MODFLOW2000 model and ZONEBUDGET computer program used to simulate the Upper Big Sandy Designated Groundwater Basin alluvial aquifer, Elbert, El Paso, and Lincoln Counties, Colorado, 2016

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 USGS 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/sir2018xxxx).