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At least 1,171 records · Page 65Linked to original sources
USGS1998

Concentrations and loads of nitrogen and phosphorus in the Yazoo River, northwestern Mississippi, 1996-97

Increased nutrient loading to the Gulf of Mexico from off-continent flux has been identified as contributing to the increase in the areal extent of the low dissolved-oxygen zone that develops annually off the coast of Louisiana and Texas. The proximity of the Yazoo River Basin in northwestern Mississippi to the Gulf of Mexico, and the intensive agriculture in the basin have lead to speculation that the Yazoo River Basin contributes a disproportionate amount of nitrogen and phosphorus to the Mississippi River and ultimately the Gulf of Mexico. Water samples from the Yazoo River were collected during 1996 and 1997 and were analyzed for total nitrogen, nitrate as nitrogen, total phosphorus, and orthophosphorus as part of the U.S. Geological Survey?s National Water-Quality Assessment Program. These data were used to compute annual loads of nitrogen and phosphorus discharged from the Yazoo River for 1996 and 1997. Annual loads of nitrogen and phosphorus were calculated by two methods. The first used multivariate regression and the second multiplied the mean annual concentration by the total annual flow. Load estimates based on the product of the mean annual concentration and the total annual flow were within the 95 percent confidence interval for the load calculated by multivariate regression in all cases. The Yazoo River loads, compared to long-term annual loads in the Mississippi River, indicated that the Yazoo River was contributing 2.3 percent or less of the total nitrogen load, 5.7 percent or less of the total phosphorus load, and 1 percent or less of the nitrate load in 1996 and 1997. The total nitrogen load from the Yazoo River Basin into the Mississippi River and ultimately the Gulf of Mexico was proportional to its discharge, the nitrate load was less than expected, whereas the total phosphorus load was slightly higher than expected based on discharge.

Mississippi↗
USGS2002

Nesting ecology of tundra swans on the coastal Yukon-Kuskokwim Delta, Alaska

Nesting ecology of Tundra Swans (Cygnus columbianus columbianus) was studies the Kashunuk River near Old Chevak (61A?26a??N, 165A?27a??W), on the Yukon-Kuskokwim Delta of western Alaska from 1988-2000. Annual variation in snow-melt chronology, nesting phenology, nesting density, clutch size and nest success was examined. The same area (approximately 23 kmA?) was searched each year and nests were found as early as possible in the laying period. Laying initiation dates ranged from 1-27 May and hatch dates from 12 June a?? 4 July among pairs and years of study. The peak arrival of Tundra Swans and the phenology of nest initiation and hatch were highly correlated with the progression of ice and snow melt in spring. Nest density averaged 0.71 kmA? and 89% of nesting pairs hatched at least one egg. Incubation period ranged from 26 to 33 days with a median of 30 days. Clutch size varied significantly among years, driven by a low mean value of 3.4 eggs in 1999. Clutch sizes were generally larger than found in previous investigations on the Yukon-Kuskokwim Delta, and nearly one egg larger than reported for clutches from Alaskaa??s North Slope (=70A?N). There was no indication of reduced clutch size in years of late spring snow melt, although nesting density tended to be lower.

Waterbirds↗
USGS2019

Digital database of the geologic map of the middle east rift geothermal subzone, Kīlauea Volcano, Hawai‘i

This database release contains all the information used to produce Geologic Investigations Series I-2614 ( https://pubs.usgs.gov/imap/2614/ ). The main component of this digital release is a geodatabase prepared using ArcGIS, but Esri shapefiles are included as well. Kīlauea is an active shield volcano in the southeastern part of the Island of Hawai‘i. The middle East Rift Zone (MERZ) map includes about 27 square kilometers of the MERZ and shows the distribution of the products of 34 separate eruptions during late Holocene time. Lava flows erupted during 1983–86 have reached the mapped area. The subaerial part of the MERZ is 3–4 km wide and about 18 km long. It is a constructional ridge, 50–150 m above the adjoining terrain, marked by low spatter ramparts and cones as high as 60 m. Lava typically flowed either northeast or southeast, depending on vent location relative to the topographic crest of the rift zone. The MERZ receives more than 100 inches of rainfall annually and is covered by tropical rain forest. Vegetation begins to grow on lava a few months after its eruption. Relative heights of trees can be a guide to relative ages of underlying lava flows, but proximity to faults, presence of easily weathered cinders, and human activity also affect the rate of growth. The rocks have been grouped into five basic age groups. The framework for the ages assigned is provided by eight radiocarbon ages from nearby mapping by the authors and a single date from within this investigation area. The numerical ages are supplemented by observations of stratigraphic relations, degree of weathering, soil development, and vegetative cover.

Hawaii↗
USGS1994

Estimation of Magnitude and Frequency of Floods for Streams on the Island of Oahu, Hawaii

This report describes techniques for estimating the magnitude and frequency of floods for the island of Oahu. The log-Pearson Type III distribution and methodology recommended by the Interagency Committee on Water Data was used to determine the magnitude and frequency of floods at 79 gaging stations that had 11 to 72 years of record. Multiple regression analysis was used to construct regression equations to transfer the magnitude and frequency information from gaged sites to ungaged sites. Oahu was divided into three hydrologic regions to define relations between peak discharge and drainage-basin and climatic characteristics. Regression equations are provided to estimate the 2-, 5-, 10-, 25-, 50-, and 100-year peak discharges at ungaged sites. Significant basin and climatic characteristics included in the regression equations are drainage area, median annual rainfall, and the 2-year, 24-hour rainfall intensity. Drainage areas for sites used in this study ranged from 0.03 to 45.7 square miles. Standard error of prediction for the regression equations ranged from 34 to 62 percent. Peak-discharge data collected through water year 1988, geographic information system (GIS) technology, and generalized least-squares regression were used in the analyses. The use of GIS seems to be a more flexible and consistent means of defining and calculating basin and climatic characteristics than using manual methods. Standard errors of estimate for the regression equations in this report are an average of 8 percent less than those published in previous studies.

Water-Resources Investigations Report↗
USGS2016

Estimating flood magnitude and frequency at gaged and ungaged sites on streams in Alaska and conterminous basins in Canada, based on data through water year 2012

Estimates of the magnitude and frequency of floods are needed across Alaska for engineering design of transportation and water-conveyance structures, flood-insurance studies, flood-plain management, and other water-resource purposes. This report updates methods for estimating flood magnitude and frequency in Alaska and conterminous basins in Canada. Annual peak-flow data through water year 2012 were compiled from 387 streamgages on unregulated streams with at least 10 years of record. Flood-frequency estimates were computed for each streamgage using the Expected Moments Algorithm to fit a Pearson Type III distribution to the logarithms of annual peak flows. A multiple Grubbs-Beck test was used to identify potentially influential low floods in the time series of peak flows for censoring in the flood frequency analysis. For two new regional skew areas, flood-frequency estimates using station skew were computed for stations with at least 25 years of record for use in a Bayesian least-squares regression analysis to determine a regional skew value. The consideration of basin characteristics as explanatory variables for regional skew resulted in improvements in precision too small to warrant the additional model complexity, and a constant model was adopted. Regional Skew Area 1 in eastern-central Alaska had a regional skew of 0.54 and an average variance of prediction of 0.45, corresponding to an effective record length of 22 years. Regional Skew Area 2, encompassing coastal areas bordering the Gulf of Alaska, had a regional skew of 0.18 and an average variance of prediction of 0.12, corresponding to an effective record length of 59 years. Station flood-frequency estimates for study sites in regional skew areas were then recomputed using a weighted skew incorporating the station skew and regional skew. In a new regional skew exclusion area outside the regional skew areas, the density of long-record streamgages was too sparse for regional analysis and station skew was used for all estimates. Final station flood frequency estimates for all study streamgages are presented for the 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent annual exceedance probabilities. Regional multiple-regression analysis was used to produce equations for estimating flood frequency statistics from explanatory basin characteristics. Basin characteristics, including physical and climatic variables, were updated for all study streamgages using a geographical information system and geospatial source data. Screening for similar-sized nested basins eliminated hydrologically redundant sites, and screening for eligibility for analysis of explanatory variables eliminated regulated peaks, outburst peaks, and sites with indeterminate basin characteristics. An ordinary least‑squares regression used flood-frequency statistics and basin characteristics for 341 streamgages (284 in Alaska and 57 in Canada) to determine the most suitable combination of basin characteristics for a flood-frequency regression model and to explore regional grouping of streamgages for explaining variability in flood-frequency statistics across the study area. The most suitable model for explaining flood frequency used drainage area and mean annual precipitation as explanatory variables for the entire study area as a region. Final regression equations for estimating the 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent annual exceedance probability discharge in Alaska and conterminous basins in Canada were developed using a generalized least-squares regression. The average standard error of prediction for the regression equations for the various annual exceedance probabilities ranged from 69 to 82 percent, and the pseudo-coefficient of determination (pseudo-R 2 ) ranged from 85 to 91 percent. The regional regression equations from this study were incorporated into the U.S. Geological Survey StreamStats program for a limited area of the State—the Cook Inlet Basin. StreamStats is a national web-based geographic information system application that facilitates retrieval of streamflow statistics and associated information. StreamStats retrieves published data for gaged sites and, for user-selected ungaged sites, delineates drainage areas from topographic and hydrographic data, computes basin characteristics, and computes flood frequency estimates using the regional regression equations.

Alaska↗
USGS1965

Ground-water levels in observation wells in Oklahoma, 1963-64

The investigation of the ground-water resources of Oklahoma by the U.S. Geological Survey in cooperation with the Oklahoma Water Resources Board includes a continuing program to collect records of water levels in selected observation wells on a systematic basis. These water-level records: (1) provide an index to available ground-water supplies; (2) facilitate the prediction of trends in water levels that will indicate likely changes in storage; (3) aid in the prediction of the base flow of streams; (4) provide information for use in basic research; (5) provide long-time continuous records of fluctuations of water levels in representative wells; and (6) serve as a framework to which other types of hydrologic data my be related. Prior to 1956, measurements of water levels in observation wells in Oklahoma were included in water-supply papers published annually by the U.S. Geological Survey. Beginning with the 1956 calendar year, however, Geological Survey water-level reports will contain only records of a selected network of observation wells, and will be published at 5-year intervals. The first of this series, for the 1956-59 period was published in 1962. This report has been prepared primarily to present water-level records of wells not included in the Federal network. However, for the sake of completeness it includes water-level records of Federal wells that either have been or will be published in water-supply papers since 1955. This report, which contains water-level records for the 2-year period (1963-64), is the third of a series presenting water-level records for all permanent observations wells in Oklahoma. The first report, published in 1963, contains water-level records for the 5-year period of (1956-60). The second report, published in 1964, contains water-level records for the 2-year period (1961-62.) (available as photostat copy only)

Open-File Report↗
USGS1967

Ground-water levels in observation wells in Oklahoma, 1965-66

The investigation of the ground-water resources of Oklahoma by the U.S. Geological Survey in cooperation with the Oklahoma Water Resources Board includes a continuing program to collect records of water levels in selected observation wells on a systematic basis. These water-level records: (1) provide an index to available ground-water supplies; (2) facilitate the prediction of trends in water levels that will indicate likely changes in storage; (3) aid in the prediction of the base flow of streams; (4) provide information for use in basic research; (5) provide long-time continuous records of fluctuations of water levels in representative wells; and (6) serve as a framework to which other types of hydrologic data my be related. Prior to 1956, measurements of water levels in observation wells in Oklahoma were included in water-supply papers published annually by the U.S. Geological Survey. Beginning with the 1956 calendar year, however, Geological Survey water-level reports will contain only records of a selected network of observation wells, and will be published at 5-year intervals. The first of this series, for the 1956-59 period was published in 1962. This report has been prepared primarily to present water-level records of wells not included in the Federal network. However, for the sake of completeness it includes water-level records of Federal wells that either have been or will be published in water-supply papers since 1955. This report, which contains water-level records for the 2-year period (1965-66), is the fourth in a series presenting water-level records for all permanent observations wells in Oklahoma. The first report, published in 1963, contains water-level records for the 2-year period of (1961-62); the second report, published in 1964, contains water-level records for the 2-year period (1961-62); and the third report, published in 1965, contains water-level records for the 2-year period (1963-64). (available as photostat copy only)

Open-File Report↗
USGS2013

Evaporation from Lake Mead, Nevada and Arizona, March 2010 through February 2012

Evaporation from Lake Mead was measured using the eddy-covariance method for the 2-year period starting March 2010 and ending February 2012. When corrected for energy imbalances, annual eddy-covariance evaporation was 2,074 and 1,881 millimeters (81.65 and 74.07 inches), within the range of previous estimates. There was a 9-percent decrease in the evaporation rate and a 10-percent increase in the lake surface area during the second year of the study compared to the first. These offsetting factors resulted in a nearly identical 720 million cubic meters (584,000 acre feet) evaporation volume for both years. Monthly evaporation rates were best correlated with wind speed, vapor pressure difference, and atmospheric stability. Differences between individual monthly evaporation and mean monthly evaporation were as much as 20 percent. Net radiation provided most of the energy available for evaporative processes; however, advected heat from the Colorado River was an important energy source during the second year of the study. Peak evaporation lagged peak net radiation by 2 months because a larger proportion of the net radiation that reaches the lake goes to heating up the water column during the spring and summer months. As most of this stored energy is released, higher evaporation rates are sustained during fall months even though net radiation declines. The release of stored heat also fueled nighttime evaporation, which accounted for 37 percent of total evaporation. The annual energy-balance ratio was 0.90 on average and varied only 0.01 between the 2 years, thus implying that 90 percent of estimated available energy was accounted for by turbulent energy measured using the eddy-covariance method. More than 90 percent of the turbulent-flux source area represented the open-water surface, and 94 percent of 30-minute turbulent-flux measurements originated from wind directions where the fetch ranged from 2,000 to 16,000 meters. Evaporation uncertainties were estimated to be 5 to 7 percent. A secondary evaporation method, the Bowen ratio energy budget method, also was employed to measure evaporation from Lake Mead primarily as a validation of eddy-covariance evaporation measurements at annual timescales. There was good agreement between annual corrected eddy-covariance and Bowen ratio energy budget evaporation estimates, providing strong validation of these two largely independent methods. Annual Bowen ratio energy budget evaporation was 6 and 8 percent greater than eddy-covariance evaporation for the 2 study years, and both methods indicated there was a similar decrease in evaporation from the first to the second year. Both methods produced negative sensible heat fluxes during the same months, and there was a strong correlation between monthly Bowen ratios (R 2 = 0.94). The correlation between monthly evaporation (R 2 = 0.65), however, was not as strong. Monthly differences in evaporation were attributed primarily to heat storage estimate uncertainty.

Arizona;Nevada↗
USGS2020

Trends in concentration, loads, and sources of trace metals and nutrients in the Spokane River Watershed, northern Idaho, water years 1990–2018

A long history of mining and widespread metals contamination in the Coeur d’Alene River watershed and downstream into the Spokane River has led to the area’s designation as a Superfund site and to extensive, ongoing (as of 2020) remedial actions. Long-term water-quality and streamflow data, collected by the U.S. Geological Survey for up to 29 years at 20 sampling sites in the Coeur d’Alene, Spokane and St. Joe River watersheds, were analyzed to evaluate the impact of remedial actions on metals in surface water. Analyses focused on total and dissolved cadmium, zinc and lead. Trends in total phosphorus, total nitrogen and dissolved orthophosphate were also evaluated; although these nutrients are not constituents of concern for the Superfund site, they are important to the health of Coeur d’Alene Lake. Dissolved cadmium, zinc and lead concentrations were compared to ambient water-quality criteria at 20 sample sites. For the 12 sites with the most extensive data records, Weighted Regressions on Time, Discharge and Season (WRTDS) models were developed to estimate flow-normalized annual mean concentrations and flow-normalized annual total loads; these results were used to evaluate trends because flow-normalization dampens the impact of interannual streamflow variability on concentrations and loads. WRTDS models with Kalman filtering (WRTDS_K) were developed to estimate annual mean concentrations and annual total loads; these results were used to evaluate spatial patterns in constituent sources. Models were developed for total and dissolved cadmium, lead, and zinc; total phosphorus and nitrogen; and dissolved orthophosphate, although not all constituents were modeled for all sites due to limited sample sizes. Bootstrapped confidence intervals were constructed to determine the statistical likelihood of trends and the slope of trends in flow-normalized concentrations and loads during the period of record (13–29 years, depending on the site), water years 1999–2009, and water years 2009–18.

Idaho↗
USGS1983

Hydrogeology of the Sarasota-Port Charlotte area, Florida

The surficial and intermediate aquifers are the major source of public water supplies in the Sarasota-Port Charlotte, Florida, area because of the relatively poor quality of Floridan aquifer water. The hydrogeologic framework consists of the surficial aquifer, intermediate aquifers (Tamiami-upper Hawthorn and lower Hawthorn-upper Tampa aquifers) and confining beds, Floridan aquifer, and lower confining bed (or base of the Floridan aquifer). The quality of ground water in the surficial and intermediate aquifers is generally good, except in the western (coastal) and southern parts where saltwater intrusion or incomplete flushing of connate water has occurred. The mineral content of ground water generally increases with depth and areally from the northeast towards the west and south. A water budget for the study area shows that an average annual rainfall of 51.0 inches minus an evapotranspiration of 38.0 inches per year and streamflow of 12.5 inches per year leaves 0.5 inch per year of recharge to the surficial aquifer. Combined pumpage from the aquifers is 1.06 inches per year. A preliminary quasi-time dimensional model has been applied to the study area to check the reasonableness of the hydrogeologic framework defined and of aquifer parameters. The model was considered calibrated when the final head matrix was within plus or minus 5 feet of the starting head.

Florida↗
USGS1986

Manual for estimating selected streamflow characteristics of natural-flow streams in the Colorado River basin in Utah

Methods are presented for estimating 10 streamflow characteristics at three types of sites on natural flow streams in the Colorado River Basin in Utah. The streamflow characteristics include average discharge and annual maximum 1-, 7-, and 15-day mean discharges for recurrence intervals of 10, 50 and 100 years. At or near gaged sites, two methods weight gaging station data with regression equation values to estimate streamflow characteristics. At sites on ungaged streams, a method estimates streamflow characteristics using regression equations. The regression equations relate the streamflow characteristics to the following basin and climatic characteristics: contributing drainage area, mean basin elevation, mean annual precipitation, main channel slope, and forested area. Separate regression equations were developed for four hydrologically distinct regions in the study area. The standard error of estimate for the 10 streamflow characteristics ranges from 13% to 87%. Basin, climatic, and streamflow characteristics, available as of September 30, 1981, are presented for 135 gaging stations in Utah, Arizona, Colorado, and Wyoming. In addition, weighted estimates of the streamflow characteristics based on station data and the regression equation estimates are provided for most gaging stations. (Author 's abstract)

Water-Resources Investigations Report↗
USGS1986

Comparison of flood frequency estimates from synthetic and observed data on small drainage areas in Mississippi

In 1964 the U.S. Geological Survey in Mississippi expanded the small stream gaging network for collection of rainfall and runoff data to 92 stations. To expedite availability of flood frequency information a rainfall-runoff model using available long-term rainfall data was calibrated to synthesize flood peaks. Results obtained from observed annual peak flow data for 51 sites having 16 yr to 30 yr of annual peaks are compared with the synthetic results. Graphical comparison of the 2, 5, 10, 25, 50, and 100-year flood discharges indicate good agreement. The root mean square error ranges from 27% to 38% and the synthetic record bias from -9% to -18% in comparison with the observed record. The reduced variance in the synthetic results is attributed to use of only four long-term rainfall records and model limitations. The root mean square error and bias is within the accuracy considered to be satisfactory. (Author 's abstract)

Water-Resources Investigations Report↗
USGS1987

Water-quality variations in the Bull Run Watershed, Oregon, under 1978 to 1983 management conditions

During the period October 1978 to September 1983, the U.S. Geological Survey, in cooperation with the City of Portland (Oregon) Water Bureau, conducted a study in the Bull Run River basin to define the hydrologic characteristics of the basin, and to examine relations between basin characteristics (both natural and man-made) and stream water quality and quantity within the basin. Hydrologically, the 1978-1983 period can be characterized as representative of the long-term average, with no records of extreme events. Likewise, water quality constituent concentrations affected by quantity of streamflow are representative of average values and ranges and exclude values that would be obtained during periods of extreme events. Ranges of concentration of major anions and cations for surface water collected October 1978 to September 1983 are similar to values collected historically. The ratio of constituent to chloride values determined for precipitation data collected during the period June 1980 to September 1981 indicated that other sources besides seawater contributed to its composition. In ratios of constituents in precipitation, Bull Run values are similar to those of other remote sites in Alaska, Washington, and California. Comparisons of storm-related suspended sediment load to annual suspended sediment loads indicated that 62% to 78% of the total annual loads occurred in 3 to 4 days during an average year. Multiple-linear regression analysis using discharge, suspended sediment and specific conductance indicated that most of the variation in the annual values could be explained by naturally occurring processes within the basin. A nonparametric time-trend analysis of 24 water quantity and quality constituents showed no statistically significant trends with estimated slopes large enough to be readily measurable for a particular year. Four constituents that were sampled weekly (turbidity, specific conductance, silica, and phytoplankton) had statistically significant trends with slope indicators that might be measurable after 6 years. However, trend analysis on daily mean specific conductance and suspended sediment values does not confirm the weekly constituent trend results.

Oregon↗
USGS1977

Annual peak discharges from small drainage areas in Montana through September 1976

Annual peak discharge from small drainage areas is tabulated for 336 sites in Montana. The 1976 additions included data collected at 206 sites. The program which investigates the magnitude and frequency of floods from small drainage areas in Montana, was begun July 1, 1955. Originally 45 crest-stage gaging stations were established. The purpose of the program is to collect sufficient peak-flow data, which through analysis could provide methods for estimating the magnitude and frequency of floods at any point in Montana. The ultimate objective is to provide methods for estimating the 100-year flood with the reliability needed for road design. (Woodard-USGS)

Open-File Report↗
USGS1986

Maps showing altitude of the potentiometric surface and changes in water levels in the aquifer in the Sparta and Memphis Sands in eastern Arkansas, spring 1985

Aquifers in the Tertiary Sparta and Memphis Sands are a major source of water supply for much of eastern and south-central Arkansas. Major withdrawals occur from the aquifer for industrial and public supply, with generally lesser but locally significant amounts withdrawn for agricultural uses. Water level data from wells tapping the artesian aquifer in the Sparta and Memphis Sands indicate steadily declining water levels in some areas where relatively large withdrawals occur. In addition, a simulation of water levels using projected withdrawals to the year 1990 indicated increasing water level declines in the aquifer. Because of the potential quantity and quality problems, the continual monitoring of water levels in the aquifer in the Sparta and Memphis Sands is essential for proper aquifer management and the continuation of the use of the aquifer as a major source of water for much of eastern and south-central Arkansas. The U.S. Geological Survey with the cooperation of the Arkansas Geological Commission has been monitoring water levels in the aquifer in the Sparta and Memphis Sands annually throughout the aquifer 's extent within the State of Arkansas. This report, prepared in cooperation with the Arkansas Geological Commission and the Arkansas Soil and Water Conservation Commission interprets water level data through hydrologic maps of the potentiometric surface and water level changes. The potentiometric surface map is based on water levels collected in the spring of 1985. The water level change map is based on a comparison of water levels collected in the spring of 1980 and 1985. This report includes the Sparta Sand and most of the Memphis Sand aquifer within the State of Arkansas. Little or no data are available in the northeastern part of the State where limited withdrawals from the aquifer occur. (Lantz-PTT)

Water-Resources Investigations Report↗
USGS2000

Mountain-front recharge along the eastern side of the Middle Rio Grande Basin, central New Mexico

Mountain-front recharge, which generally occurs along the margins of alluvial basins, can be a large part of total recharge to the aquifer system in such basins. Mountain-front recharge occurs as the result of infiltration of flow from streams that have headwaters in the mountainous areas adjacent to alluvial basins and ground- water flow from the aquifers in the mountainous areas to the aquifer in the alluvial basin. This report presents estimates of mountain-front recharge to the basin-fill aquifer along the eastern side of the Middle Rio Grande Basin in central New Mexico. The basin is a structural feature that contains a large thickness of basin-fill deposits, which compose the main aquifer in the basin. The basin is bounded along the eastern side by mountains composed of crystalline rocks of Precambrian age and sedimentary rocks of Paleozoic age. Precipitation is much larger in the mountains than in the basin; many stream channels debouch from the mountainous area to the basin. Chloride-balance and water-yield regression methods were used to estimate mountain-front recharge. The chloride-balance method was used to calculate a chloride balance in watersheds in the mountainous areas along the eastern side of the basin (subareas). The source of chloride to these watersheds is bulk precipitation (wet and dry deposition). Chloride leaves these watersheds as mountain-front recharge. The water-yield regression method was used to determine the streamflow from the mountainous watersheds at the mountain front. This streamflow was assumed to be equal to mountain-front recharge because most of this streamflow infiltrates and recharges the basin-fill aquifer. Total mountain-front recharge along the eastern side of the Middle Rio Grande Basin was estimated to be about 11,000 acre- feet per year using the chloride-balance method and about 36,000 and 38,000 acre-feet per year using two water-yield regression equations. There was a large range in the recharge estimates in a particular subarea using the different methods. Mountain-front recharge ranged from 0.7 to 15 percent of total annual precipitation in the subareas (percent recharge). Some of the smallest values of percent recharge were in the subareas in the southern part of the basin, which generally have low altitudes. The larger percent-recharge values were from subareas with higher altitudes. With existing information, determining which of the mountain- front recharge estimates is most accurate and the reasons for discrepancies among the different estimates is not possible. The chloride-balance method underestimates recharge if the chloride concentration used in the calculations for precipitation is too small or the chloride concentration in recharge is too large. Water-yield regression methods overestimate recharge if the amount of evapotranspiration of water that infiltrates into the channel bed of arroyos during runoff from summer thunderstorms is large.

Water-Resources Investigations Report↗
USGS2017

A review of surface energy balance models for estimating actual evapotranspiration with remote sensing at high spatiotemporal resolution over large extents

Many approaches have been developed for measuring or estimating actual evapotranspiration ( ET a ), and research over many years has led to the development of remote sensing methods that are reliably reproducible and effective in estimating ET a . Several remote sensing methods can be used to estimate ET a at the high spatial resolution of agricultural fields and the large extent of river basins. More complex remote sensing methods apply an analytical approach to ET a estimation using physically based models of varied complexity that require a combination of ground-based and remote sensing data, and are grounded in the theory behind the surface energy balance model. This report, funded through cooperation with the International Joint Commission, provides an overview of selected remote sensing methods used for estimating water consumed through ET a and focuses on Mapping Evapotranspiration at High Resolution with Internalized Calibration (METRIC) and Operational Simplified Surface Energy Balance (SSEBop), two energy balance models for estimating ET a that are currently applied successfully in the United States. The METRIC model can produce maps of ET a at high spatial resolution (30 meters using Landsat data) for specific areas smaller than several hundred square kilometers in extent, an improvement in practice over methods used more generally at larger scales. Many studies validating METRIC estimates of ET a against measurements from lysimeters have shown model accuracies on daily to seasonal time scales ranging from 85 to 95 percent. The METRIC model is accurate, but the greater complexity of METRIC results in greater data requirements, and the internalized calibration of METRIC leads to greater skill required for implementation. In contrast, SSEBop is a simpler model, having reduced data requirements and greater ease of implementation without a substantial loss of accuracy in estimating ET a . The SSEBop model has been used to produce maps of ET a over very large extents (the conterminous United States) using lower spatial resolution (1 kilometer) Moderate Resolution Imaging Spectroradiometer (MODIS) data. Model accuracies ranging from 80 to 95 percent on daily to annual time scales have been shown in numerous studies that validated ET a estimates from SSEBop against eddy covariance measurements. The METRIC and SSEBop models can incorporate low and high spatial resolution data from MODIS and Landsat, but the high spatiotemporal resolution of ET a estimates using Landsat data over large extents takes immense computing power. Cloud computing is providing an opportunity for processing an increasing amount of geospatial “big data” in a decreasing period of time. For example, Google Earth Engine TM has been used to implement METRIC with automated calibration for regional-scale estimates of ET a using Landsat data. The U.S. Geological Survey also is using Google Earth Engine TM to implement SSEBop for estimating ET a in the United States at a continental scale using Landsat data.

Scientific Investigations Report↗
USGS2009

Identifying Hydrologic Processes in Agricultural Watersheds Using Precipitation-Runoff Models

Understanding the fate and transport of agricultural chemicals applied to agricultural fields will assist in designing the most effective strategies to prevent water-quality impairments. At a watershed scale, the processes controlling the fate and transport of agricultural chemicals are generally understood only conceptually. To examine the applicability of conceptual models to the processes actually occurring, two precipitation-runoff models - the Soil and Water Assessment Tool (SWAT) and the Water, Energy, and Biogeochemical Model (WEBMOD) - were applied in different agricultural settings of the contiguous United States. Each model, through different physical processes, simulated the transport of water to a stream from the surface, the unsaturated zone, and the saturated zone. Models were calibrated for watersheds in Maryland, Indiana, and Nebraska. The calibrated sets of input parameters for each model at each watershed are discussed, and the criteria used to validate the models are explained. The SWAT and WEBMOD model results at each watershed conformed to each other and to the processes identified in each watershed's conceptual hydrology. In Maryland the conceptual understanding of the hydrology indicated groundwater flow was the largest annual source of streamflow; the simulation results for the validation period confirm this. The dominant source of water to the Indiana watershed was thought to be tile drains. Although tile drains were not explicitly simulated in the SWAT model, a large component of streamflow was received from lateral flow, which could be attributed to tile drains. Being able to explicitly account for tile drains, WEBMOD indicated water from tile drains constituted most of the annual streamflow in the Indiana watershed. The Nebraska models indicated annual streamflow was composed primarily of perennial groundwater flow and infiltration-excess runoff, which conformed to the conceptual hydrology developed for that watershed. The hydrologic processes represented in the parameter sets resulting from each model were comparable at individual watersheds, but varied between watersheds. The models were unable to show, however, whether hydrologic processes other than those included in the original conceptual models were major contributors to streamflow. Supplemental simulations of agricultural chemical transport could improve the ability to assess conceptual models.

Scientific Investigations Report↗