New Report Outlines FIRO Benefits by ACWA Staff Mar 19, 2025 Water News OROVILLE – A new report released in March shows that changes to reservoir operations at Lake Oroville and New Bullards Bar Reservoir can further reduce flood risk for communities along the Yuba and Feather rivers during extreme atmospheric river storm events and potentially benefit water supply during drier periods, according to a Department of Water Resources (DWR) news release. The approach, known as Forecast-Informed Reservoir Operations, or FIRO, uses improved monitoring, weather, and runoff projections to build more flexibility and efficiency into reservoir operations. In the largest FIRO assessment to date, 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’ (USACE) 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. Using historical forecasts, reservoir storage and river flow data, scientists found that FIRO, combined with a planned second spillway at New Bullards Bar, could provide additional flood storage capacity in the Yuba-Feather system and reduce downstream peak flows during prolonged storms like the 1986 and 1997 floods that devastated Yuba County. To fully realize the benefits of FIRO, 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 ARC Spillway will help realize the full benefits of FIRO in our region by reducing peak flows downstream and decreasing stress on our levee system during large atmospheric river events,” explained Yuba Water’s Director of Resource Planning John James. “With both FIRO and the ARC Spillway, we’re essentially gaining the amount of flood storage that would historically only be created through building additional infrastructure. In this case, we’re enhancing existing infrastructure and using the latest in science and technology to modernize flood operations and improve public safety.” The ARC Spillway project is currently at 100% design with Yuba Water actively pursuing state and federal grant funding. Yuba Water anticipates construction could begin as soon as 2027. The existing spillway capacity at Oroville Dam is already adequate to fully realize the benefits of FIRO. FIRO is also being implemented successfully at Lake Mendocino in the Russian River watershed in Northern California and will soon be integrated into operations at Prado Dam in the Santa Ana River watershed in Southern California. As the largest and most complex FIRO assessment to date and the first with a primary goal of reducing flood risk, the Yuba-Feather FIRO Program continues establishing FIRO’s benefit in California as an important part of a comprehensive water management and resilience strategy.
