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Runoff generated directly on Mancos Shale hillslopes initially picks up solutes by surface flushing. The major mechanism of subsequent solute pickup involves transport of soluble minerals as particulate matter with sediment. Solute release increases contemporaneously with increase in sediment concentration during rilling and rill entrenchment. Moreover, solute release increases as the power per unit width of surface area increases, thereby causally explaining the high correlation between runoff salinity and slope inclination. The regression between these two variables may be used as a tool to assess salinity hazard. Published in Journal of Hydrology, volume 59, issue 1-2, on pages 189 - 207, in 1982.
This research investigates the interannual variability of soil moisture as related to large-scale climate variability and also evaluates the spatial and temporal variability of modeled deep layer (40?140 cm) soil moisture in the Upper Colorado River Basin (UCRB). A three layers hydrological model VIC-3L (Variable Infiltration Capacity Model ? 3 layers) was used to generate soil moisture in the UCRB over a 50-year period. By using wavelet analysis, deep layer soil moisture was compared to the Palmer Drought Severity Index (PDSI), precipitation, and streamflow to determine whether deep soil moisture is an indicator of climate extremes. Wavelet and coherency analysis for the UCRB indicated a strong relationship between...
This study analyzed the linkages between large-scale climate patterns and regional precipitation variability, in particular the interannual variation of seasonal precipitation in the Colorado River Basin. Two climate indices, the Southern Oscillation Index (SOI) and the Pacific Decadal Oscillation (PDO), were selected to represent climate patterns. Conceptual influence indices, which quantify the strength of linkages between climate patterns and precipitation variability, were developed based on the Standardized Precipitation Index (SPI). In turn, the spatial variability of the influence indices within the Colorado River Basin was examined for different combinations of SOI and PDO phases and lead times from zero...
Recently the National Weather Service has developed a geostatistical model to generate areal estimates of snow water equivalent (the water content of snowpack) in various river basins throughout the Western USA. The areal snow water equivalent estimates are used to update the hydrologic simulation models used to produce extended streamflow forecasts in the USA. Currently, when the snow water equivalent estimates are obtained, it is assumed that the ground-based and airborne data used in the spatial model are measured without error. In this research, we illustrate how to modify the spatial prediction model to account for measurement errors in the observed airborne and ground-based snow data, derive the expressions...
In this study, winter mean 700 mbar height anomalies over the eastern North Pacific Ocean and the western USA are related to variability in snowpack accumulations measured on or about 1 April at 21 snowcourse stations within and near the Gunnison River basin in Colorado. Results indicate that lower than normal snowpack accumulations are primarily associated with positive 700 mbar height anomalies (anomalous anticyclonic circulation) over the western USA. Moist air from the Pacific Ocean is moved to the north of the western USA along the western margin of the anomalous anticyclonic circulation. In contrast, higher than normal snowpack accumulations are associated with negative 700 mbar height anomalies (anomalous...
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The study presented here utilized long-term streamflow records (over 500 years) to investigate the influence of interannual/interdecadal climate variability on the Colorado River basin. 19 unimpaired water year streamflow stations were reconstructed utilizing partial least square regression using standard tree ring chronologies. The spatial and temporal variability of drought was evaluated for all the stations for the different centuries in the record. Finally, the relationship between individual impact of ENSO, PDO, and AMO and its combined effect on streamflow was determined using the non parametric Rank Sum test for different lag years (0, +1, +2, and +3) of streamflow. This research also determined the change...
The fundamental rationale for statistical downscaling is that the raw outputs of climate change experiments from General Circulation Models (GCMs) are an inadequate basis for assessing the effects of climate change on land-surface processes at regional scales. This is because the spatial resolution of GCMs is too coarse to resolve important sub-grid scale processes (most notably those pertaining to the hydrological cycle) and because GCM output is often unreliable at individual and sub-grid box scales. By establishing empirical relationships between grid-box scale circulation indices (such as atmospheric vorticity and divergence) and sub-grid scale surface predictands (such as precipitation), statistical downscaling...
Availability of long-term information on the variability of water resources in a given area is particularly important for sustainable resource management. Developing watershed simulation models that can be run using annually-resolved proxy climate data provides a way to improve reconstructions of hydrological parameters over multi-century time scales. Through the addition of a snowmelt modeling component, we enhanced a simple water-balance model to simulate streamflow at seasonal resolution. The model was calibrated to the upper Meadow Valley Wash, Nevada, USA, using USGS gage number 09417500 streamflow records. PRISM data at 2.5 arc-min resolution were used to reconstruct streamflow at the seasonal timescale (October...
The spatial and temporal distribution of point precipitation quantiles representing abnormal moisture conditions over the Colorado River Basin (CRB) is analyzed by means of the Standardized Precipitation Index (SPI), calculated in annual and seasonal aggregations. From a cell-by-cell analysis, the area covered by abnormally wet and dry conditions during the last century shows an inverse relationship with their frequency of occurrence, with frequent events (occurring 80% of the time) in which abnormal conditions cover less than 10% of the basin and infrequent events (occurring 5% of the time) in which abnormal conditions cover around 50% of the basin. During El Ni�o years, both extremely wet and dry conditions are...
In the Central Rocky Mountains, snowfall dominates precipitation. Airborne contaminants retained in the snowpack can affect high elevation surface water chemistry during snowmelt. At the Fraser Experimental Forest (FEF), located west of the Continental Divide in Central Colorado, snowmelt dominates the annual hydrograph, and accounts for >95% of annual stream water discharge. During the winters of 1989?1993, we measured precipitation inputs, snowpack water equivalent (SWE) and ion content, and stream water chemistry every 7?10 days along a 3150?3500 m elevation gradient in the subalpine and alpine Lexen Creek watershed. The study objectives were to (1) quantify the distribution of SWE and snowpack chemical content...
Growing and changing demands on water supply, along with natural climate variability and possible anthropogenically induced climate change, make water resource management and planning increasingly challenging, particularly in arid regions. Instrumental climate and gaged streamflow records provide just a snapshop of recent natural hydrologic variability. In this paper, we use tree-ring-based annual streamflow reconstructions for the Sacramento River in California and the Blue River in western Colorado to analyze the temporal and spatial variability of widespread drought simultaneously affecting both basins over the past five centuries. Stability of joint-drought episodes and the covariation of reconstructed flows...
Mountain snowpack is the main source of water in the semi-arid Colorado River Basin (CRB), and while the demands for water are increasing, competing and often conflicting, the supply is limited and has become increasingly variable over the 20th Century. Greater variability is believed to contribute to lower accuracy in water supply forecasts, plus greater variability violates the assumption of stationarity, a fundamental assumption of many methods used in water resources engineering planning, design and management. Thus, it is essential to understand the underpinnings of hydroclimatic variability in order to accurately predict effects of climate changes and effectively meet future water supply challenges. A new...
This study focuses on regionalization and reconstruction of April 1 snow water equivalent (SWE) of snow courses stations located in the Upper Colorado River basin (UCRB) and evaluates regional drought scenarios for the last 480 years. Rotated principal component analysis (PCA) and cluster analysis were used to regionalize the snow course stations in the UCRB. Both methods of regionalization identified four regions of snow course stations, which were spatially distributed in the regions (east, west, north and south). Then, partial least squares regression (PLSR) was used to reconstruct three regional SWE time series in the UCRB based on residual tree-ring chronologies. Tree-ring chronologies that were positively...
Changes in regional temperature and precipitation expected to occur as a result of the accumulation of greenhouse gases may have significant impacts on water resources. We use a conceptual hydrologic model, developed and operated by the National Weather Service, to study the sensitivity of surface runoff in several sub-basins of the Colorado River to these changes. Increases in temperature of 2�C decrease mean annual runoff by 4?12%. A temperature increase of 4�C decreases mean annual runoff by 9?21%. Increases or decreases in annual precipitation of 10?20% result in corresponding changes in mean annual runoff of approximately 10?20%. For the range of scenarios studied, these results suggest that runoff in the basin...
Streamflow prediction in ungauged basins provides essential information for water resources planning and management and ecohydrological studies yet remains a fundamental challenge to the hydrological sciences. A methodology is presented for stratifying streamflow regimes of gauged locations, classifying the regimes of ungauged streams, and developing models for predicting a suite of ecologically pertinent streamflow metrics for these streams. Eighty-four streamflow metrics characterizing various flow regime attributes were computed along with physical and climatic drainage basin characteristics for 150 streams with little or no streamflow modification in Colorado, Washington, and Oregon. The diverse hydroclimatology...
The effective discharge is defined as the increment of discharge that transports the largest fraction of the annual sediment load over a period of years. Increments of the average annual total sediment load transported by various discharges were calculated by the flow-duration, sediment-transport-curve method for 15 gaging stations in the Yampa River basin of Colorado and Wyoming. A total sediment-transport curve was constructed for each gaging station by adding measured instantaneous suspended-sediment discharges to bedload-sediment discharges computed by the Meyer-Peter and Mueller relation. The streamflow durations were compiled from the respective gaging-station records. The quantity of sediment transported...
Land and water resource development can independently eliminate riparian plant communities, including Fremont cottonwood forest (CF), a major contributor to ecosystem structure and functioning in semiarid portions of the American Southwest. We tested whether floodplain development was linked to river regulation in the Upper Colorado River Basin (UCRB) by relating the extent of five developed land-cover categories as well as CF and other natural vegetation to catchment reservoir capacity, changes in total annual and annual peak discharge, and overall level of mainstem hydrologic alteration (small, moderate, or large) in 26 fourth-order subbasins. We also asked whether CF appeared to be in jeopardy at a regional level....
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This paper considers the risk of drought and develops drought scenarios for use in the study of severe sustained drought in the southwestern United States. The focus is on the Colorado River basin and regions to which Colorado River water is exported, especially southern California, which depends on water from the Colorado River as well as the four major rivers in northern California. Drought scenarios are developed using estimates of unimpaired historic streamflow as well as reconstructions of streamflow based on tree ring widths. Drought scenarios in the Colorado River are defined on the basis of annual flow at Lees Ferry. Possible spatial manifestations of the Colorado River drought scenarios for input into a...
In the western United States many rivers experience high salinity resulting from natural and anthropogenic sources. This impacts the water quality and hence, is closely monitored. The salinity is closely linked with streamflow quantity in that, a higher flow brings with it more salt but also provides substantial dilution to reduce the salt concentration and vice-versa during low flow regimes. Decision makers typically plan strategies for salinity mitigation and evaluate impacts of water management policy options on salinity in the basin using decision support models. These models require statistically consistent basin wide scenarios of streamflow and salinity. Recognizing this need, we develop a basin wide stochastic...
The US Geological Survey has maintained a network of stations to collect samples for the measurement of tritium concentrations in precipitation and streamflow since the early 1960s. Tritium data from outflow waters of river basins draining 4500?75000 km2 are used to determine average residence times of water within the basins. The basins studied are the Colorado River above Cisco, Utah; the Kissimmee River above Lake Okeechobee, Florida; the Mississippi River above Anoka, Minnesota; the Neuse River above Streets Ferry Bridge near Vanceboro, North Carolina; the Potomac River above Point of Rocks, Maryland; the Sacramento River above Sacramento, California; the Susquehanna River above Harrisburg, Pennsylvania. The...
map background search result map search result map The source hydrology of severe sustained drought in the southwestern United States Associations of interdecadal/interannual climate variability and long-term colorado river basin streamflow Associations of interdecadal/interannual climate variability and long-term colorado river basin streamflow The source hydrology of severe sustained drought in the southwestern United States