The State of Idaho's Lakes 2026

Cleanest lakes in Idaho

Cleanest combined nutrient and algae readings, 2026.

1. 1.Black Cnyn Reservoir Ns of — Gem County7.5 ft clarity · 30 µg/L P · 3 µg/L chl-a
2. 2.Palisades Lake — Bonneville County13.1 ft clarity · 21 µg/L P · 2 µg/L chl-a
3. 3.Cas Reservoir Inlet Between Lf And — Valley County4.3 ft clarity · 40 µg/L P · 12 µg/L chl-a
4. 4.Lake Walcott — Cassia County4.3 ft clarity · 51 µg/L P · 15 µg/L chl-a
5. 5.Cascade R W of Sugarloaf Island Lake — Valley County8.2 ft clarity · 29 µg/L P · 8 µg/L chl-a
6. 6.Littlewood Lake — Blaine County12.5 ft clarity · 28 µg/L P · 14 µg/L chl-a
7. 7.Mountain View Lake — Owyhee County39 µg/L P · 14 µg/L chl-a

Highest measured algae

Highest measured chlorophyll-a (algae) concentration.

1. 1.Mann Creek Reservoir — Washington County179 µg/L chlorophyll-a
2. 2.Little Wood Reservoir — Blaine County30 µg/L chlorophyll-a
3. 3.Soldier Meadow Reservoir East Arm — Nez Perce County29 µg/L chlorophyll-a
4. 4.Soldiers Meadow Reservoir West Arm — Nez Perce County29 µg/L chlorophyll-a

Trending lakes

Improving

1. 1.Mud Lake — Bear Lake County
2. 2.Cas Reservoir Inlet Between Lf And — Valley County
3. 3.Lake Walcott — Cassia County
4. 4.Island Park Lake — Fremont County
5. 5.Cascade R W of Sugarloaf Island Lake — Valley County
6. 6.Island Pk Reservoir — Fremont County
7. 7.Waha Reservoir Middle — Nez Perce County
8. 8.Soldier Meadow Reservoir East Arm — Nez Perce County

Declining

1. 1.Littlewood Lake — Blaine County
2. 2.Palisades Reservoir — Bonneville County
3. 3.Lake Lowell Across From Upper Embankment — Canyon County
4. 4.Little Wood Reservoir — Blaine County