Despite winter rains and the lifting of urban conservation rules this month, California is still desperate for water. Reservoirs in Southern California are low, and we’re sucking groundwater from the Central Valley.

But what if there’s a vast pool of unidentified water? How much would we use immediately, how much would we save and how would we protect it? Our new study published this week in the Proceedings of the Academy of Natural Sciences concludes that the Central Valley has almost three times more fresh water underground than the state estimates.