Beneath the almond and citrus fields of the San Joaquin Valley lies an enormous system of aquifers that feeds some of the world’s most productive farmland. Hundreds of miles north and east, along the Nevada border, is the Surprise Valley, a remote, high-desert region undergirded by cone-shaped hollows of sediment that hold deposits of water. Both of these water systems, along with every other groundwater basin in California — a whopping 515 entities — must create individually tailored plans to manage their water use more sustainably. In scale and ambition, California’s Sustainable Groundwater Management Act (SGMA) has few parallels. And the work becomes increasingly urgent as the climate crisis makes water shortages increasingly severe.