A three-dimensional groundwater flow model was developed to characterize groundwater resources of 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 was 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. This model was previously published by the U.S. Geological Survey in a Scientific Investigations Report (https://doi.org/10.3133/sir20175158) and the model input and output files are available in a data release (https://doi.org/10.5066/F75B01CZ). The underlying directories contain all of the input and output files for predictive simulations of groundwater response to selected scenarios for the uppermost principal aquifer systems in the Williston Basin, United States and Canada. The predictive simulations were created using base model files from a model developed by Davis and Long and documented in the U.S. Geological Survey Scientific Investigations Report 2017-5158 (https://doi.org/10.3133/sir20175158). Model archive files are documented and are available in an online data release (https://doi.org/10.5066/F75B01CZ). The three-dimensional groundwater-flow model was developed using the numerical modeling software, MODFLOW-NWT. For this study, the numerical groundwater-flow model was used to simulated three predictive scenarios: scenario 1 was focused on flowing artesian wells, and was used to simulate 1960‒2035 hydraulic-head changes that would result if none of the flowing artesian wells in the model area were capped or plugged during this period and other conditions remained constant; scenario 2 simulated 10-year drought for 2006‒15, with no increases in groundwater pumping after 2005; and scenario 3 was identical to scenario 2, except that it also applied the increased groundwater withdrawals necessary to fill the needs of energy-resource production for 2006‒15. A data-worth analysis for evaluation of potential hydrologic monitoring networks was also accomplished using the numerical model. 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/pp1841). This data release also includes MODFLOW-NWT (version 1.0.9) 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 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.

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.

A previously developed model (https://doi.org/10.3133/sir20175098) was coupled with downscaled climate model data to determine the impact of climate variability on base flow and groundwater storage in the North Fork Red River aquifer, Oklahoma. The North Fork Red River aquifer is an alluvial aquifer that discharges groundwater to the North Fork Red River, which provides inflow to Lake Altus, an important water source for the surrounding communities. The impact of climate variability on hydrologic systems and the resulting effects on basins has become an important topic in assessing future water resources. Global climate projections from general circulation models, including the Coupled Model Intercomparison Project Phase 5 (CMIP5), have been developed to improve the understanding of climate science and forecast future climatic conditions. Due to the impact of climate variations on groundwater resources, it is important to communicate the ranges of results with water resource managers. To approximate a range in future base flow conditions and flow into Lake Altus, the Coupled Model Intercomparison Project Phase 5 climate data was downscaled to watershed scale using monthly Bias-Correction Spatial Disaggregation techniques. A time-series of scaling factors were developed and interpolated for three climate scenarios (central tendency, warmer/drier, and less warm-wetter) representing a range of future climate conditions for the period 2045–2074. These scaling factors were then applied to an existing soil-water-balance model dataset with climate data for the baseline period 1980–2009 to produce recharge and evapotranspiration estimations for this future period. The downscaled climate data was applied to the finite-difference numerical groundwater-flow model of the North Fork Red River aquifer using MODFLOW-2005 with the Newton formulation solver (MODFLOW-NWT) which was temporally discretized into 373 monthly transient stress periods representing the period 1980–2010. Three climate scenarios (central tendency, warmer/drier, and less warm/wetter) representing a range of future climate conditions for the period 2045–2074 were simulated. This USGS data release contains all of the input and output files for the simulations described in the associated journal article (http://doi.org/10.1007/s10040-020-02230-x).

A previously published MODFLOW-NWT groundwater-flow model for the Rush Springs aquifer in western Oklahoma (using 1 steady state stress period followed by 444 monthly stress periods representing 1979-2015; Ellis, 2018a) was used as the basis of several groundwater-use scenarios. The model is a 3-layer model including the Cloud Chief formation (confining unit of the Rush Springs aquifer), alluvial and terrace deposits, and the Rush Springs aquifer. The scenarios were used to assess the effects of increasing groundwater withdrawals from the Rush Springs aquifer on base flows to streams that flow into Fort Cobb Reservoir to address concerns over groundwater use reducing inflows to the lake. The effects of groundwater use on base flow were assessed using four scenarios: (1) scaling the equal-proportionate-share rate estimated by Ellis (2018a), (2) scaling historical groundwater withdrawals, (3) scaling historical groundwater withdrawals using zones, and (4) base flow depletion simulations. This USGS data release contains all input and output files for the groundwater-flow simulations and streamflow and base-flow statistics described in the associated model documentation report (https://doi.org/10.3133/sir20245002). Supporting geospatial data are provided that were used to help construct the scenarios and used to display model outputs.

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).

A previously published MODFLOW-NWT groundwater-flow model for the Rush Springs aquifer in western Oklahoma (using 1 steady state stress period followed by 444 monthly stress periods representing 1979-2015; Ellis, 2018a) was used as the basis of several groundwater-use scenarios. The model is a 3-layer model including the Cloud Chief formation (confining unit of the Rush Springs aquifer), alluvial and terrace deposits, and the Rush Springs aquifer. The scenarios were used to assess the effects of increasing groundwater withdrawals from the Rush Springs aquifer on base flows to streams that flow into Fort Cobb Reservoir to address concerns over groundwater use reducing inflows to the lake. The effects of groundwater use on base flow were assessed using four scenarios: (1) scaling the equal-proportionate-share rate estimated by Ellis (2018a), (2) scaling historical groundwater withdrawals, (3) scaling historical groundwater withdrawals using zones, and (4) base flow depletion simulations. This USGS data release contains all input and output files for the groundwater-flow simulations and streamflow and base-flow statistics described in the associated model documentation report (https://doi.org/10.3133/sir20245002). Supporting geospatial data are provided that were used to help construct the scenarios and used to display model outputs.

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.