Piña, J.; Perton, M.; Suarez, M.; Sanchez-Sesma, F. J.

2013-05-01

20

Tectonic controls of the North Anatolian Fault System (NAFS) on the geomorphic evolution of the alluvial fans and fan catchments in Erzincan pull-apart basin; Turkey  

NASA Astrophysics Data System (ADS)

The Erzincan pull-apart basin is located in the eastern section of the North Anatolian Fault System (NAFS). The tectonic evolution of this basin is mostly controlled by strike slip master faults of the NAFS. This study examines the topography-structure relationships in an effort to evaluate the tectonic signatures in the landscape, paying special attention to recent tectonic activity. In the study, the main focus is on the tectonic controls of the NAFS on the geomorphic evolution of alluvial fans and fan catchments in the Erzincan pull-apart basin. The observations of the amount of tilting of the alluvial fans (?) and its relation with morphometric (Asymmetry Factor (AF), Hypsometric Integral (HI), Fractal analysis of drainage networks (D)) properties of the fan catchments provide valuable information about the tectonic evolution of the basin area. The results of the analyses showed that the alluvial fan and fan catchment morphology in the pull-apart basin are mainly controlled by the ongoing tectonic activity of the NAFS. The fault system in the basin has controlled the accommodation space by causing differential subsidence of the basin, and aggradation processes by causing channel migration, channel incision and tilting the alluvial fans.

Sarp, Gulcan

2015-02-01

21

Silcrete and alunite genesis in alluvial palaeosols (late Cretaceous to early Palaeocene, Duero basin, Spain)  

NASA Astrophysics Data System (ADS)

An extensive formation of silcretes occurs in the upper half of a late Cretaceous-to-Palaeocene Siderolithic Unit consisting of conglomerates, sandstones and sandy mudstones along the western margin of the Tertiary Duero basin (Spain). The unit is arranged in fining-upward sequences that were deposited in a fluvial braided system with floodplains subject to periodic events of exposure and drying out. The original mineralogy of the Siderolithic Unit is seen in the less altered levels, where it consists of quartz, illite-white mica, kaolinite and, at the top of the unit, K-feldspar, all coming from the palaeoalteration mantles developed on the metasediments of the Variscan Basement. The unit is characterized by a marked development of alluvial palaeosols at the uppermost part of each sequence. At field scale, the pedogenic structures and features are evident from the mottled pattern, burrowing, cracking planes and root traces; at micromorphological scale, an intense development of birefringent fabrics is seen in clays. Micas and feldspars show evidence of alteration due to hydrolysis, while the more resistant quartz grains show common corrosion gulfs and have become the only surviving elements in the most silicified beds. The neoformed minerals are related to the pedodiagenetic processes developed on the floodplains. The main neoformed phase is opal (probably amorphous silica in origin that aged to opal-CT), which ranges from local cementations in pores to an almost complete replacement of the rock, specially the finest components (matrix). Kaolinite is the most abundant neoformed clay. Locally, veinlets of alunite accompany the opalized levels. All the processes described occurred in a seasonal tropical climate. During dry episodes, strong evaporation resulted in an increase in pH, favouring the hydrolysis of the original silicates. The paucity of Mg 2+ and Ca 2+ in the groundwater would have favoured the increase in pH. In ensuing wetter periods, pHs fell rapidly, resulting in the precipitation of kaolinite and also favouring the precipitation of opal and alunite. The alunite could have formed either by oxidation of the iron sulphides developed in reducing areas of the flood plains or by evaporitic concentration of sulphate in Ca 2+- and Mg 2+-free groundwaters.

Blanco, J. A.; Armenteros, I.; Huerta, P.

2008-11-01

22

Mapping and assessment of degraded land in the Heihe River Basin, arid northwestern China  

PubMed Central

Land degradation is a great threat in the Heihe River Basin, located in the arid inland of northwestern China and land desertification is one of the main aspects of environmental changes in this basin. Previous studies have focused on water resource utilization and soil erosion, but the status of degraded land in the Heihe River Basin, such as its distribution, extent and precise characteristics is often inadequately known. Based on field observations and TM images from the year 2003, this study provides classification and evaluation information concerning the degraded land in the basin of the Heihe River. There are five types of degraded land types in the Heihe River Basin: water eroded in the southern mountains, sandified and vegetation degraded near the oases, aridized in the low reaches, and salinized in the lowlands. The total degraded area covers 29,355.5 km2, 22.58% of the land in the study area. Finally, degraded land in the Heihe River Basin was evaluated according to changes in the physical structure and chemical components of soils, land productivity, secondary soil salt, and water conditions.

Qi, Shanzhong; Cai, Yumin

2007-01-01

23

S2-Project: Near-fault earthquake ground motion simulation in the Sulmona alluvial basin  

NASA Astrophysics Data System (ADS)

Recently the Italian Department of Civil Protection (DPC), in cooperation with Istituto Nazionale di Geofisica e Vulcanologia (INGV) has promoted the 'S2' research project (http://nuovoprogettoesse2.stru.polimi.it/) aimed at the design, testing and application of an open-source code for seismic hazard assessment (SHA). The tool envisaged will likely differ in several important respects from an existing international initiative (Open SHA, Field et al., 2003). In particular, while "the OpenSHA collaboration model envisions scientists developing their own attenuation relationships and earthquake rupture forecasts, which they will deploy and maintain in their own systems" , the main purpose of S2 project is to provide a flexible computational tool for SHA, primarily suited for the needs of DPC, which not necessarily are scientific needs. Within S2, a crucial issue is to make alternative approaches available to quantify the ground motion, with emphasis on the near field region. The SHA architecture envisaged will allow for the use of ground motion descriptions other than those yielded by empirical attenuation equations, for instance user generated motions provided by deterministic source and wave propagation simulations. In this contribution, after a brief presentation of Project S2, we intend to illustrate some preliminary 3D scenario simulations performed in the alluvial basin of Sulmona (Central Italy), as an example of the type of descriptions that can be handled in the future SHA architecture. In detail, we selected some seismogenic sources (from the DISS database), believed to be responsible for a number of destructive historical earthquakes, and derive from them a family of simplified geometrical and mechanical source models spanning across a reasonable range of parameters, so that the extent of the main uncertainties can be covered. Then, purely deterministic (for frequencies < 2Hz) and hybrid deterministic- stochastic source and propagation simulations are carried out for different fault rupture scenarios (but including important features such as the dominant near-surface geology), and the results in terms of representative ground motion parameters appropriately enveloped. The fully 3D problem is solved using the Spectral Element (SE) method, extensively published by Faccioli and his co-workers, and Quarteroni and co- workers, starting from 1996, and the computational code GeoELSE (http://GeoELSE.stru.polimi.it/). Finally, numerical results are compared with available data and attenuation relationships of peak values of ground motion in the near-fault regions elsewhere. Based on the results of this work, the unfavorable interaction between fault rupture, radiation mechanism and complex geological conditions may give rise to large values of peak ground velocity (exceeding 1 m/s) even in low-to-moderate seismicity areas, and therefore increase considerably the level of seismic risk, especially in highly populated and industrially active regions, such as the Central Italy.

Faccioli, E.; Stupazzini, M.; Galadini, F.; Gori, S.

2008-12-01

24

Occurrence of volcanic ash in the Quaternary alluvial deposits, lower Narmada basin, western India  

Microsoft Academic Search

This communication reports the occurrence of an ash layer intercalated within the late Quaternary alluvial succession of the\\u000a Madhumati River, a tributary of the lower Narmada River. Petrographic, morphological and chemical details of glass shards\\u000a and pumice fragments have formed the basis of this study. The ash has been correlated with the Youngest Toba Tuff. The finding\\u000a of ash layer

Rachna Raj

2008-01-01

25

Predicting the Affects of Climate Change on Evapotranspiration and Agricultural Productivity of Semi-arid Basins  

NASA Astrophysics Data System (ADS)

Many arid and semi-arid regions around the world are experiencing water shortages that have become increasingly problematic. Since the late 1800s, upstream diversions in Nevada's Walker River have delivered irrigation supply to the surrounding agricultural fields resulting in a dramatic water level decline of the terminal Walker Lake. Salinity has also increased because the only outflow from the lake is evaporation from the lake surface. The Heihe River basin of northwestern China, a similar semi-arid catchment, is also facing losses from evaporation of terminal locations, agricultural diversions and evapotranspiration (ET) of crops. Irrigated agriculture is now experiencing increased competition for use of diminishing water resources while a demand for ecological conservation continues to grow. It is important to understand how the existing agriculture in these regions will respond as climate changes. Predicting the affects of climate change on groundwater flow, surface water flow, ET and agricultural productivity of the Walker and Heihe River basins is essential for future conservation of water resources. ET estimates from remote sensing techniques can provide estimates of crop water consumption. By determining similarities of both hydrologic cycles, critical components missing in both systems can be determined and predictions of impacts of climate change and human management strategies can be assessed.

Peri, L.; Tyler, S. W.; Zheng, C.; Pohll, G. M.; Yao, Y.

2013-12-01

26

Fault-sourced alluvial fans and their interaction with axial fluvial drainage: An example from the Plio-Pleistocene Upper Valdarno Basin (Tuscany, Italy)  

NASA Astrophysics Data System (ADS)

The present study deals with the fault-sourced, alluvial-fan deposits of the Plio-Pleistocene Upper Valdarno Basin (Northern Apennines, Italy). Different phases of alluvial fan aggradation, progradation and backstep are discussed as possible effects of the interaction among fault-generated accommodation space, sediment supply and discharge variations affecting the axial fluvial drainage. The Upper Valdarno Basin, located about 35 km SE of Florence, is filled with 550 m palustrine, lacustrine and alluvial deposits forming four main unconformity-bounded units (i.e. synthems). The study alluvial-fan deposits belong to the two uppermost synthems (Montevarchi and Torrente Ciuffenna synthems) and are Early to Middle Pleistocene in age. These deposits are sourced from the fault-bounded, NE margin of the basin and interfinger with axial fluvial deposits. Alluvial fan deposits of the Montevarchi Synthem consist of three main intervals: i) a lower interval, which lacks any evidence of a depositional trend and testify balance between the subsidence rate (i.e. fault activity) and the amount of sediment provided from the margin; ii) a coarsening-upward middle interval, pointing to a decrease in subsidence rate associated with an augment in sediment supply; iii) a fining-upward, upper interval (locally preserved), documenting a phase of tectonic quiescence associated with a progressive re-equilibration of the tectonically-induced morphological profile. The basin-scale unconformity, which separates the Montevarchi and Torrente Ciuffenna synthems was due to the entrance of the Arno River into the basin as consequence of a piracy. This event caused a dramatic increase in water discharge of the axial fluvial system, and its consequent embanking. Such an erosional surface started to develop in the axial areas, and propagated along the main tributaries, triggering erosion of the alluvial fan deposits. Alluvial-fan deposits of the Torrente Ciuffenna Synthem accumulated above the unconformity during a phase of tectonic quiescence, and show a fining-upward depositional trend. This trend was generated by a progressive decrease in sediment supply stemming out from upstream migration of the knickpoints developed during the embanking of the axial system.

Fidolini, Francesco; Ghinassi, Massimiliano; Aldinucci, Mauro; Billi, Paolo; Boaga, Jacopo; Deiana, Rita; Brivio, Lara

2013-05-01

27

Evaluating the performances of an ecohydrological model in semi-arid river basins  

NASA Astrophysics Data System (ADS)

The EHSM (EcoHydrological Streamflow Model) is a conceptual lumped model aimed to daily streamflow simulation. The model, processing daily rainfall and reference evapotranspiration at the basin scale, reproduces surface and subsurface runoff, soil moisture dynamics and actual evapotranspiration fluxes. The key elements of this numerical model are the soil bucket, where rainfall, evapotranspiration and leakage drive soil moisture dynamics, and two linear reservoirs working in parallel with different characteristic response times. The surface reservoir, able to simulate the fast response of the basin, is fed by rain falling on impervious area and by runoff generated with excess of saturation mechanism while the deep reservoir, which simulates the slow response, is fed by instantaneous leakage pulses coming from the soil bucket. The model has seven parameters, which summarize soil, vegetation and hydrological catchment properties. Parameters can be assessed using simple basic ecohydrological knowledge or Monte Carlo simulations as well. The model has been here calibrated for three semi-arid river basins located in Sicily, Italy with area ranging from 10 up to 1780 Km2 with the aim of investigating how the spatial scale may influence model performances. At the same time, the link between knowledge driven parameters and the calibrated ones is explored, investigating the suitability of a lumped framework for the model as the basin size increases.

Viola, Francesco; Noto, Leonardo V.; Pumo, Dario

2013-04-01

28

Seasonalizing mountain system recharge in semi-arid basins-climate change impacts.  

PubMed

Climate variability and change impact groundwater resources by altering recharge rates. In semi-arid Basin and Range systems, this impact is likely to be most pronounced in mountain system recharge (MSR), a process which constitutes a significant component of recharge in these basins. Despite its importance, the physical processes that control MSR have not been fully investigated because of limited observations and the complexity of recharge processes in mountainous catchments. As a result, empirical equations, that provide a basin-wide estimate of mean annual recharge using mean annual precipitation, are often used to estimate MSR. Here North American Regional Reanalysis data are used to develop seasonal recharge estimates using ratios of seasonal (winter vs. summer) precipitation to seasonal actual or potential evapotranspiration. These seasonal recharge estimates compared favorably to seasonal MSR estimates using the fraction of winter vs. summer recharge determined from isotopic data in the Upper San Pedro River Basin, Arizona. Development of hydrologically based seasonal ratios enhanced seasonal recharge predictions and notably allows evaluation of MSR response to changes in seasonal precipitation and temperature because of climate variability and change using Global Climate Model (GCM) climate projections. Results show that prospective variability in MSR depends on GCM precipitation predictions and on higher temperature. Lower seasonal MSR rates projected for 2050-2099 are associated with decreases in summer precipitation and increases in winter temperature. Uncertainty in seasonal MSR predictions arises from the potential evapotranspiration estimation method, the GCM downscaling technique and the exclusion of snowmelt processes. PMID:22091994

Ajami, Hoori; Meixner, Thomas; Dominguez, Francina; Hogan, James; Maddock, Thomas

2012-01-01

29

Estimating basin-wide hydraulic parameters of a semi-arid mountainous watershed by recession-flow analysis  

E-print Network

and in watersheds with low population densities because well-drilling to obtain the hydraulic data is expensive;Since well-drilling to estimate hydraulic parameters is often prohibitively expensive in developingEstimating basin-wide hydraulic parameters of a semi-arid mountainous watershed by recession

Walter, M.Todd

30

Monitoring and modeling of two alluvial aquifers in lower Nestos river basin, Northern Greece.  

PubMed

A groundwater monitoring and modeling program in two aquifers within the lower Nestos river basin in Northern Greece is presented. A monitoring network of 54 wells was developed in the two study areas, and groundwater level measurements and water quality sample analyses were conducted for a period of 2.5 years, from March 2007 to October 2009. The field data were used for the calibration and verification of the mathematical model MODFLOW in the two aquifers. The validated model was used to examine ten alternative management scenarios regarding groundwater abstraction in the two aquifers. The study showed that MODFLOW, if properly validated, is a useful and flexible tool in groundwater resources management. PMID:22755533

Boskidis, Ioannis; Pisinaras, Vassilios; Petalas, Christos; Tsihrintzis, Vassilios A

2012-01-01

31

Geohydrology, water quality, and preliminary simulations of ground-water flow of the alluvial aquifer in the Upper Black Squirrel Creek basin, El Paso County, Colorado  

USGS Publications Warehouse

The upper Black Squirrel Creek basin in eastern El Paso County, Colorado, is underlain by an alluvial aquifer and four bedrock aquifers. Groundwater pumpage from the alluvial aquifer has increased since the mid-1950's, and water level declines have been substantial; the bedrock aquifers virtually are undeveloped. Groundwater pumpage for domestic, stock, agricultural, and municipal uses have exceeded recharge for the past 25 years. The present extent of the effect of pumpage on the alluvial aquifer was evaluated, and a groundwater flow model was used to simulate the future effect of continued pumpage on the aquifer. Measured water level declines from 1974 through 1984 were as much as 30 ft in an area north of Ellicott, Colorado. On the basis of the simulations, water level declines from October 1984 to April 1999 north of Ellicott might be as much as 20 to 30 ft and as much as 1 to 10 ft in most of the aquifer. The groundwater flow models provided a means of evaluating the importance of groundwater evapotranspiration at various stages of aquifer development. Simulated groundwater evapotranspiration was about 43% of the outflow from the aquifer during predevelopment stages but was less than 3% of the outflow from the aquifer during late-development stages. Analyses of 36 groundwater samples collected during 1984 indicated that concentrations of dissolved nitrite plus nitrate as nitrogen generally were large. Samples from 5 of the 36 wells had concentrations of dissolved nitrite plus nitrate as nitrogen that exceeded drinking water standards. Water from the alluvial aquifer generally is of suitable quality for most uses. (USGS)

Buckles, D.R.; Watts, K.R.

1988-01-01

32

Regionalising a meso-catchment scale conceptual model for river basin management in the semi-arid environment  

NASA Astrophysics Data System (ADS)

Meso-scale catchments are often of great interest for water resources development and for development interventions aimed at uplifting rural livelihoods. However, in Sub-Saharan Africa IWRM planning in such catchments, and the basins they form part of, are often ungauged or constrained by poor data availability. Regionalisation of a hydrological model presents opportunities for prediction in ungauged basins and catchments. This study regionalises HBVx, derived from the conceptual hydrological model HBV, in the semi-arid Mzingwane Catchment, Limpopo Basin, Zimbabwe. Fifteen meso-catchments were studied, including three that were instrumented during the study. Discriminant analysis showed that the characteristics of catchments in the arid agro-ecological Region V were significantly different from those in semi-arid Region IV. Analysis of flow duration curves statistically separated sub-perennial catchments from (sub-)ephemeral catchments. Regionalised parameter sets for HBVx were derived from means of parameters from the sub-perennial catchments, the (sub-)ephemeral catchments and all catchments. The parameter sets that performed best in the regionalisation are characterised by slow infiltration with moderate/fast “overland flow”. These processes appear more extreme in more degraded catchments. This is points to benefits to be derived from conservation techniques that increase infiltration rate and from runoff farming. Faster, and possibly greater, sub-surface contribution to streamflow is expected from catchments underlain by granitic rocks. Calibration and regionalisation were more successful at the dekad (10 days) time step than when using daily or monthly data, and for the sub-perennial catchments than the (sub-)ephemeral catchments. However, none of the regionalised parameter sets yielded C NS ? 0.3 for half of the catchments. The HBVx model thus does offer some assistance to river basin planning in semi-arid basins, particularly for predicting flows in ungauged catchments at longer time steps, such as for water allocation purposes. However, the model is unreliable for more ephemeral and drier catchments. Without more reliable and longer rainfall and runoff data, regionalisation in semi-arid ephemeral catchments will remain highly challenging.

Love, David; Uhlenbrook, Stefan; van der Zaag, Pieter

33

The influence of river regulation and land use on floodplain forest regeneration in the semi-arid upper Colorado River Basin, USA  

USGS Publications Warehouse

Flow regulation effects on floodplain forests in the semi-arid western United States are moderately well understood, whereas effects associated with changes in floodplain land use are poorly documented. We mapped land cover patterns from recent aerial photos and applied a classification scheme to mainstem alluvial floodplains in 10 subjectively selected 4th order hydrologic units (subbasins) in the Upper Colorado River Basin (UCRB) in order to document land use patterns (floodplain development) and assess their effects on Fremont cottonwood forest (CF) regeneration. Three of the mainstem rivers were unregulated, five were moderately regulated and two were highly regulated. We classified polygons as Undeveloped (with two categories, including CF) and Developed (with five categories). We ground-truthed 501 randomly selected polygons (4-28% of the floodplain area in each subbasin) to verify classification accuracy and to search for cottonwood regeneration, defined as stands established since regulation began or 1950, whichever is most recent. From 40% to 95% of the floodplain area remained undeveloped, but only 19-70% of the floodplain area was classified as forest. Regeneration occupied a mean of 5% (range 1-17%) of the floodplain. The likelihood of the presence of regeneration in a polygon was reduced 65% by development and independently in a complex manner by flow regulation. Our analyses indicate that floodplain forests may be in jeopardy on both regulated and unregulated rivers and that information on historical forest extent is needed to better understand their current status in the UCRB. Conservation efforts need to be coordinated at a regional level and address the potentially adverse affects of both flow regulation and floodplain development.

Northcott, K.; Andersen, D.C.; Cooper, D.J.

2007-01-01

34

The Italian Project S2 - Task 4:Near-fault earthquake ground motion simulation in the Sulmona alluvial basin  

NASA Astrophysics Data System (ADS)

Recently the Italian Department of Civil Protection (DPC), in cooperation with Istituto Nazionale di Geofisica e Vulcanologia (INGV) has promoted the 'S2' research project (http://nuovoprogettoesse2.stru.polimi.it/) aimed at the design, testing and application of an open-source code for seismic hazard assessment (SHA). The tool envisaged will likely differ in several important respects from an existing international initiative (Open SHA, Field et al., 2003). In particular, while "the OpenSHA collaboration model envisions scientists developing their own attenuation relationships and earthquake rupture forecasts, which they will deploy and maintain in their own systems", the main purpose of S2 project is to provide a flexible computational tool for SHA, primarily suited for the needs of DPC, which not necessarily are scientific needs. Within S2, a crucial issue is to make alternative approaches available to quantify the ground motion, with emphasis on the near field region. The SHA architecture envisaged will allow for the use of ground motion descriptions other than those yielded by empirical attenuation equations, for instance user generated motions provided by deterministic source and wave propagation simulations. In this contribution, after a brief presentation of Project S2, we intend to illustrate some preliminary 3D scenario simulations performed in the alluvial basin of Sulmona (Central Italy), as an example of the type of descriptions that can be handled in the future SHA architecture. In detail, we selected some seismogenic sources (from the DISS database), believed to be responsible for a number of destructive historical earthquakes, and derive from them a family of simplified geometrical and mechanical source models spanning across a reasonable range of parameters, so that the extent of the main uncertainties can be covered. Then, purely deterministic (for frequencies < 2Hz) and hybrid deterministic- stochastic source and propagation simulations are carried out for different fault rupture scenarios (but including important features such as the dominant near-surface geology), and the results in terms of representative ground motion parameters appropriately enveloped. The fully 3D problem is solved using the Spectral Element (SE) method, extensively published by Faccioli and his co-workers, and Quarteroni and co- workers, starting from 1996, and the computational code GeoELSE (Stupazzini et al., 2009; http://GeoELSE.stru.polimi.it/). Finally, numerical results are compared with available data and attenuation relationships of peak values of ground motion in the near-fault regions elsewhere. Based on the results of this work, the unfavorable interaction between fault rupture, radiation mechanism and complex geological conditions may give rise to large values of peak ground velocity (exceeding 1 m/s) even in low-to-moderate seismicity areas, and therefore increase considerably the level of seismic risk, especially in highly populated and industrially active regions, such as the Central Italy. Faccioli E., Maggio F., Paolucci R. and Quarteroni A. (1997),2D and 3D elastic wave propagation by a pseudo-spectral domain decomposition method, Journal of Seismology, 1, 237-251. Field, E.H., T.H. Jordan, and C.A. Cornell (2003), OpenSHA: A Developing Community-Modeling Environment for Seismic Hazard Analysis, Seism. Res. Lett. 74, 406-419. Stupazzini M., R. Paolucci, H. Igel (2009), Near-fault earthquake ground motion simulation in the Grenoble Valley by a high-performance spectral element code, accepted for publication in Bull. of the Seism. Soc. of America.

Stupazzini, M.; Smerzini, C.; Cauzzi, C.; Faccioli, E.; Galadini, F.; Gori, S.

2009-04-01

35

The Impact of Drought on Household Food Security in the Limpopo Basin of Semi Arid Southern Africa: The Case of Kgatleng District in Botswana  

Microsoft Academic Search

The Limpopo Basin is important to Botswana’s agriculture in terms of its land area of 80118 square kilometers. Climatic conditions in the Basin have ranged from droughts to floods in some years. The semi-arid nature of the Basin with the resultant low crop yields under rain-fed conditions has meant that communities in the area have adapted various strategies with regard

Benjamin K. Acquah

2008-01-01

36

Palaeoenvironments and palaeotectonics of the arid to hyperarid intracontinental latest Permian- late Triassic Solway basin (U.K.)  

NASA Astrophysics Data System (ADS)

The late Permian to late Triassic sediments of the Solway Basin consist of an originally flat-lying, laterally persistent and consistent succession of mature, dominantly fine-grained red clastics laid down in part of a very large intracontinental basin. The complete absence of body or trace fossils or palaeosols indicates a very arid (hyperarid) depositional environment for most of the sediments. At the base of the succession, thin regolith breccias and sandstones rest unconformably on basement and early Permian rift clastics. Overlying gypsiferous red silty mudstones, very fine sandstones and thick gypsum were deposited in either a playa lake or in a hypersaline estuary, and their margins. These pass upwards into thick-bedded, multi-storied, fine- to very fine-grained red quartzo-felspathic and sublithic arenites in which even medium sand is rare despite channels with clay pebbles up to 30 cm in diameter. Above, thick trough cross-bedded and parallel laminated fine-grained aeolian sandstones (deposited in extensive barchanoid dune complexes) pass up into very thick, multicoloured mudstones, and gypsum deposited in marginal marine or lacustrine sabkha environments. The latter pass up into marine Lower Jurassic shales and limestones. Thirteen non-marine clastic lithofacies are arranged into five main lithofacies associations whose facies architecture is reconstructed where possible by analysis of large exposures. The five associations can be compared with the desert pavement, arid ephemeral stream, sabkha, saline lake and aeolian sand dune environments of the arid to hyperarid areas of existing intracontinental basins such as Lake Eyre and Lake Chad. The accommodation space in such basins is controlled by gradual tectonic subsidence moderated by large fluctuations in shallow lake extent (caused by climatic change and local variation) and this promotes a large-scale layer-cake stratigraphy as exemplified in the Solway basin. Here, the dominant fine-grained mature sandstones above the local basal reg breccias suggest water-reworking of wind-transported sediment, as in the northern part of the Lake Chad basin. Growth faulting occurs in places in the Solway basin, caused by underlying evaporite movement, but these faults did not significantly affect pre-late Triassic sedimentation and did not expose pre-Permian units above the basal breccias. There is no evidence of post-early Permian rifting anywhere during deposition of the late Permian to middle Triassic British succession although the succession is often interpreted with a rift-basin model. The arid to hyperarid palaeoclimate changed little during deposition of the Solway basin succession, in contrast to Lakes Eyre and Chad: and this is attributed to tectonic and palaeolatitude stability. Unlike the later Mesozoic- Cenozoic, only limited plate movements took place during the Triassic in western Europe, palaeolatitude changed little, and the Solway Basin remained in the northern latitudinal desert belt from early to mid-Triassic times. However, the influence of the early Triassic impoverished biota on environmental interpretations needs further study.

Brookfield, Michael E.

2008-10-01

37

Analysis of some peculiarities of the DREAM model parameterization in a semi-arid basin of Southern Italy  

NASA Astrophysics Data System (ADS)

Water resources management in semi-arid environments is a complex issue because of the time and spatial variability of weather and the insufficient monitoring network useful to derive input data for hydrological modelling. In this work a water balance model is revised with particular attention to the input dataset and the theoretical approach in order to improve the accuracy of the predicted outputs. The DREAM model (Manfreda et al., 2005) is applied in a semi-arid basin of Southern Italy (Carapelle torrent, basin area: 506 km2). Hydrological processes are computed on a grid schematization of the river which takes into account the spatial heterogeneity of the basin using distributed data concerning soil texture, land use, hydraulic characteristics and local slope. Time and spatial variability of vegetation coverage is considered using satellite data. Normalized Difference Vegetation Index values are converted into Leaf Area Index profiles to estimate interception and evapotranspiration. The performance of the hydrological model was improved varying four aspects of the model: the pedotransfers functions used to predict the soil hydraulic characteristics, the equations referring to the evapotranspiration process, the type of satellite images and the parameters used for calibration. Evapotranspiration is calculated using two different approaches: Thornthwaite and Penman-Monteith. Leaf Area Index is estimated using a linear regression LAI-NDVI (Caraux-Garson) and a logaritmic one (Beer). The calibration of the Beer law is carried out selecting some sample areas and comparing the literature LAI values to the simulated ones. The spatial resolution of the satellite data influences the hydrologic response: the use of the MODIS images instead of the NOAA-AVHRR ones determines higher values of evapotranspiration more realistic for Mediterranean environments. The analysis described will be useful to select the equations which are more suitable for semi-arid catchments and to individuate which factors need to be measured accurately in order to achieve better results in the model output.

Bisantino, T.; Gentile, F.; Iacobellis, V.; Milella, P.; Trisorio Liuzzi, G.

2009-04-01

38

Regional groundwater-flow model of the Redwall-Muav, Coconino, and alluvial basin aquifer systems of northern and central Arizona  

USGS Publications Warehouse

A numerical flow model (MODFLOW) of the groundwater flow system in the primary aquifers in northern Arizona was developed to simulate interactions between the aquifers, perennial streams, and springs for predevelopment and transient conditions during 1910 through 2005. Simulated aquifers include the Redwall-Muav, Coconino, and basin-fill aquifers. Perennial stream reaches and springs that derive base flow from the aquifers were simulated, including the Colorado River, Little Colorado River, Salt River, Verde River, and perennial reaches of tributary streams. Simulated major springs include Blue Spring, Del Rio Springs, Havasu Springs, Verde River headwater springs, several springs that discharge adjacent to major Verde River tributaries, and many springs that discharge to the Colorado River. Estimates of aquifer hydraulic properties and groundwater budgets were developed from published reports and groundwater-flow models. Spatial extents of aquifers and confining units were developed from geologic data, geophysical models, a groundwater-flow model for the Prescott Active Management Area, drill logs, geologic logs, and geophysical logs. Spatial and temporal distributions of natural recharge were developed by using a water-balance model that estimates recharge from direct infiltration. Additional natural recharge from ephemeral channel infiltration was simulated in alluvial basins. Recharge at wastewater treatment facilities and incidental recharge at agricultural fields and golf courses were also simulated. Estimates of predevelopment rates of groundwater discharge to streams, springs, and evapotranspiration by phreatophytes were derived from previous reports and on the basis of streamflow records at gages. Annual estimates of groundwater withdrawals for agriculture, municipal, industrial, and domestic uses were developed from several sources, including reported withdrawals for nonexempt wells, estimated crop requirements for agricultural wells, and estimated per capita water use for exempt wells. Accuracy of the simulated groundwater-flow system was evaluated by using observational control from water levels in wells, estimates of base flow from streamflow records, and estimates of spring discharge. Major results from the simulations include the importance of variations in recharge rates throughout the study area and recharge along ephemeral and losing stream reaches in alluvial basins. Insights about the groundwater-flow systems in individual basins include the hydrologic influence of geologic structures in some areas and that stream-aquifer interactions along the lower part of the Little Colorado River are an effective control on water level distributions throughout the Little Colorado River Plateau basin. Better information on several aspects of the groundwater flow system are needed to reduce uncertainty of the simulated system. Many areas lack documentation of the response of the groundwater system to changes in withdrawals and recharge. Data needed to define groundwater flow between vertically adjacent water-bearing units is lacking in many areas. Distributions of recharge along losing stream reaches are poorly defined. Extents of aquifers and alluvial lithologies are poorly defined in parts of the Big Chino and Verde Valley sub-basins. Aquifer storage properties are poorly defined throughout most of the study area. Little data exist to define the hydrologic importance of geologic structures such as faults and fractures. Discharge of regional groundwater flow to the Verde River is difficult to identify in the Verde Valley sub-basin because of unknown contributions from deep percolation of excess surface water irrigation.

Pool, D.R.; Blasch, Kyle W.; Callegary, James B.; Leake, Stanley A.; Graser, Leslie F.

2011-01-01

39

Lower Eocene alluvial paleosols (Willwood Formation, Northwest Wyoming, U.S.A.) and their significance for paleoecology, paleoclimatology, and basin analysis  

USGS Publications Warehouse

The lower Eocene Willwood Formation of northwest Wyoming is a 700 m thick accumulation of alluvial floodplain and channel mudstones and sandstones, nearly all of which show paleopedogenic modifications. Pedogenesis of Willwood sandstones is indicated by taproot and vertebrate and invertebrate bioturbation, early local cementation by calcium carbonate, and thin illuviation cutans on clastic grains. Pedogenesis in Willwood mudstones is indicated by plant bioturbation, insect and other invertebrate burrow casts and lebensspuren; free iron, aluminum, and manganese mobilization, including hydromorphic gleying; sesquioxide and calcareous glaebule formation in lower parts of the solum; presence of clay-rich and organic carbon-rich zones; and well differentiated epipedons and albic and spodic horizons. Probable A horizons are also locally well developed. Occurrence of variegated paleosol units in thick floodplain mudstone deposits and their association with thin, lenticular, and unconnected fluvial sandstones in the Willwood Formation of the central and southeast Bighorn Basin suggest that these soils formed during times of rapid sediment accumulation. The tabular geometry and lateral persistence of soil units as well as the absence of catenization indicate that Willwood floodplains were broad and essentially featureless. All Willwood paleosols were developed on alluvial parent materials and are complex in that B horizons of younger paleosols were commonly superimposed upon and mask properties of suspected A and B horizons of the next older paleosols. The soils appear to be wet varieties of the Spodosol and Entisol groups (aquods and ferrods, and aquents, respectively), though thick, superposed and less mottled red, purple, and yellow paleosols resemble some ultisols. Most Willwood paleosols resemble warm temperate to subtropical alluvial soils that form today under alternating wet and dry conditions and (or) fluctuating water tables. The up-section decrease in frequency of gley mottles, increase in numerical proportion and thickness of red versus orange coloration, and increase in abundance of calcrete glaebules indicate better drained soils and probably drier climate in late Willwood time. This drying is believed to be related to creation of rain shadows and spacing of rainfall (but not necessarily decrease in absolute rainfall) due to progressive tectonic structural elevation of the mountainous margins of the Bighorn Basin. ?? 1981.

Bown, T.M.; Kraus, M.J.

1981-01-01

40

Mapping Ecological Processes and Ecosystem Services for Prioritizing Restoration Efforts in a Semi-arid Mediterranean River Basin  

NASA Astrophysics Data System (ADS)

Semi-arid Mediterranean regions are highly susceptible to desertification processes which can reduce the benefits that people obtain from healthy ecosystems and thus threaten human wellbeing. The European Union Biodiversity Strategy to 2020 recognizes the need to incorporate ecosystem services into land-use management, conservation, and restoration actions. The inclusion of ecosystem services into restoration actions and plans is an emerging area of research, and there are few documented approaches and guidelines on how to undertake such an exercise. This paper responds to this need, and we demonstrate an approach for identifying both key ecosystem services provisioning areas and the spatial relationship between ecological processes and services. A degraded semi-arid Mediterranean river basin in north east Spain was used as a case study area. We show that the quantification and mapping of services are the first step required for both optimizing and targeting of specific local areas for restoration. Additionally, we provide guidelines for restoration planning at a watershed scale; establishing priorities for improving the delivery of ecosystem services at this scale; and prioritizing the sub-watersheds for restoration based on their potential for delivering a combination of key ecosystem services for the entire basin.

Trabucchi, Mattia; O'Farrell, Patrick J.; Notivol, Eduardo; Comín, Francisco A.

2014-06-01

41

Large Alluvial Fans on Mars  

NASA Technical Reports Server (NTRS)

Several dozen distinct alluvial fans, 10 to greater than 40 km long downslope are observed exclusively in highlands craters. Within a search region between 0 deg. and 30 deg. S, alluvial fan-containing craters were only found between 18 and 29 S, and they all occur at around plus or minus 1 km of the MOLA-defined Martian datum. Within the study area they are not randomly distributed but instead form three distinct clusters. Fans typically descend greater than 1 km from where they disgorge from their alcoves. Longitudinal profiles show that their surfaces are very slightly concave with a mean slope of 2 degrees. Many fans exhibit very long, narrow low-relief ridges radially oriented down-slope, often branching at their distal ends, suggestive of distributaries. Morphometric data for 31 fans was derived from MOLA data and compared with terrestrial fans with high-relief source areas, terrestrial low gradient alluvial ramps in inactive tectonic settings, and older Martian alluvial ramps along crater floors. The Martian alluvial fans generally fall on the same trends as the terrestrial alluvial fans, whereas the gentler Martian crater floor ramps are similar in gradient to the low relief terrestrial alluvial surfaces. For a given fan gradient, Martian alluvial fans generally have greater source basin relief than terrestrial fans in active tectonic settings. This suggests that the terrestrial source basins either yield coarser debris or have higher sediment concentrations than their Martian counterpoints. Martian fans and Basin and Range fans have steeper gradients than the older Martian alluvial ramps and terrestrial low relief alluvial surfaces, which is consistent with a supply of coarse sediment. Martian fans are relatively large and of low gradient, similar to terrestrial fluvial fans rather than debris flow fans. However, gravity scaling uncertainties make the flow regime forming Martian fans uncertain. Martian fans, at least those in Holden crater, apparently formed around the time of the Noachian-Hesperian boundary. We infer that these fans formed during an episode of enhanced precipitation (probably snow) and runoff, which exhibited both sudden onset and termination.

Moore, Jeffrey M.; Howard, Alan D.

2004-01-01

42

A tectonically controlled alluvial fan which developed into a marine fan-delta at a complex triple junction: Miocene Gildirli Formation of the Adana Basin, Turkey  

NASA Astrophysics Data System (ADS)

The sediments of the Gildirli Formation in the Karaisali embayment of the Adana Basin, southern Turkey, records the evolution, under tectonic control at a complex triple junction, of an alluvial fan into a fan-delta during a rapid Early Miocene transgression. The alluvial fan is represented by the lower part of the formation (Çakmak Member) and is characterized by an internal architecture, recording an overall progradation of the coarse proximal fan conglomerates over distal fine-grained sediments. The conglomerates contain mostly Upper Cretaceous limestone clasts of various sizes derived from the faulted mountain front of the Taurus range where this limestone is widely exposed. This active mountain front delimited the Karaisah embayment to the north and provided, during the fault activity, abundant coarse clasts to this area throughout the deposition of both the alluvial fan and the overlying fan-delta sediments. The production of fine detritus during the faulting was very limited and therefore this source contributed little fine grain detritus to the sediments. Provenance studies indicate that the fine clastics in the Gildirli Formation were carried by streams during periods of active faulting and also during periods of tectonic quiescence from a far-distant source in the hinterlands of the Taurus Mountains. The recurrent activity along the northern boundary-fault resulted in the intercalation of these fine clastics with the predominant coarse sediments in this formation. When the study area was flooded from the south by a rapidly deepening Early Miocene sea, the accumulation of all these sediments took place in a fan-delta environment. The fan-delta sediments constitute the upper parts of the Gildirli Formation (Kabalaktepe Member) and display an inverse facies pattern in which foreset beds overlie topsets and hence an upward-fining and deepening sequence. This deviation from a genetic upward-coarsening sequence of a typical marine delta was perhaps the result of a rapid relative rise in sea-level, due to tectonically induced subsidence of the area possibly coupled with a short-term global sea-level rise in the Burdigalian.

Görür, Naci

1992-12-01

43

Runoff generation processes during the wet-up phase in a semi-arid basin in Iran  

NASA Astrophysics Data System (ADS)

Understanding the hydrological processes in catchments is important for water resources management, particularly in semi-arid regions of the world. To contribute to this field, dominant runoff generation processes in a semi-arid basin (283 km2) in Southwestern Iran were investigated using analysis of hydrometric data in combination with natural isotopic tracers through the wet-up phase of a rainy season. The analysis of seven rainfall-runoff events during the rainfall dominated period illustrated the role of antecedent base flow and cumulative rainfall for explaining the hydrological response. Three distinct storm events and the corresponding discharge were collected and analyzed for oxygen-18 and deuterium isotope composition. The results show that during the wetting-up cycle, the runoff ratio during storm events increased progressively from 1 to 10%. Higher event runoff ratios following catchment wet-up were shown to be directly linked to changes in soil moisture, which in turn controlled the runoff generation processes. In line with the hydrometric results, the two-component hydrograph separation using ?18O and ?2H demonstrated a clear connection to the antecedent wetness conditions. The results suggest that the runoff ratios during storms and the partitioning of event and pre-event water fractions are sensitive to the amount of catchment wet-up and could hence be strongly impacted by changes in the timing, duration and amount of precipitation in the future.

Zarei, H.; Akhondali, A. M.; Mohammadzadeh, H.; Radmanesh, F.; Laudon, H.

2014-04-01

44

Isotopes and groundwater management strategies under semi-arid area: case of the Souss upstream basin (Morocco).  

PubMed

This study concerns the Souss upstream basin. The objective is to investigate the characteristics of surface water and groundwater, to assess the impact of artificial recharge as reinforcement of the natural replenishment and assess the renewal of groundwater under semi-arid area. Two major water types are observed: (i) surface waters and upstream springs (least mineralized) and (ii) all groundwater samples (prevailing calcium and magnesium bicarbonate water type). Water isotopes show a low evaporation of precipitations during infiltration. Impoverishment in heavy isotopes is the characteristic of mountain rainfalls, or of a climate colder and wetter than present. Carbon-14 activities (34-94 pmc) indicate a long residence time. The artificial recharge is low compared to the reservoir volume, due to which the renewal rate is also low. PMID:21377885

Bouragba, L; Mudry, J; Bouchaou, L; Hsissou, Y; Krimissa, M; Tagma, T; Michelot, J L

2011-07-01

45

Alluvial Fan-lacustrine Sedimentation and its Tectonic Implications in the Cretaceous Athgarh Gondwana Basin, Orissa, India  

Microsoft Academic Search

The Athgarh Formation is the northernmost extension of the east coast Upper Gondwana sediments of Peninsular India. The formation of the present area is a clastic succession of 700 m thick and was built against an upland scarp along the north and northwestern boundary of the basin marked by an E-W-ENE-WSW boundary fault. A regular variation in the dominant facies

Banabehari Mishra; Krishna Lal Pandya; Wataru Maejima

2004-01-01

46

Late Eocene arid climate in Asia inferred from multi-proxy sclerochronology using oyster shells from the Tarim Basin  

NASA Astrophysics Data System (ADS)

The Asian climate is characterized by a strong duality between monsoon dominant climate in southeastern Asia and arid climate in central Asia. Based on climate modelling, this pattern has been explained by two main driving mechanisms associated to the Indo-Asia collision: uplift of Tibetan Plateau and/or retreat of an epicontinental sea formerly covering Asia. However, climate proxies are lacking to test these hypotheses and understand how and when this climate pattern was established. The aim of this study is to develop a new method to understand the Late Eocene climate in central Asia, when the Paratethys was still covering the continent. A crucial task to this end is to reconstruct the climate seasonality in central Asia: when and how the climate changed from a probably temperate climate, due to the sea presence, to an arid climate? Did this climate change have an impact on the monsoon intensification in southestern Asia? Here we use bivalve sclerochronology to assess the Eocene climate variability on seosonal time scales in Central Asia. Well preserved oyster shells (Sokolowia buhsii, Grewingk) were sampled in marine sediments from Lutetian to Bartonian age in southwestern Tarim Basin, Xinjiang, China (Aertashi and Kezi sections). The Paratethys sea was shallow and partially closed, thus the challenge is to distinguish temperature from salinity effects on the biomineralization. Here, we present a new method using multi-proxy approach. The fossils were cut perpendicularly to the maximum growth axis to expose incremental yearly growth lines of the shell to be analysed. We first obtained Mg/Ca record using LA ICP-MS indicative of the temperature variations. We then recovered an isotopic sclerogeochemistry (?18Oc) record using micromilling extraction to assess the ?18Ow (and thereby the salinity) of the sea. Results show that seasonal temperature variability was considerable. Furthemore salinity increase during summers indicating a negative water balance. Thus, we infer that central Asian climate was already very arid during the Late Eocene, although the Paratethys sea was still covering the Asian continent. This is an apparent contradiction with the first assumption of a temperate climate before sea retreat but is in agreement with coeval palynological data from the Tarim Basin and with recent climate models of Eocene Asian monsoons.

Bougeois, Laurie; de Rafélis, Marc; Reichart, Gert-Jan; de Nooijer, Lennart J.; Nicollin, Florence; Dupont-Nivet, Guillaume

2013-04-01

47

Northwest Arid Lands : an introduction to the Columbia Basin shrub-steppe  

SciTech Connect

This book explores the rich variety of life in shrub-steppe lands of the Columbia River Basin. It describes, for a non-technical audience, the flora, fauna, and geology of the lower Columbia Basin in and around the Tri-Cities, Washington. Features include color photos and maps of shrub-steppe plants and animals; lists and illustration of common plants, mammals, reptiles, amphibians, birds, fish, and species of conservation concern; tips on places to see wildflowers and wildlife; geological travel logs from the Tri-Cities to Seattle and Spokane; and a comprehensive bibliography and definition of ecological terms.

O'Connor, Georganne P. (BATTELLE (PACIFIC NW LAB)); Wieda, Karen J. (BATTELLE (PACIFIC NW LAB))

2001-04-15

48

A Basin-Averaged Water Balance Approach to Estimate Catchment-Scale Groundwater Flow in a Semi-arid Mountainous Catchment  

NASA Astrophysics Data System (ADS)

Quantification of the contribution of groundwater flow from highland areas of mountainous watersheds to semi-arid and arid valley bottom unconsolidated aquifers is increasingly needed for the assessment of water resources in many populated areas. In mountainous environments, however, data for Darcy equation parameters are limited, leading to uncertainty in estimates of groundwater flow of up to two or more orders of magnitude. An alternative method for estimating regional groundwater flow from highland to valley bottom areas was developed for the semi-arid Okanagan Basin, British Columbia, Canada. The method involved a basin-averaged water balance approach, using mean annual surface water run-off (RO) data for 9 gauged tributaries with spatially distributed estimates of mean annual precipitation (P) and actual evapotranspiration (AET), to develop basin-averaged relationships for prediction of recharge-driven groundwater flow through the bedrock highland areas. Groundwater flow from highland bedrock areas to unconsolidated valley bottom aquifers was subsequently accounted for through a calibration exercise using a spreadsheet tool developed for the project. Average annual AET was the most difficult parameter to quantify at the tributary catchment scale. Spatially distributed AET estimates were developed using temperature and precipitation data, with consideration of expected AET ranges established based on available data for the region. Results for the bedrock areas in the Okanagan Basin indicated basin-averaged partitioning of mean annual precipitation as 68% AET, 19% to surface water run-off (in streams), and 13% to net recharge (groundwater flow). The influence of AET and surface water run-off parameter uncertainty on regional bedrock groundwater flow calculations was a factor of 2 (AET range of 60-70% catchment precipitation) and 1.2 (RO range of 14 to 26%), respectively. This approach allows for preliminary estimates of water budget constrained recharge- driven groundwater flow at the catchment or basin scale.

Neilson-Welch, L. A.; Allard, R.; Geller, D.; Allen, D. M.

2008-12-01

49

Riparian vegetation of two semi-arid Mediterranean rivers: Basin-scale responses of woody and herbaceous plants to environmental gradients  

Microsoft Academic Search

Mediterranean fluvial ecosystems are subjected to ever-increasing water demands and to a wide variety of other human impacts\\u000a with potential negative effects on riparian vegetation. Nevertheless, few studies have compared the importance of human versus\\u000a natural factors in structuring riparian vegetation in this region, particularly in semi-arid areas. We examined basin-scale\\u000a responses of riparian vegetation to the main environmental gradient

M. Jacoba Salinas; J. Jesús Casas

2007-01-01

50

Hydrogeochemical zonation and its implication for arsenic mobilization in deep groundwaters near alluvial fans in the Hetao Basin, Inner Mongolia  

NASA Astrophysics Data System (ADS)

High As groundwater has been found in shallow aquifers of the flat plain of the Hetao basin, but little is known about As concentration in deep groundwaters around piedmont areas, which are the major drinking water resources. One hundred and three groundwater samples from wells with depths >50 m and seven samples from one multi-level monitoring well (89 m in depth) were analyzed for chemical compositions and 18O and D isotopes to examine the geochemical processes controlling As mobilization. According to hydrogeological setting, chemical and isotopic characteristics of deep groundwater, three distinguished hydrogeochemical zones are delineated, including Recharge-Oxic Zone (Zone I), Groundwater Flow-Moderate Reducing Zone (Zone II), and Groundwater Flow-Reducing Zone (Zone III). Zone I is located in proximal fans in the recharge area with oxic conditions, where low As groundwater generally occurs. In Zone II, located in the intermediate between the fans and the flat plain with Fe-reduction predominated, groundwater As is moderate. Zone III lies in the flat plain with the occurrence of SO42- reduction, where high As groundwater is mostly found. This indicates that release of As to groundwater is primarily determined by reduction sequences. Arsenic is immobilized in O2 /NO3- reduction stage in Zone I and released in Fe-reducing conditions of Zone II, and displays a significant elevated concentration in SO4-reducing stage in Zone III. Dissolution of carbonate minerals occurs in Zone I, while Ca2+ and Mg2+ are expected to precipitate in Zone II and Zone III. In the multi-level monitoring well, both chemical and isotopic compositions are dependent of sampling depths, with the similar trend to the hydrogeochemical zonation along the flow path. The apparent increases in ?D and ?18O values in Zone III reveal the possibility of high As shallow groundwater recharge to deep groundwater. It indicates that deep groundwaters in proximal fans have low As concentrations and are considered as safe drinking water resources in the Hetao basin. However, high As concentration is frequently observed in deep groundwater in the flat plain, which should be routinely monitored in order to avoid chronic As poisoning.

Jia, Yongfeng; Guo, Huaming; Jiang, Yuxiao; Wu, Yang; Zhou, Yinzhu

2014-10-01

51

Geomorphic controls on hydrology and vegetation in an arid basin: Turkana district, northern Kenya  

SciTech Connect

As part of a broad ecological study of Kenyan pastoralist adaptation to periodic drought, a study was done to determine how arid region geomorphology affects hydrology and subsequently vegetative patterns. In this study area, 100 kilometers south of Lake Turkana, it appears that irregular precipitation is stored in bajada sediments and is available to deeply rooted vegetation over long periods of time. This vegetation provides a relatively constant food source for people's herds of browsers, the camels and goats, whereas cattle, which graze mainly on grasses, are significant producers only during wet seasons. Field observations suggest that the mountain and abutting pediment soils are too shallow to store appreciable water. However, greater quantities of water are stored in the deeper bajada sediments adjacent to the pediment where pastoralists dig temporary wells in ephemeral channels during wet seasons. Density of tree growth is greater along channels, and highest canopy cover values are found about the pediment-bajada interface. Geohydrologic processes in this area provide the basis for continuous occupation by the desert people, in contrast to recurring famines in adjacent areas, by enhancing the growth of woody vegetation.

Coppinger, K.D.; Doehring, D.O.; Schimel, D.S.

1985-01-01

52

Hydrogeology of an ancient arid closed basin: Implications for tabular sandstone-hosted uranium deposits  

SciTech Connect

Hydrogeologic modeling shows that tabular-type uranium deposits in the grants uranium region of the San Juan basin, New Mexico, formed in zones of ascending and discharging regional ground-water flow. The association of either lacustrine mudstone or actively subsiding structures and uranium deposits can best be explained by the occurrence of lakes at topographic depressions where ground water having different sources and compositions is likely to converge, mix, and discharge. Ascending and discharging flow also explains the association of uranium deposits with underlying evaporites and suggests a brine interface. The simulations contradict previous suggestions that ground water moved downward in the mudflat.

Sanford, R.F. (U.S. Geological Survey, Denver, CO (USA))

1990-11-01

53

Late Pleistocene alluvial plain sedimentation in Lower Narmada Valley, Western India: Palaeoenvironmental implications  

NASA Astrophysics Data System (ADS)

Late Pleistocene fluvial sediments that were deposited in a slowly sinking basin are now exposed as 30-50 m high incised vertical cliffs all along the Lower Narmada Valley in western India. The exposed fluvial deposits have been classified into two sediment packages, alluvial fan sediments overlain by alluvial plain sediments. The alluvial plain sequence has not been studied previously. It consists mainly of sands and silts and is dominated by overbank deposits. Occurrence of large scale bedforms in the alluvial plain sequence points to the existence of a large sand bed river in an alluvial plain setting. The major sedimentary facies in stratigraphic order include large channel fills, giant epsilon cross bedded strata, overbank fines occurring in horizontal, massive and undulatory stratified forms associated with crevasse splay and backswamp deposits, and a reddish brown palaeosol overlain by thinly stratified sands and silts at the top of the exposed sediment succession. Large sized channel fills occur at two stratigraphic levels, which are morphologically similar and are indicative of high rates of deposition and avulsion. The large channel fill structures and the giant epsilon cross bedded strata indicate a large single channel river that was consistently 10-15 m deep and about 70-80 m wide even during the dry seasons. These dimensions are larger than those of the present day Narmada River at low discharge levels. The overbank sediments indicate rapid deposition through frequent overbank floods and floodplain aggradation by a laterally shifting river. Available chronologic data suggests that the reddish brown palaeosol correlates with a regional phase of pedogenesis in the alluvial plain of Gujarat prior to the Last Glacial Maximum (LGM). The thinly stratified sands and silts overlying the palaeosol were deposited by a considerably depleted but perennial river during the arid phase of the Last Glacial Maximum. Overall, the alluvial plain sediments of the Lower Narmada valley, particularly those below the palaeosol, have been attributed to a hyper-avulsive large river with low sinuosity whose high discharge levels were determined primarily by a large catchment area further to the east and not by the semiarid climate prevailing in the Gujarat alluvial plain during the upper part of the Late Pleistocene. The study concludes that the Narmada River has maintained a large catchment at least since the last 100 ka, however, the river was characterised by a much bigger channel during much of the Late Pleistocene with discharge levels higher than the present day.

Bhandari, S.; Maurya, D. M.; Chamyal, L. S.

2005-01-01

54

Linkages between snow ablation and atmospheric boundary-layer conditions in a semi-arid basin of Western Canada  

NASA Astrophysics Data System (ADS)

High-elevation snowpacks provide critical inputs to the hydrological system of mountainous semi-arid regions where summer precipitation is insufficient to maintain adequate discharges for ecological and economic needs. The Okanagan Basin in Western Canada is an example of such a system, as most of the summer streamflow is derived from snowmelt. To better understand how snowmelt events vary as a result of atmospheric conditions, this study developed statistical models using upper-air atmospheric data for evaluating changes in snowpack ablation. Specifically, radiosonde data were statistically linked with detailed ground-based measurements of snowmelt and associated streamflow. Statistical models were developed based on data from the 2007 ablation season and concurrent data from the 850 hPa geopotential height. These models explained 57-68% of the variance in snowmelt for 2007, and were extended to predict snowmelt for the radiosonde period of record (1972-2012). Time-series analyses showed significant trends toward higher winter and spring temperatures, vertical temperature gradients in the atmospheric boundary layer in spring, and earlier dates for snowmelt and freshet initiation. Significant negative trends were also found towards decreasing spring precipitation. More broadly, ablation-season climatic and hydrological variables were significantly positively correlated with the winter and spring Multivariate El Niño Southern Oscillation and Pacific Decadal Oscillation indices, in which the positive (negative) phase was associated with higher (lower) magnitude and frequency of melt events. This combination of strong correlations and significant temporal trends indicates that with projected air-temperature increases, the magnitude and duration of melt events are likely to increase, particularly during favourable phases of the above teleconnections.

Jackson, Scott I.; Prowse, Terry D.; Bonsal, Barrie R.

2014-09-01

55

Tamarix Abundance in Arid River Basins of Arizona (USA) Reflects Prevailing Hydrology  

NASA Astrophysics Data System (ADS)

Flow regimes are strong determinants of riparian vegetation structure. Flow regimes vary among rivers of the American Southwest because of intrinsic hydrogeomorphic differences and because of differing degrees and types of human influence. This study reports on a survey of river reaches in the Gila and Bill Williams drainage basins of Arizona. that varied in flow permanence (perennial, intermittent, ephemeral), presence or absence of an upstream flow-regulating dam, and presence or absence of municipal effluent as a water source. The study focused on abundance patterns of Tamarix ramosissima, a species introduced to North America, relative to those of Populus fremontii and Salix gooddingii, which historically were common pioneer trees in the region. Analysis indicated that Tamarix was significantly more abundant than Populus-Salix at sites with intermittent flow (and thus where groundwater seasonally declined below rooting zones of shallow-rooted phreatophytes) and at sites below flow-regulating dams. Populus-Salix, in contrast, was the dominant forest type along free-flowing, perennial rivers. In reaches with ephemeral flow, including those below diversion dams, all forest types were sparse or absent and xeric shrublands predominated. Riparian ecosystem restoration projects are underway along several rivers in the American Southwest, most of which have a goal of increasing the abundance of Populus-Salix forests. These data affirm the importance of flow regime restoration for re-establishing Populus-Salix as the dominant pioneer forest type.

Stromberg, J. C.

2005-12-01

56

Large alluvial fans on Mars Jeffrey M. Moore  

E-print Network

Large alluvial fans on Mars Jeffrey M. Moore Space Sciences Division, NASA Ames Research Center-relief source areas, terrestrial low-gradient alluvial ramps in inactive tectonic settings, and older Martian basin relief than terrestrial fans in active tectonic settings. This suggests that the terrestrial

Howard, Alan D.

57

Groundwater quality and management in arid and semi-arid regions: Case study, Central Eastern Desert of Egypt  

NASA Astrophysics Data System (ADS)

This study presents a model budget for groundwater in the Central Eastern Desert of Egypt. The stable isotopic composition and hydrochemistry of groundwater samples collected from different aquifers were determined to identify recharge sources and water quality. Stable isotopic values suggest that shallow alluvial and fracture zone aquifers are recharged from seasonal precipitation, while groundwater in deeper sedimentary sub-basins is paleowater that was recharged during periods of less arid regional climate. Hydrochemical analysis indicates elevated salinity in each aquifer type, which is attributed to leaching and dissolution of terrestrial salts and to mixing with marine water. Groundwater from sedimentary sub-basin aquifers can be treated and used for drinking and domestic purposes. Groundwater from shallow alluvial and fracture zone wells is suitable for animal husbandry and mineral ore dressing. A model water budget shows that approximately 4.8 × 109 m3 of recoverable groundwater is stored in sedimentary sub-basin aquifers, or approximately 550 years of water at present utilization rates.

Amer, Reda; Ripperdan, Robert; Wang, Tao; Encarnación, John

2012-07-01

58

Holocene environments of the central Great Plains: multi-proxy evidence from alluvial sequences, southeastern Nebraska  

Microsoft Academic Search

Pollen, plant macrofossils, phytoliths, carbon isotopes, and alluvial history from sediments exposed along the South Fork of the Big Nemaha River, southeastern Nebraska, USA, provide an integrated reconstruction of changes in Holocene vegetation, climate, and fluvial activity. From 9000 to 8500 uncalibrated 14C yr BP, climate became more arid and the floodplain and alluvial fans in the main valley aggraded

Richard G. Baker; Glen G. Fredlund; Rolfe D. Mandel; E. A. Bettis

2000-01-01

59

Atmospheric-Ecosystem CO2 Exchange in Sparse Arid Shrublands Across the Great Basin USA Over Multiple Years: Identifying Patterns and Mechanisms  

NASA Astrophysics Data System (ADS)

Up to recently, desert ecosystems have essentially been ignored with respect to their influence on global carbon cycling and their potential role in modulating atmospheric CO2 levels. Because deserts, defined here as ecosystems receiving <280 mm of precipitation annually, cover 35% of Earth's surface, even small positive or negative net ecosystem CO2 exchange (NEE=fluxes) can have globally meaningful effects on atmospheric CO2. Since 2003 we have been measuring NEE and annual NEP at 10 arid shrubland sites around the Great Basin in Nevada, USA using eddy covariance and large static chamber "domes" with the objectives of quantifying seasonal, annual and interannual fluxes and the environmental and ecological factors that may be modulating these fluxes. Surprisingly, annual NEP measured in Mojave Desert creosote bush (Larrea tridentata)-dominated ecosystems, high desert sagebrush steppe (Aremesia tridentata) ecosystems, and greasewood (Sarcobatus vermiculatus) ecosystems have been largely positive (net C uptake by ecosystems; range of zero to 90 g C m-2 yr-1) and often large (as high 100 to 180 g C m-2 yr-1). Thus, the data from these arid shrublands suggest a much larger arid land C sink than has been previously assumed and call for closer tracking of the CO2 fluxes in these ecosystems.

Arnone, J. A.; Jasoni, R. L.; Larsen, J. D.; Fenstermaker, L. F.; Wohlfahrt, G.

2008-12-01

60

Rainwater harvesting in arid and semi-arid zones  

Microsoft Academic Search

In arid and semi-arid regions, the scarcity of water can be alleviated by rainwater harvesting, which is defined as a method of inducing, collecting, storing, and conserving local surface runoff for agriculture. Rainwater harvesting can be applied with different systems, and this dissertation deals with the system of micro-catchments. A microcatchment consists of a runoff area and a basin area

Th. M. Boers

1994-01-01

61

Using a physically-based model, tRIBS-Erosion, for investigating the effects of climate change in semi-arid headwater basins.  

NASA Astrophysics Data System (ADS)

Soil erosion due to rainfall detachment and flow entrainment of soil particles is a physical process responsible for a continuous evolution of landscapes. The rate and spatial distribution of this phenomenon depend on several factors such as climate, hydrologic regime, geomorphic characteristics, and vegetation of a basin. Many studies have demonstrated that climate-erosion linkage in particular influences basin sediment yield and landscape morphology. Although soil erosion rates are expected to change in response to climate, these changes can be highly non-linear and thus require mechanistic understanding of underlying causes. In this study, an integrated geomorphic component of the physically-based, spatially distributed hydrological model, tRIBS, the TIN-based Real-time Integrated Basin Simulator, is used to analyze the sensitivity of semi-arid headwater basins to climate change. Downscaled outputs of global circulation models are used to inform a stochastic weather generator that produces an ensemble of climate scenarios for an area in the Southwest U.S. The ensemble is used as input to the integrated model that is applied to different headwater basins of the Walnut Gulch Experimental Watershed to understand basin response to climate change in terms of runoff and sediment yield. Through a model application to multiple catchments, a scaling relationship between specific sediment yield and drainage basin area is also addressed and probabilistic inferences on future changes in catchment runoff and yield are drawn. Geomorphological differences among catchments do not influence specific changes in runoff and sediment transport that are mostly determined by precipitation changes. Despite a large uncertainty dictated by climate change projections and stochastic variability, sediment transport is predicted to decrease despite a non-negligible possibility of larger runoff rates.

Francipane, Antonio; Fatichi, Simone; Ivanov, Valeriy Y.; Noto, Leonardo V.

2013-04-01

62

The effect of vegetation and beaver dams on geomorphic recovery rates of incised streams in the semi-arid regions of the Columbia River basin, USA.  

NASA Astrophysics Data System (ADS)

Channel incision is a common occurrence in semi-arid regions of the Columbia River basin and throughout the world, where a fragile balance between climate, vegetation and geology makes channels susceptible to changes in hillslope erosion, stream discharge and sediment yield. Incision is defined as a rapid downcutting and lowering of the stream bed such that it reduces the frequency and duration of flooding onto the adjacent floodplain. We are studying the feasibility of restoring incised streams throughout the interior Columbia River basin. We hypothesize that under proper land use management, it is possible for them to aggrade such that they reconnect to their former floodplains within relatively short time frames. Theoretical and empirical evidence suggests that over decadal time scales, changes to land management that excludes grazing and allows riparian vegetation to become established can cause significant fill within the incised valleys. Preliminary modeling suggests that factors most affecting the length of time for an incised valley to completely aggrade and reconnect to its pre-incision floodplain are the depth of the incision, sediment production in the watershed, the amount and type of riparian vegetation, and the extent of beaver dam construction. While most natural resource and fisheries managers are aware of widespread incision throughout the Columbia River basin, the extent of incision within the range of the Pacific salmon is largely undocumented. However, we do know many incised streams that historically supported salmon no longer do so, and that habitat conditions are severely degraded in these incised streams. The historical record shows that numerous salmon-bearing streams in the semi-arid region of the interior Columbia River basin once contained narrow and deep, slowly meandering channels lined with cottonwoods, willows and/or sedges, contained numerous beaver dams, contained abundant and easily accessible off-channel habitat on the floodplain and had good flow and cool temperatures throughout most of the year. Today most of these streams are incised and contain little or no riparian vegetation or beaver dams. Stream temperatures are high and flow is ephemeral. Incision is thought to have lowered stream-adjacent water tables, causing both the loss of riparian vegetation and the increase in stream temperature. Many of these streams no longer support fish populations. We hypothesize that if incised streams were restored by creating conditions such that they could aggrade and reconnect to their former floodplains, that habitat conditions would be sufficient to again support salmon populations, and that this would greatly expand their range throughout much of the Columbia River basin.

Pollock, M.; Beechie, T.; Jordan, C.

2005-05-01

63

A groundwater-based, objective-heuristic parameter optimisation method for a precipitation-runoff model and its application to a semi-arid basin  

NASA Astrophysics Data System (ADS)

A hydrologic model calibration methodology that is based on groundwater data is developed and implemented using the US Geological Survey's precipitation-runoff modelling system (PRMS) and the modular modelling system (MMS), which performs automatic calibration of parameters. The developed methodology was tested in the Akrotiri basin, Cyprus. The necessity for the groundwater-based model calibration, rather than a typical runoff-based one, arose from the very intermittent character of the runoff in the Akrotiri basin, a case often met in semi-arid regions. Introducing a datum and converting groundwater storage to head made the observable groundwater level the calibration indicator. The modelling of the Akrotiri basin leads us to conclude that groundwater level is a useful indicator for hydrological model calibration that can be potentially used in other similar situations in the absence of river flow measurements. However, the option of an automatic calibration of the complex hydrologic model PRMS by MMS did not ensure a good outcome. On the other hand, automatic optimisation, combined with heuristic expert intervention, enabled achievement of good calibration and constitutes a valuable means for saving effort and improving modelling performance. To this end, results must be scrutinised, melding the viewpoint of physical sense with mathematical efficiency criteria. Thus optimised, PRMS achieved a low simulation error, good reproduction of the historic trend of the aquifer water level evolution and reasonable physical behaviour (good hydrologic balance, Reasonable match of aquifer level evolution, good estimation of mean natural recharge rate).

Mazi, K.; Koussis, A. D.; Restrepo, P. J.; Koutsoyiannis, D.

2004-05-01

64

Variations in fluvial deposition on an alluvial plain: an example from the Tongue River Member of the Fort Union Formation (Paleocene), southeastern Powder River Basin, Wyoming, U.S.A.  

USGS Publications Warehouse

The Tongue River Member of the Paleocene Fort Union Formation is an important coal-bearing sedimentary unit in the Powder River Basin of Wyoming and Montana. We studied the depositional environments of a portion of this member at three sites 20 km apart in the southeastern part of the basin. Six lithofacies are recognized that we assign to five depositional facies categorized as either channel or interchannel-wetlands environments. (1) Type A sandstone is cross stratified and occurs as lenticular bodies with concave-upward basal surfaces; these bodies are assigned to the channel facies interpreted to be the product of low-sinuosity streams. (2) Type B sandstone occurs in parallel-bedded units containing mudrock partings and fossil plant debris; these units constitute the levee facies. (3) Type C sandstone typically lacks internal structure and occurs as tabular bodies separating finer grained deposits; these bodies represent the crevasse-splay facies. (4) Gray mudrock is generally nonlaminated and contains ironstone concretions; these deposits constitute the floodplain facies. (5) Carbonaceous shale and coal are assigned to the swamp facies. We recognize two styles of stream deposition in our study area. Laterally continuous complexes of single and multistoried channel bodies occur at our middle study site and we interpret these to be the deposits of sandy braided stream systems. In the two adjacent study sites, single and multistoried channel bodies are isolated in a matrix of finer-grained interchannel sediment suggesting deposition by anastomosed streams. A depositional model for our study area contains northwest-trending braided stream systems. Avulsions of these systems created anastomosed streams that flowed into adjacent interchannel areas. We propose that during late Paleocene a broad alluvial plain existed on the southeastern flank of the Powder River Basin. The braided streams that crossed this surface were tributaries to a northward-flowing, basin-axis trunk stream that existed to the west. ?? 1990.

Johnson, E.A.; Pierce, F.W.

1990-01-01

65

The Effect of Human Borders on Water Dynamics in an Arid Region: A Regional Research Overview of the Middle Rio Grande/Rio Bravo Basin  

NASA Astrophysics Data System (ADS)

International and internal borders transect surface and subsurface waters. Such boundaries add complexity to already complicated biophysical and human use trade-offs and interactions between surface and subsurface waters. The surface-subsurface interactions are shaped by a combination of climate change, human community change, and politics and governance decisions. Understanding such dynamics are crucial due to the importance of these waters in arid regions around the world, often affected by borders. This paper provides an overview of the interacting systems involving and affecting surface and subsurface water in the middle Rio Grande/Rio Bravo basin of the United States and Mexico, and the emerging binational research network examining these dynamics. While details are specific to the region, many issues and relationships are generalizable to the Americas and the world.

Heyman, J.

2013-05-01

66

Controls on Cenozoic Chaco Foreland Basin Development, Bolivia  

NASA Astrophysics Data System (ADS)

The up to 200 km wide, Oligocene to Recent Chaco basin is a type example of a retroarc foreland basin system. It is bordered by the Brazilian Shield to the west and by the Subandean Zone to the east. This study combines outcrop stratigraphic, sedimentologic, paleoelevation, seismic, and well data to demonstrate the tectonic, climatic, and eustatic influence on sequence development in the Chaco basin. The Cenozoic fill of the Chaco foreland basin contains an overall coarsening- and thickening-upward stratigraphic succession up to 7.5 km thick and consists of five stratigraphic units: (1) The basal, Oligocene-Miocene-age Petaca Formation consists of dominantly calcretes and fluvial facies in arid setting; (2) The overlying, Late Miocene Yecua Formation records numerous small-scale transgressive-regressive-cycles of marginal marine facies; (3) The Late Late Miocene Tariquia Formation consists of poorly channelized, low-sinuosity anastomosed deposits in semi-arid setting (4) The overlying, Lower Pliocene Guandacay Formation composes of fluvial and distal alluvial fan facies with thin-bedded coal indicating humid paleoclimate; (5) The Late Pliocene, Emborozu Formation consists predominantly of proximal alluvial-fan-facies. Our study shows a marked upsection change in fluvial styles, fluctuations in accommodation space and sediment supply, regulated by basin subsidence. This is supported by a sourceward shift of the depositional system and shown by asymmetrical lateral and vertical variations in grain size and consistent thickness variation and facies changes. Based on our results, the Cenozoic basin development in the Subandean Zone primarily was driven by compressional tectonics and secondarily by climatic and eustatic changes. Tectonically, it formed as response to Andean lithospheric loading, erosion, and shortening by the Subandean thin-skinned fold- and thrust belt. Late Late Miocene arid-to-humid climatic shift contributed to the sedimentation style and rate, whereas global eustacy influenced the sequence only during a Late Miocene marginal-marine incursion.

Uba, C. E.; Heubeck, C.; Ege, H.; Hulka, C.

2004-12-01

67

Alluvial fan response to climatic change: Insights from numerical modeling (Invited)  

NASA Astrophysics Data System (ADS)

Alluvial fans in the western U.S. exhibit a regionally correlative sequence of Plio-Quaternary deposits. Cosmogenic and U-series dating has greatly improved the age control on these deposits and their associated terraces and generally strengthened the case for aggradation during humid-to-arid transitions. Still, the linkages between climate change, upland basin response, and alluvial fan response are not well constrained. Fans may fill and cut as a result of autogenetic processes/internal adjustments, changes in regional temperature (which controls snowmelt-induced flooding), changes in the frequency-size distribution of rainfall events, and/or changes in upslope vegetation. Here I describe the results of a numerical modeling study designed to better constrain the relationships between different end-member forcing mechanisms and the geologic record of alluvial fan deposits and terraces. The model solves the evolution of the fan topography using Exner's equation (conservation of mass) coupled with a nonlinear, threshold-controlled transport relation for sand and gravel. Bank retreat is modeled using an advection equation with a rate proportional to bank shear stress. I begin by considering the building of a fan under conditions of constant water and sediment supply. This simple system exhibits all of the complexity of fans developed under experimental conditions, and it provides insights into the mechanisms that control avulsions and it provides a baseline estimate for the within-fan relief that can result from autogenetic processes. Relationships between the magnitude and period of variations in the sediment-to-water ratio and the geomorphic response of fans are then discussed. I also consider the response of a coupled drainage basin-fan system to changes in climate, including the hydrologic and vegetation response of upland hillslopes. Fans can aggrade or incise in response to the same climatic event depending on the relief of the upstream drainage basin, which exerts a first-order control on sediment supply. The modeled fan response to changes in upstream vegetation, temperature, and precipitation are discussed can compared to available constraints on the timing and spatial distribution of fill and cut events on alluvial fans in the western U.S.

Pelletier, J. D.

2009-12-01

68

Desert pavement characteristics on wadi terrace and alluvial fan surfaces: Wadi Al-Bih, U.A.E. and Oman  

Microsoft Academic Search

In arid mountain areas, the dating and correlation of alluvial depositional surfaces is often uncertain. Especially in regions where the geomorphology is not well known, surface modification by the development of soil and desert pavement may allow the correlation of geomorphic surfaces and estimation of at least their relative ages. Pleistocene wadi terraces and associated alluvial fans occur in Wadi

Asma Al-Farraj; Adrian M Harvey

2000-01-01

69

Valley-fill alluviation during the Little Ice Age (ca. A.D. 1400-1880), Paria River basin and southern Colorado Plateau, United States  

USGS Publications Warehouse

Valley-fill alluvium deposited from ca. A.D. 1400 to 1880 is widespread in tributaries of the Paria River and is largely coincident with the Little Ice Age epoch of global climate variability. Previous work showed that alluvium of this age is a mappable stratigraphic unit in many of the larger alluvial valleys of the southern Colorado Plateau. The alluvium is bounded by two disconformities resulting from prehistoric and historic arroyo cutting at ca. A.D. 1200-1400 and 1860-1910, respectively. The fill forms a terrace in the axial valleys of major through-flowing streams. This terrace and underlying deposits are continuous and interfinger with sediment in numerous small tributary valleys that head at the base of hillslopes of sparsely vegetated, weakly consolidated bedrock, suggesting that eroded bedrock was an important source of alluvium along with in-channel and other sources. Paleoclimatic and high-resolution paleoflood studies indicate that valley-fill alluviation occured during a long-term decrease in the frequency of large, destructive floods. Aggradation of the valleys ended about A.D. 1880, if not two decades earlier, with the beginning of historic arroyo cutting. This shift from deposition to valley entrenchment near the close of the Little Ice Age generally coincided with the beginning of an episode of the largest floods in the preceding 400-500 yr, which was probably caused by an increased recurrence and intensity of flood-producing El Nin??o events beginning at ca. A.D. 1870.

Hereford, R.

2002-01-01

70

Assessment of the Hydrogeochemistry and Groundwater Quality of the Tarim River Basin in an Extreme Arid Region, NW China  

NASA Astrophysics Data System (ADS)

The concentrations of the major and trace elements in the groundwater of the Tarim River Basin (TRB), the largest inland river basin of China, were analyzed before and during rainy seasons to determine the hydrogeochemistry and to assess the groundwater quality for irrigation and drinking purposes. The groundwater within the TRB was slightly alkaline and characterized by high ionic concentrations. The groundwater in the northern sub-basin was fresh water with a Ca2+-HCO3 - water type, whereas the groundwater in the southern and central sub-basins was brackish with a Na+-Cl- water type. Evaporite dissolution and carbonate weathering were the primary and secondary sources of solutes in the groundwater within the basin, whereas silicate weathering played a minor role. The sodium adsorption ratio (SAR), water quality index (WQI), and sodium percentage (%Na) indicated that the groundwater in the northern sub-basin was suitable for irrigation and drinking, but that in the southern and central sub-basins was not suitable. The groundwater quality was slightly better in the wet season than in the dry season. The groundwater could be used for drinking after treatment for B3+, F-, and SO4 2- and for irrigation after control of the sodium and salinity hazards. Considering the high corrosivity ratio of the groundwater in this area, noncorrosive pipes should be used for the groundwater supply. For sustainable development, integrated management of the surface water and the groundwater is needed in the future.

Xiao, Jun; Jin, Zhangdong; Wang, Jin

2014-01-01

71

Study of crop coefficient and the ratio of soil evaporation to evapotranspiration in an irrigated maize field in an arid area of Yellow River Basin in China  

NASA Astrophysics Data System (ADS)

A field experiment was conducted in a maize field in 2006 in an arid area of the Yellow River Basin in China. The daytime evapotranspiration (ETc) and soil evaporation beneath the maize canopy ( E g) were measured by Bowen ratio energy balance method and micro-lysimeters, respectively. The results showed that the total ETc during maize growth season was 696 mm, and the maximum values occurred at about 90-140 days after sowing. The crop coefficient ( K c), which was calculated from the ratio of ETc to reference evapotranspiration (ET0), was quite different from the values reported by other researchers in similar climate areas, with average values of 0.34, 0.47, 1.0 and 0.9 for initial, development, mid-season and late-season stages, respectively. High correlations between leaf area index (LAI) and average K c for every 4 days were obtained. The total E g was 201.4 mm with average values ranged from 0.92 to 2.05 for four growth stages of maize; and accounted for around 28.9 % of ETc. The ratio E g/ETc showed high negative relationship with LAI. These results were very important in precise management of irrigation for maize in Yellow River Basin areas.

Zhang, Chuan; Yan, Haofang; Shi, Haibin; Sugimoto, Hideki

2013-08-01

72

The problems of overexploitation of aquifers in semi-arid areas: the Murcia Region and the Segura Basin (South-east Spain) case  

NASA Astrophysics Data System (ADS)

A general analysis of the problems arising from aquifer exploitation in semi-arid areas such as the Autonomous Region of Murcia, which belongs to the Segura Basin is presented, with particular reference to the Ascoy-Sopalmo aquifer, which is the most overexploited aquifer in Spain. It has suffered intense overabstraction over the last forty years, given renewable water resources of 2 Mm3 yr-1 and abstractions amounting to as much as 55 Mm3 yr-1. This has resulted in the drying of springs, continuous drawdown of water levels (5 m yr-1); piezometric drops (over 30 m in one year, as a consequence of it being a karstic aquifer); increase in pumping costs (elevating water from more than 320 m depth); abandoning of wells (45 reduced to 20), diminishing groundwater reserves, and deteriorating water quality (progressing from a mixed sodium bicarbonate-chloride facies to a sodium chloride one). This is a prime example of poor management with disastrous consequences. In this sense, a series of internal measures is proposed to alleviate the overexploitation of this aquifer and of the Segura Basin, with the aim of contributing to a sustainable future.

Rodríguez-Estrella, T.

2012-05-01

73

Bedload transport in alluvial channels  

USGS Publications Warehouse

Hydraulic, sediment, land-use, and rock-erosivity data of 22 alluvial streams were used to evaluate conditions of bedload transport and the performance of selected bedload-transport equations. Transport categories of transport-limited (TL), partially transport-limited (PTL), and supply-limited (SL) were identified by a semiquantitative approach that considers hydraulic constraints on sediment movement and the processes that control sediment availability at the basin scale. Equations by Parker et al. in 1982, Schoklitsch in 1962, and Meyer-Peter and Muller in 1948 adequately predicted sediment transport in channels with TL condition, whereas the equations of Bagnold in 1980, and Schoklitsch, in 1962, performed well for PTL and SL conditions. Overall, the equation of Schoklitsch predicted well the measured bedload data for eight of 22 streams, and the Bagnold equation predicted the measured data in seven streams.

Bravo-Espinosa, M.; Osterkamp, W.R.; Lopes, V.L.

2003-01-01

74

REACH SPECIFIC CHANNEL STABILIZATION BASED ON COMPREHENSIVE EVALUATION OF VALLEY FILL HISTORY, ALLUVIAL ARCHITECTURE AND GROUNDWATER HYDROLOGY IN A MOUNTAIN STREAM IN THE CENTRAL GREAT BASIN, NEVADA  

EPA Science Inventory

Kingston meadow, located in the Toiyabe Range, is one of many wet meadow complexes threatened by rapid channel incision in the mountain ranges of the central Great Basin. Channel incision can lower the baselevel for groundwater discharge and de-water meadow complexes resulting in...

75

Temporal variations of atmospheric water vapor ?D and ?18O above an arid artificial oasis cropland in the Heihe River Basin  

NASA Astrophysics Data System (ADS)

high temporal resolution measurements of ?D, ?18O, and deuterium excess (d) of atmospheric water vapor provide an improved understanding of atmospheric and ecohydrological processes at ecosystem to global scales. In this study, ?D, ?18O, and d of water vapor and their flux ratios were continuously measured from May to September 2012 using an in situ technique above an arid artificial oasis in the Heihe River Basin, which has a typical continental arid climate. The monthly ?D and ?18O increased slowly and then decreased, whereas the monthly d showed a steady decrease. ?D, ?18O, and d exhibited a marked diurnal cycle, indicating the influence of the entrainment, local evapotranspiration (ET), and dewfall. The departures of ?D, ?18O, and d from equilibrium prediction were significantly correlated with rain amount, relative humidity (RH), and air temperature (T). The "amount effect" was observed during one precipitation event. ?D and ?18O were log linear dependent on water vapor mixing ratio with respective R2 of 17% and 14%, whereas d was significantly correlated with local RH and T, suggesting the less influence of air mass advection and more important contribution of the local source of moisture to atmospheric water vapor. Throughout the experiment, the local ET acted to increase ?D and ?18O, with isofluxes of 102.5 and 23.50 mmol m-2 s-1‰, respectively. However, the dominated effect of entrainment still decreased ?D and ?18O by 10.1 and 2.24‰, respectively. Both of the local ET and entrainment exerted a positive forcing on the diurnal variability in d.

Huang, Lvjun; Wen, Xuefa

2014-10-01

76

Assimilation of Gridded Snow Water Equivalent and Satellite Snowcover Products for Semi- arid Mountain Basins in a Hydrologic Model  

NASA Astrophysics Data System (ADS)

This study examines the Particle Filter (PF) assimilation technique for distributed estimates of snow covered area (SCA) and snow-water equivalent (SWE) to update hydrologic model states. PF is a class of Bayesian filtering algorithms derived from a discrete description of Bayes rule well-suited for updating the nonlinear model states, resulting in improved model outputs. Assimilation runs are applied to the USGS Precipitation Runoff Modeling System (PRMS) hydrologic model using 1-km2 SCA derived from NOAA Advanced Very High Resolution Radiometer imagery and 1-km2 SWE estimates interpolated from National Resources Conservation Service Snow Telemetry (SNOTEL) point measurements for a six-year period (1995-2000). Two headwater basins within the Rio Grande (i.e. upper Rio Grande River basin) and Salt River (i.e. Black River basin) drainages in the Southwestern United States are contrasted. Base runs indicate measured SCA and SWE estimates were consistently lower than values estimated from temperature and precipitation within PRMS. The greatest differences occurred in the relatively complex terrain of the Rio Grande basin, as opposed to the relatively homogeneous terrain of the Black River basin, where differences were small. Differences between modeled and measured snow were different for the accumulation period versus the ablation period and had an elevational trend. Direct insertion of measured snowfields into a version of PRMS calibrated to achieve water balance led to reduced performance in estimating streamflow for the Rio Grande and increased performance in estimating streamflow for the Black River basin. However, PF as a sequential Monte Carlo technique is able to take the most advantage of information content in the data which relaxes the need for restrictive assumptions in direct insertion and even other assimilation techniques. Therefore, in this study we demonstrate the features of such a filtering technique with the potential to estimate the uncertainty of updated SCA and SWE in an ensemble framework.

Dressler, K. A.; Moradkhani, H.

2006-12-01

77

A 30000 year record of vegetation dynamics at a semi-arid locale in the Great Basin  

Microsoft Academic Search

Plant macrofossils extracted from fossil woodrat (Neotoma spp.) middens at a single locale in the northwestern Great Basin were used to examine vegetation dynamics during the last 30 000 yr. Although the modem assemblage of xeric species at the study site is a recent occurrence, a large propor- tion of the modem plant taxa near the study locale were also

Robert S. Nowak

78

Nuclear-waste isolation in the unsaturated zone of arid regions  

SciTech Connect

The vadose zone in arid regions is considered as a possible environment for geologic isolation of nuclear waste. There are several topographic and lithologic combinations in the vadose zone of arid regions that may lend themselves to waste isolation considerations. In some cases, topographic highs such as mesas and interbasin ranges - comprised of several rock types, may contain essentially dry or partially saturated conditions favorable for isolation. The adjacent basins, especially in the far western and southwestern US, may have no surface or subsurface hydrologic connections with systems ultimately leading to the ocean. Some rock types may have the favorable characteristics of very low permeability and contain appropriate minerals for the strong chemical retardation of radionuclides. Environments exhibiting these hydrologic and geochemical attributes are the areas underlain by tuffaceous rocks, relatively common in the Basin and Range geomorphic province. Adjacent valley areas, where tuffaceous debris makes up a significant component of valley fill alluvium, may also contain thick zones of unsaturated material, and as such also lend themselves to strong consideration as respository environments. This paper summarizes the aspects of nuclear waste isolation in unsaturated regimes in alluvial-filled valleys and tuffaceous rocks of the Basin and Range province.

Wollenberg, H.A.; Wang, J.S.Y.; Korbin, G.

1982-05-01

79

Attribution of satellite-observed vegetation trends in a hyper-arid region of the Heihe River basin, Western China  

NASA Astrophysics Data System (ADS)

Terrestrial vegetation dynamics are closely influenced by both climate and by both climate and by land use and/or land cover change (LULCC) caused by human activities. Both can change over time in a monotonic way and it can be difficult to separate the effects of climate change from LULCC on vegetation. Here we attempt to attribute trends in the fractional green vegetation cover to climate variability and to human activity in Ejina Region, a hyper-arid landlocked region in northwest China. This region is dominated by extensive deserts with relatively small areas of irrigation located along the major water courses as is typical throughout much of Central Asia. Variations of fractional vegetation cover from 2000 to 2012 were determined using Moderate Resolution Imaging Spectroradiometer (MODIS) vegetation index data with 250 m spatial resolution over 16-day intervals. We found that the fractional vegetation cover in this hyper-arid region is very low but that the mean growing season vegetation cover has increased from 3.4% in 2000 to 4.5% in 2012. The largest contribution to the overall greening was due to changes in green vegetation cover of the extensive desert areas with a smaller contribution due to changes in the area of irrigated land. Comprehensive analysis with different precipitation data sources found that the greening of the desert was associated with increases in regional precipitation. We further report that the area of land irrigated each year can be predicted using the runoff gauged 1 year earlier. Taken together, water availability both from precipitation in the desert and runoff inflow for the irrigation agricultural lands can explain at least 52% of the total variance in regional vegetation cover from 2000 to 2010. The results demonstrate that it is possible to separate the satellite-observed changes in green vegetation cover into components due to climate and human modifications. Such results inform management on the implications for water allocation between oases in the middle and lower reaches and for water management in the Ejina oasis.

Wang, Y.; Roderick, M. L.; Shen, Y.; Sun, F.

2014-09-01

80

Using cosmogenic nuclides to contrast rates of erosion and sediment yield in a semi-arid, arroyo-dominated landscape, Rio Puerco Basin, New Mexico  

USGS Publications Warehouse

Analysis of in-situ-produced 10Be and 26Al in 52 fluvial sediment samples shows that millennial-scale rates of erosion vary widely (7 to 366 m Ma-1) through the lithologically and topographically complex Rio Puerco Basin of northern New Mexico. Using isotopic analysis of both headwater and downstream samples, we determined that the semi-arid, Rio Puerco Basin is eroding, on average, about 100 m Ma-1. This rapid rate of erosion is consistent with estimates made using other techniques and is likely to result from a combination of easily eroded lithologies, sparse vegetation, and monsoon-dominated rainfall. Data from 331 stream water samples collected by the US Geological Survey between 1960 and 1995 are consistent with basin-wide, average chemical denudation rates of only about 1??4 m Ma-1; thus, the erosion rates we calculate may be considered rates of sediment generation because physical weathering accounts for almost 99 per cent of mass loss. The isotopic data reveal that sediment is generally well mixed downstream with the area-weighted average sediment generation rate for 16 headwater samples (234 ton km-2 a-1 for basin area 170 to 1169 km2) matching well that estimated from a single sample collected far downstream (238 ton km-2 a-1, basin area = 14 225 km2). A series of 15 samples, collected from an arroyo wall and representing deposition through the late Holocene, indicates that 10Be concentration in sediment delivered by the fluvial system has not changed appreciably over the last 1200 years despite at least two cycles of arroyo cutting and filling. Other samples (n = 21) were collected along the drainage network. Rio Puerco erosion rates scale directly with a variety of metrics describing vegetation, precipitation, and rock erodibility. Using the headwater basins for calibration, the erosion rates for both the downstream samples and also the data set as a whole, are best modelled by considering a combination of relief and vegetation metrics, both of which co-vary with precipitation and erodibility as inferred from lithology. On average, contemporary sediment yields, determined by monitoring suspended-sediment discharge, exceed cosmogenically determined millennial-scale erosion rates by nearly a factor of two. This discrepancy, between short-term rates of sediment yield and long-term rates of erosion, suggests that more sediment is currently being exported from the basin than is being produced. Because the failure of incised channel walls and the head cutting of arroyo complexes appear to be the main sources of channel sediment today, this incongruence between rates of sediment supply and sediment yield is likely to be transitory, reflecting the current states of the arroyo cycle and perhaps the influence of current or past land-use patterns. Copyright ?? 2005 John Wiley & Sons, Ltd.

Bierman, P.R.; Reuter, J.M.; Pavich, M.; Gellis, A.C.; Caffee, M.W.; Larsen, J.

2005-01-01

81

Sedimentary facies, depositional environments and palaeogeographic evolution of the Neogene Denizli Basin, SW Anatolia, Turkey  

NASA Astrophysics Data System (ADS)

The Denizli Basin (southwestern Anatolia, Turkey) contains a record of environmental changes dating since the Early Miocene. Detailed facies analysis of the Neogene formations in this half-graben enables us to document successive depositional regimes and palaeogeographic settings. Sedimentation commenced in the Early Miocene with the deposition of alluvial-fan and fluvial facies (K?z?lburun Formation). At this stage, alluvial fans sourced from elevated areas to the south prograded towards the basin centre. The Middle Miocene time saw the establishment of marginal lacustrine and wetland environments followed by the development of a shallow lake (Sazak Formation). The uppermost part of this unit consists of evaporitic saline lake and saline mudflat facies that grade upward into brackish lacustrine deposits of Late Miocene-Pliocene age (Kolankaya Formation). The lake became shallower at the end of the Pliocene time, as is indicated by expansion shoreface/foreshore facies. In the Early Quaternary, the Denizli Basin was transformed into a graben by the activation of ESE-trending normal faults. Alluvial fans were active at the basin margins, whereas a meandering river system occupied the basin central part. Oxygen isotope data from carbonates in the successive formations show an alternation of wetter climatic periods, when fresh water settings predominated, and very arid periods, when the basin hosted brackish to hypersaline lakes. The Neogene sedimentation was controlled by an active, ESE-trending major normal fault along the basin's southern margin and by climatically induced lake-level changes. The deposition was more or less continuous from the Early Miocene to Late Pliocene time, with local unconformities developed only in the uppermost part of the basin-fill succession. The unconformable base of the overlying Quaternary deposits reflects the basin's transformation from a half-graben into a graben system.

Alçiçek, Hülya; Varol, Baki; Özkul, Mehmet

2007-12-01

82

Phosphorous concentration, solubility and species in the groundwater in a semi-arid basin, southern Malayer, western Iran  

NASA Astrophysics Data System (ADS)

In areas of intensive crop production, continual phosphorous (P) applications as P fertilizer and farmyard manure have been made at levels exceeding crop requirement. As a result, surface soil accumulations of P have occurred to such an extent that loss of P in surface runoff and a high risk for P transfer into groundwater in concentrations exceeding the groundwater quality standard has become a priority management concern. Phosphorous content of groundwater was determined in order to examine dissolved P concentration and species in the groundwater and mineral solubilitiy in a semi-arid region of southern Malayer, western Iran. The speciation for P in groundwater was calculated using geochemical speciation model PHREEQC. The concentration of total P in the groundwater (0.01-2.56 mg P l-1) and estimated concentrations of HPO4 2- (49.5-89%), H2PO4 - (1.5-17.3%), CaHPO4 + (5.7-36.1%), and CaPO4 - (1.4-12.2%) varied considerably amongst the groundwater. Results suggest that the concentration of P in the groundwater could be primarily controlled by the solubility of octacalcium phosphate and ?-tricalcium phosphate. Large amounts of P fertilizer, inadequate management of P fertilization, and low irrigation efficiency, coupled with sandy soils in some parts of the study area could be mainly responsible for the greater P in the groundwater. In general, the greater the dissolved P concentration in the groundwater, the closer the solution was to equilibrium with respect to the more soluble Ca-phosphate minerals. The groundwater P content could be potentially used to identify areas where management approaches, such as P applied and crop type planted, could be adjusted to different types of soils, geology and topography.

Jalali, Mohsen

2009-05-01

83

Influences of Leaf Area Index estimations on water balance modeling in a Mediterranean semi-arid basin  

NASA Astrophysics Data System (ADS)

In the present work, the role played by vegetation parameters, necessary to the hydrological distributed modeling, is investigated focusing on the correct use of remote sensing products for the evaluation of hydrological losses in the soil water balance. The research was carried out over a medium-sized river basin in Southern Italy, where the vegetation status is characterised through a data-set of multi-temporal NDVI images. The model adopted uses one layer of vegetation whose status is defined by the Leaf Area Index (LAI), which is often obtained from NDVI images. The inherent problem is that the vegetation heterogeneity - including soil disturbances - has a large influence on the spectral bands and so the relation between LAI and NDVI is not unambiguous. We present a rationale for the basin scale calibration of a non-linear NDVI-LAI regression, based on the comparison between NDVI values and literature LAI estimations of the vegetation cover in recognized landscape elements of the study catchment. Adopting a process-based model (DREAM) with a distributed parameterisation, the influence of different NDVI-LAI regression models on main features of water balance predictions is investigated. The results show a significant sensitivity of the hydrological losses and soil water regime to the alternative LAI estimations. These crucially affects the model performances especially in low-flows simulation and in the identification of the intermittent regime.

Gigante, V.; Iacobellis, V.; Manfreda, S.; Milella, P.; Portoghese, I.

2009-06-01

84

Configuration of water resources for a typical river basin in an arid region of China based on the ecological water requirements (EWRs) of desert riparian vegetation  

NASA Astrophysics Data System (ADS)

Desert riparian vegetation is a natural cover promoting the stability and development of inland river ecosystems in arid regions. Calculating the ecological water requirements (EWRs) of desert riparian vegetation is an important step in achieving reasonable water utilization. Therefore, this study examined the Tarim River, located in an extremely arid region of China, and collected relevant data on hydrology, weather and vegetation using remote sensing. Subsequently, we analyzed the spatial distribution of the desert riparian vegetation in four sections of the Tarim River and calculated the EWR of the desert riparian vegetation using the phreatic evaporation model; additionally, we determined the required runoffs at five hydrologic stations based on the water balance principle. Ultimately, the necessary protection ranges and goals for desert riparian vegetation were established according to the water resource variations in the Tarim River. Our research showed that the total area of desert riparian vegetation along the Tarim River is 16,285.3 km2; this distribution area gradually decreased as the distance from the river increased, and areas varied in the different river sections. The EWRs of desert riparian vegetation from Sections 1 to 5 are 5.698 × 108, 7.585 × 108, 4.900 × 108, 4.101 × 108 m3 and 1.078 × 108 m3, respectively. Therefore, the total EWR of the study region is 23.362 × 108 m3. In terms of the transpiration law of the "unimodal type", the peak value of EWR of natural vegetation occurs in July, and the decreasing trend appears in the other months. Based on the water balance principle, the required runoffs in Alar, Xinquman, Yingbaza, Wusiman and Qiala were determined to be 47.105 × 108, 35.174 × 108, 22.734 × 108, 15.775 × 108 and 7.707 × 108 m3, respectively. According to the water resource frequency and the EWR of the desert riparian vegetation along the Tarim River, we divided the region into three protection ranges: key protection (8.9-11.8 km from the river), basic protection (15.8-21.8 km from the river) and influence protection (43.0 km from the river). This research not only provides a reasonable calculation method for EWR on the scale of a river basin but also supports the healthy development of the desert riparian vegetation ecosystem and helps to achieve the optimal water allocation for this river.

Ling, Hongbo; Guo, Bin; Xu, Hailiang; Fu, Jinyi

2014-11-01

85

Tectonically induced climate and its control on the distribution of depositional systems in a continental foreland basin, Cloverly and Lakota Formations (Lower Cretaceous) of Wyoming, U.S.A.  

NASA Astrophysics Data System (ADS)

Continental sediments of the Cloverly and Lakota Formations (Lower Cretaceous) in Wyoming are subdivided into three depositional systems: perennial to intermittent alluvial, intermittent to ephemeral alluvial, and playa. Chert-bearing sandstones, conglomerates, carbonaceous mudrocks, blocky mudrocks, and skeletal limestones were deposited by perennial to intermittent alluvial systems. Carbonaceous mudrocks contain abundant wood fragments, cuticle and cortical debris, and other vascular plant remains representing deposition in oxbow lakes, abandoned channels, and on floodplains under humid to seasonal conditions. Intraformational conglomerates, sandstones, bioturbated and blocky mudrocks with caliche nodules, and bioturbated limestones characterize deposition in intermittent to ephemeral alluvial systems. Bioturbated limestones are encased in bioturbated mudrocks with abundant pseudo-slickensides. The presence of caliche nodules in some of the blocky to bioturbated mudrocks is consistent with supersaturation and precipitation of calcium carbonate from groundwater under semi-arid conditions. Caliche nodules, pseudo-slickensides, and carbonate-rich floodplain sediments are interpreted to have been deposited by intermittent to ephemeral alluvial systems under seasonal to semi-arid climatic conditions. Laminated mudrocks, siltstones, vuggy carbonates, bedded to nodular evaporites, pebbly mudrocks, and diamictites were deposited in evaporative alkaline lakes or playas. Pebbly mudrocks and diamictites are interpreted to represent deposition from channelized and unchannelized hyperconcentrated flows on a playa, resulting from intense rain events within the basin. The areal abundance and distribution of these depositional systems change systematically across the overfilled portion of the Early Cretaceous Cordilleran foreland basin in Wyoming. The lower part (A-interval) of the Cloverly and Lakota Formations is characterized by deposits of perennial to intermittent rivers that existed 300 to 1000 km east of the Sevier fold-and-thrust belt. Proximal to the Sevier fold-and-thrust belt, the A-interval of the Cloverly Formation and upper Ephraim Formation of the Gannett Group are typified by deposits of intermittent to ephemeral rivers and their associated floodplains. In the middle part (B-interval) of the Cloverly Formation, intermittent to ephemeral alluvial systems expand to 600 km into the basin. The upper part (C-interval) of the Cloverly Formation is characterized by playa deposits in the Bighorn and Wind River Basins and intermittent to ephemeral alluvial deposits along the front of the ancestral Sevier Mountains. Deposits of perennial to intermittent alluvial systems in the C-interval of the Cloverly and Lakota Formations are restricted to the Black Hills region, almost 900 km to the east of the Sevier Mountains. The change in the areal distribution of depositional systems through time within this continental foreland basin may be attributed to the development of a rain shadow associated with the uplift of the Sevier Mountains in the Early Cretaceous.

Elliott, William S.; Suttner, Lee J.; Pratt, Lisa M.

2007-12-01

86

Evaluation of the importance of clay confining units on groundwater flow in alluvial basins using solute and isotope tracers: the case of Middle San Pedro Basin in southeastern Arizona (USA)  

NASA Astrophysics Data System (ADS)

As groundwater becomes an increasingly important water resource worldwide, it is essential to understand how local geology affects groundwater quality, flowpaths and residence times. This study utilized multiple tracers to improve conceptual and numerical models of groundwater flow in the Middle San Pedro Basin in southeastern Arizona (USA) by determining recharge areas, compartmentalization of water sources, flowpaths and residence times. Ninety-five groundwater and surface-water samples were analyzed for major ion chemistry (water type and Ca/Sr ratios) and stable (18O, 2H, 13C) and radiogenic (3H, 14C) isotopes, and resulting data were used in conjunction with hydrogeologic information (e.g. hydraulic head and hydrostratigraphy). Results show that recent recharge (<60 years) has occurred within mountain systems along the basin margins and in shallow floodplain aquifers adjacent to the San Pedro River. Groundwater in the lower basin fill aquifer (semi confined) was recharged at high elevation in the fractured bedrock and has been extensively modified by water-rock reactions (increasing F and Sr, decreasing 14C) over long timescales (up to 35,000 years BP). Distinct solute and isotope geochemistries between the lower and upper basin fill aquifers show the importance of a clay confining unit on groundwater flow in the basin, which minimizes vertical groundwater movement.

Hopkins, Candice B.; McIntosh, Jennifer C.; Eastoe, Chris; Dickinson, Jesse E.; Meixner, Thomas

2014-06-01

87

Impact of wind erosion on detecting active tectonics from geomorphic indexes in extremely arid areas: a case study from the Hero Range, Qaidam Basin, NW China  

NASA Astrophysics Data System (ADS)

Geomorphologic analysis has been used widely to detect active tectonics in regions where fluvial incision is the major erosional process. In this paper, however, we assess the feasibility of utilizing these frequently-used geomorphic indexes (e.g., hypsometric curves, longitudinal channel profiles, normalized stream length-gradient (SLK) index) to determine active tectonics in extremely arid areas where wind erosion also plays an important role. The case study is developed on the Hero Range in the western Qaidam Basin, one of the driest regions on Earth with severe wind erosion since late Pliocene. The result shows that in the west and south sectors, as well as the western part of the east sector, of the Hero Range where fluvial incision prevails, these geomorphic indexes are good indicators of active faulting and consistent with the geological result based on study of fault traces, scarps, faulted Holocene fans and historical seismicity within the past four decades. In contrast, along the northeastern margin (the NE and the SE parts of the east sector) of the range where wind erosion is also important, the results from the geomorphic indexes show quite active tectonics, contrary with the geological evidence favoring weakly active tectonics. Moreover, the positive SLK anomaly lies oblique to the fault trace and the anticline axis but parallel to the wind direction. To reconcile the contradiction, we propose that wind erosion caused by northwestern winds has a tendency to make geomorphic indexes exhibit anomalous values that indicate higher activities, by way of (1) lowering the base-level to generate knickpoints on the longitudinal channel profiles and therefore positive SLK anomalies, and (2) lateral erosion of the mountain front making the hypsometric curves and even the longitudinal channel profiles more convex, and producing obvious slope breaks.

Wu, Lei; Xiao, Ancheng; Yang, Shufeng

2014-11-01

88

Point sources of emerging contaminants along the Colorado River Basin: Source water for the arid Southwestern United States  

USGS Publications Warehouse

Emergingcontaminants (ECs) (e.g., pharmaceuticals, illicit drugs, personal care products) have been detected in waters across the UnitedStates. The objective of this study was to evaluate pointsources of ECs along the ColoradoRiver, from the headwaters in Colorado to the Gulf of California. At selected locations in the ColoradoRiver Basin (sites in Colorado, Utah, Nevada, Arizona, and California), waste stream tributaries and receiving surface waters were sampled using either grab sampling or polar organic chemical integrative samplers (POCIS). The grab samples were extracted using solid-phase cartridge extraction (SPE), and the POCIS sorbents were transferred into empty SPEs and eluted with methanol. All extracts were prepared for, and analyzed by, liquid chromatography-electrospray-ion trap mass spectrometry (LC-ESI-ITMS). Log Dow values were calculated for all ECs in the study and compared to the empirical data collected. POCIS extracts were screened for the presence of estrogenic chemicals using the yeast estrogen screen (YES) assay. Extracts from the 2008 POCIS deployment in the Las Vegas Wash showed the second highest estrogenicity response. In the grab samples, azithromycin (an antibiotic) was detected in all but one urban waste stream, with concentrations ranging from 30 ng/L to 2800 ng/L. Concentration levels of azithromycin, methamphetamine and pseudoephedrine showed temporal variation from the Tucson WWTP. Those ECs that were detected in the main surface water channels (those that are diverted for urban use and irrigation along the ColoradoRiver) were in the region of the limit-of-detection (e.g., 10 ng/L), but most were below detection limits.

Jones-Lepp, Tammy L.; Sanchez, Charles; Alvarez, David A.; Wilson, Doyle C.; Taniguchi-Fu, Randi-Laurant

2012-01-01

89

Point sources of emerging contaminants along the Colorado River Basin: source water for the arid Southwestern United States.  

PubMed

Emerging contaminants (ECs) (e.g., pharmaceuticals, illicit drugs, personal care products) have been detected in waters across the United States. The objective of this study was to evaluate point sources of ECs along the Colorado River, from the headwaters in Colorado to the Gulf of California. At selected locations in the Colorado River Basin (sites in Colorado, Utah, Nevada, Arizona, and California), waste stream tributaries and receiving surface waters were sampled using either grab sampling or polar organic chemical integrative samplers (POCIS). The grab samples were extracted using solid-phase cartridge extraction (SPE), and the POCIS sorbents were transferred into empty SPEs and eluted with methanol. All extracts were prepared for, and analyzed by, liquid chromatography-electrospray-ion trap mass spectrometry (LC-ESI-ITMS). Log D(OW) values were calculated for all ECs in the study and compared to the empirical data collected. POCIS extracts were screened for the presence of estrogenic chemicals using the yeast estrogen screen (YES) assay. Extracts from the 2008 POCIS deployment in the Las Vegas Wash showed the second highest estrogenicity response. In the grab samples, azithromycin (an antibiotic) was detected in all but one urban waste stream, with concentrations ranging from 30ng/L to 2800ng/L. Concentration levels of azithromycin, methamphetamine and pseudoephedrine showed temporal variation from the Tucson WWTP. Those ECs that were detected in the main surface water channels (those that are diverted for urban use and irrigation along the Colorado River) were in the region of the limit-of-detection (e.g., 10ng/L), but most were below detection limits. PMID:22684090

Jones-Lepp, Tammy L; Sanchez, Charles; Alvarez, David A; Wilson, Doyle C; Taniguchi-Fu, Randi-Laurant

2012-07-15

90

Application of a stochastic weather generator to assess climate change impacts in a semi-arid climate: The Upper Indus Basin  

NASA Astrophysics Data System (ADS)

Assessing local climate change impacts requires downscaling from Global Climate Model simulations. Here, a stochastic rainfall model (RainSim) combined with a rainfall conditioned weather generator (CRU WG) have been successfully applied in a semi-arid mountain climate, for part of the Upper Indus Basin (UIB), for point stations at a daily time-step to explore climate change impacts. Validation of the simulated time-series against observations (1961-1990) demonstrated the models' skill in reproducing climatological means of core variables with monthly RMSE of <2.0 mm for precipitation and ?0.4 °C for mean temperature and daily temperature range. This level of performance is impressive given complexity of climate processes operating in this mountainous context at the boundary between monsoonal and mid-latitude (westerly) weather systems. Of equal importance the model captures well the observed interannual variability as quantified by the first and last decile of 30-year climatic periods. Differences between a control (1961-1990) and future (2071-2100) regional climate model (RCM) time-slice experiment were then used to provide change factors which could be applied within the rainfall and weather models to produce perturbed ‘future' weather time-series. These project year-round increases in precipitation (maximum seasonal mean change:+27%, annual mean change: +18%) with increased intensity in the wettest months (February, March, April) and year-round increases in mean temperature (annual mean +4.8 °C). Climatic constraints on the productivity of natural resource-dependent systems were also assessed using relevant indices from the European Climate Assessment (ECA) and indicate potential future risk to water resources and local agriculture. However, the uniformity of projected temperature increases is in stark contrast to recent seasonally asymmetrical trends in observations, so an alternative scenario of extrapolated trends was also explored. We conclude that interannual variability in climate will continue to have the dominant impact on water resources management whichever trajectory is followed. This demonstrates the need for sophisticated downscaling methods which can evaluate changes in variability and sequencing of events to explore climate change impacts in this region.

Forsythe, N.; Fowler, H. J.; Blenkinsop, S.; Burton, A.; Kilsby, C. G.; Archer, D. R.; Harpham, C.; Hashmi, M. Z.

2014-09-01

91

Aridity Modulates N Availability in Arid and Semiarid Mediterranean Grasslands  

PubMed Central

While much is known about the factors that control each component of the terrestrial nitrogen (N) cycle, it is less clear how these factors affect total N availability, the sum of organic and inorganic forms potentially available to microorganisms and plants. This is particularly true for N-poor ecosystems such as drylands, which are highly sensitive to climate change and desertification processes that can lead to the loss of soil nutrients such as N. We evaluated how different climatic, abiotic, plant and nutrient related factors correlate with N availability in semiarid Stipa tenacissima grasslands along a broad aridity gradient from Spain to Tunisia. Aridity had the strongest relationship with N availability, suggesting the importance of abiotic controls on the N cycle in drylands. Aridity appeared to modulate the effects of pH, plant cover and organic C (OC) on N availability. Our results suggest that N transformation rates, which are largely driven by variations in soil moisture, are not the direct drivers of N availability in the studied grasslands. Rather, the strong relationship between aridity and N availability could be driven by indirect effects that operate over long time scales (decades to millennia), including both biotic (e.g. plant cover) and abiotic (e.g. soil OC and pH). If these factors are in fact more important than short-term effects of precipitation on N transformation rates, then we might expect to observe a lagged decrease in N availability in response to increasing aridity. Nevertheless, our results suggest that the increase in aridity predicted with ongoing climate change will reduce N availability in the Mediterranean basin, impacting plant nutrient uptake and net primary production in semiarid grasslands throughout this region. PMID:23565170

Delgado-Baquerizo, Manuel; Maestre, Fernando T.; Gallardo, Antonio; Quero, José L.; Ochoa, Victoria; García-Gómez, Miguel; Escolar, Cristina; García-Palacios, Pablo; Berdugo, Miguel; Valencia, Enrique; Gozalo, Beatriz; Noumi, Zouhaier; Derak, Mchich; Wallenstein, Matthew D.

2013-01-01

92

Late Miocene to Plio-Pleistocene fluvio-lacustrine system in the Karacasu Basin (SW Anatolia, Turkey): Depositional, paleogeographic and paleoclimatic implications  

NASA Astrophysics Data System (ADS)

The sedimentary record of the late Cenozoic Karacasu Basin, a long-lived continental half-graben from southwestern Turkey, is characterized by siliciclastic and carbonate deposits. Sedimentation was controlled by an active NW-SE trending major normal fault along the basin's southern margin and by climatically-induced lake-level changes. Detailed facies analysis subdivides the entire Neogene-Quaternary basin-fill into three distinct litostratigraphic units representing paleogeographic changes and sedimentation patterns throughout the basin evolution. Sedimentation commenced in the late Miocene with the deposition of proximal-medial alluvial fan and fluvial facies (Damdere Formation; FA1). At this stage, alluvial fans developed in elevated areas to the south, prograding towards the basin center. At the beginning of the Pliocene, fresh to slightly alkaline, shallow lake deposits (FA2a) of the Karacaören Formation formed. The lake became open and meromictic conditions developed (FA2b). Pollen data from the FA2b facies show that climate was arid to humid. Climate probably changed cyclically through time producing alternation of Artemisia steppe (cold and dry periods) and more forested vegetation (warm and wet). The open lake facies passes upwards into lake margin facies (FA2c), but it was still dominated by alkaline to slightly saline lake conditions. Sedimentation was almost continuous from the late Miocene to Pleistocene. In the early Quaternary, the basin was dissected by the re-activation of basin bounding faults. The unconformable base of the overlying Quaternary deposits (Karacasu Formation; FA3) reflected the basin's transformation from a half-graben into a full-graben system. Oxygen isotope data from carbonates show an alternation of humid climatic periods, when freshwater settings predominated, and semiarid/arid periods in which the basin hosted alkaline and saline water lakes. Neotectonic activity has rejuvenated many of the basin-bounding faults, causing development of talus aprons and local alluvial fans. The basin was progressively incised by modern rivers that have largely smoothed out the topographic relief of the graben margins. id="ab0010" The study highlights to the paleo-geography/-climatology in the east Mediterranean.

Alçiçek, Hülya; Jiménez-Moreno, Gonzalo

2013-06-01

93

Taphonomy and paleoecology of nonmarine mollusca: indicators of alluvial plain lacustrine sedimentation, upper part of the Tongue River Member, Fort Union Formation ( Paleocene), Northern Powder River Basin, Wyoming and Montana ( USA).  

USGS Publications Warehouse

The composition, species abundances, and spatial and temporal distributions of mollusc assemblages were controlled by the environments in which they lived and the depositional processes that affected the molluscs after death and before final burial. Post-mortem transport, reworking and concentration of shells, and mixing of faunal elements from discrete habitats produced a taphonomic 'overprint' on assemblage characteristics that directly reflects the processes of alluvial plain and floodbasin lacustrine sedimentation. The 'overprint' can be interpreted from outcrop analysis of molluscan biofabric, which consists of: 1) orientation, fragmentation, size-sorting, abrasion, density, and dispersion of shells, 2) the nature and extent of shell-infilling, and 3) ratio of articulated to disarticulated bivalves. Taphonomic characteristics were used with sedimentological properties to differentiate in-place, reworked, transported, and ecologically mixed mollusc assemblages. This study also defines the paleoecology of habitat preferences of mollusc species as a basis for recognition of the environments in which these assemblages were deposited: 1) large floodbasin lakes, 2) small floodbasin lakes, and 3) crevasse deltas and splays. Integration of sedimentology and paleoecology provides an interdisciplinary approach to the interpretation of alluvial environments through time in the Tongue River Member. -Authors

Hanley, J.H.; Flores, R.M.

1987-01-01

94

Artificial recharge in arid zone- Example from the Arava Valley- Israel  

NASA Astrophysics Data System (ADS)

In arid zones direct recharge from rainfall is negligible. The indirect recharge like recharging of flood water is the principal source of water of the alluvial aquifers in arid environment. Flooding of ephemeral streams occur as a consequence of the rain intensity and its pattern, the basin size and the geomorphic settings as slops, vegetation and soil properties. In the Arava Valley there are several reservoirs that act as diversion levees. They were constructed on few ravines for two reasons. (1) to store large volumes of floodwater for direct use in nearby agricultural fields. (2) to enhance the recharge to the local alluvial aquifers. Since flood duration is relatively short compared to the infiltration (percolation) rate, it was assumed that by storing the water in the reservoirs it will increase the recharge volume because of higher water head, longer resistance time and larger surface area available for infiltration. Unfortunately, accumulation of silts and clays in the reservoirs clogged them to direct infiltration. The accumulation of silt and clay in the reservoirs is typically to arid zones where lack of vegetation cover creates a very high erosion rate and transportation of large amounts of sediment at the duration of the water flowing on the stream channel bed. To bypass the problem of reduction in the direct recharge inside the reservoirs because of clogging, and to continue the artificial recharge into the aquifer, two kinds of artificial recharge system are operating in the Arava Valley. In one site we use a system that is similar to the conventional spreading ponds system. The big reservoir is using to store the flood water and as a settling pond. The clean water is diverted to three infiltration ponds. In the rest five reservoirs we construct a drainage pipeline close to the bottom of the levee that allow us to release the clean water (after settling of the fine particles) downstream in a slow rate that is much more efficiency for artificial recharge than in high velocity. Monitoring after the recharge water is very important and in some cases very problematic. In cases where the groundwater is shallow (10-20 m' depth) the response to the recharge is quickly and takes few days (rising in water level and or decreasing in the salinity). But in cases where the water level is very deep (about 60-110 m' in most of the area) the response to the recharge can takes few months. At this condition, it is impossible to distinguish whether the rising in the water level and or decreasing in the salinity is a result of the artificial recharge or it is a result of natural lateral flow in the aquifer itself.

Guttman, Joseph

2010-05-01

95

Radiogenic 3He/4He Estimates and Their Effect on Calculating Plio-Pleistocene Cosmogenic 3He Ages of Alluvial-Fan Terraces in the Lower Colorado River Basin, USA  

NASA Astrophysics Data System (ADS)

Several alluvial-fan terraces near Topock, AZ were created by successive entrenchment of Pliocene and Pleistocene alluvial-fan gravels shed from the adjacent Black Mountains along the lower Colorado River corridor below Hoover Dam. These fans interfinger with and overlie main-stem Colorado River sands and gravels and grade to terrace levels that correspond with pre-existing elevations of the Colorado River. Absolute dates for the ages of Quaternary deposits on the lower Colorado River are rare and cosmogenic 3He age estimates of these surfaces would help constrain the timing of aggradation and incision in the lower Colorado River corridor. We analyzed individual basalt boulders from several terrace surfaces for total 3He/4He concentrations to calculate cosmogenic 3He ages of each fan terrace; 3He/4He values, expressed as R/Ra where Ra is the 3He/4He of air, range from 0.29 to 590. Black Mountain volcanic rocks have reported K-Ar ages between 15 and 30 Ma and basalt samples from adjacent alluvial fans contain 0.42 to 47× 1012 at/g of 4He, which has likely accumulated due to nuclear processes. The amount of radiogenic 3He/4He can be significant in old rocks with young exposure ages and can complicate determination of cosmogenic 3 He content. Alpha-decay of U, Th, and their daughter isotopes produces large amounts of 4He, whereas significant amounts of radiogenic 3He are only produced through the neutron bombardment of Li and subsequent beta-decay of tritium. We measured Li, U, Th, major and rare-earth element concentrations in whole-rock basalts and mineral separates. These concentrations are used to estimate the ratio of radiogenic helium contributed to the total helium system in our samples. Li concentrations typically range from 6 to 17 ppm, with one outlier of 62 ppm. U contents range from <0.1 to 2.7 ppm and Th contents range from 0.4 to 15.3 ppm. Based on these values, our calculations predict that the average radiogenic helium (R/Ra) contributed to the total helium in Black Mountain basalt samples is 0.011. Other noble gas studies have shown that radiogenic 3He/4He is independent of the U content, nearly independent of the Th content, and strongly influenced by the Li content of a rock; we find the same results. It is assumed that mantle gases are released when the sample is crushed into a fine powder before melting in a furnace under vacuum. To correct for the possible presence of mantle gases in our age-calculations, we crushed two samples under vacuum to measure the R/Ra value (7.9 and 16.03) of mantle helium trapped in fluid inclusions in olivines and pyroxenes. Based on our 3He corrections and calculations, boulders on these alluvial fans range in age from 10 ka to 2.7 Ma.

Fenton, C.; Pelletier, J.

2005-12-01

96

Anthropogenic driven modern recharge and solute flux to arid basin aquifers: Results and implications for sustainability based on field observations and computational modeling  

NASA Astrophysics Data System (ADS)

Development of natural grass and scrubland for agricultural use (grazing and irrigated agriculture) has changed recharge mechanisms and raised questions about the sustainability of groundwater resources in the Trans-Pecos region of Texas. When quantifying the availability of water in the region, previous research relied upon the ';classic' conceptual model; minimal modern recharge, no widespread recharge on basin floors, and no recharge from anthropogenic sources such as irrigation return flow. Increasing nitrate (NO3-) concentrations in basin groundwater from the 1950's to present (median increase of 3-4 mg/L (as NO3-) over approximately 40 years) belie the model of limited modern recharge and pose a risk to water quality throughout the basins. We posit that grazing practices and irrigated agriculture have affected hydrologic processes in the basins by altering 1) the vegetation regime on the basin floors and 2) the magnitude and spatial distribution of infiltrating water. These impacts have increased recharge and transported Cl- and mobile nitrogen (N) from the vadose zone to the underlying groundwater. Using a spatially distributed net infiltration model, we estimate that between 7-20% of recharge occurring in the basins results from widespread recharge on the basin floors and that between 1960 and 2000 an additional 8.5 x 10^3 to 1.2 x 10^6 cubic meters of irrigation water has potentially been returned through irrigation return flow. Vadose zone cores collected from beneath land used for agricultural purposes document changes in water content and pore water chemistry that imply an increase in downward flux of moisture and solute resulting from human alteration of the natural system; reservoirs of NO3- and Cl- typically observed beneath the rooting depth of un-impacted vegetation are either displaced downward or flushed beyond the core depth under land with historical or ongoing irrigated agriculture. There are significant implications for the sustainability of groundwater resources in this system based upon the trends in groundwater NO3- concentrations, vadose zone core data, and results of the net infiltration models: 1) there may be more recharge to the basins than previously estimated and 2) there is a potential long-term concern for water quality. Due to the thick unsaturated zone in much of the system, long travel times are expected between the base of the root zone and the water table. It is unclear if the flux of NO3- and Cl- to the groundwater has peaked or if effects from the alteration of the natural vegetation regime will continue for years to come.

Robertson, W. M.; Sharp, J. M.

2013-12-01

97

Ground-Water Recharge in the Arid and Semiarid Southwestern United States  

USGS Publications Warehouse

Ground-water recharge in the arid and semiarid southwestern United States results from the complex interplay of climate, geology, and vegetation across widely ranging spatial and temporal scales. Present-day recharge tends to be narrowly focused in time and space. Widespread water-table declines accompanied agricultural development during the twentieth century, demonstrating that sustainable ground-water supplies are not guaranteed when part of the extracted resource represents paleorecharge. Climatic controls on ground-water recharge range from seasonal cycles of summer monsoonal and winter frontal storms to multimillennial cycles of glacial and interglacial periods. Precipitation patterns reflect global-scale interactions among the oceans, atmosphere, and continents. Large-scale climatic influences associated with El Ni?o and Pacific Decadal Oscillations strongly, but irregularly, control weather in the study area, so that year-to-year variations in precipitation and ground-water recharge are large and difficult to predict. Proxy data indicate geologically recent periods of naturally occurring multidecadal droughts unlike any in the modern instrumental record. Any anthropogenically induced climate change will likely reduce ground-water recharge through diminished snowpack at higher elevations. Future changes in El Ni?o and monsoonal patterns, both crucial to precipitation in the study area, are highly uncertain in current models. Current land-use modifications influence ground-water recharge through vegetation, irrigation, and impermeable area. High mountain ranges bounding the study area?the San Bernadino Mountains and Sierra Nevada to the west, and the Wasatch and southern Colorado Rocky Mountains to the east?provide external geologic controls on ground-water recharge. Internal geologic controls stem from tectonic processes that led to numerous, variably connected alluvial-filled basins, exposure of extensive Paleozoic aquifers in mountainous recharge areas, and distinct modes of recharge in the Colorado Plateau and Basin and Range subregions. The chapters in this professional paper present (first) an overview of climatic and hydrogeologic framework (chapter A), followed by a regional analysis of ground-water recharge across the entire study area (chapter B). These are followed by an overview of site-specific case studies representing different subareas of the geographically diverse arid and semiarid southwestern United States (chapter C); the case studies themselves follow in chapters D?K. The regional analysis includes detailed hydrologic modeling within the framework of a high-resolution geographic-information system (GIS). Results from the regional analysis are used to explore both the distribution of ground-water recharge for mean climatic conditions as well as the influence of two climatic patterns?the El Ni?o-Southern Oscillation and Pacific Decadal Oscillation?that impart a high degree of variability to the hydrologic cycle. Individual case studies employ a variety of geophysical and geochemical techniques to investigate recharge processes and relate the processes to local geologic and climatic conditions. All of the case studies made use of naturally occurring tracers to quantify recharge. Thermal and geophysical techniques that were developed in the course of the studies are presented in appendices. The quantification of ground-water recharge in arid settings is inherently difficult due to the generally low amount of recharge, its spatially and temporally spotty nature, and the absence of techniques for directly measuring fluxes entering the saturated zone from the unsaturated zone. Deep water tables in arid alluvial basins correspond to thick unsaturated zones that produce up to millennial time lags between changes in hydrologic conditions at the land surface and subsequent changes in recharge to underlying ground water. Recent advances in physical, chemical, isotopic, and modeling techniques have foster

Stonestrom, David A.; Constantz, Jim; Ferre, Ty P.A.; Leake, Stanley A.

2007-01-01

98

INFLUENCE OF SEDIMENT SUPPLY, LITHOLOGY, AND WOOD DEBRIS ON THE DISTRIBUTION OF BEDROCK AND ALLUVIAL CHANNELS  

EPA Science Inventory

Field surveys in the Willapa River basin, Washington State, indicate that the drainage area?channel slope threshold describing the distribution of bedrock and alluvial channels is influenced by the underlying lithology and that local variations in sediment supply can overwhelm ba...

99

Arid Climate Landscape Evolution and the Pediment Problem  

NASA Astrophysics Data System (ADS)

Although widely disseminated throughout many different climatic environments, pediments, or gently sloping, laterally extensive surfaces characterized by a thin veneer of alluvium covering bedrock, are particularly well developed in granitic desert locales such as the Mojave and Colorado Deserts in southern California and the Sonoran Desert in western Arizona. These features form a transitional zone within the piedmont of many exposed batholithic mountainous bodies, separating a zone of bare bedrock erosion in the steep mountain mass from a depositional zone in the alluvial basin. Well developed pediments in granitic environments commonly contain bedrock outcroppings (tors or inselbergs) that may remain uncovered indefinitely and sharp slope discontinuities at the piedmont junction separating the pediment surface from the mountain mass. Pediments have been the focus of debate in geomorphic circles for over half a century. While some geomorphologists have proposed that pediments and their associated tor fields represent unearthed relict landforms, others propose unique modes of sediment transport that form and maintain the beveled form of pediment surfaces. We hypothesize that a simple relationship between bedrock weathering and alluvial thickness could explain this range of enigmatic features and phenomena, a relationship that Anderson (2002) incorporates in his proposed explanation for high alpine surfaces and tors. Field observations suggest that the transformation of bedrock to regolith is most rapid with a finite covering of regolith. This weathering rule, combined with a simple set of sediment transport rules provides a mechanism through which pediment surfaces are produced. We examine the development of pediment surfaces and associated features using a 3D numerical, distributed-parameter landscape evolution model incorporating the most pertinent landscape development processes acting in arid regions. Temporally and spatially variable rainfall (storm size, duration, and coverage), soil types, and rock types can be accommodated. A linear diffusive transport mechanism redistributes sediment downslope, parameterizing the aggregated effects of tree throw (Yucca brevifolia), rodent burrowing, rain splash, and soil creep. Sediment flux due to stream flow is nonlinear in water flux, and is modulated by storm averaged infiltration capacity, which is dependent on soil type, depth, and antecedent soil moisture conditions.

Strudley, M. W.; Murray, A. B.; Haff, P. K.

2003-12-01

100

Geochemical evolution of groundwater salinity at basin scale: a case study from Datong basin, Northern China.  

PubMed

A hydrogeochemical investigation using integrated methods of stable isotopes ((18)O, (2)H), (87)Sr/(86)Sr ratios, Cl/Br ratios, chloride-mass balance, mass balance and hydrogeochemical modeling was conducted to interpret the geochemical evolution of groundwater salinity in Datong basin, northern China. The ?(2)H, ?(18)O ratios in precipitation exhibited a local meteoric water line of ?(2)H = 6.4 ?(18)O -5 (R(2) = 0.94), while those in groundwater suggested their meteoric origin in a historically colder climatic regime with a speculated recharge rate of less than 20.5 mm overall per year, in addition to recharge from a component of deep residual ancient lake water enriched with Br. According to the Sr isotope binary mixing model, the mixing of recharges from the Shentou karst springs (24%), the western margins (11%) and the eastern margins (65%) accounts for the groundwater from the deep aquifers of the down-gradient parts in the central basin is a possible mixing mechanism. In Datong, hydrolysis of silicate minerals is the most important hydrogeochemical process responsible for groundwater chemistry, in addition to dissolution of carbonate and evaporites. In the recharge areas, silicate chemical weathering is typically at the bisiallitization stage, while that in the central basin is mostly at the monosiallitization stage with limited evidence of being in equilibrium with gibbsite. Na exchange with bound Ca, Mg prevails at basin scale, and intensifies with groundwater salinity, while Ca, Mg exchange with bound Na locally occurs in the east pluvial and alluvial plains. Although groundwater salinity increases with the progress of water-rock/sediment interactions along the flow path, as a result of carbonate solubility control and continuous evapotranspiration, Na-HCO3 and Na-Cl-SO4 types of water are usually characterized respectively in the deep and the shallow aquifers of an inland basin with a silicate terrain in an arid climatic regime. PMID:24737419

Wu, Ya; Wang, Yanxin

2014-05-01

101

The origin and geologic evolution of the East Continent Rift Basin  

SciTech Connect

The East Continent Rift Basin (ECRB) is a newly recognized, dominantly sedimentary-volcanic Proterozoic rift basin that apparently represents the southern extension of the Keweenawan Midcontinent Rift. The ECRB extends from central Michigan at least as far south as south-central Kentucky. The inferred age of the rift fill is approximately 1,000 Ma. Evidence supporting a rift origin for the ECRB includes: interbedding of continental flood basalts and felsic volcanics with siliciclastics; sedimentary fill consisting of distal, arid-climate alluvial fan sediments that lack metamorphic lithologies; close proximity and similar lithologic succession to the Keweenawan rift-fill rocks of the Michigan Basin; and inferred marginal block faulting of Granite-Rhyolite Province rocks near the western edge of the ECRB. ECRB evolution is interpreted as follows: (1) formation of Granite-Rhyolite Province rocks (1,500--1,340 Ma); (2) Keweenawan crustal extension and rifting with development of central mafic complexes, emplacement of volcanic rocks, and deposition of siliciclastic fill from eroded marginal Granite-Rhyolite Province tilted fault blocks (ca 1,000 Ma); (3) overthrusting of the Grenville allochthon and associated foreland thrusting and folding of the rift sequence rocks together with deposition of foreland basin sediments (975---890 Ma); (4) Late Proterozoic erosional removal of the foreland basin sediments and interpreted wrench faulting along the Grenville Front (post-975 to pre-570 Ma); and (5) tectonic inversion, with the ECRB area remaining relatively high during major cambrian subsidence in central Kentucky (590--510 Ma).

Drahovzal, J.A. (Univ. of Kentucky, Lexington, KY (United States). Kentucky Geological Survey)

1992-01-01

102

The morphology of alluvial rivers  

NASA Astrophysics Data System (ADS)

Alluvial rivers form their channel in the material they transport, producing a varied collection of bed shapes, from deep single-thread channels to wide and shallow braids. Laboratory flumes produce similar morphologies at the centimeter scale, while braided rivers can spread over a few kilometers, suggesting that the same basic phenomena express themselves across scales. We conjecture that the competition between gravity and diffusion, at the scale of a sediment grain, controls the morphology of alluvial rivers. The classical threshold theory, which neglects diffusion, explains the relationship between river width and discharge [1]. However, it is valid only when bedload transport vanishes. When the river transports sediments, gravity pulls the grains towards the center of the channel, precluding equilibrium within this theoretical framework [2]. Based on laboratory experiments, we suggest that each bedload grain follows a random walk in the transverse direction. Consequently, sediments diffuse towards the less active areas of the bed, thus counteracting gravity by continuously rebuilding the river's bank. As the sediment discharge increases, this balance requires a wider and narrower channel, until the river becomes unstable. [1] R.E. Glover and Q.L. Florey, Stable channel profiles, US Bur. Reclamation, Hydr., 325, 1951. [2] G. Parker, Self-formed straight rivers with equilibrium banks and mobile bed. Part 2. The gravel river, J. Fluid Mech., 89, 1, 1978.

Devauchelle, O.; Seizilles, G.; Lajeunesse, E.; Bak, M. T.; Marc, O.; Metivier, F.

2012-12-01

103

Avulsion processes at the terminus of low-gradient semi-arid fluvial systems: Lessons from the Río Colorado, Altiplano endorheic basin, Bolivia  

NASA Astrophysics Data System (ADS)

The Río Colorado dryland river system in the southeast of the endorheic Altiplano Basin (Bolivia) terminates on a very flat coastal plain at the edge of the Salar de Uyuni, the world's largest salt pan with an area of ca. 12,500 km2. Since the Pleistocene the basin has experienced several lake expansion and contraction cycles in response to wetter and drier climate periods, respectively. At present the basin is in a dry climate period which results in a lake level lowstand and progradation of fluvial systems such as the Río Colorado onto the former lake bottom. The present field study of the terminus of the Río Colorado shows that the river experiences a gradual downstream decrease of bankfull width and depth. This bankfull decrease is caused by the combined effects of: (1) extremely low gradient of the lake bottom and, hence, loss of flow energy, and (2) downstream transmission losses due to high evaporation potential and river water percolation through the channel floor. Peak water discharge in seasonal, short-duration rain periods causes massive overbank flooding and floodplain inundation. On satellite images the morphology of the river terminus has a divergent pattern and resembles a network of coeval sinuous distributary channels. However, field observations show that only one channel is active at low flow stage, and at high-flow stage an abandoned, partially infilled channel may be active as well. The active channel at its termination splits into narrow and shallow anastomosing streams before its demise on the lacustrine coastal plain. The rest of the channels which form the divergent network are older sediment-filled abandoned sinuous river courses with multiple random avulsion points. These channel deposits, together with extensive amalgamated crevasse-splay deposits, form an intricate network of fluvial sand deposits. Successive stages of progressively deeper crevasse-channel incision into the floodplain are the result of waning-stage return flow of floodwaters towards the main channel. This results in increased crevasse-channel width, depth and length, and redeposition of eroded lacustrine coastal-plain sediment at the junction of the crevasse channel with the present-day river. A sedimentary model is proposed in which deep river bank incision by return flow in crevasse-channels creates the preferential locus for river avulsion. In a Lowstand Systems Tract with little vertical accommodation increase, the recurring avulsed-river paths result in a thin but laterally extensive network of amalgamated channel-fill, point-bar, crevasse-channel and crevasse-splay deposits. The resulting sedimentary architecture could easily be mistaken as produced by a distributary system of simultaneously active fluvial channels.

Donselaar, M. E.; Cuevas Gozalo, M. C.; Moyano, S.

2013-01-01

104

Geomorphic Processes and Remote Sensing Signatures of Alluvial Fans in the Kun Lun Mountains, China  

NASA Technical Reports Server (NTRS)

The timing of alluvial deposition in arid and semiarid areas is tied to land-surface instability caused by regional climate changes. The distribution pattern of dated deposits provides maps of regional land-surface response to past climate change. Sensitivity to differences in surface roughness and composition makes remote sensing techniques useful for regional mapping of alluvial deposits. Radar images from the Spaceborne Radar Laboratory and visible wavelength images from the French SPOT satellite were used to determine remote sensing signatures of alluvial fan units for an area in the Kun Lun Mountains of northwestern China. These data were combined with field observations to compare surface processes and their effects on remote sensing signatures in northwestern China and the southwestern United States. Geomorphic processes affecting alluvial fans in the two areas include aeolian deposition, desert varnish, and fluvial dissection. However, salt weathering is a much more important process in the Kun Lun than in the southwestern United States. This slows the formation of desert varnish and prevents desert pavement from forming. Thus the Kun Lun signatures are characteristic of the dominance of salt weathering, while signatures from the southwestern United States are characteristic of the dominance of desert varnish and pavement processes. Remote sensing signatures are consistent enough in these two regions to be used for mapping fan units over large areas.

Farr, Tom G.; Chadwick, Oliver A.

1996-01-01

105

Use of TOPSAR digital elevation data to determine the 3-dimensional shape of an alluvial fan  

NASA Technical Reports Server (NTRS)

Landforms in arid regions record the interplay between tectonic forces and climate. Alluvial fans are a common landform in desert regions where the rate of uplift is greater than weathering or sedimentation. Changes in uplift rate or climatic conditions can lead to isolation of the currently forming fan surface through entrenchment and construction of another fan either further from the mountain front (decreased uplift or increased runoff) or closer to the mountain front (increased uplift or decreased runoff). Thus, many alluvial fans are made up of a mosaic of fan units of different age, some older than 1 million years. For this reason, determination of the stages of fan evolution can lead to a history of uplift and runoff. In an attempt to separate the effects of tectonic (uplift) and climatic (weathering, runoff, sedimentation) processes on the shapes of alluvial fan units, a modified conic equation developed by Troeh (1965) was fitted to TOPSAR digital topographic data for the Trail Canyon alluvial fan in Death Valley, California. This allows parameters for the apex position, slope, and radial curvature to be compared with unit age.

Farr, Tom G.

1995-01-01

106

Miocene to recent history of the western Altiplano in northern Chile revealed by lacustrine sediments of the Lauca basin (18°15' 18°40' S/69°30' 69°05'W)  

NASA Astrophysics Data System (ADS)

The intramontane Lauca Basin at the western margin of the northern Chilean Altiplano lies to the west of and is topographically isolated from the well-known Plio-Pleistocene lake system of fluvio-lacustrine origin that covers the Bolivian Altiplano from Lake Titicaca to the north for more than 800 km to the Salar de Uyuni in the south. The Lauca Basin is filled by a sequence of some 120 m of mainly upper Miocene to Pliocene elastic and volcaniclastic sediments of lacustrine and alluvial origin. Volcanic rocks, partly pyroelastic, provide useful marker horizons. In the first period (6 4 Ma) of its evolution, the ‘Lago Lauca’ was a shallow ephemeral lake. Evaporites indicate temporarily closed conditions. After 4 Ma the lake changed to a perennial water body surrounded by alluvial plains. In the late Pleistocene and Holocene (2-0 Ma) there was only marginal deposition of alluvial and glacial sediments. The basin formed as a half-graben or by pull-apart between 10 and 15 Ma (tectonic displacement of the basal ignimbrite sequence during the ‘Quechua Phase’) and 6.2 Ma (maximum K/Ar ages of biotites of tuff horizons in the deepest part of the basin). Apart from this early basin formation, there has been surprisingly little displacement during the past 6 Ma close to the Western Cordillera of the Altiplano. Also, climate indicators (pollen, evaporites, sedimentary facies) suggest that an arid climate has existed for the past 6 Ma on the Altiplano. Together, these pieces of evidence indicate the absence of large scale block-faulting, tilt and major uplift during the past 5 6 Ma in this area.

Kött, A.; Gaupp, R.; Wörner, G.

1995-12-01

107

Miocene to Recent history of the western Altiplano in northern Chile revealed by lacustrine sediments of the Lauca Basin (18°15'-18°40'S/69°30'-69°05'W)  

NASA Astrophysics Data System (ADS)

The intramontane Lauca Basin at the western margin of the northern Chilean Altiplano lies to the west of and is topographically isolated from the well-known Plio-Pleistocene lake system of fluvio-lacustrine origin that covers the Bolivian Altiplano from Lake Titicaca to the north for more than 800km to the Salar de Uyuni in the south. The Lauca Basin is filled by a sequence of some 120m of mainly upper Miocene to Pliocene clastic and volcaniclastic sediments of lacustrine and alluvial origin. Volcanic rocks, partly pyroclastic, provide useful marker horizons. In the first period (6-4Ma) of its evolution, the 'Lago Lauca' was a shallow ephemeral lake. Evaporites indicate temporarily closed conditions. After 4Ma the lake changed to a perennial water body surrounded by alluvial plains. In the late Pleistocene and Holocene (2-0Ma) there was only marginal deposition of alluvial and glacial sediments. The basin formed as a half-graben or by pull-apart between 10 and 15Ma (tectonic displacement of the basal ignimbrite sequence during the 'Quechua Phase') and 6.2Ma (maximum K/Ar ages of biotites of tuff horizons in the deepest part of the basin). Apart from this early basin formation, there has been surprisingly little displacement during the past 6Ma close to the Western Cordillera of the Altiplano. Also, climate indicators (pollen, evaporites, sedimentary facies) suggest that an arid climate has existed for the past 6Ma on the Altiplano. Together, these pieces of evidence indicate the absence of large scale block-faulting, tilt and major uplift during the past 5-6Ma in this area.

Kött, A.; Gaupp, R.; Wörner, G.

108

Geoenvironmental and structural studies for developing new water resources in arid and semi-arid regions using remote sensing and GIS  

NASA Astrophysics Data System (ADS)

Water crises are rising with increasing world population and decreasing of freshwater resources. This problem is magnified in the arid and semi-arid regions because surface water resources are very limited and highly unreliable and therefore groundwater is the primary source of water supply in these regions. This study presents an integrated approach for the identification of groundwater occurrences using remote sensing, geological, and geophysical data, and establishing sustainable paths to groundwater management. The Central Eastern Desert (CED) of Egypt was selected as a test site for this study because its climate is arid and there is an urgent need to identify potential areas for groundwater accumulations. Field investigations indicated that the CED has three types of aquifers; shallow alluvial (SA), and fracture zone (FZ) aquifers in the valley depressions, and deep aquifers in the sedimentary succession that range in age from Late Cretaceous to Recent in the marginal extensional sub-basins (ESB) along the Red Sea coast. I developed three models: (1) a Geographic Information System (GIS) model for groundwater potential in the SA and FZ shallow aquifers; (2) a kinematic model for the development of the ESB; and (3) a groundwater budget model for the ESB aquifers. The GIS model is based on the analysis of remote sensing data of the Phased Array L-band Synthetic Aperture Radar, the Landsat Enhanced Thematic Mapper Plus, and the Advanced Spaceborne Thermal Emission and Reflection Radiometer digital elevation model. The model was evaluated and proven successful against the existing shallow water wells, and by geophysical surveys using Ground Penetrating Radar and Geoelectric methods. The kinematic model indicated that the ESB were formed in the orthogonal rifting phase in the late Oligocene that is followed by oblique rifting phase during the early Miocene which resulted to the en-echelon pattern of the inland ESB and nucleation of the rift depression into segments separated by oblique-slip accommodation zones. The groundwater budget model shows that the ESB aquifers have considerable amounts of paleowater that can be purified and used for drinking. The renewable groundwater of SA and FZ aquifers can be used for herding, irrigation, and ore dressing in the mining zones.

Amer, Reda Mohammed

2011-12-01

109

Modern and ancient alluvial fan deposits  

SciTech Connect

Understanding the structure and depositional processes of alluvial fans (river outwash deposits) has a special interest for those involved with the exploration of petroleum and many minerals. This collection of facsimile reprints of significant and classical research papers sheds new light on the subject. This reference covers the stratigraphy, sedimentology, and depositional processes of modern and ancient alluvial fans. Geographical areas considered include Arctic Canada, the American Southwest, Australia, Wyoming, Norway, and Spain. It includes a state-of-the-art introduction by the editor along with commentaries on all the papers included, a master author citation index and a subject index, and a chronological listing of early studies of alluvial fans.

Nilsen, T.H.

1985-01-01

110

Geological and geochemical characteristics of sedimentary rocks in Kremna, basin (Serbia)  

NASA Astrophysics Data System (ADS)

Studying lacustrine sediments is important because of their potential economic value since they often bear coal, oil shales and non-metallic mineral raw materials. Besides this, lacustrine sediments offer valuable information on the climate conditions which existed during the sedimentation. In Serbia there are 14 lacustrine basins spanning in age from Oligocene to Lower Pliocene. The aim of this study was to examine Lower Miocene Kremna basin, located in southwest Serbia. Kremna basin is a small basin, covering 15km2, but sedimentologically very interesting. For the purpose of this study, 43 sediment samples were taken from a borehole at different depths, from surface to 343 m depth of the basin. The borehole ended in weathered serpentinite. Mineralogical composition of sediments was determined using thin-sections and X-ray diffraction analysis, contents of macro-and microelements and rare-earth elements were determined by ICP-ES and ICP-MS techniques. Also, elemental analysis was applied to determine the contents of carbon, sulphur and nitrogen and n-alkanes, isoprenoide aliphatic alkanes and bitumen were also determined using GC-MS technique. Mineralogical analyses proved presents of several lithological types in Kremna basin: clastic sediments, tuffs, tuffaceous sediments, marlstones, dolomites, magnezites, and coal of non-economic value. Occurrence of sirlezite and sepiolite was also determined. Furthermore, according to all obtained results two faciae were determined: alluvial-marginal lacustrine and intrabasinal. Alluvial-marginal facies originated from predominantly ultramafic rocks which underlie the basin. Magnezites and Mg-marls and Mg-dolomites are dominant sediments in this facies. These sediments formed under arid, slightly saline conditions. Intrabasinal facies is represented mostly with marls, Mg-marls and dolomitic limestones. These sediments were deposited under a more humid climate with increase in paleoproductivity. The uppermost sediments of Kremna basin are represented with marly dolomite. Due to the swallowing of the basin sediments became relatively rich in predominantly land plant material. Tuffs and tuffaceous sediments were determined in both faciae.

Perunovi?, Tamara; Jovan?i?evi?, Branimir; Br?eski, Ilija; Šajnovi?, Aleksandra; Stojanovi?, Ksenija; Simi?, Vlada; Kašanin-Grubin, Milica

2014-05-01

111

Facies architecture of basin-margin units in time and space: Lower to Middle Miocene Sivas Basin, Turkey  

NASA Astrophysics Data System (ADS)

The Miocene Sivas Basin is located within a collision zone, forming one of the largest basins in Central Turkey that developed unconformably on a foundered Paleozoic-Mesozoic basement and Eocene-Oligocene deposits. The time and space relationships of sedimentary environments and depositional evolution of Lower to Middle Miocene rocks exposed between Zara and Hafik towns is studied. A 4 km thick continuous section is subdivided into the Agilkaya and Egribucak Formations. Each formation shows an overall fining upward trend and contains three members. Although a complete section is present at the western part (near Hafik) of the basin, to the east the uppermost two members (near Zara) are absent. The lower members of both formations are composed of fluvial sheet-sandstone and red mudstone that migrate laterally on a flood basin within a semi-arid fan system. In the Agilkaya Formation that crops out near Zara, alluvial fans composed of red-pink volcanic pebbles are also present. The middle members are composed of bedded to massive gypsum and red-green mudstone of a coastal and/or continental sabkha environment. While the massive gypsum beds reach several 10’s of m in Hafik area, near Zara, they are only few m thick and alternate with green mudstones. In Hafik, bedded gypsums are intercalated with lagoonal dolomitic limestone and bituminous shale in the Agilkaya Formation and with fluvial red-pink sandstone-red mudstone in the Egribucak Formation. The upper members are made up of fossiliferous mudstone and discontinuous sandy limestone beds with gutter casts, HCS, and 3-D ripples. They indicate storm-induced sedimentation in a shallow marine setting. The disorganized accumulations of ostreid and cerithiid shells, interpreted as coquina bars, are the products of storm generated reworking processes in brackish environments. Rapid vertical and horizontal facies changes and the facies associations in both formations reflect the locally subsiding nature of this molassic basin.

Çiner, A.; Kosun, E.

2003-04-01

112

Responses of Riparian Cottonwoods to Alluvial Water Table Declines.  

PubMed

/ Human demands for surface and shallow alluvial groundwater have contributed to the loss, fragmentation, and simplification of riparian ecosystems. Populus species typically dominate riparian ecosystems throughout arid and semiarid regions of North American and efforts to minimize loss of riparian Populus requires an integrated understanding of the role of surface and groundwater dynamics in the establishment of new, and maintenance of existing, stands. In a controlled, whole-stand field experiment, we quantified responses of Populus morphology, growth, and mortality to water stress resulting from sustained water table decline following in-channel sand mining along an ephemeral sandbed stream in eastern Colorado, USA. We measured live crown volume, radial stem growth, annual branch increment, and mortality of 689 live Populus deltoides subsp. monilifera stems over four years in conjunction with localized water table declines. Measurements began one year prior to mining and included trees in both affected and unaffected areas. Populus demonstrated a threshold response to water table declines in medium alluvial sands; sustained declines >/=1 m produced leaf desiccation and branch dieback within three weeks and significant declines in live crown volume, stem growth, and 88% mortality over a three-year period. Declines in live crown volume proved to be a significant leading indicator of mortality in the following year. A logistic regression of tree survival probability against the prior year's live crown volume was significant (-2 log likelihood = 270, chi2 with 1 df = 232, P < 0.0001) and trees with absolute declines in live crown volume of >/=30 during one year had survival probabilities <0.5 in the following year. In contrast, more gradual water table declines of thick similar0.5 m had no measurable effect on mortality, stem growth, or live crown volume and produced significant declines only in annual branch growth increments. Developing quantitative information on the timing and extent of morphological responses and mortality of Populus to the rate, depth, and duration of water table declines can assist in the design of management prescriptions to minimize impacts of alluvial groundwater depletion on existing riparian Populus forests. PMID:9950697

SCOTT; SHAFROTH; AUBLE

1999-04-01

113

Responses of Riparian Cottonwoods to Alluvial Water Table Declines  

NASA Astrophysics Data System (ADS)

Human demands for surface and shallow alluvial groundwater have contributed to the loss, fragmentation, and simplification of riparian ecosystems. Populus species typically dominate riparian ecosystems throughout arid and semiarid regions of North American and efforts to minimize loss of riparian Populus requires an integrated understanding of the role of surface and groundwater dynamics in the establishment of new, and maintenance of existing, stands. In a controlled, whole-stand field experiment, we quantified responses of Populus morphology, growth, and mortality to water stress resulting from sustained water table decline following in-channel sand mining along an ephemeral sandbed stream in eastern Colorado, USA. We measured live crown volume, radial stem growth, annual branch increment, and mortality of 689 live Populus deltoides subsp. monilifera stems over four years in conjunction with localized water table declines. Measurements began one year prior to mining and included trees in both affected and unaffected areas. Populus demonstrated a threshold response to water table declines in medium alluvial sands; sustained declines ?1 m produced leaf desiccation and branch dieback within three weeks and significant declines in live crown volume, stem growth, and 88% mortality over a three-year period. Declines in live crown volume proved to be a significant leading indicator of mortality in the following year. A logistic regression of tree survival probability against the prior year's live crown volume was significant (-2 log likelihood = 270, ?2 with 1 df = 232, P < 0.0001) and trees with absolute declines in live crown volume of ?30 during one year had survival probabilities <0.5 in the following year. In contrast, more gradual water table declines of ~0.5 m had no measurable effect on mortality, stem growth, or live crown volume and produced significant declines only in annual branch growth increments. Developing quantitative information on the timing and extent of morphological responses and mortality of Populus to the rate, depth, and duration of water table declines can assist in the design of management prescriptions to minimize impacts of alluvial groundwater depletion on existing riparian Populus forests.

Scott, Michael L.; Shafroth, Patrick B.; Auble, Gregor T.

1999-04-01

114

Geometry and evolution of a syntectonic alluvial fan, Southern Pyrenees  

SciTech Connect

Syntectonic alluvial fans formed on the northern margin of the Ebro Foreland Basin along the South Pyrenean thrust front during late orogenic thrust movements in the late Oligocene/early Miocene. The present-day geometry, structural relations and sedimentology of one of these fans, the Aguero fan in the province of Huesca, Spain, were studied. Field observations of the architecture of depositional facies and the geometries of syn-tectonic folds and unconformities indicate that the Aguero fan formed as the result of several phases of sedimentation which were primarily controlled by periods of tectonic activity and quiescence. The syntectonic unconformities and growth folds in the fan deposits provide a detailed record of the evolution of a fan adjacent to an active thrust front. Using a computer program to simulate sedimentation and deformation of an alluvial fan it is possible to constrain rates of both sedimentary and tectonic processes by modeling the evolution of the fan body. A facies model for the fan phases indicates that the facies change from proximal (coarse-grained, amalgamated) to distal (finger grained, stacked fining up cycles) in less than 1 km across a fan of radius estimated to be about 2 km.

Arminio, J.F. (Maraven S.A., Caracas (Venezuela)); Nichols, G.J. (Univ. of London, Egham, Surrey (United Kingdom))

1993-02-01

115

Investigation of groundwater response to overland flow and topography using a coupled MIKE SHE\\/MIKE 11 modeling system for an arid watershed  

Microsoft Academic Search

The distribution of groundwater and dynamic fluctuations in groundwater levels have direct impacts on the eco-environment of arid areas. Investigations of groundwater recharge in arid areas are typically limited by a lack of adequate meteorological and hydrogeological records. This study focuses on groundwater recharge in a seasonally flooded arid area within the Tarim Basin, China, with the aim of analyzing

Hai-Long Liu; Xi Chen; An-Ming Bao; Ling Wang

2007-01-01

116

Geomorphological evidence of neotectonic deformation in the Carnarvon Basin, Western Australia  

NASA Astrophysics Data System (ADS)

This study examines channel-scale morphodynamics of ephemeral streams in the onshore Carnarvon basin in arid west-central Western Australia. The rivers in this region have low gradients, the landscape has low relief, and the rates of climatically and tectonically driven geomorphic processes also are low. As a result, the rivers in the Carnarvon alluvial plain are highly sensitive to minor perturbations in base level, channel slope, and fluvial energy. We use channel planform adjustments, stream gradient changes, and floodplain profiles across multiple ephemeral streams within a variety of catchments and flow regimes to determine if tectonically driven land level changes are affecting channel form and fluvial processes. Growth of individual fold segments is shown to have altered stream and floodplain gradients and triggered repeated avulsions at structurally controlled nodes. Aligned perturbations in channel form across multiple channel-fold intersections provide systematic geomorphic evidence for the location and orientation of neotectonic structures in the region. These features occur as a belt of low relief anticlines in the Carnarvon alluvial plain.

Whitney, Beau B.; Hengesh, James V.

2015-01-01

117

Impacts of hydroelectric dams on alluvial riparian plant communities in Eastern Brazilian Amazonian.  

PubMed

The major rivers of the Amazon River basin and their biota are threatened by the planned construction of large hydroelectric dams that are expected to have strong impacts on floodplain plant communities. The present study presents forest inventories from three floodplain sites colonized by alluvial riparian vegetation in the Tapajós, Xingu and Tocantins River basins in eastern Amazonian. Results indicate that tree species of the highly specialized alluvial riparian vegetation are clearly distinct among the three river basins, although they are not very distinct from each other and environmental constraints are very similar. With only 6 of 74 species occurring in all three inventories, most tree and shrub species are restricted to only one of the rivers, indicating a high degree of local distribution. Different species occupy similar environmental niches, making these fragile riparian formations highly valuable. Conservation plans must consider species complementarily when decisions are made on where to place floodplain forest conservation units to avoid the irreversible loss of unique alluvial riparian vegetation biodiversity. PMID:24068089

Ferreira, Leandro Valle; Cunha, Denise A; Chaves, Priscilla P; Matos, Darley C L; Parolin, Pia

2013-09-01

118

Strontium Isotope Ratios (87Sr\\/86Sr) as Tracers for Recharge Areas, Groundwater Movement and Mixing in an Arid Coastal Region of the Sultanate of Oman  

Microsoft Academic Search

In arid and semi-arid regions, conventional hydrological investigations often fail to adequately describe groundwater systems due to a large spatial and temporal variability of hydrological parameters. Alternatively, this study from northern Oman utilizes strontium isotope ratios (87Sr\\/86Sr) to describe the origin and evolution of groundwater in the Batinah coastal alluvial aquifer, which supplies water for the most densely populated, cultivated

C. E. Weyhenmeyer; H. N. Waber; J. Kramers; S. J. Burns; A. Matter

2001-01-01

119

The Alluvial Archaeology Of North-West Europe And The Mediterranean  

E-print Network

This paper takes a retrospective and prospective view of European alluvial archaeology with special reference to developments in Britain over the past 10 years. In this respect, the January 1991 "Archaeology under alluvium: archaeology and the river environment in Britain" conference and published proceedings (Needham and Macklin, 1992), provides a very useful benchmark. It constituted the first joint meeting between archaeologist and geomorphologists in the UK which had as its theme human-environment interactions in river basins and was a significant departure from previous conferences because its focus was primarily non-tidal river systems and Holocene environmental change. Seven major topics emerged from this meeting and they form a useful framework for reviewing progress over the 1990s and for mapping future research, conservation and management agendas. These were: 1. the contrasts between alluvial archaeology in rural and urban environments; 2. the roles and relative importance of human activity and climate change in river erosion and alluviation; 3. new techniques for dating Holocene alluvial sequences; 4. Holocene and historic channel and floodplain metamorphosis; 5. the use of physical and chemical fingerprinting techniques in provenancing alluvial sediments; 6. palaeoflood analysis and the affect of extreme events on river behaviour and the archaeological record; 7. evaluating and predicting archaeological survival and potential of river valleys. Each of these topics will be reviewed and suggestions given to ways of addressing some of the critical gaps in our knowledge base, particularly using new research tools (e.g. computer modelling, LIDAR, GIS) that are now available to the alluvial archaeological community. Building on the success of the CADW-,English He...

S Of Conference; Dr. A J Howard; Prof M G Macklin; Dr. D G Passmore; Wine Reception; Buckinghamshire England

120

Extremely arid soils of the Ili Depression in Kazakhstan  

NASA Astrophysics Data System (ADS)

On the basis of macro- and micromorphological and analytical studies of extremely arid soils of the Ili Depression in Kazakhstan, a comparative analysis of pedogenetic processes shaping these soils on piedmont plains of different ages and heights is performed. The types of soil horizons and their combinations are analyzed in the context opf modern Russian and international soil classification systems. The genesis of extremely arid soils is controlled by the climatic conditions and by their geomorphic position on alluvial fans of piedmont plains. The following processes are diagnosed in these soils: soil crusting with vesicular porosity, the development of desert pavements with rock varnish, rubification, surface salinization, and iron depletion around the pores. It is suggested that the initial factor-based name (extremely arid) of these soils can be replaced by the name vesicular-crusty soils with the corresponding AKL diagnostic horizon, which is more consistent with the principles of substantive-genetic classification systems. In order to determine the classification position of these soils in terms of the new Russian soil classification system, new diagnostic horizons—AKL and CS—have to be introduced in this system. According to the WRB classification, the studied soils belong to the group of Gypsisols; the soil with strong salinization fits the criteria of the group of Solonchaks. A qualifier [yermic] is to be added to reflect the development of desert pavement and vesicular layer under extreme arid conditions.

Lebedeva, M. P.; Gerasimova, M. I.; Golovanov, D. L.; Yamnova, I. A.

2015-01-01

121

Riparian ecosytems of semi-arid North America: Diversity and human impacts  

Microsoft Academic Search

Riparian ecosystems in the semi-arid West of North America are diverse but have many similarities. The mountainous landscape\\u000a with wide range of latitude, longitude, and elevation offers diverse opportunities for streamside vegetation. All riparian\\u000a ecosystems in the region are dependent on supplemental water, usually from the shallow, valley alluvial aquifer. Western riparian\\u000a ecosystems provide several ecological services. They stabilize streambanks,

Duncan T. Patten

1998-01-01

122

Sediments in Semi-arid Wetlands: US Southern High Plains  

Technology Transfer Automated Retrieval System (TEKTRAN)

Playas are ephemeral wetlands on the semi-arid U.S. Southern High Plains that serve as runoff catchment basins and are thought to be focal points of Ogallala aquifer recharge. Sediments in playas alter biodiversity and hydroperiods. The purpose of this study was to evaluate the effects of outerbas...

123

Alluvial Fan, Rocky Mountain National Park  

USGS Multimedia Gallery

The Alluvial Fan is a fan-shaped area of disturbance in Rocky Mountain National Park. It was created on July 15, 1982, when the earthen Lawn Lake Dam above the area gave way, flooding the Park and nearby town of Estes Park with more than 200 million gallons of water. Enormous boulders were displaced...

124

Arsenate adsorption by unsaturated alluvial sediments  

Technology Transfer Automated Retrieval System (TEKTRAN)

Arsenate adsorption as a function of solution arsenic concentration and solution pH was investigated on five alluvial sediments from the Antelope Valley, Western Mojave Desert, California. Arsenate adsorption increased with increasing solution pH, exhibited a maximum around pH 4 to 5, and then decr...

125

Geospatial Data to Support Analysis of Water-Quality Conditions in Basin-Fill Aquifers in the Southwestern United States  

USGS Publications Warehouse

The Southwest Principal Aquifers study area consists of most of California and Nevada and parts of Utah, Arizona, New Mexico, and Colorado; it is about 409,000 square miles. The Basin-fill aquifers extend through about 201,000 square miles of the study area and are the primary source of water for cities and agricultural communities in basins in the arid and semiarid southwestern United States (Southwest). The demand on limited ground-water resources in areas in the southwestern United States has increased significantly. This increased demand underscores the importance of understanding factors that affect the water quality in basin-fill aquifers in the region, which are being studied through the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) program. As a part of this study, spatial datasets of natural and anthropogenic factors that may affect ground-water quality of the basin-fill aquifers in the southwestern United States were developed. These data include physical characteristics of the region, such as geology, elevation, and precipitation, as well as anthropogenic factors, including population, land use, and water use. Spatial statistics for the alluvial basins in the Southwest have been calculated using the datasets. This information provides a foundation for the development of conceptual and statistical models that relate natural and anthropogenic factors to ground-water quality across the Southwest. A geographic information system (GIS) was used to determine and illustrate the spatial distribution of these basin-fill variables across the region. One hundred-meter resolution raster data layers that represent the spatial characteristics of the basins' boundaries, drainage areas, population densities, land use, and water use were developed for the entire Southwest.

McKinney, Tim S.; Anning, David W.

2009-01-01

126

Soil Carbonate Dynamics on Arid Cropland in North China  

NASA Astrophysics Data System (ADS)

Pedogenic carbonate (PIC) is an important element for carbon sequestration. However, field data necessary to quantify carbon sequestration as carbonate have been lacking. Here, we report recent studies of carbonate accumulation in soils of the arid and semi-arid regions of north China. First study was carried out in southern Xinjiang, the Yanqi Basin, where more than 100 soil samples were collected from desert land, shrub land and cropland, and soil organic carbon (SOC) and inorganic carbon (SIC) and their stable 13C compositions were determined. This study showed that both SOC and SIC stocks were significantly higher on the cropland than on the desert land and shrub land. Our analyses suggested that cropping might have led to large PIC accumulation (24-116 g C m-2 year-1) in the Yanqi Basin. Second study was to evaluate carbon sequestration on cropland using archived soil samples from three long-term experiment (LTE) sites in north China: Urumqi, Yangling and Zhengzhou. SOC and SIC, and their stable 13C compositions were determined in two sets of soil samples (130 samples in total) collected in the early and late 2000's under various fertilization treatments. Our study showed an overall increase of SIC content in soil profiles over time, particularly under fertilizations. Accumulation rate of SIC stock over the 0-100 cm ranged from ~100 to 200 g C m-2 year-1, with the greatest rate found under the highest fertilization rate. Our analyses indicated that fertilization might have led to an average accumulation rate of > 60 g C m-2 year-1 for PIC on these arid croplands. Our studies showed that more carbon sequestrated in the form of carbonate than as SOC on arid and semi-arid lands, and suggests that increasing SOC stock through straw incorporation and manure application in the arid and semi-arid regions would also enhance carbonate accumulation in soil profiles over long-term.

Wang, X.; Xu, M.; Wang, J.; Zhang, W.; Yang, X.; Huang, S.; Liu, H.

2013-12-01

127

Alluvial evidence for major climate and flow regime changes during the middle and late Quaternary in eastern central Australia  

NASA Astrophysics Data System (ADS)

As a low-gradient arid region spanning the tropics to the temperate zone, the Lake Eyre basin has undergone gentle late Cenozoic crustal warping leading to substantial alluvial deposition, thereby forming repositories of evidence for palaeoclimatic and palaeohydrological changes from the Late Tertiary to the Holocene. Auger holes and bank exposures at five locations along the lower 500 km of Cooper Creek, a major contributor to Lake Eyre in the eastern part of the basin, yielded 85 luminescence dates (TL and OSL) that, combined wit a further 142 luminescence dates from northeastern Australia, have established a chronology of multiple episodes of enhanced flow regime from about 750 ka to the Holocene. Mean bankfull discharges on Cooper Creek upstream of the Innamincka Dome at 250-230 ka or oxygen isotope stages (OIS) 7-6 are estimated to have been 5 to 7 times larger than those of today, however, substantially less reworking has occurred during and after OIS 5 than before. Lower Cooper Creek appears to have similarly declined. In the Tirari Desert adjacent to Lake Eyre there is evidence of widespread alluvial activity, perhaps during but certainly before the Middle Pleistocene, yet the river became laterally restricted in OIS 7 to 5. While the Quaternary has been characterised by a dramatically oscillating wet-dry climate, since oxygen isotope stage OIS 7 or 6 there has been a general decline in the magnitude of the episodes of wetness to which the eastern part of central Australia has periodically returned. During the last full glacial cycle, Cooper Creek's periods of greatest runoff and sand transport were not during the last interglacial maximum of OIS 5e (132-122 ka) but later in OIS 5 when sea levels and global temperatures were substantially below those of 5e or today. Fluvial activity returned in OIS 4 and 3, but not to the extent of mid and late OIS 5; strongly seasonal but still powerful flows transported sand and fed source-bordering dunes in OIS 5 and 3. This chronology of fluvial activity in the late Quaternary broadly coincides with that for rivers of southeastern Australia and suggests that the wet phases in eastern central Australia have not been governed as much by the northern monsoon as by conditions in the western Pacific close to the east coast both north and south. Flow confinement within the Innamincka Dome has locally amplified Cooper Creek's energy, and here evidence exists for short but high-magnitude episodes of flow during the Last Glacial Maximum and in the early to middle Holocene, conditions that were capable of forming large palaeochannels but that were not long-lived enough to rework the river's extensive floodplains elsewhere along its length.

Nanson, Gerald C.; Price, David M.; Jones, Brian G.; Maroulis, Jerry C.; Coleman, Maria; Bowman, Hugo; Cohen, Timothy J.; Pietsch, Timothy J.; Larsen, Joshua R.

2008-10-01

128

UNESCO's G-WADI Program - Developing and Delivering Tools for Improved Water Management in Semi-arid and Arid Lands  

NASA Astrophysics Data System (ADS)

UNESCO's Water and Development Information for Arid Lands - A Global Network (G-WADI) aims to strengthen the capacity to manage the water resources of arid and semi-arid areas around the globe through a network of international and regional cooperation. Six centers, including SAHRA headquartered at the University of Arizona and CHRS at UC-Irvine, are cooperating to improve water resource management by sharing knowledge and tools. Specific objectives include: improved understanding of the special characteristics of hydrological systems and water management needs in arid areas, through shared data and experiences; capacity building of individuals and institutions; raising awareness of advanced technologies for data provision, data assimilation, and system analysis; and promoting integrated basin management and the use of appropriate decision support tools. SAHRA coordinates G-WADI's information dissemination via G-WADI's web site and publications. Web-based resources include Global Water News Watch and the subscription service, Water News Tracker, plus access to remotely sensed precipitation data from HyDIS. Information on use of isotopes and chemical tracers is also featured. Materials and outcomes from various workshops and short courses on modeling, water harvesting, and impacts of climate change also are provided. While the intent is to benefit water resource managers in semi- arid and arid developing countries, the collaboration among international water centers, and perspectives and traditional knowledge gained from users, has benefitted U.S. researchers in many ways.

Woodard, G. C.; Imam, B.; Sorooshian, S.

2007-12-01

129

Sedimentary facies and depositional environments of early Mesozoic Newark Supergroup basins, eastern North America  

USGS Publications Warehouse

The early Mesozoic Newark Supergroup consists of continental sedimentary rocks and basalt flows that occupy a NE-trending belt of elongate basins exposed in eastern North America. The basins were filled over a period of 30-40 m.y. spanning the Late Triassic to Early Jurassic, prior to the opening of the north Atlantic Ocean. The sedimentary rocks are here divided into four principal lithofacies. The alluvial-fan facies includes deposits dominated by: (1) debris flows; (2) shallow braided streams; (3) deeper braided streams (with trough crossbeds); or (4) intense bioturbation or hyperconcentrated flows (tabular, unstratified muddy sandstone). The fluvial facies include deposits of: (1) shallow, ephemeral braided streams; (2) deeper, flashflooding, braided streams (with poor sorting and crossbeds); (3) perennial braided rivers; (4) meandering rivers; (5) meandering streams (with high suspended loads); (6) overbank areas or local flood-plain lakes; or (7) local streams and/or colluvium. The lacustrine facies includes deposits of: (1) deep perennial lakes; (2) shallow perennial lakes; (3) shallow ephemeral lakes; (4) playa dry mudflats; (5) salt-encrusted saline mudflats; or (6) vegetated mudflats. The lake margin clastic facies includes deposits of: (1) birdfoot deltas; (2) stacked Gilbert-type deltas; (3) sheet deltas; (4) wave-reworked alluvial fans; or (5) wave-sorted sand sheets. Coal deposits are present in the lake margin clastic and the lacustrine facies of Carnian age (Late Triassic) only in basins of south-central Virginia and North and South Carolina. Eolian deposits are known only from the basins in Nova Scotia and Connecticut. Evaporites (and their pseudomorphs) occur mainly in the northern basins as deposits of saline soils and less commonly of saline lakes, and some evaporite and alkaline minerals present in the Mesozoic rocks may be a result of later diagenesis. These relationships suggest climatic variations across paleolatitudes, more humid to the south where coal beds are preserved, and more arid in the north where evaporites and eolian deposits are common. Fluctuations in paleoclimate that caused lake levels to rise and fall in hydrologically closed basins are preserved as lacustrine cycles of various scales, including major shifts in the Late Triassic from a wet Carnian to an arid Norian. In contrast, fluvial deposits were mainly formed in response to the tectonic evolution of the basins, but to some extent also reflect climatic changes. The Newark Supergroup illustrates the complexity of rift-basin sedimentation and the problems that may arise from using a single modern analog for sedimentary deposition spanning millions of years. It also shows that a tremendous wealth of depositional, climatic, and tectonic information is preserved in ancient rift-basin deposits which can be recovered if the depositional processes of modern rift-basin deposits are understood. ?? 1991.

Smoot, J.P.

1991-01-01

130

Fire, Holocene Climate Change, and Geomorphic Response Recorded in Alluvial Fan Sediments  

NASA Astrophysics Data System (ADS)

Alluvial fan stratigraphic sequences record fire history in charcoal-rich deposits and buried burned soil surfaces. Deposit characteristics provide information about the magnitude of fire-related sedimentation events and severity of associated fires, and radiocarbon-dating of charcoal establishes the timing of fires. Unlike lakes, alluvial fans are ubiquitous in mountain environments. Although alluvial-fan fire records lack the annual resolution of tree-ring records, compilation of data from many alluvial fan sites provides a statistical sample of fire timing and approximate severity that can be related to climate variations over centennial to millennial timescales. We examine alluvial fan records from xeric Pinus ponderosa-dominated forests of central Idaho, and compare them with similar records from cooler, high-elevation Pinus contorta-dominated forests of Yellowstone National Park. Identification of charcoal macrofossils from Idaho fan deposits limits inbuilt age errors in radiocarbon dating, and shows that similar forest compositions have existed over the last ca. 4000 years in the fan drainage basins. Limited data from ca. 4000-7000 yr ago suggest that Pinus ponderosa was either sparse or absent in the 4 basins represented. Large fire-related debris flows in both Idaho and Yellowstone indicate severe fires during the ca. 1050-750 cal yr BP Medieval Climatic Anomaly (MCA), which included widespread and severe western US droughts. Another such episode 2700-1600 cal yr BP is less prominent in the Idaho record. Numerous small, fire-induced sedimentation events in Idaho ca. 350-500 (Little Ice Age), 1200-1400, and 2800-3000 cal yr BP likely indicate frequent low- to mixed-severity fires, and coincide with indicators of generally cool, moist conditions in the western USA and North Atlantic, and with minimal fire activity in Yellowstone. We infer that these effectively wetter periods allow greater grass growth, fueling frequent surface fires in ponderosa forests, but limiting fires in general in the effectively wetter forests of Yellowstone. Maxima in dated small events may relate to significant droughts within these intervals, e.g. in the late AD 1500s, but widespread severe fires are not indicated. Alluvial-fan records add to data from other charcoal-based proxy records of fire that indicate the importance of centennial- to millennial-scale climate change in modulating fire activity and geomorphic response in conifer forests over the Holocene.

Pierce, J. L.; Meyer, G. A.

2004-12-01

131

The application of remotely sensed data to pedologic and geomorphic mapping on alluvial fan and playa surfaces in Saline Valley, California  

NASA Technical Reports Server (NTRS)

Arid and semiarid regions yield excellent opportunities for the study of pedologic and geomorphic processes. The dominance of rock and soil exposure over vegetation not only provides the ground observer with observational possibilities but also affords good opportunities for measurement by aircraft and satellite remote sensor devices. Previous studies conducted in the area of pedologic and geomorphic mapping in arid regions with remotely sensed data have utilized information obtained in the visible to near-infrared portion of the spectrum. Thermal Infrared Multispectral Scanner (TIMS) and Thematic Mapping (TM) data collected in 1984 are being used in comjunction with maps compiled during a Bureau of Land Management (BLM) soil survey to aid in a detailed mapping of alluvial fan and playa surfaces within the valley. The results from this study may yield valuable information concerning the application of thermal data and thermal/visible data combinations to the problem of dating pedologic and geomorphic features in arid regions.

Miller, D. A.; Petersen, G. W.; Kahle, A. B.

1986-01-01

132

Downstream effects of dams on alluvial rivers  

Microsoft Academic Search

This study describes changes in mean channel-bed elevation, channel width, bed-material sizes, vegetation, water discharges, and sediment loads downstream from 21 dams constructed on alluvial rivers. Most of the studied channels are in the semiarid western US. Flood peaks generally were decreased by the dams, but in other respects the post-dam water-discharge characteristics varied from river to river. Sediment concentrations

G. P. Williams; M. G. Wolman

1985-01-01

133

Interaction of fine sediment with alluvial streambeds  

USGS Publications Warehouse

An alluvial streambed can have a large capacity to store fine sediments that are extracted from the flow when instream concentrations are high and it can gradually release fine sediment to the flow when the instream concentrations are low. Several types of storage mechanisms are available depending on the relative size distribution of the suspended load and bed material, as well as the flow hydraulics. -from Authors

Jobson, H.E.; Carey, W.P.

1989-01-01

134

Generalized sorting profile of alluvial fans  

NASA Astrophysics Data System (ADS)

Alluvial rivers often exhibit self-similar gravel size distributions and abrupt gravel-sand transitions. Experiments suggest that these sorting patterns are established rapidly, but how—and how fast—this convergence occurs in the field is unknown. We examine the establishment of downstream sorting patterns in a kilometer-scale alluvial fan. The sharp transition from canyon to unconfined, channelized fan provides a well-defined boundary condition. The channel changes from deep and entrenched at the fan apex to shallow and depositional over a short distance, exhibiting nonequilibrium behavior. The resulting gravel-fining profile is not self-similar; the particle size distribution narrows until approximate equal mobility is achieved. Downfan, the gravel-sand transition appears to exhibit a self-similar form; field and laboratory data collapse when downstream distance is normalized by the location of the transition. Results suggest a generalized sorting profile for alluvial fans as a consequence of the threshold of motion and nonequilibrium channels.

Miller, Kimberly Litwin; Reitz, Meredith D.; Jerolmack, Douglas J.

2014-10-01

135

Origin and recharge rates of alluvial ground waters, Eastern Desert, Egypt.  

SciTech Connect

Stable isotope and tritium analyses of shallow ground waters in the Eastern Desert of Egypt showed that the waters were derived largely by evaporation of regional precipitation and at least partly from precipitation in the past 45 y. To estimate the ground water recharge rate, we developed an integrated hydrologic model based on satellite data, geologic maps, infiltration parameters, and spatial rainfall distribution. Modeling indicated that during a severe 1994 storm, recharge through transmission loss in Wadi El-Tarfa was 21% of the precipitation volume. From archival precipitation data, we estimate that the annual recharge rate for the El-Tarfa alluvial aquifer is 4.7 x 10{sup 6} m{sup 3}. Implications for the use of renewable ground waters in arid areas of Egypt and in neighboring countries are clear.

Sultan, M.; Gheith, H.; Sturchio, N. C.; El Alfy, Z.; Danishwar, S.

2002-04-12

136

Appraisal of nuclear waste isolation in the vadose zone in arid and semiarid regions (with emphasis on the Nevada Test Site)  

SciTech Connect

An appraisal was made of the concept of isolating high-level radioactive waste in the vadose zone of alluvial-filled valleys and tuffaceous rocks of the Basin and Range geomorphic province. Principal attributes of these terranes are: (1) low population density, (2) low moisture influx, (3) a deep water table, (4) the presence of sorptive rocks, and (5) relative ease of construction. Concerns about heat effects of waste on unsaturated rocks of relatively low thermal conductivity are considered. Calculations show that a standard 2000-acre repository with a thermal loading of 40 kW/acre in partially saturated alluvium or tuff would experience an average temperature rise of less than 100{sup 0}C above the initial temperature. The actual maximum temperature would depend strongly on the emplacement geometry. Concerns about seismicity, volcanism, and future climatic change are also mitigated. The conclusion reached in this appraisal is that unsaturated zones in alluvium and tuff of arid regions should be investigated as comprehensively as other geologic settings considered to be potential repository sites.

Wollenberg, H.A.; Wang, J.S.Y.; Korbin, G.

1983-05-01

137

The volcano-sedimentary evolution of a post-Variscan intramontane basin in the Swiss Alps (Glarus Verrucano) as revealed by zircon U-Pb age dating and Hf isotope geochemistry  

NASA Astrophysics Data System (ADS)

The Late Palaeozoic Glarus Verrucano basin (GVB, Glarus Alps, eastern Switzerland) formed as an intramontane graben in the aftermath of the Variscan orogeny. Its fill, the Glarus Verrucano, consists of immature alluvial fan and playa lake deposits with intercalated bimodal volcanics (basalts and rhyolites). Despite its importance for local and regional geology, no modern sedimentologic or stratigraphic studies on the GVB exist. By means of sedimentologic and geochronologic studies, we reconstruct the volcano-sedimentary evolution of the GVB: it developed at the Carboniferous/Permian boundary and experienced a first (bimodal) volcanic phase around 285 Ma. For the same time, indications for temporarily humid climate in the otherwise rather arid Early Permian are demonstrated (e.g. pyrite-bearing sandstones). During the Middle and Early Late Permian, increasing aridity is indicated by playa deposits, fanglomerates and subaerial ignimbrites, which mark a second (silicic) volcanic phase at 268 Ma. The detrital zircon age spectra are dominated by Late Variscan ages and thus demonstrate that older sedimentary and metamorphic rocks once forming the Variscan nappe edifice were already mostly eroded at that time. Finally, some larger-scale speculations are given which could indicate a causal connection between the widespread tectono-magmatic Mid-Permian Episode and the local development of the Glarus Verrucano basin.

Letsch, Dominik; Winkler, Wilfried; von Quadt, Albrecht; Gallhofer, Daniela

2015-01-01

138

The volcano-sedimentary evolution of a post-Variscan intramontane basin in the Swiss Alps (Glarus Verrucano) as revealed by zircon U-Pb age dating and Hf isotope geochemistry  

NASA Astrophysics Data System (ADS)

The Late Palaeozoic Glarus Verrucano basin (GVB, Glarus Alps, eastern Switzerland) formed as an intramontane graben in the aftermath of the Variscan orogeny. Its fill, the Glarus Verrucano, consists of immature alluvial fan and playa lake deposits with intercalated bimodal volcanics (basalts and rhyolites). Despite its importance for local and regional geology, no modern sedimentologic or stratigraphic studies on the GVB exist. By means of sedimentologic and geochronologic studies, we reconstruct the volcano-sedimentary evolution of the GVB: it developed at the Carboniferous/Permian boundary and experienced a first (bimodal) volcanic phase around 285 Ma. For the same time, indications for temporarily humid climate in the otherwise rather arid Early Permian are demonstrated (e.g. pyrite-bearing sandstones). During the Middle and Early Late Permian, increasing aridity is indicated by playa deposits, fanglomerates and subaerial ignimbrites, which mark a second (silicic) volcanic phase at 268 Ma. The detrital zircon age spectra are dominated by Late Variscan ages and thus demonstrate that older sedimentary and metamorphic rocks once forming the Variscan nappe edifice were already mostly eroded at that time. Finally, some larger-scale speculations are given which could indicate a causal connection between the widespread tectono-magmatic Mid-Permian Episode and the local development of the Glarus Verrucano basin.

Letsch, Dominik; Winkler, Wilfried; von Quadt, Albrecht; Gallhofer, Daniela

2014-07-01

139

Joint clay-heavy-light mineral analysis: a tool to investigate the hydrographic-hydraulic regime of Late Cenozoic deltaic inland fans under changing climatic conditions (Cuvelai-Etosha Basin, Namibia)  

NASA Astrophysics Data System (ADS)

An interdisciplinary study (major and minor elements, C and O isotopes, heavy and light minerals, phyllosilicates, wireline logs) in northern Namibia unraveled the hydrographic and hydraulic evolution of alluvial-fluvial sediments of the Kunene and Cubango megafans (Etosha-Cuvelai Basin). Three principal aquatic regimes were operative within the megafan complex: (1) the hydrographic regime, (2) the proximal hydraulic regime, (3) the distal hydraulic regime. The allogenic mineral assemblages mirror the hydrographic variation or drainage system and the lithological evolution of the fan sediments (alluvial-fluvial fan, lacustrine environment with evaporites, fan delta progradation). Authigenic heavy minerals are markers of the physical-chemical condition (Eh and pH values) of the hydraulic regime within the proximal fan at the basin margin. Authigenic heavy, light and clay minerals equally contribute to the determination of the fluid chemistry and temperature, as well as the source of chemical constituents of the former pore fluids percolating through the distal fan. Carbonatization was the most pronounced event in the distal hydraulic system and controlled by the presence of biogenic as well as atmospheric carbon. The isotope-based determination of the temperatures, albeit strongly fluctuating, do not exceed 40 °C. The overall pH values determined for the hydraulic regime within the distal fan range from slightly acidic to alkaline. The presence of zeolites attests to some short-lasting but strong deviations from the pH range, mainly towards more alkaline conditions. Heavy, light and clay mineral analyses proved to be a useful tool to determine the (paleo)hydrology of alluvial-fluvial fan systems in tropical arid to semiarid climates.

Dill, Harald G.; Kaufhold, S.; Lindenmaier, F.; Dohrmann, R.; Ludwig, R.; Botz, R.

2013-01-01

140

Sedimentology and palaeontology of the Upper Jurassic Puesto Almada Member (Cañadón Asfalto Formation, Fossati sub-basin), Patagonia Argentina: Palaeoenvironmental and climatic significance  

NASA Astrophysics Data System (ADS)

Six facies associations are described for the Puesto Almada Member at the Cerro Bandera locality (Fossati sub-basin). They correspond to lacustrine, palustrine, and pedogenic deposits (limestones); and subordinated alluvial fan, fluvial, aeolian, and pyroclastic deposits. The lacustrine-palustrine depositional setting consisted of carbonate alkaline shallow lakes surrounded by flooded areas in a low-lying topography. The facies associations constitute four shallowing upward successions defined by local exposure surfaces: 1) a Lacustrine-Palustrine-pedogenic facies association with a 'conchostracan'-ostracod association; 2) a Palustrine facies association representing a wetland subenvironment, and yielding 'conchostracans', body remains of insects, fish scales, ichnofossils, and palynomorphs (cheirolepidiacean species and ferns growing around water bodies, and other gymnosperms in more elevated areas); 3) an Alluvial fan facies association indicating the source of sediment supply; and 4) a Lacustrine facies association representing a second wetland episode, and yielding 'conchostracans', insect ichnofossils, and a palynoflora mainly consisting of planktonic green algae associated with hygrophile elements. The invertebrate fossil assemblage found contains the first record of fossil insect bodies (Insecta-Hemiptera and Coleoptera) for the Cañadón Asfalto Formation. The succession reflects a mainly climatic control over sedimentation. The sedimentary features of the Puesto Almada Member are in accordance with an arid climatic scenario across the Upper Jurassic, and they reflect a strong seasonality with periods of higher humidity represented by wetlands and lacustrine sediments.

Cabaleri, Nora G.; Benavente, Cecilia A.; Monferran, Mateo D.; Narváez, Paula L.; Volkheimer, Wolfgang; Gallego, Oscar F.; Do Campo, Margarita D.

2013-10-01

141

Correlation and dating of Quaternary alluvial-fan surfaces using scarp diffusion  

NASA Astrophysics Data System (ADS)

Great interest has recently been focused on dating and interpreting alluvial-fan surfaces. As a complement to the radiometric methods often used for surface-exposure dating, this paper illustrates a rapid method for correlating and dating fan surfaces using the cross-sectional shape of gullies incised into fan surfaces. The method applies a linear hillslope-diffusion model to invert for the diffusivity age, ?t (m 2), using an elevation profile or gradient (slope) profile. Gullies near the distal end of fan surfaces are assumed to form quickly following fan entrenchment. Scarps adjacent to these gullies provide a measure of age. The method is illustrated on fan surfaces with ages of approximately 10 ka to 1.2 Ma in the arid southwestern United States. Two areas of focus are Death Valley, California, and the Ajo Mountains piedmont, Arizona. Gully-profile morphology is measured in two ways: by photometrically derived gradient (slope) profiles and by ground-surveyed elevation profiles. The ?t values determined using ground-surveyed profiles are more consistent than those determined using photo-derived ?t values. However, the mean ?t values of both methods are comparable. The photometric method provides an efficient way to quantitatively and objectively correlate and relatively-date alluvial-fan surfaces. The ?t values for each surface are determined to approximately 30-50% accuracy.

Hsu, Leslie; Pelletier, Jon D.

2004-06-01

142

Hydrologic processes and geomorphic constraints on urbanization of alluvial fan slopes  

NASA Astrophysics Data System (ADS)

The natural array of processes conveying water and sediment from arid mountain catchments, through alluvial fans, into the base level below is affected by human intervention to an extent unknown until a few years ago. Previously permeable fan terrain has now been replaced by paved impermeable surfaces whose drainage becomes problematic. This problem is intensified with the growth of the town and its building density, particularly vis a vis the smaller catchments. The high sediment yields, with typically predominant bed material components that are supplied by steep catchments, create situations difficult to manage in terms of effective economical and environmentally sensitive criteria. Within the context of the general inadequacy of structural attempts to fully control the floods emanating onto an alluvial fan, a case can be made for exercising the option of local, low-key engineering intervention in protecting fan settlements. Several aspects of the considerations involved are illustrated by examples from the town of Eilat, Southern Negev Desert, Israel, a dynamically developing international tourist resort.

Schick, A. P.; Grodek, T.; Wolman, M. G.

1999-12-01

143

Semi-Arid Land-Surface-Atmosphere (SALSA) Program  

NSDL National Science Digital Library

The Semi-Arid Land-Surface-Atmosphere (SALSA) Program is "a multi-agency, multi-national global-change research effort that seeks to evaluate the consequences of natural and human-induced changes in semi-arid environments." Current research efforts focus on the upper San Pedro River basin, encompassing southeastern Arizona and northeastern Sonora (Mexico). At the site, users will find summaries of current research in the Research section, including study area maps and project summaries for the Transborder Watershed Research Program, Ecosystem Fragmentation and Restoration Study, the 1998 Mexico Campaign (an intensive field campaign "to measure upland water and energy fluxes during August and September 1998"), and Riparian Ecophysiology (coming soon). Also available are numerous archived summaries from research conducted before 1998. An excellent collection of links on global change research and "other information sources related to the hydrology and ecology of the Upper San Pedro River Basin" rounds out the site.

144

Arid and semi-arid rangelands: two thirds of Argentina  

Microsoft Academic Search

Argentina is 3 million km2, with altitudes ranging from 7000 m in the Andes in the west to sea level in the east. Therefore, the diversity in vertical and horizontal biogeographical regions is of extraordinary magnitude. About two thirds of this vast territory is associated with arid and semi-arid rangeland eco- systems. This work provides a comprehensive assessment showing the

Osvaldo A. Fernández; Carlos A. Busso

145

Turkana Grits - a Cretaceous braided alluvial system in northern Kenya  

SciTech Connect

Rather spotty but excellent exposures of the Cretaceous-age Turkana Grits occur near the western shore of Lake Turkana, northern Kenya. These very coarse to pebbly arkosic sandstones and sandy conglomerates were derived from and rest unconformably upon Precambrian metamorphic basement; they are overlain by late Tertiary basaltic flows that comprise much of the volcanics in the East African Rift Zone. The formation ranges up to 2000 ft thick in the Laburr Range. Several outcrops contain sauropod, crocodile, and tortoise remains as well as abundant trunks of petrified wood (Dryoxylon). Five major facies make up the Turkana Grits and record a major episode of continental fluvial deposition in basins flanked by Precambrian basement. Facies 1 is crudely stratified, cobble and boulder conglomerate (clast-supported); Facies 2 is crudely stratified pebble-cobble conglomerate and pebbly sandstone; Facies 3 is trough cross-bedded, very coarse sandstones containing fossils wood and vertebrate remains; Facies 4 is crudely stratified to massive sandstones with ironstone nodules; and Facies 5 is red, purple, and gray mudstone and mud shale with carbonate nodules. Facies 1 through 3 record deposition in proximal to medial braided-stream channel, longitudinal bar and dune complexes. Facies 4 is a lowland, hydromorphic paleosol, and Facies 5 represents overbank and abandoned channel-fill sedimentation in an alluvial plain.

Handford, C.R.

1987-05-01

146

A brief history of Great Basin pikas  

Microsoft Academic Search

ABSTRACT Aim Within the past few decades, seven of the 25 historically described populations of American pikas (Ochotona princeps) in the Great Basin of arid western North America appear to have become extinct. In this paper, the prehistoric record for pikas in the Great Basin is used to place these losses in deeper historical context.

Donald K. Grayson

2005-01-01

147

Lagoa Feia Formation (Lower Cretaceous), Campos basin, offshore Brazil - Rift-Valley-Stage Lacustrine carbonate reservoirs  

Microsoft Academic Search

The Lagoa Feia Formation, buried in excess of 3000 m, is the exploration frontier of the prolific Campos basin. It contains the source beds of all the basin's oil in addition to having its own potential carbonate reservoirs. The faulted margins of the basin fed a system of alluvial fans, sand flats, and mud flats. Alternating dry and rainy period

R. Bertani; T. Petrobras; A. V. Carozzi

1985-01-01

148

Geomorphology, internal structure and evolution of alluvial fans at Motozintla, Chiapas, Mexico  

NASA Astrophysics Data System (ADS)

Alluvial fans and terraces develop in diverse regions responding to different tectonic and climatic conditions. The Motozintla basin is located in the State of Chiapas, southern Mexico and has an E-W orientation following the trace of the left-lateral Polochic Fault. The evolution of the Motozintla basin and the alluvial plain is related to several factors, such as fault movement, intense erosion by hydrometeorological events, and anthropogenic activity. This study presents the geomorphology of the alluvial plain that between the villages of Motozintla and Mazapa de Juárez exposes 31 alluvial fans, 5 hanging terraces and 13 ramps. Fourteen of these alluvial fans have been truncated by the Polochic fault, exposing maximum uplifts of ~ 12 m. The internal structure of truncated fans consists of single massive beds (monolithologic fans) or stacked beds (polygenetic fans). The fans' stratigraphy is made of debris flow deposits separated by paleosols and minor hyperconcentrated flows, fluviatile beds, and pyroclastic fall deposits. The reconstruction of the stratigraphy assisted by radiocarbon geochronology suggests that these fans have been active since late Pleistocene (25 ka) to the present. This record suggests that at least 10 events have been recorded at the fan interior during the past ~ 1840 years. One of these events at 355 ± 65 14C yrs. BP (cal yrs. AD 1438 to 1652) can be correlated across the fans and is likely associated with an extreme hydrometeorologic event. The presence of a 165 ± 60 14C yrs. BP (cal yrs. AD 1652-1949) debris flow deposit within the fans suggests that movement along the Polochic fault formed the fans' scarp afterwards. In fact, a historic earthquake along the fault occurred east of Motozintla on July 22, 1816 with a Mw of 7.5-7.75. Recent catastrophic floods have affected Motozintla in 1998 and 2005 induced by extreme hydrometeorological events and anthropogenic factors. Therefore, scenarios for Motozintla involved several types of mass movement processes that pose a serious hazard and threat to the inhabitants of the region.

Sánchez-Núñez, J. M.; Macías, J. L.; Saucedo, Ricardo; Zamorano, J. J.; Novelo, David; Mendoza, M. E.; Torres-Hernández, J. R.

2015-02-01

149

Modelling the response of an alluvial aquifer to anthropogenic and recharge stresses in the United States Southern Great Plains  

NASA Astrophysics Data System (ADS)

This paper uses Visual MODFLOW to simulate potential impacts of anthropogenic pumping and recharge variability on an alluvial aquifer in semi-arid northwestern Oklahoma. Groundwater withdrawal from the aquifer is projected to increase by more than 50% (relative to 1990) by the year 2050. In contrast, climate projections indicate declining regional precipitation over the next several decades, creating a potential problem of demand and supply. The following scenarios were simulated: (1) projected groundwater withdrawal, (2) a severe drought, (3) a prolonged wet period, and (4) a human adjustment scenario, which assumes future improvements in water conservation measures. Results indicate that the combined impacts of anthropogenic pumping and droughts would create drawdown of greater than 12 m in the aquifer. Spatially, however, areas of severe drawdown will be localized around large-capacity well clusters. The worst impacts of both pumping and droughts will be on stream-aquifer interaction. For example, the projected aquifer pumpage would lead to a total streamflow loss of 40%, creating losing stream system regionally. Similarly, a severe drought would lead to a total streamflow loss of >80%. A post-audit of the model was also carried out to evaluate model performance. By simulating various stress scenarios on the alluvial aquifer, this study provides important information for evaluating management options for alluvial aquifers.

Zume, Joseph T.; Tarhule, Aondover A.

2011-08-01

150

Assessment of global aridity change  

NASA Astrophysics Data System (ADS)

The growing demand for water and the anticipated impacts of climate change necessitate a more reliable assessment of water availability for proper planning and management. Adequate understanding of the past changes in water resources availability can offer crucial information about potential changes in the future. Aridity is a reliable representation of potential water availability, especially at large scales. The present study investigates the changes in global aridity since 1960. The study considers the UNESCO aridity index, with aridity being represented as a function of its two key drivers: precipitation (P) and potential evapotranspiration (PET). First, published literature on changes in trends of P, PET, and aridity across the world is surveyed. This is followed by the analysis of trends in the aridity observations over the period 1960-2009. The nonparametric Mann-Kendall test is performed for trend analysis and outcomes investigated for the presence of clusters of trend across different grid cells the analysis is conducted over. The results suggest that arid zones are becoming slightly more humid and vice versa. They also indicate that the trend in aridity changed, or even reversed, around 1980 in most parts of the world. We speculate that the reason for this was the dramatic change (rise) in global temperature around 1980 as per both published literature and the present analysis, which, in turn, caused similar trends for global PET. We also call for additional research to verify, and possibly confirm, the present results.

Asadi Zarch, Mohammad Amin; Sivakumar, Bellie; Sharma, Ashish

2015-01-01

151

CHANNEL EVOLUTION IN MODIFIED ALLUVIAL STREAMS.  

USGS Publications Warehouse

This study (a) assesses the channel changes and network trends of bed level response after modifications between 1959 and 1972 of alluvial channels in western Tennessee and (b) develops a conceptual model of bank slope development to qualitatively assess bank stability and potential channel widening. A six-step, semiquantitative model of channel evolution in disturbed channels was developed by quantifying bed level trends and recognizing qualitative stages of bank slope development. Development of the bank profile is defined in terms of three dynamic and observable surfaces: (a) vertical face (70 to 90 degrees), (b) upper bank (25 to 50 degrees), and (c) slough line (20 to 25 degrees).

Simon, Andrew; Hupp, Cliff R.

1987-01-01

152

Soils of floodplains in arid regions of Inner Asia (the Zavkhan River, Mongolia)  

NASA Astrophysics Data System (ADS)

The environmental conditions of soil formation and the diversity and classification position of soils developing on the Zavkhan River floodplain are considered, and the morphogenetic and agrochemical properties of these soils are characterized. It is shown that the conditions of soil formation on the floodplain of the Zavkhan River are specified by the mountainous topography, the effect of the large Mongol Els sand massif, the character of the alluviation processes, the groundwater level and salinity, and the regime of floods. The position of the floodplain in the system of altitudinal zones largely dictates the character of the soil cover pattern. In terms of the new Russian soil classification system, the soils studied belong to three trunks, four orders, and seven types: stratified humus alluvial soils, light-humus alluvial soils, light-humus quasigley alluvial soils, light-humus stratozems, and solonchaks. The soils of floodplain ecosystems in arid regions are characterized by low fertility. For their efficient use for pasturing and crop growing, the ecologically balanced differentiated application of manure, mineral fertilizers (NPK), and some microelements is required.

Ubugunov, L. L.; Ubugunova, V. I.

2012-03-01

153

Macro-roughness model of bedrock-alluvial river morphodynamics  

NASA Astrophysics Data System (ADS)

The 1-D saltation-abrasion model of channel bedrock incision of Sklar and Dietrich, in which the erosion rate is buffered by the surface area fraction of bedrock covered by alluvium, was a major advance over models that treat river erosion as a function of bed slope and drainage area. Their model is, however, limited because it calculates bed cover in terms of bedload sediment supply rather than local bedload transport. It implicitly assumes that as sediment supply from upstream changes, the transport rate adjusts instantaneously everywhere downstream to match. This assumption is not valid in general, and thus can give rise unphysical consequences. Here we present a unified morphodynamic formulation of both channel incision and alluviation which specifically tracks the spatiotemporal variation of both bedload transport and alluvial thickness. It does so by relating the cover fraction not to a ratio of bedload supply rate to capacity bedload transport, but rather to the ratio of alluvium thickness to a macro-roughness characterizing the bedrock surface. The new formulation predicts waves of alluviation and rarification, in addition to bedrock erosion. Embedded in it are three physical processes: alluvial diffusion, fast downstream advection of alluvial disturbances and slow upstream migration of incisional disturbances. Solutions of this formulation over a fixed bed are used to demonstrate the stripping of an initial alluvial cover, the emplacement of alluvial cover over an initially bare bed and the advection-diffusion of a sediment pulse over an alluvial bed. A solution for alluvial-incisional interaction in a channel with a basement undergoing net rock uplift shows how an impulsive increase in sediment supply can quickly and completely bury the bedrock under thick alluvium, so blocking bedrock erosion. As the river responds to rock uplift or base level fall, the transition point separating an alluvial reach upstream from an alluvial-bedrock reach downstream migrates upstream in the form of a "hidden knickpoint". A solution for the case of a zone of rock subsidence (graben) bounded upstream and downstream by zones of rock uplift (horsts) yields a steady-state solution that is unattainable with the original saltation-abrasion model. A solution for the case of bedrock-alluvial coevolution upstream of an alluviated river mouth illustrates how the bedrock surface can be progressive buried not far below the alluvium. Because the model tracks the spatiotemporal variation of both bedload transport and alluvial thickness, it is applicable to the study of the incisional response of a river subject to temporally varying sediment supply. It thus has the potential to capture the response of an alluvial-bedrock river to massive impulsive sediment inputs associated with landslides or debris flows.

Zhang, L.; Parker, G.; Stark, C. P.; Inoue, T.; Viparelli, E.; Fu, X.; Izumi, N.

2014-05-01

154

Simulating Fine grained Alluvial Fan Sedimentation on Mars  

NASA Astrophysics Data System (ADS)

The alluvial fans on Mars date to as late as the Hesperian Period and may be representative of the last major episode of widespread fluvial modification to the red planet's surface. These fans lie within enclosed crater basins, and are characterized by their large size (tens of km in length) and gentle gradient (less than 1-3°). The fans generally feature a network of channel distributaries floored with coarser sediment and what we have interpreted to be fine grained overbank deposits that comprise the bulk of the fan material [1]. We have developed a landform evolution model based on the approach of [2] to simulate the growth of these fans in order to answer several questions about their formation, including: (1) what are the characteristics of water discharge (flow magnitude and duration) and sediment supply (quantity and grain size); and (2) what are the associated implications for the responsible climatic environment (e.g. amount and frequency of precipitation sourcing the fans). The model combines discharge and sediment deposition with channel avulsion and abandonment, allowing for an analysis of both the micro and macro scale processes concerning fan formation. Water and sediment is routed through a distributary network that can branch, recombine, and avulse. The model simulates deposition of both coarse-grained bedload and a fine-grained suspended load material that can be deposited overbank during flood events. The model records the stratigraphy of the deposited material in terms of the relative proportions of coarse and fine-grained sediment. Using measures such as channel width, relative proportions of channel versus overbank deposited sediment, and frequency of channel branching, output is statistically compared with digital elevation models that have been produced from high-resolution CTX and HiRISE stereo pairs. Initial results suggest fans formed from hundreds of flow events over many thousands of years. Fan formation processes appear to be similar to those active in terrestrial fans in northern Chile's Atacama Desert. Additional model runs will simulate fan development under different patterns of precipitation (uniform over the fan versus an orographic pattern of greater precipitation on upper crater walls) and variations in sediment size distribution. References: [1] Morgan, A. M., Howard, A. D., Hobley, D. E. J., Moore, J. M., Dietrich, W. E., Williams, R. M. E., Burr, D. M., Grant, J. A., Wilson, S. A., and Matsubara, Y. (in review) Sedimentology and Climatic Environment of Alluvial Fans in the Martian Saheki Crater and a Comparison with Terrestrial Fans in the Atacama Desert [2] Sun, T., C. Paola, G. Parker, and P. Meakin (2002), Water Resour. Res., 38, no.8, 10.

Morgan, A. M.; Howard, A. D.; Moore, J. M.; Beyer, R. A.

2013-12-01

155

Combining point and distributed snowpack data with landscape-based discretization for hydrologic modeling of the snow-dominated Maipo River basin, in the semi-arid Andes of Central Chile.  

NASA Astrophysics Data System (ADS)

The 5000-km2 upper Maipo River Basin, in central Chile's Andes, has an adequate streamgage network but almost no meteorological or snow accumulation data. Therefore, hydrologic model parameterization is strongly subject to model errors stemming from input and model-state uncertainty. In this research, we apply the Cold Regions Hydrologic Model (CRHM) to the basin, force it with reanalysis data downscaled to an appropriate resolution, and inform a parsimonious basin discretization, based on the hydrologic response unit concept, with distributed data on snowpack properties obtained through snow surveys for two seasons. With minimal calibration the model is able to reproduce the seasonal accumulation and melt cycle as recorded in the one snow pillow available for the basin, and although a bias in maximum accumulation persists, snowpack persistence in time is appropriately simulated based on snow water equivalent and snow covered area observations. Blowing snow events were simulated by the model whenever daily wind speed surpassed 8 m/s, although the use of daily instead of hourly data to force the model suggests that this phenomenon could be underestimated. We investigate the representation of snow redistribution by the model, and compare it with small-scale observations of wintertime snow accumulation on glaciers, in a first step towards characterizing ice distribution within a HRU spatial discretization. Although built at a different spatial scale, we present a comparison of simulated results with distributed snow depth data obtained within a 40 km2 sub-basin of the main Maipo watershed in two snow surveys carried out at the end of winter seasons 2011 and 2012, and compare basin-wide SWE estimates with a regression tree extrapolation of the observed data.

McPhee, James; Videla, Yohann

2014-05-01

156

Vertical flow in heavily exploited hard rock and alluvial aquifers  

Microsoft Academic Search

This paper examines the flow in heavily exploited alluvial and hard rock aquifers and demonstrates that vertical components of flow are of great importance. In a typical example of an alluvial aquifer it is shown that most of the discharge from tube wells originates from the phreatic surface flowing vertically through clay layers to the well screens. A second study

K. R. Rushton

1986-01-01

157

Debris-flow dominance of alluvial fans masked by runoff reworking and weathering  

NASA Astrophysics Data System (ADS)

Arid alluvial fan aggradation is highly episodic and fans often comprise active and inactive sectors. Hence the morphology and texture of fan surfaces are partly determined by secondary processes of weathering and erosion in addition to primary processes of aggradation. This introduces considerable uncertainty in the identification of formative processes of terrestrial and Martian fans from aerial and satellite imagery. The objectives of this study are (i) to develop a model to describe the sedimentological and morphological evolution of inactive fan surfaces in arid settings, and (ii) to assess the relative importance of primary processes of aggradation and secondary processes of weathering and reworking for surface morphology and sedimentology and for the stratigraphic record. We studied an alluvial fan characterized by a recently active sector and a long-abandoned, inactive sector along the coast of the hyperarid Atacama Desert. Here, rates of primary geomorphic activity are exceptionally low because of extreme aridity, while weathering rates are relatively high because of the effects of coastal fogs. Long-term processes of fan aggradation and reworking were determined through sedimentological facies analysis of stratigraphic sections. Ground surveys for textural and morphological patterns at the fan surface were integrated with remote-sensing by an Unmanned Airborne Vehicle (UAV). Discharges and sediment-transport capacities were calculated to estimate the efficiency of secondary runoff in reshaping the inactive fan sector. Stratigraphic sections reveal that the fan was dominantly aggraded by debris flows, whereas surface morphology is dominated by debris-flow signatures in the active sector and by weathering and runoff on the inactive sector. On the latter, rapid particle breakdown prevents the formation of a coarse desert pavement. Furthermore, relatively frequent local runoff events erode proximal debris-flow channels on the inactive sector to form local lag deposits and accumulate fine sediment in low-gradient distal channels, forming a well-developed drainage pattern that would suggest a runoff origin from aerial images. Nevertheless, reworking is very superficial and barely preserved in the stratigraphic record. This implies that fans on Earth and Mars that formed dominantly by sporadic mass flows may be masked by a surface morphology related to other processes.

de Haas, Tjalling; Ventra, Dario; Carbonneau, Patrice E.; Kleinhans, Maarten G.

2014-07-01

158

Quaternary alluvial-fan development, climate and morphologic dating of fault scarps in Laguna Salada, Baja California, Mexico  

NASA Astrophysics Data System (ADS)

Late Quaternary slip across the Cañada David detachment has produced an extensive array of Quaternary scarps cutting alluvial-fans along nearly the entire length (~ 60 km) of the range-bounding detachment. Eight regional alluvial-fan surfaces (Q 1 [youngest] to Q 8 [oldest]) are defined and mapped along the entire Sierra el Mayor range-front. Terrestrial cosmogenic nuclide 10Be concentrations from individual boulders on alluvial-fan surfaces Q 4 and Q 7 yield surface exposure ages of 15.5 ± 2.2 ka and 204 ± 11 ka, respectively. Formation of the fans is probably tectonic, but their evolution is strongly moderated by climate, with surfaces developing as the hydrological conditions have changed in response to climate change on Milankovitch timescales. Systematic mapping reveals that the fault scarp array along active range-bounding faults in Sierras Cucapa and El Mayor can be divided into individual rupture zones, based on cross-cutting relationships with alluvial-fans. Quantitative morphological ages of the Laguna Salada fault-scarps, derived from linear diffusive degradation modeling, are consistent with the age of the scarps based on cross-cutting relationships. The weighted means of the maximum mass diffusivity constant for all scarps with offsets < 4 m is 0.051 and 0.066 m 2/ka for the infinite and finite-slope solutions of the diffusion equation, respectively. This estimate is approximately an order of magnitude smaller than the lowest diffusivity constants documented in other regions and it probably reflects the extreme aridity and other microclimatic conditions that characterize the eastern margin of Laguna Salada.

Spelz, Ronald M.; Fletcher, John M.; Owen, Lewis A.; Caffee, Marc W.

2008-12-01

159

Chloride mass-balance method for estimating ground water recharge in arid areas: Examples from western Saudi Arabia  

USGS Publications Warehouse

The chloride mass-balance method, which integrates time and aerial distribution of ground water recharge, was applied to small alluvial aquifers in the wadi systems of the Asir and Hijaz mountains in western Saudi Arabia. This application is an extension of the method shown to be suitable for estimating recharge in regional aquifers in semi-arid areas. Because the method integrates recharge in time and space it appears to be, with certain assumptions, particularly well suited for and areas with large temporal and spatial variation in recharge. In general, recharge was found to be between 3 to 4% of precipitation - a range consistent with recharge rates found in other arid and semi-arid areas of the earth.

Bazuhair, A.S.; Wood, W.W.

1996-01-01

160

Causes of farmland salinization and remedial measures in the Aral Sea basin—Research on water management to prevent secondary salinization in rice-based cropping system in arid land  

Microsoft Academic Search

In the Lower Syr Darya region of the Aral Sea basin, secondary salinization of irrigated lands has been a crucial problem. To clarify the mechanism of secondary salinization, studies on water and salt behavior were conducted in an irrigation block where a rice-based cropping system has been practiced. Results of on-site studies are summarized as follows: (1) since the performance

Yoshinobu Kitamura; Tomohisa Yano; Toshimasa Honna; Sadahiro Yamamoto; Koji Inosako

2006-01-01

161

Annual plants in arid and semi-arid desert regions  

Microsoft Academic Search

Annual plants are the main vegetation in arid and semi-arid desert regions. Because of their unique traits, they are the optimal\\u000a experimental subjects for ecological studies. In this article, we summarize annual plants’ seed germination strategies, seedling\\u000a adaptability mechanism to environments, seed dispersal, and soil seed banks. We also discuss the biotic and abiotic factors\\u000a affecting the composition and dynamics

Xuehua Li; Xiaolan Li; Deming Jiang; Zhimin Liu; Qinghe Yu

2008-01-01

162

Assessing an Alluvial Channel Behavioral Problem  

NASA Astrophysics Data System (ADS)

Modern alluvial rivers appear to be highly organized physical systems. Although empirical relations provide much insight into the fundamental organizing principles of rivers across multiple scales, current theory does not fully explain these relations. In particular the bankfull Shields stress and particle Reynolds number characterize mutual adjustments of basal shear stress and median grain size of the sediment load within a channel, and it has been derived that the bankfull Shields stress should scale with the particle Reynolds number to the -2/3 power. However, empirical results do not support this. In order to explore this discrepancy we develop theory and add new data to existing datasets of alluvial bankfull properties. We compiled a dataset of 641 bankfull measurements from previous compilations and new, previously un-compiled studies. Using Bayesian linear regression, we find a relation between the logarithms of bankfull Shields stress and particle Reynolds number with a slope that has a 95% high posterior probability density interval probability of (-0.499, -0.463). Either a parameter is missing or one of the current parameters is incorrectly formulated. We propose that the particle Reynolds number is nondimensionalized in a way that, although is correctly unitless, is not the scaled internally in the most advantageously for this application. Unfortunately, without measured variability of kinematic viscosity, fluid density, or sediment density, the data is confounded and a new, more correct formulation of the particle Reynolds number cannot be proposed. A future work could resolve this issue with variation of any one of these parameters. Results from that dataset will have application to a wide range of modern and ancient planetary environments.

Trampush, S.; McElroy, B. J.; Huzurbazar, S. V.

2012-12-01

163

Alluvial Bars of the Obed Wild and Scenic River, Tennessee  

USGS Publications Warehouse

In 2004, the U.S. Geological Survey (USGS) and the National Park Service (NPS) initiated a reconnaissance study of alluvial bars along the Obed Wild and Scenic River (Obed WSR), in Cumberland and Morgan Counties, Tennessee. The study was partly driven by concern that trapping of sand by upstream impoundments might threaten rare, threatened, or endangered plant habitat by reducing the supply of sediment to the alluvial bars. The objectives of the study were to: (1) develop a preliminary understanding of the distribution, morphology, composition, stability, and vegetation structure of alluvial bars along the Obed WSR, and (2) determine whether evidence of human alteration of sediment dynamics in the Obed WSR warrants further, more detailed examination. This report presents the results of the reconnaissance study of alluvial bars along the Obed River, Clear Creek, and Daddys Creek in the Obed WSR. The report is based on: (1) field-reconnaissance visits by boat to 56 alluvial bars along selected reaches of the Obed River and Clear Creek; (2) analysis of aerial photographs, topographic and geologic maps, and other geographic data to assess the distribution of alluvial bars in the Obed WSR; (3) surveys of topography, surface particle size, vegetation structure, and ground cover on three selected alluvial bars; and (4) analysis of hydrologic records.

Wolfe, W.J.; Fitch, K.C.; Ladd, D.E.

2007-01-01

164

Long-term interactions between man and the fluvial environment - case of the Diyala alluvial fan, Iraq  

NASA Astrophysics Data System (ADS)

The Mesopotamian alluvial plain is dominated by large aggradading river systems (the Euphrates, Tigris and their tributaries), which are prone to avulsions. An avulsion can be defined as the diversion of flow from an existing channel onto the floodplain, eventually resulting in a new channel belt. Early civilizations depended on the position of rivers for their economic survival and hence the impact of channel shifts could be devastating (Wilkinson 2003; Morozova 2005; Heyvaert & Baeteman 2008). Research in the Iranian deltaic part of the Mesopotamian plain has demonstrated that deliberate human action (such as the construction of irrigation canals and dams) triggered or obstructed the alluvial processes leading to an avulsion on fluvial megafans (during preconditioning, triggering and post-triggering stages) (Walstra et al. 2010; Heyvaert et al. 2012, Heyvaert et al.2013). Thus, there is ample evidence that the present-day alluvial landscapes in the region are the result of complex interactions between natural and anthropogenic processes. Here we present a reconstruction of the Late Holocene evolution of the Diyala alluvial fan (one of the main tributaries of the Tigris in Iraq), with particular attention to the relations between alluvial fan development, changes in channel pattern, the construction of irrigation networks and the rise and collapse of societies through historic times. The work largely draws on the use of remote sensing and GIS techniques for geomorphological mapping, and previously published archaeological field data (Adams 1965). By linking archaeological sites of known age with traces of ancient irrigation networks we were able to establish a chronological framework of alluvial activity of the Diyala alluvial fan. Our results demonstrate that centralized and technologically advanced societies were able to maintain a rapidly aggradading distibutary channel system, supplying water and sediment across the entire alluvial fan. As a consequence, during these periods (Parthian, Sasanian and again in modern times), significant human modification of the landscape took place. Periods of societal decline are associated with reduced human impact and the development of a single-threaded incising river system. Adams, R.M. (1965). Land behind Baghdad: A history of settlement on the Diyala plains. University of Chicago Press, Chicago, Illinois. Heyvaert, V.M.A. & Baeteman, C. (2008). A Middle to Late Holocene avulsion history of the Euphrates river: a case study from Tell ed-D-er, Iraq, Lower Mesopotamia. Quaternary Science Reviews, 27, 2401-2410. Heyvaert, V. M. A., Walstra, J., Verkinderen, P., Weerts, H. J. T. & Ooghe, B. (2012). The role of human interference on the channel shifting of the river Karkheh in the Lower Khuzestan plain (Mesopotamia, SW Iran). Quaternary International, 251, 52-63. Heyvaert, V.M.A., Walstra, J., Weerts, H.J.T. (2013). Human impact on avulsion and fan development in a semi-arid region: examples from SW Iran. Abstractbook of the 10th International Fluvial Sedimentology Conference, July 2013,Leeds, United Kingdom. Morozova, G.S. (2005). A review of Holocene avulsions of the Tigris and Euphrates rivers and possible effects on the evolution of civilizations in lower Mesopotamia. Geoarchaeology, 20, 401-423. Walstra, J., Heyvaert, V. M. A. & Verkinderen, P. (2010). Assessing human impact on alluvial fan development: a multidisciplinary case-study from Lower Khuzestan (SW Iran). Geodinamica Acta, 23, 267-285. Wilkinson, T.J. (2003). Archaeological Landscapes of the Near East. The University of Arizona Press, Tucson, Arizona.

Heyvaert, Vanessa M. A.; Walstra, Jan; Mortier, Clément

2014-05-01

165

From source to sink in the sediment cascade of the Hei-River Basin: Implications for late Quaternary landscape dynamics in the Gobi Desert, NW China  

NASA Astrophysics Data System (ADS)

The Hei River Basin with a catchment size of ~130,000 km² is host to one of the largest continental alluvial fans in the world. The basin comprises: (1) its high-elevated river sources in the glacier and the permafrost zone of the Qilian Mountains, (2) the semi-arid foreland of the Hexi Corridor in the middle reaches and (3) the endorheic Ejina Basin (Gaxun Nur Basin) as its recent sink. The river basin is characterized by small subcatchments of hyper-arid mountain ranges of the Gobi-Tienshan and Beishan as well as of smooth and fuzzy water divides of the Hexi-Corridor and the Badain Jaran Sand Sea. Up to 300 m of Quaternary sediments establish the large Ejina Basin, with a size of 28,000 km², as an excellent archive for environmental reconstructions located at the recent intersection of westerly and monsoonal air masses. Three sediment cores (up to 230 m long) provide evidence of sedimentation dynamics over the last 250,000 years, and cover at least two terminations since OIS 6. The sediments have to be regarded as a result of the interplay between tectonic activity and climate dynamics, accompanied by a related eolian and hydrological response of the catchment. Thus, it is crucial to understand and reconstruct the sedimentary processes along the huge sediment cascades, and to identify the most important sediment sources. Here we present a provenance analysis from mineralogical fingerprints of modern sediments that have been deposited along recent pathways from the sources to the Ejina Basin. The methodical approach combines the analysis of clay minerals, bulk mineralogy, and bulk geochemistry. Furthermore, we use heavy mineral data obtained from automated particle-analysis via a computer-controlled scanning electron microscope (CCSEM) and XRD measurements. We analyzed ~200 surface samples from the whole catchment as reference material, as well as the upper 19 m of cored sediments, to gain insight into temporal changes of depositional processes and provenance. Geostatistical analyses of the compositional data reveal a clear discrimination between sediments from the Qilian Shan in the south and from local basin sediments in the north. Moreover the mineralogical fingerprints allow the differentiation of sources from intrusive rocks that are dominant in the Bei Shan mountain sub-catchment, and from greenschist-bearing metamorphic rocks, that are widespread in the Qilian Mountain catchment. Finally, we draw conclusions about the main transport processes and pathways from assumed source regions to the sink (Ejina Basin). The provenance analysis of the sediment core reveals strong changes from local (Bei Shan) to long-distant (Qilian Shan) sources. The Late Pleistocene record reveals frequently changing sediment supply between periodic high mountain runoff and local episodic runoff. We assume that these variations are related to basin internal processes (e.g. fan dynamics, tectonics) and changing environmental conditions that are linked with variations in meltwater runoff and precipitation in the upper reaches of the southern catchment. These conclusions are supported by grain size characteristics that indicate phases of predominant alluvial activity and limnic deposition around the Late Glacial to Holocene transition and enhanced pre-Holocene eolian activity.

Schimpf, Stefan; Nottebaum, Veit; Diekmann, Bernhard; Hartmann, Kai; Lehmkuhl, Frank; Wünnemann, Bernd; Zhang, Chi

2014-05-01

166

Mass balance from alluvial fan isopachs: a case study from the Chinese Tian Shan  

NASA Astrophysics Data System (ADS)

Continental surfaces are incessantly reworked through erosion and sedimentation. Markers of erosion within drainage areas are often scarce and temporary, but at the outlet of mountain belts, more continuous and perennial records of deposition can be found in alluvial fans. These fans are constructed by the deposition through time of the coarse part of sediments transported by rivers. Volume of sediments trapped in alluvial fans can then be used in order to reconstruct sediment fluxes coming out from their catchment areas and the associated erosion rates. Quantifying such erosion rates is of great interest for the study of mass transfer. It is also necessary to understand relief dynamics, as well as the influence of tectonic and climate on this dynamics. We propose here a complete method to estimate erosion fluxes from alluvial fans in a specific area, the northern piedmont of the Tian Shan in China. Along the piedmont of this range, series of fans of different ages are clearly identified. In particular, abandoned fans (which were active before 10 000 years ago) are well preserved in the landscape, and easily identifiable on satellite images. These fans have been deeply incised during the last deglaciation (about 10 000 years ago), and therefore, their basal surface can be observed. In this specific area, it is then possible to obtain field constraints on the real fan thickness. First, we draw a morpho-sedimentary map of the fans and their drainage basins. Then, we went on the field to estimate the fan thickness wherever it is possible. Finally, based on this data set, and on geometrical considerations, we built isopach maps of the fans and calculate their volumes. These 3D reconstructions can then be compared to the geometrical relationships classically used to assess alluvial fan volumes from their upper surface only. Erosion rates of ten drainage basins can be derived from these volumes, allowing a sink to source investigation, for the period of fan activity. In north Tian Shan, these erosion rates can be compared with other values calculated from bedload measurements and cosmogenic data, providing thus an opportunity to discuss results coming from different methods

Guerit, Laure; Barrier, Laurie; Métivier, François; Jolivet, Marc; Fu, Bihong

2013-04-01

167

Water sources accessed by arid zone riparian trees in highly saline environments, Australia.  

PubMed

The flow regimes of arid zone rivers are often highly variable, and shallow groundwater in the alluvial aquifers can be very saline, thus constraining the availability and quality of the major water sources available to riparian trees-soil water, shallow groundwater and stream water. We have identified water sources and strategies used by riparian trees in more highly saline and arid conditions than previously studied for riparian trees of arid zone rivers. Our research focused on the riparian species Eucalyptus coolabah, one of the major riparian trees of ephemeral arid zone rivers in Australia. The water sources available to this riparian tree were examined using delta(18)O isotope data from xylem, soil water, groundwater and surface water. Additionally, soil chloride and matric potential data were used to infer zones of water availability for root uptake. Despite the saline conditions, the trees used a mixture of soil water and groundwater sources, but they did not use surface water directly. The study identified three strategies used to cope with typically high groundwater and soil water salinities. Firstly, the trees preferentially grow in zones of most frequent flushing by infiltrating streamflow, such as the bank-tops of channels. Secondly, the trees limit water use by having low transpiration rates. Thirdly, the trees are able to extract water at very low osmotic potentials, with water uptake continuing at chloride concentrations of at least 20,000-30,000 mg L(-1). PMID:18270743

Costelloe, Justin F; Payne, Emily; Woodrow, Ian E; Irvine, Elizabeth C; Western, Andrew W; Leaney, Fred W

2008-05-01

168

Inference of lithologic distributions in an alluvial aquifer using airborne transient electromagnetic surveys  

USGS Publications Warehouse

An airborne transient electromagnetic (TEM) survey was completed in the Upper San Pedro Basin in southeastern Arizona to map resistivity distributions within the alluvial aquifer. This investigation evaluated the utility of 1D vertical resistivity models of the TEM data to infer lithologic distributions in an alluvial aquifer. Comparisons of the resistivity values and layers in the 1D resistivity models of airborne TEM data to 1D resistivity models of ground TEM data, borehole resistivity logs, and lithologic descriptions in drill logs indicated that the airborne TEM identified thick conductive fine-grained sediments that result in semiconfined groundwater conditions. One-dimensional models of ground-based TEM surveys and subsurface lithology at three sites were used to determine starting models and constraints to invert airborne TEM data using a constrained Marquardt-styleunderparameterized method. A maximum structural resolution of six layers underlain by a half-space was determined from the resistivity structure of the 1D models of the ground TEM data. The 1D resistivity models of the airborne TEM data compared well with the control data to depths of approximately 100 m in areas of thick conductive silt and clay and to depths of 200 m in areas of resistive sand and gravel. Comparison of a 3D interpolation of the 1D resistivity models to drill logs indicated resistive (mean of 65 ohm-m ) coarse-grained sediments along basin margins and conductive (mean of 8 ohm-m ) fine-grained sediments at the basin center. Extents of hydrologically significant thick silt and clay were well mapped by the 1D resistivity models of airborne TEM data. Areas of uncertain lithology remain below conductive fine-grained sediments where the 1D resistivity structure is not resolved: in areas where multiple lithologies have similar resistivity values and in areas of high salinity.

Dickinson, Jesse E.; Pool, D.R.; Groom, R.W.; Davis, L.J.

2010-01-01

169

Aerodynamic roughness parameters for semi-arid natural shrub communities of Wyoming, USA  

Microsoft Academic Search

Estimates of aerodynamic roughness length (z0) were calculated at nine sites for natural sagebrush (Artemisia tridentata spp.), saltbush (Atriplex nuttallii) and greasewood (Sarcobatus vermiculatus) plant communities in two semi-arid basins in Wyoming, USA. Estimates were based on wind and temperature profiles measured above the plant canopies during summer (August) of 1994 and fall (September and October) of 1995. Values of

Kenneth L. Driese; William A. Reiners

1997-01-01

170

Environmental changes documented by sedimentation of Lake Yiema in arid China since the late Glaciation  

Microsoft Academic Search

In this study, a 6 m long core (16,000 BP) at the center of the dry Lake Yiema, a closed lake of Shiyang River drainage in Minqin Basin of the arid northwestern China, was retrieved to recover the history of climate changes and lake evolution in the area. Five radiocarbon dates on organic matter were obtained. A chronological sequence is

Fa-Hu Chen; Qi Shi; Jian-Min Wang

1999-01-01

171

Environmental changes documented by sedimentation of Lake Yiema in arid China since the Late Glaciation  

Microsoft Academic Search

In this study, a 6 m long core (16,000 BP) at the center of the dry Lake Yiema, a closed lake of Shiyang River drainage in Minqin Basin of the arid northwestern China, was retrieved to recover the history of climate changes and lake evolution in the area. Five radiocarbon dates on organic matter were obtained. A chronological sequence is

Fa-Hu Chen; Qi Shi; Jian-Min Wang

1999-01-01

172

A review of stratigraphy and sedimentary environments of the Karoo Basin of South Africa  

NASA Astrophysics Data System (ADS)

The Karoo Supergroup covers almost two thirds of the present land surface of southern Africa. Its strata record an almost continuous sequence of continental sedimentation that began in the Permo-Carboniferous (280 Ma) and terminated in the early Jurassic 100 million years later. The glacio-marine to terrestrial sequence accumulated in a variety of tectonically controlled depositories under progressively more arid climatic conditions. Numerous vertebrate fossils are preserved in these rocks, including fish, amphibians, primitive aquatic reptiles, primitive land reptiles, more advanced mammal-like reptiles, dinosaurs and even the earliest mammals. Palaeoenvironmental analysis of the major stratigraphic units of the Karoo sequence demonstrates the effects of more localised tectonic basins in influencing depositional style. These are superimposed on a basinwide trend of progressive aridification attributed to the gradual northward migration of southwestern Gondwanaland out of polar climes and accentuated by the meteoric drying effect of the surrounding land masses. Combined with progressive climatic drying was a gradual shrinking of the basin brought about by the northward migration of the subducting palaeo-Pacific margin to the south. Following deposition of the Cape Supergroup in the pre-Karoo basin there was a period of uplift and erosion. At the same time the southern part of Gondwana migrated over the South Pole resulting in a major ice-sheet over the early Karoo basin and surrounding highlands. Glacial sedimentation in both upland valley and shelf depositories resulted in the basal Karoo Dwyka Formation. After glaciation, an extensive shallow sea remained over the gently subsiding shelf fed by large volumes of meltwater. Black clays and muds accumulated under relatively cool climatic conditions (Lower Ecca) with perhaps a warmer "interglacial" during which the distinctive Mesosaurus-bearing, carbonaceous shales of the Whitehill Formation were deposited. Deformation of the southern rim of the basin, caused by the subducting palaeo-Pacific plate, resulted in mountain ranges far to the south. Material derived from this source, as well as granitic uplands to the west and morth-east, was deposited on large deltas that built out into the Ecca sea (Upper Ecca). The relatively cool climate and lowland setting promoted thick accumulations of peat on the coastal and delta plains and which now constitute the major coal reserves of southern Africa. Later the prograding deltas coalesced to fill most of the basin after which fluvial sedimentation of the Beaufort Group dominated. The climate by this time (Late Permian) had warmed to become semi-arid with highly seasonal rainfall. The central parts of the basin were for the most part drained by fine-grained meanderbelts and semi-permanent lakes. Significant stratabound uranium reserves have been delimited in the channel sandstones of the Beaufort Group in the southwestern parts of the basin. Pulses of uplift in the southern source areas combined with a possible orogenic effect resulted in two coarser-grained alluvial fans prograding into the more central parts of the basin (Katberg Sandstone Member and Molteno Formation). In the upper Karoo sequence progressive aridification dominated depositional style with playa lake and wadi-type environments (Elliot Formation) that finally gave way to a dune sand dominated system (Clarens Formation). Basinwide volcanic activity of the early Jurassic Drakensberg Group brought deposition in the Karoo Basin to a close.

Smith, R. M. H.

173

Empirical assessment of theory for bankfull characteristics of alluvial channels  

NASA Astrophysics Data System (ADS)

compiled a data set of 541 bankfull measurements of alluvial rivers (see supporting information) and used Bayesian linear regression to examine empirical and theoretical support for the hypothesis that alluvial channels adjust to a predictable condition of basal shear stress as a function of sediment transport mode. An empirical closure based on channel slope, bankfull channel depth, and median grain size is proposed and results in the scaling of bankfull Shields stress with the inverse square root of particle Reynolds number. The empirical relationship is sufficient for purposes of quantifying paleohydraulic conditions in ancient alluvial channels. However, it is not currently appropriate for application to alluvial channels on extraterrestrial bodies because it depends on constant-valued, Earth-based coefficients.

Trampush, S. M.; Huzurbazar, S.; McElroy, B.

2014-12-01

174

The Shape of Trail Canyon Alluvial Fan, Death Valley  

NASA Technical Reports Server (NTRS)

A modified conic equation has been fit to high-resolution digital topographic data for Trail Canyon alluvial fan in Death Valley, California. Fits were accomplished for 3 individual fan units of different age.

Farr, Tom G.; Dohrenwend, John C.

1993-01-01

175

Surface texture analysis of southern Tuli Basin sediments: Implications for Limpopo Valley geoarchaeological contexts  

NASA Astrophysics Data System (ADS)

The Hackthorne 1 site (southern Tuli Basin, South Africa) is situated on a sand-covered plateau adjacent to the Limpopo River Valley. Although the site is well known for its Stone Age archaeology, the past environmental contexts (particularly sedimentological/geomorphological) are not well known. We examine the Hackthorne sand grain surface textures, so as to provide some insight on the site specific and regional depositional history. Quartz sands at Hackthorne were collected from surface sands and from underlying weathered calcrete. SEM analysis was performed on sand grains, through which several mechanical and chemical microtextures were identified. Microtextures typical of fluvial environments were found only on grains derived from the plateau calcrete host sediment, whilst the surface sands exhibited only textures associated with aeolian environments. The results indicate that the calcrete host sediment is composed of alluvium, and that the surface sands mantling the Hackthorne Plateau are not deflated from the alluvial deposits in the Limpopo Valley, but may rather be derived from distant aeolian sources. The deposition of aeolian sands is consistent with OSL dates which place sand deposition, or remobilization, at 23 and 15 kya, periods in southern Africa associated with increased aridity.

Le Baron, Joel C.; Grab, Stefan W.; Kuman, Kathleen

2011-03-01

176

Paleogeographic and paleotectonic setting of sedimentary basins in the Sevier thrust belt and hinterland, eastern Great Basin  

SciTech Connect

The eastern Great Basin contains a sparse record of broadly distributed Cretaceous sedimentary rocks which record: evolution of intermontane basins during development of the Sevier (Sv)contractional orogen and incipient extensional collapse of the elevated Sv hinterland (east-central NV), and complex tectono-sedimentary interactions between frontal thrust belt structures and the western margin of the adjacent foreland basin. Palinspastic restoration of these strata and associated structures to pre-Tertiary extension positions reveals a clearer pictures of Cretaceous basin paleogeography and allows comparison with the Puna/Altiplano plateau and precordillera thrust belt of the Neogene Andean orogen. Two syntectonic stratal assemblages are present in east-central NV. Lower Cretaceous alluvial strata (Newark Canyon Fm) record basin development coeval with emergence of contractional structures in the Sv hinterland. Localized early Cretaceous basins were possibly piggyback immature; periods of open drainage to the to the east and south suggest connection with the nascent Sv foreland basin to the east (Cedar Mountain/Sanpete Fms) prior to major thrust loading in central Utah. Development of hinterland structures is almost recorded by Aptian-Albian foreland basin alluvial deposits in SW Utah (Dakota Fm) and southern Nevada (Willow Tank Fm). Upper Cretaceous to Eocene strata (Sheep Pass Fm) record inception of regionally abundant alluvial-lacustrine basins which developed in response to onset of latest Cretaceous extension and associated collapse of the Sv hinterland. Evolution of the structurally complex western margin of the Sv foreland basin is recorded in Cretaceous through Eocene strata deposited in: piggyback basins which were at times hydrologically connected to the adjacent foreland basins, and thrust-proximal portions of the foreland basin. These proximal areas are characterized by folding and faulting of basin fill and development of intrabasinal unconformities.

Schmitt, J.G. (Montana State Univ., Bozeman, MT (United States). Dept. of Earth Sciences); Vandervoort, D.S. (Cornell Univ., Ithaca, NY (United States). Dept. of Geological Sciences); Suydam, J.D. (Washington State Univ., Pullman, WA (United States). Dept. of Geology)

1993-04-01

177

Caribbean basin framework, 3: Southern Central America and Colombian basin  

SciTech Connect

The authors recognize three basin-forming periods in southern Central America (Panama, Costa Rica, southern Nicaragua) that they attempt to correlate with events in the Colombian basin (Bowland, 1984): (1) Early-Late Cretaceous island arc formation and growth of the Central American island arc and Late Cretaceous formation of the Colombian basin oceanic plateau. During latest Cretaceous time, pelagic carbonate sediments blanketed the Central American island arc in Panama and Costa Rica and elevated blocks on the Colombian basin oceanic plateau; (2) middle Eocene-middle Miocene island arc uplift and erosion. During this interval, influx of distal terrigenous turbidites in most areas of Panama, Costa Rica, and the Colombian basin marks the uplift and erosion of the Central American island arc. In the Colombian basin, turbidites fill in basement relief and accumulate to thicknesses up to 2 km in the deepest part of the basin. In Costa Rica, sedimentation was concentrated in fore-arc (Terraba) and back-arc (El Limon) basins; (3) late Miocene-Recent accelerated uplift and erosion of segments of the Central American arc. Influx of proximal terrigenous turbidites and alluvial fans in most areas of Panama, Costa Rica, and the Colombian basin marks collision of the Panama arc with the South American continent (late Miocene early Pliocene) and collision of the Cocos Ridge with the Costa Rican arc (late Pleistocene). The Cocos Ridge collision inverted the Terraba and El Limon basins. The Panama arc collision produced northeast-striking left-lateral strike-slip faults and fault-related basins throughout Panama as Panama moved northwest over the Colombian basin.

Kolarsky, R.A.; Mann, P. (Univ. of Texas, Austin (United States))

1991-03-01

178

Oblique-slip sedimentation and deformation in Nonacho basin (early Proterozoic), Northwest Territories, Canada  

Microsoft Academic Search

The Nonacho basin shares several traits with molassoid basins formed in oblique-slip settings: great thickness (about 9 km, 6 mi) of siliciclastic sediments deposited in alluvial fan, fan-delta, braided stream, beach, deltaic, and lacustrine environments; synsedimentary faults which activated nearby sources; rapid sedimentation and subsidence; telescoped facies transitions, particularly adjacent to active faults; extremely variable thickness of lithostratigraphic units; diachronous

L. B. Aspler; J. A. Donaldson

1984-01-01

179

Tectonic controls on the geomorphic evolution of alluvial fans in the Piedmont Zone of Ganga Plain, Uttarakhand, India  

NASA Astrophysics Data System (ADS)

The Piedmont Zone is the least studied part of the Ganga Plain. The northern limit of the Piedmont Zone is defined by the Himalayan Frontal Thrust (HFT) along which the Himalaya is being thrust over the alluvium of the Ganga Plain. Interpretation of satellite imagery, Digital Terrain Models (DTMs) and field data has helped in the identification and mapping of various morphotectonic features in the densely forested and cultivated Piedmont Zone in the Kumaun region of the Uttarakhand state of India. The Piedmont Zone has formed as a result of coalescing alluvial fans, alluvial aprons and talus deposits. The fans have differential morphologies and aggradation processes within a common climatic zone and similar litho-tectonic setting of the catchment area. Morphotectonic analysis reveals that the fan morphologies and aggradation processes in the area are mainly controlled by the ongoing tectonic activities. Such activities along the HFT and transverse faults have controlled the accommodation space by causing differential subsidence of the basin, and aggradation processes by causing channel migration, channel incision and shifting of depocentres. The active tectonic movements have further modified the landscape of the area in the form of tilted alluvial fan, gravel ridges, terraces and uplifted gravels.

Goswami, Pradeep K.; Pant, Charu C.; Pandey, Shefali

2009-06-01

180

Climate change and groundwater management in the Upper Guadiana Basin  

Microsoft Academic Search

The Upper Guadiana Basin is a semi-arid region located in the centre of Spain. From a morphological point of view it is a very flat region. Rivers just have ephemeral streams which usually infiltrate into the aquifers. So groundwater flow plays an important role in this basin. Since late in 1970s intensive water abstractions have been carried out in the

M. Candel; A. Yustres; V. Navarro

2009-01-01

181

A summary of methods for the collection and analysis of basic hydrologic data for arid regions  

USGS Publications Warehouse

This report summarizes and discusses current methods of collecting and analyzing the data required for a study of the basic hydrology of arid regions. The fundamental principles behind these methods are no different than those that apply to studies of humid regions, but in arid regions the infrequent occurrence of precipitation, the great variability of the many hydrologic elements, and the inaccessibility of most basins usually make it economically infeasible to use conventional levels of instrumentation. Because of these economic considerations hydrologic studies in arid regions have been commonly of the reconnaissance type; the more costly detailed studies are generally restricted to experimental basins and to those basins that now have major economic significance. A thorough search of the literature and personal communication with workers in the field of arid-land hydrology provided the basis for this summary of methods used in both reconnaissance and detailed hydrologic studies. The conclusions reached from a consideration of previously reported methods are interspersed in this report where appropriate.

Rantz, S.E.; Eakin, T.E.

1971-01-01

182

Calibration of the ARID robot  

NASA Technical Reports Server (NTRS)

The author has formulated a new, general model for specifying the kinematic properties of serial manipulators. The new model kinematic parameters do not suffer discontinuities when nominally parallel adjacent axes deviate from exact parallelism. From this new theory the author develops a first-order, lumped-parameter, calibration-model for the ARID manipulator. Next, the author develops a calibration methodology for the ARID based on visual and acoustic sensing. A sensor platform, consisting of a camera and four sonars attached to the ARID end frame, performs calibration measurements. A calibration measurement consists of processing one visual frame of an accurately placed calibration image and recording four acoustic range measurements. A minimum of two measurement protocols determine the kinematics calibration-model of the ARID for a particular region: assuming the joint displacements are accurately measured, the calibration surface is planar, and the kinematic parameters do not vary rapidly in the region. No theoretical or practical limitations appear to contra-indicate the feasibility of the calibration method developed here.

Doty, Keith L

1992-01-01

183

Calibration of the ARID robot  

NASA Astrophysics Data System (ADS)

The author has formulated a new, general model for specifying the kinematic properties of serial manipulators. The new model kinematic parameters do not suffer discontinuities when nominally parallel adjacent axes deviate from exact parallelism. From this new theory the author develops a first-order, lumped-parameter, calibration-model for the ARID manipulator. Next, the author develops a calibration methodology for the ARID based on visual and acoustic sensing. A sensor platform, consisting of a camera and four sonars attached to the ARID end frame, performs calibration measurements. A calibration measurement consists of processing one visual frame of an accurately placed calibration image and recording four acoustic range measurements. A minimum of two measurement protocols determine the kinematics calibration-model of the ARID for a particular region: assuming the joint displacements are accurately measured, the calibration surface is planar, and the kinematic parameters do not vary rapidly in the region. No theoretical or practical limitations appear to contra-indicate the feasibility of the calibration method developed here.

Doty, Keith L.

1992-09-01

184

Rapid post-Pliocene crustal shortening in northern Tibet: Evidence from the Kumkuli Basin, Xinjiang Province, China  

NASA Astrophysics Data System (ADS)

The Altyn Tagh and Kunlun strike-slip faults dominate the modern deformation of northern Tibetan Plateau. We present shortening magnitudes and rates from the deformed Kumkuli Basin (~4000 m a.s.l.), located near the intersection of these faults ~80 km south of the Altyn Tagh and ~200 km northwest of the termination of the Kunlun fault. Quaternary vertical uplift rates of ~2.5-3 mm/yr occur beneath range front faults and folding of Eocene - Pliocene sediments record a total of >26% of post-Pliocene shortening. Basin infilling initiated in Eocene time and continued through Pliocene time with deposition of conglomerates to fluvial and lacustrine sediments. Notable Miocene gypsum beds indicate an arid environment and likely act as a zone of structural weakness in ongoing deformation. Paleocurrent directions indicate northward paleo-flow that sourced material from the Hoh Xil Basin located 150 km to the south of the Kumkuli Basin depocenter. Subsequent basin closure in Miocene time resulted from the uplift of the Quimen Tagh range to the north. Post-Pliocene deformation of basin sediments form a ~ 1 km high mountain range where a net of >12 km shortening is estimated from balanced cross sections. Folded Quaternary alluvial fan surfaces indicate that crustal shortening is ongoing. We combine new 36Cl cosmogenic radionuclide dating of depth profiles at the peaks of two folds with geomorphic reconstructions to estimate ~550 m of vertical fault motion since ~200 ka on subsurface thrust faults. We relate upper crustal shortening of the Kumkuli Bsain with left-lateral slip along the nearby Altyn Tagh fault and continued upward growth of the plateau in a region between major strike-slip faults and the rigid basement material of the Qaidam Basin. Although localized, Quaternary rates presented here are among the highest shortening rates documented in northern Tibet. Rapid upper crustal shortening at high elevations compounded with an addition of lower crustal material at depth may provide a mechanism by which northern Tibet reached elevations of >5000 m.

Yakovlev, P. V.; Clark, M. K.; Niemi, N. A.; Chang, H.; Yi, J.

2013-12-01

185

Increased storminess during MIS3 altered the late Quaternary basin-scale weathering, erosion, and deposition in Nahal Yael, hyperarid Negev, Israel  

NASA Astrophysics Data System (ADS)

A conceptual model for geomorphic response to Pleistocene to Holocene climate change (Bull and Schick, 1979, Quat. Res. 11: 153-171) was probably based on earlier observations in the southwestern US, but first applied to the hyperarid (<30 mm yr-1) Nahal Yael watershed, southern Negev desert. This influential model includes a chain of events following a climate change from semiarid late Pleistocene to hyperarid Holocene: reduced vegetation cover, increased yield of sediments from slopes, and accelerated aggradation of terraces and export of sediment from the basin to deposit an alluvial fan. The model is now >30 years old and during this time chronologic, paleoenvironmental and hydrogeomorphic research have all advanced but the discussions are still within the framework put forward then. The model is revaluated here by using data acquired in Nahal Yael over the 30 years since the original model was proposed. Recent studies indicate late Pleistocene climate was hyperarid and the transition from semiarid to hyperarid climates did not occur. The revised chronology reveals a 35-20 ka episode (probably already beginning at ~50 ka with lower rates) of accelerated weathering and sediment production and distinct talus accretion on slopes. Coeval with accretion on slopes, sediments were also transported and aggraded in fluvial terraces and alluvial fans, without noticeable lag time or a chain of discernable events. This intensified sediment production and delivery phase is unrelated to the Pleistocene-Holocene transition. The depositional landforms were rapidly incised during 20-18 ka; since this approximately LGM incision, sediment yield is from the storage in these depositional landforms and is not produced from bedrock in significant quantities. We propose that in such hyperarid environment, the main operators are individual extreme storms, and in this case specifically an episode of frequent storms and floods is the driver of change regardless the mean climatic conditions. It created a pulse of intense weathering due to numerous cycles of wetting and drying on slopes and sediment transport to fluvial terraces and alluvial fans; its impact continues all the way to the present. We suggest that even if aspects of the original conceptual model of Bull and Schick (1979) are correct, it has been applied too frequently, too generally, across very diverse arid climates and settings, and for too long in lieu of collecting new data at a full basin scale and testing the model.

Enzel, Y.; Amit, R.; Grodek, T.; Ayalon, A.; Lekach, J.; Porat, N.; Bierman, P. R.; Blum, J. D.; Erel, Y.

2012-12-01

186

Aridity threshold in controlling ecosystem nitrogen cycling in arid and semi-arid grasslands  

NASA Astrophysics Data System (ADS)

Higher aridity and more extreme rainfall events in drylands are predicted due to climate change. Yet, it is unclear how changing precipitation regimes may affect nitrogen (N) cycling, especially in areas with extremely high aridity. Here we investigate soil N isotopic values (?15N) along a 3,200?km aridity gradient and reveal a hump-shaped relationship between soil ?15N and aridity index (AI) with a threshold at AI=0.32. Variations of foliar ?15N, the abundance of nitrification and denitrification genes, and metabolic quotient along the gradient provide further evidence for the existence of this threshold. Data support the hypothesis that the increase of gaseous N loss is higher than the increase of net plant N accumulation with increasing AI below AI=0.32, while the opposite is favoured above this threshold. Our results highlight the importance of N-cycling microbes in extremely dry areas and suggest different controlling factors of N-cycling on either side of the threshold.

Wang, Chao; Wang, Xiaobo; Liu, Dongwei; Wu, Honghui; Lü, Xiaotao; Fang, Yunting; Cheng, Weixin; Luo, Wentao; Jiang, Ping; Shi, Jason; Yin, Huaqun; Zhou, Jizhong; Han, Xingguo; Bai, Edith

2014-09-01

187

Temporal change and suitability assessment of cropland in the Yellow River Basin during 1990–2005  

Microsoft Academic Search

Rapid landscape pattern change has taken place in many arid and semi-arid regions of China such as Yellow River Basin over the past decade. In this article, the physical suitability of cropland and its change were evaluated and analyzed by the combined use of satellite remote sensing, geographical information system, and landscape modeling technologies. The aim was to improve our

Siyuan Wang; Bing Zhang; Cunjian Yang; Yan Zhao; Hui Wang

2012-01-01

188

Temporal change and suitability assessment of cropland in the Yellow River Basin during 1990–2005  

Microsoft Academic Search

Rapid landscape pattern change has taken place in many arid and semi-arid regions of China such as Yellow River Basin over the past decade. In this article, the physical suitability of cropland and its change were evaluated and analyzed by the combined use of satellite remote sensing, geographical information system, and landscape modeling technologies. The aim was to improve our

Siyuan Wang; Bing Zhang; Cunjian Yang; Yan Zhao; Hui Wang

2011-01-01

189

Soil water balance of annual cropnative shrub systems in Senegal's Peanut Basin: The missing link  

E-print Network

Soil water balance of annual crop­native shrub systems in Senegal's Peanut Basin: The missing link agroecosystems Intercropping Semi-arid landscapes Groundwater uptake a b s t r a c t Shrubs in the Senegal Peanut

Selker, John

190

75 FR 62137 - Notice of Public Meeting; Proposed Alluvial Valley Floor Coal Exchange Public Interest Factors...  

Federal Register 2010, 2011, 2012, 2013, 2014

...Public Meeting; Proposed Alluvial Valley Floor Coal Exchange Public Interest Factors; Montana...to consider a proposal to exchange Federal coal deposits for Alluvial Valley Floor (AVF) fee coal pursuant to the Federal Land Policy and...

2010-10-07

191

Seasonal Solute Cycling by Evapotranspiration and Flooding in a Semi-Arid Delta: The Okavango Delta, Botswana  

NASA Astrophysics Data System (ADS)

The Okavango River in semi-arid northwestern Botswana flows into an endorheic basin where its distributaries are developed on a large alluvial fan to form the dispersal system of the Okavango Delta. The river and its distributaries support a large pristine wetland complex which they inundate annually for 4 to 6 months. The semi-arid climate subjects the river and tributaries to high rates of evapotranspiration causing about 96% of the inflow into Botswana to be lost within the Delta. As an endorheic basin, it is one of the few river systems for which solutes are cycled entirely within the terrestrial system. We hypothesized that the seasonal flood pulse initiated by discharge from tropical Angola and the dense vegetation and hot climate cause variable response to influx, the temporal and spatial distribution and the recycling of solutes. Over a period of two years, we made hourly measurements of water levels, water temperature and electrical conductivity at four select locations distributed spatially across the Okavango Delta. We used SolonistTM level, temperature and conductivity loggers to record the readings. One of our objective was to document changes in water level that reflect flooding and non flooding conditions, water temperature which reflect seasonality and electrical conductivity which approximated the aqueous solute behavior. A second objective was to assess the timing and behavior of the aqueous solutes on a seasonal and short term (daily) basis in order to elucidate the effects of flooding and vegetation on the solute behavior. The flood pulse which enters the delta in February-March is highly attenuated by the redistribution in the distributaries and flooding of the wetlands. Discharge decreases from upstream to downstream due to this and the effects of evapotranspiration. The seasons are clearly observed in the water temperatures with higher water temperatures in the wet summer season and lower temperatures in the dry winter season. Overall, the aqueous solute concentration in the delta is generally higher in the wet summer season due to evapotranspiration and lower in the dry winter season due to dilution by flood waters. The solute concentration increase from upstream to downstream due to the longer residence time of water in the delta and greater exposure to evapotranspiration with distance downstream. During the winter when flooding occurs, the aqueous solute concentration increase initially during the rising limb of the flood pulse before decreasing as continued flooding of the delta continues. We suggest that the initial increase in the aqueous solute concentration is due to dissolution of solutes that accumulated in the floodplains and numerous islands from evapotranspiration in the summer and flushing of the solutes into the river and distributaries. The effect of vegetative evapo-concentration is observed on a diel basis with markedly higher solute concentrations during the day and lower concentrations at night. We conclude that evapotranspiration has a pronounced effect in controlling the aqueous solute concentration and its downriver concentration. In addition, previously precipitated solutes on land are cycled to river water by the initial phase of flooding.

Atekwana, E. A.; Molwalefhe, L.

2012-12-01

192

Structure of Alluvial Valleys from 3-D Gravity Inversion: The Low Andarax Valley (Almería, Spain) Test Case  

NASA Astrophysics Data System (ADS)

This paper presents a gravimetric study (based on 382 gravimetric stations in an area about 32 km2) of a nearly flat basin: the Low Andarax valley. This alluvial basin, close to its river mouth, is located in the extreme south of the province of Almería and coincides with one of the existing depressions in the Betic Cordillera. The paper presents new methodological work to adapt a published inversion approach (GROWTH method) to the case of an alluvial valley (sedimentary stratification, with density increase downward). The adjusted 3D density model reveals several features in the topography of the discontinuity layers between the calcareous basement (2,700 kg/m3) and two sedimentary layers (2,400 and 2,250 kg/m3). We interpret several low density alignments as corresponding to SE faults striking about N140-145°E. Some detected basement elevations (such as the one, previously known by boreholes, in Viator village) are apparently connected with the fault pattern. The outcomes of this work are: (1) new gravimetric data, (2) new methodological options, and (3) the resulting structural conclusions.

Camacho, Antonio G.; Carmona, Enrique; García-Jerez, Antonio; Sánchez-Martos, Francisco; Prieto, Juan F.; Fernández, José; Luzón, Francisco

2014-08-01

193

Modern alluvial fan and deltaic sedimentation in a foreland tectonic setting: the Lower Mesopotamian Plain and the Arabian Gulf  

NASA Astrophysics Data System (ADS)

The Arabo-Persian Gulf, generally considered as a classical carbonate basin, in fact also includes important terrigenous systems whose nature and geometry are related closely to the tectonic framework. The Gulf is bordered along its northeastern periphery by an active alpine system which constitutes a major source of both siliceous and calcareous detritus. There are four types of terrigenous discharge which are classified according to their structural relationships. Numerous alluvial fans terminate ephemeral consequent streams draining the flanks of anticlines forming the external parts of the Zagros Mountain belt. Alluvial-fan deltas studied in detail in southeastern Iran terminate semi-permanent streams which flow along major synclinal axis. They are composed mainly of fine carbonate detritus, part of which accumulates as spectacular marine mud banks. Two major types of delta occur. Relatively small marine deltas, associated with permanent antecedent streams which cross the Zagros fold system, are scattered along the Persian shoreline. The other is the a major deltaic complex which is associated with the Tigris-Euphrates Rivers. This system has prograded along the main axis of the Gulf, the resulting Mesopotamian Plain filling at least half of the original basin which, in early Quaternary times, extended from Hormuz to Syria.

Baltzer, Frédéric; Purser, Bruce H.

1990-05-01

194

Sedimentology of a muddy alluvial deposit: Triassic Denwa Formation, India  

NASA Astrophysics Data System (ADS)

Triassic Upper Denwa Formation (˜ 380 m) in the Satpura Gondwana basin, central India is a mudstone-dominated fluvial succession that comprises isolated ribbon-shaped (2-5-m-thick) channel-fill bodies encased within fine-grained extra-channel deposits. Eight architectural elements are recognized, of which five belong to channel-fill deposits and the remaining three to extra-channel deposits. Majority of channel-fill deposits are characterized by sandy or muddy inclined heterolithic strata (IHS) that record limited lateral accretion of point bars or benches (constrained by cohesive banks) in mixed- to suspended-load sinuous channels. A few ribbon bodies are mud rich and attest to nearly stagnant conditions in partly abandoned channels. A few single- or multistorey ribbon bodies that are dominantly sandy and lack inclined strata represent deposits of straight, laterally stable channel. The smallest ribbon bodies (˜ 1 m thick) of calcirudite/calcarenite possibly represent deposits of secondary channels in the interfluves. Coexistence of channel-fill bodies of different dimension, lithology and internal organization in restricted stratigraphic intervals suggests an anabranching system having channels with different fill histories. The extra-channel deposits mainly comprise red mudstone (1-5 m thick) that indicates pervasive oxidation of overbank sediments in well-aerated and well-drained setting. Sporadically developed calcic vertisols suggest a hot, semi-arid climate during the Upper Denwa period. Sandy to heterolithic sheets (70 cm to 2 m thick) with sharp, planar basal surfaces are replete with features suggestive of unconfined sheet flow. Also at places there are indications of subaqueous emplacement of sands. These bodies with paleocurrent oblique to that of the channel-fills are interpreted as crevasse splay deposits. Tabular heterolithic bodies (3-5 m thick) are characterized by undulating basal surface, complex organization of sandstone lenses interwoven with heteroliths and red mudstone (in decimeter-scale) with desiccation cracks. Such tabular bodies are attributed to repetitive, sheet-like and poorly channelized splaying. Very thick (10 to 20 m) mudstones intervals are inexplicable in terms of overbank flooding only. Poorly developed pedogenic features in sandy to muddy heterolithic sheets and certain mudstone intervals and well-developed cumulative paleosols in surrounding mudstone highlights the contrast between rapidly emplaced splay deposits and slowly accumulated floodplain deposits. The Denwa channels are comparable with modern, low-gradient and low-energy anabranching river system in which the sediment load is dominantly fine-grained. The semi-arid climate possibly facilitated enhanced supply of fines to the Upper Denwa system. However, sediment partitioning and distribution in a particular channel was controlled by flow diversion to and from other channels in that anabranching system. Low flow strength with periodic flood events, high bank strength and a rate of sediment supply that slightly exceeded that of onward transport probably were important factors for the development of the Upper Denwa anabranching system.

Ghosh, Parthasarathi; Sarkar, Soumen; Maulik, Pradip

2006-09-01

195

Morphostructural characterization of the Charco basin and its surrounding areas in the Chihuahua segment of north Mexican Basin and Range Province  

NASA Astrophysics Data System (ADS)

The Chihuahua Basin and Range (CBR) is the eastern branch of the northern Mexican Basin and Range Province that, from a morphostructural point of view, presently is one amongst the lesser-known zones of the southern portion of the North America Basin and Range Province. The study area covers an approximately 800 km2-wide portion of the CBR and encompasses the fault-bounded Charco basin and its surrounding areas. The bedrock of the area pertains to the large siliceous-igneous province of the Sierra Madre Occidental and consists of volcanoclastic rocks including Oligocene dacite, rhyolite, rhyolitic tuffs, and polimitic conglomerates. The region is characterized by a series of NW-SE oriented valleys delimited by tilted monoclinal blocks bounded by high angle, SW-dipping, normal faults. Abrupt changes in elevation, alternating between narrow faulted mountain chains and flat arid valleys or basins are the main morphological elements of the area. The valleys correspond to structural grabens filled with Plio-Pleistocene continental sediments. These grabens are about 10 km wide, while the extensional fault system extend over a distance of more than 15 km. The mountain ranges are in most cases continuous over distances that range from 10 to 70 km including different branches of the extensional and transfer faults. The morphogenesis is mainly erosive in character: erosional landforms (such as rocky scarps, ridges, strath-terraces, erosional pediment, reverse slopes, landslide scar zones, litho-structural flat surfaces) dominate the landscape. In contrast, Quaternary depositional landforms are mainly concentrated within the flat valleys or basins. The Quaternary deposits consist of wide alluvial fans extending to the foot of the main ridges, fluvial and debris-slope deposits. The morphostructural characterization of the area integrated different methodologies, including: i) geomorphological and structural field analyses; ii) remote sensing and geo-morphometric investigations based on aerial photos and Digital Elevation Models (a 28x28 m DEM and high-resolution LIDAR dataset in key sites), and iii) geophysical investigations (high resolution reflection seismic profiling combined with refraction seismic tomography). The main outputs of this research are as follows: i) the Charco basin master-faults and their conjugate extensional system were geometrically characterized and their main associated landforms mapped and described; ii) the morphostratigraphic correlations amongst both deformed and tectonically unaffected Quaternary deposits revealed that the Charco basin master fault has been inactive over the Holocene; iii) the main extensional fault system is associated with conjugate faults, oriented approximately SSW-NNE, that segmented the Charco basin master faults and favored the deposition of the most recent piedmont fans along the eastern margin of the basin; iv) the local morphostructures had played a dominant influence on the Quaternary evolution of both drainage network and relief landforms.

Troiani, Francesco; Menichetti, Marco

2014-05-01

196

A review of the stratigraphy and sedimentary environments of the Karoo-aged basins of Southern Africa  

NASA Astrophysics Data System (ADS)

The Karoo Basin of South Africa was one of several contemporaneous intracratonic basins in southwestern Gondwana that became active in the Permo-Carboniferous (280 Ma) and continued to accumulate sediments until the earliest Jurassic, 100 million years later. At their maximum areal extent, during the early Permian, these basins covered some 4.5 million km 2. The present outcrop area of Karoo rocks in southern Africa is about 300 000 km 2 with a maximum thickness of some 8000 m. The economic importance of these sediments lies in the vast reserves of coal within the Ecca Group rocks of northern and eastern Transvaal and Natal, South Africa. Large reserves of sandstone-hosted uranium and molybdenum have been proven within the Beaufort Group rocks of the southern Karoo trough, although they are not mineable in the present market conditions. Palaeoenvironmental analysis of the major stratigraphic units of the Karoo succession in South Africa demonstrates the changes in depositional style caused by regional and localized tectonism within the basin. These depocentres were influenced by a progressive aridification of climate which was primarily caused by the northward drift of southwestern Gondwana out of a polar climate and accentuated by the meteoric drying effect of the surrounding land masses. Changing palaeoenvironments clearly influenced the rate and direction of vertebrate evolution in southern Gondwana as evidenced by the numerous reptile fossils, including dinosaurs, which are found in the Karoo strata of South Africa, Lesotho, Namibia and Zimbabwe. During the Late Carboniferous the southern part of Gondwana migrated over the South Pole resulting in a major ice sheet over the early Karoo basin and surrounding highlands. Glacial sedimentation in upland valleys and on the lowland shelf resulted in the Dwyka Formation at the base of the Karoo Sequence. After glaciation, an extensive shallow sea covered the gently subsiding shelf, fed by large volumes of meltwater. Marine clays and muds accumulated under cool climatic conditions (Lower Ecca Group) including the distinctive Mesosaurus-bearing carbonaceous shales of the Whitehill Formation. Subduction of the palaeo-Pacific plate reslted in an extensive chain of mountains which deformed and later truncated the southern rim of the main Karoo Basin. Material derived from these "Gondwanide" mountains as well as from the granitic uplands to the north-east, accumulated in large deltas that prograded into the Ecca sea (Upper Ecca Group). The relatively cool and humid climate promoted thick accumulations of peat on the fluvial and delta plains which now constitute the major coal reserves of southern Africa. As the prograding deltas coalesced, fluvio-lacustrine sediments of the Beaufort Group were laid down on broad gently subsiding alluvial plains. The climate by this time (Late Permian) had warmed to become semi-arid with highly seasonal rainfall. Vegetation alongside the meander belts and semi-permanent lakes supported a diverse reptilian fauna dominated by therapsids or "mammal-like reptiles". Pulses of uplift in the southern source areas combined with possible orographic effects resulted in the progadation of two coarse-grained alluvial fans into the central parts of the basin (Katberg Sandstone Member and Molteno Formation). In the upper Karoo Sequence, progressive aridification and tectonic deformation of the basin through the late Triassic and early Jurassic led to the accumulation, in four separate depositories, of "redbeds" which are interpreted as fluvial and flood-fan, playa and dune complexes (Elliot Formation). This eventually gave way to westerly wind-dominated sedimentation that choked the remaining depositories with fine-grained dune sand. The interdune areas were damp and occasionally flooded and provided a habitat for small dinosaurs and the earliest mammals. During this time (Early Jurassic), basinwide volcanic activity began as a precursor to the break-up of Gondwana in the late Jurassic and continued until the early Cretaceous. This

Smith, R. M. H.; Eriksson, P. G.; Botha, W. J.

1993-02-01

197

Valuing Water: variability and the Lake Eyre Basin, central Australia  

Microsoft Academic Search

‘Environmental values’ form an increasingly important component of natural resource management, but use of the term ‘value’ is dominated by a narrow and limiting utility-based definition. In this paper I consider theories of value and practices of valuing water in the arid and semi-arid Lake Eyre Basin, central Australia. While value is the subject of diverse meanings—both within a range

Leah M. Gibbs

2006-01-01

198

Late Quaternary alluvial fans at the eastern end of the San Bernardino Mountains, Southern California  

NASA Astrophysics Data System (ADS)

Alluvial fans at the eastern end of the San Bernardino Mountains in Southern California provide a record of climate modulated sediment transfer and erosion, and are deformed and displaced in places by active faults. Alluvial fans within two study areas, the Mission Creek and the Whitewater River drainages, were examined using geomorphic, sedimentological, and 10Be terrestrial cosmogenic nuclide (TCN) surface exposure methods to define the timing of alluvial fan formation and erosion, and to examine the role of climatic, tectonic and autocyclic processes. These alluvial fan complexes were studied because they are amongst the best-preserved successions of alluvial fans in southern California and they are located at the mouths of two of the largest drainages, Whitewater River and Mission Creek, in the San Bernardino Mountains and traverse major faults, the Mission Creek and Banning. The alluvial fans comprise bouldery debris deposits that represent deposition dominated by flash flood and debris flow events. TCN surface exposure dating indicates that abandonment/incision of alluvial fan surfaces date to early in the Last Glacial or more likely the penultimate glacial cycle, to marine isotope stage (MIS) 4, and to the Holocene. The lack of alluvial fan ages during the latter part of the Last Glacial (MIS 2 and 3) suggests that there has been little alluvial fan lobe deposition/incision during that time. This is similar to findings for many other alluvial fans throughout the American Southwest, and supports the view that there is a strong climatic control on alluvial fan formation throughout this region. Furthermore, the oldest alluvial fan surfaces in the Mission Creek region are beheaded by the Whitewater River drainage, showing that the oldest alluvial fans in the Mission Creek region underwent significant capture by the Whitewater River drainage. This shows the autocyclic controls are also important on alluvial fan evolution in this region; but the importance of these processes to alluvial fan development in other regions of the American Southwest needs to be more fully assessed. The alluvial fans in the Mission Creek area traverse the Mission Creek fault, but are not deformed by it, which suggests that there may have been little if any movement along this fault since at least MIS 4. In contrast, alluvial fans in the Whitewater River study are displaced by active faults highlighting the influence of tectonism on alluvial fan development in this region. In addition to illustrating the importance of climatic controls on the development of alluvial fans in the American Southwest, a classic region for alluvial fan studies, this study illustrates the complex mixture of autocyclic and allocyclic factors that force alluvial fan development in tectonically active settings.

Owen, Lewis A.; Clemmens, Samuel J.; Finkel, Robert C.; Gray, Harrison

2014-03-01

199

The Vallesian mammal succession in the Vallès-Penedès basin (northeast Spain): Paleomagnetic calibration and correlation with global events  

Microsoft Academic Search

The integrated lithostratigraphic, biostratigraphic and magnetostratigraphic study of new and classical alluvial fan sequences in the Vallès-Penedès Basin (northeast Spain, Western Mediterranean) enabled a considerable refinement of the Vallesian mammalian succession in this basin and its correlation with the Magnetic Polarity Time Scale. Up to 12 new sections were logged and sampled in a search of mammal remains and a

Jorge Agustí; Lluís Cabrera; Miguel Garces; Josep M. Parés

1997-01-01

200

HYDRAULIC ANALYSIS OF BASEFLOW AND BANK STORAGE IN ALLUVIAL STREAMS  

EPA Science Inventory

This paper presents analytical solutions, which describe the effect of time-variable net recharge (net accretion to water table) and bank storage in alluvial aquifers on the sustenance of stream flows during storm and inter-storm events. The solutions relate the stream discharge,...

201

On Earthquake Ground Motion and Structural Response in Alluvial Valleys  

E-print Network

On Earthquake Ground Motion and Structural Response in Alluvial Valleys By Jacobo Bielak 1 , Member amplification and structural dam­ age due to local site conditions in sedimentary valleys during earthquakes the 1988 Armenia Earthquake. A more realistic two­dimensional finite element analysis is performed herein

Shewchuk, Jonathan

202

Intra-meander hyporheic flow in alluvial rivers  

Microsoft Academic Search

Several geomorphological fluvial features are able to induce hyporheic exchange between the rivers and the alluvial sediments. However, while the small-scale exchange induced by bed forms has been thoroughly investigated, the role of the larger features remains poorly understood. Here, we focus on the hyporheic flows driven by the channel sinuosity in the intrameander zone. A physically based model is

Roberto Revelli; Fulvio Boano; Carlo Camporeale; Luca Ridolfi

2008-01-01

203

Fluvial geomorphic features of the Lower Mississippi alluvial valley  

Microsoft Academic Search

The Lower Mississippi Valley (LMV) has been one of the most intensively studied alluvial valleys in the world in terms of it's geological and geomorphic framework and history. A brief outline of the history of the major geological and geomorphological investigations of the LMV is provided. The results of these investigations are discussed in terms of the fluvial geomorphic framework

Lawson M. Smith

1996-01-01

204

Germination and seed water status of four grasses on moss-dominated biological soil crusts from arid lands  

Microsoft Academic Search

Biological soil crusts dominated by drought-tolerant mosses are commonly found through arid and semiarid steppe communities of the northern Great Basin of North America. We conducted growth chamber experiments to investigate the effects of these crusts on the germination of four grasses: Festuca idahoensis, Festuca ovina, Elymus wawawaiensis and Bromus tectorum. For each of these species, we recorded germination time

Marcelo D. Serpe; Jeanne M. Orm; Tara Barkes; Roger Rosentreter

2006-01-01

205

Nearshore and alluvial facies in the Sant Llorenç del Munt depositional system: recognition and development  

NASA Astrophysics Data System (ADS)

The Eocene Sant Llorenç del Munt fan-delta complex forms a part of the coarse-grained foreland basin fill of the southeastern margin of the Ebro Basin. It was sourced from the rising Catalan Coastal Range in the SE and shows an overall northwesterly progradation during a time period of approximately six million years. Coarse clastic deposits (coarse sands and gravels) dominated this fan delta, whereas finer-grained sands, silts, and muds were deposited laterally off active sedimentation sites or in the more marine area. Depositional processes were clearly influenced by the high sediment input, giving a dominance of sediment gravity flow deposits. The sediments studied have been grouped into four distinct facies belts including coastal plain, proximal fan-delta front, distal fan-delta front and fan-delta slope sediments, respectively. The facies belts combine to form the nearshore and coastal alluvial reaches of the fan-delta system, developed during a transgressive phase lasting some 50,000 years.

Rasmussen, H.

2000-12-01

206

Integrating hydrologic modeling and land use projections for evaluation of hydrologic response and regional water supply impacts in semi-arid environments  

Microsoft Academic Search

Semi-arid environments are generally more sensitive to urbanization than humid regions in terms of both hydrologic modifications\\u000a and water resources sustainability. The current study integrates hydrologic modeling and land use projections to predict long-term\\u000a impacts of urbanization on hydrologic behavior and water supply in semi-arid regions. The study focuses on the Upper Santa\\u000a Clara River basin in northern Los Angeles

Minxue HeTerri; Terri S. Hogue

207

Implications of deep drainage through saline clay for groundwater recharge and sustainable cropping in a semi-arid catchment, Australia  

NASA Astrophysics Data System (ADS)

The magnitude and timing of deep drainage and salt leaching through clay soils is a critical issue for dryland agriculture in semi-arid regions (<500 mm yr-1 rainfall, potential evapotranspiration >2000 mm yr-1) such as parts of Australia's Murray-Darling Basin (MDB). In this rare study, hydrogeological measurements and estimations of the historic water balance of crops grown on overlying Grey Vertosols were combined to estimate the contribution of deep drainage below crop roots to recharge and salinization of shallow groundwater. Soil sampling at two sites on the alluvial flood plain of the Lower Namoi catchment revealed significant peaks in chloride concentrations at 0.8-1.2 m depth under perennial vegetation and at 2.0-2.5 m depth under continuous cropping indicating deep drainage and salt leaching since conversion to cropping. Total salt loads of 91-229 t ha-1 NaCl equivalent were measured for perennial vegetation and cropping, with salinity to ? 10 m depth that was not detected by shallow soil surveys. Groundwater salinity varied spatially from 910 to 2430 mS m-1 at 21 to 37 m depth (N = 5), whereas deeper groundwater was less saline (290 mS m-1) with use restricted to livestock and rural domestic supplies in this area. The Agricultural Production Systems Simulator (APSIM) software package predicted deep drainage of 3.3-9.5 mm yr-1 (0.7-2.1% rainfall) based on site records of grain yields, rainfall, salt leaching and soil properties. Predicted deep drainage was highly episodic, dependent on rainfall and antecedent soil water content, and over a 39 yr period was restricted mainly to the record wet winter of 1998. During the study period, groundwater levels were unresponsive to major rainfall events (70 and 190 mm total), and most piezometers at about 18 m depth remained dry. In this area, at this time, recharge appears to be negligible due to low rainfall and large potential evapotranspiration, transient hydrological conditions after changes in land use and a thick clay dominated vadose zone. This is in contrast to regional groundwater modelling that assumes annual recharge of 0.5% of rainfall. Importantly, it was found that leaching from episodic deep drainage could not cause discharge of saline groundwater in the area, since the water table was several meters below the incised river bed.

Timms, W. A.; Young, R. R.; Huth, N.

2012-04-01

208

Implications of deep drainage through saline clay for groundwater recharge and sustainable cropping in a semi-arid catchment, Australia  

NASA Astrophysics Data System (ADS)

The magnitude and timing of deep drainage and salt leaching through clay soils is a critical issue for dryland agriculture in semi-arid regions (<500 mm yr-1 rainfall), such as parts of Australia's Murray-Darling Basin (MDB). In this unique study, hydrogeological measurements and estimations of the historic water balance of crops grown on overlying Grey Vertosols were combined to estimate the contribution of deep drainage below crop roots to recharge and salinization of shallow groundwater. Soil sampling at two sites on the alluvial flood plain of the Lower Namoi catchment revealed significant peaks in chloride concentrations at 0.8-1.2 m depth under perennial vegetation and at 2.0-2.5 m depth under continuous cropping indicating deep drainage and salt leaching since conversion to cropping. Total salt loads of 91-229 t ha-1 NaCl equivalent were measured for perennial vegetation and cropping, with salinity to ?10 m depth that is not detected by shallow soil surveys. Groundwater salinity varied spatially from 910 to 2430 mS m-1 at 21 to 37 m depth (N = 5), whereas deeper groundwater was less saline (290 mS m-1) with use restricted to livestock and rural domestic supplies in this area. The Agricultural Production Systems Simulator (APSIM) software package predicted deep drainage of 3.3-9.5 mm yr-1 (0.7-2.1% rainfall) based on site records of grain yields, rainfall, salt leaching and soil properties. Predicted deep drainage was highly episodic, dependent on rainfall and antecedent, and over a 39 yr period was restricted mainly to the record wet winter of 1998. During the study period, groundwater levels were unresponsive to major rainfall events (70 and 190 mm total), and most piezometers at about 18 m depth remained dry. In this area, at this time, recharge negligible due to low rainfall and large potential evapotranspiration, transient hydrological conditionsafter changes in land use and a thick clay dominated vadose zone. This is in contrast to regional groundwater modelling that assumes annual recharge of 0.5% of rainfall. Importantly, it was found that leaching from episodic deep drainage could not cause discharge of saline groundwater in the area, since the water table was several meters below the incised river bed.

Timms, W. A.; Young, R. R.; Huth, N.

2011-11-01

209

A successful borehole drilled by cryogenic drilling in an arid, unconsolidated soil with boulders  

SciTech Connect

An 80 foot deep borehole was drilled using a novel cryogenic drilling method. The freeze while drilling technique stabilizes the borehole wall while drilling by using conventional air rotary methods but with low temperature nitrogen gas (as cold as {minus}196 C) as the drilling fluid. The location of the field test was a semi-arid alluvial unconsolidated sedimentary formation at the Aerojet, Inc. site in Rancho Cordova, California. The geology was a sandy soil matrix containing cobbles and boulders. The test goal was to drill to 100 feet (30 m), but the test was terminated at 80 feet due to a failure of the swivel shaft and drill bit resulting from the very rough drilling conditions. No safety, technical, or operational problems were encountered that could prevent cryogenic drilling from becoming a standard technique for drilling in unstable near-surface formations.

Cavagnaro, P.; Simon, R.D.; Cooper, G.A. [Univ. of California, Berkeley, CA (United States). Dept. of Materials Science and Mineral Engineering

1997-07-01

210

Bahia Adair and vicinity, Sonora: modern siliciclastic-dominated arid macrotidal coastline  

SciTech Connect

The northwestern Sonoran coastline, in the vicinity of Bahia Adair, combines several important geologic features. The arid landward environments are dominated by the dunes of the Gran Desierto and the surrounding alluvial fans and ephemeral streams. The Colorado River, whose delta lies to the northwest, has been an important source of sediment until very recently. The high tidal energy of the region has profoundly influenced the distribution and geometries of coastal and shallow-marine sand bodies, and the active tectonic setting has also played a role. The Cerro Prieto splay of the San Andreas fault system has been responsible for local uplift and downwarp and resulting transgression and regression. The intertidal and supratidal zones are dominated by sand and constitute a sand-body type that has been seldom considered by petroleum explorationists or other students of ancient sand bodies, and the associated evaporites are rather different from those described from the superficially analogous Persian Gulf sabkhas.

Lock, B.E.; Sinitiere, S.M.; Williams, L.J.

1989-03-01

211

GEOG 400 Spring 2013 ARID LANDS GEOMORPHOLOGY  

E-print Network

Outline# 1 Course and Historical Overview/Global Deserts 2 Causes/Climates/Soils and Ecosystems of Arid 12 Arid Lands and Climate Change 13 Desertification and Land Degradation 14 Environmental Issues Environments (2008), Wiley-Blackwell. The book is listed at $80 in Amazon and used copies start at $45

212

Kinematic analysis of the ARID manipulator  

NASA Technical Reports Server (NTRS)

The kinematic structure of the ARID manipulator lends itself to simple forward and inverse kinematics analysis. The purpose of this paper is to fully document and verify an existing analysis. The symbolic software package MATHEMATICA was used to produce and verify the equations presented here. In the analysis to follow, the standard Devenit-Hartenberg kinematic parameters of the ARID were employed.

Doty, Keith L

1992-01-01

213

Landscape evolution in the Yellow River Basin using satellite remote sensing and GIS during the past decade  

Microsoft Academic Search

Over the past decade, rapid landscape pattern change has taken place in many arid and semi-arid regions of China, such as the Yellow River Basin. In this paper, landscape evolution was investigated by the combined use of satellite remote sensing, geographic information system (GIS) and landscape modelling technologies. The aim was to improve our understanding of landscape changes so that

Siyuan Wang; Chibiao Ding; Jingshi Liu

2009-01-01

214

Competing Interests and Concerns in the Rio Grande Basin: Mountain Hydrology, Desert Ecology, Climate Change, and Population Growth  

Microsoft Academic Search

In the mountainous American Southwest, the Rio Grande basin is a prime example of how conflicts, misconceptions, and competition regarding water can arise in arid and semi-arid catchments. Much of the Rio Grande runoff originates from snow fields in the San Juan Mountains of southern Colorado and the Sangre De Cristo Mountains of northern New Mexico, far from population centers.

A. Rango

2004-01-01

215

Rainbow Basin, CA mapping project  

NSDL National Science Digital Library

Rainbow Basin is just north of Barstow, CA, and is an excellent badlands-style exposure of the Barstow syncline in the Miocene Barstow Formation. In the first mapping class, their assignment is to map the basic geology of the basin, using a couple of distinctive marker beds within the Barstow Formation. Several faults postdate the fold, and three different ages of alluvial deposits occur within the basin. We camp in the nearby Owl Canyon campground, and spend three days in the field. More time could be spent with an introductory class, but three suffices to get most of the basin on the map. They are charged with writing up descriptions of the rock units they encounter. From the field map, students transfer information to an office copy, add a map explanation, and draw a cross-section through the map area. Mapping is done on a topographic map, specifically developed for the basin, with 10-foot contour intervals. This is a proprietary map, so permission is needed for its use.

Joan Fryxell

216

Detectability of minerals on desert alluvial fans using reflectance spectra  

NASA Technical Reports Server (NTRS)

The visible and near-infrared reflectance spectra of soil samples collected from desert alluvial and colluvial surfaces in the Cuprite mining district, Nevada, were analyzed. These surfaces are downslope from hydrothermally altered volcanic rocks that contain spectrally characteristic minerals such as alunite and kaolinite. Coarse fractions of the soils on the alluvial fans are mineralogically variable and express the upslope lithologies; fine fractions are remarkably similar mineralogically and spectrally in all samples because of dilution of local mineral components by regionally derived windblown dust. Theoretical models for spectral mixing and for particle-size effects were used to model the observed spectral variations. Diagnostic mineral absorption bands in the spectra of fan materials were enhanced by computationally removing the spectrum of the homogeneous fine-soil component. Results show that spectral mixing models are useful for analyzing data with high spectral resolution obtained by field and aircraft spectrometers.

Shipman, Hugh; Adams, John B.

1987-01-01

217

A model of channel response in disturbed alluvial channels  

USGS Publications Warehouse

Dredging and straightening of alluvial channels between 1959 and 1978 in West Tennessee caused a series of morphologic changes along modified reaches and tributary streams. Degradation occurred for 10 to 15 years at sites upstream of the area of maximum disturbance and lowered bed-levels by as much as 6.1 m. Following degradation, reaches upstream of the area of maximum disturbance experienced a secondary aggradation phase in response to excessive incision and gradient reduction. -from Author

Simon, A.

1989-01-01

218

Semi-Arid Landscapes: The Canary in the Climate-Change Coalmine (Invited)  

NASA Astrophysics Data System (ADS)

The balance between precipitation as a driving force of sediment transport (via hillslope erosional processes) or a resisting force (via increases in vegetation cover) is reflected by the landforms and denudation rates in semi-arid landscapes. While exact values vary, studies examining the relationship between land surface lowering and mean annual precipitation show a ';sweet spot' of peak denudation rates for semi-arid landscapes receiving ~300-500 mm precipitation/year. Ongoing and future climate change necessitates the investigation of how landscapes may respond as they move towards or away from this erosional threshold; semi-arid landscapes on the edge of ecohydrologic thresholds (e.g. treelines) may experience dramatic environmental changes as ongoing and future climate change alters ecosystems. Semi-arid landscapes are the equivalent to canaries in a coal-mine, and studying them advances understanding of how other sensitive landscapes may respond to climate change. Landforms, however, are a product of thousands to millions of years of climatic forcing. Direct measurement of both short and long-term erosion rates is complicated, and observations of modern erosional processes may not reflect the past. Over 10 years of environmental data collected in the heavily instrumented Dry Creek Experimental Watershed (DCEW) outside Boise, Idaho facilitates 2nd order analysis of climate-driven environmental variability across a large area (27 km2). Multi-scaled analyses relate runoff production from pedons to catchments, and erosion rates and processes from hillslopes to landforms, while prior mapping results (Poulos et al, 2012) allow application of results to similar semi-arid montane landscapes. Preliminary data reveal intriguing, but counterintuitive, feedbacks among soil properties, hillslope hydrology, ecology, and drainage development. Despite steeper slope angles, north-facing slopes have thicker soils than south-facing slopes, suggesting slower erosion rates. This conflicts with theories of hillslope processes which predict that erosion rates increase and soil thicknesses decrease with increasing slope angles. Could future increases in temperatures and decreased vegetation push north-facing slopes beyond a geomorphic tipping point, where their soils and drainages erode like south-facing slopes? Also, shallower soils and reduced plant cover on south-facing slopes appear to limit soil water storage and evapotranspiration, culminating in increased runoff and streamflow from these relatively drier ecosystems. What impact do these pedon- and hillslope-scale differences in runoff have on catchment-scale drainage erosion, incision and expansion? Finally, while landforms and erosion rates reflect, to some degree, the annual to centennial-scale climate conditions and precipitation events, episodic events such as wildfires exert a major control on erosion rates. Alluvial fans act as natural (albeit a bit leaky) sediment traps for hillslope erosion from 1st order drainage systems, while charcoal fragments in alluvial fan stratigraphic sequences provide both evidence of fire, and (through 14C dating) a means to estimate erosion rates. Ongoing fire studies in the DCEW, combined with surveys of alluvial fan sediment volumes, will reveal 1) the contribution of fire events to overall erosion rates, 2) variability in erosion rates between north and south facing slopes and 3) changes in Holocene fire activity with changes in climate.

Pierce, J. L.; Poulos, M. J.

2013-12-01

219

Uranium in framboidal pyrite from a naturally bioreduced alluvial sediment.  

PubMed

Samples of a naturally bioreduced, U-contaminated alluvial sediment were characterized with various microscopic and spectroscopic techniques and wet chemical extraction methods. The objective was to investigate U association and interaction with minerals of the sediment. Bioreduced sediment comprises approximately 10% of an alluvial aquifer adjacent to the Colorado River, in Rifle, CO, that was the site of a former U milling operation. Past and ongoing research has demonstrated that bioreduced sediment is elevated in solid-associated U, total organic carbon, and acid-volatile sulfide, and depleted in bioavailable Fe(III) confirming that sulfate and Fe(III) reduction have occurred naturally in the sediment. SEM/EDS analyses demonstrated that framboidal pyrites (FeS(2)) of different sizes ( approximately 10-20 microm in diameter), and of various microcrystal morphology, degree of surface weathering, and internal porosity were abundant in the <53 microm fraction (silt + clay) of the sediment and absent in adjacent sediments that were not bioreduced. SEM-EMPA, XRF, EXAFS, and XANES measurements showed elevated U was present in framboidal pyrite as both U(VI) and U(IV). This result indicates that U may be sequestered in situ under conditions of microbially driven sulfate reduction and pyrite formation. Conversely, such pyrites in alluvial sediments provide a long-term source of U under conditions of slow oxidation, contributing to the persistence of U of some U plumes. These results may also help in developing remedial measures for U-contaminated aquifers. PMID:20028047

Qafoku, Nikolla P; Kukkadapu, Ravi K; McKinley, James P; Arey, Bruce W; Kelly, Shelly D; Wang, Chongmin; Resch, Charles T; Long, Philip E

2009-11-15

220

ARID relative calibration experimental data and analysis  

NASA Technical Reports Server (NTRS)

Several experiments measure the orientation error of the ARID end-frame as well as linear displacements in the Orbiter's y- and z-axes. In each experiment the position of the ARID on the trolley is fixed and the manipulator extends and retracts along the Orbiter's y-axis. A sensor platform consisting of four sonars arranged in a '+' pattern measures the platform pitch about the Orbiter's y-axis (angle b) and yaw about the Orbiter's x-axis (angle alpha). Corroborating measurements of the yaw error were performed using a carpenter's level to keep the platform perpendicular to the gravity vector at each ARID pose being measured.

Doty, Keith L

1992-01-01

221

Desert Pavement Process and Form: Modes and Scales of Landscape Stability and Instability in Arid Regions  

NASA Astrophysics Data System (ADS)

Desert pavements are recognized in arid landscapes around the world, developing via diminution of constructional/depositional landform relief and creating a 1-2 stone thick armor over a "stone free" layer. Surface exposure dating demonstrates that clasts forming the desert pavements are maintained at the land surface over hundreds of thousands of years, as aeolian fines are deposited on the land surface, transported into the underlying parent material and incorporated into accretionary soil horizons (e.g., the stone free or vesicular [Av] horizon). This surface armor provides long-term stability over extensive regions of the landscape. Over shorter time periods and at the landform-element scale, dynamic surficial processes (i.e., weathering, runoff) continue to modify the pavement form. Clast size reduction in comparison to underlying parent material, along with armoring and packing of clasts in pavements contribute to their persistence, and studies of crack orientations in pavement clasts indicate physical weathering and diminution of particle size are driven by diurnal solar insolation. Over geologic time, cracks form and propagate from tensile stresses related to temporal and spatial gradients in temperature that evolve and rotate in alignment with the sun's rays. Observed multimodal nature of crack orientations appear related to seasonally varying, latitude-dependent temperature fields resulting from solar angle and weather conditions. Surface properties and their underlying soil profiles vary across pavement surfaces, forming a landscape mosaic and controlling surface hydrology, ecosystem function and the ultimate life-cycle of arid landscapes. In areas of well-developed pavements, surface infiltration and soluble salt concentrations indicate that saturated hydraulic conductivity of Av horizons decline on progressively older alluvial fan surfaces. Field observations and measurements from well-developed desert pavement surfaces landforms also yield significantly lower infiltration rates, enhanced rates of overland flow characterized by high water:sediment ratios and reduced production of desert ecosystems. Consequently, regionally extensive pavement and significantly decreased infiltration over geologic time have resulted in widespread overland flow, elaborate drainage networks on alluvial and eolian-mantled bedrock landscapes, and channel incision and regional dissection of the pavement-mantled landforms. However, these once stable landscapes become progressively unstable with time, serving as sediment source areas for younger alluvial deposits (i.e., geologic life-cycle). Thus, regional dissection (instability) of these desert landscapes can be influenced by the intrinsic properties of pavement-mantled landscapes and not necessarily to external forces of climate change and tectonics.

Wells, Stephen G.; McFadden, Leslie D.; McDonald, Eric V.; Eppes, Martha C.; Young, Michael H.; Wood, Yvonne A.

2014-05-01

222

An integrated modelling and remote sensing approach for hydrological study in arid and semi-arid regions: the SUDMED Program  

E-print Network

-arid, land-surface interactions, remote sensing, disaggregation, aggregation, snow processes, surface1 An integrated modelling and remote sensing approach for hydrological study in arid and semi resources in arid and semi-arid regions. In this context, remote sensing data have been widely used

Paris-Sud XI, Université de

223

Frequency and Spatial Characteristics of Droughts in the Conchos River Basin, Mexico  

Microsoft Academic Search

The temporal and spatial characteristics of droughts are investigated to provide a framework for sustainable water resources management in a semi-arid region. Using the Palmer Drought Severity Index (PDSI) as an indicator of drought severity, the characteristics of droughts are examined in the Conchos River Basin in Mexico. This basin is important to both the United States and Mexico, because

Tae-Woong Kim; Juan B. Valdés; Javier Aparicio

2002-01-01

224

The Late Quaternary biogeographic histories of some Great Basin mammals (western USA)  

Microsoft Academic Search

The Great Basin of arid western North America provides one of the most detailed late Pleistocene and Holocene mammal records available for any part of the world, though the record is by far strongest for small mammals. Of the 35 genera of now-extinct North American Pleistocene mammals, 19 are known to have occurred in the Great Basin, a list that

Donald K. Grayson

2006-01-01

225

Characterization of the hydrological functioning of the Niger basin using the ISBA-TRIP model  

Microsoft Academic Search

During the 70s and 80s, West Africa has faced extreme climate variations with extended extreme drought conditions. Of particular importance is the Niger basin, since it traverses a large part of the Sahel and is thus a critical source of water in this semi arid region. However, the understanding of the hydrological processes over this basin is currently limited by

V. Pedinotti; A. Boone; B. Decharme; J. F. Crétaux; N. Mognard; G. Panthou; F. Papa

2011-01-01

226

Using major ions and ?15N-NO3(-) to identify nitrate sources and fate in an alluvial aquifer of the Baiyangdian lake watershed, North China Plain.  

PubMed

In semi-arid regions, most human activities occur in alluvial fan areas; however, NO3(-) pollution has greatly threatened the shallow groundwater quality. In this paper, ?(15)N-NO3(-) and multi-tracers were used to identify the origin and fate of NO3(-) in groundwater of the Baiyangdian lake watershed, North China Plain. The investigation was conducted in two typical regions: one is the agricultural area located in the upstream of the watershed and another is the region influenced by urban wastewater in the downstream of the watershed. Results indicate that the high NO3(-) concentrations of the upstream shallow groundwater were sourced from fertilizer and manure or sewage leakage, whilst the mixture and denitrification caused the decrease in the NO3(-) concentration along the flow path of the groundwater. In the downstream, industrial and domestic effluent has a great impact on groundwater quality. The contaminated rivers contributed from 45% to 76% of the total recharge to the groundwater within a distance of 40 m from the river. The mixture fraction of the wastewater declined with the increasing distance away from the river. However, groundwater with NO3(-) concentrations larger than 20 mg l(-1) was only distributed in areas near to the polluted river or the sewage irrigation area. It is revealed that the frontier and depression regions of an alluvial fan in a lake watershed with abundant organics, silt and clay sediments have suitable conditions for denitrification in the downstream. PMID:23743546

Wang, Shiqin; Tang, Changyuan; Song, Xianfang; Yuan, Ruiqiang; Wang, Qinxue; Zhang, Yinghua

2013-07-01

227

[Effects of cadmium stress on the microbial biodiversity in purple soil and alluvial soil potted with a poplar (Populus deltoides x Populus nigra)].  

PubMed

Effects of current Cd contamination levels on microbial biodiversity were studied under the typical Cd contaminated soils in the Yangtze Basin. Purple soil and alluvial soil potted with a poplar (Populus deltoides x Populus nigra) were selected, and the culturable soil microbial amounts by flat method, microbial biomass and bacterial community structure by PCR-DGGE were investigated. Cd supplies significantly increased the culturable amounts of bacteria and actinomyces in purple soil, but decreased the culturable amounts of fungi and the content of microbial biomass N. Fingerprint of DGGE also showed that bacterial community structure have obviously changed under different Cd supplies. In contrast, the lower Cd supplies slightly increased the culturable amounts of bacteria and fungi in alluvial soil, but higher Cd supply treatment decreased the culturable amounts of bacteria, actinomyces and fungi, and the content of microbial biomass N. However, only a slight change was observed under different Cd supplies by DGGE fingerprint. Additionally, there were few effects of Cd supplies on the content of microbial biomass C in both purple soil and alluvial soil. The results provided basic data to understand the effects of present Cd contamination levels on soil microbial characteristics. PMID:21922843

Wang, Ao; Wu, Fu-Zhong; Yang, Wan-Qin; Zhou, Li-Qiang; Wang, Xu-Xi; Han, Yu

2011-07-01

228

Facies analysis and basin architecture of the Neogene Subandean synorogenic wedge, southern Bolivia  

NASA Astrophysics Data System (ADS)

Foreland sedimentation in the Subandean Zone of south-central Bolivia spans from the Upper Oligocene to present. It records sediment dispersal patterns in an initially distal and later proximal retroarc foreland basin, and thereby contains stratigraphic information on the tectonic evolution of the adjacent Andean fold-thrust belt. Within the Neogene orogenic wedge individual siliciclastic-dominated depositional systems formed ahead of an eastward-propagating deformation regime. We defined, described, and interpreted eight architectural elements and 24 lithofacies from 15 outcrop locations representing the Neogene foreland basin in the Subandean Zone and the Chaco Plain. These are combined to interpret depositional settings. The up to 7.5 km-thick Neogene wedge is subdivided in five stratigraphic units on the basis of facies associations and overall architecture: (1) The basal, Oligocene-Miocene, up to 250 m-thick Petaca Formation consists dominantly of calcrete, reworked conglomeratic pedogenic clasts, and fluvial sandstone and mudstone. This unit is interpreted to represent extensive pedogenesis under an arid to semiarid climate with subordinate braided fluvial processes. (2) The overlying, Upper Miocene, up to 350 m thick Yecua Formation records numerous small-scale transgressive-regressive cycles of marginal marine, tidal, and shoreline facies of sandstone, ooid limestones, and varicoloured mudstone. (3) The Upper Miocene, up to 4500 m-thick Tariquia Formation principally consists of sandstone with interbedded sandstone-mudstone couplets representing frequent crevassing in anastomosing streams with an upsection-increasing degree of connectedness. (4) The up to 1500 m-thick Lower Pliocene Guandacay Formation represents braided streams and consists principally of granule to cobble conglomerate interbedded with sandstone and sandy mudstone. (5) The Upper Pliocene, up to 2000 m-thick Emborozu Formation consists predominantly of alluvial-fan-deposited cobble to boulder conglomerate interbedded with sandstone and sandy mudstone. The coarsening- and thickening-upward pattern and eastward progradation, coupled with the variable proportions of overbank facies, channel size, and degree of channel abandonment, in the Tariquia, Guandacay, and Emborozu Formations reflect a distal through proximal fluvial megafan environment. This long-lived megafan grew by high sedimentation rates and a northeast-through-southeast radial paleoflow pattern on large, coarse-grained sediment lobes. The marked overall upsection change in pattern and depositional styles indicate fluctuations in accommodation space and sediment supply, regulated by basin subsidence, and are attributable to Andean tectonics and climatic controls.

Eji Uba, Cornelius; Heubeck, Christoph; Hulka, Carola

2005-10-01

229

Global and continental changes of arid areas using the FAO Aridity Index over the periods 1951-1980 and 1981-2010  

NASA Astrophysics Data System (ADS)

An increase in arid areas and progressing land degradation are two of the main consequences of global climate change. In the 2nd edition of the World Atlas of Desertification (WAD), published by the United Nation Environment Program (UNEP) in 1997, a global aridity map was presented. This map was based on the Food and Agriculture Organization (FAO) Aridity Index (AI) that takes into account the annual ratio between precipitation (RR) and Potential Evapo-Transpiration (PET). According to the long-term mean value of this ratio, climate is therefore classified in hyper-arid (<0.05), arid (0.05-0.2), semi-arid (0.2-0.5), dry sub-humid (0.5-0.65), and humid (>0.65); a special case are cold climates, which occur if the mean annual PET is below 400 mm. In the framework of the 3rd edition of the WAD, we computed new global aridity maps to improve and update the old version that was based on a single dataset (CRU dataset, Climate Research Unit of University of East Anglia) related to the 1951-80 period only. We computed the AI on two different time intervals (1951-80 and 1981-2010) in order to account for shifts in classes between the two periods and we used two different datasets: PET from CRU (version 3.2), and precipitation from the global 0.5?x0.5? gridded monthly precipitation of the Global Precipitation Climatology Center (GPCC) of the Deutscher Wetterdienst (DWD). We used the GPCC Full Data Reanalysis Version 6.0, which showed a high reliability during many quality checks and is based on more stations than the CRU's precipitation counterpart. The results show that the "arid areas" (i.e. AI <0.5) globally increased from 28.4% to 29.6% and in Northern Hemisphere the cold climate areas decreased from 26.6% to 25.4%. Comparing the aridity maps of the two periods, the areas which most remarkably moved to lower AI values ("more arid" conditions) are: Canada, Brazil, the Mediterranean Region, Eastern Europe, almost all of Africa, the Middle East, Eastern China, Borneo, and Australia. At regional or country level, a shift of one class towards a "more arid" class can be found in Alaska (U.S.), Alberta (Canada), Patagonia (Argentina), Pernambuco (Brazil), Western Peru, Spain, the Southern Sahara and North-Eastern Kalahari deserts, Rajasthan and Madhya Pradesh (India), Mongolia, the Yang-Tze Basin (China), and the North-Eastern and South-Western Australian coasts. On the other hand, Central U.S., Paraguay and Northern Argentina, Scandinavia, Northern Australia, and Western China moved to a wetter climate in the last period. Due to the low data availability, we assumed that no changes took place in Antarctica, which is meant to be under a permanent ice cap, excluding the northernmost Graham Land.

Spinoni, Jonathan; Micale, Fabio; Carrao, Hugo; Naumann, Gustavo; Barbosa, Paulo; Vogt, Jürgen

2013-04-01

230

Geomorphologic, stratigraphic and sedimentologic evidences of tectonic activity in Sone-Ganga alluvial tract in Middle Ganga Plain, India  

NASA Astrophysics Data System (ADS)

The basement of the Ganga basin in the Himalayan foreland is criss-crossed by several faults, dividing the basin into several sub-blocks forming horsts, grabens, or half-grabens. Tectonic perturbations along basement faults have affected the fluvial regime and extent of sediment fill in different parts of the basin during Late Quaternary. The East Patna Fault (EPF) and the West Patna Fault (WPF), located in Sone-Ganga alluvial tract in the southern marginal parts of Middle Ganga Plain (MGP), have remained tectonically active. The EPF particularly has acted significantly and influenced in evolving the geomorphological landscape and the stratigraphic architecture of the area. The block bounded by the two faults has earlier been considered as a single entity, constituting a half-graben. The present investigation (by morpho-stratigraphic and sedimentologic means) has revealed the existence of yet another fault within the half-graben, referred to as Bishunpur-Khagaul Fault (BKF). Many of the long profile morphological characters (e.g., knick-zone, low width-depth ratio) of the Sone River at its lower reaches can be ascribed to local structural deformation along BKF. These basement faults in MGP lie parallel to each other in NE-SW direction.

Sahu, Sudarsan; Saha, Dipankar

2014-08-01

231

Preface paper to the Semi-Arid Land-Surface-Atmosphere (SALSA) Program special issue  

USGS Publications Warehouse

The Semi-Arid Land-Surface-Atmosphere Program (SALSA) is a multi-agency, multi-national research effort that seeks to evaluate the consequences of natural and human-induced environmental change in semi-arid regions. The ultimate goal of SALSA is to advance scientific understanding of the semi-arid portion of the hydrosphere-biosphere interface in order to provide reliable information for environmental decision making. SALSA approaches this goal through a program of long-term, integrated observations, process research, modeling, assessment, and information management that is sustained by cooperation among scientists and information users. In this preface to the SALSA special issue, general program background information and the critical nature of semi-arid regions is presented. A brief description of the Upper San Pedro River Basin, the initial location for focused SALSA research follows. Several overarching research objectives under which much of the interdisciplinary research contained in the special issue was undertaken are discussed. Principal methods, primary research sites and data collection used by numerous investigators during 1997-1999 are then presented. Scientists from about 20 US, five European (four French and one Dutch), and three Mexican agencies and institutions have collaborated closely to make the research leading to this special issue a reality. The SALSA Program has served as a model of interagency cooperation by breaking new ground in the approach to large scale interdisciplinary science with relatively limited resources.

Goodrich, D.C.; Chehbouni, A.; Goff, B.; MacNish, B.; Maddock, T.; Moran, S.; Shuttleworth, W.J.; Williams, D.G.; Watts, C.; Hipps, L.H.; Cooper, D.I.; Schieldge, J.; Kerr, Y.H.; Arias, H.; Kirkland, M.; Carlos, R.; Cayrol, P.; Kepner, W.; Jones, B.; Avissar, R.; Begue, A.; Bonnefond, J.-M.; Boulet, G.; Branan, B.; Brunel, J.P.; Chen, L.C.; Clarke, T.; Davis, M.R.; DeBruin, H.; Dedieu, G.; Elguero, E.; Eichinger, W.E.; Everitt, J.; Garatuza-Payan, J.; Gempko, V.L.; Gupta, H.; Harlow, C.; Hartogensis, O.; Helfert, M.; Holifield, C.; Hymer, D.; Kahle, A.; Keefer, T.; Krishnamoorthy, S.; Lhomme, J.-P.; Lagouarde, J.-P.; Lo, Seen D.; Luquet, D.; Marsett, R.; Monteny, B.; Ni, W.; Nouvellon, Y.; Pinker, R.; Peters, C.; Pool, D.; Qi, J.; Rambal, S.; Rodriguez, J.; Santiago, F.; Sano, E.; Schaeffer, S.M.; Schulte, M.; Scott, R.; Shao, X.; Snyder, K.A.; Sorooshian, S.; Unkrich, C.L.; Whitaker, M.; Yucel, I.

2000-01-01

232

Genetic diversity, fixation and differentiation of the freshwater snail Biomphalaria pfeifferi (Gastropoda, Planorbidae) in arid lands.  

PubMed

The freshwater snail Biomphalaria pfeifferi is the main intermediate host of human intestinal Bilharziasis. It is widely distributed in Africa, Madagascar and middle-eastern countries, and its habitat includes wetlands, and arid to semi-arid areas. Based on analysis of 18 microsatellites, we investigated reference allelic variation among 30 populations of B. pfeifferi from three drainage basins in Dhofar, Oman (the eastern limit of its distribution). This is an arid to semi-arid region, with a 9,000-year history of very low rainfall, but is subject to unpredictable and destructive flash floods. In this context we showed that genetic fixation was very high compared to genetic differentiation which was moderate and, that, relative to B. pfeifferi populations from wetlands, the populations in Dhofar show evidence of lower levels of genetic diversity, a higher degree of genetic fixation, a quasi-absence of migration, and a higher level of genetic drift. Despite the extreme conditions in the Dhofar habitat of this species, it is able to survive because of its very high self-fertilization (approaching 100 %) and fecundity rates. PMID:23543205

Mintsa Nguema, Rodrigue; Langand, Juliette; Galinier, Richard; Idris, Mohamed A; Shaban, Mahmoud A; Al Yafae, Salem; Moné, Hélène; Mouahid, Gabriel

2013-06-01

233

Sedimentology and geochemistry of carbonates from lacustrine sequences in the Madrid Basin, central Spain  

Microsoft Academic Search

Lacustrine and alluvial carbonate facies have been investigated in Middle Miocene successions of the western side of the Madrid Basin in order to evaluate paleoenvironments in which carbonates formed. Carbonate facies are varied and include: (1) calcrete and dolocrete; (2) pond deposits; (3) lake margin dolostone; (4) mudflat carbonate; and (5) open-lake carbonate facies. The dominant mineralogy of these is

J. P. Calvo; B. F. Jones; M. Bustillo; R. Fort; A. M. Alonso Zarza; C. Kendall

1995-01-01

234

The migration, dissolution, and fate of chlorinated solvents in the urbanized alluvial valleys of the southwestern USA  

NASA Astrophysics Data System (ADS)

The migration, dissolution, and subsequent fate of spilled chlorinated solvents in the urban alluvial valleys of the southwestern U.S. appear to be governed by a unique set of hydrogeologic and geochemical processes occurring within terrigeneous clastic depositional systems. The alluvial and lacustrine fill of the basins, the trapping of solvents in fine-grained sediments beneath the urbanized valley centers, the oxic conditions typical of the deeper alluvium, and the contaminant-transport patterns produced by large-scale basin pumping combine to produce long aqueous-phase plumes derived from the dissolution of trapped chlorinated solvents. Although of limited aqueous solubility, these dense solvents are sufficiently mobile and soluble in the southwestern alluvial valleys to have produced aqueous plumes that have migrated several kilometers through the deeper alluvium and have contaminated valuable water-supply well fields in California, Arizona, and New Mexico. The typical length of these plumes and the presence of oxic groundwater indicate that it is unlikely that natural attenuation will be a practical remedial option in the southwestern alluvial valleys or in other alluvial systems in which similar hydrogeologic and geochemical conditions exist. Résumé La migration, la dissolution et l'évolution consécutive des rejets de solvants chlorés dans les vallées alluviales du sud-ouest des États-Unis paraissent déterminées par un même ensemble de processus hydrogéologiques et géochimiques intervenant dans des formations de dépôts clastiques terrigènes. Les remplissages alluviaux et lacustres des bassins, le piégeage des solvants par des sédiments fins sous les centres des vallées urbanisées, les conditions oxiques typiques des alluvions plus profondes et les types de transport de contaminants provoqués par le pompage à l'échelle du bassin se combinent pour produire des panaches, étendus dans la phase aqueuse, provenant de la dissolution de solvants chlorés piégés. Malgré leur faible solubilité dans l'eau, ces solvants denses sont suffisamment mobiles et solubles pour avoir produit, dans le sud-ouest des vallées alluviales, des panaches aqueux qui ont migré de plusieurs kilomètres dans les alluvions plus profondes et ont contaminé des champs captants pour l'eau potable en Californie, en Arizona et au Nouveau-Mexique. La longueur de ces panaches et la présence d'eau souterraine en conditions oxiques indiquent qu'il est peu probable que la décroissance naturelle soit un recours pratique de décontamination dans les vallées alluviales du sud-ouest ou dans d'autres systèmes alluviaux dans lesquels existent des conditions hydrogéologiques et géochimiques semblables. Resumen La migración, disolución y transporte de compuestos clorados en valles aluviales urbanos del sudoeste de los Estados Unidos de América parecen estar gobernados por un conjunto único de procesos hidrogeológicos y geoquímicos que tienen lugar en los depósitos clásticos. El relleno aluvial y lacustre de las cuencas, la inmovilización de los solutos en sedimentos de grano fino bajo las zonas urbanizadas, los condiciones óxicas típicas del aluvial profundo y las direcciones de transporte regidas por los fuertes bombeos en las cuencas se combinan para producir grandes penachos en fase acuosa procedentes de la disolución de los compuestos clorados atrapados en el medio. Aunque la solubilidad de estos compuestos clorados densos es pequeña, es suficiente para producir penachos que en algunos casos se han desplazado varios kilómetros a través del aluvial profundo y han llegado a contaminar zonas de extracción muy productivas en California, Arizona y Nuevo México. La longitud de estos penachos y la presencia de agua subterránea oxidante indican que es improbable que la degradación natural sea un buen método de limpieza de estos acuíferos o de otros sistemas aluviales que presenten características hidrogeológicas y geoquímicas semejantes.

Jackson, R. E.

235

Alluvial Diamond Resource Potential and Production Capacity Assessment of Ghana  

USGS Publications Warehouse

In May of 2000, a meeting was convened in Kimberley, South Africa, and attended by representatives of the diamond industry and leaders of African governments to develop a certification process intended to assure that rough, exported diamonds were free of conflictual concerns. This meeting was supported later in 2000 by the United Nations in a resolution adopted by the General Assembly. By 2002, the Kimberley Process Certification Scheme (KPCS) was ratified and signed by both diamond-producing and diamond-importing countries. Over 70 countries were included as members at the end of 2007. To prevent trade in 'conflict' diamonds while protecting legitimate trade, the KPCS requires that each country set up an internal system of controls to prevent conflict diamonds from entering any imported or exported shipments of rough diamonds. Every diamond or diamond shipment must be accompanied by a Kimberley Process (KP) certificate and be contained in tamper-proof packaging. The objective of this study was to assess the alluvial diamond resource endowment and current production capacity of the alluvial diamond-mining sector in Ghana. A modified volume and grade methodology was used to estimate the remaining diamond reserves within the Birim and Bonsa diamond fields. The production capacity of the sector was estimated using a formulaic expression of the number of workers reported in the sector, their productivity, and the average grade of deposits mined. This study estimates that there are approximately 91,600,000 carats of alluvial diamonds remaining in both the Birim and Bonsa diamond fields: 89,000,000 carats in the Birim and 2,600,000 carats in the Bonsa. Production capacity is calculated to be 765,000 carats per year, based on the formula used and available data on the number of workers and worker productivity. Annual production is highly dependent on the international diamond market and prices, the numbers of seasonal workers actively mining in the sector, and environmental conditions, which influence seasonal farming.

Chirico, Peter G.; Malpeli, Katherine C.; Anum, Solomon; Phillips, Emily C.

2010-01-01

236

Hydrocarbon potential of early mesozoic basins of eastern United States  

SciTech Connect

The exposed Triassic-Liassic rift basins in the eastern United States are half-grabens filled with up to 7 km of continental sediments. The location and sense of asymmetry of the half-grabens are closely tied to the structural grain of the Appalachian crystalline terranes on which they have formed. In many instances, the faulted margins of the basins are older thrusts or terrane boundaries reactivated as listric normal faults. The sediment fill of the basins reflects their structural asymmetry. Coarse alluvial fan deposits along the main border faults pass basinward into a complex assemblage of fluvial, paludal, and lacustrine facies. The oldest sediment fill in the rift basins is dated palynologically as late Ladinian to late Carnian. Perhaps reflecting the northward opening of the central Atlantic, the youngest rift-fill sediments are older in the southern basins than in the northern-Carnian in the Righmond basin vs. Toarcian in the Hartford-Deerfield basin. Floral evidence points to a tropical to near-tropical environment, with severe oscillations between xerophytic (dry) and hydrophytic (wet) conditions. The degree of thermal maturation, as estimated from vitrinite reflectance and clay mineralogy, varies widely from basin to basin; however, most of the basins are within the oil to dry gas generative window. The basins with highest thermal maturities are those having large volumes of diabase intrusives and presumed higher paleogeothermal gradients. The peak of thermal maturation/migration may have occurred as early as the Jurassic.

Schlamel, S.

1988-01-01

237

Depositional character of a dry-climate alluvial fan system from Palaeoproterozoic rift setting using facies architecture and palaeohydraulics: Example from the Par Formation, Gwalior Group, central India  

NASA Astrophysics Data System (ADS)

The ?20 m thick coarse-grained clastic succession in the basal part of Palaeoproterozoic Par Formation, Gwalior Group has been investigated using process-based sedimentology and deductive palaeohydraulics. Bounded between granitic basement at its base and shallow marine succession at the top, the studied stratigraphic interval represents products of an alluvial fan and its strike-wise co-existent braided river system that possibly acted as a tributary for the fan. Detailed facies, facies association analysis allowed identification of two anatomical parts for the fan system viz. proximal and mid fan. While thin proximal fan is represented by products of rock avalanche and hyperconcentrated flows with widely varying rheology, the mid fan is represented by products of sheet floods and flows within streamlets. The interpretation found support from palaeoslope estimation carried out on the fluvial part of the mid fan that plot dominantly within the alluvial fan field demarcated by Blair and McPherson (1994). Dry climatic condition suggested from dominance of stream flow over mass flow deposition within the Par alluvial fan. Strike-wise, the fan is discontinuous and juxtaposed with a braid plain system. In contrast to the fluvial part of fan system, the palaeoslope data from the braid plain system dominantly plot within the ‘natural depositional gap' defined by Blair and McPherson. A raised palaeoslope for the river systems, as suggested from Proterozoic braid plain deposits around the Globe, is found valid for the Par braid plain system as well. From preponderance of granular and sandy sediments within the alluvial fan and braid plain systems and a pervasive north-westward palaeocurrent pattern within the fluvial systems the present study infers a gently sloping bevelled source area in the south-southeast of the basin with occurrence of steep cliffs only locally.

Chakraborty, Partha Pratim; Paul, Pritam

2014-09-01

238

Are North Slope surface alluvial fans pre-Holocene relicts?  

USGS Publications Warehouse

The surface morphology of the northern slope of the Brooks Range (North Slope) from the Canning River, Alaska, eastward is dominated by a series of large alluvial fans and braided streams floored by coarse alluvium. On the basis of our studies, we conclude that the fans are not prograding now nor have they been prograding at any time during the Holocene. During the latest transgression and the following sea-level highstand, the North Slope depositional environment and climate probably differed greatly from the present ones.

Reimnitz, Erk; Wolf, Stephen C.

1998-01-01

239

Groundwater arsenic contamination in Brahmaputra river basin: a water quality assessment in Golaghat (Assam), India  

Microsoft Academic Search

Distribution of arsenic (As) and its compound and related toxicology are serious concerns nowadays. Millions of individuals\\u000a worldwide are suffering from arsenic toxic effect due to drinking of As-contaminated groundwater. The Bengal delta plain,\\u000a which is formed by the Ganga–Padma–Meghna–Brahmaputra river basin, covering several districts of West Bengal, India, and Bangladesh\\u000a is considered as the worst As-affected alluvial basin. The

Mridul Chetia; Soumya Chatterjee; Saumen Banerjee; Manash J. Nath; Lokendra Singh; Ravi B. Srivastava; Hari P. Sarma

2011-01-01

240

Tectonics and Quaternary sequence development of basins along the active Vienna Basin strike-slip fault  

NASA Astrophysics Data System (ADS)

The Vienna Basin strike-slip fault is a continent scale active fault extending over a distance of some 300 km from the Eastern Alps through the Vienna Basin into the Western Carpathians. Sinistral movement causes the formation of several tight Pleistocene strike-slip basins within the older Miocene Vienna Basin. These sub-basins not only have a high relevance for groundwater exploitation but their fault activities depict serious seismic hazards. Basins are filled with fluvial sediments from the Danube and, closer to the Alpine front, with thick alluvial fan deposits. However, knowledge on the stratigraphy and tectonics is sparse and rather limited to the Miocene part of the Vienna Basin as it hosts giant hydrocarbon fields. This study tackles two major questions: (i) What is the effect of Quaternary climatic oscillations and subsidence on the sequence development of the alluvial fans and (ii) what is the deformation style of these basins? To answer (i) we present a series of new OSL ages and biotic data from both, surface and cores, to better constrain the timing of fan activity, fan abandonment but also to constrain the onset of Pleistocene basin formation. For (ii) we utilize information from unparalleled geophysical and geological data. Specifically we utilize industrial Bouguer gravity's derivatives to highlight shallow structures and to compensate for the lag of fault trace information. The integration of geological and geophysical data highlights textbook-like models of strike-slip basins, with typical features like Riedel shears with intervening relay ramps, en-echelon sidewall faults and a cross-basin fault zone delimiting opposite depocenters. The infill reflects a distinct cyclicity with thick sequences of coarse sediments deposited during colder periods and thin sequences of paleosol and flood sediments deposited during warmer periods. Ages indicate main activity around the short peak glacial periods and basin formation starting c. 300 ka ago. The distinct sequence development and the strong contrast to the underlying marine deposits is a very suitable setting to apply geophysical methods constraining basins' deformation style.

Salcher, B.; Lomax, J.; Meurers, B.; Smit, J.; Preusser, F.; Decker, K.

2012-04-01

241

Resource pulses, species interactions, and diversity maintenance in arid and semi-arid environments  

Microsoft Academic Search

Arid environments are characterized by limited and variable rainfall that supplies resources in pulses. Resource pulsing is a special form of environmental variation, and the general theory of coexistence in variable environments suggests specific mechanisms by which rainfall variability might contribute to the maintenance of high species diversity in arid ecosystems. In this review, we discuss physiological, morphological, and life-history

Peter Chesson; Renate L. E. Gebauer; Susan Schwinning; Nancy Huntly; Kerstin Wiegand; Morgan S. K. Ernest; Anna Sher; Ariel Novoplansky; Jake F. Weltzin

2004-01-01

242

Use of bio-technology in sludge treatment to ameliorat arid and semi-arid soil  

Microsoft Academic Search

Desert soils in arid and semi-arid regions are poor in organic matter and nutrient elements which is the second factor after water for developing these soils. Organic matter is important to improve the biological, chemical and physical properties of sandy soils as well as a source of nutrients elements for growing plants. As a result of sewage sludge contains macro-

2004-01-01

243

Sedimentology and depositional environments of the Red Sandstone Group, Rukwa Rift Basin, southwestern Tanzania: New insight into Cretaceous and Paleogene terrestrial ecosystems and tectonics in sub-equatorial Africa  

NASA Astrophysics Data System (ADS)

The Red Sandstone Group (RSG) in the Rukwa Rift Basin of southwestern Tanzania represents one of the only well-exposed, fossiliferous Cretaceous-Paleogene continental sedimentary sequences in sub-equatorial Africa. The significance of the RSG for reconstructing the paleoenvironmental and paleoclimatic history of African ecosystems during these critical time periods has been obfuscated by long-standing confusion and debate over the age of the deposits. Detailed stratigraphic, sedimentologic, and paleontologic investigations of the RSG conducted between 2002 and 2008 have produced a wealth of new fossil discoveries and data on lithofacies, alluvial architecture, sedimentary provenance, clay mineralogy and geochronology that resolve the long-standing debate over the age of these deposits. This study confirms the existence of an extensive middle Cretaceous sequence, herein named the Galula Formation, and subdivided into the Mtuka and Namba members. Moreover, we document the existence of a previously unrecognized late Paleogene continental sequence termed the Nsungwe Formation, which is divided into the Utengule and Songwe members. The Galula Formation represents a 600-3000 m thick sequence of amalgamated, braided fluvial deposits that were deposited across a large braidplain system via multiple parallel channels that had their source in the highlands of Malawi and Zambia. The middle Cretaceous Dinosaur Beds of Malawi are hypothesized to be at least partially correlative with the Galula Formation, and represent proximal deposits of this large, northwest flowing, trunk stream system. A moderately diverse terrestrial vertebrate fauna, including multiple species of dinosaurs, crocodyliforms, turtles, fishes and mammals have been recovered, along with a sparse aquatic molluscan fauna. Lithofacies and clay mineralogy indicate that Cretaceous paleoclimate ameliorated during deposition of the Galula Formation, transitioning from tropical semi-arid to tropical humid conditions. The 400+ m-thick late Oligocene Nsungwe Formation is temporally constrained by concordant mammalian biostratigraphy, detrital zircon geochronology and a radiometrically dated volcanic tuff capping the sequence (˜24.9 Ma). A significant change in depositional environments occurs between the lower alluvial fan-dominated Utengule Member and the upper fluvial and lacustrine-dominated Songwe Member. The Songwe Member preserves a diverse terrestrial and aquatic vertebrate and invertebrate fauna, with abundant ashfall and ashflow volcanic tuffs that were deposited in a semi-arid wetland landscape during the late Oligocene. The Nsungwe Formation provides a new window into the early tectonics and faunal transitions associated with initiation of the "modern" East African Rift System.

Roberts, Eric M.; O'Connor, Patrick M.; Stevens, Nancy J.; Gottfried, Michael D.; Jinnah, Zubair A.; Ngasala, Sifael; Choh, Adeline M.; Armstrong, Richard A.

2010-05-01

244

Soil texture controls vegetation biomass and soil organic carbon storage in arid desert grassland in the middle of Hexi Corridor region of northwest China  

NASA Astrophysics Data System (ADS)

Soil texture may play an important role in controlling vegetation distribution pattern and net primary production, as well as soil organic carbon (SOC) concentration and stock in arid desert grassland ecosystem. However, little information is available in the current literature on the occurrence and extent of these textural effects in arid desert grasslands in northwest China. The main objective of this study was to quantify the relationships between soil texture (silt + clay) and above-and below-ground biomass, SOC concentration and stock in arid Hexi corridor desert grasslands of northwest China. Above-and below-ground biomass were investigated and SOC concentration, bulk density, stone content, and soil particle size distribution at the seven layers of 100cm profile were determined in the selected 32 grassland sites located in the similar topographical units (alluvial-diluvial fans) in the study area. The results showed that above-ground biomass was higher than below-ground biomass, with a mean value of 0.67 in the below-ground biomass / above-ground biomass ratio (R/S). More than 95% of below-ground biomass distributed in the top 30 cm depth. Spatially, desert grassland vegetation biomass was positively related to soil sit+clay content. The mean SOC density in the 0-100 cm depth was 2.94 kg m-2 in the arid desert grasslands. SOC concentrations and stocks were positively and significantly related to silt+clay content for the seven soil layers sampled up to a depth of 100 cm. Soil silt+clay content explained 42%-79% of the variation in SOC stocks. In conclusion, soil texture appeared to have an important impact on the vegetation productivity and distribution pattern, and is an important controlling factor of SOC stocks in arid Hexi Corridor grassland soils. Keywords: soil texture, vegetation biomass, SOC stock, arid desert grassland, northwest China

su, Yong-zhong

2014-05-01

245

Faulting and Groundwater in Arid Environments: Ground and Airborne Geophysics in Support of Framework Hydrology  

NASA Astrophysics Data System (ADS)

In the Mojave Desert of the southwestern USA, groundwater is compartmentalized within a series of fault-bounded basins. As part of an effort to understand and manage groundwater resources in arid environments, the USGS is investigating basins within the Fort Irwin National Training Center through a combination of hydrologic, geophysical, and geochemical approaches. Airborne time-domain electromagnetic (TDEM) data were collected within the Leach Basin, a geologically complex, internally-drained basin bisected and flanked by a number of Quaternary faults, including the Garlock fault and the Death Valley fault zone. The airborne TDEM data provide subsurface constraints down to approximately 200 m depth, and show abrupt changes in earth response across faulted boundaries, reflecting the strong lateral resistivity contrast between igneous rocks and basin sediments. Intra-basin faults are additionally identified, and to a lesser extent faults within the igneous basement can be traced. The distribution of faults throughout the basin and within the subsurface can thus be directly obtained from the airborne data. These electrical discontinuities, however, present challenges for the laterally-constrained inversion approach we applied, and we present alternative approaches to inverting these data which honor the complexity of the region. We further outline a multivariate approach to fault identification which combines resistivity models, airborne magnetics, and surface topography. A resistivity stratigraphy has been developed using borehole geophysical logs, ground-based gravity, TDEM soundings, and lab resistivity measurements from nearby basins. The results are applied to the airborne resistivity models and used to trace aquifer hydrostratigraphy throughout the basin. Interpreted parameters include the depth to basement, the base of the primary aquifer, depth to water, and variations in groundwater salinity. Together with hydrologic investigations, these results are being used to estimate groundwater storage within the basin.

Bedrosian, P. A.; Burgess, M. K.; Bloss, B.; Ball, L. B.; Polster, S.; Densmore, J.; Martin, P.; Langenheim, V. E.; Jachens, R. C.

2011-12-01

246

Sources and transport of nitrogen in arid urban watersheds.  

PubMed

Urban watersheds are often sources of nitrogen (N) to downstream systems, contributing to poor water quality. However, it is unknown which components (e.g., land cover and stormwater infrastructure type) of urban watersheds contribute to N export and which may be sites of retention. In this study we investigated which watershed characteristics control N sourcing, biogeochemical processing of nitrate (NO3-) during storms, and the amount of rainfall N that is retained within urban watersheds. We used triple isotopes of NO3- (?15N, ?18O, and ?17O) to identify sources and transformations of NO3- during storms from 10 nested arid urban watersheds that varied in stormwater infrastructure type and drainage area. Stormwater infrastructure and land cover--retention basins, pipes, and grass cover--dictated the sourcing of NO3- in runoff. Urban watersheds were strong sinks or sources of N to stormwater depending on runoff, which in turn was inversely related to retention basin density and positively related to imperviousness and precipitation. Our results suggest that watershed characteristics control the sources and transport of inorganic N in urban stormwater but that retention of inorganic N at the time scale of individual runoff events is controlled by hydrologic, rather than biogeochemical, mechanisms. PMID:24803360

Hale, Rebecca L; Turnbull, Laura; Earl, Stevan; Grimm, Nancy; Riha, Krystin; Michalski, Greg; Lohse, Kathleen A; Childers, Daniel

2014-06-01

247

Water harvesting techniques for small communities in arid areas.  

PubMed

Limited water resources exist in numerous remote indigenous settlements around Australia. Indigenous people in these communities are still living in rudimentary conditions while their urban counterparts have full amenities, large scale water supplies and behavioral practices which may not be appropriate for an arid continent but are supported by extensive infrastructure in higher rainfall coastal areas. As remote indigenous communities continue to develop, their water use will increase, and in some cases, costly solutions may have to be implemented to augment supplies. Water harvesting techniques have been applied in settlements on a small scale for domestic and municipal purposes, and in the large, broadacre farm setting for productive use of the water. The techniques discussed include swales, infiltration basins, infiltration trenches and "sand dam" basins. This paper reviews the applications of water harvesting relevant to small communities for land rehabilitation, landscaping and flood control. Landscaping is important in these communities as it provides shelter from the sun and wind, reduces soil erosion and hence reduced airborne dust, and in some cases provides food and nutrition. Case studies of water harvesting systems applied in the Pilbara Region, Western Australia for landscaping around single dwellings in Jigalong and Cheeditha, in a permaculture garden in Wittenoon and at a college and carpark in Karratha are described. PMID:11700659

Yuen, E; Anda, M; Mathew, K; Ho, G

2001-01-01

248

Herbicide interchange between a stream and the adjacent alluvial aquifer  

USGS Publications Warehouse

Herbicide interchange between a stream and the adjacent alluvial aquifer and quantification of herbicide bank storage during high streamflow were investigated at a research site on the Cedar River flood plain, 10 km southeast of Cedar Rapids, Iowa. During high streamflow in March 1990, alachlor, atrazine, and metolachlor were detected at concentrations above background in water from wells as distant as 20, 50, and 10 m from the river's edge, respectively. During high streamflow in May 1990, alachlor, atrazine, cyanazine, and metolachlor were detected at concentrations above background as distant as 20, 50, 10, and 20 m from the river's edge, respectively. Herbicide bank storage took place during high streamflow when hydraulic gradients were from the river to the alluvial aquifer and the laterally infiltrating river water contained herbicide concentrations larger than background concentrations in the aquifer. The herbicide bank storage can be quantified by multiplying herbicide concentration by the "effective area" that a well represented and an assumed porosity of 0.25. During March 1990, herbicide bank storage values were calculated to be 1.7,79, and 4.0 mg/m for alachlor, atrazine, and metolachlor, respectively. During May 1990, values were 7.1, 54, 11, and 19 mg/m for alachlor, atrazine, cyanazine, and metolachlor, respectively. ?? 1994 American Chemical Society.

Wang, W.; Squillace, P.

1994-01-01

249

RIVER TRANSPORT - INDUCED CHANGES IN CHEMICAL COMPOSITION OF ALLUVIAL GOLD (DOCUMENTED ON LOCALITIES THE WESTERN CARPATHIANS)  

Microsoft Academic Search

Alluvial gold is influenced by various physical, chemical and biological factors. As type- localities for study of changes in chemical composition of alluvial gold we chose Pukanec (Central Slovakia Neovolcanic Field) and Magurka and Ni?ná Boca (Nízke Tatry Mts). The most distinctive are morphological and chemical changes (dissolution and precipitation), the latter is most commonly represented by the formation of

B. BAHNA; A. SMIRNOV; M. CHOVAN; F. BAKOS

250

A. Reservoir Effects of Stream Channels DAM IMPACTS ON AND RESTORATION OF AN ALLUVIAL RIVER  

E-print Network

of 35 dams on large rivers in the Western U.S. that rivers with braided patterns tended to narrowA. Reservoir Effects of Stream Channels DAM IMPACTS ON AND RESTORATION OF AN ALLUVIAL RIVER ­ RIO and reservoirs on alluvial rivers extends both upstream and downstream of the dam. Downstream of dams, both

Julien, Pierre Y.

251

Statistic inversion of multi-zone transition probability models for aquifer characterization in alluvial fans  

E-print Network

Understanding the heterogeneity arising from the complex architecture of sedimentary sequences in alluvial fans is challenging. This paper develops a statistical inverse framework in a multi-zone transition probability approach for characterizing the heterogeneity in alluvial fans. An analytical solution of the transition probability matrix is used to define the statistical relationships among different hydrofacies and their mean lengths, integral scales, and volumetric proportions. A statistical inversion is conducted to identify the multi-zone transition probability models and estimate the optimal statistical parameters using the modified Gauss-Newton-Levenberg-Marquardt method. The Jacobian matrix is computed by the sensitivity equation method, which results in an accurate inverse solution with quantification of parameter uncertainty. We use the Chaobai River alluvial fan in the Beijing Plain, China, as an example for elucidating the methodology of alluvial fan characterization. The alluvial fan is divided...

Zhu, Lin; Gong, Huili; Gable, Carl; Teatini, Pietro

2015-01-01

252

Chromium and nickel as indicators of source-to-sink sediment transfer in a Holocene alluvial and coastal system (Po Plain, Italy)  

NASA Astrophysics Data System (ADS)

A reliable quantitative estimate of changes in source-to-sink sediment transfer requires that high-resolution stratigraphic studies be coupled with accurate reconstructions of spatial and temporal variability of the sediment-routing system through time. Source-to-sink patterns from the contributing upland river catchments to the deltaic and coastal system are reconstructed from the Holocene succession of the Po Plain on the basis of selected geochemical indicators. Sediment supplied to the delta area by the major trunk river (the Po) exhibits naturally high Cr and Ni values, which invariably exceed the maximum permissible concentrations for unpolluted sites. This 'anomaly' reflects remarkable sediment contribution from ultramafic (ophiolitic) parent rocks cropping out in the Po drainage basin (Western Alps and NW Apennines). In contrast, alluvial and coastal plain deposits supplied by ophiolite-free, Apenninic catchments invariably display lower Cr and Ni contents. For constant sediment provenance domain, Cr and Ni distribution is observed to be controlled primarily by hydraulic sorting. Clay-silt deposits (floodplain, swamp and lagoon/bay facies associations) invariably show higher metal concentrations than their sandy counterparts (fluvial-channel, distributary-channel and beach-ridge facies associations). From a stratigraphic perspective, in sedimentary basins characterized by strong differences in sediment composition geochemical fingerprinting of individual facies associations framed by surfaces of chronostratigraphic significance is proposed as an invaluable approach towards an accurate quantitative assessment of sediment storage in alluvial and coastal depositional systems as opposed to volumetric reconstructions based on lithologic or geometric criteria alone.

Amorosi, Alessandro

2012-12-01

253

Lake evolution of the terminal area of Shiyang River drainage in arid China since the last glaciation  

Microsoft Academic Search

Investigations of geomorphology and sedimentology, and analyses of radiocarbon dates, grain size and carbonate of the sediment at the present-dry closed basin in the terminal area of Shiyang River in arid China were conducted to recover the history of palaeolake change since the last glacial. The terminal area was covered by eolian sand before 13,000 14C BP. Lacustrine deposits covered

Q. Shi; Fa-Hu Chen; Yan Zhu; David Madsen

2002-01-01

254

Sustainable Water Use System of Artesian Water in Alluvial Fan  

NASA Astrophysics Data System (ADS)

The traditional water use system, developed with the intelligence of the local residents, usually takes advantage of local natural resources and is considered as a sustainable system, because of its energy saving(only forces of nature). For this reason, such kind of water use system is also recommended in some strategic policies for the purpose of a symbiosis between nature and human society. Therefore, it is important to clarify the relationship between human activities and water use systems. This study aims to clarify the mechanism of traditional water use processes in alluvial fan, and in addition, to investigate the important factors which help forming a sustainable water use system from the aspects of natural conditions and human activities. The study area, an alluvial fan region named Adogawa, is located in Shiga Prefecture, Japan and is in the west of Biwa Lake which is the largest lake in Japan. In this alluvial region where the land use is mainly occupied by settlements and paddy fields, a groundwater flowing well system is called "kabata" according to local tradition. During field survey, we took samples of groundwater, river water and lake water as well as measured the potential head of groundwater. The results showed that the upper boundary of flowing water was approximately 88m amsl, which is basically the same as the results reported by Kishi and Kanno (1966). In study area, a rapid increase of water pumping for domestic water use and melting snow during last 50 years, even if the irrigation area has decreased about 30% since 1970, and this fact may cause a decrease in recharge rate to groundwater. However, the groundwater level didn't decline based on the observed results, which is probably contributed by some water conservancy projects on Biwa Lake which maintained the water level of the lake. All the water samples are characterized by Ca-HCO3 type and similar stable isotopic value of ?D and ?18O. Groundwater level in irrigation season is higher than that in non-irrigation season, which indicates that groundwater level is apparently influenced by surface water. Some communities and NPOs working in this area maintain the "kabata" and canal for environment conservation. There are many rules for the local residents when using the water resources. For example, the use of detergents is prohibited for "kabata" users. The residents living upstream also should think of other groundwater users downstream. For this reason, it can be considered that the "kabata" water use method contributed to a symbiosis between ecosystem and human activity The study area case showed that the traditional water use system is useful for forming a sustainable groundwater flowing well use system.

Kishi, K.; Tsujimura, M.; Tase, N.

2013-12-01

255

An aridity index defined by precipitation and specific humidity  

NASA Astrophysics Data System (ADS)

SummaryThe United Nations Environmental Programme (UNEP), defined an aridity index (AI) by the ratio of the annual precipitation and potential evapotranspiration (PET) totals. In this work, specific humidity was used instead of PET and a new aridity index (Iq) has been defined using the ratio of annual precipitation totals and annual mean specific humidity (Sh). As shown in this study, Sh can be easily computed with very high accuracy (3.569% error rate) with mean temperature, relative humidity and local pressure which are most commonly and widely measured meteorological data. The single point correlation graph of Sh which shows the entrance of aridity through the South Eastern Anatolia Region into Turkey and the distribution of the aridity over Turkey explains the relationship with Sh and aridity. According to the common and different aspects of arid zones found with AI, Iq and Erinç aridity index (Im), Iq found to be applicable for monitoring climate change and distribution of arid zones.

Sahin, Sinan

2012-06-01

256

An astronomically-tuned climate framework for hominins in the Turkana Basin Josephine C.A. Joordens a,b,  

E-print Network

hypothesize that during lake phases, the Turkana Basin was an aridity refugium for permanent-water dependentAn astronomically-tuned climate framework for hominins in the Turkana Basin Josephine C.A. Joordens a novel climate proxy, strontium isotope ratios (87 Sr/86 Sr) of lacustrine fish fossils from the Turkana

Utrecht, Universiteit

257

Architectural analysis and chronology of an Alpine alluvial fan using 3D ground penetrating radar investigation and quantitative outcrop analysis  

NASA Astrophysics Data System (ADS)

Alluvial fans represent sediment sinks directly at the outlet of the source area in mountain landscapes. They contain multiple information on short-term as well as on long-term changes of sediment supply and of environmental parameters like climate and vegetation. However, most studies on alluvial fans are restricted to selective surface analysis and almost no studies exist which aim to clear the subsurface geometry of an alluvial fan in total. Our study is embedded in the SedyMONT research program within the TOPO-EUROPE framework and aims to clarify the subsurface structure of an alluvial fan by a time-controlled 3D architectural model. The Illgraben fan is located in the Central Alps of Switzerland within the Rhone valley and covers an area of about 6.5 km2. Currently construction works for a highway cuts through the fan exposing its deposits (mainly gravel and diamicton) up to 15 m depth and therefore offers the unique opportunity to link ground penetrating radar (GPR) investigations with quantitative outcrop analysis. GPR measurements on the Illgraben fan have been carried out at two different scales: (i) a fan-wide scale with about 80 km radar sections forming a half spiderweb pattern to identify the fundamental architecture of the fan (using 100 MHz and 40 MHz antenna), and (ii) four orthogonal grids of about 50 m x 100 m for detailed architectural analysis (using a 200 MHz antenna). Penetration depth was up to 15 m for high and low frequency antennas. The radargrams were processed, georeferenced and transferred into a 3D-modeling software (GOCAD®) to map radar facies units. By means of quantitative sedimentological analyses and precisely scaled photo panels we could translate radar facies pattern into sedimentary facies, and interpret reflectors and their properties in terms of sedimentary units. These geobodies can be characterized in terms of volume, shape, geometrical key parameters, their spatial distribution, as well as internal sedimentary structures in order to identify depositional processes. Preliminary results show distinct horizons ('palaeosurfaces') indicating fan-wide depositional starvation and minimized sediment supply. Furthermore, between these horizons the Illgraben fan is built up by multi-storey and multilateral architectural elements of different type and at characteristic scales which can be attributed to specific depositional processes (e.g. debris flows, channel fills, levees). At small-scale a heterogeneous and complex stacking pattern of geobody interfaces was observed, showing a distinct multi-fold hierarchy of mainly concave, convex and horizontal structures. First 14C AMS ages from the central part of the alluvial fan (ca. 10 m depth) indicate high sedimentation rates during the past 2000 years. We found no control of natural spectral gamma-ray radiation by lithofacies units. Hence variations must indicate changes in the source areas and/or climate-controlled weathering conditions in the drainage basin (ca. 9.5 km2).

Franke, D.; Hornung, J.; Hinderer, M.

2012-04-01

258

Quantifying Spatial and Temporal Variability of Mountain System Recharge in Semi-Arid Catchments  

NASA Astrophysics Data System (ADS)

Groundwater recharge is likely to be altered as a result of climate change and variability impacting groundwater resources. In semi-arid Basin and Range systems where Mountain System Recharge (MSR) represents a significant component of recharge, this impact is likely to be more pronounced. Despite the importance of MSR in such basins' water budget, physical processes that control MSR have not been fully investigated due to complexity of recharge processes in mountainous catchments and limited soil moisture and water level elevation data. In most groundwater models, MSR is either derived from empirical relationships or estimated during the model calibration and water balance analysis. Therefore, these models are not capable of assessing the impact of climate variability and change on groundwater resources. The objective of this research is to enhance our conceptual understanding of MSR, and quantify temporal and spatial variability of MSR in selected semi-arid catchments in the Basin and Range province of Arizona. Water budget analysis was performed on a seasonal time scale using the Soil and Water Assessment Tool (SWAT2005). Isotopic and soil moisture data were used to provide a constraint on recharge seasonality and water balance partitioning. Preliminary results show annual variability of MSR with pronounced differences in winter and summer seasons. The ratio of MSR to precipitation varied between (0-20%) in summer with a median of 8% compared to (0-50%) in winter with a median of 18%. Moreover, a threshold response of MSR to winter and summer precipitation and soil moisture was shown over the simulation period in different catchments. These results demonstrate the advantage of using modeling approaches that can evaluate these seasonal recharge thresholds. The results further highlight the need for further understanding of the physical factors in semi-arid catchments that control precipitation partitioning into MSR such as vegetation, soil type and slope.

Ajami, H.; Hogan, J.; Maddock, T.; Meixner, T.; Troch, P.

2008-12-01

259

Strategies for cooler cities? Ecophysiological responses of semi-arid street trees to storm water harvesting  

NASA Astrophysics Data System (ADS)

As the southwestern U.S. moves into an uncertain future in terms of water supply and climate, communities are seeking creative ways to harvest urban runoff. One such solution is to implement water-sensitive urban design features such as rain basins, which are designed to capture and facilitate infiltration of precipitation and storm water as it runs off impermeable surfaces like streets and sidewalks. Rain basins essentially act as temporary cisterns, allowing a given rain event to have a much larger impact in recharging soil water profiles. In this sense, even a 'small' rain may yield a more saturated soil profile and stimulate plant physiological activity well beyond plants that lack this additional moisture input. However, the impacts of rain basins on plant function remain unquantified. Therefore, the purpose of our research is to characterize the performance of native mesquite trees in basins relative to non-basin native mesquites. To answer our question, we randomly sampled basin and non-basin native mesquites in two different neighborhoods in Tucson, AZ, and characterized their response to precipitation events. We measured stomatal conductance, a proxy for transpiration, on the first and third days following rain events in 2013. Numerous environmental factors, such as photosynthetically available radiation (PAR), temperature, relative humidity, and soil moisture, were also measured in order to explore relationships with conductance. These measurements were conducted before and during monsoon season in order to determine the significance of water in basin performance, enabling us to better characterize plant response to medium (6 to 12 mm) rain events. Findings from this study indicate that basin and non-basin mesquites have similar pre-monsoon conductance rates, with a mean basin value of 70 +/-10 mmol/(m2*s) and a mean non-basin value of 57 +/-6 mmol/(m2*s) at peak conductance. In contrast, during the monsoon, basin mesquites showed significantly higher peak conductance rates (179 +/-22 mmol/(m2*s)) than non-basin trees (126 +/-9 mmol/(m2*s)). Perhaps more importantly, basin mesquite conductance remained elevated for an extended period of time into the afternoon as compared to non-basin mesquites. While this difference was negligible before the monsoon, it was significant during the monsoon. The day immediately after a medium rainfall event, non-basin mesquites shut down around 13:00, while basin mesquites never shut down completely before the end of the measurement period around 17:30. Soil moisture levels were elevated in the rain basins relative to the non-basin soils, suggesting that basins impact plant functioning through enhanced soil water availability. These preliminary results demonstrate that basins are an effective means of capturing water and irrigating plants. Here we have demonstrated how an appreciation of wildland plant ecophysiology can be applied to an urban setting in support of a suite of ecosystem services. Notably, there is a potential for enhanced urban heat island mitigation in semi-arid cities through the application of water-sensitive urban design features such as rain basins, due to their supporting a longer duration of latent heat flux cooling (i.e., transpiration) into the afternoon.

DeMets, C. M.; Pavao-zuckerman, M.; Barron-Gafford, G.

2013-12-01

260

The measurement of total sediment load in alluvial streams  

USGS Publications Warehouse

The measurement of the total sediment load transported by streams that flow in alluvial channels has been a perplexing problem to engineers and geologists for over a century. Until the last decade the development of equipment to measure bed load and suspended load was carried on almost independently, and without primary consideration of the fundamental laws governing the transportation of fluvial sediments. French investigators during the nineteenth century described methods of measurement and a mathematical approach for computing the rate of bed-load movement. The comprehensive laboratory investigations by Gilbert early in this century provided data that are still being used for studies of sediment transport. Detailed laboratory investigations of bed-load movement conducted during the last two decades by a number of investigators have resulted in the development of additional mathematical formulas for computing rates of bed-load movement. Likewise, studies of turbulent flow have provided the turbulence suspension theory for suspended sediment as it is known today.

Benedict, P.C.; Matejka, D.Q.

1953-01-01

261

Methodologies for hydraulic hazard mapping in alluvial fan areas  

NASA Astrophysics Data System (ADS)

Hydraulic hazards in alluvial fan areas are mainly related to torrential floods and debris flows. These processes are characterized by their fast time evolution and relevant sediment load. Rational approaches for the estimation of hazard levels in flood-prone areas make use of the maps of depth and velocity, which are provided by numerical simulations of the event. This paper focuses on national regulations regarding quantitative debris-flow hazard mapping and compares them to a simple conceptual model for the quantification of the hazard levels on the basis of human stability in a flood. In particular, the proposed method takes into account, in a conceptual fashion, both the local slope and the density of the fluid, that are crucial aspects affecting stability for processes in mountain environments. Physically-based hazard criteria provide more comprehensible and objective maps, increasing awareness among stakeholders and providing more acceptable constraints for land planning.

Milanesi, L.; Pilotti, M.; Ranzi, R.; Valerio, G.

2014-09-01

262

Distinctive channel geometry and riparian vegetation: A geomorphic classification for arid ephemeral streams  

NASA Astrophysics Data System (ADS)

Interactions between hydrology, channel form, and riparian vegetation along arid ephemeral streams are not thoroughly understood and current stream classifications do not adequately represent variability in channel geometry and associated riparian communities. Relatively infrequent hydrologic disturbances in dryland environments are responsible for creation and maintenance of channel form that supports riparian communities. To investigate the influence of channel characteristics on riparian vegetation in the arid southwestern United States, we develop a geomorphic classification for arid ephemeral streams based on the degree of confinement and the composition of confining material that provide constraints on available moisture. Our conceptual model includes five stream types: 1) bedrock channels entirely confined by exposed bedrock and devoid of persistent alluvium; 2) bedrock with alluvium channels at least partially confined by bedrock but containing enough alluvium to create bedforms that persist through time; 3) incised alluvium channels bound only by unconsolidated alluvial material into which they are incised; 4) braided washes that exhibit multi-thread, braided characteristics regardless of the composition of confining material; and 5) piedmont headwater 0-2nd order streams (Strahler) confined only by unconsolidated alluvium and which initiate as secondary channels on piedmont surfaces. Eighty-six study reaches representing the five stream types were surveyed on the U.S. Army Yuma Proving Ground in the Sonoran Desert of southwestern Arizona. Non-parametric multivariate analysis of variance (PERMANOVA) indicates significant differences between the five stream types with regards to channel geometry (i.e., stream gradient, width-to-depth ratio, the ratio between valley width and channel width (Wv/Wc), shear stress, and unit stream power) and riparian vegetation (i.e., presence and canopy coverage by species, canopy stratum, and life form). Discriminant analysis of the physical driving variables is being conducted to produce a model that predicts stream type and resulting riparian vegetation communities based on channel geometry. This model will be tested on a separate set of 15 study reaches surveyed on the Barry M. Goldwater Air Force Range in southern Arizona. The resulting classification will provide a basis for examining relationships between hydrology, channel and watershed characteristics, riparian vegetation and ecosystem sensitivity of ephemeral streams in arid regions of the American Southwest.

Sutfin, N.; Shaw, J. R.; Wohl, E. E.; Cooper, D.

2012-12-01

263

Geomorphological characterization of endorheic basins in northern Chile  

NASA Astrophysics Data System (ADS)

Quantitative geomorphology regroups a large number of interesting tools to characterize natural basins across scales. The application of these tools to several river basins allows the description and comparison of geomorphological properties at different spatial scales as oppose to more traditional descriptors that are typically applied at a single scale, meaning the catchment scale. Most of the recent research using these quantitative geomorphological tools has focused on open catchments and no specific attention has been given to endorheic basins, and the possibility of having particular features that distinguish them from exorheic catchments. The main objective of our study is to characterize endorheic basins and investigate whether these special geomorphological features can be identified. Because scaling invariance is a widely observed and relatively well quantified property of open basins, it provides a suitable tool to characterize differences between the geomorphology of closed and open basins. Our investigation focuses on three closed basins located in northern Chile which describe well the diversity in the geomorphology and geology of this arid region. Results show that endhoreic basins exhibit different slope-area and flow paths sinuosity regimes compared to those observed in open basins. These differences are in agreement with the particular self-similar behavior across spatial scales of the Euclidean length of subcatchments, as well as the Hack's law and Horton's ratios. These regimes imply different physical processes inside the channel network regardless of the basin area, and they seem to be related to the endorheic character of these basins. The analysis of the probability density functions of contributing areas and lengths to the lower region shows that the hypothesis of self-similarity can also be applied to closed basins. Theoretical expressions for these distributions were derived and validated by the data. Future research will focus on (1) applying similar analyses in other locations and comparing the results, and (2) understanding and modeling the effects of groundwater in forming the landscape of these arid regions.

Dorsaz, J.; Gironas, J. A.; Escauriaza, C. R.; Rinaldo, A.

2011-12-01

264

Establishment of Populus deltoides under simulated alluvial groundwater declines  

USGS Publications Warehouse

Establishment, growth, and survival of seedlings of Populus deltoides subsp. monilifera (plains cottonwood) were examined in an experimental facility simulating five rates of declining alluvial groundwater. The treatments were permanent saturation, drawdown rates of 0.4, 0.7, 2.9 cm/d and immediate drainage. The experiment was conducted outdoors in planters near Fort Collins, Colorado. Seedling survival was highest under the two slowest drawdown rates and declined significantly with faster drawdown rates. The highest growth rate was associated with the drawdown rate of 0.4 cm/d, in which mean shoot height was 2.4 cm and mean root length was 39 am 98 days after planting. Growth of shoots and roots was reduced both by saturated conditions and by the more rapid drawdown rates of 0.7 and 2.9 cm/d. No establishment was observed in the immediate drawdown treatment. Whereas maximum biomass accumulation is associated with the most gradual drawdown or saturated conditions, seedling establishing naturally under such conditions are also most likely to be removed by ice or subsequent flooding. Seedlings establishing in higher topographic positions, in contrast, are subject to increased mortality and reduced shoot growth, resulting from reduced soil moisture. Rapid root extension following establishment allows P. deltoides seedlings to grow across a wide range of groundwater drawdown rates, and thus a variety of positions across a gradient of riparian soil moisture. Our results indicate that in coarse alluvial sands of low fertility, 47% of germinating P. deltoides seeds were able to survive in associated with a drawdown rate of 2.9 cm/d and a final water table depth of 80 cm.

Segelquist, Charles A.; Scott, Michael L.; Auble, Gregor T.

1993-01-01

265

Modeling Hydrological Impacts of Climate Change the Case of the Transboundary San Pedro Basin  

NASA Astrophysics Data System (ADS)

The US Southwest is an arid and semi-arid area where temporal and spatial variability have important impacts on water resources availability and management. Integrating this uncertainty into planning and decision making is a key issue, both for operation optimization and risk management strategies. A study in the San Pedro Basin, combining climatic data series analysis with climate change projection from global circulation models, aims at providing a basis for the inclusion of climatic scenarios into the Basin's decision and policy-making process. Changes in precipitation result in changes in mountain-front recharge. Long-term changes in the basin's water budget are assessed using existing hydrological models for the San Pedro Basin. An effort is made to clearly present a broad range of results corresponding to different scenarios for water managers and policy makers. This analysis will benefit the inclusion of a climatic component into the Decision Support System (DSS) model of the Upper San Pedro Basin.

Serrat-Capdevila, A.; Valdes, J. B.; Gonzalez, J.; Baird, K.; Mata, L. J.; Maddock, T., III

2006-12-01

266

Alluvial Fan Delineation from SAR and LIDAR-Derived Digital Elevation Models in the Philippines  

NASA Astrophysics Data System (ADS)

Occurrence of floods and debris flows leading to the formation of alluvial fans at the base of mountains naturally improve fertility of alluvial plains. However, these formations also have detrimental effects to communities within these zones like the case of Barangay (village) Andap, New Bataan, Compostela Valley where the whole village was wiped out by debris flow when it was hit by Supertyphoon Bopha in 2012. Hence, demarcating the boundaries of alluvial fans is crucial in disaster preparedness and mitigation. This study describes a method to delineate alluvial fans through contour maps from SAR and LiDAR-derived digital elevation models. Based on this data, we used hydrographic apex point polygons to plot the outflow points of upstream watersheds. The watershed and alluvial fan polygons were used to simulate debris flows in the study sites. The fans generated from the flood simulation were consistent with the polygons delineated from the digital elevation model. Satellite imagery and evidences of alluvial deposits found on site revealed 392 alluvial fans in the country. Widest among these is the sprawling 760 sq km fan identified in Cagayan Valley threatening about 434,329 persons at risk of debris flow. Other fans include those identified in Calapan, Mindoro (531 sq km), Kaliwanagan, Pangasinan (436 sq km), Pampanga Alluvial Fan (325 sq km), Mina, Iloilo (315 sq km), Lamsugod, S. Cotabato (286 sq km), in Tignaman, Oton and Alimodian in Iloilo (272 sq km), and the bajada, a series of alluvial fan coalescing to form a larger fan, identified in Ilocos Norte (218 sq km).

Aquino, D. T.; Ortiz, I.; Timbas, N.; Gacusan, R.; Montalbo, K.; Eco, R. C.; Lagmay, A.

2013-12-01

267

Residence Time of Sediments in Alluvial Plains from U-Th Isotope Analyses: The Ganges River System. (Invited)  

NASA Astrophysics Data System (ADS)

As illustrated in recent studies (Granet et al., 2007 ; 2010), the analysis of U-Th disequilibria in sediments collected along rivers allows the estimation of sediment transfer time in alluvial plains. Such an approach requires understanding the secondary processes which modify the U and Th isotopes of the sediments during their transfer within the plain. It also assumes a negligible contribution of new and fresh sediments coming from the erosion of the plain substratum during the sedimentary transfer. In order to specify these first results on the Ganges Basin river system, the main Himalayan tributaries of the Ganges were sampled at the exit of the Himalayan range and at the outlet of their watershed just before their confluence with the Ganges. In addition, at several sampling locations, suspended sedimentary load was collected at different depths of the water column. Our new data along with previously published data in (Granet et al., 2007 ; 2010) show that a wide range of variation in Th activity ratios in bedload and suspended sediments for several of these rivers. Such differences probably point to contrasting (geographical, geological, lithological, pedological..) origins of these two types of sediments. Furthermore, bedload and suspended load exhibit very different covariations of U and Th isotope ratios from upstream to downstream. These different trends of variations highlight the occurrence of different transfer histories within the plain for the coarse-grained and fine-grained sediments: 100 ky or more for the bedload sediments from the Himalayan range to the confluence with the Ganges, but much less for the suspended sediments. Variations in the U-Th isotope ratios of suspended sediments recorded for the same sampling location but at different seasons suggest that their transfer time could be as fast as one year. These data therefore confirm the real potential of U and Th isotopes in river sediments to constrain their transfer time within alluvial plain but also their origin. M. Granet et al. (2007) time-scales of sedimentary transfer and weathering processes from U-series nuclides: Clues from the Himalayan rivers, Earth and Planet. Sc. Let., 261, 389-406. Granet M et al. (2010) U-series disequilibria in suspended river sediments and implication for sediment transfer time in alluvial plains : the case of the Himalayan rivers Geochim. Cosmochim. Acta, 74, 2851-2865

Chabaux, F. J.; Blaes, E.; Granet, M.; Dosseto, A.; Stille, P.; France-Lanord, C.; Lupker, M.

2010-12-01

268

Stratigraphic architecture and quaternary evolution of the Val d'Agri intermontane basin (Southern Apennines, Italy)  

NASA Astrophysics Data System (ADS)

The sedimentary record of the Val d'Agri basin is of great importance for understanding the Quaternary tectonic activity and climatic variability in the Southern Apennines. Changes in tectonic controls, sediment supply and climatic input have been identified. The interval from ˜ 56 to ˜ 43 ka was associated with asymmetric subsidence restricted to the north-eastern actively faulted margin of the basin and development of axial braided river and transverse alluvial fan systems. Short-lasting Mediterranean-type pedogenesis between ˜ 43 and ˜ 32 ka (MIS Stage 3) coexisted with progradation-aggradation of the southern alluvial fan deposits and southwards tilting of the basin floor. Aggradation ended with consumption of accommodation space after 32 ka. During a subsequent stage of decline of vegetation cover, possibly as a consequence of climatic cooling (probably MIS Stage 2), active progradation of alluvial fans occurred. Breakthrough of the basin threshold and entrenchment of the drainage network must therefore be attributed to a latest Pleistocene to Holocene age. The first stages of basin opening and fill, predating ˜ 56 ka have only been inferred by stratigraphic considerations: the earliest lacustrine sedimentation should be middle Pleistocene or older in age. The following south-eastward basin widening allowed progradation of alluvial fan systems, which completely filled the lacustrine area (tentatively late middle Pleistocene). Pedogenesis in "Mediterranean-like" climate conditions caused the final development of a highly mature fersiallitic paleosol at the top of the fan surfaces, in areas of morpho-tectonic stability, plausibly during MIS Stage 5. The study results demonstrate the potential of applying a multidisciplinary approach in an intermontane continental settings marked by a relative rapid and constant tectonic subsidence and a high rate of sediment supply during the Pleistocene glacial-interglacial cycles.

Zembo, Irene

2010-01-01

269

Biology of Annual Plants in Arid and Semi-Arid Desert Regions of China  

Microsoft Academic Search

\\u000a Annual species are a major component of desert vegetation, with their unique traits playing a key role in vegetation restoration\\u000a in arid and semi-arid deserts. This chapter presents a systematic discussion of current research status and expectations of\\u000a future studies with respect to annual species in the deserts of China. To date, studies on annual species have been concerned\\u000a mainly

Xuehua Li

270

Applying animal behavior to arid rangeland mangement  

Technology Transfer Automated Retrieval System (TEKTRAN)

Livestock production is one of many demands placed on today’s arid rangelands. Therefore, understanding plant and animal biology and their effects on biotic and abiotic landscape components is fundamental if rangelands are to remain ecologically sustainable. One limiting factor to accomplishing posi...

271

Mountains and Arid Climates of Middle Latitudes  

Microsoft Academic Search

Simulations from a global climate model with and without orography have been used to investigate the role of mountains in maintaining extensive arid climates in middle latitudes of the Northern Hemisphere. Dry climates similar to those observed were simulated over central Asia and western interior North America in the experiment with mountains, whereas relatively moist climates were simulated in these

S. Manabe; A. J. Broccoli

1990-01-01

272

Geohydrologic framework of the Roswell ground-water basin, Chaves and Eddy Counties, New Mexico  

USGS Publications Warehouse

This report describes the geohydrology of the Roswell ground-water basin and shows the long-term hydrostatic-head changes in the aquifers. The Roswell ground-water basin consists of a carbonate artesian aquifer overlain by a leaky confining bed, which, in turn is overlain by an alluvial water-table aquifer. The water-table aquifer is hydraulically connected to the Pecos River. Ground-water pumpage from about 1,500 wells in the basin was about 378,000 acre-feet in 1978. Irrigation use on about 122,000 acres accounted for 95 percent of that pumpage.

Welder, G.E.

1983-01-01

273

Cyclic fluvial sedimentation in a rapidly subsiding basin, northwest Washington  

NASA Astrophysics Data System (ADS)

The Eocene Chuckanut Formation of northwest Washington comprises as much as 6000 m of alluvial strata and is one of the thickest nonmarine sequences in North America. The Bellingham Bay Member forms approximately the lower half of the Chuckanut Formation; it is characterized by repetitive fining-upward cycles consisting of a lower coarse-grained and an upper fine-grained member. Two types of cycle have similar vertical profiles but can be distinguished by the nature of their coarse member. Coarse members of the first type are thick (> 2-3 m), are commonly multi-storey, have apparent sheet geometry and are interpreted as the deposits of meandering-river channels and point bars. Coarse members of the second type are thinner (< 2-3 m), have apparent ribbon geometry and are interpreted as floodplain (crevasse?) channel deposits. Down-basin changes in the Bellingham Bay Member include a major decrease in grain size and an increase in fine-member thickness and cycle-recurrence interval. These changes reflect decreased flow competence and increased stability of channel banks. Similar trends might be found in other ancient alluvial sequences and could be useful in studies of both basin geometry and coal exploration. Sediment-accumulation rates are a minimum of 50 cm 1000 yrs -1, implying rapid subsidence. This subsidence probably had a major control on the sedimentation style of the Bellingham Bay Member, which resembles computer-generated models of alluvial stratigraphy at high subsidence rates (Allen, 1978).

Johnson, Samuel Y.

1984-03-01

274

30 CFR 912.822 - Special performance standards-operations in alluvial valley floors.  

Code of Federal Regulations, 2011 CFR

...RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE IDAHO § 912.822 Special performance standards—operations in alluvial valley floors. Part 822 of this chapter,...

2011-07-01

275

30 CFR 912.822 - Special performance standards-operations in alluvial valley floors.  

Code of Federal Regulations, 2014 CFR

...RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE IDAHO § 912.822 Special performance standards—operations in alluvial valley floors. Part 822 of this chapter,...

2014-07-01

276

Exploration of an alluvial aquifer in Oman by time-domain electromagnetic sounding  

NASA Astrophysics Data System (ADS)

One-third of the population of Oman depends upon groundwater extracted from the alluvium of the Batinah Plain, on the coast of the Gulf of Oman. Deep geophysical exploration techniques were used to determine the depth and nature of the alluvium and the boundaries of the aquifer. The base and structural controls of the alluvial basin at its contact with Tertiary marine sediments and Cretaceous ophiolite were mapped with seismic reflection data, recorded originally for oil exploration. The base of the alluvium dips northward from the foothills of the Northern Oman Mountains, reaching a maximum depth of 2000m at the coast. The varying facies of the alluvium are grossly characterised by different, overlapping ranges of electrical resistivity, depending largely on the clay content and degree of cementation. Resistivities near the coast are reduced by saline intrusion. These variations of resistivity were mapped with time-domain electromagnetic sounding along 400km of profile, to distinguish among the three zones of the alluvial aquifer. The wedge of saline intrusion was also delineated, up to 10km from the coast. The thickness of the saturated gravel aquifer ranges from 20-160m in an area greater than 600km2. Résumé Un tiers de la population d'Oman est alimenté par de l'eau souterraine pompée dans les alluvions de la plaine de Batinah, sur la côte du golfe d'Oman. Des techniques d'exploration géophysique profonde ont été mises en oeuvre pour déterminer la profondeur et la nature des alluvions et les limites de l'aquifère. La base et les contrôles structuraux du bassin alluvial au contact des sédiments marins tertiaires et des ophiolites crétacées ont été cartographiés à partir des données de sismique réflexion obtenues à l'origine pour la recherche pétrolière. La base des alluvions plonge vers le nord à partir du piémont du massif septentrional d'Oman, pour atteindre une profondeur maximale de 2000m sur la côte. Les divers faciès alluviaux sont grossièrement caractérisés par des différentes gammes de résistivitéélectrique se recouvrant, dépendant surtout de la teneur en argiles et du degré de cimentation. Les résistivités près de la côte diminuent du fait de l'intrusion marine. Ces variations de résistivité ont été cartographiées à partir de 400km de profils électromagnétiques, dans le domaine temporel ; trois zones ont été distinguées dans l'aquifère alluvial. Le biseau salé a aussi été délimité, jusqu'à 10km de la côte. L'épaisseur de la partie saturée des graviers va de 20-160m sur une étendue supérieure à 600km2. Resumen Un tercio de la población de Omán depende de las aguas subterráneas extraídas del aluvial de la Llanura de Batinah, en la costa del Golfo de Omán. Para determinar la profundidad y naturaleza del aluvial, así como los límites del acuífero, se han usado técnicas de exploración geofísica profunda. El basamento y los límites estructurales del aluvial en su contacto con los sedimentos marinos del Terciario y la ofiolita cretácica se obtuvieron mediante sísmica de reflexión, registrada previamente en campañas de exploración petrolífera. La base del aluvial buza hacia el norte desde el pie de las Montañas del Norte de Omán, alcanzando una profundidad máxima de 2000m en la costa. Las distintas facies del aluvial están caracterizadas por rangos distintos, pero superpuestos, de resistividad eléctrica, dependiendo del contenido en arcillas y del grado de cementación. Las resistividades cerca de la costa se reducen por la intrusión salina. Estas variaciones de resistividad se obtuvieron con registros electromagnéticos a lo largo de un perfil de 400km, con el objetivo de distinguir las tres zonas del acuífero aluvial. También se pudo obtener la geometría de la cuña de intrusión, que llega hasta 10km de la costa. El espesor de las gravas saturadas que forman el acuífero oscila entre los 20-160m en un área superior a 600km2.

Young, M. E.; de Bruijn, R. G. M.; Al-Ismaily, A. Salim

277

Magnetic properties of alluvial soils polluted with heavy metals  

NASA Astrophysics Data System (ADS)

Magnetic properties of soils, reflecting mineralogy, concentration and grain-size distribution of Fe-oxides, proved to be useful tool in assessing the soil properties in terms of various environmental conditions. Measurement of soil magnetic properties presents a convenient method to investigate the natural environmental changes in soils as well as the anthropogenic pollution of soils with several risk elements. The effect of fluvial pollution with Cd, Cu, Pb and Zn on magnetic soil properties was studied on highly contaminated alluvial soils from the mining/smelting district (P?íbram; CZ) using a combination of magnetic and geochemical methods. The basic soil characteristics, the content of heavy metals, oxalate, and dithionite extractable iron were determined in selected soil samples. Soil profiles were sampled using HUMAX soil corer and the magnetic susceptibility was measured in situ, further detailed magnetic analyses of selected distinct layers were carried out. Two types of variations of magnetic properties in soil profiles were observed corresponding to indentified soil types (Fluvisols, and Gleyic Fluvisols). Significantly higher values of topsoil magnetic susceptibility compared to underlying soil are accompanied with high concentration of heavy metals. Sequential extraction analysis proved the binding of Pb, Zn and Cd in Fe and Mn oxides. Concentration and size-dependent parameters (anhysteretic and isothermal magnetization) were measured on bulk samples in terms of assessing the origin of magnetic components. The results enabled to distinguish clearly topsoil layers enhanced with heavy metals from subsoil samples. The dominance of particles with pseudo-single domain behavior in topsoil and paramagnetic/antiferromagnetic contribution in subsoil were observed. These measurements were verified with room temperature hysteresis measurement carried out on bulk samples and magnetic extracts. Thermomagnetic analysis of magnetic susceptibility measured on magnetic extracts indicated the presence of magnetite/maghemite in the uppermost layers, and strong mineralogical transformation of iron oxyhydroxides during heating. Magnetic techniques give valuable information about the soil Fe oxides, which are useful for investigation of the environmental effects in soil. Key words: magnetic methods, Fe oxides, pollution, alluvial soils.

Dlouha, S.; Petrovsky, E.; Boruvka, L.; Kapicka, A.; Grison, H.

2012-04-01

278

Engineering geologic feasibility of lignite mining in alluvial valleys by hydraulic dredging methods  

E-print Network

ENGINEERING GEOLOGIC FEASIBILITY OF LIGNITE MINING IN ALLUVIAL VALLEYS BY HYDRAULIC DREDGING METHODS A Thesis by CYNTHIA LYNN CASON Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirement... for the degree of MASTER OF SCIENCE May 1982 Niajor Subject: Geology ENGINEERING GEOLOGIC FEASIBILITY OF LIGNITE MINING IN ALLUVIAL VALLEYS BY HYDRAULIC DREDGING METHODS A Thesis by CYNTHIA LYNN CASON Approved as to style and content by: (Chairman...

Cason, Cynthia Lynn

1982-01-01

279

Late Holocene upper bounds of flood magnitudes and twentieth century large floods in the ungauged, hyperarid alluvial Nahal Arava, Israel  

NASA Astrophysics Data System (ADS)

The impact of large twentieth century floods on the riparian vegetation and channel morphology of the relatively wide anabranching and braided Nahal Arava, southern Israel, was documented as part of developing tools to (a) identify recent large floods, (b) determine these flood's respective magnitudes in alluvial ungauged streams, and (c) determine long-term upper bounds to flood stages and magnitudes. Along most of its course Nahal Paran, a major tributary that impacts the morphology, floods and sediments of Nahal Arava at the study reach, is a coarse-gravel, braided ephemeral stream. Downstream of the Arava-Paran confluence, aeolian and fluvial sand delivered from eastern Arava valley alters the channel morphology. The sand has accreted up to 2.5 m above the distinct current channels, facilitating the recording of large floods. This sand enhances the establishment of denser riparian vegetation (mainly Tamarix nilotica and Haloxylon persicum) that interacts with floods and affects stream morphology. A temporal association was found between specific floods recorded upstream and tree-ring ages of re-growth of flood-damaged tamarix trees ('Sigafoos trees') in the past 30 years. This association can be utilized for developing a twentieth century flood chronology in hyperarid ungauged basins in the region. The minimum magnitude of the largest flood that covered the entire channel width, estimated from flood deposits, is approximately 1700-1800 m 3s - 1 . This is a larger magnitude than the largest gauged flood of 1150 m 3s - 1 that occurred in 1970 about 30 km upstream in Nahal Paran. Our estimation agrees with flood magnitude estimated from the regional envelope curve of the largest floods. Based on Holocene alluvial stratigraphy and OSL dating in the study reach we also conclude that flood stages did not reach the late Holocene (˜ 2.2 ka) surface and therefore we estimate a non-exceedance upper bound of ˜ 2000 m 3s - 1 flood magnitudes for Nahal Arava during that interval. This study indicates that in unfavorable areas the combination of hydrology, fluvial morphology and botanic evidence can increase our understanding of ungauged basins and give information crucial for hydrology planning.

Jacoby, Yael; Grodek, Tamir; Enzel, Yehouda; Porat, Naomi; McDonald, Eric V.; Dahan, Ofer

2008-03-01

280

Debris-flow deposits in an alluvial-plain succession: The upper Triassic Callide coal measures of Queensland, Australia  

SciTech Connect

The Carnian-Rhaetian Callide Coal Measures are preserved in a small (22.5 km by 8 km), partially fault-bounded basin remnant in east-central Queensland, Australia. The <150 m thick coal-measure succession is interpreted to have accumulated during a phase of mild crustal extension that formed a series of discrete, intermontane basins in eastern Australia. The succession fines upward from a conglomerate-rich lower part into a finer-grained and coal-bearing upper section (including coal seams <34 m thick), and is interpreted as the deposits of an alluvial-plain environment. Anomalous, matrix-rich diamictites, breccias, and conglomerates have been recognized within the succession at several localities, in many cases interbedded with coals. These are interpreted as the product of debris flows. Two debris-flow lithofacies are recognized: (1) mixtures of fine carbonaceous material, clay, silt, sand, gravel, and volcaniclastic debris, and (2) breccias consisting principally of coal clasts in a coaly matrix with minor clastic and volcaniclastic debris. The distribution of debris flows in the Callide Coal Measures shows a coincidence with mapped faults and interpreted structural lineaments. The debris flows may have been triggered by fault movements, which formed rupture topography on the flat alluvial plain, and caused destabilization of water-saturated clastic and organic sediments. Some debris-flow bodies may have been mounded, such that subsequent peat formation was restricted until those bodies were buried. The preservation of debris-flow units at different stratigraphic levels along mapped structures suggests multiple paleoseismic events or multiple debris-flow units at different stratigraphic levels along mapped structures suggests multiple paleoseismic events or multiple debris-flow events along those structures. The mixing of volcaniclastic debris into debris-flow facies suggests that seismic events were coincident with (or perhaps caused by) nearby, explosive volcanic activity. The close relationship between debris-flow deposits and thick coal bodies on the inferred downthrown sides of faults at Callide further suggests that periodic, tectonic subsidence may have facilitated thick coal accumulation.

Jorgensen, P.J.; Fielding, C.R. [Univ. of Queensland, Brisbane (Australia). Dept. of Earth Sciences

1999-09-01

281

Water and Arid Lands of the Western United States  

NASA Astrophysics Data System (ADS)

Despite impressive innovations by some states, western water laws and institutions now in place were designed chiefly for an earlier era and have not adapted to the new demands and stresses on water resources. In Water and the Arid Lands of the Western United States the authors explore the nature of water demands in the agricultural and municipal sectors and set forth prescriptions for the west to move away from its historical reliance on expensive supply-side projects and toward better management of existing supplies. Six cases studies by experts in the field illustrate specific examples of water management issues. Taking as foci the Central Valley of California, the High Plains of Texas, and the Upper Basin of the Colorado River, three of the case studies examine problems faced by the large urban areas of southern California; Tucson, Arizona; and Denver, Colorado. A concluding chapter suggests practical policy options and politically feasible institutional changes for maximizing the efficiency of water use and minimizing the conflict associated with the reallocation of limited water supplies.

El-Ashry, Mohamed T.; Gibbons, Diana C.

1988-09-01

282

Landscape ecological risk assessment study in arid land  

NASA Astrophysics Data System (ADS)

The ecosystem risk assessment is an essential decision making system for predicting the reconstruction and recovery of a damaged ecosystem after intensive mankind activities. The sustainability of environment and resources of the lake ecosystem in arid districts have been paid close attention to by international communities as well as numerous experts and scholars. The ecological risk assessment offered a scientific foundation for making the decision and execution of ecological risk management. Bosten Lake, the largest inland freshwater lake in China, is the main water source of the industrial and agricultural production as well as the local residence in Yanqi basin, Kuara city and Yuri County in the southern Xinjiang. Bosten Lake also provides a direct water source for emergency transportation in the Lower Reaches of Tarim River. However, with the intensive utilizations of water and soil resources, the environmental condition in the Bosten Lake has become more and more serious. In this study, the theory and method of landscape ecological risk assessment has been practiced using 3S technologies combined with the frontier theory of landscape ecology. Defining the mainly risk resource including flood, drought, water pollution and rich nutrition of water has been evaluated based on the ecosystem risk assessment system. The main process includes five stages: regional natural resources analysis, risk receptor selection, risk sources evaluation, exposure and hazard analysis, and integrated risk assessment. Based on the risk assessment results, the environmental risk management countermeasure has been determined.

Gong, Lu; Amut, Aniwaer; Shi, Qingdong; Wang, Gary Z.

2007-09-01

283

Floodplain biogeochemical mosaics: A multidimensional view of alluvial soils  

NASA Astrophysics Data System (ADS)

alluvial floodplains of large rivers are exceptionally productive and dynamic ecosystems, characterized by a complex mosaic of vegetation at different successional stages overlying soils sorted by historic floods. Natural floodplains are widely credited with efficiently removing nitrogen from surface waters and accumulating carbon in biomass, yet very little floodplain research has examined carbon and nitrogen cycling below surficial soils. We evaluated the extent to which vegetation cover could be used to predict subsurface carbon and nitrogen dynamics and to estimate whole-floodplain carbon storage and denitrification rates. We dug soil pits under three dominant vegetation communities on a gravel-bedded floodplain in northwest Montana to the depth of the permanent water table (1-3 m). We compared depth profiles of total and dissolved carbon (C) and nitrogen (N), denitrification potentials (DEAs), organic particulates, moisture, and pH across vegetation types. Near-surface soils (0-10 cm) of forests had larger C and N pools and DEAs than grasslands or gravel bars, but such vegetation effects dissipated within the upper ~50 cm of soil. At depth, spatial heterogeneity in carbon and nitrogen pools and fluxes depended instead on soil texture, and relatively high rates of DEA and carbon storage were measured in zones of buried organic debris. Although C storage and denitrification potential are generally low in subsurface soils, these deep soils might nonetheless contribute substantially to whole-floodplain C storage and denitrification because of their large volume, high hydrologic connectivity, and heterogeneous biogeochemistry.

Appling, Alison P.; Bernhardt, Emily S.; Stanford, Jack A.

2014-08-01

284

Diazotrophy in Alluvial Meadows of Subarctic River Systems  

PubMed Central

There is currently limited understanding of the contribution of biological N2 fixation (diazotrophy) to the N budget of large river systems. This natural source of N in boreal river systems may partially explain the sustained productivity of river floodplains in Northern Europe where winter fodder was harvested for centuries without fertilizer amendments. In much of the world, anthropogenic pollution and river regulation have nearly eliminated opportunities to study natural processes that shaped early nutrient dynamics of large river systems; however, pristine conditions in northern Fennoscandia allow for the retrospective evaluation of key biochemical processes of historical significance. We investigated biological N2 fixation (diazotrophy) as a potential source of nitrogen fertility at 71 independent floodplain sites along 10 rivers and conducted seasonal and intensive analyses at a subset of these sites. Biological N2 fixation occurred in all floodplains, averaged 24.5 kg N ha?1 yr?1 and was down regulated from over 60 kg N ha?1 yr?1 to 0 kg N ha?1 yr?1 by river N pollution. A diversity of N2-fixing cyanobacteria was found to colonize surface detritus in the floodplains. The data provide evidence for N2 fixation to be a fundamental source of new N that may have sustained fertility at alluvial sites along subarctic rivers. Such data may have implications for the interpretation of ancient agricultural development and the design of contemporary low-input agroecosystems. PMID:24223119

DeLuca, Thomas H.; Zackrisson, Olle; Bergman, Ingela; Díez, Beatriz; Bergman, Birgitta

2013-01-01

285

Age-dating volcanic and alluvial surfaces with multipolarization data  

NASA Technical Reports Server (NTRS)

A false-color multipolarization version of one of the images of Owens Valley area acquired by the JPL Synthetic Aperture Radar (SAR) is given. A geologic map of the alluvial fans there (Gillespie, 1982) is also given for comparison. In general, brightness in the multipolarization images can be seen to be inversely proportional to the age of the surfaces. A more detailed investigation of the relationship between backscatter and age of the surfaces was undertaken with calibrated aircraft SAR data. The quantitative relationship between backscatter coefficient and age for the three polarizations is shown. The straight lines connecting the measured data points imply a steady-state process, although the process or processes leading to this relationship may have operated at rates that varied with climate fluctuations, such as the glacial ages. It is expected that the relationship between radar brightness and age is a consistent one, and that with the wider availability of calibrated radar backscatter data, these relationships can be less well-known areas. The effect of variable such as past climate fluctuations, tectonic disturbance, and rock type must be understood before extension beyond the Mojave Desert region can be attempted.

Farr, T. G.

1985-01-01

286

Semi-Arid Aquifer Responses to Forest Restoration Treatments and Climate Change.  

PubMed

The purpose of this study was to develop an interpretive groundwater-flow model to assess the impacts that planned forest restoration treatments and anticipated climate change will have on large regional, deep (>400?m), semi-arid aquifers. Simulations were conducted to examine how tree basal area reductions impact groundwater recharge from historic conditions to 2099. Novel spatial analyses were conducted to determine areas and rates of potential increases in groundwater recharge. Changes in recharge were applied to the model by identifying zones of basal area reduction from planned forest restoration treatments and applying recharge-change factors to these zones. Over a 10-year period of forest restoration treatment, a 2.8% increase in recharge to one adjacent groundwater basin (the Verde Valley sub-basin) was estimated, compared to conditions that existed from 2000 to 2005. However, this increase in recharge was assumed to quickly decline after treatment due to regrowth of vegetation and forest underbrush and their associated increased evapotranspiration. Furthermore, simulated increases in groundwater recharge were masked by decreases in water levels, stream baseflow, and groundwater storage resulting from surface water diversions and groundwater pumping. These results indicate that there is an imbalance between water supply and demand in this regional, semi-arid aquifer. Current water management practices may not be sustainable into the far future and comprehensive action should be taken to minimize this water budget imbalance. PMID:24665998

Wyatt, Clinton J W; O'Donnell, Frances C; Springer, Abraham E

2014-03-25

287

Vertical carbon-14 profiles for resolving spatial variability in recharge in arid environments  

NASA Astrophysics Data System (ADS)

Groundwater age tracers are often measured to help constrain estimates of groundwater recharge, especially in arid environments where other methods are unsuitable. However multiple processes can influence the shape of vertical tracer profiles in an aquifer including (1) variation in tracer input concentrations from the unsaturated zone, (2) the role of diffusion in transporting tracer into the aquifer when fluxes are low and (3) spatial variability in recharge. This study demonstrates the influence of spatially variable recharge and spatially variable carbon-14 (14C) activities in the unsaturated zone on vertical 14C profiles in groundwater. Through groundwater flow and solute transport modelling, we demonstrate that recharge estimated from single point measurements of 14C may be wrong more than an order of magnitude when unsaturated zone 14C activities and recharge vary spatially. We then present a case study from the Ti Tree Basin in arid central Australia, where detailed profiles of 14C activity in unsaturated zone gas and groundwater have been measured, and spatial variability in unsaturated zone 14C is observed (ranging from 54 to 106 pMC above the watertable). Through modelling our data, we show that when unsaturated zone 14C activities are known, measurement of the 14C profile can help constrain estimates of recharge and its spatial variability. This approach improves our understanding of groundwater flow in the Ti Tree Basin, by showing mountain front recharge to be an important mechanism.

Wood, Cameron; Cook, Peter G.; Harrington, Glenn A.

2015-01-01

288

Guatemalan forest synthesis after Pleistocene aridity  

PubMed Central

Sediments from two lakes in the Peten Department, Guatemala, provide palynological evidence from Central America of late Pleistocene aridity and subsequent synthesis of mesic forests. Late Glacial vegetation consisted of marsh, savanna, and juniper scrub. An early Holocene temperate forest preceded a mesic tropical forest with Brosimum (ramon). Thus “primeval” rain forests of Guatemala are no older than 10,000 to 11,000 years and are considerably younger in the Peten due to Mayan disturbances. Among dated Neotropical sites, the Peten has the most mesic vegetation yet shown to have supplanted xeric vegetation present during the Pleistocene. The arid late Glacial-humid early Holocene transition appears to have been pantropical in the lowlands. The Peten was not a Pleistocene refugium for mesophytic taxa, as has been suggested. Thus genesis of extant rain forests in northern Central America and southern Mexico remains unexplained. Images PMID:16593498

Leyden, Barbara W.

1984-01-01

289

Latest Carboniferous-earliest Permian transgressive deposits in the Paganzo Basin of western Argentina: Lithofacies and sequence stratigraphy of a coastal-plain to bay succession  

NASA Astrophysics Data System (ADS)

The upper Paleozoic rocks of Gondwana record a complex paleoclimatic history related to the migration of the supercontinent over high latitudes. Changes in climate and relative sea level can be traced through detailed sedimentologic and sequence-stratigraphic analysis. Our study focuses on transgressive deposits of Stephanian-Early Permian age in the lower member of the Tupe Formation with the objective of characterizing lithofacies and sedimentary environments within a sequence-stratigraphic framework in order to achieve a better understanding of the sedimentary history of the Paganzo Basin and the nature of transgressive deposits. Sixteen lithofacies grouped in eight assemblages were defined and arranged in two complete sequences. A sequence boundary (SB) is identified at the base of the Tupe Formation. Coastal-plain deposits capped by marine embayment lithofacies are included within sequence 1. A relative sea-level fall (SB) is recorded by an abrupt change into braided alluvial-plaine deposits (LST). The beginning of the TST is characterized by the appearance of coal and deltaic lithofacies. Late TST deposits occur above a ravinement surface and comprise bay-margin to distal-bay deposits forming a retrogradational stacking package. These lithofacies are replaced upwards by HST deposits. A relative sea-level fall (SB) is recorded by the presence of fluvial deposits overlying marine lithofacies. The Tupe Formation illustrates the transition of a coastal-plain to a marine embayment. The detection of a transgressive surface within the coastal-plain deposits of sequence 1 expanded significantly the volume of deposits now included as part of the latest Carboniferous-earliest Permian transgression, and underscores the importance of searching for transgressive signatures in non-marine environments. The presence of two sequences supports a punctuated shoreline trajectory with an overall retrogradational stacking pattern. An abrupt relative sea-level fall and increased aridity is recorded at the end of the transgressive event.

Desjardins, Patricio R.; Buatois, Luis A.; Limarino, Carlos O.; Cisterna, Gabriela A.

2009-07-01

290

Lower Palaeozoic Alluvial Systems: The Sedimentological Impact of Evolving Vegetation in Terrestrial Environments  

NASA Astrophysics Data System (ADS)

In present-day alluvial environments, the impact of vegetation on sedimentological processes and deposits is well known. A vegetated catchment may decrease sediment yield, sediment erodability, Hortonian overland flow, aeolian winnowing of fines, the proportion of sediment transported as bedload, may increase bank stability, infiltration into substrates, bed roughness, and can promote the production of chemically-weathered clays and soils and the adoption of a meandering style. It is generally understood that, prior to the evolution of terrestrial vegetation during the Lower Palaeozoic, ancient alluvial systems were markedly different from modern systems, with many systems adopting a "sheet-braided" style. This understanding has previously informed the interpretations of many Precambrian pre-vegetation alluvial successions, but there has been relatively little work regarding Lower Palaeozoic alluvial successions that existed during the active terrestrialization of plants. In this study, a comprehensive review of 141 Cambrian to Devonian alluvial successions documented in published literature was combined with original field data from 20 alluvial successions from across Europe and North America, in order to identify changes in the sedimentary style of alluvial strata while vegetation was evolving and colonizing alluvial environments. This approach has established clear trends indicating an increase in mudrocks and sandstone maturity and a decrease in overall sand grain size through the Lower Palaeozoic, suggesting that primitive vegetation cover was able to promote the production and preservation of muds and increase the residence time of sand-grade sediment (and thus sediment reworking) in alluvial systems. It has also enabled the first stratigraphic occurrence of certain vegetation-dependent sedimentary features to be pinpointed and tied directly to the onset of specific evolutionary adaptations recorded in the palaeobotanical fossil record. As such, the first markedly heterolithic alluvial sequences can be shown to first appear at the same time as the most primitive terrestrial vegetation in the Lower Ordovician, whilst pedogenic calcite first appears in the rock record at the same time as vascular plants in the Lower Silurian. Vertisols, coal, and certain indicators of meandering fluvial style (lateral accretion surfaces) only appear after the development of plant arborescence and deep rooting in the Devonian.

Davies, N. S.; Gibling, M. R.

2009-04-01

291

Cambrian to Devonian evolution of alluvial systems: The sedimentological impact of the earliest land plants  

NASA Astrophysics Data System (ADS)

In present-day alluvial environments, the impact of vegetation on sedimentological processes and deposits is well known. A vegetated catchment may decrease sediment yield, sediment erodibility, Hortonian overland flow, aeolian winnowing of fines, the proportion of sediment transported as bedload, and may increase bank stability, infiltration into substrates, and bed roughness. Vegetation also promotes the production of chemically-weathered clays and soils and the adoption of a meandering style. It is generally understood that, prior to the evolution of terrestrial vegetation during the Early Palaeozoic, ancient alluvial systems were markedly different from modern systems, with many systems adopting a "sheet-braided" style. This understanding has previously informed the interpretations of many Precambrian pre-vegetation alluvial successions, but there has been relatively little work regarding Early Palaeozoic alluvial successions laid down prior to and during the initial colonization of the Earth's surface by plants. A comprehensive review of 144 Cambrian to Devonian alluvial successions documented in published literature was combined with original field data from 34 alluvial successions across Europe and North America. The study was designed to identify changes in alluvial style during the period that vegetation was evolving and first colonizing alluvial environments. An increase in mudrock proportion and sandstone maturity is apparent, along with a decrease in overall sand grain size through the Early Palaeozoic. These trends suggest that primitive vegetation cover promoted the production and preservation of muds from the mid Ordovician onwards and increased the residence time of sand-grade sediment in alluvial systems. The compilation also enables the first stratigraphic occurrence of certain vegetation-dependent sedimentary features to be pinpointed and related to the evolution of specific palaeobotanical adaptations. The first markedly heterolithic alluvial sequences appeared at about the same time as the most primitive terrestrial vegetation in the Ordovician, and prolific pedogenic calcite, charcoal and bioturbated floodplain fines first appeared in the rock record at about the same time as vascular-plant macrofossils became abundant in the late Silurian. Lateral accretion sets in channel deposits appeared near the Silurian-Devonian boundary, at or shortly before the appearance of underground rooting systems, and become progressively more abundant in the record during the Devonian, implying a major expansion of meandering rivers as rooted plants stabilized river banks. Coals become abundant after the development of plant arborescence. The analysis suggests that the evolution of embryophytes had a profound effect on fluvial processes and deposits, and this period of landscape evolution must be considered amongst the most significant environmental and geomorphological changes in Earth history, with profound consequences for all aspects of the Earth system.

Davies, Neil S.; Gibling, Martin R.

2010-02-01

292

Heating degree–days for arid regions  

Microsoft Academic Search

Arid regions generally have great temperature differences between day and night. Heating degree–days are indicative of the need to heat buildings. We show that the maximum and minimum temperatures are linearly related at high significance levels. Degree–day calculations using only maximum temperature records are presented and risk assessments are explained. Regional variations of monthly degree–days are mapped and their relations

Zekai ?en

1998-01-01

293

VOCs in Arid soils: Technology summary  

SciTech Connect

The Volatile Organic Compounds In Arid Soils Integrated Demonstration (VOC-Arid ID) focuses on technologies to clean up volatile organic compounds and associated contaminants in soil and groundwater at arid sites. The initial host site is the 200 West Area at DOE`s Hanford site in southeastern Washington state. The primary VOC contaminant is carbon tetrachloride, in association with heavy metals and radionuclides. An estimated 580--920 metric tons of carbon tetrachloride were disposed of between 1955 and 1973, resulting in extensive soil and groundwater contamination. The VOC-Arid ID schedule has been divided into three phases of implementation. The phased approach provides for: rapid transfer of technologies to the Environmental Restoration (EM-40) programs once demonstrated; logical progression in the complexity of demonstrations based on improved understanding of the VOC problem; and leveraging of the host site EM-40 activities to reduce the overall cost of the demonstrations. During FY92 and FY93, the primary technology demonstrations within the ID were leveraged with an ongoing expedited response action at the Hanford 200 West Area, which is directed at vapor extraction of VOCs from the vadose (unsaturated) zone. Demonstration efforts are underway in the areas of subsurface characterization including: drilling and access improvements, off-gas and borehole monitoring of vadose zone VOC concentrations to aid in soil vapor extraction performance evaluation, and treatment of VOC-contaminated off-gas. These current demonstration efforts constitute Phase 1 of the ID and, because of the ongoing vadose zone ERA, can result in immediate transfer of successful technologies to EM-40.

Not Available

1994-02-01

294

Patterns of human occupation during the early Holocene in the Central Ebro Basin (NE Spain) in response to the 8.2 ka climatic event  

Microsoft Academic Search

The Central Ebro River Basin (NE Spain) is the most northern area of truly semi-arid Mediterranean climate in Europe and prehistoric human occupation there has been strongly influenced by this extreme environmental condition. Modern climate conditions single out this region due to the harsh environment, characterised by the highest absolute summer temperatures of the Ebro River Basin. The Bajo Aragón

P. González-Sampériz; P. Utrilla; C. Mazo; B. Valero-Garcés; Mc. Sopena; M. Morellón; M. Sebastián; A. Moreno; M. Martínez-Bea

2009-01-01

295

Hydrologic and Soil Science in a Mediterranean Critical Zone Observatory: Koiliaris River Basin  

NASA Astrophysics Data System (ADS)

The Koiliaris River watershed is situated 25km east from the city of Chania, Crete, Greece. The total watershed area is 145km2 and the main supply of water originates in the White Mountains. At high elevations (altitude 2014 m), the maximum slope is 43% while at the lower elevations the slope measures 1-2%. Land use includes heterogeneous agricultural areas (25.4%), olive and orange groves (15.6%), and scrub and/or herbaceous vegetation associations (57.6%). The geology of the Basin consists of 23.8% Plattenkalk (dolomites, marbles, limestone and re-crystallized limestone with cherts); 31% of Trypali units (re-crystallized calcaric breccias); 9.4% limestones with marls in Neogene formations; 13% marls in Neogene formations; 12.8% schists, and 10% quaternary alluvial deposits. Intensive hydrologic and geochemical monitoring has been conducted since 2004 while the site has historical data since the ‘60s. In addition, a telemetric high-frequency hydrologic and water quality monitoring station has been deployed to obtain data for the characterization of the hydrologic and biogeochemical processes with varying process response-times. Hydrologic and geochemical modeling confirms the estimation of characteristic times of these processes. The main type of soil degradation in the basin as well as in other arid and semi-arid regions is water erosion, which is due to the clearing of forests and natural vegetation for cropping and livestock grazing. De-vegetation and inappropriate cultivation practices induces soil organic matter (SOM) losses making soils susceptible to erosion and desertification with global consequences for food security, climate change, biodiversity, water quality, and agricultural economy. Cropland plowing breaks-up water stable aggregates making the bio-available pool bio-accessible; which could be microbially attacked and oxidized resulting in SOM decline. Chronosequence data analysis suggested first-order kinetic rate of decline of the bio-available carbon and nitrogen pools, where as much as half of the total OM loss could take place during the first year after the conversion of grassland to cropland. We have shown by physical fractionation and spectroscopic techniques in croplands and set-aside fields that most of the SOM decline in croplands has been attributed to the breakup of macroaggregates and the oxidation of particulate organic matter despite the climatic or textural conditions. However, lower decomposition rates and higher silt-clay content of Greek soil create more stable aggregates and facilitate OM stabilization. Studies on Koiliaris River highland de-vegetated grazing lands suggested decline of soil biochemical quality compared to native vegetated lands. The size of soluble mineral nitrogen and organic carbon pools have also decreased. The composition of the soluble OM pool had significantly lower DOC aromaticity and was nitrogen enriched compared with the naturally vegetated lands. The DON Aromaticity Index was shown to be a promising sensitive indicator of de-vegetation effect on the soluble pool of OM. The partitioning coefficients of the potential soluble organic nitrogen increased with increasing DON aromaticity for the de-vegetated lands, indicating that the lower the aromaticity, the more prone soils are to leaching DON and potentially affect water quality. The land-use load apportionment analysis revealed that the river export load of dissolved organic nitrogen (DON) is linearly correlated with the normalized, livestock derived, DON load input from pasture suggesting that increasing livestock grazing in a watershed would result in higher DON export in river. DON aromaticity could serve as a simple indicator of soil biochemical quality and aggregate disturbance in soils and therefore SOM stability. We have conducted a stratified soil sampling intending to validate the utility of the examined indices for the quantification of the effects of agricultural pressures to soil quality and the detection of potential effects on water quality. The watershed is one of the Critical Zone Observator

Nikolaidis, Nikolaos; Stamati, Fotini; Schnoor, Jerald; Moraetis, Daniel; Kotronakis, Manolis

2010-05-01

296

Temperature as a tracer to identify surface water-groundwater exchanges in the Heihe River Basin, northwest China  

NASA Astrophysics Data System (ADS)

The Heihe River Basin (HRB) is the second largest inland river basin in the arid region of northwestern China. Under natural conditions, the Heihe River recharges to groundwater in the piedmont areas after coming out of the Qilian Mountains. In the front edge of the alluvial and fluvial fans in the middle HRB, groundwater discharges to the surface in the form of springs and then flows into the Heihe River and ends up at the terminal lakes in the lower HRB. The surface water-groundwater interactions are frequent and dynamic along the Heihe River, and the understanding of these interactions is essential for conjunctive use and management of water resources and is fundamental to ensuring ecosystem health of the HRB. Among the various methods used to study surface water-groundwater interactions, those based on temperature have some distinct advantages because of the obvious temperature differences between surface water and groundwater and also because of the simplicity and low cost of temperature measurement. Fiber-optic distributed temperature sensing (DTS) can measure temperature at very high spatial and temporal resolutions and has led to important insights into the processes of groundwater and surface water interactions. In this study, DTS was applied to measure high-resolution temperature variations in the river water with a 0.25 m spatial interval and a 15 minute temporal frequency in a total distance of 5 km along two sections of the Heihe River. A statistical approach was used to discern the spatial distribution and the size of groundwater discharge zones and hyporheic zones, respectively. The exchange flux was then estimated using 1-D hydrodynamic model, which calculates the inflow flux in the study area by comparing the simulated temperatures with the measured ones. In addition, temperature data, combined with more traditional hydrological data such as hydraulic heads and fluxes, can provide independent constraints for calibrating the coupled surface water-groundwater model. This study utilized the airborne thermal-infrared (TIR) remote sensing method to obtain the pattern of temperature changes on the river surface in the middle HRB. The TIR sensed temperatures were compared with the simultaneous ground observations and the two showed a good match. The distribution and variation pattern of temperature anomalies were identified, thus providing an effective means of locating groundwater discharge areas. This information can be further compared with the simulated groundwater discharge areas by the integrated surface water-groundwater model to improve the model calibration over a regional scale.

Liu, J.; Yao, Y.; Liu, C.; Xiao, H.; Zheng, C.; Li, W.

2013-12-01

297

Geotechnical Parameters of Alluvial Soils from in-situ Tests  

NASA Astrophysics Data System (ADS)

The article concentrates on the identification of geotechnical parameters of alluvial soil represented by silts found near Poznan and Elblag. Strength and deformation parameters of the subsoil tested were identified by the CPTU (static penetration) and SDMT (dilatometric) methods, as well as by the vane test (VT). Geotechnical parameters of the subsoil were analysed with a view to using the soil as an earth construction material and as a foundation for buildings constructed on the grounds tested. The article includes an analysis of the overconsolidation process of the soil tested and a formula for the identification of the overconsolidation ratio OCR. Equation 9 reflects the relation between the undrained shear strength and plasticity of the silts analyzed and the OCR value. The analysis resulted in the determination of the Nkt coefficient, which might be used to identify the undrained shear strength of both sediments tested. On the basis of a detailed analysis of changes in terms of the constrained oedometric modulus M0, the relations between the said modulus, the liquidity index and the OCR value were identified. Mayne's formula (1995) was used to determine the M0 modulus from the CPTU test. The usefullness of the sediments found near Poznan as an earth construction material was analysed after their structure had been destroyed and compacted with a Proctor apparatus. In cases of samples characterised by different water content and soil particle density, the analysis of changes in terms of cohesion and the internal friction angle proved that these parameters are influenced by the soil phase composition (Fig. 18 and 19). On the basis of the tests, it was concluded that the most desirable shear strength parameters are achieved when the silt is compacted below the optimum water content.

M?ynarek, Zbigniew; Stefaniak, Katarzyna; Wierzbicki, Jedrzej

2012-10-01

298

Comparison of different investigation methods to characterise alluvial gravel aquifers  

NASA Astrophysics Data System (ADS)

For reliable groundwater transport modelling of unconsolidated porous aquifers, high resolution characterisation of spatially heterogeneous hydraulic and transport properties is of great importance. Predictions of first-arrival times and long term behaviour depend strongly on the quality of estimated hydraulic and transport parameters. By neglecting small-scale structures such as sand lenses and sediment intra-channel deposits, predictions are hardly accurate. This paper deals with the comparison of methods to characterize hydraulic parameters governing solute transport in unconsolidated porous aquifer materials. A large number of single-well slug tests, cross-well slug tests, a pumping test and a multi-level tracer test were conducted in a shallow alluvial gravel aquifer. This facilitated describing the spatial variation of hydraulic and transport parameters with high resolution. Multi-level slug tests results show distinct positive correlation with porosity-logs and drill cores and are thus an effective means to identify and characterize subsurface structures at high resolution. Values for hydraulic conductivity gained from pumping tests and cross-well slug tests revealed good accordance but were around one order of magnitude higher than the values derived from multi-level slug tests. This might be due to the fact that the three methods are involving different test-volumes. Hence, the determination of hydraulic conductivity underlies a scale dependency: larger test volumes tend to be characterized by larger K-values. Furthermore, our pumping test results show the importance of a high sampling rate, in our case 50 Hz, in order to determine reliably the hydraulic properties storage and anisotropy of hydraulic conductivity. Although pumping tests typically estimate hydraulic parameters on large-scale, small-scale heterogeneity could also be identified and characterized. This was again possible through the high resolution records of the early time drawdown. Finally, results of multi-level tracer testing supported observations from slug tests and porosity logs.

Reist, Fabian; Brauchler, Ralf; Jiménez, Santos; Bühler, Lukas; Hu, Linwei; Leuenberger-West, Fanny; Bayer, Peter

2014-05-01

299

Evaluation of reforestation in the Lower Mississippi River Alluvial Valley  

USGS Publications Warehouse

Only about 2.8 million ha of an estimated original 10 million ha of bottomland hardwood forests still exist in the Lower Mississippi River Alluvial Valley (LMAV) of the United States. The U.S. Fish and Wildlife Service, the U.S. Forest Service, and state agencies initiated reforestation efforts in the late 1980s to improve wildlife habitat. We surveyed restorationists responsible for reforestation in the LMAV to determine the magnitude of past and future efforts and to identify major limiting factors. Over the past 10 years, 77,698 ha have been reforested by the agencies represented in our survey and an additional 89,009 ha are targeted in the next 5 years. Oaks are the most commonly planted species and bare-root seedlings are the most commonly used planting stock. Problems with seedling availability may increase the diversity of plantings in the future. Reforestation in the LMAV is based upon principles of landscape ecology; however, local problems such as herbivory, drought, and flooding often limit success. Broad-scale hydrologic restoration is needed to fully restore the structural and functional attributes of these systems, but because of drastic and widespread hydrologic alterations and socioeconomic constraints, this goal is generally not realistic. Local hydrologic restoration and creation of specific habitat features needed by some wildlife and fish species warrant attention. More extensive analyses of plantings are needed to evaluate functional success. The Wetland Reserve Program is a positive development, but policies that provide additional financial incentives to landowners for reforestation efforts should be seriously considered.

King, S.L.; Keeland, B.D.

1999-01-01

300

Feast to famine: Sediment supply control on Laramide basin fill  

NASA Astrophysics Data System (ADS)

Erosion of Laramide-style uplifts in the western United States exerted an important first-order influence on Paleogene sedimentation by controlling sediment supply rates to adjacent closed basins. During the latest Cretaceous through Paleocene, these uplifts exposed thick intervals of mud-rich Upper Cretaceous foreland basin fill, which was quickly eroded and redeposited. Cretaceous sedimentary lithologies dominate Paleocene conglomerate clast compositions, and the volume of eroded foreland basin strata is approximately twice the volume of preserved Paleocene basin fill. As a result of this sediment oversupply, clastic alluvial and paludal facies dominate Paleocene strata, and are associated with relatively shallow and ephemeral freshwater lake facies. In contrast, large, long-lived, carbonate-producing lakes occupied several of the basins during the Eocene. Basement-derived clasts (granite, quartzite, and other metamorphic rocks) simultaneously became abundant in lower Eocene conglomerate. We propose that Eocene lakes developed primarily due to exposure of erosion-resistant lithologies within cores of Laramide uplifts. The resultant decrease in erosion rate starved adjacent basins of sediment, allowing the widespread and prolonged deposition of organic-rich lacustrine mudstone. These observations suggest that geomorphic evolution of the surrounding landscape should be considered as a potentially important influence on sedimentation in many other interior basins, in addition to more conventionally interpreted tectonic and climatic controls.

Carroll, Alan R.; Chetel, Lauren M.; Elliot Smith, M.

2006-03-01

301

Water-quality data for selected streams in the Mississippi Alluvial Plain ecoregion, northwestern Mississippi, September – October 2007  

USGS Publications Warehouse

From September through October 2007, the U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency, collected and analyzed water-quality samples from streams in the Yazoo River basin within the Mississippi Alluvial Plain ecoregion in northwestern Mississippi. Water-quality samples were collected at 56 sites in the study area and analyzed for various physical and chemical characteristics including, but not limited to, suspended sediment, nutrients, and chlorophyll a. Additionally, water temperature, pH, specific conductance, and dissolved oxygen data were measured at 28 of the sites using multiparameter water-quality meters at 30-minute intervals for a minimum of 48 hours. Data collected for this project will be used in the development of water-quality criteria for nutrients. The nutrient data will enhance existing datasets and support evaluation of cause and effect relations for nutrient criteria development. In addition, these indicators will assist in the development and evaluation of restoration and remediation plans for water bodies not meeting their designated uses, as stated in the U.S. Environmental Protection Agency's Clean Water Act Section 303(d).

Hicks, Matthew B.; Stocks, Shane J.

2010-01-01

302

UNESCO's G-WADI Program - Developing and Delivering Tools for Improved Water Management in Semi-arid and Arid Lands  

Microsoft Academic Search

UNESCO's Water and Development Information for Arid Lands - A Global Network (G-WADI) aims to strengthen the capacity to manage the water resources of arid and semi-arid areas around the globe through a network of international and regional cooperation. Six centers, including SAHRA headquartered at the University of Arizona and CHRS at UC-Irvine, are cooperating to improve water resource management

G. C. Woodard; B. Imam; S. Sorooshian

2007-01-01

303

Geologic evolution of Uinta-Piceance basin province, northwestern Colorado and northeastern Utah  

SciTech Connect

The Uinta-Piceance basin province (UPBP) has a complex Phanerozoic history characterized by five distinct phases of basin development (1) The UPBP formed part of a continental platform shelf on the northwestern flank of North America during the early and middle Paleozoic. Cambrian through Mississippian strata consist mainly of carbonate rocks, shale, and quartzite; contain major unconformities; and thicken westward. (2) Pennsylvanian-Permian uplifts of the ancestral Rocky Mountain orogeny segmented this continental platform shelf into the Eagle, Paradox, and Oquirrh basins. Basin-margin tectonics and cyclic eustatic-climatic fluctuations strongly controlled deposition of the clastic, carbonate, and evaporitic fill of these basins. (3) During the early Mesozoic, the UPBP formed part of a slowly subsiding continental platform. Triassic-Jurassic rocks include eolian, alluvial, and lacustrine deposits that thicken and grade westward into marine facies. (4) Paleozoic and early Mesozoic strata in the westernmost part of the UPBP were thrust eastward during the late Mesozoic Sevier orogeny, causing subsidence in the adjacent foreland basin. The history of the UPBP part of this foreland basin is recorded by thick nonmarine deposits within and adjacent to the thrust belt that grade eastward into thinner accumulations of marine rocks. (5) The geometry and style of regional compressional deformation changed markedly with onset of the latest Cretaceous-Paleogene Laramide orogeny. Laramide uplifts segmented the UPBP foreland basin into the Uinta and Piceance intermontane lacustrine basins. The geometry of these lacustrine basins is notably different from that of the late Paleozoic segment basins.

Johnson, S.Y.; Tuttle, M.L.; Bryant, B.H.; Dubiel, R.F.; Fouch, T.D.; Franczyk, K.J.; Grauch, V.J.S.; Grout, M.A.; Johnson, R.C.; Molenaar, C.M.; Nichols, D.J.; Nichols, K.M.; Nuccio, V.F.; Peterson, F.; Pitman, J.K.; Perry, W.J. Jr.; Potter, C.J.; Sawatzky, D.L.; Scott, R.W. Jr.; Verbeek, E.R.; Wanty, R.B. (Geological Survey, Denver, CO (USA))

1990-05-01

304

Diagenetic contrast of sandstones in hydrocarbon prospective Mesozoic rift basins (Ethiopia, UK, USA)  

NASA Astrophysics Data System (ADS)

Diagenetic studied in hydrocarbon-prospective Mesozoic rift basins were carried out in the Blue Nile Basin (Ethiopia), Ulster Basin (United Kingdom) and Hartford Basin (United States of America). Alluvial fan, single and amalgamated multistorey meandering and braided river, deep and shallow perennial lake, shallow ephemeral lake, aeolian and playa mud-flat are the prominent depositional environments. The studied sandstones exhibit red bed diagenesis. Source area geology, depositional environments, pore-water chemistry and circulation, tectonic setting and burial history controlled the diagenetic evolution. The diagenetic minerals include: facies-related minerals (calcrete and dolocrete), grain-coating clay minerals and/or hematite, quartz and feldspar overgrowths, carbonate cements, hematite, kaolinite, illite-smectite, smectite, illite, chlorite, actinolite, laumontite, pyrite and apatite. Diversity of diagenetic minerals and sequence of diagenetic alteration can be directly related to depositional environment and burial history of the basins. Variation in infiltrated clays, carbonate cements and clay minerals observed in the studied sandstones. The alluvial fan and fluviatile sandstones are dominated by kaolinite, illite calcite and ferroan calcite, whereas the playa and lacustrine sandstones are dominated by illite-smectite, smectite-chlorite, smectite, chlorite, dolomite ferroan dolomite and ankerite. Albite, pyrite and apatite are predominantly precipitated in lacustrine sandstones. Basaltic eruption in the basins modified mechanically infiltrated clays to authigenic clays. In all the studied sandstones, secondary porosity predominates over primary porosity. The oil emplacement inhabited clay authigenesis and generation of secondary porosity, whereas authigenesis of quartz, pyrite and apatite continued after oil emplacement.

Wolela, A.

2014-11-01

305

GEOMORPHIC AND HYDROGEOLOGICAL CONTROLS ON THE DISTRIBUTION OF WET MEADOWS IN THE CENTRAL GREAT BASIN  

EPA Science Inventory

The Great Basin is an arid landscape dominated by dryland vegetation such as big sage and xeric grasses. Meadow complexes occur in mountain drainages and consist of discrete parcels of land up to several hectares in area that are characterized by high water tables and that primar...

306

BIOGEOGRAPHIC IMPLICATIONS OF RECENT LOW-ELEVATION RECOLONIZATION BY NEOTOMA CINEREA IN THE GREAT BASIN  

Microsoft Academic Search

Homestead Cave, a paleontological site located in a low-elevation arid setting in the north- ern Bonneville Basin of northcentral Utah, documents the local extinction of Neotoma cinerea during the Middle Holocene. N. cinerea is present there today, and the Homestead Cave record suggests that recolonization likely occurred sometime prior to 1,000 years ago. This history supports the view (forwarded by

Donald K. Grayson; David B. Madsen

2000-01-01

307

Salt Accumulation in the Loessial Sequence in the Be'er Sheva Basin, Israel  

E-print Network

Salt Accumulation in the Loessial Sequence in the Be'er Sheva Basin, Israel MORDECKAIMAGARr / Evidence of climatic changes is recorded in the salt content of the surface sediments in arid zones, In wetter periods airborne salts are removed downward by leaching to the groundwater, whereas in drier

Gvirtzman, Haim

308

Connecting science to managers in river restoration in the Upper Klamath Basin, Oregon and California  

Microsoft Academic Search

The semi-arid Upper Klamath Basin is a complex landscape of agricultural land, pasture and forests, drained by rivers, lakes, and wetlands. Unique characteristics of the river systems include high natural nutrient loadings, large springs, low gradients, high sinuosity, fine sediment, herbaceous-dominated riparian vegetation, and habitat for salmonid and sucker fish. Following listing of several fish species under the Endangered Species

P. F. McDowell

2009-01-01

309

Petrographically deduced triassic climate for the Deep River Basin, eastern piedmont of North Carolina  

SciTech Connect

A petrographic comparison of Triassic, fluvial sandstones from the Deep River Basin in the eastern piedmont of North Carolina with nearby Holocene stream sands (1) indicates that he Triassic climate was more arid than today's and (2) distinguishes an eastern, more plutonic terrane from a western, more metamorphic source terrane. The paleoclimatic interpretation is based on differences in framework composition between modern and ancient sands of the same grain size, derived from the same rock type, transported similar distances and deposited in similar settings. The Triassic sandstones contain more lithic-fragments but less quartz than otherwise equivalent, modern sand in the Deep River Basin. Feldspar content is more complex, controlled by both source-rock composition and climate. Sand from the more plutonic terrane contains more feldspar and plutonic lithic-fragments than sand from the more metamorphic terrane, which contains more quartz and metamorphic lithic-fragments. This petrographic interpretation of the Triassic sandstones along with the presence of coal, limestone, chert and caliche in the middle of the section suggests that the Triassic climate was cyclic, changing from arid to humid and back to arid. Plate-tectonic reconstructions place the Deep River Basin between the Triassic equator and Tropic of cancer, where the easterly trade winds would predominate. Therefore, the arid portions of the cycle could have been due to a periodic, orographic, rain shadow formed as the result of intermittent movement along the Jonesboro Fault, creating a highland area east of the Deep River Basin.

McCarn, S.T.; Mansfield, C.F.

1985-01-01

310

Permanence of soil surface crusts on abandoned farmland in the Central Ebro Basin\\/Spain  

Microsoft Academic Search

Surface crusts are frequently found on fallow land in the semi-arid Ebro Basin (Spain) and are an important factor in land degradation. Soil surface sealing leads to a decrease in infiltration rates and a consequent increase in runoff, thereby accelerating sheet wash and rill erosion. Thin sections were used to analyse the development and structures of the different crusts found

Johannes B. Ries; Ulrike Hirt

2008-01-01

311

Sequence stratigraphy of the Late Permian Coal Measures in the Sydney Basin  

Microsoft Academic Search

In the Late Permian Newcastle, Tomago and Illawarra Coal Measures of the foreland Sydney Basin, eight 3rd?order depositional sequences form three sequence sets. The sequence sets constitute the highstand systems tract of a 2nd?order sequence. Up?sequence decreasing marine shale thickness and increasing incised?valley?fill thickness, coupled with an overall regressive trend from marine to dominantly alluvial environments, indicate that sedimentation was

C. Herbert

1995-01-01

312

Understanding runoff processes in a semi-arid environment through isotope and hydrochemical hydrograph separations  

NASA Astrophysics Data System (ADS)

The understanding of runoff generation mechanisms is crucial for the sustainable management of river basins such as the allocation of water resources or the prediction of floods and droughts. However, identifying the mechanisms of runoff generation has been a challenging task, even more so in arid and semi-arid areas where high rainfall and streamflow variability, high evaporation rates, and deep groundwater reservoirs increase the complexity of hydrological process dynamics. Isotope and hydrochemical tracers have proven to be useful in identifying runoff components and their characteristics. Moreover, although widely used in humid-temperate regions, isotope hydrograph separations have not been studied in detail in arid and semi-arid areas. Thus the purpose of this study is to determine if isotope hydrograph separations are suitable for the quantification and characterization of runoff components in a semi-arid catchment considering the hydrological complexities of these regions. Through a hydrochemical characterization of the surface water and groundwater sources of the catchment and two and three component hydrograph separations, runoff components of the Kaap Catchment in South Africa were quantified using both, isotope and hydrochemical tracers. No major disadvantages while using isotope tracers over hydrochemical tracers were found. Hydrograph separation results showed that runoff in the Kaap catchment is mainly generated by groundwater sources. Two-component hydrograph separations revealed groundwater contributions between 64 and 98% of total runoff. By means of three-component hydrograph separations, runoff components were further separated into direct runoff, shallow and deep groundwater components. Direct runoff, defined as the direct precipitation on the stream channel and overland flow, contributed up to 41% of total runoff during wet catchment conditions. Shallow groundwater defined as the soil water and near-surface water component, contributed up to 45% of total runoff, and deep groundwater contributed up to 84% of total runoff. A strong correlation for the four studied events was found between the antecedent precipitation conditions and direct runoff. These findings suggest that direct runoff is enhanced by wetter conditions in the catchment which trigger saturation excess overland flow as observed in the hydrograph separations.

Camacho, V. V.; Saraiva Okello, A. M. L.; Wenninger, J. W.; Uhlenbrook, S.

2015-01-01

313

Sedimentary record and climatic implications of recurrent deformation in the Tian Shan: Evidence from Mesozoic strata of the north Tarim, south Junggar, and Turpan basins, northwest China  

SciTech Connect

Detailed stratigraphic, sedimentologic, paleocurrent, and subsidence analyses were conducted on Mesozoic nonmarine sedimentary sections of the south Junggar, north Tarim, and Turpan basins, Xinjang Uygur Autonomous Region, northwest China. These three basins have been foreland basins throughout the Mesozoic and Cenozoic eras, as demonstrated by asymmetrically distributed basinwide sediment accumulations, foreland-style subsidence profiles, and a variety of outcrop and subsurface facies data. Mesozoic paleocurrent indicators measured in the south Junggar and north Tarim basins, as well as Mesozoic sandstone compositions from both basins, indicate that the intervening Tian Shan has existed as a positive physiographic feature partitioning the two basins throughout Mesozoic and Cenozoic time. Paleocurrent, facies, and subsurface isopach data suggest that the Turpan basin was established as a discrete feature by the Early Jurassic period. The timing and style of depositional systems within the north Tarim Mesozoic depocenter, the south Junggar Mesozoic depocenter, and the central Turpan basin are remarkably similar. Upper Triassic strata of each basin consist of alluvial conglomerate and associated braided-fluvial sandstone and siltstone which fine upward into lower through Middle Jurassic, locally organic-rich, meandering-fluvial, and lacustrine strata. Upper Jurassic braided-fluvial red beds in each basin are overlain by a distinct pulse of uppermost Jurassic alluvial conglomerate. Lower Cretaceous exposures consist of fine-grained red beds in north Tarim and Turpan and interbedded red and gray shale with local silty carbonates in south Junggar. Upper Cretaceous strata of the north Tarim and south Junggar basins are composed of alluvial conglomerate with associated braided-fluvial sandstone and siltstone. 94 refs., 17 figs.

Hendrix, M.S.; Graham, S.A.; Sobel, E.R. [Stanford Univ., CA (United States)] [and others] [Stanford Univ., CA (United States); and others

1992-01-01

314

Predicting the Future Impact of Droughts on Ungulate Populations in Arid and Semi-Arid Environments  

PubMed Central

Droughts can have a severe impact on the dynamics of animal populations, particularly in semi-arid and arid environments where herbivore populations are strongly limited by resource availability. Increased drought intensity under projected climate change scenarios can be expected to reduce the viability of such populations, yet this impact has seldom been quantified. In this study, we aim to fill this gap and assess how the predicted worsening of droughts over the 21st century is likely to impact the population dynamics of twelve ungulate species occurring in arid and semi-arid habitats. Our results provide support to the hypotheses that more sedentary, grazing and mixed feeding species will be put at high risk from future increases in drought intensity, suggesting that management intervention under these conditions should be targeted towards species possessing these traits. Predictive population models for all sedentary, grazing or mixed feeding species in our study show that their probability of extinction dramatically increases under future emissions scenarios, and that this extinction risk is greater for smaller populations than larger ones. Our study highlights the importance of quantifying the current and future impacts of increasing extreme natural events on populations and species in order to improve our ability to mitigate predicted biodiversity loss under climate change. PMID:23284700

Duncan, Clare; Chauvenet, Aliénor L. M.; McRae, Louise M.; Pettorelli, Nathalie

2012-01-01

315

Responses of terrestrial aridity to global warming  

NASA Astrophysics Data System (ADS)

dryness of terrestrial climate can be measured by the ratio of annual precipitation (P) to potential evapotranspiration (PET), where the latter represents the evaporative demand of the atmosphere, which depends on the surface air temperature, relative humidity, wind speed, and available energy. This study examines how the terrestrial mean aridity responds to global warming in terms of P/PET using the Coupled Model Intercomparison Project phase 5 transient CO2 increase to 2 × CO2 simulations. We show that the (percentage) increase (rate) in P averaged over land is ~1.7%/°C ocean mean surface air temperature increase, while the increase in PET is 5.3%/°C, leading to a decrease in P/PET (i.e., a drier terrestrial climate) by ~3.4%/°C. Noting a similar rate of percentage increase in P over land to that in evaporation (E) over ocean, we propose a framework for examining the change in P/PET, in which we compare the change in PET over land and E over ocean, both expressed using the Penman-Monteith formula. We show that a drier terrestrial climate is caused by (i) enhanced land warming relative to the ocean, (ii) a decrease in relative humidity over land but an increase over ocean, (iii) part of increase in net downward surface radiation going into the deep ocean, and (iv) different responses of PET over land and E over ocean for given changes in atmospheric conditions (largely associated with changes in temperatures). The relative contributions to the change in terrestrial mean aridity from these four factors are about 35%, 35%, 15%, and 15%, respectively. The slight slowdown of the surface wind over both land and ocean has little impact on the terrestrial mean aridity.

Fu, Qiang; Feng, Song

2014-07-01

316

Planform Dynamics of a Mixed Bedrock-Alluvial Meandering River  

NASA Astrophysics Data System (ADS)

The planform evolution of meandering rivers involves dynamic interactions among planform geometry, three-dimensional flow structure, bed morphology, sediment transport, and bank resistance. Modes of interaction among these factors in different types of bends have yet to be completely determined. This paper examines flow structure, bed morphology, and planform evolution in three different types of bends on the Wabash River, Illinois: an elongated loop with forested banks and extensive bedrock at the downstream end of the bend (Horseshoe Bend), an elongated loop with unforested banks and local bedrock control within the bend (Maier Bend), and a series of simple bends with forested banks and no bedrock control. Data consist of velocity measurements obtained between May 2011 and February 2013 for bankfull or near-bankfull flows using acoustic Doppler current profilers. Rates of migration and planform evolution were determined through GIS-based analysis of historical aerial photography from 1938 to present, including annual photos in recent years. Lidar data, sediment samples, and multi-beam echosounding data provide information on bed morphology, on the spatial extent of bedrock, and on bank materials. Horseshoe Bend has not moved substantially over the historical period of record. This lack of migration is in part related to extensive bedrock control, but also reflects high near-bank flow resistance produced by LWD and the relatively high resistance of bank materials to erosion. At Maier Bend, migration rates are high due to low resistance of bank materials to erosion, resulting in bend extension; however, the pattern of extension has been strongly influenced by the local outcropping of bedrock into the channel. In the simple bends, planform evolution has been dominated by translation, despite migration of the channel into forested sections of the floodplain. Bed morphology in these bends, especially the structure of point bars, strongly influences flow structure, resulting in high velocities near the outer bank well downstream of the bend apex. The results show that bedrock control can have an important influence on the planform evolution of mixed alluvial-bedrock rivers, yet also highlight the substantive effects of planform geometry, bed morphology, and bank resistance on bend development in these types of rivers.

Rhoads, B. L.; Konsoer, K. M.; Best, J.; Garcia, M. H.; Abad, J. D.

2013-12-01

317

Aridity and grazing as convergent selective forces: an experiment with an Arid Chaco bunchgrass.  

PubMed

It has been proposed that aridity and grazing are convergent selective forces: each one selects for traits conferring resistance to both. However, this conceptual model has not yet been experimentally validated. The aim of this work was to experimentally evaluate the effect of aridity and grazing, as selective forces, on drought and grazing resistance of populations of Trichloris crinita, a native perennial forage grass of the Argentinean Arid Chaco region. We collected seeds in sites with four different combinations of aridity and grazing history (semiarid/ subhumid x heavily grazed/lightly grazed), established them in pots in a common garden, and subjected the resulting plants to different combinations of drought and defoliation. Our results agreed with the convergence model. Aridity has selected T. crinita genotypes that respond better to drought and defoliation in terms of sexual reproduction and leaf growth, and that can evade grazing due to a lower shoot: root ratio and a higher resource allocation to reserves (starch) in stem bases. Similarly, grazing has selected genotypes that respond better to drought and defoliation in terms of sexual reproduction and that can evade grazing due to a lower digestibility of leaf blades. These results allow us to extend concepts of previous models in plant adaptation to herbivory to models on plant adaptation to drought. The only variable in which we obtained a result opposite to predictions was plant height, as plants from semiarid sites were taller (and with more erect tillers) than plants from subhumid sites; we hypothesize that this result might have been a consequence of the selection exerted by the high solar radiation and soil temperatures of semiarid sites. In addition, our work allows for the prediction of the effects of dry or wet growing seasons on the performance of T. crinita plants. Our results suggest that we can rely on dry environments for selecting grazing-resistant genotypes and on high grazing pressure history environments for selecting drought-resistant ones. PMID:21049876

Quiroga, R Emiliano; Golluscio, Rodolfo A; Blanco, Lisandro J; Fernández, Roberto J

2010-10-01

318

REGIONAL SNOWFALL PATTERNS IN THE HIGH, ARID ANDES  

Microsoft Academic Search

Since 1990 the project ’Climate Change in the Arid Andes‘ has been focusing on past climate and environmental conditions in the high mountain range of the north Chilean Andes (18° S–28° S). The extreme aridity of this region is shown by the absence of glaciers, even at the highest altitudes above 6700 m a.s.l. More knowledge of the present climatic

MATHIAS VUILLE; CASPAR AMMANN

1997-01-01

319

Herbivore-plant interactions and desertification in arid lands  

Technology Transfer Automated Retrieval System (TEKTRAN)

Arid lands around the world have experienced or are currently experiencing degradation that is known as desertification. Animal-plant interactions that have an effect on desertification are among the most important function of animals in arid ecosystems. Desertification has been defined as land de...

320

Uses of tree legumes in semi-arid regions  

SciTech Connect

Uses of tree legumes in semi-arid and arid regions are reviewed. This review is divided into sections according to the following general use categories: fuels; human food; livestock food; to increase yields of crops grown beneath their canopies;and control of desertification. (MHR)

Felker, P.

1980-01-01

321

ENVIRONMENTAL MONITORING AND ASSESSMENT PROGRAM - ARID ECOSYSTEMS 1992 PILOT REPORT  

EPA Science Inventory

The Environmental Monitoring and Assessment Program (EMAP) is being implemented to provide quantitative assessments of status and trends in the condition of ecological resources within the United States. n 1992 the EMAP Arid Ecosystems Resource Group (EMAP-Arid) conducted a pilot...

322

HOW IMPORTANT ARE SOIL FUNGI IN THE NITROGEN CYCLE OF ARID AND SEMIHOW IMPORTANT ARE SOIL FUNGI IN THE NITROGEN CYCLE OF ARID AND SEMIHOW IMPORTANT ARE SOIL FUNGI IN THE NITROGEN CYCLE OF ARID AND SEMIHOW IMPORTANT ARE SOIL FUNGI IN THE NITROGEN CYCLE OF  

E-print Network

HOW IMPORTANT ARE SOIL FUNGI IN THE NITROGEN CYCLE OF ARID AND SEMIHOW IMPORTANT ARE SOIL FUNGI IN THE NITROGEN CYCLE OF ARID AND SEMIHOW IMPORTANT ARE SOIL FUNGI IN THE NITROGEN CYCLE OF ARID AND SEMIHOW IMPORTANT ARE SOIL FUNGI IN THE NITROGEN CYCLE OF ARID AND SEMI----ARID ECOSYSTEMS?ARID ECOSYSTEMS

Hall, Sharon J.

323

Sequence stratigraphic interpretation methods for low-accommodation, alluvial depositional sequences: applications to reservoir characterization of Cut Bank field, Montana  

E-print Network

SEQUENCE STRATIGRAPHIC INTERPRETATION METHODS FOR LOW- ACCOMMODATION, ALLUVIAL DEPOSITIONAL SEQUENCES: APPLICATIONS TO RESERVOIR CHARACTERIZATION OF CUT BANK FIELD, MONTANA A Dissertation by RAHILA RAMAZANOVA Submitted...- ACCOMMODATION, ALLUVIAL DEPOSITIONAL SEQUENCES: APPLICATIONS TO RESERVOIR CHARACTERIZATION OF CUT BANK FIELD, MONTANA A Dissertation by RAHILA RAMAZANOVA Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment...

Ramazanova, Rahila

2009-05-15

324

Processes affecting the chemical composition of Blue Lake, an alluvial gold-mine pit lake in New Zealand  

Microsoft Academic Search

Blue Lake is an abandoned, water-filled alluvial gold-mine pit in Central Otago, New Zealand. Alluvial gold mining is generally considered to be chemically benign, unless mercury is added to assist gold separation. The major element, trace metal and isotopic composition of the pit lake was compared to nearby, unaffected streams. Blue Lake was found to be enriched in the major

Shaun L. L. BarkerA; Jonathan P. KimB; Dave Craw; Russell D. Frew; Keith A. Hunter

2004-01-01

325

Recharge areas and geochemical evolution of groundwater in an alluvial aquifer system in the Sultanate of Oman  

Microsoft Academic Search

A regional hydrogeochemical model was developed to evaluate the geochemical evolution of different groundwaters in an alluvial aquifer system in the Interior of Oman. In combination with environmental isotopes the model is able to extract qualitative and quantitative information about recharge, groundwater flow paths and hydraulic connections between different aquifers. The main source of water to the alluvial aquifer along

Juerg M. Matter; H. N. Waber; S. Loew; A. Matter

2006-01-01

326

Tectonic evolution of the Söke Basin: Extension-dominated transtensional basin formation in western part of the Büyük Menderes Graben, Western Anatolia, Turkey  

NASA Astrophysics Data System (ADS)

Integrated study on the stratigraphic and structural features of the Söke Basin on the western end of the Büyük Menderes Graben, Western Anatolia, has indicated that the tectonic evolution of Söke Basin includes extension-dominated transtension. At its western end, the EW-trending Büyük Menderes Graben tends to follow a zig-zag path influenced by zones of NE-SW-trending weakness in pre-rift crystalline rocks. The pre-existing fabric trends lie at angles up to 45-70° to the regional extension direction and are followed by extensional faults. The basin fill can be grouped into four major sequences separated by angular unconformities: (1) normal- to strike-slip-faulted Early-Middle Miocene alluvial fan-lacustrine sediments with economic coal beds, (2) folded and normal- to strike-slip-faulted Middle-Late Miocene lacustrine deposits intruded by volcanic rocks, (3) tilted Late Pliocene-Pleistocene alluvial fan-lacustrine carbonate deposits and shallow marine fan-delta deposits, and (4) undeformed Holocene alluvial, fluvial, and coastal sediments. The earliest sediments are interpreted, for the first time, to have been deposited in a supradetachment basin governed by the activity of an extensional detachment that separated metamorphic rocks in the footwall from ophiolitic nappes in the hangingwall. During the Middle-Late Miocene, high-angle faults cross-cut the low-angle detachment, and alluvial fans from lacustrine sediments were deposited under the control of an E-W-trending dip-slip normal fault and NE-SW-trending oblique-slip normal faults that formed an extensional basin. This activity was followed by normal to strike-slip-dominated deformation, leading to a highly complex mosaic of faults and fault-blocks, and fragmentation of the oldest basin-fill rock units. Finally, from Pleistocene until modern times, extensional forces have been in operation and have led to the reactivation of the Priene-Sazli fault, in front of which the Quaternary Söke-Milet Basin developed under the control of oblique extension. These results support an extension-dominated transtension that has existed since the Early Miocene in the western end of the Büyük Menderes Graben.

Sümer, Ökmen; ?nci, U?ur; Sözbilir, Hasan

2013-04-01

327

ARID1B-mediated disorders: Mutations and possible mechanisms.  

PubMed

Mutations in the gene encoding AT-rich interactive domain-containing protein 1B (ARID1B) were recently associated with multiple syndromes characterized by developmental delay and intellectual disability, in addition to nonsyndromic intellectual disability. While the majority of ARID1B mutations identified to date are predicted to result in haploinsufficiency, the underlying pathogenic mechanisms have yet to be fully understood. ARID1B is a DNA-binding subunit of the Brahma-associated factor chromatin remodelling complexes, which play a key role in the regulation of gene activity. The function of remodelling complexes can be regulated by their subunit composition, and there is some evidence that ARID1B is a component of the neuron-specific chromatin remodelling complex. This complex is involved in the regulation of stem/progenitor cells exiting the cell cycle and differentiating into postmitotic neurons. Recent research has indicated that alterations in the cell cycle contribute to the underlying pathogenesis of syndromes associated with ARID1B haploinsufficiency in fibroblasts derived from affected individuals. This review describes studies linking ARID1B to neurodevelopmental disorders and it summarizes the function of ARID1B to provide insights into the pathogenic mechanisms underlying ARID1B-mediated disorders. In conclusion, ARID1B is likely to play a key role in neurodevelopment and reduced levels of wild-type protein compromise normal brain development. Additional studies are required to determine the mechanisms by which impaired neural development contributes to the intellectual disability and speech impairment that are consistently observed in individuals with ARID1B haploinsufficiency. PMID:25674384

Sim, Joe C H; White, Susan M; Lockhart, Paul J

2015-02-01

328

ARID1B-mediated disorders: Mutations and possible mechanisms  

PubMed Central

Summary Mutations in the gene encoding AT-rich interactive domain-containing protein 1B (ARID1B) were recently associated with multiple syndromes characterized by developmental delay and intellectual disability, in addition to nonsyndromic intellectual disability. While the majority of ARID1B mutations identified to date are predicted to result in haploinsufficiency, the underlying pathogenic mechanisms have yet to be fully understood. ARID1B is a DNA-binding subunit of the Brahma-associated factor chromatin remodelling complexes, which play a key role in the regulation of gene activity. The function of remodelling complexes can be regulated by their subunit composition, and there is some evidence that ARID1B is a component of the neuron-specific chromatin remodelling complex. This complex is involved in the regulation of stem/progenitor cells exiting the cell cycle and differentiating into postmitotic neurons. Recent research has indicated that alterations in the cell cycle contribute to the underlying pathogenesis of syndromes associated with ARID1B haploinsufficiency in fibroblasts derived from affected individuals. This review describes studies linking ARID1B to neurodevelopmental disorders and it summarizes the function of ARID1B to provide insights into the pathogenic mechanisms underlying ARID1B-mediated disorders. In conclusion, ARID1B is likely to play a key role in neurodevelopment and reduced levels of wild-type protein compromise normal brain development. Additional studies are required to determine the mechanisms by which impaired neural development contributes to the intellectual disability and speech impairment that are consistently observed in individuals with ARID1B haploinsufficiency. PMID:25674384

Sim, Joe C. H.; White, Susan M; Lockhart, Paul J.

2015-01-01

329

Agronomic and Economic Impacts of Reuse Secondary Treated Wastewater in Irrigation under Arid and Semi-Arid Regions  

Microsoft Academic Search

Sustainable agricultural development, in arid and semi-arid region is influenced to a great extent by sources of water that might be used economically and effectively in developing agriculture programs. Therefore, the use of treated municipal wastewater, as a new source for water irrigation, has been encouraged by Saudi government to increase the efficient use of water irrigation in crop production.

Ali Abdullah Alderfasi

330

Holocene landscape evolution and geoarcheology of low-order streams in the Rio Grande basin, San Juan Mountains, Colorado, USA  

NASA Astrophysics Data System (ADS)

This geoarcheological study investigates soil stratigraphy and geochronology of alluvial deposits to determine Holocene landscape evolution within the Hot Creek, La Jara Creek, and Alamosa River drainage basins in the San Juan Mountains of Colorado. Geomorphic mapping and radiocarbon dating indicate synchronicity in patterns of erosion, deposition, and stability between drainage basins. In all three basins, the maximum age of mapped alluvial terraces and fans is ~ 3300 cal yr BP. A depositional period seen at both Hot Creek and the Alamosa River begins ~ 3300 to 3200 cal yr BP. Based on soil development, short periods of stability followed by alluvial fan aggradation occur in the Alamosa River basin ~ 2200 cal yr BP. A period of landscape stability at Hot Creek before ~ 1100 cal yr BP is followed by a period of rapid aggradation within all three drainages between ~ 1100 and 850 cal yr BP. A final aggradation event occurred between ~ 630 and 520 cal yr BP at La Jara Creek. These patterns of landscape evolution over the past ~ 3300 yr provide the framework for an archeological model that predicts the potential for buried and surficial cultural materials in the research area.

Carver, Daniel P.; Beeton, Jared M.

2014-09-01

331

A refined characterization of the alluvial geology of yucca flat and its effect on bulk hydraulic conductivity  

USGS Publications Warehouse

In Yucca Flat, on the Nevada National Security Site in southern Nevada, the migration of radionuclides from tests located in the alluvial deposits into the Paleozoic carbonate aquifer involves passage through a thick, heterogeneous section of late Tertiary and Quaternary alluvial sediments. An understanding of the lateral and vertical changes in the material properties of the alluvial sediments will aid in the further development of the hydrogeologic framework and the delineation of hydrostratigraphic units and hydraulic properties required for simulating groundwater flow in the Yucca Flat area. Previously published geologic models for the alluvial sediments within Yucca Flat are based on extensive examination and categorization of drill-hole data, combined with a simple, data-driven interpolation scheme. The U.S. Geological Survey, in collaboration with Stanford University, is researching improvements to the modeling of the alluvial section, incorporating prior knowledge of geologic structure into the interpolation method and estimating the uncertainty of the modeled hydrogeologic units.

Phelps, G.A.; Halford, K.J.

2011-01-01

332

Evaluation of Flow Dynamics in a Karst Aquifer System at Sapanca Lake Basin (turkey) via Hydrochemical and Isotopic Data  

NASA Astrophysics Data System (ADS)

Sapanca Lake, located 20 km west of Izmit bay, is a fresh water lake with tectonic origin and supplies drinking and municipal water to the region. Groundwater discharges from a karstic aquifer developed in Permo-Triassic and Late Jurassic-Early Cretaceous aged marbles and an alluvial aquifer distributed in east-west direction on the Sapanca plain play an important role in the recharge of the lake. In the Sapanca lake basin, there are numerous springs discharging (1 to 75 lt/s) from different elevations of the karstic aquifer system. Dolines, sinkholes, depression fields, and disappearing rivers developed on the southern heights of the basin are directly connected with the karstic aquifer and allow the aquifer system to show rapid recharge and discharge characteristics. In the scope of the study, 25 karst spring waters as well as 25 wells drilled in the alluvial aquifer were sampled as representatives of dry and rainy periods. Hydrochemical and isotopic (18O/2D/3H) compositions of the samples were evaluated along with the hydrogeology and the fracture analysis of the basin in order to assess the hydraulic relationship between the aquifer systems and the groundwater circulation in the basin. Results show that groundwaters from alluvial and karstic aquifers are modern water and demonstrate similar hydrochemical facies (Ca-HCO3 ve Ca+Mg-HCO3). Although showing seasonal differences, isotopic composition (18O/2D) of the karst springs resembles those of the streams and groundwaters from alluvial aquifer. This suggests that ground and surface waters feed each other periodically and characterize a mixing. Fracture analysis of the basin suggests that faulting has significant control over groundwater discharge and circulation in the karst aquifer and form discontinuities in the system, subdividing it into several aquifer sub-systems.

Gunduz, O. C.; Yolcubal, I.

2013-12-01

333

Influence of groundwater on the degradation of irrigated soils in a semi-arid region, the inner delta of the Niger River, Mali  

NASA Astrophysics Data System (ADS)

The problem of soil degradation through alkalinization/salinization in an irrigated area with a semi-arid climate was examined in the inner delta of the Niger River, Mali, by the study of groundwater hydraulics and hydrochemistry in an area recharged by irrigation water. On the basis of data analysis on various scales, it is concluded that the current extent of the surface saline soils is due to a combination of three factors: (1) the existence of ancient saline soils (solonchaks) resulting from the creation of a broad sabkha west of the former course of the Niger River, now called the Fala of Molodo. These saline crusts were gradually deposited during the eastward tilting of the tectonic block that supports the Niger River; (2) the irrigation processes during the recent reflooding of the Fala of Molodo (river diversion in 1950). These used very poorly mineralized surface water but reintroduced into the alluvial groundwater system - generally of a low permeability (K=10-6 m s-1) - salts derived from the ancient solonchaks; and (3) the redeposition of the dissolved salts on the surface due to the intense evapotranspiration linked to the present Sahelian climate. In this context, only efficient artificial draining of subsurface alluvial groundwater can eliminate most of the highly mineralized flow and thus reduce the current saline deposits.

Valenza, A.; Grillot, J. C.; Dazy, J.

2000-08-01

334

Effects of Land Use and Hydrogeology on the Water Quality of Alluvial Aquifers in Eastern Iowa and Southern Minnesota, 1997  

USGS Publications Warehouse

Ground-water samples were collected from monitoring wells at 31 agricultural and 30 urban sites in the Eastern Iowa Basins study unit during June-August 1997 to evaluate the effects of land use and hydrogeology on the water quality of alluvial aquifers. Ground-water samples were analyzed for common ions, nutrients, dissolved organic carbon, tritium, radon-222, pesticides and pesticide metabolites, volatile organic compounds, and environmental isotopes. Calcium, magnesium, and bicarbonate were the dominant ions in most samples and were likely derived from solution of carbonate minerals (calcite and dolomite) present in alluvial detrital deposits. Chloride and nitrate were dominant anions in samples from several wells. Sodium and chloride concentrations were significantly higher in samples from urban areas, where roads are more numerous and road salts may be more frequently applied, than in agricultural areas. Nitrate was detected in 94 percent of samples from agricultural areas and 77 percent of samples from urban areas. Nitrate concentrations were significantly higher in agricultural areas than in urban areas and exceeded the U.S. Environmental Protection Agency maximum contaminant level for drinking water (10 milligrams per liter as N) in 39 percent of samples from agricultural areas. Nitrate concentrations in samples from urban areas did not exceed the maximum contaminant level. Greater use of fertilizers in agricultural areas most likely contributes to higher nitrate concentrations in samples from those areas. Tritium-based ages indicate ground water was most likely recharged after the 1950's at all but one sampling site. Agricultural and urban land-use areas have remained relatively stable in the study area since the 1950's; therefore, the effects of current land use should be reflected in ground water sampled during this study. Radon-222 was detected in all samples and exceeded the U.S. Environmental Protection Agency's previously proposed maximum contaminant level for drinking water (300 picocuries per liter) in 71 percent of samples. Pesticides were detected in 84 percent of samples from agricultural areas and 70 percent from urban areas. Atrazine and metolachlor were the most frequently detected pesticides in samples from agricultural areas; atrazine and prometon were the most frequently detected pesticides in samples from urban areas. None of the pesticide concentrations exceeded U.S. Environmental Protection Agency maximum contaminant levels or lifetime health advisories for drinking water. Pesticide metabolites were detected in 94 percent of samples from agricultural areas and 53 percent from urban areas. Metolachlor ethane sulfonic acid and deethylatrazine were the most frequently detected metabolites in samples from agricultural areas; metolachlor ethane sulfonic acid and alachlor ethane sulfonic acid were the most frequently detected metabolites in samples from urban areas. Total metabolite concentrations were significantly higher in samples from agricultural areas than in samples from urban areas. Total pesticide concentrations (parent compounds) tended to be higher in samples from agricultural areas; however, this difference was not statistically significant. Metabolites constituted the major portion of the total residue concentration in the alluvial aquifer. Volatile organic compounds were detected in 40 percent of samples from urban areas and 10 percent from agricultural areas. Methyl tertbutyl ether was the most commonly detected volatile organic compound and was present in 23 percent of samples from urban areas. Elevated concentrations (greater than 30 micrograms per liter) of methyl tert-butyl ether and BTEX compounds (benzene, toluene, ethylbenzene, and xylene) in two samples from urban areas suggest the possible presence of point-source gasoline leaks or spills. Factors other than land use may contribute to observed differences in water quality between and within agricultural and urban

Savoca, Mark E.; Sadorf, Eric M.; Linhart, S. Mike; Akers, Kim K.B.

2000-01-01

335

Modelling basin effects on earthquake ground motion in the Santiago de Chile basin by a spectral element code  

NASA Astrophysics Data System (ADS)

Simulations of strong ground motion within the Santiago de Chile Metropolitan area were carried out by means of 3-D deterministic wave propagation tool based on the spectral element method. The simulated events take into account the pronounced interface between the low-velocity sedimentary basin and the bedrock as well as topography of the area. To verify our model we simulated a regional earthquake recorded by a dense network installed in the city of Santiago for recording aftershock activity after the 2010 February 27 Maule main shock. The results proof the alluvial basin amplification effects and show a strong dependence of spectral amplification in the basin on the local site conditions. Moreover, we studied the seismic response due to a hypothetical Mw= 6.0 event occurring along the active San Ramón Fault, which is crossing the eastern edge of the city. The scenario earthquakes exhibit that an unfavourable interaction between fault rupture, radiation mechanism and complex geological and topographic conditions in the near-field region may give rise to large values of peak ground velocity in the basin. Finally, 3-D numerical predictions of ground motion are compared with the one computed according to ground motion prediction equations selected among the next generation attenuation relationships, in terms of ground motion peak values and spectral acceleration. The comparison underlines that the 3-D scenario simulations predict a significantly higher level of ground motion in the Santiago basin, especially over deep alluvial deposits. Moreover, also the location of the rupture nucleation largely influences the observed shaking pattern.

Pilz, Marco; Parolai, Stefano; Stupazzini, Marco; Paolucci, Roberto; Zschau, Jochen

2011-11-01

336

Quantities and associations of lead, zinc, cadmium, manganese, chromium, nickel, vanadium, and copper in fresh Mississippi delta alluvium and New Orleans alluvial soils  

Microsoft Academic Search

The topic of this study is the effect of anthropogenic metals on the geochemical quality of urban soils. This is accomplished by comparing the metal contents and associations between two alluvial soils of the lower Mississippi River Delta, freshly deposited alluvial parent materials and alluvial soils collected from a nearby urban environment. Fresh alluvium samples (n=97) were collected from the

H. W. Mielke; C. R. Gonzales; M. K. Smith; P. W. Mielke

2000-01-01

337

Sundaland basins  

NASA Astrophysics Data System (ADS)

The continental core of Sundaland, comprising Sumatra, Java, Borneo, the Thai-Malay Peninsula and Indochina, was assembled during the Triassic Indosinian orogeny, and formed an exposed landmass during Pleistocene lowstands. Because the region includes extensive shallow seas, and is not significantly elevated, it is often assumed to have been stable for a long period. This stability is a myth. The region is today surrounded by subduction and collision zones, and merges with the India-Asia collision zone. Cenozoic deformation of Sundaland is recorded in the numerous deep sedimentary basins alongside elevated highlands. Some sediment may have been supplied from Asia following Indian collision but most was locally derived. Modern and Late Cenozoic sediment yields are exceptionally high despite a relatively small land area. India-Asia collision, Australia-SE Asia collision, backarc extension, subduction rollback, strike-slip faulting, mantle plume activity, and differential crust-lithosphere stretching have been proposed as possible basin-forming mechanisms. In scale, crustal character, heat flow and mantle character the region resembles the Basin and Range province or the East African Rift, but is quite unlike them in tectonic setting. Conventional basin modeling fails to predict heat flow, elevation, basin depths and subsidence history of Sundaland and overestimates stretching factors. These can be explained by interaction of a hot upper mantle, a weak lower crust, and lower crustal flow in response to changing forces at the plate edges. Deformation produced by this dynamic model explains the maintenance of relief and hence sediment supply over long time periods.

Hall, Robert; Morley, Christopher K.

338

PRESERVATION OF ARCHAEOLOGICAL MATERIALS IN ARID ENVIRONMENTS RELEVANT TO YUCCA MOUNTAIN  

SciTech Connect

The objective of this study was to evaluate archaeological materials from underground openings or shallow burial in arid environments relevant to Yucca Mountain and to draw conclusions about how their state and their environment of preservation could be of relevance to design and operational aspects of the high-level waste repository. The study has evaluated materials from cultures in the arid regions of the ancient Middle East and compared them with the preservation of ancient materials in dry cave sites in the Great Basin desert area of Nevada. The emphasis has been on materials found in undisturbed underground openings such as caves and un-backfilled tombs. Long-term preservation of such materials in underground openings and the stability of the openings themselves provide useful analogue information that serves as a reference point for considering the operation and evolution of the Yucca Mountain repository. Being able to shed light, by close physical and environmental analogy, on what happens in underground openings over many thousands of years provides valuable underpinning to illustrations of expected system performance and offers pointers towards optimizing repository system and operational design.

N. Chapman, A. Dansie, C. McCombie

2006-02-24

339

NATURAL ARSENIC CONTAMINATION OF HOLOCENE ALLUVIAL AQUIFERS BY LINKED TECTONIC, WEATHERING, AND MICROBIAL PROCESSES  

EPA Science Inventory

Linked tectonic, geochemical, and biologic processes lead to natural arsenic contamination of groundwater in Holocene alluvial aquifers, which are the main threat to human health around the world. These groundwaters are commonly found a long distance from their ultimate source of...

340

The structure of two alluvial soils in Italy after 10 years of conventional and minimum tillage  

Microsoft Academic Search

Micro and macroporosity, pore shape and size distribution, aggregate stability, saturated hydraulic conductivity and crop yield were analysed in alluvial silty loam (Fluventic Eutrochrept) and clay soils (Vertic Eutrochrept) following long-term minimum and conventional tillage. The soil structure attributes were evaluated by characterizing porosity by means of image analysis of soil thin sections prepared from undisturbed soil samples.The interaggregate microporosity,

M. Pagliai; M. Raglione; T. Panini; M. Maletta; M. La Marca

1995-01-01

341

DAM IMPACTS ON AND RESTORATION OF AN ALLUVIAL RIVER - RIO GRANDE, NEW MEXICO  

Microsoft Academic Search

The impact of construction of dams and reservoirs on alluvial rivers extends both upstream and downstream of the dam. Downstream of dams, both the water and sediment supplies can be altered leading to adjustments in the river channel geometry and ensuing changes in riparian and aquatic habitats. The wealth of pre and post-regulation data on the Middle Rio Grande, New

Gigi RICHARD; Pierre JULIEN

2004-01-01

342

An evaluation strategy for conservation goals of the Mississippi Alluvial Valley  

USGS Publications Warehouse

The population goals and habitat objectives established by the Mississippi Alluvial Valley Migratory Bird Initiative are based on several unverified assumptions. We have developed an evaluation strategy that identifies research needed to verify these assumptions. We also have outlined a monitoring strategy designed to track progress toward achieving habitat objectives and population goals.

Twedt, D.J.; Hamel, P.B.; Cooper, R.J.; Woodrey, M.S.

2000-01-01

343

Temporal evolution of groundwater composition in an alluvial aquifer (Pisuerga River, Spain) by principal component analysis  

Microsoft Academic Search

A set of quantitative analytical data from the alluvial aquifer of the Pisuerga river, located at the north-east of Valladolid (Spain), has been processed by multivariate statistical techniques in order to investigate the evolution of the groundwater composition between two surveys. The original matrix consisted of 16 physico-chemical variables, determined in 32 groundwater samples collected in 32 sampling sites of

Beatriz Helena; Rafael Pardo; Marisol Vega; Enrique Barrado; Jose Manuel Fernandez; Luis Fernandez

2000-01-01

344

NATURAL HAZARDS ON ALLUVIAL FANS: THE VENEZUELA DEBRIS FLOW AND FLASH FLOOD DISASTER  

E-print Network

NATURAL HAZARDS ON ALLUVIAL FANS: THE VENEZUELA DEBRIS FLOW AND FLASH FLOOD DISASTER In December Venezuela. Rainfall on December 2-3 totaled 200 millimeters (8 inches) and was followed by a major storm, Denver, Colorado, Naples, Italy, and Vargas, Venezuela. In time scales spanning thousands of years

Eaton, L. Scott

345

HYDRAULIC ANALYSIS OF BASE-FLOW AND BANK STORAGE IN ALLUVIAL STREAMS  

EPA Science Inventory

This paper presents analytical solutions, which describe the effect of time-variable net recharge (net accretion to water table) and bank storage in alluvial aquifers on the sustenance of stream flows during storm and inter-storm events. The solutions relate the stream discharge,...

346

The hydrogeology of the Condamine River Alluvial Aquifer, Australia: a critical assessment  

NASA Astrophysics Data System (ADS)

The Condamine plain is an important agricultural zone in Australia with prominent irrigated cotton and grain crops. About one third of the irrigation water is pumped from the shallow alluvial aquifer, causing gross aquifer depletion over time. Over the last few decades, various hydrological, hydrochemical, and geological aspects of this aquifer and the overlying floodplain (including soil properties) have been investigated and used to construct the conceptual understanding and numerical models for management of this resource. Yet, the water balance of the aquifer is still far from resolved, and the geological contact between the alluvial sediments and underlying bedrock is yet to be categorically defined, to mention two major uncertainties. This report collates up-to-date knowledge of different disciplines, critically evaluates the accepted hydrogeological conventions, highlights key knowledge gaps, and suggests strategies for future research. Among recommendations are (1) development of numerical flow and solute transport models for the natural (i.e. pre-developed) period, (2) analysis of groundwater for isotopic composition and presence of pesticides, CFCs and PPCPs, and (3) use of stochastic approaches to characterize the hydraulic properties of the alluvial sediments. These and other proposed measures are relevant also to other alluvial aquifers which suffer from similar fundamental uncertainties.

Dafny, Elad; Silburn, D. Mark

2014-05-01

347

Spatial variability of some soil chemical properties in alluvial plains of northwestern India  

Microsoft Academic Search

A survey of the soils of alluvial plains of northwestern India was carried out and measurements of soil chemical properties were made over 470 sites on a grid of 10 km x 10 km. The data were analyzed geostatistically to determine the degree and nature of spatial dependence. Variation appeared to be isotropic. The available N, P, and K showed

M. S. Grewal; I. S. Dahiya; Anil Kumar

1997-01-01

348

Evaluation of spatial variation in some soil properties of alluvial plains  

Microsoft Academic Search

This study was carried out to examine the spatial dependence in silt + clay content, cation exchange capacity, and pH of soils on the alluvial plains of Haryana. Four hundred and seventy samples were drawn at 10 × 10 km grid nodes from 24 great group associations of three moisture regime zones. The coefficient of variation ranged from 7.10% to

Anil Kumar; M. S. Kuhad; M. S. Grewal; I. S. Dahiya

1996-01-01

349

Modeling the effects of deep chiseling with DRAINMOD for alluvial soils  

Technology Transfer Automated Retrieval System (TEKTRAN)

DRAINMOD is a drainage model that has been widely used in the shallow water table regions of the US including southeastern US. Therefore, it is important that DRAINMOD realistically simulate surface runoff, infiltration and drainage volume for the surface-seal-formation prone alluvial soils that are...

350

Boulder, Pavement, Pit; Sample Selection for Cosmogenic Nuclide Dating on Alluvial Fans  

Microsoft Academic Search

Selecting sample targets and methods that minimize the effects of erosion, inheritance, and material movement is one of the largest issues facing cosmogenic isotope dating. Since sample material availability often sharply limits methods, establishing error estimates in less-than-ideal sampling situations is also important. Our study of alluvial fan offsets in the Eastern California Shear Zone (Mojave Desert) takes advantage of

L. A. Perg; M. E. Oskin; D. Blumentritt; M. Strane; S. Mukhopadhyay

2005-01-01

351

Fourier grain shape analysis: a means for correlating alluvial deposits at the Nevada Test Site  

Microsoft Academic Search

Quartz sand derived from alluvial fans that drain different lithologies at the Nevada Test Site can be distinguished on the basis of grain shape as described by the Fourier series in closed form. Specifically, we examined tuff units from the Piapi Canyon and Indian Trail Formations as well as carbonate-bearing clastic units from the Eleana Formation. Discrimiation between rock types

B. T. Grothaus; G. L. Hage

1978-01-01

352

Determine the optimum spectral reflectance of juniper and pistachio in arid and semi-arid region  

NASA Astrophysics Data System (ADS)

Arid and semi-arid areas of northeast Iran cover about 3.4 million ha are populated by two main tree species, the broadleaf Pistacia vera. L (pistachio) and the conifer Juniperus excelsa ssp. polycarpos (Persian juniper). Natural stands of pistachio in Iran are not only environmentally important but genetically essential as seed sources for pistachio production in orchards. In this study, we estimated the optimum spectral reflectance of juniper forests and natural pistachio stands using remote sensing to help in the sustainable management and production of pistachio in Iran. In this research spectral reflectance are able to specify of multispectral from Advanced Land Observing Satellite (ALOS) that provided by JAXA. These data included PRISM is a panchromatic radiometer with a 2.5 m spatial resolution at nadir, has one band with a wavelength of 0.52-0.77 ?m and AVNIR-2 is a visible and near infrared radiometer for observing land and coastal zones with a 10 m spatial resolution at nadir, has four multispectral bands: blue (0.42-0.50 ?m), green (0.52-0.60 ?m), red (0.61-0.69 ?m), and near infrared (0.76-0.89 ?m). Total ratio vegetation index (TRVI) of optimum spectral reflectance of juniper and pistachio have been evaluated. The result of TRVI for Pistachio and juniper were (R2= 0.71 and 0.55). I hope this research can provide decision of managers to helping sustainable management for arid and semi-arid regions in Iran.

Fadaei, Hadi; Suzuki, Rikie

2012-11-01

353

Phylogeography of the Arid Shrub Atraphaxis frutescens (Polygonaceae) in Northwestern China: Evidence From cpDNA Sequences.  

PubMed

Climatic fluctuations during the Pleistocene are usually considered as a significant factor in shaping intraspecific genetic variation and influencing demographic histories. To well-understand these processes in desert northwest China, we selected arid adapted Atraphaxis frutescens as the study species. Two cpDNA regions (psbK-psbI, psbB-psbH) were sequenced in 272 individuals from 33 natural populations across the range of this shrub, and 10 haplotypes were identified. It was found to contain high levels of total gene diversity (H T = 0.858), and low levels of within-population diversity (H S = 0.092). Analysis of molecular variance (AMOVA) indicates that genetic differentiation primarily occurs among groups of populations. Based on BEAST (Bayesian Evolutionary Analysis Sampling Trees) analysis, we suggest that intraspecific differentiation of the species, resulting from isolated populations, accompanied enhanced desertification during the middle and late Pleistocene. The expansion of the Gurbantunggut and Kumtag deserts in this area appears to have triggered divergence among populations of the western, central, and eastern portions of the region and shaped genetic differentiation among them. Two possible independent glacial refugia were predicted, the Ili Valley and the northern Junggar Basin. Extensive development of arid habitats (desert margin and arid piedmont grassland) coupled with a more equable climate because the early Holocene are factors likely to have generated recent expansion of A. frutescens. PMID:25516612

Xu, Zhe; Zhang, Ming-Li

2015-01-01

354

A geochemical approach for the evaluation of water availability and salinity in closed basins: the Draa Basin, Morocco  

NASA Astrophysics Data System (ADS)

In the sub-Saharan Draa Basin of southern Morocco, winter snowmelt from the Atlas Mountains is captured in a reservoir, stored, and discharged downstream for irrigation in six oases. The combined imported surface water and shallow groundwater exploitation for sustaining local agriculture is a common practice in many worldwide arid basins.. Like in many basins, the salinization of groundwater in the Draa Basin has become a limiting factor for agricultural development and long-term sustainability. .Since most of the IPCC climate models predict a significant decrease in precipitation in Northern Africa over the next few decades, water shortage and salinization induced from climate change are expected to exacerbate the existing water crisis. Evaluating the sources and mechanisms of this salinization can provide the necessary tools for sustainable water management in the Draa Basin that may be applied to many similarly arid basins. Here we present new geochemical results from 98 shallow groundwater and four surface water samples collected in May 2009 and April 2010. The samples were collected from upstream tributaries to the reservoir, the reservoir, and groundwater from in six oases downstream of the reservoir. The goal of the survey was to identify the sources of salinity using geochemical and isotopic (87Sr/86Sr, ?2H, and ?18O) signatures in the groundwater, which could derive from three possible sources (1) evaporation and recycling of the irrigation water; (2) dissolution of salts that were entrapped in the unsaturated zone; and (3) lateral flow of adjacent groundwater. The data show a large salinity range from fresh water to highly brackish water with total dissolved salts (TDS) exceeding 12,000 mg/L. The salinity increases with downstream flow between successive oases. Br/Cl and B/Cl ratios decrease with TDS, which suggests that the main mechanism of salinization in the Draa Basin is derived salt dissolution in the unsaturated zone and salinization of the underlying shallow groundwater. The 87Sr/86Sr ratio in groundwater slightly increases with distance from the reservoir, indicating some contribution of lateral groundwater with a higher 87Sr/86Sr ratio. Initial oxygen and hydrogen isotopes measurements show that some of the downstream groundwater has lower ?2H and ?18O values relative to the reservoir, while other have respectively higher values. These variations could reflect both contribution of external 18O- and 2H-depleted groundwater sources and further evaporation of the irrigation water that resulted in 18O and 2H enrichments. Overall, the isotopic data provide some unique insights for the hydrological balance and salinization mechanisms of groundwater in the Draa basin, which could be applied to other basins in arid regimes.

Warner, N.; Lgourna, Z.; Boutaleb, S.; Tagma, T.; Vinson, D. S.; Ettayfi, N.; Bouchaou, L.; Vengosh, A.

2010-12-01

355

Flow regime change in an Endorheic basin in Southern Ethiopia  

NASA Astrophysics Data System (ADS)

Endorheic basins, often found in semi-arid and arid climates, are particularly sensitive to changes in climatological fluxes such as precipitation, evaporation and runoff, resulting in variability of river flows as well as of water levels in end-point lakes that are often present. In this paper we apply the Indicators of Hydrological Alteration (IHA) to characterise change to the natural flow regime of the Omo-Ghibe basin in Southern Ethiopia. This endorheic basin is considered relatively pristine, with the basin being the main source of flow to Lake Turkana, the end-point lake in the East-African rift valley. The water level in Lake Turkana shows significant fluctuation, but an increasing trend can be observed over the past 20 yr. The reasons are currently not well understood. Of the five groups of metrics in the IHA, only those related to magnitude were found to show significant trends, with the main trend being the increase of flow during the dry season. This trend was not reflected in climatological drivers such as rainfall, evaporation, and temperature (which shows an increasing trend), but rather is attributed to the substantial changes in Land Use and Land Cover (LULC) in the basin. The impact on the basin hydrology is apparent mainly in the more humid part of the basin. The significant shift from forest and woodland to grassland and cropland results in a decrease of actual evaporation and subsequent increase in (dry season) runoff. The long term trend of the increasing levels in lake Turkana are related to these trends in dry season flows, while shorter term fluctuations of the lake levels are attributed primarily to anomalies in consecutive wet and dry season rainfall.

Worku, F. F.; Werner, M.; Wright, N.; van der Zaag, P.; Demissie, S.

2014-01-01

356

Infiltration of atrazine and metabolites from a stream to an alluvial aquifer  

USGS Publications Warehouse

The infiltration of atrazine, deethylatrazine, and deisopropylatrozine from Walnut Creek, a tributary stream, to the alluvial valley aquifer along the South Skunk River in central Iowa occurred where the stream transects the river's flood plain. A preliminary estimate indicated that the infiltration was significant and warrants further investigation. Infiltration was estimated by measuring the loss of stream discharge in Walnut Creek and the concentrations of atrazine and its metabolites deethylatrazine and deisopropylatrazine, in ground water 1 m beneath the streambed. Infiltration was estimated before application of agrichemicals to the fields during a dry period on April 7, 1994, and after application of agrichemicals during a period of small runoff on June 8, 1994. On April 7, the flux of atrazine, deethylatrazine, and deisopropylatrazine from Walnut Creek into the alluvial valley aquifer ranged from less than 10 to 60 (??g/d)/m2, whereas on June 8 an increased flux ranged from 270 to 3060 (??g/d)/m2. By way of comparison, the calculated fluxes of atrazine beneath Walnut Creek, for these two dates, were two to five orders of magnitude greater than an estimated flux of atrazine to ground water caused by leaching from a field on a per-unit-area basis. Furthermore, the unit-area flux rates of water from Walnut Creek to the alluvial valley aquifer were about three orders of magnitude greater than estimated recharge to the alluvial aquifer from precipitation. The large flux of chemicals from Walnut Creek to the alluvial valley aquifer was due in part to the conductive streambed and rather fast ground water velocities; average vertical hydraulic conductivity through the streambed was calculated as 35 and 90 m/d for the two sampling dates, and estimated ground water velocities ranged from 1 to 5 m/d.

Squillace, P.J.; Burkart, M.R.; Simpkins, W.W.

1997-01-01

357

Regolith Thickness Instability and the Formation of Tors in Arid, Granitic Environments  

NASA Astrophysics Data System (ADS)

We previously developed a model that incorporates a feedback between bedrock weathering and physical erosion (stream flow and diffusive processes) to explain the origin and maintenance of the laterally extensive (km's), nearly uniformly thin regolith blanket that characterizes pediments in arid regions such as the southwestern United States. Specifically, physical erosion controls pediment form by modifying regolith thickness, which, in turn, regulates bedrock weathering rates (Anderson, 2002). This relationship yields coupled bedrock and alluvial surfaces that lower together through time. Hydrogeochemical considerations and field observations in arid, granitic environments suggest that the relationship between weathering rates and regolith thickness exhibits a maximum for a finite thickness of cover. Our model offers an explanation for the isolated bedrock knobs (tors/inselbergs) that often punctuate otherwise smooth pediments. These features may arise as a consequence of stochasticity in rainfall and sediment transport conditions driven by fluctuations in climate, combined with the "peaked" nature of our weathering relationship. Climate fluctuations, which may manifest themselves as periods of higher effective moisture (decadal to millennial time scales) or changes in local base levels, may invoke a transition in which mantled surfaces lower at rates exceeding the bare-bedrock weathering rate. (Typically, boundary conditions and geometrical constraints restrict mantled surfaces to lower at rates below the bare-bedrock weathering rate in our model.) With a mantled surface lowering at such a rate, the form of the weathering-rate curve predicts that the pediment will be susceptible to an instability that will lead to bare-bedrock; regolith thickness that falls below a threshold value will approach a stable attractor at zero thickness. If this instability is triggered in a spatially heterogeneous pattern, perhaps as runoff from an intense rainfall event interacts with heterogeneities in regolith thickness and surface topography, a tor field will tend to develop. Incipient tors may then grow due to accelerated denudation on mantled surfaces compared to bare rock surfaces. As the tors grow in height, they will also tend to develop the steep sides and angular junctions with the surrounding pediment that characterize classic tor fields such as those found on the flanks of Cima Dome or in Joshua Tree National Park in the Mojave Desert of Southern California. Subsequent shifts in climate or local base level that cause the sediment surface to lower at a rate less than the bare-bedrock weathering rate will lead to a progressive decrease in tor height, ultimately leading to their disappearance. Tors in these environments thus represent possibly transient features related to fluctuations in climate or local transport conditions.

Strudley, M. W.; Murray, A. B.; Haff, P. K.

2004-12-01

358

Tectonic setting of Cretaceous basins on the NE Tibetan Plateau: Insights from the Jungong basin  

USGS Publications Warehouse

Quantifying the Cenozoic growth of high topography in the Indo-Asian collision zone remains challenging, due in part to significant shortening that occurred within Eurasia before collision. A growing body of evidence suggests that regions far removed from the suture zone experienced deformation before and during the early phases of Himalayan orogenesis. In the present-day north-eastern Tibetan Plateau, widespread deposits of Cretaceous sediment attest to significant basin formation; however, the tectonic setting of these basins remains enigmatic. We present a study of a regionally extensive network of sedimentary basins that are spatially associated with a system of SE-vergent thrust faults and are now exposed in the high ranges of the north-eastern corner of the Tibetan Plateau. We focus on a particularly well-exposed basin, located ~20km north of the Kunlun fault in the Anyemaqen Shan. The basin is filled by ~900m of alluvial sediments that become finer-grained away from the basin-bounding fault. Additionally, beds in the proximal footwall of the basin-bounding fault exhibit progressive, up-section shallowing and several intraformational unconformities which can be traced into correlative conformities in the distal part of the basin. The observations show sediment accumulated in the basin during fault motion. Regional constraints on the timing of sediment deposition are provided by both fossil assemblages from the Early Cretaceous, and by K-Ar dating of volcanic rocks that floor and cross-cut sedimentary fill. We argue that during the Cretaceous, the interior NE Tibetan Plateau experienced NW-SE contractional deformation similar to that documented throughout the Qinling-Dabie orogen to the east. The Songpan-Ganzi terrane apparently marked the southern limit of this deformation, such that it may have been a relatively rigid block in the Tibetan lithosphere, separating regions experiencing deformation north of the convergent Tethyan margin from regions deforming inboard of the east Asian margin. ?? 2011 The Authors. Basin Research ?? 2011 Blackwell Publishing Ltd, European Association of Geoscientists & Engineers and International Association of Sedimentologists.

Craddock, W.H.; Kirby, E.; Dewen, Z.; Jianhui, L.

2012-01-01

359

Strontium Isotope Ratios (87Sr/86Sr) as Tracers for Recharge Areas, Groundwater Movement and Mixing in an Arid Coastal Region of the Sultanate of Oman  

NASA Astrophysics Data System (ADS)

In arid and semi-arid regions, conventional hydrological investigations often fail to adequately describe groundwater systems due to a large spatial and temporal variability of hydrological parameters. Alternatively, this study from northern Oman utilizes strontium isotope ratios (87Sr/86Sr) to describe the origin and evolution of groundwater in the Batinah coastal alluvial aquifer, which supplies water for the most densely populated, cultivated and industrialized area in the Sultanate. Sr-isotope ratios in groundwater samples from over 100 wells distributed over the 10,000 km2 study area show that the Jabal Akhdar mountains are the most significant recharge area for the adjacent coastal alluvial plain. Sr-isotope ratios in samples taken along the foothills of the mountains are as high as 0.7120, indicating that this water has interacted with the pre-Permian silt- and sandstone formations exposed in the anticline of the Jabal Akhdar. Sr-isotope ratios of these pre-Permian sediments exceed 0.7200 and are thus significantly higher than isotope ratios of the Permian to Mesozoic limestones and dolomites (87Sr/86Sr = 0.7067 to 0.7080) that form the limbs of the anticline. Groundwater that infiltrates in the mountains follows two major groundwater flowpaths across the alluvial plain towards the coast. Along these two preferential pathways, the Sr-isotope signal changes from 0.7110-0.7120 at the foothills to 0.7095-0.7100 a few kilometers further onto the coastal plain, indicating the addition of a second, locally infiltrated, groundwater component. Mixing calculations based on Sr- and Cl-concentrations together with Sr-isotopes indicate that recharge on the coastal plain only accounts for approximately 10% of the total groundwater recharge, the remaining 90% originating in the Jabal Akhdar mountains. Surprisingly, very little influence of oceanic basement rocks, the Samail ophiolite, is detectable in the Sr-isotope ratios of groundwater samples. Even in catchments composed entirely of ophiolite, the groundwater Sr-isotope ratios are consistently above 0.7080, indicating little rock-water interaction with the ophiolite matrix (87Sr/86Sr = 0.7030 to 0.7065). Instead, groundwater samples closely resemble the Sr-isotope signature of magnesite and calcite lined fractures in the ophiolitic host rocks (87Sr/86Sr = 0.7078 to 0.7087), suggesting that groundwater flow occurs predominantly through hydraulically connected fracture systems, which is consistent with modern-day tritium activities detected in all bedrock wells.

Weyhenmeyer, C. E.; Waber, H. N.; Kramers, J.; Burns, S. J.; Matter, A.

2001-12-01

360

Mapping Quaternary alluvial fans in the southwestern United States based on multiparameter surface roughness of lidar topographic data  

NASA Astrophysics Data System (ADS)

alluvial fans have diverse surface morphologies related to both depositional and weathering processes. Numerous studies have demonstrated that the surface expression and morphometry of alluvial fans can be used as an indicator of their relative age of deposition, but only recently has there been an effort to utilize high-resolution topographic data to differentiate alluvial fans by surface age with automated and quantifiable routines. We developed a quantitative model for mapping the relative age of alluvial fan surfaces based on multiparameter surface roughness values computed from 1 m resolution lidar topographic data. Roughness is defined as a function of observational scale and integration of slope, curvature, and aspect topographic parameters. Alluvial fan roughness values were computed across multiple observation scales (3 × 3 m to 150 × 150 m) based on the standard deviation (SD) of slope, curvature (tangential), and aspect topographic parameters. Plots of roughness value versus size of observation scale suggest that the SD of each parameter over a 7 × 7 m observation window best identified the signature of surface roughness elements. Roughness maps derived from slope, curvature, and aspect at this scale were integrated using fuzzy logic. The integrated roughness map was then classified into five relative morphostratigraphic surface age categories (active wash to ~400 ka) and statistically compared with a similar fivefold surface age map of alluvial fans developed using traditional field surveys and aerial photographic interpretation. The model correctly predicted the distribution and relative surface age of ~61% of alluvial fan landforms based on traditional mapping techniques.

Regmi, Netra R.; McDonald, Eric V.; Bacon, Steven N.

2014-01-01