In 2017 the U.S. Geological Survey, in cooperation with the Oklahoma Water Resources Board, published a calibrated numerical groundwater-flow model and associated model documentation report that evaluated the effects of potential groundwater withdrawals on groundwater flow and availability in the North Fork Red River aquifer in southwest Oklahoma. The results of groundwater-availability scenarios run on the calibrated numerical groundwater-flow model could be used by the Oklahoma Water Resources Board to reevaluate the maximum annual yield of groundwater from the North Fork Red River aquifer in Oklahoma. The numerical groundwater-flow model was built on a hydrogeologic framework and a conceptual groundwater-flow model derived from previously published and newly collected hydrologic data. A hydrogeologic framework is a three-dimensional representation of the aquifer and the surrounding geologic units at a scale that captures the regional controls on groundwater flow. The hydrogeologic framework for the North Fork Red River aquifer included a definition of the aquifer extent and potentiometric surface, as well as a description of the textural and hydraulic properties of aquifer materials. A conceptual groundwater-flow model is a simplified description of the major inflow and outflow sources (hydrologic boundaries) of a groundwater-flow system as well as an accounting of the estimated mean flows from those sources (water budget) for a specified period of time. The hydrogeologic framework and conceptual model are necessary constraints used in the construction and calibration of a scientifically defensible numerical groundwater-flow model that reasonably represents the groundwater-flow system. A finite-difference numerical groundwater-flow model of the North Fork Red River aquifer was constructed by using MODFLOW-2005 with the Newton formulation solver (MODFLOW-NWT). Data inputs for each package were specified in machine-readable text files. The numerical model of the North Fork Red River aquifer had 385 rows, 460 columns, about 27,600 active cells of 886 by 886 ft (270 by 270 meters), and 2 convertible layers. The top layer (layer 1) represented the undifferentiated Quaternary alluvium and terrace deposits with variable thickness determined from the hydrogeologic framework, and the bottom layer (layer 2) represented the Permian bedrock with a nominal thickness of about 100 feet. The model active area was created from the North Fork Red River aquifer extent and expanded in some areas to ensure that each active cell was in connection with at least one other active cell. One terrace lobe in northern Beckham County was not included in the model active area because it was almost separated spatially and hydraulically from the rest of the North Fork Red River aquifer. The numerical model was temporally discretized into 408 monthly transient stress periods (each with 2 time steps) representing the period 1980–2013. An initial steady-state stress period, in which the groundwater-flow equation had no storage component, represented mean annual inflows to and outflows from the aquifer and produced a solution that was used as the initial condition for subsequent transient stress periods. The numerical model was constructed in units of meters and days. 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/sir20175098).

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.

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 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 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).

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 Salt Fork Arkansas River and Chikaskia River alluvial aquifers by using MODFLOW-2005 with the Newton formulation solver (MODFLOW-NWT). The model included the Chikaskia River alluvial aquifer, which is classified as a minor aquifer by the OWRB and is hydrologically connected to the Salt Fork Arkansas River alluvial aquifer. 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 feet. 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. At the time of this publication (2025), a hydrologic investigation and determination of the MAY for the Salt Fork Arkansas River alluvial aquifer had not been completed. The U.S. Geological Survey, in cooperation with the OWRB, conducted a hydrologic investigation and evaluated the simulated effects of potential groundwater withdrawals on groundwater flow and availability in the Salt Fork Arkansas River alluvial aquifer in northern Oklahoma for a study period spanning 1980–2020. Fifteen simulations are included in this data release: a simulation for the calibrated numerical groundwater-flow model, 9 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 the input and output files for the simulations described in the associated model documentation report (https://doi.org/10.3133/sir20255043).

A previously published MODFLOW 2005 groundwater model (https://doi.org/10.3133/sir20185136) of the Rush Springs aquifer was modified to assess the effects of groundwater withdrawals rates on spring discharge, streamflow, and groundwater availability pertaining to the Rush Springs aquifer in and near the Caddo Nation of Oklahoma Tribal jurisdictional area. Increases in industrial and public water supply needs have led to increased development of water resources within the Rush Springs aquifer. As new areas within the aquifer are developed, increased water withdrawals may result in decreases in available water resources and conflicts among water users. The Caddo Nation of Oklahoma is concerned about permitted water transfers from the Rush Springs aquifer in Caddo County to areas outside of this aquifer. The U.S. Geological Survey (USGS), in cooperation with the Caddo Nation of Oklahoma and Bureau of Indian Affairs, assessed four groundwater-withdrawal scenarios and their effects on the Rush Springs aquifer on the Caddo Nation of Oklahoma Tribal jurisdictional area. For the previously published calibrated model, groundwater flow was simulated from 1979 through 2015. In this study, groundwater flow simulations were extended through 2035. The period from 2016 through 2035 is referred to as the 20-year projections. The numerical model contains one steady-state stress period, 444 monthly transient stress periods and 20 annual stress periods. 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/sir20225044).

A previously published MODFLOW 2005 groundwater model (https://doi.org/10.3133/sir20185136) of the Rush Springs aquifer was modified to assess the effects of groundwater withdrawals rates on spring discharge, streamflow, and groundwater availability pertaining to the Rush Springs aquifer in and near the Caddo Nation of Oklahoma Tribal jurisdictional area. Increases in industrial and public water supply needs have led to increased development of water resources within the Rush Springs aquifer. As new areas within the aquifer are developed, increased water withdrawals may result in decreases in available water resources and conflicts among water users. The Caddo Nation of Oklahoma is concerned about permitted water transfers from the Rush Springs aquifer in Caddo County to areas outside of this aquifer. The U.S. Geological Survey (USGS), in cooperation with the Caddo Nation of Oklahoma and Bureau of Indian Affairs, assessed four groundwater-withdrawal scenarios and their effects on the Rush Springs aquifer on the Caddo Nation of Oklahoma Tribal jurisdictional area. For the previously published calibrated model, groundwater flow was simulated from 1979 through 2015. In this study, groundwater flow simulations were extended through 2035. The period from 2016 through 2035 is referred to as the 20-year projections. The numerical model contains one steady-state stress period, 444 monthly transient stress periods and 20 annual stress periods. 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/sir20225044).