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).

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 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.

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.

U.S. Geological Survey (USGS) in cooperation with the U.S. Air Force Civil Engineering Center conducted short-term aquifer tests at 11 wells to estimate hydraulic properties in the Fountain Creek alluvial aquifer, in El Paso County, Colorado. Data were collected in July 2019 over three days. Single-hole pumping and recovery tests were completed at five wells, and multiple single-hole displacement (solid slug) tests were conducted at all 11 wells. This data release contains water-level data collected at various time intervals (0.25 seconds, 0.5 seconds, and variable during a manual test with a stopwatch) and well-discharge rates for the aquifer tests in comma separated value (CSV) files for the 34 tests analyzed. All water-level displacement data for a given well are provided in a single CSV file for the well. Data are further categorized by the type of aquifer test used for data collection (slug or pumping). Well logs, graphs of the test data, and plots of analytical solutions are included in file, “FCAA_aquifer_testing_description_plots_vFINAL.pdf.”

U.S. Geological Survey (USGS) in cooperation with the U.S. Air Force Civil Engineering Center conducted short-term aquifer tests at 11 wells to estimate hydraulic properties in the Fountain Creek alluvial aquifer, in El Paso County, Colorado. Data were collected in July 2019 over three days. Single-hole pumping and recovery tests were completed at five wells, and multiple single-hole displacement (solid slug) tests were conducted at all 11 wells. This data release contains water-level data collected at various time intervals (0.25 seconds, 0.5 seconds, and variable during a manual test with a stopwatch) and well-discharge rates for the aquifer tests in comma separated value (CSV) files for the 34 tests analyzed. All water-level displacement data for a given well are provided in a single CSV file for the well. Data are further categorized by the type of aquifer test used for data collection (slug or pumping). Well logs, graphs of the test data, and plots of analytical solutions are included in file, “FCAA_aquifer_testing_description_plots_vFINAL.pdf.”

Co-developed surface and subsurface hydrologic models for the Upper Colorado River Basin and the Colorado Plateaus principal aquifer system were used to investigate the drivers of change in hydrologic water budget components during contrasting recent wet (1982–1999) and drought (2000–2022) periods in select headwater subregions of the Upper Colorado River Basin. The hydrologic system was simulated with separate model codes to represent watershed and groundwater hydrology. A Precipitation-Runoff Modeling System (PRMS) model was used to simulate surface and near-surface watershed hydrology of the model area from the plant canopy to the lower limit of the soil zone. A MODFLOW-NWT model was used to simulate streamflow, surface-water/groundwater interactions, and three-dimensional saturated groundwater hydrology. Outputs of recharge, surface runoff, and interflow from the PRMS model were used as inputs to the MODFLOW-NWT model. This data release details the development of these models and contains the model input and output files for each of the models for the simulations described in Tillman and others, 2025 (https://doi.org/10.1016/j.ejrh.2025.102554). This page includes the file 'modelgeoref.txt' that describes the projection, datum, and coordinates of the four corners of the model grid (common to both models) in decimal degrees. The two child items,' Upper Colorado River Basin MODFLOW-NWT Model Application Data', and 'Upper Colorado River Basin Precipitation-Runoff Modeling System (PRMS) Model Application Data' contain the input and output files for each model, descriptions of the model files, and instructions for running the models.