Reducing flood risk through Forecast-Informed Reservoir Operations in California

A new report released on March 13, 2025, shows that changes to reservoir operations at Lake Oroville and New Bullards Bar Reservoir in California can further reduce flood risk for communities along the Tuba and Feather rivers during extreme atmospheric river storm events and potentially benefit water supply during drier river periods.

The approach, known as Forecast-Informed Reservoir Operations (FIRO), uses improved monitoring, weather and runoff projection to build more flexibility and efficiency into reservoir operations.

The California Department of Water Resources (DWR) and Yuba Water Agency partnered with the Center for Western Weather and Water Extremes (CW3E) at UC San Diego’s Scripps Institution of Oceanography and the U.S. Army Corps of Engineers’ Engineering Research and Development Center to evaluate if FIRO could be implemented at both reservoirs to reduce downstream flood risk without negatively impacting water supplies.

Lake Oroville is managed by DWR and New Bullards Bar is managed by Yuba Water Agency.

Scientists found that FIRO, combined with a planned second spillway at New Bullards Bay, could provide additional flood storage capacity in the Yuba-Feather system and reduce downstream peak flows during prolonged storms.

“California’s reservoirs play a critical role in safeguarding our communities from floods and maintaining our state’s water supply, especially as we continue to see more extreme weather events in the form of larger, wetter, and more frequent storms and longer, more severe periods of drought,” said DWR’s State Climatologist Dr. Michael Anderson in a press release. “The Yuba-Feather FIRO Viability Assessment is an important step toward improving flood protection to communities downstream while managing California’s valuable water resources for decades to come.”

Yuba Water is planning operational changes, continued atmospheric river monitoring and the construction of a new Atmospheric River Control (ARC) spillway at New Bullards Bar.

The second spillway will have gates 31.5 feet lower than the dam’s existing spillway gates, allowing the agency to release water before large, threatening storms hit, when there is enough downstream channel capacity to handle the flows.

The project is currently at 100% design with Yuba Water actively pursuing state and federal grant funding. Construction could begin as soon as 2027.

Utilizing FIRO during the wetter winter months may also benefit the region. Both DWR and Yuba Water are required to draw down their reservoirs to ensure there is enough flood storage.

Since advanced weather forecasting tools give dam operators more notice of incoming storms, water releases to reduce flood risk may begin earlier using FIRO, providing additional storage capacity to capture increase runoff into reservoirs.

As storm systems pass and dry conditions return, releases from reservoirs can be reduced which can potentially benefit water supply.