Researchers said Tuesday that California has overdrawn its water account and has been draining it for a century.
UC Merced Professor Joshua Viers and former UC Davis researcher Ted Grantham, now with the U.S. Geological Survey, drilled down into the state’s database of water-rights allocations.
Viers said they found the allocations exceed the state's actual water supply by five times the average annual runoff and 10 times the actual surface-water supply for some river basins.
"Just the fact that we've, on paper, appropriated about five times the amount of water that we might have available was a very interesting finding,” said Viers, who is director of the Center for Information Technology Research in the Interest of Society at UC Merced.
Viers said the state has about 70 million acre feet of surface water available for use. And, based on active water rights records, a total of 370 million acre feet have been allocated.
He said there are far more people who hold rights than there is water.
"In many cases we've allocated five to ten times the amount of water that might be in a river by the time you get to its outlet such as the California Bay Delta system," said Viers.
Viers said with continued drought, California needs to overhaul the way it accounts for water use.
He said the water-rights system is complicated, groundwater use is not regulated and the state needs a unified system to monitor and accurately track surface and groundwater in real-time.
"At present, water reporting is voluntary," Viers said. "Unfortunately, there is a perverse incentive to estimate that you're using your full allocation in the event that if you weren't using it, it might be given away to someone else. So we need to create a system where we know how much water is available, what is it being used for and by whom."
Viers said all those allocations mean that in times of drought, it’s hard to tell who should have to reduce "water extraction."
"We're now at a position within the state of California that if we're going to maintain our position as the ninth most prosperous economy in the world, we're going to have to do a better job of managing our water resources," said Viers.
Viers said the researchers are now working with state water managers, including the State Water Resources Control Board, to develop analytical tools to allocate water demand based on availability.
Read the study: http://iopscience.iop.org/1748-9326