Short-term aquifer tests were conducted to estimate hydraulic properties in an alluvial aquifer. Tests included eight single-hole pumping and recovery tests and three slug tests (in a single well). These investigations were conducted in the Wet Mountain Valley, in Custer and Fremont Counties, Colorado. The U.S. Geological Survey (USGS) conducted aquifer tests in May, 2019. These aquifer tests inform the conceptual understanding of the valley-fill aquifer and serve as primary inputs to the numerical groundwater-flow model. Testing was completed in cooperation with the Upper Arkansas Water Conservancy District. This data release contains raw data from aquifer tests, water-level and pumping discharge rate measurements, well logs, graphs of the testing data, and plots of analytical solutions.