Eutrophic Lakes in Idaho
9 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. 9 Idaho 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 carry higher phosphorus and chlorophyll-a readings. The same nutrient richness that defines the trophic class shows up in those numbers.
| # | Lake | County | Clarity | Depth | TSI |
|---|---|---|---|---|---|
| 1 | Mud Lake | Bear Lake | - | - | 59 |
| 2 | Cas Reservoir Inlet Between Lf And | Valley | 4.3 ft | - | 56 |
| 3 | Lake Walcott | Cassia | 4.3 ft | - | 58 |
| 4 | Island Park Lake | Fremont | 9.8 ft | - | 50 |
| 5 | Cascade R W of Sugarloaf Island Lake | Valley | 8.2 ft | - | 50 |
| 6 | Island Pk Reservoir | Fremont | 2.3 ft | - | 60 |
| 7 | Littlewood Lake | Blaine | 12.5 ft | - | 50 |
| 8 | Mountain View Lake | Owyhee | - | - | 57 |
| 9 | American Falls R-Little Hole Draw Lake | Power | - | - | 60 |
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 →Georgia version →Massachusetts version →Ontario version →Québec version →Nova Scotia version →British Columbia version →Newfoundland and Labrador version →All Idaho lakes →
Source: EPA National Aquatic Resource Surveys, 2026.