California releases new San Joaquin Basin Flood-MAR studies to address rising flood and drought risks

California’s Department of Water Resources (DWR) has released a new set of San Joaquin Basin Flood-Managed Aquifer Recharge (Flood-MAR) Watershed Studies outlining how climate change is intensifying droughts and floods across the Calaveras, Stanislaus, Tuolumne, Merced, and Upper San Joaquin watersheds — and how stormwater capture can help offset those impacts.

The studies evaluate how pairing Forecast-Informed Reservoir Operations (FIRO) with Managed Aquifer Recharge (MAR) could reduce flood risk while boosting groundwater supplies in one of the state’s most stressed basins. FIRO leverages advanced weather forecasting to strategically time reservoir releases, creating space for incoming storms and allowing operators to route high flows to recharge sites. According to DWR, using FIRO-MAR “has the potential to increase the volume of recharge more than fourfold, and it can greatly diminish the size and frequency of flood flows.”

“San Joaquin Valley communities will be dramatically shaped by growing extremes in drought and flood, and our capacity to respond to them,” said DWR Director Karla Nemeth in a press release. “The Watershed Studies begin a broad path forward for the Valley – outlining the risk if we do nothing and what we can gain if we begin acting together now.”

DWR notes that implementing FIRO-MAR at scale will require new conveyance improvements, expanded recharge areas, and water-rights agreements with existing holders. The studies do not determine feasibility but offer planning-level analysis to guide pilot projects, reservoir reoperations, and long-term watershed investments.

DWR leaders emphasized the importance of the findings across programs. “The San Joaquin Basin Watershed Studies provide new insights that will help inform the State’s long-term flood management strategy,” said Laura Hollender, deputy director for Flood Management & Dam Safety, in a press release. Other division leaders said the work will bolster groundwater sustainability, ecosystem restoration, and State Water Project planning.

The Basinwide Summary and five watershed-specific reports are now available through DWR’s San Joaquin Basin Flood-MAR Watershed Studies resources.