A three-dimensional groundwater flow model (MODFLOW2000) of the Denver Basin bedrock aquifer system and overlying alluvial aquifer was developed to provide quantitative estimates of groundwater flow conditions and provide a useful tool for managers to analyze temporal changes to the hydrologic system in response to changing climatic conditions and future groundwater development. In 2004, the U.S. Geological Survey (USGS) initiated large-scale regional studies to provide updated assessments of groundwater availability in important principal aquifers across the United States, including the Denver Basin. The Denver Basin groundwater flow model includes several enhancements over previous modeling efforts because of the availability of additional data, improved modeling capabilities, and advanced computer technology. Additional data available include updated geologic mapping, additional geophysical logs, water-level, streamflow, precipitation, and irrigation data collected since previous studies; and updated estimates of pumping from Denver Basin bedrock and alluvial aquifers. Modeling capabilities and computer technology also have advanced such that additional features, hydrologic processes, and numerical techniques are included in the current model that were not possible in previous models. The Denver Basin groundwater flow model represents regional time-varying (transient) conditions prior to 1880 through 2003. The model was calibrated by primarily adjusting hydraulic conductivity and recharge parameters until a best fit was obtained between observed and simulated transient hydraulic heads and flows using PEST. The calibrated model was used to estimate the hydrologic system response to two pumping scenarios for the period 2004 through 2053. This USGS data release contains all of the input and output files for the simulation and calibration described in the associated model documentation report (https://pubs.er.usgs.gov/publication/pp1770).

The previously developed three-dimensional groundwater flow model (MODFLOW2000) of the Denver Basin bedrock aquifer system and overlying alluvial aquifer (https://pubs.er.usgs.gov/publication/pp1770 and model archive https://doi.org/10.5066/F77W69PQ) was updated to provide quantitative estimates of groundwater flow conditions and provide a useful tool for managers to analyze temporal changes to the hydrologic system in response to changing climatic conditions and future groundwater development. The computer program ZONEBUDGET was used to calculate cell by cell water balances for the major components of the water budget for the Upper Big Sandy Designated Groundwater Basin alluvial aquifer. The original Denver Basin groundwater flow model was done as part of a large-scale regional groundwater availability study of the principal aquifers and represents regional time-varying (transient) conditions prior to 1880 through 2003. This model was updated to include updated well pumping data through 2016. This U.S. Geological Survey data release contains all of the input and output files for the simulation described in the associated model documentation report (https://doi.org/10.3133/sir20195049).

The previously developed three-dimensional groundwater flow model (MODFLOW2000) of the Denver Basin bedrock aquifer system and overlying alluvial aquifer (https://pubs.er.usgs.gov/publication/pp1770 and model archive https://doi.org/10.5066/F77W69PQ) was updated to provide quantitative estimates of groundwater flow conditions and provide a useful tool for managers to analyze temporal changes to the hydrologic system in response to changing climatic conditions and future groundwater development. The computer program ZONEBUDGET was used to calculate cell by cell water balances for the major components of the water budget for the Upper Big Sandy Designated Groundwater Basin alluvial aquifer. The original Denver Basin groundwater flow model was done as part of a large-scale regional groundwater availability study of the principal aquifers and represents regional time-varying (transient) conditions prior to 1880 through 2003. This model was updated to include updated well pumping data through 2016. This U.S. Geological Survey data release contains all of the input and output files for the simulation described in the associated model documentation report (https://doi.org/10.3133/sir20195049).

A three-dimensional groundwater flow model (MODFLOW200-FMP1_1) of the Central Valley in California was developed to aid water managers in understanding how water moves through the aquifer system, to predict water-supply scenarios, and to address issues related to water competition. The USGS Groundwater Resources Program made a detailed assessment of groundwater availability of the Central Valley aquifer system, which includes: (1) the present status of groundwater resources; (2) how these resources have changed over time; and (3) tools to assess system responses to stresses from future human uses and climate variability and change. This effort builds on previous investigations, such as the USGS Central Valley Regional Aquifer System and Analysis (CV-RASA) project and several other groundwater studies in the Valley completed by Federal, State and local agencies at differing scales. The principal product of this new assessment is a tool referred to as the Central Valley Hydrologic Model (CVHM) that accounts for integrated, variable water supply and demand, and simulates surface-water and groundwater-flow across the entire Central Valley system. The current model was extended to incorporate a slightly larger geographic area, has a finer spatial and temporal discretization, uses a more-detailed depiction of subsurface geology. In addition, the model utilizes a modified version of MODFLOW2000 (version 1.15.03) to include an updated and refined Farm Process (FMP1) to simulate groundwater and surface-water flow, irrigated agriculture, land subsidence, and other key processes in the Central Valley on a monthly basis for April 1961 through September 2003. This USGS data release contains all of the input and output files for the simulation and calibration of the CVHM described in the associated model documentation report (https://pubs.er.usgs.gov/publication/pp1766).

A three-dimensional groundwater flow model (MODFLOW200-FMP1_1) of the Central Valley in California was developed to aid water managers in understanding how water moves through the aquifer system, to predict water-supply scenarios, and to address issues related to water competition. The USGS Groundwater Resources Program made a detailed assessment of groundwater availability of the Central Valley aquifer system, which includes: (1) the present status of groundwater resources; (2) how these resources have changed over time; and (3) tools to assess system responses to stresses from future human uses and climate variability and change. This effort builds on previous investigations, such as the USGS Central Valley Regional Aquifer System and Analysis (CV-RASA) project and several other groundwater studies in the Valley completed by Federal, State and local agencies at differing scales. The principal product of this new assessment is a tool referred to as the Central Valley Hydrologic Model (CVHM) that accounts for integrated, variable water supply and demand, and simulates surface-water and groundwater-flow across the entire Central Valley system. The current model was extended to incorporate a slightly larger geographic area, has a finer spatial and temporal discretization, uses a more-detailed depiction of subsurface geology. In addition, the model utilizes a modified version of MODFLOW2000 (version 1.15.03) to include an updated and refined Farm Process (FMP1) to simulate groundwater and surface-water flow, irrigated agriculture, land subsidence, and other key processes in the Central Valley on a monthly basis for April 1961 through September 2003. This USGS data release contains all of the input and output files for the simulation and calibration of the CVHM described in the associated model documentation report (https://pubs.er.usgs.gov/publication/pp1766).

In 2018 The U.S. Geological Survey, in cooperation with the U.S. Bureau of Reclamation and 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 Rush Springs aquifer in western 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 evaluate the maximum annual yield of groundwater from the Rush Springs aquifer in Oklahoma. 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 conceptual model was necessary to provide 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 Rush Springs 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 Rush Springs aquifer had 1,362 rows, 1,083 columns, about 554,000 active cells of 500 by 500 ft, and 3 convertible layers. The top layer (layer 1) represented the Permian-age Cloud Chief Formation. The Rush Springs aquifer is composed of Permian-age Whitehorse Group. The second layer (layer 2) represented the undifferentiated Quaternary-age alluvium and terrace deposits, as well as the upper 30 ft of the Whitehorse Group. The bottom layer (layer 3) represented the remainder of the Rush Springs Formation. The model active area was modified from Neel and others (2018). The numerical model was temporally discretized into 444 monthly transient stress periods representing the period 1979-2015. 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/sir20185136)

In 2018 The U.S. Geological Survey, in cooperation with the U.S. Bureau of Reclamation and 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 Rush Springs aquifer in western 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 evaluate the maximum annual yield of groundwater from the Rush Springs aquifer in Oklahoma. 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 conceptual model was necessary to provide 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 Rush Springs 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 Rush Springs aquifer had 1,362 rows, 1,083 columns, about 554,000 active cells of 500 by 500 ft, and 3 convertible layers. The top layer (layer 1) represented the Permian-age Cloud Chief Formation. The Rush Springs aquifer is composed of Permian-age Whitehorse Group. The second layer (layer 2) represented the undifferentiated Quaternary-age alluvium and terrace deposits, as well as the upper 30 ft of the Whitehorse Group. The bottom layer (layer 3) represented the remainder of the Rush Springs Formation. The model active area was modified from Neel and others (2018). The numerical model was temporally discretized into 444 monthly transient stress periods representing the period 1979-2015. 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/sir20185136)

This data release contains a three-dimensional groundwater flow model with example applications using MODFLOW-2000. The calibrated model is able to simulate observed decadal-scale climate-driven fluctuations in the groundwater system as well as observed shorter-term pumping-related fluctuations. Example model simulations show that the timing and location of the effects of groundwater pumping vary markedly depending on the pumping location. The complete description for the models in Gannett et al., 2012.

This data release contains a three-dimensional groundwater flow model with example applications using MODFLOW-2000. The calibrated model is able to simulate observed decadal-scale climate-driven fluctuations in the groundwater system as well as observed shorter-term pumping-related fluctuations. Example model simulations show that the timing and location of the effects of groundwater pumping vary markedly depending on the pumping location. The complete description for the models in Gannett et al., 2012.

This model archive provides the necessary documentation of the numerical models developed for the Central Sands Lake study in central Wisconsin and will be included as a technical appendix (Appendix C) in the report to the Wisconsin State Legislature by the Wisconsin Department of Natural Resources (WDNR) in response to 2017 Wisconsin Act 10. This legislation directed DNR to determine whether existing and potential groundwater withdrawals are causing or are likely to cause significant reduction of mean seasonal water levels at Pleasant Lake, Long Lake, and Plainfield Lake (s. 281.34(7m)(2)(b), Wis. Stats.) in Waushara County, Wisconsin. To evaluate the potential hydrologic connection between groundwater withdrawals and the nearby study lakes, hydrologic models were created that focused on the lakes of interest and yet were large enough to cover a broad enough region to extend to the major hydrologic boundaries of the natural flow system. The areas near the lakes require finer-scale grid discretization (or spacing) to better represent the lakes and streams in the model, but also need to cover a large enough area to include the groundwater withdrawal locations that have the potential to cause reduction in water levels in the lakes. To accomplish these goals, three groundwater models were created: a regional model extending to major hydrologic boundaries; and two inset models, inheriting boundaries from the regional model but focused near the lakes. Each of the inset models, in turn, included a detailed area close to the lakes surrounded by an area at the same spatial scale as the regional model. To support WDNR in evaluating the connection between groundwater withdrawals and lake levels, a representative time period was required over which to compare land use with and without irrigated agriculture and for WDNR to evaluate potential lake stage and flux changes related to irrigated agriculture. WDNR chose the climate period of 1981-2018 to be representative of a typical period and provided two land use scenarios—one with no irrigated agriculture and one with assumed crop rotations similar to current conditions—to simulate with groundwater models to, then, compare lake responses with. As a result, simulations over this climate record are not intended to recreate the history of 1981-2018 because land use changed over that time. These runs are, instead, intended to provide a basis on which to compare land use with and without irrigation-related groundwater withdrawals based on the current arrangement of land use and a varied climatic record. Groundwater withdrawals focused on irrigated-agriculture-related water use because greater than 95% of groundwater withdrawal in the two inset models around the study lakes is for irrigated agriculture water use. The period of 2012-2018 was used for parameter estimation (synonymously referred to as “history matching”) for the groundwater models. This time period was chosen because it includes the most complete water use records to simulate groundwater withdrawals. History matching was performed using groundwater elevations, lake stages, and streamflow observations over the 2012-2018 time period and processed observations derived from those raw data. Climatic data were incorporated into the model using a soil-water balance approach. A soil water balance model (Westenbroek and others, 2021) was constructed at the scale of the regional groundwater model to both calculate recharge based on land use and climate, and in the long-term climate-period runs, to estimate water use required by irrigated agriculture to apply as well boundary conditions in the groundwater model in the absence of reported water use values over that period. The model archive presents all the inputs needed to run the models, the model software, information on history matching to estimate parameters of the model, model scenario files, and model outputs that the user should be able to recreate using the model files in this archive.