Mismatched: A Comparison of Future Water Supply and Demand for the Metropolitan Water District of Southern California and Its Member Agencies

Even in normal water years, Californians see a large and growing gap between the water we demand and the water that is naturally available. The 2012–16 drought saw surface water and groundwater supplies shrink drastically, sounding a louder wake-up call about the need for more sustainable management of our state’s water resources.

Water agencies in Southern California need consistent assumptions as they consider major investments in water-supply projects, especially given limited state and federal funding. Our analysis shows that the Metropolitan Water District of Southern California (MWD) and water agencies have reached very different conclusions about future water demands and supplies, and they must more closely coordinate long-term water-management planning before making decisions with wide-ranging implications for not only the region but also the entire state.

Despite recent trends toward conservation and efficiency and greater use of local water supplies, the MWD anticipates relatively less investment in local water supplies, continued regional reliance on imported water, and ever-growing demand for water. In particular, the MWD’s projections of future annual water demands are 335,000 to 554,000 acre-feet higher than what is predicted by the local agencies over the next 25 years. On the basis of these higher-demand projections and the expectation of less local water supply, compared to local agencies’ predictions, the MWD anticipates 259,000 to 281,000 acre-feet more in annual imported water sales than the water agencies plan to purchase.