Part of the solution to California’s demand for water in the face of the state’s crippling drought may lie 10,000 feet beneath the surface of the state’s Central Valley. New research published in the journal PNAS suggests that the region’s aquifers, areas deep underground where water can collect, have three times the usable groundwater as previously estimated.

“It’s not often that you find a ‘water windfall,’ but we just did,” said study author Robert Jackson, a professor at Stanford University, in a press release. “There’s far more fresh water and usable water than we expected.”