California's biggest reservoir reaches capacity for third straight year

San Francisco Chronicle​

04-05-2025

California's largest reservoir, Shasta Lake, reached capacity this week, marking the third straight year it has filled or nearly filled with water.
The run of big water years at the reservoir reflects the unusual string of wet winters the state has experienced, and it bodes well for water supplies this year across California.
The lake, which stretches across an extraordinary 35 miles in the southern Cascades north of Redding near Mount Shasta, is the cornerstone of the federally run Central Valley Project. Its supplies are sent to cities and farms hundreds of miles away, including the Bay Area. The San Joaquin Valley's booming agricultural industry is the primary beneficiary.
The lake's water, collected from the Sacramento River, also generates hydroelectricity and is used to manage downriver flows for wildlife and water quality.
The last time Shasta Lake hit capacity or near capacity for three consecutive years was 2010 through 2012.
Early in the week, the Bureau of Reclamation announced a slight increase in the amount of water it expects to deliver this year from Shasta Lake and the nearly 20 other reservoirs in the Central Valley Project.
According to the announcement, most water suppliers for farms in the San Joaquin Valley will get 50% of what they requested, up from the 40% projected in March. Water suppliers north of the Sacramento-San Joaquin River Delta are still slotted for 100% of what they requested while municipal suppliers south of the delta remain pegged for 75%.
The State Water Project, a network of reservoirs that runs in parallel to the federal project, also increased its projected deliveries from 40% to 50% this week. Its flagship reservoir, Lake Oroville, is also expected to fill.
On Thursday, the state's major reservoirs cumulatively held 118% of the water they typically hold this time of year, according to the California Department of Water Resources.
State and federal decisions about how much water to deliver are based largely on the amount of water held in reservoirs, much of it coming from spring snowmelt in the Sierra Nevada and southern Cascades. But there are other factors, too, both hydrological, such as how quickly the snow melts, and regulatory, including how much water must be released from reservoirs for rivers and fish.
This year, snowpack across the state measured 96% of average on April 1, the point at which it typically peaks. Seasonal precipitation stands at 99% of average. The past two years were wetter, with snowpack at 111% of average in April 2024 and 237% of average in April 2023.
With snowmelt now in full force, Shasta Lake peaked on Tuesday. The reservoir held 4,405,312 acre-feet of water, federal data shows, leaving it less than five feet from topping out, which water officials consider 'full pool.' (An acre-foot of water is equal to what two to three households use in a year.)
Since Tuesday, the Bureau of Reclamation has increased water releases from the reservoir, which has dropped lake levels.
'Operation of the Central Valley Project supports food and economic development not only for California, but the nation,' said Michael Burke, a spokesman for the U.S. Bureau of Reclamation, which runs the federal project, in an email. 'With a full (Shasta) reservoir we can meet the needs of the communities downstream and generate power when it is needed the most.'