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Off Stream Gathers Steam
Whatever strategy CALFED selects to fix the problems of the Bay and Delta, the chances are good that it will include increasing the state's water storage capacity. Among the many ways to store water, the one currently getting the most attention involves so-called "off-stream" storage, rather than traditional in-stream reservoirs.
Historically, reservoirs have been created by damming rivers, backing them up to form artificial lakes. In contrast, off-stream storage involves pumping water out of the source river to a man-made reservoir that may be located miles away. Off-stream is likely to be the wave of the future because "there are probably no feasible sites in California for in-stream reservoirs large enough to meet our storage needs," says CALFED's Dick Daniel.
New storage figures in all three of the alternatives proposed by CALFED, the cooperative state and federal effort to meet the state's water needs and restore the ecological health of the Bay-Delta, but how much and where remain big questions. One possibility is to raise existing dams, such as Shasta, to increase their capacity, but this approach can cause significant environmental impacts, according to Daniel. Storing water underground in aquifers is another possibility, also with possible drawbacks. "Large-scale groundwater withdrawals can cause land subsidence," says the Kern County Water Agency's Lloyd Fryer.
Daniel notes that the off-stream approach has a number of advantages. It allows water managers to pump water away from a river during high flow periods and hold it until needed. "It gives us an opportunity to store water with less environmental impact than traditional reservoirs, which disrupt natural flow patterns," says Daniel. It's also preferable to groundwater storage says Kern County's Fryer because "it lets you cycle water in and out of the reservoir rapidly enough to meet peak demand schedules. Cycling of groundwater is slower and steadier."
Another advantage is that intakes for off-stream reservoirs can be located so as to minimize interference with natural processes. For example, Daniel says that CALFED is looking at a possible diversion point on the Sacramento River near the town of Colusa, where levees begin to hem in the river. Above this point the river is still in a relatively natural state, with its flood plain largely intact. "Off-stream storage lets you capture water after it has done its work," says Daniel, adding that three possible reservoir sites near Colusa are the "front-runners for off-stream storage north of the Delta." Other possibilities include the Los Banos Grandes Project near the San Luis Dam and the Montgomery Reservoir, between the Merced and Tuolumne rivers.
Daniel points out that water stored off-stream might be managed differently than in-stream water. For example, Daniel notes that stored water retains heat, which is good for some users, such as farm crops, but not for Delta fish. "The last thing I want is for us to discharge warm water into the Delta," says Daniel. "But we could serve stored water directly to farmers to substitute for cold water coming out of the river." Stored water might also facilitate efforts to restore flows on waterways such as Stony Creek and Thomes Creek. "We could build a ditch to serve the people who have water rights on those creeks with stored water instead," suggests Daniel. The release of stored water can also generate electricity, although the energy gained does not offset the amount used to pump the water to the reservoir in the first place.
Several off-stream facilities are already in the works, like Contra Costa Water District's Los Vaqueros Reservoir, which will be dedicated this May (see calendar), and the 800,000 acre-foot Eastside Reservoir under construction near Los Angeles. Indeed CALFED has been looking into an expansion of Los Vaqueros, which was constructed to provide better, not more, water to Contra Costa Water's customers. "Our water allocation is the same as it was before-195,000 acre-feet-but we will be able to take it from a different part of the Delta," says the District's Ed Novi. The new intake at Old River, which is equipped with state-of-the-art fish screens, avoids the salinity problems that plagued the old intake at Rock Slough during dry periods. The flexibility provided by the extra storage also helps to protect fish. "During the spring spawning period we will shut down all pumping and serve our customers using stored water," says Novi.
Daniel cautions that since off-stream storage requires flooding habitat, it is by no means environmentally benign. There are also big operational questions, says the Bay Institute's Peter Vorster. "How high do river and Delta flows need to be before we can safely start diverting and storing?" he asks.
And then there's the cost. Daniel estimates that new water supplies, including stored water, will cost $300-$400 per acre-foot, and others believe the costs could be much higher. "We should look at it only after more cost-efficient alternatives, such as conservation, water transfers, acquisition and conjunctive use have been exhausted," says Vorster.
Governor Wilson's proposed $1.3 billion water bond includes funding for off-stream storage feasibility studies. Environmentalists oppose the funding on the grounds that it predetermines CALFED's decision on storage. Furthermore, says Vorster, agriculture would be one of the big beneficiaries of new storage, and "we don't think that public money should be used to subsidize agriculture's environmental obligations." Although he does not dismiss off-stream storage as an option, Vorster says "the big questions are where in the game do you introduce it and who pays?"
Contact: Dick Daniel 916)657-2666 or Peter Vorster (415)721-7680
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