Every September in south-central Washington, the gates of Tieton Dam open and the Tieton River pours through. More than a half-million gallons of water flow each minute for 45 days. The sudden and sustained surge sends the river raging and frothing through the Yakima Basin, brimming against its banks with the kind of force that fuels whitewater rafting businesses and earns mentions in travel guides. 

This man-made flood was born from the best intentions. In 1980, the U.S. Bureau of Reclamation found itself taken to task - and to court - by the Yakama Nation for allowing culturally and religiously significant spring chinook salmon runs to decline. Forced by a federal court decision to develop a way to manage water that would help Yakima River spring chinook recover, fish biologists invented the system called "flip-flop," which alternates flows in the Yakima and Naches rivers to serve both farming and fish. And for a while, it seemed to work: Farmers got their water in the key late-summer and early-fall dry periods, and the spring chinook rebounded, albeit modestly. 

But the compromise was paid for by the Tieton, a tributary of the Naches. The river's artificial lows and highs make survival difficult for its native steelhead, a species now listed as threatened under the Endangered Species Act. "We did this to the Tieton so we wouldn't continue to do what we were doing to the Yakima chinook," says Dale Bambrick, the eastern Washington branch chief of the National Marine Fisheries Service. "We've turned this river into a biological desert." 

And new research suggests flip-flop may also take an unexpected toll on the Yakima spring chinook, the very fish it was designed to protect. Faced with the possible failure of the system, the Yakama Nation, the irrigation districts, and the federal and state agencies that regulate Yakima water and wildlife - once fierce opponents - must now work together to decide the future of the basin's fish. 

The Yakima Basin is a green blot in a rolling, rainless sagebrush landscape, its 500,000 irrigated acres famous for fruit, hops and wine grapes. The basin flourishes thanks to elaborate waterworks: the Yakima and the Naches and their tributaries, plus six reservoirs, dams, irrigation channels and the flip-flop system. 

For the century before the 1980 court decision, business as usual meant fish were a "fleeting" thought for the Bureau, admits Bureau biologist Scott Kline. Rivers were run primarily for irrigation; once the irrigating season ended in October, dam gates closed and rivers dried to save water for next year. 

"Every single salmon nest was killed, and any fish out there rearing was killed," says John Easterbrooks, regional fisheries program manager for the Washington Department of Fish and Wildlife, who has worked in the basin for 30 years. "They turned it on and off like a faucet." 

The dams and fluctuating flows pushed the basin's seagoing, or anadromous, salmon population - which once included sockeye, coho, chinook and steelhead - to extinction. Sockeye succumbed to dams within four years of their construction, while overfishing and development extirpated the coho by the 1970s. The changing flows destroyed chinook eggs, eliminating summer chinook and drastically reducing spring chinook numbers. 

Salmon spawning in high flows sometimes made their nests, or "redds," in riverbed gravel near the shores. These redds then dried up in winter, when the water levels dropped so low that much of the riverbed was exposed. By the late 1970s, spring chinook salmon, so named for their springtime return from the ocean, had dwindled from hundreds of thousands of fish to a few hundred. 

When Bob Tuck went to work for the Yakama Nation in 1979, he was the only anadromous fish biologist in the basin. "The feds and state had given up on eastern Washington," he says. "Those were pretty desperate times." 

In October of 1980, Tuck was out looking for redds on the Yakima River when he witnessed firsthand how reduced water flows expose redds and kill eggs. "The river was literally dropping out from under me," he recalls. He ran to a nearby home and used the phone to call the Bureau. "I told them, 'Stop what you're doing.' And that drew some attention." 

It also spurred the Yakama to action: The tribe took the Bureau to court over its treaty-guaranteed fishing rights, and won. U.S. District Court Judge Justin L. Quackenbush ordered the Bureau to protect the redds and put a committee of local fish biologists - including Tuck and Easterbrooks - in place to advise them. The rest was up to the Bureau. 

After months of contention between the tribe, the committee, the Bureau and farmers, flip-flop began. From April to September, the Bureau would continue, as it had for decades, to release reservoir water into the Yakima River for diversion into irrigation channels downstream. But in September, when the spring chinook spawn, the agency would ramp down the Yakima's flow to force the salmon to make their redds lower in the stream, where they would remain water-covered through the winter. Simultaneously, the Bureau would ramp up flows on the Tieton, creating a torrent that would then flow into the Naches and downstream for irrigation. 

This meant sacrificing the Tieton, which was already damaged by highway development and the construction of Tieton Dam and its reservoir, Rimrock Lake, in the 1920s. The Tieton was smaller than the Yakima, with a steepness and a propensity to flash flood that made it inhospitable to spring chinook. Tuck, who grew up in the Yakima Basin and wrote his master's thesis on its fish, remembers it running bone-dry in winter, bereft of chinook. 

"We wrote (the Tieton) off as a fish producer in exchange for lower flows in the Yakima," Easterbrooks says. "We thought we weren't losing a lot, creating flip-flop and sacrificing the Tieton." 

What they were losing, however, were steelhead trout. They just didn't know it yet. 

"The Tieton is a big piece of real estate - just because you don't see fish doesn't mean they're not there," Bambrick notes. "Before the dam, the Tieton had one of the most important steelhead populations," and even after the dam was completed in 1925, steelhead may have still numbered in the hundreds. 

When the extreme flows of flip-flop began, they flushed out young steelhead in the Tieton and, to a lesser extent, the Naches, along with the seeds of cottonwoods and other riparian plants and the aquatic insects on which steelhead depend. What Kline likes to call "the food of the river" was gone, and the steelhead with it. 

But spring chinook, not steelhead, were the basin's concern - until 2000, when steelhead were listed as threatened. The listing prompted a review of flip-flop. As required by the Endangered Species Act, the Bureau submitted a new biological assessment and plan for water management in the Yakima Basin to the National Marine Fisheries Service in 2003. NMFS responded with a biological opinion that asked the Bureau to recognize the extent of flip-flop's impact on steelhead and to either tweak the alternating flows for their benefit or help with other recovery efforts. But persistent disagreements with the Bureau meant that the biological opinion was never signed or made public. "We concluded, 'That's bad,' " says Bambrick, "and the Bureau concluded, 'So what?' " 

Its impact on steelhead aside, flip-flop may not be the best way to protect spring chinook either. Armed with nearly 30 years of data - a luxury Tuck and Easterbrooks didn't have - Steve Cramer, an independent fisheries consultant hired by the irrigators, has found that the alternating water flows on the Yakima River protect spring chinook eggs at the expense of stable habitat in which the salmon can grow once they hatch. Despite the Bureau's efforts to moderate Yakima flows, the summer's releases disrupt plant and insect life and make natural shelters for juvenile spring chinook scarce. The Yakama Nation's most recent annual salmon count turned up 2,495 returning wild spring chinook in a river system that historically may have seen 200,000. Cramer's report suggests those numbers won't increase until fish and water managers strike a better balance between protecting redds and protecting rearing habitat, which might mean modifying or doing away with flip-flop. Until then, says Yakama Nation biologist Mark Johnston, spring chinook are "just hanging on." 

In Washington, as in the rest of the world, no environmental story is complete without climate change. A 2005 study by scientists at the Pacific Northwest National Laboratory in Richland, Wash., estimates that Yakima Basin water available for irrigation will drop 20 to 40 percent by midcentury due to global warming. 

The finding supports what Stan Isley, a specialist with the Washington State Department of Ecology Water Resources Program, has long suspected: No amount of water conservation or tinkering with flows can keep both farming and fish healthy in the Yakima Basin - not without water from somewhere else. 

Jack Stanford, a University of Montana ecology professor with an abiding love for the basin, agrees. That's why he proposes pumping water from the nearby Columbia River directly into the region's irrigation channels, supplying farmers while bypassing the river system entirely. It's a streamlined version of another proposal, the Black Rock Project. Currently under study by the Bureau, the billion-dollar plan would store Columbia River water for both irrigation and fish in a massive reservoir just east of the basin. Although the basin's farmers have been calling for more water storage for 50 years, the project's price tag and potential impact continue to raise concerns. 

For now, Bambrick, Johnston and their colleagues are tying their hopes to more mundane developments. After a four-year stalemate, new blood in the Bureau has brought a new willingness to work with the NMFS. Representatives from the two agencies, the Washington Department of Fish and Wildlife, and the Yakama and agricultural communities plan to meet regularly in the coming year, to work on a revised biological assessment due early next summer. Bambrick and his colleagues hope the resulting plan and biological opinion will mean relief and restoration for the Tieton, and more protection for all the basin's fish. 

In the end, it may come down to the Yakama Nation. As the tribe balances the rivers' health with its own irrigation districts and plans for development, it stands to win or lose in ways that "transcend history or economy," says Stanford. For the Yakama, the whole river system matters, and both their livelihood and their identity are at stake. 

"This is who we are as a people," says Phil Rigdon, the deputy director of natural resources for the Yakama and a member of the tribe. "People make this into an environmental issue. But it's a people issue. Why is one economy more important than the other? Ours was the first economy." 

The author is a freelance writer based in Tucson, Arizona.