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Aquifers in New York State

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Primary and/or principal aquifers are afforded special protection by regulations governing the siting of landfills (leaves DEC website), oil and gas wells, and tire stockpiles. Any location within the mapped boundaries of a Primary or Principal Aquifer is considered to overlie such an aquifer. In cases where the Primary/Principal Aquifer boundary is within 2,000 feet of a proposed facility, contact DOW for final location review.

GIS is recommended to determine if a location is within a Primary or Principal Aquifer. See the section titled GIS Data Sets, below. Alternatively, US Geological Survey (USGS) maps can serve this purpose.

When using USGS maps, examine the published Primary and Principal Aquifer maps (leaves DEC website).

Map of New York's primary and principal aquifers
Primary and Principal Aquifers in New York State.
For detailed mapping see the websites listed in the right margin
of this webpage or use the GIS dataset referenced below.

If these maps do not address the location in question, refer to the USGS 1:250,000 maps titled Unconsolidated Aquifers in Upstate New York (leaves DEC website).

Areas shown as "Unconfined Aquifer 10 to 100 gallons per minute" or "Unconfined Aquifer more than 100 gallons per minute" are considered to be Principal Aquifers unless contradictory site specific information is made available to DEC. Similar information may be submitted to demonstrate that a Principal Aquifer exists where it has not been previously mapped. In these cases the DEC Division of Water will review any such investigations and make a final determination.

GIS Data Sets

A GIS data set containing the mapping of 1:24,000 scale Primary and Principal Aquifers (leaves DEC website) is available at the NYS GIS Clearinghouse. Enhancements were made to these maps to create digital, geo-referenced map layers. The digital map layers contain original mapping units and aquifer boundaries as well as new standardized mapping units and updated aquifer boundaries. The original published aquifer maps contain additional base and geologic information not included in these map layers.

Additionally, a GIS coverage for 1:250,000 scale Principal Aquifers (leaves DEC website) is available at the NYS GIS Clearinghouse.

Primary Aquifers

Primary Aquifers are defined in the Division of Water Technical & Operational Guidance Series (TOGS) 2.1.3 as "highly productive aquifers presently utilized as sources of water supply by major municipal water supply systems".

View of the Chemung River Valley
The aquifer underlying the Chemung River Valley at
Big Flats, NY is part of the Elmira Primary Aquifer

All of the Primary Aquifers have been mapped in detail at a scale of 1:24,000. They are available as USGS reports. The map above shows the locations of Primary Aquifers and their names. Click on the map to see a larger image in which the aquifers are linked to their respective USGS reports. Additionally, the GIS dataset for this type of aquifer may also be used and is detailed above. This dataset contains 1:24,000 scale maps of Primary and Principal Aquifers.

Principal Aquifers

Another category listed in TOGS 2.1.3 is Principal Aquifers. These are "aquifers known to be highly productive or whose geology suggests abundant potential water supply, but which are not intensively used as sources of water supply by major municipal systems at the present time". Principal Aquifer mapping at a 1:24,000 scale is ongoing through the cooperative USGS/DEC aquifer mapping program and available online at the USGS. Complete upstate New York mapping coverage exists at a 1:250,000 scale. Mapping reports at both scales can be viewed at the USGS webpage titled "USGS Mapping of Unconsolidated Aquifers of Upstate New York" (leaves DEC website). Additionally, there are GIS datasets for 1:24,000 and 1:250,000 scale aquifer maps.

Sole Source Aquifers

Sole Source Aquifers are designated as the sole or main source of drinking water for a community by the US Environmental Protection Agency under provisions of the Federal Safe Drinking Water Act. DEC believes that all of the Primary Water Supply Aquifers in New York State would qualify for designation as Sole Source Aquifers. However, there is no direct technical relationship between the federal designation of "Sole Source" aquifers and the state designation of Primary and Principal Aquifers.

Please visit the EPA's webpages for more information on their Sole Source Aquifer program (leaves DEC's website).


About one quarter of New Yorkers rely on groundwater as a source of potable water. In order to enhance regulatory protection in areas where groundwater resources are most productive and most vulnerable, in 1980 the Department of Health identified twenty-one Primary Water Supply Aquifers (usually referred to simply as Primary Aquifers) across the state excluding Long Island Aquifers. Later, DEC recognized another type of productive aquifer designated as Principal Aquifers. Sole Source Aquifers are designated by the US Environmental Protection Agency as the sole or main source of drinking water for a community, under provisions of the Federal Safe Drinking Water Act. The designations are made in response to a petition from the locality, and after public hearing. New York State has little influence over such designations.

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