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Map Layer Info

Realtime Streamflow Stations

What this map layer shows:

The locations of over 4,000 stream gaging stations that provide updated streamflow information to the National Atlas every few hours.
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Background Information
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The U.S. Geological Survey (USGS) Water Resources program, in cooperation with more than 800 Federal, State, and local agencies, operates a streamflow gaging-station network to collect nationally consistent information about the Nation's water resources and to help define and manage those resources. Individual stream-gaging stations are supported for specific purposes, such as water allocation, reservoir operations, or the regulation of permit requirements. However, the data are also used for flood hazard mitigation by the National Weather Service, the U.S. Army Corps of Engineers, and the Federal Emergency Management Agency, for resource planning, for infrastructure design of reservoirs and dams, and for many other purposes.

More than Over 4,000 of the USGS's approximately 7,000 stream gages are equipped with telemetry that transmits a reading of stream depth to an office by satellite or telephone. Computers in the office convert the depth reading to a value for flow and plot a graph of flow versus time, usually showing the previous 7 days. Some stations also transmit values for temperature, conductance, or other parameters. The data typically are updated every 4 hours, but this can vary depending on the equipment used and the flow status. More frequent updates may be made in times of flooding. Realtime hydrologic data are provisional and have not been reviewed or edited. Each station record is considered provisional until the data are published, which usually occurs within 6 months of the end of the water year (September 30). Data users are cautioned to consider carefully the provisional nature of the information before using it for decisions that concern personal or public safety or the conduct of business that involves substantial monetary or operational consequences.

The map layer available in the National Atlas Map Maker is a snapshot of realtime stations and is updated approximately every 6 months. The downloadable map of realtime stations usually is regenerated every business day. A "robot" program examines each of the Web servers that serve realtime data, compiles a list of realtime stations, and uses the list to regenerate the realtime map. Sometimes, States will be missing from the map. This usually indicates that the local Web server was unavailable when the "robot" tried to retrieve the list. If too many States are unavailable, the map will not be regenerated.

The Realtime Streamflow Stations map layer shows the locations of more than 4,000 realtime stream-gaging stations in the United States and Puerto Rico. Descriptive information includes the station ID number and location, flow information, and a Web address for accessing realtime hydrologic data. This map layer was compiled by the USGS.