A three-dimensional, finite-difference MODFLOW 2005 groundwater model using the Newton formulation solver (MODFLOW-NWT) was created for the Cimarron River alluvial aquifer in Payne County, north-central Oklahoma to assess the impacts of current groundwater withdrawal rates with respect to current and future groundwater availability and the impacts to baseflow to the Cimarron River. To better understand current (2021) water resources and possible future water availability in the Pawnee Nation Tribal jurisdictional area, the U.S. Geological Survey, in cooperation with the Bureau of Indian Affairs and the Pawnee Nation of Oklahoma, compiled available hydrogeologic data and developed conceptual and numerical groundwater-flow models. The numerical model consists of a single layer representing alluvium and terrace deposits within the alluvial aquifer model area. The calibrated model contains one steady-state stress period and 24 monthly, transient stress periods for 2016-17. Streamflow-capture analysis was applied to the steady-state simulation to identify areas of the aquifer where base flows in the Cimarron River were most sensitive to groundwater withdrawals. 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/sir20215073).

A previously calibrated MODFLOW-NWT groundwater-flow model (https://doi.org/10.3133/sir20205118) was used to determine the effects of climate variability under a range of future climatic conditions on groundwater resources in the reach 1 of the Washita River alluvial aquifer in western Oklahoma. The study area focuses on reach 1 of the Washita River alluvial aquifer; the entire Washita River alluvial aquifer consists of four administrative sections, or reaches, that are designated as reaches 1–4 by the Oklahoma Water Resources Board (OWRB, 2012). To approximate a range in future base-flow conditions in reach 1 of the Washita River alluvial aquifer and base-flow into Foss Reservoir, the Coupled Model Intercomparison Project Phase 5 Global Climate Model climate data were downscaled to watershed scale using monthly Bias-Correction Spatial Disaggregation techniques. A time series of scaling factors was developed and spatially interpolated for three climate scenarios (central tendency, warmer/drier, and less warm-wetter) representing a range of future climate conditions for the period 2050–2079. These scaling factors were then applied to an existing soil-water-balance model (https://doi.org/10.3133/sir20205118) with climate data for the baseline period 1985–2014 to produce recharge and evapotranspiration estimations for this future period. The downscaled climate data were applied to the groundwater-flow model of the reach 1 of the Washita River alluvial aquifer using MODFLOW-NWT. This data release contains the input and output files for the scenarios described in the associated model documentation report (https://doi.org/10.3133/sir20245082).

A previously calibrated MODFLOW-NWT groundwater-flow model (https://doi.org/10.3133/sir20205118) was used to determine the effects of climate variability under a range of future climatic conditions on groundwater resources in the reach 1 of the Washita River alluvial aquifer in western Oklahoma. The study area focuses on reach 1 of the Washita River alluvial aquifer; the entire Washita River alluvial aquifer consists of four administrative sections, or reaches, that are designated as reaches 1–4 by the Oklahoma Water Resources Board (OWRB, 2012). To approximate a range in future base-flow conditions in reach 1 of the Washita River alluvial aquifer and base-flow into Foss Reservoir, the Coupled Model Intercomparison Project Phase 5 Global Climate Model climate data were downscaled to watershed scale using monthly Bias-Correction Spatial Disaggregation techniques. A time series of scaling factors was developed and spatially interpolated for three climate scenarios (central tendency, warmer/drier, and less warm-wetter) representing a range of future climate conditions for the period 2050–2079. These scaling factors were then applied to an existing soil-water-balance model (https://doi.org/10.3133/sir20205118) with climate data for the baseline period 1985–2014 to produce recharge and evapotranspiration estimations for this future period. The downscaled climate data were applied to the groundwater-flow model of the reach 1 of the Washita River alluvial aquifer using MODFLOW-NWT. This data release contains the input and output files for the scenarios described in the associated model documentation report (https://doi.org/10.3133/sir20245082).

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).

The U.S. Geological Survey constructed a steady-state numerical groundwater flow model in cooperation with Des Moines Water Works (DMWW) to simulate groundwater flow conditions in the Des Moines River alluvial aquifer (DMRA) during winter low-flow conditions typical of December 2018-2020. The Des Moines River alluvial aquifer (DMRA) is an important source of water for Des Moines Water Works (DMWW), the municipal water utility that serves residential and commercial water needs in the city of Des Moines, Iowa and surrounding municipalities. A comprehensive understanding of groundwater flow processes in the DMRA is needed for DMWW to make decisions related to the management of this water resource. A three-layered model was constructed using MODFLOW-NWT to simulate an area of about 15 square kilometers near Prospect Park in Des Moines, Iowa. The model has 130 rows and 130 columns of cells within the model boundary. Parameter ESTimation software (PEST) was used for model calibration to assess and optimize performance of individual parameters including the horizontal and vertical hydraulic conductivity of the various units, evapotranspiration rate, and recharge rate. 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/ofr20211110).

The U.S. Geological Survey constructed a steady-state numerical groundwater flow model in cooperation with Des Moines Water Works (DMWW) to simulate groundwater flow conditions in the Des Moines River alluvial aquifer (DMRA) during winter low-flow conditions typical of December 2018-2020. The Des Moines River alluvial aquifer (DMRA) is an important source of water for Des Moines Water Works (DMWW), the municipal water utility that serves residential and commercial water needs in the city of Des Moines, Iowa and surrounding municipalities. A comprehensive understanding of groundwater flow processes in the DMRA is needed for DMWW to make decisions related to the management of this water resource. A three-layered model was constructed using MODFLOW-NWT to simulate an area of about 15 square kilometers near Prospect Park in Des Moines, Iowa. The model has 130 rows and 130 columns of cells within the model boundary. Parameter ESTimation software (PEST) was used for model calibration to assess and optimize performance of individual parameters including the horizontal and vertical hydraulic conductivity of the various units, evapotranspiration rate, and recharge rate. 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/ofr20211110).

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).

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).

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).