SPOKANE — The era of massive dam construction in the West — which tamed rivers, swallowed towns and created irrigated agriculture, cheap hydropower and persistent environmental problems — effectively ended in 1966 with the completion of Glen Canyon Dam in Arizona.

But a booming population and growing fears about climate change have governments once again studying dams, this time to create huge reservoirs to capture more winter rain and spring snowmelt for use in dry summer months.

New dams are being studied in Washington, California, Oregon, Idaho, Colorado, Nevada and other states, even as dams are being torn down across the country over environmental concerns — worries that will likely pose big obstacles to new dams.

"The West and the Northwest are increasing in population growth like never before," said John Redding, regional spokesman for the U.S. Bureau of Reclamation in Boise. "How do you quench the thirst of the hungry masses?"

Wealth of ideas

There are lots of ideas for increasing water supplies in the West. They include conservation, storage of water in natural underground aquifers, pipelines to carry water from the mountains, desalination plants to make drinking water from the ocean, small dams to serve local areas.

Most of those ideas are much more popular than big new dams.

Gov. Christine Gregoire put together a coalition of business, government and environmental groups to create the Columbia River Management Plan, which calls for spending $200 million to study various proposals to find more water for arid Eastern Washington.

Jay Manning, director of the state Department of Ecology, thinks massive new dams on the main stems of rivers are unlikely. But it is quite possible that tributaries will be dammed, and reservoirs pumped full of river water.

"It is inevitable we will take steps to increase water supply," Manning said. "Storage is part of that solution."

Pressure increasing

Demand for water from growing cities, industry, agriculture and struggling fish runs is already high. Increasing the pressure are fears that climate change will cause rain instead of snow to fall in winter, reducing the snowpack that provides water in summer months.

Gregoire's plan drew the support of many environmentalists by including many ideas they prefer, including conservation measures and metering more uses of water.

But the state is also studying dams, drawing opposition from some environmentalists, particularly a group called the Center for Environmental Law and Policy.

"Our water future doesn't lie with new dams," said Dr. John Osborn, a Spokane physician and chairman of the Sierra Club chapter in Spokane. "It's water conservation."

Osborn contends dam boosters have run a well-orchestrated, under-the-table campaign to push for new dams for the benefit of business, underplaying the costs and environmental destruction and ignoring the benefits of improving water-conservation programs.

But other environmental groups have signed on to the state's bill, although they're leery of the dams. A big reason is that one-third of any new water would be dedicated to survival of endangered salmon.

"What we're trying to do is make sure that before going down that path, and instead of going down that path, we understand what alternatives there are in conservation and water markets and aquifer storage," said Michael Garrity, of the Seattle office of American Rivers.

Washington's water crisis is centered on the Columbia River basin and the adjacent Yakima River Basin — which produce a bounty of crops, including apples, cherries, hops for beer and wine grapes.

Groundwater wells in the region are being emptied to sustain millions of acres of irrigated agriculture, prompting ongoing studies of new dams.

A major barrier to new dams is the cost, running in the billions, Manning said.

A recent study of the Black Rock dam proposal in the Yakima River basin concludes the 600-foot-tall dam would cost $6.7 billion to build and operate, but would return just 16 cents for every dollar spent to build and operate.

The explosive growth of the West in recent decades is in part a product of an earlier binge in dam construction that provided plentiful water and cheap electricity.

The U.S. Bureau of Reclamation built more than 472 dams to capture, store and deliver water, including Shasta Dam in California, Bonneville Dam on the Oregon-Washington border, Fort Peck Dam in Montana and Grand Coulee Dam in Washington.

The construction of Glen Canyon Dam on the Arizona-Utah border, dedicated in 1966, galvanized the rising environmental movement because the resulting creation of Lake Powell inundated a huge swath of scenic land.

But the population of the Western states grew nearly 20 percent in the 1990s, to more than 64 million, and continues to swell even as climate change poses new threats to the water supply.