Updated Aug 2026
South Dakota Lake Water Quality
Water quality grades for 2 of the 469 lakes we list here, across 59 counties.
Grade Distribution
All 469 South Dakota lakes in the index: 2 (0.4%) carry an A–F grade and 467 (99.6%) are not rated, because they lack enough recent nutrient or algae sampling to support a letter.
Lake Map
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Where to stay near South Dakota's top-graded lakes
Cabins, resorts, and vacation rentals around Traverse Lake and the other top-graded South Dakota lakes pinned on the map. Live availability and prices.
Top-rated places to stay near Traverse Lake
Prices for Sep 11–13, 4 adults. Change dates on the map below.
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Explore South Dakota Lakes
South Dakota reports, fishing & travel
South Dakota's cleanest and most-polluted lakes, ranked A–F
Species activity outlook by water temperature and season
Where to stay at South Dakota's top lakes, each with its grade
Best-graded lakes within 50 miles of Sioux Falls
Reservoirs in South Dakota
View all 1 reservoirs →1 of 469 South Dakota lakes (0%) are man-made reservoirs in the USACE National Inventory of Dams. 1 carry a High or Significant hazard rating. The oldest matched dam dates to 1976.
EPA-Impaired Lakes in South Dakota
View all 1 impaired lakes →1 of 469 South Dakota lakes (0%) are officially listed as impaired under Clean Water Act §303(d) in the most recent EPA ATTAINS reporting cycle.
South Dakota Fishing & Recreation
Licenses, regulations, records, and where to fish across South Dakota.
Counties
All 59 South Dakota counties, ranked by average lake water quality. Compare them against every county nationwide in the county rankings, browse the full directory of graded lakes, or pick a different state.
South Dakota Lake Water Quality Dataset (2026)
Every graded South Dakota lake in one spreadsheet — A–F grade, water clarity, phosphorus, chlorophyll-a, trophic state, size, public access, and a link to each lake's report card.
South Dakota Lakes Needing Attention
2 lakes2 graded lakes
| # | Lake | County | Grade | Clarity |
|---|---|---|---|---|
| 1 | FTraverse Lake | Roberts | F | 3.9 ft |
| 2 | FBig Stone Lake | Roberts | F | 3 ft |
South Dakota lists 469 lakes across 59 counties, 2 of which carry a grade. Most of the input behind those grades flows through monitoring run by the South Dakota Department of Agriculture and Natural Resources, which feeds state, federal, and volunteer measurements into the EPA Water Quality Portal. The remainder are here because they are real named lakes, not because anyone has sampled them recently.
Dry Lake Number Two is the largest lake in this index at about 6,442 acres, one of 56 here that clear 500 acres. The rest run smaller, and small and shallow is where nutrient loading shows up first, because there is less water to dilute it and the bottom sediment stays within reach of the sun. The cleanest county on average is Roberts (grade F); the most-stressed is Roberts. The gap between the top and bottom counties is large enough that a single figure for South Dakota lake water quality hides real local variation.
Lake Match
Which lake suits how you actually use one?
Six questions — swimming, fishing, quiet, cabins, drive time — and a shortlist of graded lakes that fit, with the water quality behind each one.
Source: EPA National Aquatic Resource Surveys and the EPA Water Quality Portal.
More on lake water quality
A data snapshot of the lakes we grade: how the A–F distribution breaks down, the clearest and the greenest states, and where the water is improving.
How lakes are graded A–F on nutrients and algae using EPA ecoregion condition classes, what each letter means in the water, and why an A is not a clearance.
The cleanest and dirtiest U.S. lakes in the monitoring record, ranked on EPA nutrient and algae condition classes across thousands of graded lakes.
The clearest lakes in America, ranked by measured Secchi depth in feet from EPA monitoring data — and why the famously clear lakes are missing.