Despite the environmental claims made by proponents, not everyone is embracing new off-channel projects. This spring, the plans for Glade Reservoir landed the Poudre on American Rivers' list of most endangered streams.

Glade is "the same (as any dam) in terms of impact to the flow regime," says Mark Easter, a spokesman for the Save the Poudre coalition. Although Glade is supposed to bolster low river flows, some worry that its diminishing effects on high flows could threaten plans for a new kayak park.

Easter is also doubtful about the agricultural benefits. A draft environmental impact statement says that constructing Glade would save 33,600 to 69,000 acres of farmland from development and the loss of water rights. But Easter calculates that the reservoir would make it possible to build at least 20,000 acres' worth of new subdivisions and encourage breakneck growth so towns could repay their debts.

Up in Washington, the environmental benefits of Black Rock appear to pale in comparison with its costs. According to the draft environmental impact statement, the project would provide only about 16 cents in benefits to fish and farmers for every dollar spent. That doesn't include regional economic growth and tourism, but the skewed cost-benefit ratio has united reservoir opponents.

Phil Rigdon, the Yakama Nation's deputy director of natural resources, says the tribe is not opposed to a new reservoir. But his agency is skeptical about Black Rock's potential for salmon restoration. More significant habitat improvements and new fish-passage devices on the existing dams would also need to be built before the release of water from Black Rock could help salmon, Rigdon says. "We're saying you need a full package; otherwise, don't sell it as a fish project."

The Yakama have joined the Roza Irrigation District in advocating a more modest water-storage project   -- one that won't saddle locals with a multibillion-dollar debt. The possibility that reservoir water could seep into the toxic mess underneath the nearby Hanford Nuclear Reservation is also a concern that has prompted more BuRec studies.

All these issues recently led the state of Washington, which has shared the costs and workload for the studies, to resign from the federal planning process. Derek Sandison of the Washington Department of Ecology says that although the state hasn't abandoned Black Rock, it is taking a closer look at smaller alternatives. It's also considering aquifer storage and recovery, in which water is diverted and stored underground to reduce evaporation.

There are also growing worries over how much global warming will increase drought and reservoir evaporation rates. When water managers acknowledge global warming, they often use it as a reason to build more reservoirs. Sid Morrison cites studies that predict the Yakima Valley could see water losses of up to 40 percent by 2050. "Two years (of drought) back-to-back," says Morrison, "and the (fruit) trees are dead."

But a February 2008 article in the journal Science casts doubts on this strategy. Because reservoirs and their water sources are geographically locked in place, changes in climate could make it very difficult to keep them full.

"Most of these projects are really expensive and, with what we know now about climate change, the old rules don't apply anymore," says Brad Udall, director of the Western Water Assessment at the University of Colorado, Boulder. "The (model of the) 20th century is no longer adequate to project the future" of water supply and storage.

Federal agencies are expected to complete final impact statements for both Black Rock and Glade reservoirs around the beginning of next year.

Black Rock opponent Michael Garrity, who works in American Rivers' Seattle office, doubts that the project will be approved. But if it is, he sees an unlikely silver lining: Because Black Rock would cost so much, and yet fail to meet the needs of fish and farmers, he says, "It could be a setback for other people who want to build dams in the West."

This article was made possible with support from the William C. Kenney Watershed Protection Foundation and the Jay Kenney Foundation.