California water managers have announced their preliminary forecast of supplies that will be available next year from the State Water Project, telling 29 public agencies to plan for as little as 5% of requested allotments.
The state Department of Water Resources said Monday that the initial allocation is based on current reservoir levels and conservative assumptions about how much water the state may be able to deliver in 2025.
“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,” DWR Director Karla Nemeth said.
The Newsom administration is projecting that California’s State Water Project could lose up to 23% of its water delivering capacity within 20 years.
Last year, the state’s initial forecast was 10% of requested supplies, but the allocation was increased to 40% in the spring.
Officials said the initial water supply forecast does not take into account the series of storms that drenched much of the state in the last two weeks of November. The storms pushed precipitation to above-average levels in Northern California for this time of year.
“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,” Nemeth said. “What we do know is that we started the water year following record heat this summer and in early October that parched the landscape.”
She said officials considered runoff forecasts that account for how the hot, dry conditions in the summer and October left parched soils. When soils are too dry, runoff from the mountain snowpack will typically be soaked up by the ground, reducing the amount of water flowing in streams and rivers to reservoirs.
A weak La Niña is forecast to appear this winter, and NOAA forecasters have said the pattern will likely bring drier-than-average conditions in much of the Southwest. They have also said, however, that the outlook is uncertain for much of California.
The State Water Project’s aqueducts and pipelines transport water from the Sacramento-San Joaquin River Delta to 29 water agencies that supply 27 million people.
State officials update the allocation monthly, and may increase their forecast based on the rainfall, snowpack and reservoir levels. A final allocation for the State Water Project is typically announced by May or June.
