It appears California has given away rights to far more water than it actually has. 

UC Merced Professor Joshua Viers says the numbers just don't add up. 

"Out of those 32,000 different water rights, they sum up to about 370 million acre-feet, and in a good year, California has about 70 million acre-feet," Viers said. 

According to those numbers, California has allocated five times more surface water than the state actually has. 

"What's also innovative about this study is that we can look at individual river systems, and in some cases we've allocated 10 times, or 1,000 percent, of that full natural flow," Viers said. 

Viers says you can't manage what you don't measure.

Better information might enable state regulators to better target water cutbacks in times of drought.