California boosts state water allocation again, as heavy snow returns to the mountains

California water officials have again upped the projected delivery allocation for the State Water Project in 2023, as the state braces for a big winter storm this week after a string of storms earlier in the year replenished reservoirs and Sierra Nevada snowpack.

The California Department of Water Resources on Wednesday announced that the State Water Project, which stores and delivers water to 29 water agencies that serve 27 million Californians, will be able to deliver 35% of water supply requested this year by those agencies.

After nine atmospheric river storms from late December through last month soaked California, state water officials in late January announced a major boost, from 5% of requested water supply to 30%.

The increase announced Wednesday brings the forecast delivery to 1.48 million acre-feet of water (482 billion gallons), adding 210,000 acre-feet (68 billion gallons) from last month’s estimate.

Even with the allocation increase, state water officials warn that it is still very early in the year, and too soon to declare an end to California’s ongoing drought, which is now in its third year.

“We’re hopeful that more storms this week are a sign that the wet weather will return, but there remains a chance that 2023 will be a below average water year in the northern Sierra.” Karla Nemeth, director of the Department of Water Resources, said in a prepared statement.

Several feet of snow is forecast this week for the mountains, according to the National Weather Service, with significant amounts also expected in the Sierra Nevada foothills and even some accumulation possible at high elevations within the Sacramento Valley as a major winter storm envelops most of the U.S.

Snowpack across the Sierra Nevada range as of Wednesday was at 173% of normal for the date, according to the Department of Water Resources.

The new 35% allocation took into account snowpack calculations that were not yet available last month, when the allocation was set at 30%.

Nemeth at the time called the 30% figure a “fairly conservative” figure, and state water officials in Wednesday’s announcement said the 35% mark takes into account “an anticipation of dry conditions” between the end of this week’s storm and the beginning of April.

“Careful planning and the use of advanced forecasting tools will enable the Department to balance the needs of our communities, agriculture and the environment should dry conditions continue this spring and into next year,” Nemeth’s statement continued.

California’s two largest reservoirs included in the State Water Project, Lake Oroville and the San Luis Reservoir, gained a combined 1.62 million acre-feet of water during the stretch of December and January storms, state water officials said.

Lake Oroville’s water level stood at 115% of its historic average as of Wednesday.

State Water Project allotments are set each year on Dec. 1, then updated monthly through May or June. The state in December 2021 set an initial allocation of 0%, which ultimately increased to 5% for 2022.

A 30% allocation represents about half of the historic average for the project, Ted Craddock, deputy director of the State Water Project, said last month. The state last allocated 30% in 2019.

State Water Project allocations can be adjusted downward, if “extreme dry conditions warrant,” according to Wednesday’s news release.