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LakeQuality
Late afternoon sun over Slim Lake, scattering a bright path across wind-textured water

Sully County Lake Quality

South Dakota, 9 lakes, measured by SD DANR

Sully County has 9 monitored lakes — a thin enough sample that one or two stressed lakes can move the county average noticeably. Use the per-lake pages below for what actually matters. The 9 monitored lakes in Sully County carry whatever clarity, phosphorus, and chlorophyll-a readings SD DANR has published, shown as reported.

Most of the county's monitored lakes are shallow, under 50 feet, which means wind keeps the water column mixed all summer and sediment-bound phosphorus releases back into the surface layer whenever the bottom is disturbed.

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Where to stay near Sully County

Top-rated places to stay near Sully County

Prices for Oct 23–25, 4 adults. Change dates on the map below.

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Quick Answers for Sully County

Cleanest lakes in Sully County →Best swimming lakes in South Dakota →

Planning a trip? Check special fishing regulations for Fuller Lake — or check the official South Dakota fishing regulations.

All Lakes in Sully County

9 lakes · 0 ranked on readings, 9 without enough sampling0 lakes ranked on readings · 9 without enough sampling, hidden

#LakeClarityPhosphorusAlgaeTrophicAccess
Fuller LakeSullyNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
Lake OkobojoSullyNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
Post LakeSullyNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
Walker LakeSullyNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
Durrstein LakeSullyNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
Warnes SloughSullyNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
Sully LakeSullyNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
Stone LakeSullyNo recent samplesNo recent samples18.1 µg/LNo recent samplesNot recorded
Cottonwood LakeSullyNo recent samplesNo recent samplesNo recent samplesNo recent samples✓ Public

NR = no nutrient or algae reading on record. The measurements are published as the authority reports them. Where the data comes from.

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Other Counties in South Dakota

Pennington County

2 lakes

Roberts County

20 lakes

Hughes County

2 lakes

Charles Mix County

8 lakes

Walworth County

4 lakes

Butte County

2 lakes

Browse every South Dakota lake, or the full directory of lakes across all United States (49 states), Canada (Ontario, Québec, Nova Scotia, British Columbia and Newfoundland and Labrador), and 38 other country hubs..

Source: the South Dakota Department of Agriculture and Natural Resources. See data sources.