MODFLOW2000 model used to simulate the groundwater flow of the Denver Basin Aquifer System, Colorado

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).