California is in the grip of its fourth drought since 2000. To cope with worsening droughts, over the past few decades Californians have made impressive gains in water efficiency. Total water diversions in California for agriculture and cities – roughly 30 million acre feet per year for agriculture and 8 million acre feet per year for cities – have not increased even while California’s population has grown and irrigated farm acreage has increased. But conservation alone cannot guarantee Californians have an adequate supply of water.