Not one drop of water need be lost when Hetch Hetchy Valley in Yosemite National Park is restored.
California's drought, now in its fourth year, is serious indeed. Even if wet weather returns, California's chronic overdraft of its groundwater basins is not sustainable over time. The state needs to make systematic reforms and strategic investments to manage its limited water supplies for its homes, businesses, and farms, as well as for its rivers and wetlands. For additional thoughts on the drought and water management solutions, see our "Blame Game" essay from two weeks ago.
Restoring Yosemite's Hetch Hetchy Valley, however, will not affect San Francisco's water rights on the Tuolumne River nor the use of those supplies. The only effect will be the manner in which the water is stored. No other community has built a reservoir in a national park. Alternatives are available to move the storage outside of Yosemite. (See Restoration of Hetch Hetchy Valley and San Francisco's Water Supply, Restore Hetch Hetchy, 2014.)
Hetch Hetchy Reservoir is one of 9 reservoirs in San Francisco's Regional Water System, and accounts for about 25% of its total system storage. It accounts for only 1/8 of the surface storage in the Tuolumne River watershed. Don Pedro Reservoir, located downstream on the Tuolumne River, is owned and operated by the Turlock and Modesto Irrigation Districts but includes a water bank for San Francisco that can hold up to 740,000 acre-feet of water - more than twice the volume of Hetch Hetchy Reservoir.
Importantly, all proposals to restore Hetch Hetchy Valley in Yosemite National Park would provide San Francisco sufficient opportunity to make system improvements to assure no loss of supply.
Over the last 25 years, other California communties have developed more than 1,000,000 acre-feet of dry year supply - more than 18 times the amount of water required to restore Hetch Hetchy Valley - through a combination of surface storage, groundwater storage, water purchases and water recycling programs. These supplies have largely been developed to improve the environmental performance of urban water systems and to reduce the impacts of those systems on California's rivers and wetlands.
Presently, San Francisco simply lacks the political will to make the system modifications necessary to return the Hetch Hetchy Valley in Yosemite National Park to the American people. This needs to change. Not one drop of water need be lost.