The Delta-Mendota Canal runs south along the western edge of the San Joaquin Valley, parallel to the California Aqueduct for most of its journey, but it diverges to the east after passing San Luis Reservoir, which receives some of its water. The water is pumped from the canal and into O’Neill Forebay. Then it is pumped into San Luis Reservoir by the Gianelli Pumping-Generating Plant.

With California entering a third year of drought and its reservoirs at low levels, the federal government has announced plans to deliver minimal amounts of water through the Central Valley Project, putting many farmers on notice that they should prepare to receive no water from the system this year.

The federal Bureau of Reclamation, which manages the project’s dams and canals, announced a zero-water allocation for irrigation districts that supply many farmers across the Central Valley. Cities that receive water from the project in the Central Valley and parts of the Bay Area were allocated 25% of their historical water use.

“Conditions are very dry. And as a result, we have to be very cautious with these allocations,” said Ernest Conant, the bureau’s regional director.

After a wet start to the rainy season in October and December, the state has gone through an extremely dry stretch in January and much of February. Conant pointed out that January and February are on pace to be the driest on record.

Without those critical months of snow and rain, the state has less to count on to boost major reservoirs, which were already low after two dry years.

Last February, the Bureau of Reclamation started with a 5% allocation for many agricultural water users and a 55% allocation for cities. But the hot, dry conditions last spring shrank inflows from rain and snowmelt much more than projected, Conant said, and the agency decided to reduce allocations to 0% for the irrigation districts and 25% for cities — the same reductions the agency is starting with this year.

“We’re getting a certain amount of criticism from the agricultural community for these low allocations, but we have to be prudent and cautious with these very dry conditions,” Conant said. “If it doesn’t rain in March, it’s possible it could get worse.”

The Central Valley Project stretches about 400 miles from the Redding area to the southern end of the San Joaquin Valley, with 20 dams and about 500 miles of main canals. One of California’s two main north-south water conduits, the project pumps water from the Sacramento-San Joaquin River Delta near the intakes of the other major system, the State Water Project.

The federal government has  more than 270 water contracts on the Central Valley Project to supply entities including large irrigation districts, individual farmers and cities.

The project also supplies agricultural water users with senior rights predating the project’s construction, called settlement and exchange contractors, which during critically dry years are still able to receive up to 75% allocations under their contracts.

“There’ll be certain areas in the Central Valley that have some water, and there’ll be other areas that really have no supplemental water,” Conant said. “Those farmers are going to have to rely upon groundwater if it’s available.”

Some areas may be able to obtain water transferred from other sources, Conant said. But given how diminished the state’s water supplies are, he said, “we’ll just simply have to fallow a number of acres” and leave some farmland dry.

The reduced water allocations will affect cities in the Central Valley and parts of the Bay Area served by the Santa Clara Valley Water Agency, Contra Costa Water District and East Bay Municipal Utility District.

Water suppliers in Southern California, meanwhile, have been told to expect 15% of their full water allocations this year from the State Water Project.

The Bureau of Reclamation said its initial allocations for the Central Valley Project, which could still change, are based on estimates of how much water will be available from rain, snow and reservoirs. The total amount of water stored in project’s largest reservoirs has dropped significantly over the last year.

“Our reservoirs are at about 27% of capacity, about 52% of the 15-year average,” Conant said.

December storms bought heavy snow to the Sierra Nevada, but the snowpack has since dwindled to 67% of average for this time of year.

And this winter’s biggest storms have brought relatively less precipitation to the watershed that feeds Shasta Lake, the state’s largest reservoir.

Water releases from Shasta Dam provide critical cold water for endangered winter-run Chinook salmon. But last summer, with the reservoir at low levels, the water flowing from the dam got so warm that it was lethal for salmon eggs.

State biologists estimated only 2.56% of the winter-run eggs hatched and survived to swim downriver past Red Bluff, one of the lowest rates of “egg-to-fry” survival in years.

Advocates for the commercial and recreational salmon fishing industries, which depend on the more numerous fall-run Chinook, criticized how officials have managed water releases from Shasta Dam over the last two years.

“We’re likely looking at another year of decimated natural salmon runs due to water decisions that favor a small group of agricultural landowners over the interests of the rest of California,” said John McManus, president of the Golden State Salmon Assn.

McManus and others have criticized what they say have been excessive water releases from Shasta Dam during the drought, which they say left the reservoir too low last year to continue supplying water cool enough for the fish.

“This highlights the need for more responsible drought planning,” McManus said.

Officials with the Bureau of Reclamation have defended their handling of water releases, pointing out that the amount of runoff flowing into Shasta Lake last year shrank to a record low that went beyond their projections.

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