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In this study we identify the physiographic and snowpack conditions currently represented by snowpack telemetry (SNOTEL) stations in the Rio Grande headwaters. Based on 8 years of advanced very high-resolution radiometer data (1995–2002) a snow cover persistence index was derived. Snow cover persistence values at the seven SNOTEL sites ranged from 3·9 to 4·75, with an average 14% greater than the mean persistence of the watershed. Using elevation, western barrier distance, and vegetation density, a 32-node binary classification tree model explained 75% of the variability in average snow cover persistence. Terrain classes encompassing the Lily Pond, Middle Creek, and Slumgullion SNOTEL sites represented 4·1%,...
Snow covered area (SCA) observations from the Landsat Enhanced Thematic Mapper (ETM+) were used in combination with a distributed snowmelt model to estimate snow water equivalent (SWE) in the headwaters of the Rio Grande basin (3,419 km2) - a spatial scale that is an order of magnitude greater than previous reconstruction model applications. In this reconstruction approach, modeled snowmelt over each pixel is integrated over the time of ETM+ observed snow cover to estimate SWE. Considerable differences in the magnitude of SWE were simulated during the study. Basin-wide mean SWE was 2�6 times greater in April 2001 versus 2002. Despite these climatological differences, the model adequately recovered SWE at intensive...
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Complete daily water budget information was assembled for a 105 km segment of the South Platte River in the plains region below Denver, CO, for the period 1983?1993. The data were used in testing the possibility that dependence of alluvial exchange mechanisms on stage height, as shown by models of alluvial exchange, allows alluvial exchange to be predicted continuously over a given reach through use of statistical information on river discharge. The study segment was divided into an upper and a lower reach; daily alluvial exchanges for each reach were estimated by the method of residuals. The two reaches show small (15%) but statistically significant annual differences in rates of exchange. For each reach, there...
Cyanobacteria are known to form a crust on soil surfaces holding soil particles together and thereby offering resistance to erosion. A controlled experiment was carried out to throw light on this issue. The experiment consisted of subjecting erosion cups filled with soil to artificial rainfall in the laboratory. Three sets of erosion cups, each set consisting of six, were used. One set consisted of soil with inoculated cyanobacteria and the second set consisted of soil with naturally colonized cyanobacteria, both over a period of about 8 months. The third set consisted of soil with no bacterial growth. The results indicate that the soil erosion cups with the inoculated cyanobacterial crust had at least one order...
Drainages are important features of semiarid landscapes because they are areas where surface water, groundwater, and terrestrial and aquatic ecosystems converge. Management of these critical ecohydrological systems requires a sound understanding of surface water?groundwater interactions. At the basin- to landscape-scale, drainage density, location, and channel characteristics are formed upon a geomorphic and geologic template that limit where and how surface water?groundwater interactions occur. At smaller scales, semiarid surface water?groundwater interactions exhibit a high degree of temporal and spatial variability that links directly to biogeochemical characteristics and ecosystem dynamics. In this paper, we...
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Two distributed parameter models, a one-dimensional (1D) model and a two-dimensional (2D) model, are developed to simulate overland flow in two small semiarid shrubland watersheds in the Jornada basin, southern New Mexico. The models are event-based and represent each watershed by an array of 1-m2 cells, in which the cell size is approximately equal to the average area of the shrubs. Each model uses only six parameters, for which values are obtained from field surveys and rainfall simulation experiments. In the 1D model, flow volumes through a fixed network are computed by a simple finite-difference solution to the 1D kinematic wave equation. In the 2D model, flow directions and volumes are computed by a second-order...
Streamflow in the upper Colorado River in the western USA is always snowmelt dominated, whereas the lower river's perennial streamflows are snowmelt dominated only 50% of the time. The magnitude and timing of peak flows is important for water resources management. In the upper basin the annual maximum daily discharge usually occurs in May or June, and in the lower basin this peak is observed to occur in any month except May or June. The timing of one-half of the specific runoff is used as a second measure of the variability in timing and magnitude of streamflows. For the upper basin, nine watersheds are used to illustrate streamflow trends, with the Yampa River used as a sample sub-basin. For the lower basin, five...
Drainages are important features of semiarid landscapes because they are areas where surface water, groundwater, and terrestrial and aquatic ecosystems converge. Management of these critical ecohydrological systems requires a sound understanding of surface water?groundwater interactions. At the basin- to landscape-scale, drainage density, location, and channel characteristics are formed upon a geomorphic and geologic template that limit where and how surface water?groundwater interactions occur. At smaller scales, semiarid surface water?groundwater interactions exhibit a high degree of temporal and spatial variability that links directly to biogeochemical characteristics and ecosystem dynamics. In this paper, we...
Regional transport of water and dissolved constituents through heavily regulated river systems is influenced by the presence of reservoirs. Analysis of seasonal patterns in solute fluxes for salinity and nutrients indicates that in-reservoir processes within large storage reservoirs in the Rio Grande and Colorado basins (southwestern USA) are superimposed over the underlying watershed processes that predominate in relatively unregulated stream reaches. Connectivity of the aquatic system with the landscape is apparently disrupted by processes within the reservoir systems; these processes result in large changes in characteristics for solute transport that persist downstream in the absence of significant inputs. Additionally,...
Global synthesis of the findings from �140 recharge study areas in semiarid and arid regions provides important information on recharge rates, controls, and processes, which are critical for sustainable water development. Water resource evaluation, dryland salinity assessment (Australia), and radioactive waste disposal (US) are among the primary goals of many of these recharge studies. The chloride mass balance (CMB) technique is widely used to estimate recharge. Average recharge rates estimated over large areas (40?374 000 km2) range from 0�2 to 35 mm year1, representing 0�1?5% of long-term average annual precipitation. Extreme local variability in recharge, with rates up to �720 m year1, results from focussed...
Estimating the annual mass flux at a network of fixed stations is one approach to characterizing water quality of large rivers. The interpretive context provided by annual flux includes identifying source and sink areas for constituents and estimating the loadings to receiving waters, such as reservoirs or the ocean. Since 1995, the US Geological Survey's National Stream Quality Accounting Network (NASQAN) has employed this approach at a network of 39 stations in four of the largest river basins of the USA: the Mississippi, the Columbia, the Colorado and the Rio Grande. In this paper, the design of NASQAN is described and its effectiveness at characterizing the water quality of these rivers is evaluated using data...
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Drainages are important features of semiarid landscapes because they are areas where surface water, groundwater, and terrestrial and aquatic ecosystems converge. Management of these critical ecohydrological systems requires a sound understanding of surface water-groundwater interactions. At the basin- to landscape-scale, drainage density, location, and channel characteristics are formed upon a geomorphic and geologic template that limit where and how surface water-groundwater interactions occur. At smaller scales, semiarid surface water-groundwater interactions exhibit a high degree of temporal and spatial variability that links directly to biogeochemical characteristics and ecosystem dynamics. In this paper, we...
Tributaries may either ameliorate or exacerbate the geomorphic and ecologic impacts of flow regulation by altering the flux of water and sediment into the flow-regulated mainstem. To capture the effects of tributary influences on a flow regulated river, long-term discharge and cross-sectional data are used to assess the geomorphic and hydrologic impacts of impoundment. In addition, the use of the short-lived cosmogenic radioisotope 7Be (half-life 53·4 days) to link sediment transport dynamics to benthic macroinvertebrate community structure is evaluated. It is found that the 7Be activity of transitional bed load sediment is highly seasonal and reflects both variations in activity of sediment sources and limited...
In semiarid complex terrain, the landscape creates spatial niches for different types of vegetation through the effects of aspect, slope and curvature on the water and energy balance at the soil surface. The ecohydrology of rangelands is defined by the interaction of soils, plants and climate occurring on a topographic surface. While these interactions have been studied for subtle terrain, little is known about the controls exerted by terrain position, in particular terrain aspect, on ecosystem processes. Furthermore, differential plant establishment can lead to measurable differences in rates of soil development, which in turn can affect soil hydraulic properties and the surface water balance. In this study, we...
The detectability of the interannual variations of terrestrial water storage in 70 river basins acquired by satellite gravimetry was investigated using the Japan Meteorological Agency?Simple Biosphere (JMA?SiB) model. Terrestrial water storages for the monthly, seasonal, and annual averaging periods were computed from the output of a 10 year integration performed by the JMA-SiB model. The satellite specification was assumed to be the same as for the NASA Gravity Recovery and Climate Experiment (GRACE). The total errors in the satellite-gravimetry-derived terrestrial water storage (including the instrument error, atmospheric error, and error due to the postglacial rebound) were computed for each period at each basin....
Willow communities dominate mid-elevation riparian areas throughout the Rocky Mountains of North America. However, many willow stands are rapidly declining in aerial cover and individual plants in stature. A poor understanding of the processes that control willow establishment hinders identifying the causes of this decline. We analysed the processes that have facilitated or limited willow establishment over the last half of the 20th century on two large floodplains in Rocky Mountain National Park in Colorado by addressing two questions: (1) How does hydrologic regime control willow establishment on different fluvial landforms? (2) How might climate-driven variations in hydrologic regime affect future willow establishment?...
Pre- and post-remediation data sets are used herein to assess the effectiveness of remedial measures implemented in the headwaters of the Mineral Creek watershed, where contamination from hard rock mining has led to elevated metal concentrations and acidic pH. Collection of pre- and post-remediation data sets generally followed the synoptic mass balance approach, in which numerous stream and inflow locations are sampled for the constituents of interest and estimates of streamflow are determined by tracer dilution. The comparison of pre- and post-remediation data sets is confounded by hydrologic effects and the effects of temporal variation. Hydrologic effects arise due to the relatively wet conditions that preceded...
Biological soil crusts (BSCs) are the dominant living cover in many drylands of the world. They possess many features that can influence different aspects of local hydrologic cycles, including soil porosity, absorptivity, roughness, aggregate stability, texture, pore formation, and water retention. The influence of biological soil crusts on these factors depends on their internal and external structure, which varies with climate, soil, and disturbance history. This paper presents the different types of biological soil crusts, discusses how crust type likely influences various aspects of the hydrologic cycle, and reviews what is known and not known about the influence of biological crusts on sediment production and...
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Suspended sediment, sediment-associated, total trace element, phosphorus (P), and total organic carbon (TOC) fluxes were determined for the Mississippi, Columbia, Rio Grande, and Colorado Basins for the study period (the 1996, 1997, and 1998 water years) as part of the US Geological Survey's redesigned National Stream Quality Accounting Network (NASQAN) programme. The majority (≥70%) of Cu, Zn, Cr, Ni, Ba, P, As, Fe, Mn, and Al are transported in association with suspended sediment; Sr transport seems dominated by the dissolved phase, whereas the transport of Li and TOC seems to be divided equally between both phases. Average dissolved trace element levels are markedly lower than reported during the original NASQAN...
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Remote sensing is an important source of snow-cover extent for input into the Snowmelt Runoff Model (SRM) and other snowmelt models. Since February 2000, daily global snow-cover maps have been produced from data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS). The usefulness of this snow-cover product for streamflow prediction is assessed by comparing SRM simulated streamflow using the MODIS snow-cover product with streamflow simulated using snow maps from the National Operational Hydrologic Remote Sensing Center (NOHRSC). Simulations were conducted for two tributary watersheds of the Upper Rio Grande basin during the 2001 snowmelt season using representative SRM parameter values. Snow depletion...
map background search result map search result map One- and two-dimensional modelling of overland flow in semiarid shrubland, Jornada basin, New Mexico Annual suspended sediment and trace element fluxes in the Mississippi, Columbia, Colorado, and Rio Grande drainage basins Analysis of groundwater exchange for a large plains river in Colorado (USA) Surface water-groundwater interactions in semiarid drainages of the American southwest A comparison of MODIS and NOHRSC snow-cover products for simulating streamflow using the Snowmelt Runoff Model Analysis of groundwater exchange for a large plains river in Colorado (USA) One- and two-dimensional modelling of overland flow in semiarid shrubland, Jornada basin, New Mexico Surface water-groundwater interactions in semiarid drainages of the American southwest A comparison of MODIS and NOHRSC snow-cover products for simulating streamflow using the Snowmelt Runoff Model Annual suspended sediment and trace element fluxes in the Mississippi, Columbia, Colorado, and Rio Grande drainage basins