Updated Jul 2026
South Dakota Lake Water Quality
Water quality grades for 4 monitored lakes across 13 counties.
4 South Dakota lakes carry a grade. Most of the input data 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. About 25% of graded South Dakota lakes earn an A. The bulk sit in the middle B–C range; 75% fall into D or F, almost all of those in counties where row-crop agriculture dominates the watershed.
Eutrophic conditions dominate — nutrient-loaded, productive, with algal pressure that shows up most years in late summer. These lakes tend to be shallow, agricultural-watershed, and over-warmed by the time July ends. Pennington ranks highest on average county grade (A). Roberts sits lowest. With only 13 counties in the state, the cross-county spread is narrower than the within-county spread for most lakes.
Grade Distribution
How South Dakota’s 4 graded lakes break down from A (excellent) to F.
Top-Graded South Dakota Lakes
The highest water-quality grades in South Dakota — clarity, depth, and A-F grade at a glance.
Canyon Lake
Pennington County, South Dakota
See grade for Canyon Lake →Lake Andes
Charles Mix County, South Dakota
See grade for Lake Andes →Traverse Lake
Roberts County, South Dakota
See grade for Traverse Lake →Big Stone Lake
Roberts County, South Dakota
See grade for Big Stone Lake →Lake Map
Explore South Dakota Lakes
South Dakota reports, fishing & travel
Reservoirs in South Dakota
View all 1 reservoirs →1 of 4 South Dakota lakes (25%) 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.
South Dakota Fishing & Recreation
Licenses, regulations, records, and where to fish across South Dakota.
Counties
All 13 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.
Top 25 Cleanest Lakes
| Rank | Lake | County | Grade | Clarity |
|---|---|---|---|---|
| 1 | Canyon Lake | Pennington | A | - |
| 2 | Lake Andes | Charles Mix | D | - |
| 3 | Traverse Lake | Roberts | D | 3.9 ft |
| 4 | Big Stone Lake | Roberts | F | 3 ft |
25 Lakes Needing Attention
| Rank | Lake | County | Grade | Clarity |
|---|---|---|---|---|
| 1 | Big Stone Lake | Roberts | F | 3 ft |
| 2 | Traverse Lake | Roberts | D | 3.9 ft |
| 3 | Lake Andes | Charles Mix | D | - |
| 4 | Canyon Lake | Pennington | A | - |
Where to stay near South Dakota
Top-rated places to stay near South Dakota
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Source: EPA National Aquatic Resource Surveys, 2026.