This data release contains environmental tracer model inputs, outputs, and model results. Dataset includes environmental tracer concentrations, simulated recharge conditions (water temperature, excess air), and estimated groundwater residence times. This dataset supports an integrated hydrologic investigation of groundwater recharge processes and groundwater flow in the Wet Mountain Valley alluvial aquifer, Custer and Fremont Counties, Colorado. Data were collected by the U.S. Geological Survey in cooperation with the Upper Arkansas Water Conservancy District.

The U.S. Geological Survey in cooperation with the Upper Arkansas Water Conservancy District, created a numerical groundwater-flow model for the Wet Mountain Valley alluvial aquifer using the finite-difference MODFLOW code with the Newton formulation solver. This numerical groundwater-flow model simulates water-budget components, groundwater and surface-water interactions, and evaluates the potential effects of aquifer storage and recovery through an added recharge simulation. The numerical model was spatially discretized into two layers with 261 rows and 133 columns of square cells at 250 meters on each side, for a total of 20,007 active cells. The model was rotated by 36 degrees to the northwest to align with the orientation of the valley and the assumed groundwater-flow directions. The numerical model was temporally discretized into 241 stress periods. The first stress period simulates a mean steady-state period, and the subsequent 240 stress periods were transient and simulate each month from 2000 to 2019. This U.S. Geological Survey data release includes all of the necessary files to simulate the Wet Mountain Valley alluvial aquifer and potential flow paths within it as described in the associated Scientific Investigations Report (https://doi.org/10.3133/sir20245105).

The U.S. Geological Survey in cooperation with the Upper Arkansas Water Conservancy District, created a numerical groundwater-flow model for the Wet Mountain Valley alluvial aquifer using the finite-difference MODFLOW code with the Newton formulation solver. This numerical groundwater-flow model simulates water-budget components, groundwater and surface-water interactions, and evaluates the potential effects of aquifer storage and recovery through an added recharge simulation. The numerical model was spatially discretized into two layers with 261 rows and 133 columns of square cells at 250 meters on each side, for a total of 20,007 active cells. The model was rotated by 36 degrees to the northwest to align with the orientation of the valley and the assumed groundwater-flow directions. The numerical model was temporally discretized into 241 stress periods. The first stress period simulates a mean steady-state period, and the subsequent 240 stress periods were transient and simulate each month from 2000 to 2019. This U.S. Geological Survey data release includes all of the necessary files to simulate the Wet Mountain Valley alluvial aquifer and potential flow paths within it as described in the associated Scientific Investigations Report (https://doi.org/10.3133/sir20245105).

This data release contains environmental tracer concentrations, modeled recharge conditions (water temperature, excess air), and resulting estimated groundwater residence times. This dataset supports an integrated hydrogeochemical investigation of solute sources, groundwater recharge processes, and groundwater flow in the Fountain Creek alluvial aquifer. The data release contains five comma separated value (CSV) files. The CSV files contain the model inputs (gas and tracer concentrations) and the model outputs (simulated recharge temperature, excess air, apparent groundwater age, and mean groundwater residence time). Data were collected in cooperation with the U.S. Air Force Civil Engineering Center.

This data release contains environmental tracer concentrations, modeled recharge conditions (water temperature, excess air), and resulting estimated groundwater residence times. This dataset supports an integrated hydrogeochemical investigation of solute sources, groundwater recharge processes, and groundwater flow in the Fountain Creek alluvial aquifer. The data release contains five comma separated value (CSV) files. The CSV files contain the model inputs (gas and tracer concentrations) and the model outputs (simulated recharge temperature, excess air, apparent groundwater age, and mean groundwater residence time). Data were collected in cooperation with the U.S. Air Force Civil Engineering Center.

The U.S. Geological Survey (USGS), in cooperation with the Air Force Civil Engineering Center, created a numerical groundwater-flow model for the Fountain Creek alluvial aquifer using the finite-difference MODFLOW code with the Newton formulation solver. This numerical groundwater-flow model simulates water-budget components, groundwater-flow directions, and groundwater-flow paths of the Fountain Creek alluvial aquifer. The numerical model was spatially discretized into a single layer with 291 rows and 254 columns of 200 by 200 feet size, and a total of 17,610 active cell. The numerical model was temporally discretized into 1 initial steady-state stress period representing the average conditions of the 240 monthly transient stress periods from 2000 to 2019. This USGS data release includes all the necessary files to simulate the Fountain Creek alluvial aquifer and potential flow paths within it as described in the associated USGS Scientific Investigations Report (https://doi.org/10.3133/sir20235119).

The U.S. Geological Survey (USGS), in cooperation with the Air Force Civil Engineering Center, created a numerical groundwater-flow model for the Fountain Creek alluvial aquifer using the finite-difference MODFLOW code with the Newton formulation solver. This numerical groundwater-flow model simulates water-budget components, groundwater-flow directions, and groundwater-flow paths of the Fountain Creek alluvial aquifer. The numerical model was spatially discretized into a single layer with 291 rows and 254 columns of 200 by 200 feet size, and a total of 17,610 active cell. The numerical model was temporally discretized into 1 initial steady-state stress period representing the average conditions of the 240 monthly transient stress periods from 2000 to 2019. This USGS data release includes all the necessary files to simulate the Fountain Creek alluvial aquifer and potential flow paths within it as described in the associated USGS Scientific Investigations Report (https://doi.org/10.3133/sir20235119).

This dataset was created in support of a study focusing on ground-water resources in the Great Basin carbonate and alluvial aquifer system (GBCAAS). The GBCAAS is a complex aquifer system comprised of both unconsolidated and bedrock formations covering an area of approximately 110,000 square miles. The aquifer system is situated in the eastern portion of the Great Basin Province of the western United States. The eastern Great Basin is experiencing rapid population growth and has some of the highest per capita water use in the Nation. These factors, combined with the arid setting, have levied intensive demand upon current ground-water resources and, thus, predictions of future shortages. Because of the large regional extent of the aquifer system, rapid growth in the region, and the reliance upon ground water for urban populations, agriculture, and native habitats, the GBCAAS was selected by the U.S. Geological Survey (USGS) Water Resources program as part of the National Water Census Initiative to evaluate the Nation's ground-water availability. These data are derived from the Basin Characterization Model (BCM). The BCM is a distributed-parameter, water-balance accounting model that is run on a monthly time step. The BCM incorporates spatially distributed parameters (monthly precipitation, monthly minimum and maximum air temperature, monthly potential evapotranspiration, soil-water storage capacity, and saturated hydraulic conductivity of bedrock and alluvium) to determine where excess water is available in a basin and whether the excess water is stored in the soil or infiltrates downward into underlying bedrock. This dataset is composed of three raster layers. Two of the layers are outputs of the BCM model, one is an input. The layers are as follows: 1. Estimated average in-place recharge for the years 1940 to 2006 in the GBCAAS study area. In-place recharge is output from the BCM and is calculated as the annual mean amount of water that can drain from the soil zone directly into consolidated bedrock or unconsolidated deposits. 2. Estimated average runoff for the years 1940 to 2006 in the GBCAAS study area. Estimated runoff is output from the BCM and is calculated as the annual mean amount of water that runs off the mountain front or becomes streamflow. 3. Estimated saturated hydraulic conductivity (K) of bedrock and unconsolidated basin fill in the GBCAAS study area. The data are input to the BCM model as one of two temporally invariable inputs: storage capacity of soil and saturated hydraulic conductivity (Flint and Flint, 2007). The dataset was developed by applying assumed K values to geologic formations derived from 1:500,000-scale and 1:750,000-scale digital State geologic maps covering the study area. Hydraulic conductivity estimates of bedrock are uncertain because of the unknown hydraulic properties and spatial distributions of fractures, faults, fault gouge, and shallow infilling materials associated with different bedrock types and evaporative demand. These data are output from a model and should be used with caution. Refer to the larger work citation for details about the data and adjustments made to estimated recharge and runoff in water balance calculations made for the GBCAAS study. References cited: Flint, A.L., and Flint, L.E., 2007, Application of the Basin Characterization Model to estimate in-place recharge and runoff potential in the Basin and Range carbonate-rock aquifer system, White Pine County, Nevada and adjacent areas in Nevada and Utah: U.S. Geological Survey Scientific Investigations Report 2007-5099, 30p.

This dataset was created in support of a study focusing on ground-water resources in the Great Basin carbonate and alluvial aquifer system (GBCAAS). The GBCAAS is a complex aquifer system comprised of both unconsolidated and bedrock formations covering an area of approximately 110,000 square miles. The aquifer system is situated in the eastern portion of the Great Basin Province of the western United States. The eastern Great Basin is experiencing rapid population growth and has some of the highest per capita water use in the Nation. These factors, combined with the arid setting, have levied intensive demand upon current ground-water resources and, thus, predictions of future shortages. Because of the large regional extent of the aquifer system, rapid growth in the region, and the reliance upon ground water for urban populations, agriculture, and native habitats, the GBCAAS was selected by the U.S. Geological Survey (USGS) Water Resources program as part of the National Water Census Initiative to evaluate the Nation's ground-water availability. These data are derived from the Basin Characterization Model (BCM). The BCM is a distributed-parameter, water-balance accounting model that is run on a monthly time step. The BCM incorporates spatially distributed parameters (monthly precipitation, monthly minimum and maximum air temperature, monthly potential evapotranspiration, soil-water storage capacity, and saturated hydraulic conductivity of bedrock and alluvium) to determine where excess water is available in a basin and whether the excess water is stored in the soil or infiltrates downward into underlying bedrock. This dataset is composed of three raster layers. Two of the layers are outputs of the BCM model, one is an input. The layers are as follows: 1. Estimated average in-place recharge for the years 1940 to 2006 in the GBCAAS study area. In-place recharge is output from the BCM and is calculated as the annual mean amount of water that can drain from the soil zone directly into consolidated bedrock or unconsolidated deposits. 2. Estimated average runoff for the years 1940 to 2006 in the GBCAAS study area. Estimated runoff is output from the BCM and is calculated as the annual mean amount of water that runs off the mountain front or becomes streamflow. 3. Estimated saturated hydraulic conductivity (K) of bedrock and unconsolidated basin fill in the GBCAAS study area. The data are input to the BCM model as one of two temporally invariable inputs: storage capacity of soil and saturated hydraulic conductivity (Flint and Flint, 2007). The dataset was developed by applying assumed K values to geologic formations derived from 1:500,000-scale and 1:750,000-scale digital State geologic maps covering the study area. Hydraulic conductivity estimates of bedrock are uncertain because of the unknown hydraulic properties and spatial distributions of fractures, faults, fault gouge, and shallow infilling materials associated with different bedrock types and evaporative demand. These data are output from a model and should be used with caution. Refer to the larger work citation for details about the data and adjustments made to estimated recharge and runoff in water balance calculations made for the GBCAAS study. References cited: Flint, A.L., and Flint, L.E., 2007, Application of the Basin Characterization Model to estimate in-place recharge and runoff potential in the Basin and Range carbonate-rock aquifer system, White Pine County, Nevada and adjacent areas in Nevada and Utah: U.S. Geological Survey Scientific Investigations Report 2007-5099, 30p.

A new version of previously published steady-state numerical groundwater flow models of the Great Basin carbonate and alluvial aquifer system (GBCAAS), and was developed in conjunction with U.S. Geological Survey (USGS) studies in Parowan, Pine, and Wah Wah Valleys, Utah. This version of the model is considered to be GBCAAS v. 3.0 and supersedes previous versions. This model added 15 transient calibration stress periods and 14 projection stress periods, aquifer storage properties, historical withdrawals in Parowan Valley, and observations of water-level changes in Parowan Valley to the previous steady-state versions. Recharge in Parowan Valley and withdrawal from wells in Parowan Valley and two nearby wells in Cedar City Valley vary for each calibration stress period representing conditions from March 1940 to November 2013. Stresses, including recharge, are the same in each stress period as in the steady-state stress period for all areas outside of Parowan Valley. This data release contains one calibration simulation and one projection simulation. The model is calibrated to transient conditions only in Parowan Valley. Simulated storage properties outside of Parowan Valley are set the same as the Parowan Valley properties and should not be considered calibrated. The projection simulation was used to estimate that reducing withdrawals in Parowan Valley from 35,000 to about 22,000 acre-feet per year should stabilize groundwater levels in the valley if recharge varies as it did from about 1950 to 2012 and that withdrawals of 15,000 acre-feet per year from Pine Valley and 6,500 acre-feet per year from Wah Wah Valley could ultimately (long-term steady-state) cause water-level declines of about 1,900 feet near the withdrawal wells and more than 5 feet over about 10,500 square miles. 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/sir20175072). This data release also contains source code needed to run the models. Model files presented in this data release were modified from an existing, calibrated, steady-state model of the Great Basin carbonate and alluvial aquifer system. SIR 2014-5213 (https://pubs.usgs.gov/sir/2014/5213/) and SIR 2017-5011 (https://doi.org/10.3133/sir20175011) document the construction and calibration of the previous versions of this model. Modifications that were made to the input files and discussion of model results are documented in SIR2017-5072 (https://doi.org/10.3133/sir20175072), which is associated with this data release. The model consists of a parent and a child model and must be run using MODFLOW-LGR. The child model is far removed from the area considered for this project, but is being kept with the model so that one model version exists of the Great Basin carbonate and alluvial aquifer system that incorporates all refinements and improvements. The model files documented in this data release should be used instead of previous versions.