SACRAMENTO, CA (MPG) - On Dec. 2, the Department of Water Resources (DWR) announced an initial State Water Project (SWP) allocation forecast of five percent of requested supplies for 2025.

The State Water Project provides water to 29 public water agencies that serve 27-million Californians.

The December initial water supply forecast is the first allocation of the new water year and is based on current reservoir storage and conservative assumptions for precipitation to come. For comparison, the initial allocation for Water Year 2024 was 10 percent of requested supplies and it eventually increased to 40 percent by the end of the season.

The initial allocation forecast announced Dec. 2 does not take into account the series of strong storms that brought precipitation to above average across Northern California in the last two weeks of November. These storms will be taken into account, along with other variables, for future allocation updates. Prior to these storms, the start of the water year had been dry and warm.

“Based on long-range forecasts and the possibility of a La Niña year, the State Water Project is planning for a dry 2025 punctuated by extreme storms like we’ve seen in late November,” said the Department of Water Resources Director Karla Nemeth. “We need to prepare for any scenario, and this early in the season, we need to take a conservative approach to managing our water supply. Our wettest months of the season are still to come.” 

“What we do know is that we started the water year following record heat this summer and in early October that parched the landscape. We must account for dry soils in our State Water Project allocation planning and our runoff forecasts for the spring,” Nemeth said. 

Soil moisture is critical to the success of California’s water years. If the soil is too dry, snowpack runoff in the spring will absorb into the ground instead of providing water supply to the state’s reservoirs. The ability to incorporate soil moisture into runoff forecasts is one of many recent improvements for State Water Project operations. Investments in Forecast Informed Reservoir Operations (FIRO) and improved data collection through the Department of Water Resources’ $7-million California Stream Gage Improvement Program will also help the Department of Water Resources and other agencies to incorporate the best available science and data into water management decisions.

Also new this season, the State Water Project has revised its operating permit to allow for new tools and resources to better manage the water supply for endangered fish species and millions of Californians. Earlier this month, the State Water Project received a new Incidental Take Permit from the California Department of Fish & Wildlife that covers five species protected under the California Endangered Species Act: Delta smelt, longfin smelt, white sturgeon, winter-run Chinook salmon and spring-run Chinook salmon. The new permit went into effect on Nov. 4.

Each year, the Department of Water Resources provides the initial State Water Project allocation based on available water storage, projected water supply and water demands. Allocations are updated monthly as snowpack, rainfall and runoff information is assessed, with a final allocation typically determined in May or June. As the winter progresses, if California sees an increase in rain and snowfall, the allocation forecast might increase.

Historical data on State Water Project allocations is available at water.ca.gov.