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 The Northern High Plains aquifer is generally unconfined; most of the water withdrawn from the aquifer is used for irrigation.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.

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 groundwater flow model (https://doi.org/10.3133/sir20185035) was modified and used as the primary tool to assess groundwater availability in the Ozark Plateaus aquifer system which is an important source for municipal, industrial, agricultural, and domestic water supply needs across much of southern Missouri and northern Arkansas, and smaller areas of southeastern Kansas and northeastern Oklahoma. The new model was developed to access changes in simulated hydrologic budget components at the regional scale to quantify hydrologic changes across the Ozark system. The model benefits current and future investigations that involve groundwater-withdrawal scenarios, optimization, particle transport, and monitoring network analysis. Recent short-term drought conditions have emphasized the need to better understand the delicate balance between abundance, sustainability and scarcity. The model also is critical to the ongoing work to quantify groundwater availability in the Ozark aquifer system. The groundwater model simulated 116 years (1900—2016) of historical hydrologic conditions, 45 years (2016-2060) of potential future hydrologic conditions, and the response of the groundwater system to changes in stress. Stress applied to the groundwater system included changes in recharge and increased groundwater withdrawals for water supply. Semi-seasonal stress periods were simulated from the later part of 1991 through 2060 to represent higher demand and lower recharge in the spring and summer months, and lower demand and higher recharge in the fall and winter months. Three scenarios were developed to simulate potential future conditions and assess the potential effects on the hydrologic system and availability of water resources. For each scenario, changes in water levels and hydrologic budget components were evaluated from predevelopment (1900) to present (2016), and 44 years into the future (2060). This USGS data release contains all of the input and output files for the model and the calibration and scenario simulations described in the associated professional paper (https://doi.org/10.3133/pp1854). This data release also includes (1) MODFLOW-NWT (v. 1.1.2) source code, (2) PEST++ source code, and (3) processing Python scripts and associated instruction files for parameter estimation and model calibration using PEST++.

A previously developed groundwater flow model (https://doi.org/10.3133/sir20185035) was modified and used as the primary tool to assess groundwater availability in the Ozark Plateaus aquifer system which is an important source for municipal, industrial, agricultural, and domestic water supply needs across much of southern Missouri and northern Arkansas, and smaller areas of southeastern Kansas and northeastern Oklahoma. The new model was developed to access changes in simulated hydrologic budget components at the regional scale to quantify hydrologic changes across the Ozark system. The model benefits current and future investigations that involve groundwater-withdrawal scenarios, optimization, particle transport, and monitoring network analysis. Recent short-term drought conditions have emphasized the need to better understand the delicate balance between abundance, sustainability and scarcity. The model also is critical to the ongoing work to quantify groundwater availability in the Ozark aquifer system. The groundwater model simulated 116 years (1900—2016) of historical hydrologic conditions, 45 years (2016-2060) of potential future hydrologic conditions, and the response of the groundwater system to changes in stress. Stress applied to the groundwater system included changes in recharge and increased groundwater withdrawals for water supply. Semi-seasonal stress periods were simulated from the later part of 1991 through 2060 to represent higher demand and lower recharge in the spring and summer months, and lower demand and higher recharge in the fall and winter months. Three scenarios were developed to simulate potential future conditions and assess the potential effects on the hydrologic system and availability of water resources. For each scenario, changes in water levels and hydrologic budget components were evaluated from predevelopment (1900) to present (2016), and 44 years into the future (2060). This USGS data release contains all of the input and output files for the model and the calibration and scenario simulations described in the associated professional paper (https://doi.org/10.3133/pp1854). This data release also includes (1) MODFLOW-NWT (v. 1.1.2) source code, (2) PEST++ source code, and (3) processing Python scripts and associated instruction files for parameter estimation and model calibration using PEST++.

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) refined the spatial and temporal discretization of a previously modeled area (Phase 1: https://pubs.usgs.gov/sir/2008/5143/ and Phase 2: https://pubs.usgs.gov/sir/2010/5149/) which focused on a 30,000-square-mile area of the High Plains aquifer. Regional groundwater-flow models were constructed to evaluate the effects of groundwater withdrawal on stream base flow in the Elkhorn and Loup River Basins, Nebraska. The model was calibrated to match groundwater level and base-flow data from the stream-aquifer system during the pre-1940 through 2010 period (including predevelopment [pre-1895], early development [1895–1940], and historical development [1940 through 2010] conditions) using an automated parameter- estimation method. The calibrated model was then used to simulate hypothetical development conditions (2011 through 2060). To assess the impact of wells on aquifer depletions, additional wells were simulated throughout the model domain and pumped for 50 years. The percentage of each well’s withdrawal after 50 years, which was compensated by aquifer reductions to stream base flow, storage, or evapotranspiration, was computed and mapped. This data release also includes the MODFLOW-NWT (version 1.0.7) 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/sir20185106).

Groundwater in the Ozark Plateaus aquifer system is an important source for municipal, industrial, agricultural, and domestic water supply needs across much of southern Missouri and northern Arkansas, and smaller areas of southeastern Kansas and northeastern Oklahoma. Recent short-term drought conditions have emphasized the need to better understand the delicate balance between abundance, sustainability and scarcity. A groundwater flow model was developed as the primary tool to assess groundwater availability in the aquifer system. The model was developed to benefit current and future investigations that involve groundwater-withdrawal scenarios, optimization, particle transport, and monitoring network analysis. The model is also critical to the ongoing work to quantify groundwater availability in the Ozark aquifer system. The groundwater model simulated 116 years (1900—2016) of hydrologic conditions and the response of the groundwater system to changes in stress. Stress applied to the groundwater system included changes in recharge and increased groundwater withdrawals for water supply. Semi-seasonal stress periods were simulated from the later part of 1991 to 2016 to represent higher demand and lower recharge in the spring and summer months, and lower demand and higher recharge in the fall and winter months. Groundwater pumping increased throughout the simulation period, with a maximum rate of about 600 million gallons per day (Mgal/d). History matching for the Ozark aquifer system model was accomplished by a combination of manual changes to parameter values and automated calibration methods. Observation data used in the development and evaluation of the model included 19,045 hydraulic-head observations from 6,683 wells within the Ozark model area that were weighted for use in the parameter estimation software. Observation data also included stream leakage estimates summed to calculate a net gain or net loss value for each stream. The majority, but not all, of the recharge component was discharged through streams simulated in the model. The total simulated discharge to streams fluctuates seasonally between 7,500 and 17,500 Mgal/d with a mean outflow of 11,500 Mgal/d. Much of the remaining balance between modeled recharge inflows and stream outflows was made up by water moving into or out of storage in the aquifer system resulting in changes in modeled groundwater levels. This USGS data release contains all of the input and output files for the model and calibration simulation described in the associated model documentation report (https://doi.org/10.3133/sir20185035). This data release also includes (1) MODFLOW-NWT (v. 1.1.2) source code, (2) PEST++ source code, and (3) processing Python scripts and associated instruction files for parameter estimation and model calibration using PEST++.