WaterWatch Challenges Willamette Water Temperature Plan

By WaterWatch Staff  |  Oct. 10, 2021  |  Instream

Watch of Oregon is challenging state approval of a plan to dampen the water-temperature impact of a $1.3 billion municipal water withdrawal project on the Willamette River.

WaterWatch is asking the Multnomah County Circuit Court to overturn or re-evaluate a decision by the Oregon Department of Environmental Quality (DEQ) approving a “Thermal Trading Plan” to offset the water-temperature impact of withdrawing 150 million gallons of water a day from the Willamette River near Wilsonville. Staff attorney Brian Posewitz says the plan underestimates the temperature impact and that proposed offsets of those impacts are too uncertain or illusory. The issues are important because the Willamette River is already too warm for much of its fish and wildlife, including steelhead and salmon threatened with extinction.

The water will be withdrawn by the Willamette Water Supply Systems – an intergovernmental entity of the Tualatin Valley Water District and the cities of Beaverton and Hillsboro. The Portland Tribune reported in 2014 that cities served by Tualatin Valley Water District – including parts of Beaverton, Hillsboro, and Tigard – have for years been coveting water from the Willamette for their municipal water supply as a cheaper alternative to buying water from Portland. The search for other water sources was driven by the need to supply Washington County’s growing businesses and population. The Willamette Water Supply System has a federal Clean Water Act permit that requires it to address the temperature impact of its water withdrawals.

“Various things tend to make water temperature problems – usually water being too warm – better or worse,” said Brian. “But certainly, one of the ways you make a warm-water problem worse is by reducing flows, because less water warms faster than more water.”

As Oregon and the western U.S. are increasingly mired in drought, the water withdrawals of city and municipal water agencies will have even greater temperature impacts on rivers and streams, whether in the Willamette Valley or east of the Cascades.

WaterWatch’s challenge to the Willamette Water Supply System’s Thermal Trading Plan will focus, in part, on how the plan treats 30 million gallons of water to be withdrawn under a permit the city of Hillsboro bought from the city of Salem. The plan assumes that, had Salem kept the rights for that water, it would have withdrawn that much more water from the Willamette River at Salem, thus reducing flows and raising river temperatures between Salem and Wilsonville. Willamette Water Supply system is taking credit for keeping that water in the river. WaterWatch believes the evidence in its case will show that, by using other water rights, Salem will withdrawal just as much water as if it had never sold the right to 30 million gallons to Hillsboro.

“The result is that the Thermal Trading Plan significantly underestimates the temperature impact of the Water Supply System,” said Brian. In addition, the Thermal Trading Plan fails to adequately show how the Water Supply System will make up for the temperature impact of its water withdrawals. It proposes to use riparian restoration projects to increase streamside shading but fails to provide enough detail to show that the shading will adequately offset the impact.

The plan also proposes to increase flows with water from Willamette Basin reservoirs upstream, but that water is already being used to lower water temperature in the river. The Willamette Water Supply System is just one example of how municipal water use – which includes drinking water but also water for things like washing cars and watering lawns – can impact streamflows and water quality.

If these issues are important to you, be sure to let your city leaders and water department officials know you want your water supply to be sustainable by protecting fish, wildlife and water quality.

This article originally appeared in the Fall 2021 issue of WaterWatch’s Instream newsletter. Photo by Tommy Hough.