Center for Western Weather and Water Extremes (CW3E)

This Work Plan lays out an approach and scope for assessing the viability of Forecast Informed Reservoir Operations (FIRO) at Howard A. Hanson Dam. Tacoma Water and the U.S. Army Corps of Engineers Seattle District are collaborating with Center for Western Weather and Water Extremes at Scripps Institution of Oceanography at UC San Diego, the U.S. Army Corps of Engineers Research and Development Center, the National Oceanographic and Atmospheric Administration National Weather Service, the National Marine Fisheries Service, King County River and Floodplain Management, and the Muckleshoot Indian Tribe to assess the benefits of reservoir management scenarios using forecasts. The Howard A. Hanson Dam FIRO project will investigate this key question: How can improved forecasts of landfalling atmospheric rivers and associated precipitation and runoff be used to improve the reliability of spring refill to meet instream flows for fish and water supply storage objectives, improve the effectiveness of summer water management in advance of the fall flood transition period, maintain or improve operations for downstream flood risk management, and ensure forecasts and operations are flexible enough to respond to a changing climate without impacting flood risk, water storage reliability, and flows for fish?

This Workplan lays out an approach and scope for assessing the viability of Forecast Informed Reservoir Operations at Seven Oaks Dam. In 2023, San Bernardino Valley Municipal Water District initiated a partnership with the U.S. Army Corps of Engineers and the Center for Western Weather and Water Extremes at Scripps Institution of Oceanography, UC San Diego, to form a multi-agency Steering Committee which seeks to answer a key question: Can current and improved forecasts of individual and series of landfalling atmospheric rivers and other storm types and their associated precipitation, temperature, and runoff be used to inform flexible reservoir operations at Seven Oaks Dam to increase water conservation and to enhance and protect habitat through strategic releases, while maintaining flood risk management objectives?  

This Final Viability Assessment (FVA) presents results and recommendations for future Forecast Informed Reservoir Operations (FIRO) at Prado Dam. In 2017, Orange County Water District (OCWD) initiated a partnership with the U.S. Army Corps of Engineers (USACE) and the Center for Western Weather and Water Extremes (CW3E) at Scripps Institution of Oceanography (SIO), UC San Diego, to form a multi-agency Steering Committee and test FIRO as a method to improve water supply reliability, while not impairing and possibly enhancing habitat and flood risk management. This FVA builds on the 2021 Preliminary Viability Assessment (PVA), which demonstrated that FIRO is viable at Prado Dam. The ultimate goal of this project is to inform the update of USACE’s Water Control Manual (WCM) for Prado Dam to allow flexible FIRO operations, as demonstrated by rigorous analyses and documented in this FVA.

Recognizing the importance of Atmospheric Rivers (ARs) in a changing climate, Yuba Water and the California Department of Water Resources (DWR) are working with Scripps Institution of Oceanography’s Center for Western Weather and Water Extremes (CW3E) at UC San Diego, the U.S. Army Corps of Engineers (USACE), the National Weather Service, and other members of the Yuba-Feather Steering Committee to implement Forecast Informed Reservoir Operations (FIRO) at New Bullards Bar (NBB) and Lake Oroville (ORO) in the Yuba and Feather River watersheds. FIRO is a flexible water management strategy that uses improved weather and runoff forecasts to help water managers retain or release water from reservoirs to increase resilience to droughts and floods. The primary objective of this FIRO project is to reduce flood risk; a secondary objective is to achieve water supply benefits where possible, while supporting environmental needs. This FIRO Preliminary Viability Assessment (PVA) indicates strong potential for FIRO to be a viable water management strategy for reducing flood risk in the Yuba and Feather River watersheds.

This Preliminary Viability Assessment (PVA) was initiated by the Prado Dam Forecast Informed Reservoir Operations (FIRO) multi-agency Steering Committee in 2017 and follows the workplan completed in 2019. The PVA provides an initial evaluation of the viability of FIRO as a strategy for improving water supply reliability for Orange County Water District (OCWD), while not impairing and possibly enhancing environmental conditions and flood risk management. Constructed and operated by the U.S. Army Corps of Engineers (USACE), Prado Dam was primarily designed for flood risk management. Stormwater capture for downstream groundwater recharge into OCWD’s water supply is a secondary purpose. The PVA demonstrated that FIRO is viable, and it lays the groundwork for a Final Viability Assessment (FVA) and recommendations for updating USACE’s Water Control Manual (WCM), which governs operation of Prado Dam.