Thomas Harter.

According to the theory, individuals, acting independently and rationally according to each one's self-interest, behave contrary to the whole group's long-term best interests by depleting some common resource. The result for California groundwater in this drought year has been reliance on groundwater to meet fully two-thirds of the state's urban and agricultural water needs.

"It's a significant concern because it's not a rate at which we can continue to use this resource," Harter said. "It's not sustainable."

Here & Now host Jeremy Hobson pointed out that California is the last Western state to regulate groundwater. Last week the California legislature sent three bills to Gov. Brown that would end a commonly held view in California that property owners have the right to draw as much groundwater as they want from wells on their property.

The lack of regulation and a continuing drought have resulted in severe overdraft of the state's aquifer. By studying the state's geology and measuring groundwater levels over decades, scientists know how much water is there, Harter said. Californians should not expect any new hidden reservoirs to be found.

"The best way I think we can address this is make information about the resource more available and let people know what happens to the resource, where (water) comes in and where it goes out, and involve the public on the decision-making on how we want to manage that resource," Harter said.