What's under your address?
Enter an address and we'll place it on the USGS Principal Aquifers map: which aquifer you sit over, what rock it is, and what that rock tends to put in well water.
What this can and can't tell you
It names the regional aquifer system USGS maps at your location. Whether your well taps it depends on the well's depth: a shallow well may draw from sand above it, and a deep one may be drilled past it into another formation. Your well's log, filed with the state when it was drilled, records the depth.
About four in ten acres of the lower 48 sit on no principal aquifer at all. Wells there draw from local fractured rock or small sand deposits that the national map doesn't outline — the lookup will say so.
Privacy
Your address is sent to a geocoder (Esri ArcGIS, with the U.S. Census Bureau as a fallback) to get coordinates. We don't log or store it.