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LakeQuality

Eutrophic Lakes in Oregon

22 eutrophic lakes in Oregon. High nutrients, frequent algae, reduced clarity.

A eutrophic lake is a productive ecosystem with the trade-offs that come with productivity: more food at the base of the food web, more clarity reduction by mid-summer, more dissolved-oxygen variability near the bottom. 22 {{stateName}} lakes register as eutrophic. Only 0% are deep — eutrophy correlates with shallowness, agricultural watersheds, and the kind of nutrient-input history that takes decades to shift.

Eutrophic lakes typically grade C or D on the LakeGrade rubric. The same nutrient richness that defines the trophic class drives the lower grade.

#LakeCountyGradeClarityDepthTSI
1Davis LakeDeschutesB--51
2Prineville ReservoirCrookB--50
3Fish LakeJacksonB--51
4Howard Prairie LakeJacksonB--53
5Deschutes River Arm LakeJeffersonB4.6 ft-50
6Phillps LakeBakerC--54
7Devil'S LakeLincolnC--58
8Mckay ReservoirUmatillaC--54
9Unity ReservoirBakerC--59
10Lake OwyheeMalheurC--57
11North Tenmile LakeCoosD4.9 ft-54
12Lake Billy ChinookJeffersonD--62
13Crooked River Arm LakeJeffersonD--62
14Bully Creek LakeMalheurD4.9 ft-63
15Mckay LakeUmatillaF3.3 ft-67
16Howard Prairie ReservoirJacksonF2.3 ft-69
17Deschutes River Arm LakeJeffersonF--65
18Cullaby LakeClatsopF--66
19Tenmile LakeCoosF--64
20Lake Billy ChinookJeffersonF--69
21Diamond LakeDouglasF--67
22Thief Valley ReservoirUnionF--69
All eutrophic lakes →Minnesota version →Wisconsin version →Illinois version →Michigan version →Iowa version →Ohio version →Pennsylvania version →New York version →Missouri version →Indiana version →North Dakota version →South Dakota version →Florida version →Colorado version →North Carolina version →Vermont version →Texas version →Arkansas version →Oklahoma version →Kansas version →Nebraska version →Nevada version →Arizona version →Idaho version →Montana version →New Mexico version →All Oregon lakes →

Source: EPA National Aquatic Resource Surveys, 2026.