Andy Long has more than 25 years of experience assessing groundwater flow and transport through numerical modeling, analyzing ambient and injected tracers, and geophysical methods.
Groundwater Specialist, USGS Washington Water Science Center (July 2015 – present) - I advise and train staff scientists and technicians on technical issues, including interpretive studies and the collection, management, and archival of data. I advise managers of the science center in building and guiding the overall groundwater studies and data programs. I conduct scientific investigations involv
Chair and Vice Chair, Washington Hydrogeology Symposium (2017 – present) – http://depts.washington.edu/uwconf/wordpress/wahgs/
Research Hydrologist, USGS Dakota Water Science Center (DWSC; 2009 – 2015) –
Developed innovative methods to better understand, quantify, and test hypotheses related to groundwater flow and transport in karst aquifers. Topics include groundwater age dating, lumped-parameter models, aquifer classification, hydrochemical evaluation, heat transport, and groundwater recharge.
Adjunct Assistant Professor, South Dakota School of Mines and Technology (SDSMT; Oct 2005 – 2018) –
Served on eight graduate advisory committees for M.S. and Ph.D. students and gave numerous guest lectures.
Hydrologist, USGS DWSC (Jan 1999 – Oct 2009) –
This involved numerical modeling of groundwater flow and solute transport, dye tracing experiments in karst aquifers, aquifer pumping tests, and development of new research models.
Consultant (1994–1998) –
Conducted GIS analysis and groundwater modeling with MODFLOW related to a proposed low-level nuclear-waste site for the Boyd County Monitoring Committee in Nebraska. Consulted for Terra Nitrogen in Sergeant Bluff, Iowa and simulated groundwater flow and transport with MODFLOW, MOC, and GIS analysis to assess the movement of ammonia contamination.
Research assistant, SDSMT (1995–1998) –
Developed and wrote the FORTRAN computer code for a three-dimensional groundwater model to simulate dual-porosity flow in karst aquifers. Collaborated with a team of researchers on the design of a numerical model to simulate surface-water and groundwater flow, dynamically linked to atmospheric processes.
Hydrologist, Rapid City Water Department (1994-1995) –
Collaborated with the USGS to simulated groundwater flow in karst aquifers.
Science and Products
Hydrochemical Analysis of Groundwater in Jewel Cave National Monument
Assess the utility of a regional aquifer system groundwater model to inform the USGS National Hydrologic Model
Walla Walla River Basin groundwater-flow system, Oregon-Washington
Williston and Powder River Basins Groundwater Availability Study
Keyport Groundwater Model
RRAWFLOW: Rainfall-Response Aquifer and Watershed Flow Model
Groundwater Flow, Quality, and Mixing in the Wind Cave National Park Area, South Dakota
Kitsap Groundwater Model
Pasco Groundwater Storage
Chimacum GW Model
Yakima River Basin
MODFLOW-NWT model used to evaluate the groundwater availability of the Columbia Plateau Regional Aquifer System, Washington, Oregon, and Idaho
MODFLOW-NWT model to simulate the groundwater flow system near Puget Sound, Pierce and King Counties, Washington
Water Use Data for Hydraulic Fracturing Treatments in and near the Williston Basin, United States, 2000-2015
Data from simulations of ecological and hydrologic response to climate change scenarios at Wind Cave National Park, South Dakota, 1901-2050
Spectral analysis to quantify the response of groundwater levels to precipitation — Northwestern United States
300,000 yr history of water-table fluctuations at Wind Cave, South Dakota, USA—Scale, timing, and groundwater mixing in the Madison Aquifer
Multivariate analysis of hydrochemical data for Jewel Cave, Wind Cave, and surrounding areas
Data management plan for the U.S. Geological Survey Washington Water Science Center
Williston Basin groundwater availability, United States and Canada
Groundwater availability of the Williston Basin, United States and Canada
Construction and calibration of a groundwater-flow model to assess groundwater availability in the uppermost principal aquifer systems of the Williston Basin, United States and Canada
Potential application of radiogenic isotopes and geophysical methods to understand the hydrothermal dystem of the Upper Geyser Basin, Yellowstone National Park
RRAWFLOW: Rainfall-Response Aquifer and Watershed Flow Model (v1.15)
Effects of projected climate (2011–50) on karst hydrology and species vulnerability—Edwards aquifer, south-central Texas, and Madison aquifer, western South Dakota
Historical and projected climate (1901–2050) and hydrologic response of karst aquifers, and species vulnerability in south-central Texas and western South Dakota
Conceptual model of the uppermost principal aquifer systems in the Williston and Powder River structural basins, United States and Canada
Science and Products
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Hydrochemical Analysis of Groundwater in Jewel Cave National MonumentThe Issue: The park’s landscape and geomorphology is characterized as a carbonate karst environment, with sinking streams and fast connections between surface water and groundwater, resulting in high vulnerability of contamination to groundwater. Now that subterranean lakes have been discovered in Jewel Cave, understanding the groundwater connection of the lakes therein to the lakes in nearby Wind...
Assess the utility of a regional aquifer system groundwater model to inform the USGS National Hydrologic ModelThe Issue: In Washington State, groundwater (GW) inflow to streams, or baseflow, is essential for maintaining aquatic habitats, and for out-of-stream uses such as irrigated agriculture during the typically dry summers. However, the National Hydrologic Model (NHM) currently is most suited to predicting total daily streamflow. This project aims to assess the NHM’s performance in simulating baseflow...
Walla Walla River Basin groundwater-flow system, Oregon-WashingtonThe Issue: Decades of declining groundwater levels in the Walla Walla River Basin (WWRB), which spans Oregon and Washington, are affecting instream flows for threatened and culturally important fish populations and water availability for competing interests across state lines. The public and state resource management agencies have begun implementing efforts to stabilize groundwater levels and...
Williston and Powder River Basins Groundwater Availability StudyThe development of two nationally important energy-producing areas, the Williston structural basin (containing the Bakken Formation) and Powder River structural basin, provide a critical opportunity to study the water-energy nexus within a groundwater context. Large volumes of water are needed for energy development in these basins. The hydraulically connected aquifers in the regional glacial...
Keyport Groundwater ModelThe Issue: Chlorinated volatile organic compounds have impacted groundwater beneath a former 9-acre landfill at OU 1 of the Naval Base Kitsap Keyport, Washington. The landfill is adjacent to tidal flats that are an extension of Liberty and Dogfish Bays and was the primary disposal area for domestic and industrial waste generated by NBK Keyport from the 1930s through 1973. The Navy needs a detailed...
Quincy GroundwaterThe Issue: Since 1952, water diverted from the Columbia River for irrigation in parts of the Quincy Subarea in eastern Washington has resulted in rising groundwater levels and increased groundwater flows and storage. Managers of groundwater in the area need a better understanding of the flow system before and after the start of irrigation. How the USGS will help: In a joint effort with Washington...
RRAWFLOW: Rainfall-Response Aquifer and Watershed Flow ModelRRAWFLOW: Rainfall-Response Aquifer and Watershed Flow Model
Groundwater Flow, Quality, and Mixing in the Wind Cave National Park Area, South DakotaProject Period: 2007-2010Cooperator: National Park ServiceProject Chief: Andrew Long
Kitsap Groundwater ModelThe Issue: Groundwater provides a major source of drinking water for the population of the Kitsap Peninsula. Consequently, as the population grows, so does the demand for groundwater. However, the quantity of usable groundwater is limited, largely because the Peninsula is bounded by seawater and the potential for water-level declines and seawater intrusion increases as groundwater usage increases...
Pasco Groundwater StorageThe Issue: Since 1952 water diverted from the Columbia River has been used to irrigate parts of the Pasco basin in eastern Washington. As a result of the surface-water irrigation, groundwater levels generally have risen in the area. The increases in groundwater fluxes and groundwater in storage have created a need to better understand the flow system before and after the start of irrigation to...
Chimacum GW ModelProjected increases in population and development in northeastern Jefferson County, Washington, are expected to lead to increased groundwater withdrawals in the Chimacum Creek Basin. Changes in land use and climate could reduce groundwater recharge, thereby reducing groundwater available for drinking and for baseflow to streams that host endangered fish species. The USGS is developing quantitative...
Yakima River BasinThe Yakima River flows 215 miles from the outlet of Keechelus Lake in the central Washington Cascades southeasterly to the Columbia River, draining an area of 6,155 square miles. The Yakima River Basin is one of the most intensively irrigated areas in the United States. Population in the Yakima River Basin was about 238,000 in 1990. Increasing demands for water for municipal, fisheries...
MODFLOW-NWT model used to evaluate the groundwater availability of the Columbia Plateau Regional Aquifer System, Washington, Oregon, and IdahoA three-dimensional groundwater flow model (MODFLOW-NWT) of the Columbia Plateau Regional aquifer (CPRAS) in Washington, Oregon, and Idaho was developed to provide an integrated understanding of the hydrologic system to implement effective water-resource management strategies. The U.S. Geological Survey (USGS) Groundwater Resources Program assessed the groundwater availability as part of a nationa
MODFLOW-NWT model to simulate the groundwater flow system near Puget Sound, Pierce and King Counties, WashingtonA three-dimensional groundwater flow model, constructed in MODFLOW-NWT, was developed to evaluate the groundwater flow system near Puget Sound, Pierce and King Counties, Washington. A steady-state model version was constructed to simulate equilibrium conditions, while a transient model version was constructed to simulate monthly variability from January 2005 to December 2015. The model was used to
Water Use Data for Hydraulic Fracturing Treatments in and near the Williston Basin, United States, 2000-2015Water used for hydraulic fracturing treatments in and near the Williston Basin during 2000-2015, was estimated using data reported in IHS Markit (TM) (2016). Hydraulic fracturing treatment data from IHS Markit (TM) (2016) may include volumes in a variety of measurement units, and they may include multiple treatments per well. All listed treatments within the study area were converted to gallons an
Data from simulations of ecological and hydrologic response to climate change scenarios at Wind Cave National Park, South Dakota, 1901-2050This data release contains data discussed in its larger work citation (Symstad et al., 2017, Climate Risk Management 17:78-91, Associated Item at right). "ClimateComparisonData.csv" contains summary metrics of six climate projections used as climate input for quantitative simulations of hydrologic and ecological responses to climate change at Wind Cave National Park (WCNP) and the same summary met
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Spectral analysis to quantify the response of groundwater levels to precipitation — Northwestern United StatesPersistent atmospheric patterns that lead to wet and dry seasons and droughts over periods of months to decades and longer-term climate change over periods of decades to millennia affect groundwater resources. Changes in groundwater storage and the resulting groundwater discharge from most aquifers is relatively slow and steady compared to the variability of daily precipitation. The response of grAuthorsAndrew J. Long, Christopher P. Konrad
300,000 yr history of water-table fluctuations at Wind Cave, South Dakota, USA—Scale, timing, and groundwater mixing in the Madison AquiferDeposits of calcite coating the lower passages of Wind Cave in the southern Black Hills of South Dakota were precipitated under phreatic conditions. Data from samples associated with a new cave survey and hydrologic studies indicate that past water tables within Wind Cave reached a maximum height of 45 m above modern levels but were mostly confined to 25 m or less. Uranium-series ages for basal laAuthorsJames B. Paces, Margaret V. Palmer, Arthur N. Palmer, Andrew J. Long, Matthew P. Emmons
Multivariate analysis of hydrochemical data for Jewel Cave, Wind Cave, and surrounding areasJewel Cave National Monument and Wind Cave National Park in South Dakota contain two of the six longest caves worldwide. These caves contain subterranean lakes that are important points of intersection between the water table of the Madison aquifer and the caves. During 2015 to 2017, several subterranean lakes were discovered in Jewel Cave, which previously was thought to be above the regional watAuthorsAndrew J. Long, James B. Paces, William G. Eldridge
Data management plan for the U.S. Geological Survey Washington Water Science CenterThe primary mission of the U.S. Geological Survey (USGS) Water Mission Area is to collect and disseminate reliable, impartial, and timely information needed to understand the water resources of the Nation, including data on streamflow, groundwater, water quality, water use, and availability. Management of data throughout the entire data lifecycle is necessary to meet the mission and maintain the UAuthorsKathleen E. Conn, Mark C. Mastin, Andrew J. Long, Richard S. Dinicola, Cynthia Barton
Williston Basin groundwater availability, United States and CanadaThe Williston Basin contains important oil and gas resources for the Nation. Freshwater supplies are limited in this semiarid area, and oil and gas development can require large volumes of freshwater. Groundwater is the primary source of water for many water users in the Williston Basin, so to better understand these resources, the U.S. Geological Survey (USGS) assessed the groundwater availabilitAuthorsJoanna N. Thamke, Andrew J. Long, Kyle W. Davis
Groundwater availability of the Williston Basin, United States and CanadaExecutive SummaryThe Williston Basin of the Northern Great Plains is a sedimentary basin—a geologic bowl-like structure filled with layered sedimentary rocks dating as far back as the Paleozoic age. The basin, which is nationally important for the production of energy resources, spans Montana, North Dakota, and South Dakota in the United States, and Manitoba and Saskatchewan in Canada. The three uAuthorsAndrew J. Long, Joanna N. Thamke, Kyle W. Davis, Timothy T. Bartos
Construction and calibration of a groundwater-flow model to assess groundwater availability in the uppermost principal aquifer systems of the Williston Basin, United States and CanadaThe U.S. Geological Survey developed a groundwater-flow model for the uppermost principal aquifer systems in the Williston Basin in parts of Montana, North Dakota, and South Dakota in the United States and parts of Manitoba and Saskatchewan in Canada as part of a detailed assessment of the groundwater availability in the area. The assessment was done because of the potential for increased demandsAuthorsKyle W. Davis, Andrew J. Long
Potential application of radiogenic isotopes and geophysical methods to understand the hydrothermal dystem of the Upper Geyser Basin, Yellowstone National ParkNumerous geochemical and geophysical studies have been conducted at Yellowstone National Park to better understand the hydrogeologic processes supporting the thermal features of the Park. This report provides the first 87Sr/86Sr and 234U/238U data for thermal water from the Upper Geyser Basin (UGB) intended to evaluate whether heavy radiogenic isotopes might provide insight to sources of groundwatAuthorsJames B. Paces, Andrew J. Long, Karl R. Koth
RRAWFLOW: Rainfall-Response Aquifer and Watershed Flow Model (v1.15)The Rainfall-Response Aquifer and Watershed Flow Model (RRAWFLOW) is a lumped-parameter model that simulates streamflow, spring flow, groundwater level, or solute transport for a measurement point in response to a system input of precipitation, recharge, or solute injection. I introduce the first version of RRAWFLOW available for download and public use and describe additional options. The open-soAuthorsAndrew J. Long
Effects of projected climate (2011–50) on karst hydrology and species vulnerability—Edwards aquifer, south-central Texas, and Madison aquifer, western South DakotaKarst aquifers—formed by the dissolution of soluble rocks such as limestone—are critical groundwater resources in North America, and karst springs, caves, and streams provide habitat for unique flora and fauna. Springflow and groundwater levels in karst terrane can change greatly over short time scales, and therefore are likely to respond rapidly to climate change. How might the biological communiAuthorsBarbara Mahler, John F. Stamm, Mary F. Poteet, Amy J. Symstad, MaryLynn Musgrove, Andrew J. Long, Parker A. Norton
Historical and projected climate (1901–2050) and hydrologic response of karst aquifers, and species vulnerability in south-central Texas and western South DakotaTwo karst aquifers, the Edwards aquifer in the Balcones Escarpment region of south-central Texas and the Madison aquifer in the Black Hills of western South Dakota, were evaluated for hydrologic response to projected climate change through 2050. Edwards aquifer sites include Barton Springs, the Bexar County Index Well, and Comal Springs. Madison aquifer sites include Spearfish Creek and Rhoads ForAuthorsJohn F. Stamm, Mary F. Poteet, Amy J. Symstad, MaryLynn Musgrove, Andrew J. Long, Barbara Mahler, Parker A. Norton
Conceptual model of the uppermost principal aquifer systems in the Williston and Powder River structural basins, United States and CanadaThe three uppermost principal aquifer systems of the Northern Great Plains—the glacial, lower Tertiary, and Upper Cretaceous aquifer systems—are described in this report and provide water for irrigation, mining, public and domestic supply, livestock, and industrial uses. These aquifer systems primarily are present in two nationally important fossil-fuelproducing areas: the Williston and Powder RivAuthorsAndrew J. Long, Katherine R. Aurand, Jennifer M. Bednar, Kyle W. Davis, Jonathan D.R.G. McKaskey, Joanna N. Thamke