As we step into 2025, the Sacramento region is starting the year on a positive note, thanks to the Bureau of Reclamation’s continued commitment to meeting a balanced planning minimum for Folsom Reservoir storage. This minimum, outlined in a Memorandum of Understanding (MOU) with the Water Forum, identifies a minimum storage level of 300,000 acre-feet by the end of December each year. In years with dry conditions, the minimum is 230,000 acre-feet. The MOU also outlines mechanisms for communication and information sharing between the Water Forum and Reclamation, as well as opportunities for regional actions to support Folsom storage levels.
These storage levels are vital for maintaining water flow and temperature in the lower American River, which are essential for the survival and reproduction of fish species like threatened fall-run Chinook salmon and federally listed steelhead trout. Maintaining adequate flows helps these species migrate, spawn, and thrive. The storage also provides a level of water supply reliability for the regional water agencies that depend on Folsom Reservoir and the lower American River. Lastly, improved end-of-year storage in Folsom reservoir better positions Reclamation to balance the many demands of their Central Valley Project (a statewide water delivery system which Folsom Reservoir is part of).
A Tale of Two Years: 2023 and 2024
The historic storms of 2023 brought abundant rain and snow, filling Folsom Reservoir and creating an opportunity for local water providers to implement in-lieu recharge strategies. By using surface water instead of groundwater, providers allowed groundwater to replenish naturally, banking over 12.3 billion gallons of water in underground aquifers. This approach both enhanced regional groundwater storage and positioned the area for resilience in future dry years.
In contrast, 2024 experienced “average” precipitation—an unusual occurrence in California’s increasingly variable climate. Folsom Reservoir reached 97% capacity in late spring, providing a solid foundation for managing lower American River conditions during critical summer and fall periods. However, the unusually hot summer of 2024—the hottest on record—posed challenges, particularly for maintaining optimal river temperatures for fish.
Reclamation relied on a power bypass in the fall of 2024—a method of releasing colder water from lower reservoir levels—to manage temperature targets to balance the needs of fish with available resources. Through careful management, river conditions supported fish habitat during the fall spawning cycle, although higher-than-ideal water temperatures delayed natural and hatchery spawning of fall-run Chinook salmon. With Reclamation’s help to keep river temperatures down and the Water Forum’s work to provide ideal spawning beds and side channels for rearing, the spawning and out migration results look encouraging this year.
Despite these challenges, Reclamation successfully met the balanced end-of-year planning minimum for Folsom Reservoir in 2024.
Implications for 2025 and Beyond
Strong year-end storage at Folsom Reservoir positions the region to better maintain adequate cold-water reserves in 2025, though careful management will still be required (especially given the dry start to 2025). Over the long term, agreements like the MOU provide a framework for addressing shifting climate patterns. Projections indicate earlier runoff peaks in wetter years and increased frequency of multi-year droughts. Historically, Folsom reservoir has been known to refill each summer, but with less snowpack in the future, that is not an assumption we can make any more. Strategies such as banking water in wet years and managing resources in average and dry years are essential for protecting our water supplies and environment.
As we reflect on the past year and look ahead, the Water Forum appreciates Reclamation’s partnership and commitment to meeting the MOU planning minimum. This collaborative effort highlights the value of shared responsibility in managing water resources for the American River region, and the people and environment who depend on them.
Featured photo: Folsom Reservoir, December 2023. Credit: CA DWR