Willamette River Temperature Tmdl and River Model

The Willamette River, Oregon, and many of its tributaries are included on the 303(d) list of water bodies that fail to meet water quality standards due to temperature standard violations. These violations potentially impact a number of beneficial uses, including populations of Chinook salmon, Coho salmon, and Steelhead that are included on the U. S. Threatened and Endangered Species List. In order to address the temperature concerns, a TMDL was developed for the Willamette Basin. The TMDL impacts major industrial and municipal point sources including the wastewater treatment facilities of the cities of Portland, Salem and Eugene; a number of publicly and privately operated hydroelectric facilities and reservoirs including Portland General Electric and Eugene Water and Electric Board facilities and 13 U. S. Army Corps or Engineers operated reservoirs; as well as many riparian landowners in the basin. A two-dimensional hydrodynamic and water quality model of the Willamette River and major tributaries was developed to evaluate anthropogenic impacts on Willamette River temperature. The model was developed collaboratively by Oregon Department of Environmental Quality, federal agencies, industry, and municipalities. This paper presents modeling simulations which evaluate the sensitivity of river temperature to shade, effluent loads, and reservoir and hydroelectric project operations and describes wasteload allocations and load allocations developed to limit temperature impacts.