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
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: 65
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
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
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
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.
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
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
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
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
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
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
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
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
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
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: 65
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 andQuantifying 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 (SPASeasonally 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. PredictinInstruments, 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.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 methodsEstimation 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 nonpointLow 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. RegionAn 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 hydrologicAdvances 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 quantificationPhosphorus 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 attribuSmall 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 ponEstimates 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