Breaking Lower Snake River dams will aid recovery of native fish, new study finds
CORVALLIS, Ore. — A team of scientists, including one from Oregon State University, concluded in a recent paper that the failure of four dams in Washington’s lower Snake River basin provides the best and only reasonable opportunity to promote the recovery of key fish species, including salmon and rainbow trout.
The article, published in the journal Water Biology and Security, examines in detail current fish populations in the basin, past efforts to help restore those populations, and the future impacts of climate change.
“We set out to answer the question of what should be done to maximize the likelihood of recovery of these critical fish species in the lower Snake River Basin,” said Bob Hughes, a courtesy associate professor in the Oregon State Department of Fish and Wildlife. “This analysis has clearly shown that the aggressive action of breaking down roadblocks is necessary.”
Dams have been built around the world to allow humans to store and alter the timing and amount of water released downstream and often to generate electricity. However, there is growing evidence that dams also negatively impact ecosystems.
This has led to an exponential growth in dam failures in recent decades, particularly in North America and Europe. In the United States alone, more than 1,200 dams have failed, most in recent decades.
Breaching is considered a form of river rehabilitation because it can help restore river flows, water temperatures, sediment and particle transport, river and riparian ecosystems, and habitat access by upstream and downstream essential for aquatic organisms to complete their life cycles, said Hughes, an aquatic ecologist for more than 40 years, the last 18 of them in the state of Oregon.
The Snake River Basin in southeastern Washington, northeastern Oregon and Idaho is part of the Columbia River Basin. The Snake River is the largest tributary of the Columbia River.
In the 1960s and 1970s, the federal government built four dams on the Lower Snake River in southeastern Washington to improve navigation, generate hydroelectricity and create recreational opportunities.
Since the completion of the dams, despite considerable efforts to improve the habitat and provide better passage conditions, native fish populations have been and continue to be altered, with many species or populations now threatened with extinction or of disappearance, note the authors of the article.
Nowhere is this decline more evident than in the Snake River Basin, they say. This basin was once home to nearly 50% of the chinook salmon and steelhead trout in the entire Columbia River Basin, which includes much of Oregon and Washington, nearly all of Idaho, and parts of the Wyoming and Nevada.
Today, after decades of attempts to mitigate the effects of the dams, only 1-2% of historic numbers of wild salmon and rainbow trout are returning and all populations in the basin are at risk of extinction or extinction. .
“The weight of evidence that we have described in the paper indicates a strong likelihood that the breach, more than any other measure implemented in the past, promotes a real possibility of rehabilitation,” said lead author Adam Storch. of the newspaper who is an analyst with the Oregon Department of Fish and Wildlife. “This is an especially important consideration given the dire state of many populations.”
In the recent paper published in Water Biology and Security, researchers examined the impact of the failure of the four Lower Snake River dams – Ice Harbor, Lower Monumental, Little Goose and Lower Granite – on the rehabilitation of salmon, rainbow trout, bull trout and white sturgeon. and Pacific lamprey.
For comparison, they looked at research from recent years on the Elwha River in Washington, where dams have been breached and native populations of salmon, rainbow trout, bull trout and of Pacific lamprey quickly rebounded.
They also reviewed research modeling the risk of fish extinction for Chinook salmon and rainbow trout populations in the Lower Snake River under current conditions and if the dams were breached and the spill on the four Lower Columbia Basin dams were rising to facilitate fish passage.
And they considered the dynamics of climate change. The Snake River Basin currently contains 20% of the habitat occupied by salmon and rainbow trout in Pacific Northwest rivers; by 2080, it is expected to contain 65% of the region’s coldest and most climate-resilient riverine habitats that these cold-water species require.
Recent research has shown that even with the potential effects of climate change, much of the habitat in the Snake River Basin will remain suitable for fish. However, under current dam conditions, it is unclear how migratory fish such as salmon and rainbow trout will access these areas without succumbing to warm water stress.
All of these factors led the authors of the paper to conclude that the wealth of credible scientific evidence clearly indicates that the failure of the four lower Snake River dams and more spills on the lower Columbia River dams are needed. to rehabilitate declining populations of salmon, rainbow trout, Snake River salmon. bull trout, white sturgeon and pacific lamprey.
“This rehabilitation would in turn benefit the human populations who depend on these species economically, recreationally and culturally,” they write.
In addition to his position at Oregon State, Hughes is a senior research scientist at the Amnis Opis Institute, a water resource consulting firm. Other co-authors of the article are Howard Schaller, Charles Petrosky, Robert Vadas Jr., Benjamin Clemens, Gary Sprague, Norman Mercado-Silva, Brett Roper, Michael Parsley; Edward Bowles and Jay Hesse.