Water Supply

Western Water Supply Forecasts

Western Water Supply Forecasts - This web page allows water resource managers to use powerful interactive forecasting tools to show expected seasonal water volumes at over 500 locations in the western United States. These tools allow users to see the probability of a stream producing a given seasonal water volume. The interactive capability allows users to generate future runoff scenarios based on historical observed precipitation and temperatures, or from an ensemble of previous years. In addition, the skill of forecasts which were made during previous years can be verified by comparing them to observed values.

The web page was recently upgraded in early 2009 to provide more extensive capabilities for viewing and analyzing water supply forecasts and water resource outlooks. Enhancements include additional map layers, water supply tools, expanded forecast verification, climate sensitivity studies, and a revamped format that includes help documentation.

The Water Supply Outlook for California and northern Nevada is issued January through May by the California Nevada River Forecast Center, National Weather Service. It represents a coordinated forecast effort between the National Weather Service, the California Department of Water Resources, the National Resource Conservation Service, the U.S. Bureau of Reclamation, and local water district managers.

All forecast volumes reflect natural flow. Actual observed flow may be affected by upstream water management.

All Monthly Water Supply Outlooks and verification products are published in .pdf format (requires Adobe® Acrobat Reader). A shorter text version that contains forecasts only is also available.

Current Monthly Water Supply Outlooks

Upper Klamath Basin June Water Supply Update - issued June 04, 2009
East Side Sierra Nevada/Humboldt Basin June Water Supply Update - issued June 04, 2009

May 2009 Water Supply Outlook (full report - Adobe PDF) - issued May 11, 2009
May 2009 Water Supply Outlook (text version) - issued May 07, 2009

Historical Archive - Monthly Water Supply Outlooks and Annual Verification

*special June update for Klamath and East-side Sierra Nevada

Statewide Water Conditions is now available on the CDEC website and contains a series of links to hmtl, text, and pdf format reports.

The web page Water Supply Outlook for the western United States hosted by the CBRFC presents a broader picture of water supply outlook conditions for the western United States, including:

- graphical and tabular streamflow forecasts
- monthly and seasonal precipitation
- mountain snowpack and satellite areal extent of snow cover
- reservoir storage

It is issued jointly by the National Weather Service and the USDA Natural Resources Conservation Service.

Runoff volume forecasts for the snowmelt season are seasonal products, issued weekly from about mid-April until peak stages occur (typically early to mid June). Indicated values are unimpaired flow volumes in thousands of acre-feet in 5 day intervals for the next 20 days. Runoff forecasts are updated every Wednesday during the snowmelt season and are published in .pdf format (requires Adobe® Acrobat Reader).

Snowmelt Runoff Volume Forecast - issued Wed, May 27, 2009 - Please Note: 06/03 - An error was corrected for the Kern River at Isabella Peak 1-Day Volume and Date. This will be the final forecast for the season. Please contact the CNRFC if additional guidance is needed.

Previous Snowmelt Runoff Volume Forecasts issued duing the 2009 season are listed below with links to each document.

• April 15, 2009
• April 22, 2009
• April 29, 2009
• May 06, 2009
• May 13, 2009
  
• May 20, 2009