Forecast Informed Reservoir Operations: Russian River Watershed
FIRO is a reservoir-operations strategy that better informs decisions to retain or release water by integrating additional flexibility in operation policies and rules with enhanced monitoring and improved weather and water forecasts (American Meteorological Society; 2020). Since 2014, CW3E and federal, state, and local partners have developed, tested, and implemented FIRO at reservoirs across the Western United States. FIRO is now being assessed nationwide.
PROJECT STATUS
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LAKE MENDOCINO |
Permanent FIRO Implementation |
Water Control Manual update complete |
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LAKE SONOMA |
Temporary FIRO Implementation |
Multi-year deviation in place |
OVERVIEW
The Russian River Basin in Northern California spans Sonoma and Mendocino counties and is strongly influenced by atmospheric rivers, which deliver much of the region’s annual rainfall. Lake Mendocino and Lake Sonoma are federally operated reservoirs managed by the U.S. Army Corps of Engineers (USACE) for flood risk reduction and water supply. USACE works in partnership with Sonoma Water, which manages releases from the water supply pool.
Together, the reservoirs provide water to Mendocino, Sonoma, and Marin counties, while supporting agriculture, and maintaining downstream flows critical for endangered salmon species. FIRO at Lake Mendocino is officially authorized in the USACE Water Control Manual and is advancing at Lake Sonoma through multi-year deviation testing and technical evaluation.
The motivation for implementing FIRO in the Russian River Watershed is to increase water supply reliability through dry summers and falls without compromising flood control during the atmospheric river-dominated wet season. Current efforts to implement FIRO at Lake Sonoma will improve resilience to drought and floods throughout the watershed.
FIRO BENEFITS
130,500 acre-feet of additional water in Lake Mendocino & Lake Sonoma between Water Year 2017 – 2026
Lake Mendocino has increased water conservation opportunities within the flood control space through FIRO operations since 2017, totaling approximately 54,500 acre-feet of new water through March 31, 2026. Lake Sonoma began testing FIRO in 2023, adding approximately 19,000 acre-feet annually for a total of ~76,000 acre-feet through 2026. The 2021 and 2022 bars (Lake Mendocino FIRO Carryover) reflect water retained from prior FIRO operations during drought years rather than new additions, and are not included in the 130,500 acre-foot total. During Water Years 2021 and 2022, FIRO helped keep Lake Mendocino from going dry and supported more favorable in-stream flows for both water supply and the environment relative to conditions without FIRO.
KEY ACHIEVEMENTS
#1
Lake Mendocino was the first reservoir to formally authorize FIRO into its USACE Water Control Manual in October of 2025.
800,000+
People across Mendocino, Sonoma, and Marin counties benefit from the increased water supply
7
Cross-sector partner organizations working collaboratively to implement FIRO Russian River
STEERING COMMITTEE
Co-Chairs
Don Seymour, Sonoma Water
F. Martin Ralph, Center for Western Weather and Water Extremes, Scripps Institution of Oceanography, UC San Diego
Nick Malasavage, US Army Corps of Engineers, San Francisco District
Members
Michael Anderson, California State Climate Office, California Department of Water Resources
Chris Frans, U.S. Bureau of Reclamation
Joseph Forbis, US Army Corps of Engineers, Engineer Research and Development Center
Joshua Fuller, National Marine Fisheries Service, NOAA
Cary Talbot, US Army Corps of Engineers, Engineer Research and Development Center
Mimi Abel, Physical Sciences Laboratory, NOAA
Patrick Sing, US Army Corps of Engineers, San Francisco District
Support Staff
Arleen O’Donnell, Eastern Research Group
Rob Hartman, RKH Consulting Services
Jay Jasperse, Sonoma Water/CW3E
Michael Konieczki, HDR Inc.
Jon Rutz, Center for Western Weather and Water Extremes, Scripps Institution of Oceanography, UC San Diego
Kyla Van Maanen, Center for Western Weather and Water Extremes, Scripps Institution of Oceanography, UC San Diego
RESOURCES
Lake Mendocino
Final Viability Assessment (12/20)
Final Viability Assessment One-Page Summary
Preliminary Viability Assessment (7/17)
Lake Mendocino Work Plan Fact Sheet
Lake Mendocino FIRO Overview One-Pager
Lake Sonoma
RUSSIAN RIVER FIRO NEWS
Sonoma Water 2025 Urban Water Management Plan
RELEVANT CW3E PUBLICATIONS
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Contact Kyla Van Maanen at kvm@ucsd.edu for more information
Last updated: June 30, 2026