Oregon’s 4,819 lakes are largely in good ecological condition, especially when compared to those elsewhere in the country, a new report from the state department of environmental quality concludes.
There were, however, areas of concern in some Oregon lakes and reservoirs, the report noted.
The most widespread problem identified was excess nutrients, including nitrogen and phosphorus, which can come from sewage treatment plants, failing septic systems, and the use of fertilizers in agriculture and landscaping.
The study estimated that 21% of Oregon’s lakes, or about 1,000, were in poor condition when it comes to phosphorus levels. He estimated that 13% of the state’s lakes, or about 600, were in poor condition for nitrogen.
“Oregon’s lakes are special places, and this assessment provides a lot of solid information about their environmental health,” said Lori Pillsbury, DEQ’s lab administrator. “The results will indicate how we continue to protect our lakes and make improvements where needed. »
DEQ collected samples from 49 randomly selected lakes during the summer of 2017 as part of the US Environmental Protection Agency‘s National Lakes Assessment. He used these results to make estimates for the remaining lakes.
Each study estimate has a 95% confidence interval that reflects the level of certainty of the estimate.
The results will help DEQ better monitor changes in lake conditions and better protect the state’s lakes, the report said.
The samples were also tested for toxic substances, making this Oregon’s first statewide dataset of toxic substances in lakes.
The results show that most Oregon lakes are in good shape for biological communities, such as insects and zooplankton. The majority of Oregon’s lakes have high recreational value.
And, although toxic compounds sometimes exceed levels set to protect human health and aquatic life, this is rare.
Riparian habitat disturbance was the second most frequently identified issue. Disturbances include roads, homes, agricultural activities, logging and litter.
High levels of human disturbance in the riparian zone were observed in about 11% of the 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 places, these were above background or screening levels. All are compounds that persist in sediments and bioaccumulate in fish and other aquatic life.
DEQ tested 15 lakes in the Willamette Basin. He did not test Lake Detroit, which provides drinking water to Salem and other nearby communities.