Do Dams Really Impact River Temps in
by Kurt Miller
I've written several op-eds over the past year related to critical topics like social equity, salmon recovery, and the importance of hydropower as a crucial, carbon-free energy resource in the Pacific Northwest. Yet, a recent statement I gave on the subject of river temperature regulation may have been one of my most controversial.
My perspective appeared in a May 13 Daily News article about a decision by the Washington State Dept. of Ecology to add a river temperature provision into an EPA permit for Columbia River Basin dams. The EPA permit was designed to manage pollution coming from equipment. It was never intended to try to control the temperature of an entire river system.
The article was picked up and edited by the Associated Press, and subsequently ran in a few national publications.
I was accurately quoted as saying, “What this decision risks doing is saying, 'We are going to regulate the temperature of the river because there are dams there.' But the reality is even without the dams, those temperatures could be the exact same.”
In a follow-up letter to the editor, a community activist wrote that I had no justification in asserting this.
I want to respectfully respond by sharing the science behind my statement because it has important implications for environmental policy.
To begin, a report released by the EPA on May 18 indicates that the water coming from Canada and from upstream of the lower Snake River dams in Idaho often substantially exceeds the Washington state temperature standards before it gets to the Washington border. This means that even without the lower Columbia and lower Snake dams in place, the state's temperature standards would be unattainable. Also, while the EPA report attempts to allocate temperature responsibility to each respective dam in the study area, it acknowledges this effort as a difficult and imperfect task.
Furthermore, a 2002 peer-reviewed study performed by Pacific Northwest National Laboratory showed that dams within the Columbia River and Snake River basins tend to moderate extreme water temperatures. The PNNL study states, “… the reservoirs decrease the water temperature variability. The reservoirs also create a thermal inertia effect that tends to keep water cooler later into the spring and warmer later into the fall compared to the un-impounded river condition.” 
Also in 2002, a team of researchers conducted a water temperature study on behalf of the U.S. Army Corps of Engineers. They compared pre-lower Snake River dam measurements of water temperature from 1955-1958 to measurements taken after the lower Snake River dams were constructed.
The research found no evidence that river temperatures had increased as a result of the dams, and instead appeared to have remained unchanged or slightly lower, even though air temperatures had increased. The team identified air temperature and flow levels as the biggest influences on temperatures in the river.
And so, to my original assertion, I'm very concerned by the position taken by the Washington State Dept. of Ecology to include river temperatures in its permitting process. This decision could needlessly reduce the availability of a carbon-free energy resource and increase electricity bills for millions of customers. That outcome would be a step in the wrong direction for the climate, for salmon, and for the social welfare of the region.
The EPA issued a public notice seeking comment on this topic beginning a 60-day public process beginning May 21. We encourage everyone to participate in this important issue and help protect the future of carbon-free, low-cost hydropower in our region. Comments should be provided to ColumbiaRiverTMDL@epa.gov by 5 p.m. (PDT) on July 21, 2020.
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