Californians are generous to a fault—and it’s a pretty large fault.
A new study by University of California (UC) researchers shows that policies developed in the state over the past 100 years are responsible for surface water allocations that total about five times the amount of actual mean annual runoff.
That’s not a good thing.
“It seems clear that in a lot of these cases, we’ve promised a lot more water than what’s available,” lead author Ted Grantham told the Sacramento Bee. “There’s never going to be enough water to meet all of these demands.”
The study, published Tuesday online in the journal Environmental Research Letters, analyzed 12,000 water rights granted by state agencies since 1914. It compared those grants to streamflow data from the U.S. Geological Survey and found a lot more water was promised to rights holders than exists.
It has long been known that California water rights probably exceeded available water, but the UC study is the first to quantify that. The study found that 16 of the 27 rivers studied had rights that exceeded runoff.
Statewide flow averages around 70 million acre feet a year, while those holding water rights can claim 370 million acre feet. That’s the bad news. The worse news is that the study did not factor in riparian rights granted to streamside landowners before 1914.
“So in many ways our estimate is a substantial underestimate of the total volume of rights,” co-author and UC Merced professor of water resources Joshua Viers told the Los Angeles Times.
It’s only now—with California experiencing a menacing drought and sucking out groundwater much faster than it can be replaced—that the state is beginning to limit the amount of surface water certain rights holders can draw. The UC study seems to indicate that the state has vastly underestimated the cuts that will have to be made.
Grantham, who did the study as part of postdoctoral work at UC Davis, said 80% of the water was controlled by 1% of the rights holders and most of them were government agencies. “We don’t really need to deal with thousands and thousands of water-rights holders,” he told the Bee. “We might just need to deal with a couple hundred that hold 90% of the water.”
Craig Wilson, who oversees water rights in the Sacramento-San Joaquin Delta for the State Water Resources Control Board, says even that won’t be necessary. He told the Bee that many rights holders don’t use the water allocated to them, and a lot of the water that is used ends up back in the rivers. Much of the water rights discussed by the study are connected to rivers and streams that empty into the Delta and the Central Valley.
Wilson’s assertion is impossible to prove because the state doesn’t know how much water is being diverted at any one moment. That goes to the heart of the problem, as explained by UC Berkeley professor of environmental and resource economics: “Without supervision of distribution, appropriative water rights are meaningless: We do not have a coherent system for allocating water.”