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Primary & Principal Aquifers

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, the Department of Health, in 1980, identified eighteen Primary Water Supply Aquifers (usually referred to simply as Primary Aquifers) across the state excluding Long Island aquifers. Later, NYSDEC recognized another type of productive aquifer designated as Principal Aquifers.

Primary Aquifers

These 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 United States Geological Survey (USGS) reports. The map above shows the locations of Primary Aquifers and their names. Click on this 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 at the bottom of this page. Please note, 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 mapping at a 1:24,000 scale is incomplete. However extensive mapping coverage exists at a 1:250,000 scale. The USGS link in the right margin titled "USGS Mapping of Unconsolidated Aquifers of Upstate New York" contains maps of both scales. Additionally, there are GIS datasets for 1:24,000 and 1:250,000 scale aquifer maps.

Principal Aquifer Determinations

Any location within the mapped boundaries of a Primary or Principal Aquifer is considered to overlie such aquifer. In cases where the Primary/Principal Aquifer boundary is within 2000 feet of a proposed facility, contact DOW for final location review.

To determine if a location exists within a Primary or Principal Aquifer, use of GIS is recommended. See the section titled GIS Data Sets, below. Alternatively, USGS maps can serve this purpose.

As a first step to using USGS maps, examine the published Primary and Principal Aquifer maps (outside link leaving DEC's 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 refereenced on this page.

If these maps do not cover the location in question, refer to the USGS 1:250,000 maps titled Unconsolidated Aquifers in Upstate New York (outside link leaving DEC's website).

When examining the 1:250,000 scale maps, in either paper or GIS form, 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 the Department. Similar information may be submitted to demonstrate that a Principal Aquifer exists where it has not been previously mapped. In these cases the 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 (outside link leaving DEC's website) is available at the NYS GIS Clearinghouse. Enhancements were made to these maps to create digital, georeferenced 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 (outside link leaving DEC's website) is also available at the NYS GIS Clearinghouse.


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