Willamette Basin Total Maximum Daily Loads (TMDLs) -
The Problem

The Willamette River Basin is home to seventy percent of Oregon's population. Those who live or work in the basin depend on the river for many resources, and also contribute to potential pollution problems that come with any residential, municipal, industrial, or agricultural operation.

For the amount of land area in the basin, more water flows from the Willamette River than from any other major river basin in the United States. The basin, 180 miles long and 80 miles wide, is bordered by the crest of the Cascade Mountains to the East, the crest of the Coast Range to the West, and the Columbia River to the North where the two rivers meet. About 2.3 million people live in the river basin near its 16,000 miles of rivers and streams, and more than half of them live in the Portland metropolitan area.

As population increases, and land conversion to urban and industrial uses continues in the basin, these changes affect the Willamette River.

For example, the household chemical products applied in and around the home, including pesticides and fertilizers, may end up in the Willamette after passing through treatment plants or in storm water runoff. Pollutants can reach the river through groundwater as well as from runoff and pipes.

• Groundwater Quality Report for the Willamette Basin, March 2004

During the 1990s, the Legislature provided resources for the Department of Environmental Quality (DEQ) to work with others to study the health of the Willamette River. The studies included a number of key findings, including a high incidence of deformities in the skeletons of certain fish, as well as the presence of toxic chemicals in fish tissues at levels that make the fish unsafe to eat. The studies also found that the majority of water pollution came from urban and rural runoff.

In 2001, DEQ began working with a group of stakeholders to create a plan to bring the Willamette up to water quality standards. This group participates as the Willamette River TMDLs Council.

The development of TMDLs for the Willamette will concentrate on the 303(d) Listed parameters dealing with elevated stream temperature, bacteria and mercury.