The mighty are falling. Right now, they're toppling one after another — those dams and dikes that have altered the natural flow of Northwestern waters for the past century.

Consider: On October 9, the 500-foot-long earthen Savage Rapids Dam, which had blocked the lower Rogue River since 1921 bit the dust. A week before, contractors breached the last of the dikes that had kept Puget Sound tides from most of the Nisqually River estuary since the turn of the 20th century.

Next year, PacifiCorp will take down its 125-foot concrete Condit Dam, which has blocked southwest Washington's White Salmon River just north of the Columbia Gorge since 1913. The Elwha dams, which have kept salmon from the watershed that forms 20 percent of Olympic Natonal Park since long before the park was created, will start coming down in 2011. And 25 government agencies, state governments, tribes, and interest groups have agreed with PacifiCorp on a process that may lead to removal of four dams that have blocked the Klamath River for most of the past century.

These are not minor projects. The Nisqually project is the biggest estuary restoration in the Northwest. The Condit project will be the biggest dam removal in the United States, and the Elwa dam removal will be even bigger. And the Klamath? “When the Klamath dams come down it will be the biggest dam removal project the world has ever seen,” said Steve Rothert of American Rivers. Rothert, whose group was at the negotiating table, said that when the dams come down, “we will be able to watch on a grand scale as a river comes back to life.”

Need more? Some environmental groups also hope that the Klamath agreement points the way toward a decision to breach the lower Snake River dams.

As you can easily imagine, the factors in such massive alterations of the landscape cut in many directions. That has meant environmental groups are lined up on opposing sides of some of the disputes.

Take the Klamath River, for starters. Virtually no one claims that taking out the Klamath dams would be a bad idea. But will the Klamath agreement hold up? That remains to be seen. And would the benefits of dam removal outweigh the environmental costs imposed on the Klamath Basin by the agreement? Some environmental groups say they won't. They argue that if you're fixated on the welfare of salmon and the principle of dam removal, then you may not look too closely at the price tag. If price is a consideration, though, you may decide that the rewards are too uncertain and the known costs are too high.

PacifiCorp owns the Klamath dams, the first of which went up in 1918, the last in 1962. The company itself, which operates in Washington, Oregon, California, and Utah, is owned by MidAmerican Energy Holdings Company, which in turn is largely owned by Warren Buffett's Berkshire Hathaway. It had been owned by Glasgow-based Scottish Power. But representatives of the Hoopa Valley, Yurok, Karuk and Klamath tribes demonstrated against the dams' effect on Klamath River salmon outside the company's annual meeting in 2004, and the next year, Scottish Power unloaded its American subsidiary.

Federal licenses to operate the dams expired in 2006, and more than a decade ago, PacifiCorp started the relicensing process. NOAA Fisheries and the U.S. Fish and Wildlife Service insisted that the company install fish ladders. The California Energy Commission, the Interior Department, and FERC concluded that if fish ladders were the price of relicensing, PacifiCorp and its customers would save money if the utility just took the dams down.

The Hoopa Valley tribe, which occupies a reservation along the Klamath's largest tributary, the Trinity River, northeast of Eureka, would love to see the Klamath dams come down. But the Hoopas don't like the proposed agreement. Seattle attorney Tom Schlosser, who represents the tribe, explains that “it's not a dam-removal agreement. It's a planning process.”

Dam removal is discussed as a done deal, but that's not what the agreement says. For openers, members of negotiating groups have yet to ratify it. If the agreement goes forward, it requires the Secretary of the Interior to decide in 2012 whether or not the benefits of dam removal would outweigh the costs. If he decides they would, dam removal could start in 2020, but there are many other contingencies. The states of Oregon and California can back out. The whole agreement is linked to a complex settlement of disputes over water in the Klamath Basin, upstream from the dams. Such settlements would require Congressional blessing — and a Congressional appropriation of $985 million. Schlosser doubts all this is going to happen.

Without the agreement, FERC could tell PacifiCorp to take down the dams. With the agreement in place, however, FERC will effectively be unable to do that. The utility “has gotten the parties to agree that it will take an act of Congress to remove those dams,” Schlosser says. “They've gotten themselves thrown into the briar patch.”

American Rivers' Steve Rothert acknowledges that the agreement is “not a guarantee.” He says “American Rivers would prefer that dam removal was certain and sooner.” However, he says, “we are confident . . . that removal will be determined to be in the public interest and will happen.” The biggest hurdle, he notes, was getting all the participants to agree. With that accomplished, “there are no real show-stoppers to date.”

Assuming the dams will eventually come out, PacifiCorp can keep operating them, with no significant operating changes, for more than a decade. Critics say the utility is getting a long free pass. They also point out that the agreement does not help fish that try to spawn in the Klamath's tributary Shasta and Scott rivers, which are virtually sucked dry to irrigate farms in central California. “The Scott and the Shasta rivers are basically de-watered,” says WaterWatch of Oregon's executive director John De Voe. “This deal won't do a damn thing to address those problems.”

The deal also locks in allocations of water and money that critics say will prevent rational water management in the Klamath Basin for another 50 years. Oregon Wild conservation director Steve Pedery says it will “cement Bush priorities in the basin.” (The Bush administration's approach to the basin had less to do with helping farmers grow potatoes than with helping Karl Rove grow votes.)

The Klamath Basin made national headlines in 2001, when the Bureau of Reclamation had refused to let water flow to its Klamath irrigation project. The Bureau was under court order to protect two endangered species of bottom-dwelling fish called suckers, which inhabit Upper Klamath Lake and several smaller local water bodies, as well as a threatened population of coho salmon that spawns in California tributaries of the Klamath River. The farmers who raised potatoes, alfalfa, and other crops on the 220,000 acres of the federal irrigation project had already borrowed money to plant this year’s crops. They were left high and dry. That May, a “bucket brigade” drew an estimated 12,000 people to Klamath Falls. Protesters chainsawed the locks off the headgates and let water flow into the irrigation canals. They also laid pipe around the headgates. In August, a caravan of sympathizers from towns all over the west arrived in Klamath Falls bearing food for the local farmers.