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What’s Next for California’s Water Supplies as the Rainy Season Comes to an End?

Author: Jessica Diaz

Editor: Amy Steinfeld

The conclusion of California’s five-year drought was undeniably dramatic. The recent Sierra snowpack survey by California’s Department of Water Resources showed water content 196 percent above the long-term average. The 2017 water year was the wettest on record for Northern California. And in April, the governor lifted California’s declaration of drought emergency.

Yet this immediate-term relief should not obscure the stark reality: California suffers a long-term deficit in water supply. The state’s population is projected to increase from an estimated 39 million in 2016 to 52.6 million by 2060. The U.S. Bureau of Reclamation projects that by 2030, California will face 5 million acre-feet of total unmet water demand in an average year, and even more in a dry year. This is equivalent to the average annual use by 10 million households.

This shortfall is of particular concern to communities that rely heavily on two primary sources of imported water: the Colorado River and the State Water Project. The U.S. Bureau of Reclamation’s most recent assessment of the Colorado River Basin projected a long-term imbalance between supply and demand of 3.2 million acre-feet per year by 2060. As noted in a recent report by the Colorado Water Institute, National Science Foundation, the National Oceanic and Atmospheric Administration and the U.S. Geological Survey, shortages of Colorado River water will only increase as temperatures continue to rise and “mega-droughts” lasting 20 years or longer become more likely. The State Water Project will face similar shortfalls: a 2015 reliability report indicated that long-term average deliveries would meet only 62 percent of the total contracted amounts, and only 28 percent to 33 percent of demand in a multiyear dry period.

Groundwater supplies also face long-term strain. DWR has been estimating that overdraft is between 1 and 2 million acre-feet per year. The Sacramento and San Joaquin River Basins collectively lost over 16 million acre-feet between October 2003 and March 2010, with even more significant losses during the recent drought.

Rather than heralding an “end” of drought, the most recent rainy season highlights what is likely to be the new normal: a continued cycle of drought-to-deluge, with a long-term deficit in key sources of supply. As a result, it is increasingly important for state and local water agencies to account for these new precipitation patterns and demand projections in every aspect of water planning.



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