The U.S. Geological Survey's (USGS) National Water Information
System (NWIS) is a comprehensive and distributed application that
supports the acquisition, processing, and long-term storage of water
data. Water Data for the Nation serves as the publicly available portal to a
geographically seamless set of much of the water data maintained
Nationally, USGS surface-water data includes more than 850,000
station years of time-series data that describe stream levels,
streamflow (discharge), reservoir and lake levels, surface-water
quality, and rainfall. The data are collected by automatic
recorders and manual field
measurements at installations across the Nation.
Data are collected by field personnel or relayed through telephones
or satellites to offices where it is stored and processed. The data
relayed through the Geostationary Operational Environmental
Satellite (GOES) system are processed automatically in near real
time, and in many cases, current data
are available online within minutes.
Once a complete day of readings are received from a site, daily summary data are generated and made
available online. Annually, the USGS finalizes and publishes the
daily data in a series of water-data reports. Approved daily data
and peak data are updated annually following
publication of the reports.