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Map of Sole Source Aquifer Locations

National Geographic Information Systems (GIS) layer of SSAs

Information on sole source aquifers (SSAs) is widely used in assessments under the National Environmental Policy Act and at the state and local level. A national layer, including all available SSA coverages, is available for use in GIS. This layer includes a total of 89 GIS polygons for SSAs.

In addition to single SSA designated area polygons, some EPA regional offices have delineated GIS layers for:

  • Streamflow zones
  • Aquifer recharge areas
  • Other features at the land surface important for SSA designations

The SSA geospatial data set is available through for use by government agencies, private organizations, and the public.  Visit to download the data.