Gregory E Schwarz
Gregory Schwarz is an Economist with the USGS Water Resources Mission Area.
Science and Products
Filter Total Items: 67
Estimates of diffuse phosphorus sources in surface waters of the United States using a spatially referenced watershed model
The statistical watershed model SPARROW (SPAtially Referenced Regression On Watershed attributes) was used to estimate the sources and transport of total phosphorus (TP) in surface waters of the United States. We calibrated the model using stream measurements of TP from 336 watersheds of mixed land use and spatial data on topography, soils, stream hydrography, and land use (agriculture, forest, sh
Authors
R. B. Alexander, R. A. Smith, G. E. Schwarz
ERF1_2 -- Enhanced River Reach File 2.0
The digital segmented network based on watershed boundaries, ERF1_2, includes enhancements to the U.S. Environmental Protection Agency's River Reach File 1 (RF1) (USEPA, 1996; DeWald and others, 1985) to support national and regional-scale surface water-quality modeling. Alexander and others (1999) developed ERF1, which assessed the hydrologic integrity of the digital reach traces and calculated
Authors
Jacqueline V. Nolan, John W. Brakebill, Richard B. Alexander, Gregory E. Schwarz
Natural background concentrations of nutrients in streams and rivers of the conterminous United States
Determining natural background concentrations of nutrients in watersheds in the developed world has been hampered by a lack of pristine sampling sites covering a range of climatic conditions and basin sizes. Using data from 63 minimally impacted U.S. Geological Survey reference basins, we developed empirical models of the background yield of total nitrogen (TN) and total phosphorus (TP) from small
Authors
R. A. Smith, R. B. Alexander, G. E. Schwarz
Estimation of nitrogen yields and loads from basins draining to Long Island Sound, 1988–98
Monitoring data on total nitrogen concentrations
and streamflow were used to estimate annual
nonpoint nitrogen loads for 1988?98 at 28 monitoring
sites and 26 unmonitored basins that drain
to Long Island Sound. The estimated total nitrogen
yields at monitoring sites were used with basin
characteristics and ancillary data to develop a
multiple-linear regression equation to estimate
nonpoint
Authors
John R. Mullaney, Gregory E. Schwarz, Elaine C. Todd Trench
A spatially referenced regression model (SPARROW) for suspended sediment in streams of the Conterminous U.S.
Suspended sediment has long been recognized as an important contaminant affecting water resources. Besides its direct role in determining water clarity, bridge scour and reservoir storage, sediment serves as a vehicle for the transport of many binding contaminants, including nutrients, trace metals, semi-volatile organic compounds, a nd numerous pesticides (U.S. Environmental Protection Agency, 20
Authors
Gregory E. Schwarz, Richard A. Smith, Richard B. Alexander, John R. Gray
A field and statistical modeling study to estimate irrigation water use at Benchmark Farms study sites in southwestern Georgia, 1995-96
A benchmark irrigation monitoring network of farms located in a 32-county area in southwestern Georgia was established in 1995 to improve estimates of irrigation water use. A stratified random sample of 500 permitted irrigators was selected from a data base--maintained by the Georgia Department of Natural Resources, Georgia Environmental Protection Division, Water Resources Management Branch--to o
Authors
Julia L. Fanning, Gregory E. Schwarz, William C. Lewis
A comparison of load estimates using total suspended solids and suspended-sediment concentration data
This paper presents the results to-date from a continuing investigation into the differences between total suspended solids (TSS) and suspended-sediment concentration (SSC) data and the ramifications of using each type of data to estimate sediment loads. It compares estimates of annual suspended-sediment loads that were made using regression equations developed from paired TSS and SSC data, to ann
Authors
G.D. Glysson, J. R. Gray, G. E. Schwarz
Price current-meter standard rating development by the U.S. geological survey
The U.S. Geological Survey has developed new standard rating tables for use with Price type AA and pygmy current meters, which are employed to measure streamflow velocity. Current-meter calibration data, consisting of the rates of rotation of meters at several different constant water velocities, have shown that the original rating tables are no longer representative of the average responsiveness
Authors
E. F. Hubbard, G. E. Schwarz, K.G. Thibodeaux, L.M. Turcios
A spatially referenced regression model (SPARROW) for suspended sediment in streams of the conterminous U.S.
Suspended sediment has long been recognized as an important contaminant affecting water resources. Besides its direct role in determining water clarity, bridge scour and reservoir storage, sediment serves as a vehicle for the transport of many binding contaminants, including nutrients, trace metals, semi-volatile organic compounds, and numerous pesticides (U.S. Environmental Protection Agency, 200
Authors
Gregory E. Schwarz, Richard A. Smith, Richard B. Alexander, John R. Gray
Effect of stream channel size on the delivery of nitrogen to the Gulf of Mexico
An increase in the flux of nitrogen from the Mississippi river during the latter half of the twentieth century has caused eutrophication and chronic seasonal hypoxia in the shallow waters of the Louisiana shelf in the northern Gulf of Mexico. This has led to reductions in species diversity, mortality of benthic communities and stress in fishery resources. There is evidence for a predominantly anth
Authors
R. B. Alexander, R. A. Smith, G. E. Schwarz
Details of current-meter rating table development by the U.S. Geological Survey
No abstract available.
Authors
Ernest F. Hubbard, Gregory E. Schwarz, Kirk G. Thibodeaux, Lisa M. Turcios
Comparability of suspended-sediment concentration and total suspended solids data
Two laboratory analytical methods ? suspended-sediment concentration (SSC) and total suspended solids (TSS) ? are predominantly used to quantify concentrations of suspended solid-phase material in surface waters of the United States. The analytical methods differ. SSC data are produced by measuring the dry weight of all the sediment from a known volume of a water-sediment mixture. TSS data are pro
Authors
John R. Gray, G.D. Glysson, L.M. Turcios, G. E. Schwarz
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Filter Total Items: 67
Estimates of diffuse phosphorus sources in surface waters of the United States using a spatially referenced watershed model
The statistical watershed model SPARROW (SPAtially Referenced Regression On Watershed attributes) was used to estimate the sources and transport of total phosphorus (TP) in surface waters of the United States. We calibrated the model using stream measurements of TP from 336 watersheds of mixed land use and spatial data on topography, soils, stream hydrography, and land use (agriculture, forest, shAuthorsR. B. Alexander, R. A. Smith, G. E. SchwarzERF1_2 -- Enhanced River Reach File 2.0
The digital segmented network based on watershed boundaries, ERF1_2, includes enhancements to the U.S. Environmental Protection Agency's River Reach File 1 (RF1) (USEPA, 1996; DeWald and others, 1985) to support national and regional-scale surface water-quality modeling. Alexander and others (1999) developed ERF1, which assessed the hydrologic integrity of the digital reach traces and calculatedAuthorsJacqueline V. Nolan, John W. Brakebill, Richard B. Alexander, Gregory E. SchwarzNatural background concentrations of nutrients in streams and rivers of the conterminous United States
Determining natural background concentrations of nutrients in watersheds in the developed world has been hampered by a lack of pristine sampling sites covering a range of climatic conditions and basin sizes. Using data from 63 minimally impacted U.S. Geological Survey reference basins, we developed empirical models of the background yield of total nitrogen (TN) and total phosphorus (TP) from smallAuthorsR. A. Smith, R. B. Alexander, G. E. SchwarzEstimation of nitrogen yields and loads from basins draining to Long Island Sound, 1988–98
Monitoring data on total nitrogen concentrations and streamflow were used to estimate annual nonpoint nitrogen loads for 1988?98 at 28 monitoring sites and 26 unmonitored basins that drain to Long Island Sound. The estimated total nitrogen yields at monitoring sites were used with basin characteristics and ancillary data to develop a multiple-linear regression equation to estimate nonpointAuthorsJohn R. Mullaney, Gregory E. Schwarz, Elaine C. Todd TrenchA spatially referenced regression model (SPARROW) for suspended sediment in streams of the Conterminous U.S.
Suspended sediment has long been recognized as an important contaminant affecting water resources. Besides its direct role in determining water clarity, bridge scour and reservoir storage, sediment serves as a vehicle for the transport of many binding contaminants, including nutrients, trace metals, semi-volatile organic compounds, a nd numerous pesticides (U.S. Environmental Protection Agency, 20AuthorsGregory E. Schwarz, Richard A. Smith, Richard B. Alexander, John R. GrayA field and statistical modeling study to estimate irrigation water use at Benchmark Farms study sites in southwestern Georgia, 1995-96
A benchmark irrigation monitoring network of farms located in a 32-county area in southwestern Georgia was established in 1995 to improve estimates of irrigation water use. A stratified random sample of 500 permitted irrigators was selected from a data base--maintained by the Georgia Department of Natural Resources, Georgia Environmental Protection Division, Water Resources Management Branch--to oAuthorsJulia L. Fanning, Gregory E. Schwarz, William C. LewisA comparison of load estimates using total suspended solids and suspended-sediment concentration data
This paper presents the results to-date from a continuing investigation into the differences between total suspended solids (TSS) and suspended-sediment concentration (SSC) data and the ramifications of using each type of data to estimate sediment loads. It compares estimates of annual suspended-sediment loads that were made using regression equations developed from paired TSS and SSC data, to annAuthorsG.D. Glysson, J. R. Gray, G. E. SchwarzPrice current-meter standard rating development by the U.S. geological survey
The U.S. Geological Survey has developed new standard rating tables for use with Price type AA and pygmy current meters, which are employed to measure streamflow velocity. Current-meter calibration data, consisting of the rates of rotation of meters at several different constant water velocities, have shown that the original rating tables are no longer representative of the average responsivenessAuthorsE. F. Hubbard, G. E. Schwarz, K.G. Thibodeaux, L.M. TurciosA spatially referenced regression model (SPARROW) for suspended sediment in streams of the conterminous U.S.
Suspended sediment has long been recognized as an important contaminant affecting water resources. Besides its direct role in determining water clarity, bridge scour and reservoir storage, sediment serves as a vehicle for the transport of many binding contaminants, including nutrients, trace metals, semi-volatile organic compounds, and numerous pesticides (U.S. Environmental Protection Agency, 200AuthorsGregory E. Schwarz, Richard A. Smith, Richard B. Alexander, John R. GrayEffect of stream channel size on the delivery of nitrogen to the Gulf of Mexico
An increase in the flux of nitrogen from the Mississippi river during the latter half of the twentieth century has caused eutrophication and chronic seasonal hypoxia in the shallow waters of the Louisiana shelf in the northern Gulf of Mexico. This has led to reductions in species diversity, mortality of benthic communities and stress in fishery resources. There is evidence for a predominantly anthAuthorsR. B. Alexander, R. A. Smith, G. E. SchwarzDetails of current-meter rating table development by the U.S. Geological Survey
No abstract available.AuthorsErnest F. Hubbard, Gregory E. Schwarz, Kirk G. Thibodeaux, Lisa M. TurciosComparability of suspended-sediment concentration and total suspended solids data
Two laboratory analytical methods ? suspended-sediment concentration (SSC) and total suspended solids (TSS) ? are predominantly used to quantify concentrations of suspended solid-phase material in surface waters of the United States. The analytical methods differ. SSC data are produced by measuring the dry weight of all the sediment from a known volume of a water-sediment mixture. TSS data are proAuthorsJohn R. Gray, G.D. Glysson, L.M. Turcios, G. E. Schwarz