The Natural Resources Conservation Service (NRCS) of the U.S. Department of Agriculture provides data and information for the western United States, including:

1) Stream-flow forecasts for the first five months of each year, based on mountain snowpack.

2) Data and stream-flow outlooks by state and river basins, incorporating snow-pack and precipitation data.

3) Forecasts reflecting snowpack, stream-flow and reservoir storage. Please note: For some states the river basin reports may be generated and kept by state officials rather than the NRCS.

4) NRCS also provides experimental daily water supply forecasts

The National Weather Service's Advanced Hydrologic Prediction Service (AHPS) monitors and reports on river flood conditions and on low river water levels for the United States. The short- and long-term forecasts are also available. The long-term forecasts for low levels are available under local forecast points. Look for a tab below hydrograph under Additional Information and the link, How low could the river get?

Water supply forecasts and water resource outlooks from NOAA River Forecast Centers are provided by basin in general and for specific points using an interactive map. Forecasts are generally made only for basins with potentially significant amounts of snow melt. In addition to the forecast, point-specific information also includes climatology.

The Climate Impacts Group at the University of Washington produces hydrological and soil moisture monitoring and forecast maps for the western United States.