What is a river forecast?

A river forecast is a report of the amount of water flowing through a certain point along a river. The U.S. National Weather Service (NWS) maintains forecasts of hundreds of points determined to be at high risk for flooding conditions. The NWS relies heavily on a network of river gages operated by the US Geological Survey (USGS). Data is received from these river gages either by phone telemetry or satellite. During flooding, USGS technicians are out in the river areas taking flow measurements and relaying the information back to the NWS and other agencies. This information provides vital information for river flood warning and forecast programs.

Source: NOAA and NWS