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LakeQuality
Pink and orange afterglow over the treeline on Slim Lake after sunset

Updated August 2026

The State of South Dakota's Lakes 2026

Of 8 lakes in South Dakota, 0% sit in EPA's favourable condition classes for nutrients and algae and 100% in its poorer ones. Traverse Lake is the cleanest; 1 lakes (12.5%) are on an official impaired-waters list.

Data Report

8
Monitored lakes sampled
F
Average readings
0%
low nutrient and algae readings
12.5%
On impaired list

South Dakota nutrient and algae readings

Cleanest lakes in South Dakota

Cleanest combined nutrient and algae readings, 2026.

  1. 1.Traverse Lake — Roberts County3.9 ft clarity · 173 µg/L P · 36 µg/L chl-a

Highest measured algae

Highest measured chlorophyll-a (algae) concentration.

  1. 1.Big Stone Lake — Roberts County70 µg/L chlorophyll-a
  2. 2.Traverse Lake — Roberts County36 µg/L chlorophyll-a

Trending lakes

Declining

  1. 1.Traverse Lake — Roberts County

Impaired waters in South Dakota

1 lakes appear on the EPA/state 303(d) impaired-waters list (1 formally listed, 0 with a cleanup plan/TMDL).

Oxygen depletion (low DO) · 1pH / acidity · 1

Explore South Dakota lakes

Lake Fishing Forecast

Species activity outlook by water temperature and season

South Dakota Lake Trips

Where to stay at South Dakota's top lakes, each with its readings

Lakes near Sioux Falls

Cleanest lakes within 50 miles of Sioux Falls

Readings combine total phosphorus, total nitrogen, chlorophyll-a, and turbidity from the EPA Water Quality Portal and state agencies. See the full methodology, the national State of America’s Lakes report, or all South Dakota lakes.

Cite this report: LakeQuality, “The State of South Dakota's Lakes 2026”.