A three-dimensional groundwater flow model was developed to characterize groundwater resources the uppermost principal aquifers in the Williston structural basin in parts of Montana, North Dakota, and South Dakota in the United States and of Manitoba and Saskatchewan in Canada as part of a detailed assessment of the groundwater availability of the area. The uppermost principal aquifers are comprised of the glacial, lower Tertiary, and Upper Cretaceous aquifer systems. The model was developed as a part of the U.S. Geological Survey Water Availability and Use Science Program's effort to conduct large-scale multidisciplinary regional studies of groundwater availability. The numerical model is intended to be used to (1) simulate hydrologic scenarios of interest to groundwater managers and to advance the understanding of groundwater budgets and components including recharge, discharge, and aquifer storage for the entire system, (2) compute historical and projected system response to natural and anthropogenic stresses, and (3) evaluate potential hydrologic monitoring programs at a scale relevant to basin-wide water-management decisions. The three-dimensional groundwater-flow model was developed using the numerical modeling software, MODFLOW-NWT. The steady-state (mean) hydrological conditions included data from 1981 to 2005, and transient (temporally-varying) conditions included a combination of a steady state period with data prior to 1960, and a transient period from 1961 to 2005. The model was calibrated by attempting to match simulated and measured or estimated hydraulic heads, differences in hydraulic heads between aquifers, stream base flow, and measured flow at flowing artesian wells. Sub-regional water budgets for the model area were produced with ZONEBUDGET. This USGS data release contains all of the input and output files for the model described in the associated model documentation report (https://doi.org/10.3133/sir201755158). This data release also includes (1) MODFLOW-NWT (version 1.0.9) source code, and (2) ZONEBUDGET source code.

This groundwater flow model used a previously developed three-dimensional groundwater flow model (https://doi.org/10.3133/sir20165153) was used to assess future groundwater availability in the Northern High Plains aquifer in Colorado, Kansas, Nebraska, South Dakota, and Wyoming. In this groundwater flow model, a modified version of a previously published soil-water-balance (SWB) model (https://doi.org/10.3133/sir20165153) estimates recharge and groundwater withdrawals for irrigation using climatic, soils, land-cover data. For this groundwater flow model, the SWB output was adjusted in areas where surface water is used for irrigation and adjusted the same as was done through calibration of the previously-developed groundwater flow model. The model was designed as a tool for regional evaluations of groundwater resources and of groundwater interactions with streams and other hydrologic features resulting from current or forecasted conditions. For this study, five forecast scenarios are included, a baseline forecast, two forecasts evaluating the effects of land use changes, and two forecast evaluating the effects of climatic changes. This USGS data release also includes MODFLOW-NWT (version 1.0.5) source code and SWB source code. This USGS data release contains all of the input and output files for the model described in the associated model documentation report (https://doi.org/10.3133/pp1864).

A three-dimensional groundwater flow model was developed to characterize groundwater resources and the interaction of groundwater with streams and other hydrologic features in the Northern High Plains aquifer. The Northern High Plains aquifer is generally unconfined; most of the water withdrawn from the aquifer is used for irrigation. A modified version of a previously published soil-water-balance (SWB) model estimates recharge using climatic, soils, land cover data, in addition to data for groundwater withdrawals for irrigation. The SWB output was adjusted in areas where surface water is used for irrigation. The groundwater flow model results were calibrated using parameter estimation to measured groundwater levels and estimated stream base flows. The model was designed as a tool for regional evaluations of groundwater resources and of groundwater interactions with streams and other hydrologic features resulting from current or forecasted conditions. This USGS data release contains all of the input and output files for the model described in the associated model documentation report (https://doi.org/10.3133/sir20165153). This data release also includes (1) MODFLOW-NWT (version 1.0.9) source code, and (2) SWB source code in two formats.

A 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 national study of regional systems (https://pubs.usgs.gov/circ/1323/). The CPRAS assessment includes the status of groundwater resources, how these resources have changed over time, and development and application of tools to estimate system responses to stresses from future uses and climate variability and change. A major product of this assessment is a numerical groundwater-flow model of the system. Two models were constructed to simulate groundwater flow in the CPRAS: a steady-state predevelopment model representing conditions before large-scale pumping and irrigation altered the system, and a transient model representing the period 1900–2007. Construction of the model, development and calibration of the steady-state and transient simulations, as well as, a commingling scenario, is documented in the Scientific Investigations Report 2014-5127 (https://doi.org/10.3133/sir20145127). Two additional scenarios were completed and documented in the U.S. Geological Survey Professional Paper 1817 (https://doi.org/10.3133/pp1817). One scenario represents long-term equilibrium under 2007 conditions and the other modified the equilibrium conditions to account for potential increased pumpage under projected temperature increases with climate change. The model is a useful tool for investigating water supply, water demand, management strategies, groundwater-surface water exchanges, and potential effects of changing climate on the hydrologic system. This USGS data release contains all of the input and output files for the simulations described in the associated model documentation reports: U.S. Geological Survey Professional Paper 1817 (https://doi.org/10.3133/pp1817) and the modeling report that documents the construction and calibration of the model, Scientific Investigations Report 2014-5127 (https://doi.org/10.3133/sir20145127).

A 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 national study of regional systems (https://pubs.usgs.gov/circ/1323/). The CPRAS assessment includes the status of groundwater resources, how these resources have changed over time, and development and application of tools to estimate system responses to stresses from future uses and climate variability and change. A major product of this assessment is a numerical groundwater-flow model of the system. Two models were constructed to simulate groundwater flow in the CPRAS: a steady-state predevelopment model representing conditions before large-scale pumping and irrigation altered the system, and a transient model representing the period 1900–2007. Construction of the model, development and calibration of the steady-state and transient simulations, as well as, a commingling scenario, is documented in the Scientific Investigations Report 2014-5127 (https://doi.org/10.3133/sir20145127). Two additional scenarios were completed and documented in the U.S. Geological Survey Professional Paper 1817 (https://doi.org/10.3133/pp1817). One scenario represents long-term equilibrium under 2007 conditions and the other modified the equilibrium conditions to account for potential increased pumpage under projected temperature increases with climate change. The model is a useful tool for investigating water supply, water demand, management strategies, groundwater-surface water exchanges, and potential effects of changing climate on the hydrologic system. This USGS data release contains all of the input and output files for the simulations described in the associated model documentation reports: U.S. Geological Survey Professional Paper 1817 (https://doi.org/10.3133/pp1817) and the modeling report that documents the construction and calibration of the model, Scientific Investigations Report 2014-5127 (https://doi.org/10.3133/sir20145127).

The U.S. Geological Survey (USGS), in cooperation with the Oklahoma Water Resources Board (OWRB), constructed a finite-difference numerical groundwater-flow model of the Washita River aquifer by using MODFLOW-2005 (Harbaugh, 2005) with the Newton formulation solver (MODFLOW-NWT). The 1973 Oklahoma Groundwater Law requires that the OWRB conduct hydrologic investigations of the State’s aquifers to determine the maximum annual yield (MAY) for each groundwater basin. The MAY is defined as the total amount of fresh groundwater that can be annually withdrawn while allowing a minimum 20-year life of that groundwater basin. For alluvium and terrace groundwater basins, the life requirement is satisfied if, after 20 years of MAY withdrawals, 50 percent of the groundwater basin (hereinafter referred to as an “aquifer”) retains a saturated thickness of at least 5 ft. Once a MAY has been established, the amount of land owned or leased by a groundwater-use permit applicant determines the annual volume of water allocated to that groundwater-use permit applicant. The annual volume of groundwater allocated per acre of land is known as the equal-proportionate-share (EPS) pumping rate. The OWRB issued a final order on November 13, 1990, that established the MAY (81,840 and 46,935 acre-feet per year [acre-ft/yr]) and EPS pumping rate (1.5 and 1.0 acre-foot per acre per year) for reaches 3 and 4, respectively, of the Washita River aquifer in southern Oklahoma. Because more than 20 years have elapsed since the final order was issued, the USGS, in cooperation with the OWRB, conducted an updated hydrologic investigation and evaluated the effects of potential groundwater withdrawals on groundwater flow and availability in the Washita River aquifer in southern Oklahoma. Reach 3 extends from near Anadarko, Okla., to Alex, Okla., and reach 4 extends from near Alex to south of Davis, Okla. Twenty-four simulations are included in this data release: a simulation for the calibrated numerical groundwater-flow model, 18 scenario simulations to evaluate the EPS pumping rate, 4 scenario simulations to evaluate groundwater storage over a 50-year period, and 1 scenario simulation to evaluate effects of a hypothetical drought. This USGS data release contains all of the input and output files for the simulations described in the associated model documentation report (https://doi.org/10.3133/sir20235072).

The U.S. Geological Survey (USGS), in cooperation with the Oklahoma Water Resources Board (OWRB), constructed a finite-difference numerical groundwater-flow model of the Washita River aquifer by using MODFLOW-2005 (Harbaugh, 2005) with the Newton formulation solver (MODFLOW-NWT). The 1973 Oklahoma Groundwater Law requires that the OWRB conduct hydrologic investigations of the State’s aquifers to determine the maximum annual yield (MAY) for each groundwater basin. The MAY is defined as the total amount of fresh groundwater that can be annually withdrawn while allowing a minimum 20-year life of that groundwater basin. For alluvium and terrace groundwater basins, the life requirement is satisfied if, after 20 years of MAY withdrawals, 50 percent of the groundwater basin (hereinafter referred to as an “aquifer”) retains a saturated thickness of at least 5 ft. Once a MAY has been established, the amount of land owned or leased by a groundwater-use permit applicant determines the annual volume of water allocated to that groundwater-use permit applicant. The annual volume of groundwater allocated per acre of land is known as the equal-proportionate-share (EPS) pumping rate. The OWRB issued a final order on November 13, 1990, that established the MAY (81,840 and 46,935 acre-feet per year [acre-ft/yr]) and EPS pumping rate (1.5 and 1.0 acre-foot per acre per year) for reaches 3 and 4, respectively, of the Washita River aquifer in southern Oklahoma. Because more than 20 years have elapsed since the final order was issued, the USGS, in cooperation with the OWRB, conducted an updated hydrologic investigation and evaluated the effects of potential groundwater withdrawals on groundwater flow and availability in the Washita River aquifer in southern Oklahoma. Reach 3 extends from near Anadarko, Okla., to Alex, Okla., and reach 4 extends from near Alex to south of Davis, Okla. Twenty-four simulations are included in this data release: a simulation for the calibrated numerical groundwater-flow model, 18 scenario simulations to evaluate the EPS pumping rate, 4 scenario simulations to evaluate groundwater storage over a 50-year period, and 1 scenario simulation to evaluate effects of a hypothetical drought. This USGS data release contains all of the input and output files for the simulations described in the associated model documentation report (https://doi.org/10.3133/sir20235072).

The U.S. Geological Survey, in cooperation with the Oklahoma Water Resources Board, constructed a finite-difference numerical groundwater-flow model of the Salt Fork Red River aquifer using MODFLOW with the Newton formulation solver (MODFLOW-NWT). The 1973 Oklahoma Water Law requires the Oklahoma Water Resources Board to conduct hydrologic investigations of the State’s aquifers to support a determination of the maximum annual yield (MAY) for each groundwater basin. The MAY is defined as the amount of fresh groundwater that can be withdrawn annually while ensuring a minimum 20-year life of the groundwater basin. For alluvium and terrace aquifers, the groundwater-basin-life requirement is satisfied if, after 20 years of MAY withdrawals, 50 percent of the groundwater basin retains a saturated thickness of at least 5 ft. When a MAY has been established, the amount of land owned or leased by a permit applicant determines the annual volume of water allocated to that permit applicant. The annual volume of water allocated per acre of land is known as the equal-proportionate-share (EPS) pumping rate. Because the MAY and EPS have not yet been established for the Salt Fork Red River aquifer, the U.S. Geological Survey, in cooperation with the Oklahoma Water Resources Board, conducted a hydrologic investigation and developed a calibrated numerical groundwater-flow model to evaluate the effects of potential groundwater withdrawals on groundwater availability in the Salt Fork Red River aquifer. The results of groundwater-availability scenarios run on the calibrated numerical groundwater-flow model could be used by the Oklahoma Water Resources Board to evaluate the maximum annual yield of groundwater from the Salt Fork Red River aquifer in Oklahoma. The numerical model was temporally discretized into 1 initial steady-state stress period representing average conditions during 1980-2015 and 432 monthly transient stress periods representing the period 1980-2015. This U.S. Geological Survey data release contains all of the input and output files for the simulations described in the associated model documentation report (https://doi.org/10.3133/sir20215003).

The U.S. Geological Survey (USGS), in cooperation with the Oklahoma Water Resources Board (OWRB), constructed a finite-difference numerical groundwater-flow model of the Boone and Roubidoux aquifers in northeastern Oklahoma by using MODFLOW-NWT (version 1.1.4) with the Newton formulation solver to simulate groundwater flow and account for the drying and rewetting of cells within the groundwater-flow model. The numerical groundwater-flow model was discretized into four layers consisting of 354 rows by 261 columns with a 2,000-feet by 2,000-feet cell size. The model layers were used to simulate the Western Interior Plains confining system, the Boone aquifer, the Ozark confining unit, and the Roubidoux aquifer. The model was temporally discretized into one steady-state stress period followed by 456 monthly transient stress periods spanning from January 1980 to December 2017. The steady-state stress period typically consisted of mean annual inputs from January 1980 to December 2017, but inputs from 1979 were included for some of the simulations.

The U.S. Geological Survey (USGS), in cooperation with the Oklahoma Water Resources Board (OWRB), constructed a finite-difference numerical groundwater-flow model of the Boone and Roubidoux aquifers in northeastern Oklahoma by using MODFLOW-NWT (version 1.1.4) with the Newton formulation solver to simulate groundwater flow and account for the drying and rewetting of cells within the groundwater-flow model. The numerical groundwater-flow model was discretized into four layers consisting of 354 rows by 261 columns with a 2,000-feet by 2,000-feet cell size. The model layers were used to simulate the Western Interior Plains confining system, the Boone aquifer, the Ozark confining unit, and the Roubidoux aquifer. The model was temporally discretized into one steady-state stress period followed by 456 monthly transient stress periods spanning from January 1980 to December 2017. The steady-state stress period typically consisted of mean annual inputs from January 1980 to December 2017, but inputs from 1979 were included for some of the simulations.