U.S. Geological Survey site numbers

USGS site identification numbers

All U.S. Geological Survey (USGS) data sites (also referred to as "sites") are assigned a unique identification number. This number is unique in that it applies specifically to a given site and to no other. The number usually is assigned when a site is first established and is retained for that site indefinitely. The system used by the USGS to assign identification numbers for surface-water site s and for ground-water sites differ, but both are based on geographic location. The "downstream order" system is used for surface-water sites and the "latitude-longitude sequence number" system is used for wells, off-stream sites, and sites where there is difficulty in assigning a meaningful downstream order number, or where data are obtained intermittently.

Downstream Order System

Since October 1, 1950, the order of listing surface-water site records in USGS reports is in a downstream direction along the main stream. All sites on a tributary entering upstream from a mainstream site are listed before that site. A site on a tributary that enters between two mainstream sites is listed between them.

The site-identification number is assigned according to downstream order. Gaps are left in the series of numbers to allow for new site s that may be established; hence, the numbers are not consecutive. The complete number for each site, such as 02351890 includes the two-digit basin identifier "02" plus the downstream-order number "351890", which can be from six to 12 digits. Most surface-water site numbers are eight digits; however, up to 14 digit numbers are permissible.

Latitude-Longitude Sequence Number

The latitude-longitude sequence number identifier is a 15-digit number assigned to a site. The number is formed initially from the latitude and longitude of a point believed to represent the location of a site, followed by a two-digit sequence number.

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