Atmospheric Rivers

What is an Atmospheric River?

Atmospheric rivers consist of narrow bands of enhanced water vapor which provide approximately half of the major rainfall in the Russian River watershed.


Sonoma Water and Scripps Institution of Oceanography Enter into Partnership to Study Atmospheric Rivers, Drought Relief Initiatives

Sonoma Water has entered into a cooperative agreement with Scripps Institution of Oceanography and the Center for Western Weather and Water Extremes (CW3E) to advance research in ocean science and meteorology.  The research will help define the role of atmospheric rivers in filling Lake Mendocino and potentially offering predictability to retain water without increasing flood risk. The partnership will also develop a feasibility assessment project for the potential use of forecast-informed reservoir operations (FIRO) for Lake Mendocino in cooperation with the US Army Corps of Engineers. 


Atmospheric River Washington, D.C. Hill Briefing, July 13, 2016

On July 13, 2016 a briefing was held on the Hill in Washington, D.C. for Congressional staff about atmospheric rivers, subseasonal-to-seasonal precipitation prediction needs, related weather forecasting technology, and their potential benefits of water management.  View a photo presentation of the briefing here. The briefing was moderated by Sonoma Water Director Shirlee Zane and panelists included:

  • Dr. Louis Uccellini, Assistant Administration for Weather Services, National Oceanic and Atmospheric Administration and Director, National Weather Service
  • Dr. Cary Talbot, Program Manager, Engineer Research and Development Center, U.S. Army Corps of Engineers
  • Ms. Jeanine Jones, Western States Water Council
  • Dr. F. Marty Ralph, Director of the Center for Western Weather and Water Extremes, UCSD/Scripps Institution of Oceanography

Atmospheric river-driven storms can make or break a water year in the West. An interagency, cross-disciplinary team of experts is exploring the viability of utilizing forecasts of atmospheric rivers and their heavy precipitation in operational decisions at key western reservoirs that have been plagued by drought. Such forecasts could provide sufficient notice of these events to enable prudent planning and adaptable operation so that water managers would be better positioned to maximize water supply while maintaining public safety. Additionally, water decisions across the West can benefit from longer lead time information on precipitation from weeks to seasons in advance. The briefing was hosted by the Association of California Water Agencies, Western States Water Council, Scripps Institution of Oceanography and Sonoma Water.

View the presentations from the briefing:


Lake Mendocino Forecast Informed Reservoir Operations (FIRO)

Sonoma Water has entered into a cooperative agreement with Scripps Institution of Oceanography and the Center for Western Weather and Water Extremes (CW3E) to advance research in ocean science and meteorology. The research will help define the role of atmospheric rivers in filling Lake Mendocino and potentially offering predictability to retain water without increasing flood risk. The partnership will also develop a feasibility assessment project for the potential use of forecast-informed reservoir operations (FIRO) for Lake Mendocino in cooperation with the U.S. Army Corps of Engineers. 

These are a few documents that more fully explain efforts to use improved forecasting techniques to increase water supply in Lake Mendocino:

Learn more about FIRO.

Background Materials

Media articles and water agency information

Presentations from Western States Water Council S2S Workshops

More Information

These are a few links that more fully explain Atmospheric Rivers: