Gregory Schwarz is an Economist with the USGS Water Resources Mission Area.
Science and Products
River Corridor hot spots for biogeochemical processing: a continental scale synthesis
Rivers are the veins of the landscape, providing environmental benefits that are disproportionately high relative to their aerial extent; shedding flood waters, hosting aquatic ecosystems, transporting solutes and energy-rich materials, and storing and transforming pollutants into less harmful forms. From uplands to the coasts, rivers facilitate key biogeochemical reactions that cumulatively influ
Mean seasonal SPARROW model inputs and simulated nitrogen and phosphorus loads for the Northeastern United States 2002 base year
This U.S. Geological Survey (USGS) data release includes input and output tabular files associated with mean seasonal 2002 simulations of total nitrogen and total phosphorus loads of the northeastern United States. The mean seasonal (MS) simulations are performed using a dynamic configuration of the USGS's Spatially Referenced Regression On Watershed attributes (dynamicSPARROW-MS) model, nonlinear
Nutrient Load Data used to Quantify Regional Effects of Agricultural Best Management Practices: An application of the 2012 SPARROW models for the Midwest, Northeast, and Southeast United States
Nitrogen and phosphorus losses from agricultural areas have impacted the water quality of downstream rivers, lakes, and oceans. As a result, investment in the adoption of agricultural best management practices (BMPs) has grown but assessments of their effectiveness at large spatial scales have been sparse. This study applies regional Spatially Referenced Regression On Watershed-attributes (SPARROW
Select Attributes for NHDPlus Version 2.1 Reach Catchments and Modified Network Routed Upstream Watersheds for the Conterminous United States (ver. 4.0, August 2023)
This metadata record describes a series of data sets of natural and anthropogenic landscape features linked to NHDPlus Version 2.1's (NHDPlusV2) approximately 2.7 million stream segments, their associated catchments, and their upstream watersheds within the conterminous United States. These data were developed by the Hydrologic Sytem's Team (HST) within the the United States Geological Survey's (
Inputs and Selected Predictions of the CBTN_v5 and CBTP_v5 SPARROW Models for the Chesapeake Bay Watershed
The CBTN_v5 and CBTP_v5 SPARROW models were developed to support inferences about causes of observed changes in nitrogen and phosphorus (respectively) fluxes in Chesapeake Bay tributaries between 1992 and 2012. Model inputs and outputs are included in three files, which are described below. Detailed documentation of the SPARROW modeling technique is available at https://pubs.er.usgs.gov/publicatio
Filter Total Items: 66
Sand- and gravel-trapping efficiencies derived for four types of pressure-difference bedload samplers
Bedload-trapping efficiencies (coefficients) were derived for four types of pressure-difference bedload samplers at the St. Anthony Falls Laboratory, University of Minnesota during the first two phases of flume experiments in January-March, 2006, referred to as “StreamLab06.” The bedload-sampler research component was part of a series of community-led, large-scale laboratory experiments performed
Authors
John Gray, Joel T. Groten, Jonathan A. Czuba, Gregory E. Schwarz, Kyle Strom, Panayiotis Diplas
Predicting near-term effects of climate change on nitrogen transport to Chesapeake Bay
Understanding effects of climate change on nitrogen fate and transport in the environment is critical to nutrient management. We used climate projections within a previously calibrated spatially referenced regression (SPARROW) model to predict effects of expected climate change over 1995 through 2025 on total nitrogen fluxes to Chesapeake Bay and in watershed streams. Assuming nitrogen inputs and
Authors
Scott Ator, Gregory E. Schwarz, Andrew Sekellick, Gopal Bhatt
Quantifying regional effects of best management practices on nutrient losses from agricultural lands
Nitrogen (N) and phosphorus (P) losses from agricultural areas have degraded the water quality of downstream rivers, lakes, and oceans. As a result, investment in the adoption of agricultural best management practices (BMPs) has grown, but assessments of their effectiveness at large spatial scales have lagged. This study applies regional Spatially Referenced Regression On Watershed-attributes (SPA
Authors
Victor L. Roland, Ana María García, David A. Saad, Scott W. Ator, Dale M. Robertson, Gregory E. Schwarz
Seasonally dynamic nutrient modeling quantifies storage lags and time-varying reactivity across large river basins
Nutrients that have gradually accumulated in soils, groundwaters, and river sediments in the United States over the past century can remobilize and increase current downstream loading, obscuring effects of conservation practices aimed at protecting water resources. Drivers of storage accumulation and release of nutrients are poorly understood at the spatial scale of basins to watersheds. Predictin
Authors
Noah Schmadel, Judson Harvey, Gregory E. Schwarz
Instruments, methods, rationale, and derived data used to quantify and compare the trapping efficiencies of four types of pressure-difference bedload samplers
Bedload and ancillary data were collected to calculate and compare the bedload trapping efficiencies of four types of pressure-difference bedload samplers as part of episodic, sediment-recirculating flume experiments at the St. Anthony Falls Laboratory, University of Minnesota, Minneapolis, in January–March 2006. The bedload-sampler experiments, which were conceived, organized, and led by the U.S.
Authors
John R. Gray, Gregory E. Schwarz, David Dean, Jonathan A. Czuba, Joel T. Groten
Accounting for temporal variability of streamflow in estimates of travel time
Retention, processing, and transport of solutes and particulates in stream corridors are influenced by the travel time of streamflow through stream channels, which varies dynamically with discharge. The effects of streamflow variability across sites and over time cannot be addressed by time-averaged models if parameters are based solely on the characteristics of mean streamflow. We develop methods
Authors
Christopher P. Konrad, Noah Schmadel, Judson Harvey, Gregory E. Schwarz, Jesus Gomez-Velez, Elizabeth W. Boyer, Durelle Scott
Low threshold for nitrogen concentration saturation in headwaters increases regional and coastal delivery
River corridors store, convey, and process nutrients from terrestrial and upstream sources, regulating delivery from headwaters to estuaries. A consequence of chronic excess nitrogen loading, as supported by theory and field studies in specific areas, is saturation of the biogeochemically-mediated nitrogen removal processes that weakens the capacity of the river corridor to remove nitrogen. Region
Authors
Noah Schmadel, Judson Harvey, Richard Alexander, Elizabeth W. Boyer, Gregory E. Schwarz, Jesus D. Gomez-Velez, Durelle Scott, Christopher Konrad
An enhanced hydrologic stream network based on the NHDPlus medium resolution dataset
The National Hydrography Dataset Plus, Version 2.1 (NHDPlusV2.1) is an attribute-rich digital stream network for the conterminous United States, serving as a foundational infrastructure for reporting hydrologic information at both regional and national scales. SPAtially Referenced Regressions On Watershed attributes (SPARROW) is a process-based statistical model that relies on a digital hydrologic
Authors
John W. Brakebill, Gregory E. Schwarz, Michael E. Wieczorek
Advances in quantifying streamflow variability across continental scales: 2. Improved model regionalization and prediction uncertainties using hierarchical Bayesian methods
The precise estimation of process effects in hydrological models requires applying models to large scales with extensive spatial variability in controlling factors. Despite progress in large‐scale applications of hydrological models in conterminous United States (CONUS) river basins, spatial constraints in model parameters have prevented the interbasin sharing of data, complicating quantification
Authors
Richard B. Alexander, Gregory E. Schwarz, Elizabeth W. Boyer
Phosphorus and nitrogen transport in the binational Great Lakes Basin estimated using SPARROW watershed models
Eutrophication problems in the Great Lakes are caused by excessive nutrient inputs (primarily phosphorus, P, and nitrogen, N) from various sources throughout its basin. In developing protection and restoration plans, it is important to know where and from what sources the nutrients originate. As part of a binational effort, Midcontinent SPARROW (SPAtially Referenced Regression On Watershed attribu
Authors
Dale M. Robertson, David A. Saad, Glenn A. Benoy, Ivana Vouk, Gregory E. Schwarz, Michael T Laitta
Small ponds in headwater catchments are a dominant influence on regional nutrient and sediment budgets
Small ponds—farm ponds, detention ponds, or impoundments below 0.01 km2—serve important human needs throughout most large river basins. Yet the role of small ponds in regional nutrient and sediment budgets is essentially unknown, currently making it impossible to evaluate their management potential to achieve water quality objectives. Here we used new hydrography data sets and found that small pon
Authors
Noah Schmadel, Judson Harvey, Gregory E. Schwarz, Richard Alexander, Jesus D. Gomez-Velez, Durelle Scott, Scott W. Ator
Estimates of long-term mean daily streamflow and annual nutrient and suspended-sediment loads considered for use in regional SPARROW models of the Conterminous United States, 2012 base year
Streamflow, nutrient, and sediment concentration data needed to estimate long-term mean daily streamflow and annual constituent loads were compiled from Federal, State, Tribal, and regional agencies, universities, and nongovernmental organizations. The streamflow and loads are used to develop Spatially Referenced Regressions on Watershed Attributes (SPARROW) models. SPARROW models help describe th
Authors
David A. Saad, Gregory E. Schwarz, Denise M. Argue, David W. Anning, Scott A. Ator, Anne B. Hoos, Stephen D. Preston, Dale M. Robertson, Daniel Wise
Science and Products
- Science
River Corridor hot spots for biogeochemical processing: a continental scale synthesis
Rivers are the veins of the landscape, providing environmental benefits that are disproportionately high relative to their aerial extent; shedding flood waters, hosting aquatic ecosystems, transporting solutes and energy-rich materials, and storing and transforming pollutants into less harmful forms. From uplands to the coasts, rivers facilitate key biogeochemical reactions that cumulatively influ - Data
Mean seasonal SPARROW model inputs and simulated nitrogen and phosphorus loads for the Northeastern United States 2002 base year
This U.S. Geological Survey (USGS) data release includes input and output tabular files associated with mean seasonal 2002 simulations of total nitrogen and total phosphorus loads of the northeastern United States. The mean seasonal (MS) simulations are performed using a dynamic configuration of the USGS's Spatially Referenced Regression On Watershed attributes (dynamicSPARROW-MS) model, nonlinearNutrient Load Data used to Quantify Regional Effects of Agricultural Best Management Practices: An application of the 2012 SPARROW models for the Midwest, Northeast, and Southeast United States
Nitrogen and phosphorus losses from agricultural areas have impacted the water quality of downstream rivers, lakes, and oceans. As a result, investment in the adoption of agricultural best management practices (BMPs) has grown but assessments of their effectiveness at large spatial scales have been sparse. This study applies regional Spatially Referenced Regression On Watershed-attributes (SPARROWSelect Attributes for NHDPlus Version 2.1 Reach Catchments and Modified Network Routed Upstream Watersheds for the Conterminous United States (ver. 4.0, August 2023)
This metadata record describes a series of data sets of natural and anthropogenic landscape features linked to NHDPlus Version 2.1's (NHDPlusV2) approximately 2.7 million stream segments, their associated catchments, and their upstream watersheds within the conterminous United States. These data were developed by the Hydrologic Sytem's Team (HST) within the the United States Geological Survey's (Inputs and Selected Predictions of the CBTN_v5 and CBTP_v5 SPARROW Models for the Chesapeake Bay Watershed
The CBTN_v5 and CBTP_v5 SPARROW models were developed to support inferences about causes of observed changes in nitrogen and phosphorus (respectively) fluxes in Chesapeake Bay tributaries between 1992 and 2012. Model inputs and outputs are included in three files, which are described below. Detailed documentation of the SPARROW modeling technique is available at https://pubs.er.usgs.gov/publicatio - Publications
Filter Total Items: 66
Sand- and gravel-trapping efficiencies derived for four types of pressure-difference bedload samplers
Bedload-trapping efficiencies (coefficients) were derived for four types of pressure-difference bedload samplers at the St. Anthony Falls Laboratory, University of Minnesota during the first two phases of flume experiments in January-March, 2006, referred to as “StreamLab06.” The bedload-sampler research component was part of a series of community-led, large-scale laboratory experiments performedAuthorsJohn Gray, Joel T. Groten, Jonathan A. Czuba, Gregory E. Schwarz, Kyle Strom, Panayiotis DiplasPredicting near-term effects of climate change on nitrogen transport to Chesapeake Bay
Understanding effects of climate change on nitrogen fate and transport in the environment is critical to nutrient management. We used climate projections within a previously calibrated spatially referenced regression (SPARROW) model to predict effects of expected climate change over 1995 through 2025 on total nitrogen fluxes to Chesapeake Bay and in watershed streams. Assuming nitrogen inputs andAuthorsScott Ator, Gregory E. Schwarz, Andrew Sekellick, Gopal BhattQuantifying regional effects of best management practices on nutrient losses from agricultural lands
Nitrogen (N) and phosphorus (P) losses from agricultural areas have degraded the water quality of downstream rivers, lakes, and oceans. As a result, investment in the adoption of agricultural best management practices (BMPs) has grown, but assessments of their effectiveness at large spatial scales have lagged. This study applies regional Spatially Referenced Regression On Watershed-attributes (SPAAuthorsVictor L. Roland, Ana María García, David A. Saad, Scott W. Ator, Dale M. Robertson, Gregory E. SchwarzSeasonally dynamic nutrient modeling quantifies storage lags and time-varying reactivity across large river basins
Nutrients that have gradually accumulated in soils, groundwaters, and river sediments in the United States over the past century can remobilize and increase current downstream loading, obscuring effects of conservation practices aimed at protecting water resources. Drivers of storage accumulation and release of nutrients are poorly understood at the spatial scale of basins to watersheds. PredictinAuthorsNoah Schmadel, Judson Harvey, Gregory E. SchwarzInstruments, methods, rationale, and derived data used to quantify and compare the trapping efficiencies of four types of pressure-difference bedload samplers
Bedload and ancillary data were collected to calculate and compare the bedload trapping efficiencies of four types of pressure-difference bedload samplers as part of episodic, sediment-recirculating flume experiments at the St. Anthony Falls Laboratory, University of Minnesota, Minneapolis, in January–March 2006. The bedload-sampler experiments, which were conceived, organized, and led by the U.S.AuthorsJohn R. Gray, Gregory E. Schwarz, David Dean, Jonathan A. Czuba, Joel T. GrotenAccounting for temporal variability of streamflow in estimates of travel time
Retention, processing, and transport of solutes and particulates in stream corridors are influenced by the travel time of streamflow through stream channels, which varies dynamically with discharge. The effects of streamflow variability across sites and over time cannot be addressed by time-averaged models if parameters are based solely on the characteristics of mean streamflow. We develop methodsAuthorsChristopher P. Konrad, Noah Schmadel, Judson Harvey, Gregory E. Schwarz, Jesus Gomez-Velez, Elizabeth W. Boyer, Durelle ScottLow threshold for nitrogen concentration saturation in headwaters increases regional and coastal delivery
River corridors store, convey, and process nutrients from terrestrial and upstream sources, regulating delivery from headwaters to estuaries. A consequence of chronic excess nitrogen loading, as supported by theory and field studies in specific areas, is saturation of the biogeochemically-mediated nitrogen removal processes that weakens the capacity of the river corridor to remove nitrogen. RegionAuthorsNoah Schmadel, Judson Harvey, Richard Alexander, Elizabeth W. Boyer, Gregory E. Schwarz, Jesus D. Gomez-Velez, Durelle Scott, Christopher KonradAn enhanced hydrologic stream network based on the NHDPlus medium resolution dataset
The National Hydrography Dataset Plus, Version 2.1 (NHDPlusV2.1) is an attribute-rich digital stream network for the conterminous United States, serving as a foundational infrastructure for reporting hydrologic information at both regional and national scales. SPAtially Referenced Regressions On Watershed attributes (SPARROW) is a process-based statistical model that relies on a digital hydrologicAuthorsJohn W. Brakebill, Gregory E. Schwarz, Michael E. WieczorekAdvances in quantifying streamflow variability across continental scales: 2. Improved model regionalization and prediction uncertainties using hierarchical Bayesian methods
The precise estimation of process effects in hydrological models requires applying models to large scales with extensive spatial variability in controlling factors. Despite progress in large‐scale applications of hydrological models in conterminous United States (CONUS) river basins, spatial constraints in model parameters have prevented the interbasin sharing of data, complicating quantificationAuthorsRichard B. Alexander, Gregory E. Schwarz, Elizabeth W. BoyerPhosphorus and nitrogen transport in the binational Great Lakes Basin estimated using SPARROW watershed models
Eutrophication problems in the Great Lakes are caused by excessive nutrient inputs (primarily phosphorus, P, and nitrogen, N) from various sources throughout its basin. In developing protection and restoration plans, it is important to know where and from what sources the nutrients originate. As part of a binational effort, Midcontinent SPARROW (SPAtially Referenced Regression On Watershed attribuAuthorsDale M. Robertson, David A. Saad, Glenn A. Benoy, Ivana Vouk, Gregory E. Schwarz, Michael T LaittaSmall ponds in headwater catchments are a dominant influence on regional nutrient and sediment budgets
Small ponds—farm ponds, detention ponds, or impoundments below 0.01 km2—serve important human needs throughout most large river basins. Yet the role of small ponds in regional nutrient and sediment budgets is essentially unknown, currently making it impossible to evaluate their management potential to achieve water quality objectives. Here we used new hydrography data sets and found that small ponAuthorsNoah Schmadel, Judson Harvey, Gregory E. Schwarz, Richard Alexander, Jesus D. Gomez-Velez, Durelle Scott, Scott W. AtorEstimates of long-term mean daily streamflow and annual nutrient and suspended-sediment loads considered for use in regional SPARROW models of the Conterminous United States, 2012 base year
Streamflow, nutrient, and sediment concentration data needed to estimate long-term mean daily streamflow and annual constituent loads were compiled from Federal, State, Tribal, and regional agencies, universities, and nongovernmental organizations. The streamflow and loads are used to develop Spatially Referenced Regressions on Watershed Attributes (SPARROW) models. SPARROW models help describe thAuthorsDavid A. Saad, Gregory E. Schwarz, Denise M. Argue, David W. Anning, Scott A. Ator, Anne B. Hoos, Stephen D. Preston, Dale M. Robertson, Daniel Wise