Alexander Soroka
Alex is fascinated in how little decisions we make in our day-to-day lives can add up to big changes in our water supply and its quality. His research broadly focuses on interactions between land use and water quality in Maryland and Delaware. Currently Alex is summarizing groundwater quality changes from 1980-present and agronomic practices in the Chesapeake Bay watershed
Alex Soroka is a physical scientist at the USGS Maryland-Delaware-DC Water Science Center in Baltimore, Maryland, where his work primarily focuses on the interactions between agricultural practices and water quality. He earned a Bachelor of Science in Environmental Science at the State University of New York at Oneonta in 2012 and a Master’s degree in Water Science and Policy at the University of Delaware in 2015. His thesis work investigated fertilization rates and nutrient uptake for high yielding irrigated grain corn and involved a combination of agronomy and hydrology.
Alex found a home in soil fertility research as a Master’s student advised by Dr. Amy Shober. He contributed to multiple projects involving phosphorous (P) amendments, P transport, cover crop implementation, nutrient uptake by row crops, and irrigation management. In working with extension specialists, Alex learned firsthand of the difficulty that producers face trying to maintain profitability while meeting water quality goals.
Alex began an internship with the USGS in 2014 after his presentation at a field day for local producers caught the eye of USGS scientist Judy Denver. Working out of the Dover, Delaware office, Alex studied the impact of irrigation on nitrogen movement under two corn and soybean fields. In March of 2018, Alex transitioned to a permanent position in the USGS Baltimore office, where he continues to focus on agricultural research. He is also leading a project to develop innovative methods of estimating nitrogen flux into wetlands from grain fields and is coordinating a group of students digitizing agricultural features on the Delmarva peninsula. Alex is also working on linking remote sensing data, such as NDVI, with water quality.
Professional Experience
2018-Present Physical Scientist, USGS MD-DE-DC Water Science Center, MD
2016-2017 Pathways Physical Scientist Intern, USGS Dover office, DE
2013-2016 Teaching and Research assistant, University of Delaware, DE
2011-2012 Teaching assistant, SUNY Oneonta, NY
2010 Research Experience for Undergrad (REU) intern, Hubbard Brook, NH
Education and Certifications
MS - Water Science and Policy, University of Delaware - 2016
Thesis: Effects of In-Season Fertilizer Strategies on the Yield and Nitrogen Use Efficiency of Irrigated Corn
BS - Environmental Science, State University of New York at Oneota - 2012
Science and Products
Summarizing Science to Inform Management in the Chesapeake Bay Watershed
Science to Inform Management Priorities from Loads to Endpoints (SIMPLE)
USGS calculates loads and trends through 2021 for the nine major rivers entering Chesapeake Bay
Summarizing Scientific Findings for Common Stakeholder Questions to Inform Nutrient and Sediment Management Activities in the Chesapeake Bay Watershed
Updated 2020 Nutrient and Suspended-Sediment Trends for the Nine Major Rivers Entering the Chesapeake Bay
Nitrogen, phosphorus, and suspended-sediment loads and trends measured at the Chesapeake Bay River Input Monitoring stations: Water years 1985-2022
Data supporting a spatiotemporal trend analysis of specific conductivity, streamflow, and landscape attributes of selected sub-basins within the Delaware River watershed, 1980 to 2018
Soil-Water-Balance (SWB) model archive used to simulate water budget components in Pennsylvania and Maryland, 2000-2020
Possible Cattle Access Points on Select Streams within the Smith Creek Watershed Derived from 2018 NAIP Imagery
Nitrogen, phosphorus, and suspended-sediment loads and trends measured at the Chesapeake Bay River Input Monitoring stations: Water years 1985-2021
Possible Cattle Access Points on Steams within the USGS Showcase Watersheds Derived from 2018 and 2019 NAIP Imagery
Nitrogen, phosphorus, and suspended-sediment loads and trends measured at the Chesapeake Bay River Input Monitoring stations: Water years 1985-2020
Nitrogen flux estimates in support of Chesapeake Bay Hypoxia and Anoxia forecasts, 1985-2021
Water bodies within 500 meters of poultry feeding operations on the Delmarva Peninsula in 2016 and 2017
Nitrogen flux estimates in support of Chesapeake Bay Hypoxia and Anoxia forecasts, 1985-2020
Poultry Feeding Operations on the Delaware, Maryland, and Virginia Peninsula from 2016 to 2017
Poultry production houses in the Upper Choptank watershed identified using aerial imagery from 1968 to 2018
Atmospheric correction intercomparison of hyperspectral and multispectral imagery over agricultural study sites
Your land, your water—Using research to guide conservation practices on local farms in the Chesapeake Bay watershed
Hydrogeologic characterization of Area B, Fort Detrick, Maryland
Near real-time detection of winter cover crop termination using harmonized Landsat and Sentinel-2 (HLS) to support ecosystem assessment
Spatial patterns and seasonal timing of increasing riverine specific conductance from 1998 to 2018 suggest legacy contamination in the Delaware River Basin
Remote sensing evaluation of winter cover crop springtime performance and the impact of delayed termination
Nitrogen in the Chesapeake Bay watershed—A century of change, 1950–2050
Estimating the effect of winter cover crops on nitrogen leaching using cost-share enrollment data, satellite remote sensing, and Soil and Water Assessment Tool (SWAT) modeling
Monitoring the water-quality response of agricultural conservation practices in the Bucks Branch watershed, Sussex County, Delaware, 2014–16
Science and Products
- Science
Summarizing Science to Inform Management in the Chesapeake Bay Watershed
Stakeholders can use scientific insights to address their priority water-quality concerns. The USGS works with Chesapeake Bay stakeholders to identify and address priority questions that can help inform management decisions. These scientific insights can help guide nutrient and sediment management activities undertaken by Chesapeake Bay stakeholders. This webpage summarizes recent scientific...Science to Inform Management Priorities from Loads to Endpoints (SIMPLE)
Resource managers are working to improve water-quality in the Chesapeake to benefit the people who live in the region and the birds, fish, and other animals who rely on clean water in the watershed and the Bay. The U.S Geological Survey (USGS) supports resource managers and other Chesapeake stakeholders by providing science that informs restoration and conservation in the Chesapeake region. The...USGS calculates loads and trends through 2021 for the nine major rivers entering Chesapeake Bay
Issue: The amount of nutrients and suspended sediment entering the Chesapeake Bay affect water-quality conditions in tidal waters. Excess nutrients contribute to algal blooms that lower the oxygen levels in tidal waters that are important for fish and shellfish. The algal blooms, along with suspended sediment, also decrease visibility in shallow waters for submerged aquatic grasses. The grasses...Summarizing Scientific Findings for Common Stakeholder Questions to Inform Nutrient and Sediment Management Activities in the Chesapeake Bay Watershed
Issue: The Chesapeake Bay Program (CBP) partnership is striving to improve water-quality conditions in the Bay by using a variety of management strategies to reduce nutrient and sediment loads. The partnership uses monitoring results and modeling tools to implement management strategies, relying on the scientific community to synthesize existing information and direct new research to address...Updated 2020 Nutrient and Suspended-Sediment Trends for the Nine Major Rivers Entering the Chesapeake Bay
Issue: The amount of nutrients and suspended sediment entering the Chesapeake Bay affect water-quality conditions in tidal waters. Excess nutrients contribute to algal blooms that lower the oxygen levels in tidal waters that are important for fish and shellfish. The algal blooms, along with suspended sediment, also decrease visibility in shallow waters for submerged aquatic grasses. The grasses... - Data
Filter Total Items: 13
Nitrogen, phosphorus, and suspended-sediment loads and trends measured at the Chesapeake Bay River Input Monitoring stations: Water years 1985-2022
Nitrogen, phosphorus, and suspended-sediment loads, and changes in loads, in major rivers across the Chesapeake Bay watershed have been calculated using monitoring data from the Chesapeake Bay River Input Monitoring (RIM) Network stations for the period 1985 through 2022. Nutrient and suspended-sediment loads and changes in loads were determined by applying a weighted regression approach called WRData supporting a spatiotemporal trend analysis of specific conductivity, streamflow, and landscape attributes of selected sub-basins within the Delaware River watershed, 1980 to 2018
This data release makes available three data tables supporting a spatiotemporal analysis of riverine conductivity and streamflow trends within the Delaware River Basin. The listed datasets include baseflow and total flow time series for selected gaged basins, watershed attributes, water quality information and trend analysis results.Soil-Water-Balance (SWB) model archive used to simulate water budget components in Pennsylvania and Maryland, 2000-2020
This model archive documents the Soil-Water-Balance (SWB) model used to simulate potential recharge for portions of Pennsylvania and Maryland from 2000 to 2021. The Pennsylvania and Maryland SWB model was used to create output at a 250 meter grid scale. Model parameters were adjusted using baseflow estimates from 36 reference watersheds varying in area from 0.37 to 817 square miles. The simulationPossible Cattle Access Points on Select Streams within the Smith Creek Watershed Derived from 2018 NAIP Imagery
This data release contains one shapefile describing cattle access to a total of 36 different sub basins within the Smith Creek Watershed located in Virginia and West Virginia. This data release identifies areas in satellite imagery where cattle were observed to have access to the stream (confirmed access), areas where cattle exist, and are not fenced off from the stream (unrestricted access), andNitrogen, phosphorus, and suspended-sediment loads and trends measured at the Chesapeake Bay River Input Monitoring stations: Water years 1985-2021
Nitrogen, phosphorus, and suspended-sediment loads, and changes in loads, in major rivers across the Chesapeake Bay watershed have been calculated using monitoring data from the Chesapeake Bay River Input Monitoring (RIM) Network stations for the period 1985 through 2021. Nutrient and suspended-sediment loads and changes in loads were determined by applying a weighted regression approach called WRPossible Cattle Access Points on Steams within the USGS Showcase Watersheds Derived from 2018 and 2019 NAIP Imagery
This data release contains one point shapefile describing cattle access to streams for three USGS showcase watersheds: Smith Creek, Conewago Creek, and Upper Chester River. This data release identifies areas where cattle were able to access the stream, as well as possible cattle access areas. Streams were defined using a combination of geospatial data and aerial imagery and cattle access points weNitrogen, phosphorus, and suspended-sediment loads and trends measured at the Chesapeake Bay River Input Monitoring stations: Water years 1985-2020
Nitrogen, phosphorus, and suspended-sediment loads, and changes in loads, in major rivers across the Chesapeake Bay watershed have been calculated using monitoring data from the Chesapeake Bay River Input Monitoring (RIM) Network stations for the period 1985 through 2020. Nutrient and suspended-sediment loads and changes in loads were determined by applying a weighted regression approach called WRNitrogen flux estimates in support of Chesapeake Bay Hypoxia and Anoxia forecasts, 1985-2021
Data release includes the U.S. Geological Survey (USGS) estimate of spring nitrogen fluxes summed from nine tributaries to the Chesapeake Bay from 1985 to 2021. Data are presented as the sum from tributaries within the USGS River Input Monitoring (RIM) network identified by site numbers: 01491000, 01578310, 01594440, 01646580, 01668000, 01673000, 01674500, 02035000, 02041650. Periods of estimationWater bodies within 500 meters of poultry feeding operations on the Delmarva Peninsula in 2016 and 2017
Data release contains 1710 polygons representing small bodies of water within 500 meters of poultry feeding operations on the Delmarva Peninsula. Ponds were identified using the USDA's National Agriculture Imagery Program's 2016 and 2017 products. Poultry feeding operations were described in location by Soroka and Duren (2020).Nitrogen flux estimates in support of Chesapeake Bay Hypoxia and Anoxia forecasts, 1985-2020
Data release includes the U.S. Geological Survey (USGS) estimate of spring nitrogen fluxes from nine tributaries to the Chesapeake Bay from 1985 to 2020. Data are presented from tributaries within the USGS River Input Monitoring (RIM) network identified by site numbers: 01491000, 01578310, 01594440, 01646580, 01668000, 01673000, 01674500, 02035000, 02041650. Periods of estimation include January tPoultry Feeding Operations on the Delaware, Maryland, and Virginia Peninsula from 2016 to 2017
Data release contains two shapefiles related to poultry houses on the Delmarva Peninsula (Delaware, Eastern Shore Maryland and, Eastern Shore Virginia). One dataset is a polygon shapefile representing 5747 poultry houses identified using 2016 and 2017 aerial imagery from the U.S. Department of Agricultures National Aerial Imagery Program (NAIP). The second dataset is a point shapefile of inactivPoultry production houses in the Upper Choptank watershed identified using aerial imagery from 1968 to 2018
Dataset contains a polygon shapefile representing poultry houses in the Upper Choptank watershed in Queen Anne's County, Maryland, and Kent County, Delaware. - Publications
Atmospheric correction intercomparison of hyperspectral and multispectral imagery over agricultural study sites
In this research effort we assess the performance of atmospheric correction-based surface reflectance (SR) retrievals from two satellite image sources, one with very high spatial resolution (VHR) (AuthorsBrian T Lamb, W. Dean Hively, Jyoti Jennewein, Alison Thieme, Alex M. SorokaYour land, your water—Using research to guide conservation practices on local farms in the Chesapeake Bay watershed
Agricultural lands are an important part of the economy and heritage of the Chesapeake Bay watershed and are a focus of conservation activities. Streams and rivers around farms provide communities with drinking water and recreational opportunities, but these local benefits can be impaired by elevated nutrient and sediment concentrations. Compared to inputs from the atmosphere, wastewater, and urbaAuthorsJames S. Webber, John W. Clune, Alex M. Soroka, Kenneth E. HyerHydrogeologic characterization of Area B, Fort Detrick, Maryland
Groundwater in the karst groundwater system at Area B of Fort Detrick in Frederick County, Maryland, is contaminated with chlorinated solvents from the past disposal of laboratory wastes. In cooperation with U.S. Army Environmental Command and U.S. Army Garrison Fort Detrick, the U.S. Geological Survey performed a 3-year study to refine the conceptual model of groundwater flow in and around Area BAuthorsPhillip J. Goodling, Brandon J. Fleming, John Solder, Alex M. Soroka, Jeff P. RaffenspergerNear real-time detection of winter cover crop termination using harmonized Landsat and Sentinel-2 (HLS) to support ecosystem assessment
Cover crops are planted to reduce soil erosion, increase soil fertility, and improve watershed management. In the Delmarva Peninsula of the eastern United States, winter cover crops are essential for reducing nutrient and sediment losses from farmland. Cost-share programs have been created to incentivize cover crops to achieve conservation objectives. This program required that cover crops be planAuthorsFeng Gao, Jyoti Jennewein, W. Dean Hively, Alex M. Soroka, Alison Thieme, Dawn Bradley, Jason Keppler, Steven Mirsky, Uvirkaa AkumagaSpatial patterns and seasonal timing of increasing riverine specific conductance from 1998 to 2018 suggest legacy contamination in the Delaware River Basin
Increasing salinization of freshwater threatens water supplies that support a range of human and ecological uses. The latest assessments of Delaware River Basin (DRB) surface-water-quality changes indicate widespread salinization has occurred in recent decades, which may lead to meaningful degradation in water quality. To better understand how and when salinity transport occurs and implications foAuthorsChristine Rumsey, John C. Hammond, Jennifer C. Murphy, Megan E. Shoda, Alex M. SorokaRemote sensing evaluation of winter cover crop springtime performance and the impact of delayed termination
In 2019, the Maryland Department of Agriculture's Winter Cover Crop Program introduced a delayed termination incentive (after May 1) to promote springtime biomass accumulation. We used satellite imagery calibrated with springtime in situ measurements collected from 2006–2021 (n = 722) to derive biomass estimates for Maryland fields planted to cereal cover crop species (286,200 ha total over two seAuthorsAlison Thieme, W. Dean Hively, Feng Gao, Jyoti Jennewein, Steven Mirsky, Alex M. Soroka, Jason Keppler, Dawn Bradley, Sergii Skakun, Gregory W. McCartyNitrogen in the Chesapeake Bay watershed—A century of change, 1950–2050
ForewordSustaining the quality of the Nation’s water resources and the health of our diverse ecosystems depends on the availability of sound water-resources data and information to develop effective, science-based policies. Effective management of water resources also brings more certainty and efficiency to important economic sectors. Taken together, these actions lead to immediate and long-term eAuthorsJohn W. Clune, Paul D. Capel, Matthew P. Miller, Douglas A. Burns, Andrew J. Sekellick, Peter R. Claggett, Richard H. Coupe, Rosemary M. Fanelli, Ana Maria Garcia, Jeff P. Raffensperger, Silvia Terziotti, Gopal Bhatt, Joel D. Blomquist, Kristina G. Hopkins, Jennifer L. Keisman, Lewis C. Linker, Gary W. Shenk, Richard A. Smith, Alex M. Soroka, James S. Webber, David M. Wolock, Qian ZhangEstimating the effect of winter cover crops on nitrogen leaching using cost-share enrollment data, satellite remote sensing, and Soil and Water Assessment Tool (SWAT) modeling
This study employed a novel combination of data (winter cover crop cost-share enrollment records, satellite remote sensing of wintertime vegetation, and results of Soil and Water Assessment Tool (SWAT) water quality simulations) to estimate the environmental performance of winter cover crops (WCC) at the watershed scale, from 2008 through 2017, within the Tuckahoe sub-watershed of the Choptank RivAuthorsW. Dean Hively, Sangchul Lee, Ali M. Sadeghi, Gregory W. McCarty, Brian T. Lamb, Alex M. Soroka, Jason Keppler, In-Young Yeo, Glenn E. MoglenMonitoring the water-quality response of agricultural conservation practices in the Bucks Branch watershed, Sussex County, Delaware, 2014–16
The purpose of this study was to evaluate the effects of irrigation and cover crops as conservation practices on water quality in groundwater and streams. Bucks Branch, a stream in the Nanticoke River watershed in southwestern Delaware, was identified as having one of the highest concentrations of nitrate in all surface-water sites sampled by the Delaware Department of Natural Resources and EnviroAuthorsJudith M. Denver, Alex M. Soroka, Betzaida Reyes, Todd R. Lester, Deborah A. Bringman, M.S. Brownley