One of the shocking truths to emerge from California’s continuing drought is this: the state has no idea how much water it has. Nor do its leaders have a clear idea how much water is actually diverted by users, what it is used for and how much is left over. “It’s kind of surprising how little we know about some of these issues,” said Alvar Escriva-Bou, a research fellow at the Public Policy Institute of California. “There is much room for improvement.”