Temp Chart

EPA analyzed the change in water temperatures from five different sources.

Hydroelectric dams have so far caused the largest increases in water temperatures in the lower Snake River and the U.S. portion of the Columbia River, but the water can already exceed temperature standards when it enters Washington state, according to a newly released analysis by the Environmental Protection Agency.

EPA's findings of total maximum daily load for temperature—released May 18 for public comment—found that in the summer and early fall, water is already significantly warmer than the temperature standards in the Columbia River where it enters Washington state from Canada, and in the Snake River where it enters the state from Idaho.

A TMDL analysis calculates the amount of a pollutant (in this case, heat) a waterbody can receive and still meet specific standards. It then allocates load reductions to sources of the pollutant necessary to meet a target it determines.

EPA was ordered by a U.S. District Judge in Seattle to complete the TMDLs for the two rivers in October 2018 after the agency unsuccessfully argued Washington and Oregon were responsible for developing them. That ruling stood after EPA lost its appeal in the 9th U.S. Circuit Court of Appeals in December.

The environmental and fishing groups that sued EPA to force compliance hailed the release of the plan as long overdue, and cited the document as further evidence the lower Snake River dams should be removed.

Those four dams are estimated to increase Snake River temperatures somewhere between 0.3 and 3.2 degrees Celsius (0.5 to 5.8 degrees Fahrenheit) from July through October. During the same months, the Columbia River dams from Bonneville to Grand Coulee sometimes decrease water temperatures by as much as 0.9 C (1.6 F) but also increase temperatures by up to 4.5 C (8.1 F), EPA's analysis said.

Climate change has increased temperatures in both the Snake and Columbia rivers by an additional 1  to 2 degrees Celsius (1.8 to 3.6 degrees Fahrenheit) since 1960, or 0.2 to 0.4 C (0.36 to 0.72 F) per decade, EPA said. (The analysis does not include future increases from climate change because TMDL studies evaluate current sources of heat.)

Other sources—including point sources and tributaries—have caused significantly smaller temperature increases, while the Dworshak Dam on the Clearwater River decreases temperatures in the Snake River by as much as 3.8 C (6.8 F) during those four months, the TMDL results said.

Conservation and fishing groups said warmer water has long been a major problem for threatened and endangered salmon and steelhead in the basin.

"We must swiftly implement EPA's plan to protect what remains of the once-magnificent anadromous fisheries on the Snake, Clearwater, and Salmon rivers—starting with removing the Lower Snake River dams," Buck Ryan, executive director of Snake River Waterkeeper, said in a news release.

Northwest RiverPartners countered that the analysis shows that Columbia Basin water temperature standards in Washington and Oregon cannot be met, even if the dams were removed. "My concern is that, if it becomes part of an implementation plan, essentially the dams could be found to be operating in violation of the plan, even though there's nothing they could actually do at the dams—including removing them—to achieve the states' water quality standards," RiverPartners Executive Director Kurt Miller said.

Miller said water temperatures are a legitimate concern, and RiverPartners favors taking reasonable actions to reduce them. But measures that reduce hydropower generation would be counterproductive by adding impacts from climate change, he said.

He added that even rivers with no dams are experiencing temperatures that kill fish—including the Fraser River in British Columbia, and undammed rivers in Alaska. "It's something I really hope the states of Washington and Oregon keep in mind as they ultimately develop their implementation plan," Miller said. "Do you really want to be reducing the capability of an important carbon-free resource?"

TMDLs are required under the federal Clean Water Act for any water body deemed impaired by states. They determine a pollutant (temperature in this case) reduction target, and allocate reductions necessary to the sources of the pollutant.

States usually issue TMDLs for EPA's approval, but in this case, the U.S. District Court agreed that Washington and Oregon had abandoned intentions to create one for the Snake and Columbia rivers after entering in an agreement with EPA to do the work, since the river involves several jurisdictions and EPA had done some of the analysis.

The public is invited to comment on EPA's TMDL analysis through July 21. After considering comments, the agency may modify the final document before providing it to Oregon and Washington to incorporate in their water quality management plans.

The TMDL analysis notes that because of continuing impacts from climate change and upstream impacts in Idaho and Canada, the states' water quality standards are unlikely to be met.

"The current water quality conditions present a significant challenge to achieving downstream water quality standards in Washington and Oregon," the analysis says. From July through September, the main water quality standard at the U.S.-Canada border is a seven-day average daily maximum of 16 degrees Celsius (60.8 degrees Fahrenheit), which increases to 17.5 C (63.5 F) from Grand Coulee Dam to Priest Rapids Dam, and to 20 C (68 F) below Priest Rapids Dam.

In its analysis, EPA says the states could change designated uses in the river to meet those standards. The designated uses related to water temperature generally involve aquatic life, such as conditions needed for salmonid habitat, migration, rearing or spawning.

"Even if all the allocations in this TMDL are implemented and the temperature reductions envisioned are fully realized, it is unlikely that the numeric criteria portion of the [water quality standard] will be met at all times and all places," the TMDL analysis states, and later suggests, "One option for addressing the conflict created by the inability to achieve applicable water quality criteria at all times and all places is for the States to make changes to their applicable designated uses." It notes that a decision to modify or remove a designated use rests with a state.

In analyzing the Columbia Basin's current temperatures, the TMDL analysis used data from 2011 through 2016 from the University of Washington's Columbia River Data Access in Real Time database. Temperatures were evaluated at 18 DART stations, including readings from four lower Snake River dams and 11 Columbia River dams. Most of the stations are in the dams' tailraces, where water is well mixed, except for Wells Dam, where data came from the forebay as no tailrace data exists, and for Bonneville, where the temperature station is 6 miles downstream.

The TMDL analysis includes a comparison of maximum monthly temperatures with target temperatures for each of the dams from July through October, showing reductions that would be needed to achieve them.

The largest reductions would be needed in August at the Washington state border, where the Columbia River would need to drop by 3.2 degrees Celsius (5.8 degrees Fahrenheit) and the Snake River by 3.6 C (6.5 F).

August is also when maximum temperatures at Grand Coulee Dam exceed the target by as much as 2.9 C (5.2 F), followed by Rock Island Dam at 2.8 C (5.0 F). On the Snake River's Ice Harbor Dam, a reduction of 1.8 C (3.2 F) would be needed to meet targets.

Starting with temperatures at the Washington border, the TMDL analysis estimates the cumulative temperature impact at each dam by comparing current temperature to estimated temperature under free-flowing conditions. An allocation exceedance is then assigned to each dam for July, August, September and October.

In July, the analysis estimated no exceedances at any of the dams from Grand Coulee to Priest Rapids on the Columbia, or at Lower Granite on the Snake River. Allocation exceedances at McNary, John Day, The Dalles and Bonneville dams ranged from 0.3 to 0.4 C (0.5 to 0.7 F); and from 0.3 to 0.6 C (0.5 to 1.1 F) at Little Goose, Lower Monumental and Ice Harbor dams.

By August, Wanapum and Priest Rapids dams were added to the list of allocation exceedances. By September, all dams on the Columbia River have allocation exceedances, the highest at Priest Rapids, by 1.8 C (3.2 F).

The document also discusses and analyzes influences by tributaries, and offers details on cold water refuges, as required under Oregon's water quality standards.

Near the end of the TMDL analysis, EPA noted state-issued TMDLs provide reasonable assurances standards will be met through a description of load allocations.

"By contrast, this federal TMDL is being issued by EPA, which lacks authority to implement nonpoint source controls or otherwise assure reductions in nonpoint source pollution," it stated. Implementation will depend on development of plans by Washington and Oregon, and river temperature reduction efforts by federal agencies, it said.

It concluded, "EPA recommends that the states, in developing their implementation plans, consider continued development, revision, and implementation of tributary TMDLs, including protection of [cold water refuges]; funding mechanisms to address traditional nonpoint sources of heat; voluntary conservation programs; a collaborative monitoring and tracking program; and other activities designed to reduce water temperature."

K.C. Mehaffey covers fish issues for Clearing Up, and is editor of the NW Fishletter. She joined the NewsData writing team in February 2018. From lawsuits to scientific studies, she is enjoying the deep dive into the Columbia Basin's many fish topics.