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  • Due to a lapse in government funding, the majority of USGS websites will not be updated except to provide important public safety information. Websites displaying real-time water data will be updated with limited support. For more information, please see www.doi.gov/shutdown.

National aquifer codes

National aquifers are the principal aquifers or aquifer systems in the United States, defined as regionally extensive aquifers or aquifer systems that have the potential to be used as a source of potable water.

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Reference Systems