Most Oregon lakes in good condition, new study shows

A kayak loaded up for a trip to a boat-in campsite at Waldo Lake. The lake was among 49 statewide, and 15 in the Willamette Basin, sampled for a new DEQ study.
A kayak loaded up for a trip to a boat-in campsite at Waldo Lake. The lake was among 49 statewide, and 15 in the Willamette Basin, sampled for a new DEQ study.

Oregon’s 4,819 lakes are largely in good ecological condition, especially when compared with those elsewhere in the nation, a new report from the state Department of Environmental Quality concludes.

There were areas of concern, however, in some Oregon lakes and reservoirs, the report notes.

The most widespread problem identified was excess nutrients, including nitrogen and phosphorus, which can come from sewage treatment plants, failing septic systems and fertilizer use in agriculture and landscaping.

The study estimated 21% of Oregon’s lakes, or about 1,000, were in poor condition with regard to phosphorus levels. It estimated 13% of the state’s lakes, or about 600, were in poor condition with regard to nitrogen.

“Oregon’s lakes are special places, and this assessment provides a great deal of solid information about their environmental health,” said Lori Pillsbury, DEQ's laboratory administrator. “The results will inform how we continue to protect our lakes, and make improvements where needed.”

People fish from boats during the Detroit Lake Fishing Derby in Detroit in May.
People fish from boats during the Detroit Lake Fishing Derby in Detroit in May.

DEQ collected samples in 49 randomly chosen lakes during the summer of 2017, as part of the U.S. Environmental Protection Agency’s National Lakes Assessment. It used those results to make estimates for the remaining lakes.

Each estimate in the study shows a 95% confidence interval that conveys the level of certainty in the estimate.

The results will help DEQ better monitor changes in lake conditions and better protect the state's lakes, the report says.

The samples also were tested for toxics, making this Oregon’s first statewide dataset on toxics in lakes.

The results show that most Oregon lakes are in good condition for biological communities, such as insects and zooplankton. The majority of Oregon’s lakes are of high recreational value.

And, although toxic compounds sometimes exceed levels set to protect human health and aquatic life, that is rare.

Disturbance of lakeshore habitat was the second-most frequent problem identified. Disturbances include roads, houses, agricultural activities, logging and trash.

High levels of human disturbances in the riparian zone were observed in an estimated 11% of lakes, or about 500 lakes.

Also from the report:

  • E. coli was estimated to be present in 34% of Oregon lakes, but within the safe level for recreational contact.

  • Mercury was present in about 55% of Oregon lake sediments, DDT in about 44%, and PCBs in about 27%. In some locations, these were over background or screening levels. All are compounds that persist in sediment and bioaccumulate in fish and other aquatic life.

DEQ tested 15 lakes in the Willamette Basin. It did not test Detroit Lake, which provides drinking water for Salem and other nearby communities.

Tracy Loew is a reporter at the Statesman Journal. She can be reached at tloew@statesmanjournal.com, 503-399-6779 or on Twitter at @Tracy_Loew.

This article originally appeared on Salem Statesman Journal: Oregon’s 4,819 lakes in good condition, but DEQ study finds concerns