California's great Central Valley isn't homogeneous

The great Central Valley of California, which stretches from Bakersfield to Redding, has striking differences in rainfall - with the south much drier than the north, wrote George Skelton in his Los Angeles Times column Capitol Journal. The fact is important, he says, because crops growing in the hot dry south take more water than those in the northern reaches.

"You and I are going to drink more water in Bakersfield than in Colusa," said Daniel Sumner, director of the Agricultural Issues Center, a UC Agriculture and Natural Resources statewide program. "Plants can store up more water in the north."

A senior researcher at the UC Davis Center for Watershed Sciences, Josue Medellin-Azuara, calculated that it takes 4 acre-feet of irrigation water to grow an acre of almonds or pistachios in the Tulare Basin, where nut orchards have expanded the most in the last decade. In the rest of the San Joaquin Valley, it requires 3.4 acre-feet. But in the Sacramento Valley, these nuts need only 2.4 acre-feet. That's a difference of roughly one acre-foot, or nearly 326,000 gallons, enough to supply two households for a year.

Skelton said that in past columns he has suggested that the state consider regulating crops based on their water demands and location, but Gov. Jerry Brown flatly rejects that notion, preferring to allow farmers to decide what they want to grow.

The regulating will happen indirectly anyway within the next generation when new groundwater controls are implemented, said Jeffrey Mount, a senior fellow at the Public Policy Institute of California and former director of the UC Davis watershed center.

"That can't happen soon enough," Skelton wrote.

Read more