Only the DRA is Advocating for Tower Changes Spring Chinook Need
Now more than ever, the Deschutes River Alliance is the strongest voice of the lower Deschutes River and the only organization fighting for tower changes that improve water quality and benefit native fish in the lower Deschutes River.
For the past six months, I have represented DRA in a stakeholder process convened by the owners of the Pelton Round Butte Hydroelectric project and the Selective Water Withdrawal (SWW) Tower that releases water into the lower Deschutes River.
This stakeholder group includes the operators, state agencies and organizations focused on native fish and water quality, with the premise “to identify cold water release scenarios that could be modeled for the lower river,” and benefit native fish.
At the November meeting, I asked the operators of the dam complex to test a scenario, outlined in their own water quality study, that would improve water quality in the lower Deschutes River. The suggestion was met with silence. Other attendees instead chose to assert that current operations, and the temperature profile, benefit aquatic life - a false assertion that risks the survival of the iconic wild spring Chinook salmon from poor water quality and the deadly Ceratanova shasta parasite.
The reintroduction steelhead and spring Chinook was a key requirement for the relicensing of the Pelton Round Butte Hydroelectric project and the impetus for the (SWW) tower. The tower was sold as a way to collect salmon and steelhead smolts migrating downstream through Lake Billy Chinook (LBC) during the spring. Since the smolts migrate in the upper water column of LBC, the flow to the tower’s surface inlet would attract the smolts and they would be funneled into a collection facility near the tower inlet. This surface water is also warmer and the majority comes from the Crooked River, which has the poorest water quality of the three main tributaries feeding LBC. As a result, when the majority of water flowing into the lower Deschutes River is from the surface, it is both warmer and the poorest quality water.
History of C. shasta
Although C. shasta has always existed in the lower Deschutes River, as has its aquatic worm host organism, C. shasta was not thought to be a significant problem. However, very high pre-spawning mortality of wild adult spring Chinook in the Warm Springs River starting in 2014 was a sign that C. shasta was becoming a serious problem. Studies have found that both juvenile and adult Deschutes River Chinook were dying prematurely, with C. shasta the suspected cause.
Prior to the SWW tower operations, water released into the lower Deschutes River was primarily from the bottom of LBC and was cooler and cleaner. The SWW tower introduced the warmer, poorer quality surface water over a much longer period of time, including the winter, and both PGE’s data, as well as DRA’s data, show very large increases in the number of host worms and parasite.
Infection of salmon by C. shasta occurs at levels of 10 spores/liter of river water. Research by Oregon State University and the Oregon Department of Fish and Wildlife have measured spore counts many times that amount in the lower Deschutes River as far downstream as the Oak Springs area during the spring months. This implies that downstream migrating juvenile spring Chinook smolts as well as upstream migrating adults are exposed to C. shasta at lethal levels.
In studies using juveniles caged in the lower Deschutes River, as many as 87% of some groups showed infection and subsequent high mortality by C. shasta. The prevalence of infection and subsequent mortality increased with increasing water temperature, clearly suggesting that warmer water in the spring during juvenile spring Chinook outmigration is an important mortality factor effecting the survival of these fish.
The adult spring Chinook migrate up the lower Deschutes River during spring are exposed to C. shasta infection and mortality as well as an increased pre-spawning mortality throughout their range.
Risks to Wild Spring Chinook
The wild spring Chinook are especially at risk. More than 40 years of research has established that a spawning population between 1,000 and 1,300 adults is needed to maintain a healthy population of these fish. The same research shows that nearly all wild spring Chinook in the Deschutes use the Warm Spring River for spawning and juvenile rearing. A barrier dam and trap at Warm Springs National Fish Hatchery makes it possible to accurately count upstream migrating adults with precision and later spawning ground counts can later measure the success of these adults which makes it possible to monitor pre-spawning mortality.
A common measure of pre-spawning mortality in anadromous fish including spring Chinook, is the number of fish it takes to construct one successful redd or spawning bed. A fish/redd ratio of between 3 and 4 is commonly believed to indicate acceptable pre-spawning mortality. In fact, the long-term data set below shows that prior to increased water temperature and nutrient input (and subsequent increases in the host organism for C. shasta and spore counts) that 4 adults/redd was the average. After SWW tower operation started in 2010, however, the number of adults required to construct one redd shot up to in some cases over 20 adults/per redd. This strongly suggests a seriously high adult pre-spawning mortality and it is very likely, based on the timing of this change alone that SWW tower operation is the cause of C. shasta infection of adults on their way to the spawning grounds in the Warm Springs River.
https://critfc.org/wp-content/uploads/2021/08/18-04.pdf
It should come as little surprise that the number of wild adult spring Chinook returning to the Deschutes has plunged to record low levels recently. Adult counts at the Warm Springs National Hatchery have fallen to a small fraction of the minimum target number of 1,000 and both sport angling and tribal harvest at Sherars Falls have been severely constrained due to low returns. In fact, wild spring Chinook returns have been so low that a significant portion of the wild adults have been kept and spawned at the hatchery as an emergency measure against the extinction of the population.
The current plight of the wild spring Chinook in the lower Deschutes is another and very serious example of the damage that current SWW tower operations are doing to the river. It is difficult for DRA to accept that other stakeholders will not support our well-reasoned and thoughtful call for operational changes in SWW operation that would benefit not only spring Chinook but all native fishes in the lower Deschutes.
Deschutes River Alliance: Cooler, cleaner H2O for the lower Deschutes River.
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