Lower Snake River Dam ©EcoFlight
By Jennifer Yachnin
09/13/2024
Federal and state officials plan to spend the next year figuring out how to address the “heat pollution” in the Lower Snake River, ratcheting down summer water temperatures in a bid to bolster a struggling population of fish.
Flows in the 140-mile stretch of river in southeastern Washington state regularly spike above 70 degrees Fahrenheit in the summer months. The warm water creates unfavorable conditions for migrating salmon and steelhead, further complicating an already arduous journey that many will not survive.
This plan won’t address what all agree is one big factor contributing to the hot water: four dams that tribes and environmental advocates want to see come down. Instead, the Army Corps of Engineers, which operates the dams, and the Washington State Department of Ecology, are searching for other ways to put the region on a "temperature diet."
Those efforts could result in lowering the levels of some or all of the four reservoirs at different times, among the options to speed water through the system to keep temperatures within acceptable ranges.
"It's not as simple as pressing a button and dropping the temperature of the river. There are limited ways to go about reducing water temperature," said Miles Johnson, the Columbia Riverkeeper's legal director.
In the meantime, the Biden administration, Washington and Oregon and four tribal nations are contemplating how that portion of the river could be returned to a free-flowing state, which would require winning congressional approval to breach the Ice Harbor, Lower Monumental, Little Goose and Lower Granite dams. While that would help cool down the water, tearing down dams is unlikely to happen anytime soon, given intense Republican opposition to the idea and the region’s current reliance on the hydropower they generate.
The effort to tackle Lower Snake River temperatures is the result of a legal battle launched by Columbia Riverkeeper and other organizations, which sued the Army Corps in 2014 alleging the agency was discharging "oil and heat pollution" into the river without Clean Water Act permits. The effort focused on both oil leaks into the river from turbines and other components of the hydropower facilities, as well as the discharge of used "cooling water," or flows used to lower the temperature of the facilities.
While salmon and steelhead throughout the Columbia River Basin have been on the decline for decades, several Snake River species are in particular peril, listed under the Endangered Species Act as either endangered or threatened.
The 9th U.S. Circuit Court of Appeals upheld a victory for the environmental groups in 2019, prompting an EPA evaluation of the rivers that dictated temperature reduction targets for each of the reservoirs.
The target for the Lower Snake River, formally known as the temperature “total maximum daily load” (TMDL), is set at a maximum of 68 degrees Fahrenheit to ensure salmon and other fish can lay eggs, spawn and migrate.
The Army Corps issued its "Water Quality Attainment Plan” to achieve those temperature goals earlier this year but that proposal was rejected by the Washington State Department of Ecology in June, because it "fails to include necessary details of the water quality temperature goal and potential actions."
State officials criticized the plan’s contention that the Army Corps is already meeting some requirements through its current practices, such as injections of cold water from an Idaho reservoir.
In response, the Army Corps said it will aim to revise its plan over the course of the next year, led by a working group that includes state officials and tribal representatives, along with federal agencies including EPA, the Bonneville Power Administration, Bureau of Reclamation, NOAA Fisheries and the Fish and Wildlife Service.
“The Corps is committed to implement temperature control strategies and meet the load allocations in the Columbia and Lower Snake Rivers Temperature TMDL,” the agency wrote in an August letter. “While the Corps has analyzed and implemented multiple water temperature improvement actions over the years, the work is not done.”
Coming in hot
Although the dams contribute to the temperature problem, the Snake River is already vulnerable to running hot.
Flowing from the eastern slopes of the Cascade Range, the Lower Snake River collects warm water as it flows through an area on the Idaho and Oregon border.
That includes water from the Salmon River, an undammed, mostly wilderness area, that spiked to a high of 76 F this summer, said Chris Peery, a fish biologist in the Army Corp’s Walla Walla District.
“There's no way to control or moderate these temperatures,” Peery explained. “But that's just normal temperatures now that… with climate change, we are getting lower flows in the system and warmer weather.”
The warm water creates a challenge for migrating salmon, which will halt their migration when water temperatures rise above 68 F, or what scientists refer to as a “thermal barrier.”
But pausing a salmon’s journey can be particularly risky, since most salmon stop feeding once they enter fresh water and rely solely on fat stores for their journey to spawning grounds.
The endangered Snake River sockeye salmon faces a particularly tough journey, traveling nearly 900 miles from the Pacific Ocean to the Sawtooth Valley lakes in Idaho, which is at an elevation of 6,500 feet.
But Peery notes that the warm water feeding into the river would create a challenge for water managers even if the Lower Snake River dams were to be removed.
“This area gets hot in the summertime. It always has gotten hot in the summertime,” Peery said, noting that historic temperature data for the region is limited in the decades before the federal government built the dams in the 1960s and '70s.
Among the few records available, he pointed to data from the late 1950s that shows water temperatures in July and August at or above 75 F.
“If, for example, we could wave a magic wand and take out the dams today, we would still see temperatures like this in the Lower Snake River, especially with documented warmer weather,” Peery said.
But Chad Brown, a supervisor for Water Quality Management in the Washington State Department of Ecology, said that while high temperatures do naturally occur in the river, storing water behind dams creates additional heat and maintains those temperatures for a longer period of time.
“Although those temperatures may get higher naturally without the dams, it’s the magnitude and the duration that the fish are exposed,” Brown said.
Brown added that his agency is focused on how to improve the region’s temperatures incrementally.
“What we're asking for is that methodical process to ensure that we're looking at all different options and really looking at those that are reasonable and feasible,” Brown added.
He pointed to the potential for “selective withdrawal” from reservoirs, in which water is funneled through a structure’s lowest outlets to tap the coldest available flows, rather than solely through hydropower facilities that sit higher up.
Finding balance
The Army Corps currently relies almost exclusively on water from behind the 717-foot tall Dworshak Dam — located to the east in Idaho — to moderate temperatures in the Lower Snake River.
“The water that comes out of Dworshak is 42 degrees year round,” Peery said, and later added: “It's a very valuable resource, but it's kind of the one-trick pony. Once we release it, it's gone, and we won't be able to replace that water again until the next flood season, next spring runoff, and so it has to be managed really closely.”
The releases from the Dworshak reservoir can account for as much as one-third of the overall water in the Lower Snake River in the summer months, lowering the river’s temperature an average of 2 to 3 degrees, Peery explained.
As the water flows through the river, its dams and reservoirs, that temperature will typically rise as it mixes more thoroughly at each step with existing flows.
To assist migrating salmon, the Army Corps has also focused on installing infrastructure to provide cooler water to fish exiting 100-feet high ladders or fishways, a series of 1-foot-high pools that allow the fish to move over a dam.
“These exits, obviously, are near the surface of the river, and again, that's where this warmest water is in the system,” Peery said. New pumps push cooler water up from the base of the dam to allow fish to continue their migration, rather than hitting a “thermal barrier” of warm waters.
Environmental advocates argue that the Army Corps could do more, however, such as by lowering the levels of the existing reservoirs.
That’s because temperatures in the reservoirs are dictated by a variety of other factors. In addition to the temperature of water entering the facilities, things like air temperatures and the volume of a reservoir can affect how quickly water warms and how hot it gets.
Partially emptying those facilities would also amplify the effects of the cold water released from Dworshak Dam, since it would need to cool a smaller volume of water.
Peery acknowledged that reducing water levels in the reservoirs would likely decrease temperatures, it would also mean the Army Corps could fail to meet its additional mandates on the river system.
If water levels in reservoirs are dropped too low, for example, it could disrupt transportation on the waterway. Similarly, a minimum water level is required for hydropower production.
“The Corps has multiple missions that we’re authorized by Congress to fulfill,” Peery said, pointing to hydropower, environmental stewardship, navigation, recreation and flood management “We don’t have a choice to pick and choose which ones we’d like to do. We have to do them all simultaneously.”
“There definitely are some compromises that have to be made at times,” he added.
Johnson, with the Columbia Riverkeeper, said he is encouraged by the Army Corps' decision to reshape its plans with the working group but remains skeptical that the agency will achieve the necessary temperature reductions.
“The Corps doesn’t get to take potential solutions off the table because they might conflict with other uses of the reservoir,” Johnson said. Instead, he said he’d like to see the agency analyze all potential solutions to the water quality problems then address whether those solutions are feasible.
To illustrate the challenges faced by migrating fish in the region, Johnson points to low rates of success for the endangered Snake River sockeye salmon attempting to reach their spawning grounds.
Preliminary data provided by the Idaho Department of Fish and Game shows as of late July that among the approximately 1,800 Snake River sockeye to pass the Bonneville Dam — the first major barrier to fish migrating in the Columbia and Snake rivers — 55 percent reached the Lower Granite Dam, the last of the four Lower Snake River facilities.
By comparison, in 2023 only 22 percent of those fish reached the Lower Granite Dam — a particularly disastrous year thanks to warm temperatures — and in 2022 data showed about 66 percent.
Johnson said while he would prefer to see the dams breached, he would otherwise like to see EPA and the Army Corps utilize "sophisticated water quality monitoring models" to determine five to 10 options for altering the river's temperature.
“It’s pretty clear what [the Washington State Department of] Ecology’s rules say and what Ecology wants to have happen but given the Corps' apparent unwillingness to take responsibility for the heat pollution that they’re causing, they’ll continue to try to find ways to not really address all potential solutions,” Johnson said. “We’ll keep pushing them to do that."
E&E News: Lower Snake River ‘temperature diet’ looks to shed degrees
