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Scott Ator

Scott Ator is a Hydrologist at the USGS MD-DE-DC Water Science Center.

I have been a hydrologist with the U.S. Geological Survey in Baltimore, Maryland since 1994, including a Research Hydrologist from 2005 through 2010. My work has focused primarily on the design, implementation, and analysis and interpretation of results of water-quality and geochemical studies (including major-ion chemistry, nutrients, and pesticides) in streams and groundwater at multiple spatial

Professional Experience

  • Hydrologist at USGS MD-DE-DC Water Science Center, Catonsville, MD, 1994 to present day

     

  • Research Hydrologist at USGS MD-DE-DC Water Science Center, Catonsville, MD, 2005-2010

Education and Certifications

  • MS, Environmental Science and Policy, Johns Hopkins University, Baltimore, MD, 2003

  • BS, Geology, summa cum laude, University of Maryland, College Park, MD, 1994

Science and Products

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Screenshot of web map and map controls; shaded areas show total phosphorus levels in Northeast US streams

2012 SPARROW Models for the Northeast: Total Phosphorus, Total Nitrogen, Suspended Sediment, and Streamflow

The 2012 SPAtially Referenced Regression On Watershed attributes (SPARROW) Models measure the damaging contaminants of phosphorus, nitrogen, and suspended sediment in streamflow throughout the Northeast United States. Through various types of watershed management practices, loads of nutrients and suspended sediment are significantly reduced within the stream network in impounded reaches, and...
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Maryland-Delaware-D.C. Water Science Center
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2012 SPARROW Models for the Northeast: Total Phosphorus, Total Nitrogen, Suspended Sediment, and Streamflow

The 2012 SPAtially Referenced Regression On Watershed attributes (SPARROW) Models measure the damaging contaminants of phosphorus, nitrogen, and suspended sediment in streamflow throughout the Northeast United States. Through various types of watershed management practices, loads of nutrients and suspended sediment are significantly reduced within the stream network in impounded reaches, and...
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U.S. Geological Survey hydrologic technicians collect a stream sample from Hallocks Mill Brook

New Synthesis Describes Current Understanding of Factors Driving Nutrient Trends in Streams of the Chesapeake Bay Watershed

Issue: Excessive nitrogen and phosphorus in Chesapeake Bay since the 1950s have contributed to low dissolved oxygen leading to fish kills, and poor water clarity and associated loss of submerged aquatic vegetation. The Chesapeake Bay Program partnership has been working to improve aquatic conditions in the Bay and its tidal tributaries, and streams in the watershed, by reducing inputs of nutrients...
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Core Science Systems Mission Area, Chesapeake Bay Activities
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New Synthesis Describes Current Understanding of Factors Driving Nutrient Trends in Streams of the Chesapeake Bay Watershed

Issue: Excessive nitrogen and phosphorus in Chesapeake Bay since the 1950s have contributed to low dissolved oxygen leading to fish kills, and poor water clarity and associated loss of submerged aquatic vegetation. The Chesapeake Bay Program partnership has been working to improve aquatic conditions in the Bay and its tidal tributaries, and streams in the watershed, by reducing inputs of nutrients...
Learn More
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Example layer-bottom altitudes from MODFLOW-NWT.

Modeling Capabilities @ MD-DE-DC

USGS models are widely used to predict responses of hydrologic systems to changing stresses, such as increases in precipitation or ground-water pumping rates, as well as to predict the fate and movement of solutes and contaminants in water. The USGS is at the forefront of devising new techniques and computer software to solve practical problems in the study of water resources. Predictive models...
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Maryland-Delaware-D.C. Water Science Center
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Modeling Capabilities @ MD-DE-DC

USGS models are widely used to predict responses of hydrologic systems to changing stresses, such as increases in precipitation or ground-water pumping rates, as well as to predict the fate and movement of solutes and contaminants in water. The USGS is at the forefront of devising new techniques and computer software to solve practical problems in the study of water resources. Predictive models...
Learn More
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Water chemistry measurements on the Alaska Peninsula

Improving Our Understanding and Helping with Water Quality Improvements

Understanding trends in stream chemistry is critical to watershed management and often complicated by multiple contaminant sources and landscape conditions changing over varying time scales.
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Chesapeake Bay Activities
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Improving Our Understanding and Helping with Water Quality Improvements

Understanding trends in stream chemistry is critical to watershed management and often complicated by multiple contaminant sources and landscape conditions changing over varying time scales.
Learn More
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Nitrogen and Phosphorus Applied to the Eastern Shore

Excess manure and fertilizer are worsening water-quality conditions on Eastern Shore of Chesapeake

Excess fertilizer and manure applied to the Chesapeake Bay’s Eastern Shore are causing poor water-quality in streams that flow into the Bay, according to a new publication by the U.S. Geological Survey.
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Chesapeake Bay Activities
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Excess manure and fertilizer are worsening water-quality conditions on Eastern Shore of Chesapeake

Excess fertilizer and manure applied to the Chesapeake Bay’s Eastern Shore are causing poor water-quality in streams that flow into the Bay, according to a new publication by the U.S. Geological Survey.
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SPARROW model input datasets and predictions for predicting near-term effects of climate change on nitrogen transport to Chesapeake Bay

This data release includes 5 files containing model inputs and resulting model predictions. A previously-calibrated spatially referenced regression (SPARROW) model was used to estimate effects of climate change on in-stream nitrogen (TN) loads in the Chesapeake Bay watershed between 1995 and 2025. Model scenarios were run using data for nitrogen sources and landscape characteristics from 2012, cha
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Maryland-Delaware-D.C. Water Science Center

SPARROW model input datasets and predictions of nitrogen loads in streams of the Chesapeake Bay watershed

This data release contains mean-annual total nitrogen (TN) loads predicted by a SPARROW model for individual stream and shoreline reaches in the Chesapeake watershed as defined by NHDPlus, a 1:100,000 scale representation of stream hydrography built upon the National Hydrography Dataset (NHD) (Horizon Systems, 2010). Also included are the input variables required to execute the model, including la
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Chesapeake Bay Activities, Maryland-Delaware-D.C. Water Science Center

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
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Lower Mississippi-Gulf Water Science Center

SPARROW model inputs and simulated streamflow, nutrient and suspended-sediment loads in streams of the Northeastern United States, 2012 Base Year

The U.S. Geological Survey's (USGS) SPAtially Referenced Regression On Watershed attributes (SPARROW) model was used to aid in the interpretation of monitoring data and simulate streamflow and water-quality conditions in streams across the Northeast Region of the United States. SPARROW is a hybrid empirical/process-based mass balance model that can be used to estimate the major sources and environ
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Chesapeake Bay Activities, Maryland-Delaware-D.C. Water Science Center

Water-quality and streamflow datasets used for estimating long-term mean daily streamflow and annual loads to be considered for use in regional streamflow, nutrient and sediment SPARROW models, United States, 1999-2014

The United States Geological Survey's (USGS) SPAtially Referenced Regressions On Watershed attributes (SPARROW) model was developed to aid in the interpretation of monitoring data and simulate water-quality conditions in streams across large spatial scales. SPARROW is a hybrid empirical/process-based mass balance model that can be used to estimate the major sources and environmental factors that a
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Water Resources Mission Area

Input and predictions from a suspended-sediment SPARROW model CBSS_V2 in the Chesapeake Bay watershed

These data represent input and estimates from a medium-resolution (1:100,000 scale) NHDPlus SPAtially Referenced Regression on Watershed attributes (SPARROW) model for the Chesapeake Bay watershed (CBSS_v2). The model spatially correlates long-term mean annual suspended-sediment flux in 113 non-tidal streams to likely upland and stream-corridor sources, landscape factors affecting upland sediment
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Chesapeake Bay Activities, Maryland-Delaware-D.C. Water Science Center

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
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Water Resources Mission Area, National Water Quality Program, Chesapeake Bay Activities
Filter Total Items: 44

Geology, hydrology, and groundwater contamination in the vicinity of Central Chemical facility, Hagerstown, Maryland

The soil and groundwater at the Central Chemical facility, Hagerstown, Maryland, are contaminated due to the blending and production of pesticides and fertilizers during much of the 20th century. Remedial investigations focus on two operable units (OU) consisting of the surface soils and waste disposal lagoon (OU-1) and the groundwater (OU-2). The contaminants of concern (COC) for groundwater incl
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Trevor P. Needham, Alex R. Fiore, Scott W. Ator, Jeff P. Raffensperger, Madison B. Smith, Nicole M. Bellmyer, Caitlyn M. Dugan, Carol J. Morel

Estimated reduction of nitrogen in streams of the Chesapeake Bay in areas with agricultural conservation practices

Spatial data provided by the U.S. Department of Agriculture National Resource Conservation Service representing implementation at the field-level for a selection of agricultural conservation practices were incorporated within a spatially referenced regression model to estimate their effects on nitrogen loads in streams in the Chesapeake Bay watershed. Conservation practices classified as “high-imp
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Andrew Sekellick, Scott Ator, Olivia H. Devereux, Jennifer L. Keisman
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Chesapeake Bay Activities, Maryland-Delaware-D.C. Water Science Center, Pennsylvania Water Science Center

Effects of return flows on stream water quality and availability in the Upper Colorado, Delaware, and Illinois River Basins

Understanding effects of human water use and subsequent return flows on the availability and suitability of water for downstream uses is critical to efficient and effective watershed management. We compared spatially detailed estimates of stream chemistry within three watersheds in diverse settings to available standards to isolate effects of wastewater and irrigation return flows on the suitabili
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Scott Ator, Olivia L. Miller, David A. Saad
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Water Resources Mission Area, Pennsylvania Water Science Center

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
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Scott Ator, Gregory E. Schwarz, Andrew Sekellick, Gopal Bhatt
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Chesapeake Bay Activities

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
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Victor L. Roland, Ana María García, David A. Saad, Scott W. Ator, Dale M. Robertson, Gregory E. Schwarz
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Water Resources Mission Area, Upper Midwest Environmental Sciences Center, Upper Midwest Water Science Center, South Atlantic Water Science Center (SAWSC), Lower Mississippi-Gulf Water Science Center

Nutrient trends and drivers in the Chesapeake Bay Watershed

The Chesapeake Bay Program maintains an extensive nontidal monitoring network, measuring nitrogen and phosphorus (nutrients) at more than 100 locations on rivers and streams in the watershed. Data from these locations are used by United States Geological Survey to assess the ecosystem’s response to nutrient-reduction efforts. This fact sheet summarizes recent trends in nitrogen and phosphorus in n
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Kenneth E. Hyer, Scott W. Phillips, Scott W. Ator, Doug L. Moyer, James S. Webber, Rachel Felver, Jennifer L. Keisman, Lee A. McDonnell, Rebecca Murphy, Emily M. Trentacoste, Qian Zhang, William C. Dennison, Sky Swanson, Brianne Walsh, Jane Hawkey, Dylan Taillie
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Chesapeake Bay Activities, Pennsylvania Water Science Center, Virginia and West Virginia Water Science Center

Factors driving nutrient trends in streams of the Chesapeake Bay watershed

Despite decades of effort toward reducing nitrogen and phosphorus flux to Chesapeake Bay, water-quality and ecological responses in surface waters have been mixed. Recent research, however, provides useful insight into multiple factors complicating the understanding of nutrient trends in bay tributaries, which we review in this paper, as we approach a 2025 total maximum daily load (TMDL) managemen
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Scott Ator, Joel Blomquist, James S. Webber, Jeffrey G. Chanat
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Chesapeake Bay Activities, Virginia and West Virginia Water Science Center

Hydrogeology and shallow groundwater quality in the tidal Anacostia River watershed, Washington, D.C.

Groundwater hydrology and geochemistry within the tidal Anacostia River watershed of Washington, D.C. are related to natural and human influences. The U.S. Geological Survey, in cooperation with the District Department of Energy & Environment, began investigating the hydrogeology and groundwater quality of the watershed in 2002. Lithologic coring, groundwater-level and tidal monitoring, and water-
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Scott W. Ator, Judith M. Denver, Cheryl A. Dieter
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Water Resources Mission Area, Maryland-Delaware-D.C. Water Science Center

Response of nitrogen loading to the Chesapeake Bay to source reduction and land use change scenarios: A SPARROW‐informed analysis

In response to concerns regarding the health of streams and receiving waters, the United States Environmental Protection Agency established a total maximum daily load for nitrogen in the Chesapeake Bay watershed for which practices must be in place by 2025 resulting in an expected 25% reduction in load from 2009 levels. The response of total nitrogen (TN) loads delivered to the Bay to nine source
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Matthew P. Miller, Paul D. Capel, Ana M. Garcia, Scott W. Ator
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Water Resources Mission Area, Chesapeake Bay Activities, Maryland-Delaware-D.C. Water Science Center, Pennsylvania Water Science Center

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
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Noah Schmadel, Judson Harvey, Gregory E. Schwarz, Richard Alexander, Jesus D. Gomez-Velez, Durelle Scott, Scott W. Ator
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Water Resources Mission Area, John Wesley Powell Center for Analysis and Synthesis, Maryland-Delaware-D.C. Water Science Center

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
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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
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Water Resources Mission Area, Upper Midwest Environmental Sciences Center, Upper Midwest Water Science Center

Toward explaining nitrogen and phosphorus trends in Chesapeake Bay tributaries, 1992-2012

Understanding trends in stream chemistry is critical to watershed management, and often complicated by multiple contaminant sources and landscape conditions changing over varying time scales. We adapted spatially-referenced regression (SPARROW) to infer causes of recent nutrient trends in Chesapeake Bay tributaries by relating observed fluxes during 1992, 2002, and 2012 to contemporary inputs and
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Scott Ator, Ana M. Garcia, Gregory E. Schwarz, Joel Blomquist, Andrew Sekellick
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Water Resources Mission Area, Chesapeake Bay Activities, Maryland-Delaware-D.C. Water Science Center, Pennsylvania Water Science Center
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MD-DE-DC WSC Capabilities Sites

We’ve created a series of websites, thematically named to characterize our work as our “Capabilities”, working interdependently with a diverse array...

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