Aug. 20 — California's historic over-allocation of water rights and inaccurate accounting of how those rights are being exercised make it difficult for regulators to enforce curtailment orders when supplies are scarce, according to a new study by University of California researchers.
The study confirms past analyses of the state's water rights database. This assessment, however, takes a closer look at the data, providing a spatial distribution of the post-1914 appropriation of surface water and identifying entities that hold the most water rights, which the authors said could inform needed reforms to water right policies.
Published Aug. 19 in the journal Environmental Research Letters, the study found that over the last century, California has issued rights to five times more surface water than is available in a year with average runoff. Annual freshwater flow averages 70 million acre feet, but the state has allocated rights for 370 million acre feet, the study said.
Rights to water on 16 of the state's 27 major rivers exceed natural supplies, the researchers said. The most over-allocated are the Sacramento and San Joaquin rivers and their tributaries and Southern California coastal streams.
Ted Grantham, the lead author of “100 years of California's water rights system: patterns, trends and uncertainty,’’ told Bloomberg BNA Aug. 20 that the analysis showed that the top 1 percent of water rights holders accounts for more than 80 percent of the total volume of allocated water.
Also, while individuals and private corporations hold most of the water rights, most water, by volume, is allocated to public entities, Grantham said.
“To me, that suggests that reallocating or restructuring water rights would involve a couple of hundred key actors and most certainly not private individuals,’’ he said.
Grantham conducted the research as part of post-doctoral studies at the University of California at Davis with co-author Joshua Viers, a professor of water resources at the University of California at Merced.
California's appropriative water rights, which the State Water Resources Control Board oversees, “incentivizes permit holders to over-report water use to protect the face-value amount of their water right and therefore represents a generous estimate of actual water use,’’ the study said. Also, return flows to rivers and canals can be reused, which can lead to double-counting of the same volumes of water, the study said.
The authors also said their analysis looked only at the post-1914 appropriative water rights, not the riparian claims, which make the total amount of surface water allocated significantly higher.
“In a well-functioning appropriative water rights system in which allocation volumes are accurately tracked and verified, over-allocation of water supplies is not necessarily a problem,’’ the study said.
“During periods of water scarcity, junior appropriators have to forego their entitlement,” the study said, “but when water is abundant, most water rights holders should be able to exercise their claims.’’
The study said California's system “is ill-equipped to satisfy growing societal demands for water supply reliability and healthy ecosystems.’’
The state lacks accurate knowledge of how much water is being used by most water rights holders. With accurate water use information, the blanket curtailment orders regulators have issued during the current extreme drought wouldn't have been necessary, the study said.
Satisfying new demands for water will likely require reallocation of existing water rights, the study said.
California's water laws allow for reallocation of rights to manage water resources, but additional public investment is necessary, the study said.
In issuing curtailment orders, the SWRCB has requested information on water use. Many of the requests are still outstanding, officials told the agency's governing board at an Aug. 19 meeting.
“While we continue to implement water rights law and regulation under our established system, we are receptive to learning from other parties' findings regarding allocation of water in post-1914 water rights and their ideas on how to improve our processes,’’ Amanda Montgomery, a water rights manager at the water board, said in an Aug. 20 e-mailed statement.
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