Water is vital to the health of our economy and natural ecosystems. California’s cities and agricultural communities depend upon reliable supplies of clean and adequate freshwater. As California’s population and economy grow, there is mounting concern about our ability to meet future water demand amidst pressure on our complex water systems. In the 20 th century, our approach to meeting this demand was to develop new supply by tapping our rivers, streams, and groundwater aquifers. While this approach brought tremendous benefits to the state, it also came at enormous environmental cost. We are reaching the economic, ecological, and social limits of traditional supply options: continuing to rely solely on building new infrastructure will fail to solve our impending crisis. We must expand our thinking about supply, away from costly new dams and toward other options for expanding supply (eg, recycled water, stormwater capture, and integrated groundwater banking and management) and reducing statewide water demand. There is no “silver bullet” solution to our water problems, as all rational observers acknowledge. Instead, we need a diverse portfolio of solutions. But the need to do many things does not mean we must, or can afford, to do everything. We must do the most effective things first.

In particular, there are tremendous opportunities to improve the efficiency with which we use water at lower economic and ecological cost than developing new supply. There is vast potential to reduce our demand for water without affecting the services and benefits that water provides. Improving efficiency offers many benefits. Conserved water can be reallocated to other uses by the same user, such as growing more food on a farm. It can be left (or returned to) ecosystems to help restore natural water flow levels. It can be moved from one user to another as part of an economic arrangement or transfer. In addition, reducing the application of unnecessary water can save energy, reduce wastewater and associated treatment costs, and eliminate or delay the need for new water supply and treatment infrastructure. Water management efforts and programs should explicitly work to assure such co-benefits.