Eutrophic Lakes in Idaho

28 eutrophic lakes in Idaho. 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. 28 {{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.

#	Lake	County	Grade	Clarity	Depth	TSI
1	Mud Lake	Bear Lake	B	-	-	51
2	Nla Lake	Boise	B	23.3 ft	-	68
3	Nla Lake	Custer	B	38.1 ft	-	59
4	American Falls R Lake	Bannock	B	-	-	53
5	Nla Lake	Boundary	C	6.1 ft	-	51
6	Arrowrock Reservoir	Elmore	C	9.5 ft	-	52
7	Waha Reservoir	Nez Perce	C	9.7 ft	-	50
8	Cascade Reservoir Inlet	Valley	C	7.3 ft	-	50
9	Nla Lake	Caribou	C	10.1 ft	-	54
10	Nla Lake	Bonner	C	3.9 ft	-	54
11	Nla Lake	Valley	C	9 ft	-	54
12	Cascade R Lake	Valley	C	5.7 ft	-	52
13	American Falls Reservoir	Power	C	-	-	55
14	Mountain View Lake	Owyhee	C	-	-	57
15	American Falls R-Sr Cattle Tower Lake	Power	C	-	-	58
16	American Falls Res Off Seagull Bay Lake	Power	C	-	-	60
17	Nla Lake	Cassia	C	4.7 ft	-	57
18	Nla Lake	Clearwater	C	6.4 ft	-	55
19	Cas Reservoir Inlet Between Lf And	Valley	C	4.3 ft	-	56
20	Lake Walcott	Cassia	C	4.3 ft	-	58
21	Island Pk Reservoir	Fremont	C	2.3 ft	-	60
22	American Falls R-Sportsmans Cove Lake	Power	C	-	-	61
23	American Falls R-Little Hole Draw Lake	Power	C	-	-	60
24	Nla Lake	Owyhee	D	3 ft	-	59
25	Ririe Lake	Bonneville	D	4.6 ft	-	58
26	Nla Lake	Franklin	D	5.2 ft	-	60
27	Nla Lake	Fremont	D	6.2 ft	-	59
28	Little Wood Reservoir	Blaine	D	-	-	64

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 →Oregon version →Arkansas version →Oklahoma version →Kansas version →Nebraska version →Nevada version →Arizona version →Montana version →New Mexico version →Tennessee version →Alabama version →Virginia version →Kentucky version →Utah version →Washington version →Wyoming version →All Idaho lakes →

Source: EPA National Aquatic Resource Surveys, 2026.