This dataset consists of altitude values representing the top surface (in feet) of well-consolidated bedrock at the base of the shallow groundwater system in the Lower Gunnison River Basin in Delta, Montrose, Ouray, and Gunnison Counties, Colorado. Bedrock-altitude values were computed as the difference between land-surface altitude and the thickness of regolith sediments represented by dataset rglth. The U.S. Geological Survey prepared this dataset in cooperation with the Colorado Water Conservation Board.