The delta is particularly susceptible to earthquake or flood and subsequent levee failure. A water-system break or outage would affect not just Bay Area cities but also San Joaquin Valley farms and most of urban Southern California. This vulnerability is at the heart of the highly controversial $20 billion plan to build enormous twin tunnels around the delta to move water from Northern California to the state and federal water pumps in the south delta. Opponents of the plan worry about its effect on delta communities, farms and fisheries and contend other alternatives would be more cost-effective. But few dispute that the water system as it exists is vulnerable.
San Francisco and the East Bay have made significant investments to improve water pipelines before the next big earthquake. San Francisco and its customers have spent more than $5 billion in upgrades and system redundancies for the Hetch Hetchy system over the last decade. But other potential events, such as drought, could severely affect our water systems.
Long-term trends on the Colorado River, where demand has outpaced supply for more than a decade, have led to historically low levels in the river's principal storage reservoirs - a major concern for Southern California and other Western states that depend on the river. Many of us remember brown lawns and bricks in our toilets from the drought that beset California in the early 1990s. It is only a matter of time until the next extended drought occurs - or has it started already?
In earlier water system emergencies, the East Bay provided supplies through temporary pipelines - to Marin County in the 1970s and to San Francisco in the 1930s. Next time, our neighbors could be short of supply as well.
We have also committed to doing a better job of protecting and restoring habitat for fish and wildlife. These commitments have led to significant changes in how our largest water systems are operated. Los Angeles has given up a substantial portion of supply from the eastern Sierra Nevada as a result of community support and legal action to restore Mono Lake. Legal rulings and political pressure resulting from the collapse of fisheries in the bay-delta, the Central Valley and the Trinity River have forced urban water agencies in Northern and Southern California, as well as some San Joaquin Valley agricultural water districts, to reduce their reliance on water exported from the delta.
Advocates of restoring Hetch Hetchy Valley in Yosemite National Park have not yet convinced San Franciscans or elected officials that restoration should be pursued, even though the water at stake is far less than that involved in the examples described above. But if restoration of Hetch Hetchy Valley does proceed, some additional new water will need to be developed.
Many communities throughout California and the West are taking steps to make their water systems more resilient.
Urban Southern California has invested in numerous local projects, including surface reservoirs for storing imported supplies and groundwater for collecting local runoff. Southern California also is investing more heavily in water recycling than Northern California. San Diego could soon be asking to put its recycled supplies directly back into its potable water system after being fully treated - with public acceptance being perhaps the largest challenge (see sidebar). These are important investments indeed, especially if Colorado River supplies continue to spiral downward.
In the Bay Area, some recent improvements also have been made. The Contra Costa Water District built Los Vaqueros Reservoir in its backyard. The East Bay has invested in an additional diversion point along the Sacramento River at Freeport (Sacramento County).
The South Bay is somewhat less vulnerable to an interruption in imported supplies because it harvests more water locally and has been actively recharging its groundwater basin for the past two decades. San Francisco has improved groundwater management in and near the city, although many of its customers along the Peninsula and in the East Bay have failed to keep up.
Prescient water planning must use all the tools in the toolbox. For the foreseeable future, our cities will still import the bulk of our water supplies But we need to complement these existing facilities with newly developed local surface storage, recharged groundwater basins, recycling and increased water efficiency - all with a cautious eye on the prospect of potentially less dependable rain and snowfall in the years ahead. If we do it right, we will meet future demands, ensure resiliency for our communities and will be able to better protect our rivers and streams.
Spreck Rosekrans is executive director of Restore Hetch Hetchy.