Data Release for Secondary Hydrogeologic Regions of the Conterminous United States (ver. 2.0, June 2022)
The U.S. Geological Survey (USGS) previously identified 62 Principal Aquifers (PAs) in the U.S., with 57 located in the conterminous states.  The USGS characterized areas outside of PAs as “other rocks;” other rocks account for about 40% of the area of the conterminous states. This paper subdivides the large area …