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Help using the USGS Water Data for the Nation Site water-quality data retrieval system

! Discrete water samples data are undergoing modernization with this page no longer being updated with the latest data starting March 11, 2024
with a full decommission expected 6 months later. Learn more about the upcoming change and where to find the new samples data in our blog.
Help home page Navigation help Search criteria help
Output formats help Codes help Parameter help

This page introduces the water-quality data base, and guides new users through example data retrievals. Although a few definitions are provided herein, more complete definitions are provided on the main USGS Water Data for the Nation help page.


Recent updates

Major enhancements to the water-quality database and the display of these data were incorporated into the USGS Water Data for the Nation Site in July 2007. Read the news section for more information.


The USGS Water Data for the Nation water-quality data base is a compilation of the USGS Water Science Center NWIS data bases. It is very large (about 5 million samples), with many types of measurements for many different environmental media, from USGS and other agencies. Search criteria are necessary to focus your search. There often is more than one way to locate desired data. The examples provided below are meant to familiarize new users with the system.

Brief explanation of data base

Understanding of a few key elements of the data base is essential to understanding what kind of data you retrieve. Technical data analyses often require more detailed information and coding

Site type describes whether the site is a surface-water, groundwater, precipitation-monitoring, or other site type.

Site name describes the location of the site. Often, the site type can be inferred from the site name. Requesting "list of sites" output formats allows users to view basic information for each site.

Medium type or medium code defines what kind of sample was collected for analysis. This question is particularly important for surface-water sites, which can have samples for several media (water, biological tissue, stream-bottom sediments, suspended sediments, etc.).

Parameter codes are used to identify the water-quality values stored in the data base. Each code is linked to a definition. Parameter-code definitions typically contain information about what was analyzed, what units are associated with the numerical data, and sometimes, how the sample was processed prior to analysis (filtering, for examples). Definitions for each retrieved parameter are provided in the heading of each output.

Data retrievals-general guidance

Retrieving data from this site consists of the following steps (starting from the main USGS Water Data for the Nation water-quality sample page).

Some hints:

Example data retrievals

Additional information for technical data analysis

Data retrievals-precautions