Updated Aug 2026
South Dakota Lake Water Quality
469 lakes across 59 counties, 14 with a recent water-quality reading.
Lake Map
Get South Dakota water-quality updates
New water-quality readings for South Dakota lakes as SD DANR publishes them. Unsubscribe anytime.
Where to stay near South Dakota's cleanest lakes
Cabins, resorts, and vacation rentals around Canyon Lake (Pennington County, SD) and the other cleanest South Dakota lakes pinned on the map. Live availability and prices.
Top-rated places to stay near Canyon Lake (Pennington County, SD)
Prices for Oct 30–Nov 1, 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 lakes, ranked on agency measurements
Species activity outlook by water temperature and season
Where to stay at South Dakota's top lakes, each with its readings
Cleanest 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 54 impaired lakes →54 of 469 South Dakota lakes (12%) are officially listed as impaired under Clean Water Act §303(d) in the most recent EPA ATTAINS reporting cycle. 39 have an approved Total Maximum Daily Load (TMDL) restoration plan.
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 lakes, or pick a different state.
South Dakota Lake Water Quality Dataset (2026)
Every measured South Dakota lake in one spreadsheet — water clarity, phosphorus, chlorophyll-a, trophic state, size, public access, and a link to each lake's page.
South Dakota lists 469 lakes across 59 counties, 14 of them with a recent water-quality reading. Most of that sampling 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 county with the lowest nutrient and algae readings on average is Pennington. The gap between 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 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 track: the clearest and the greenest states, and where the water is improving.
How nutrient and algae readings are read against EPA ecoregion condition classes, what each class means in the water, and why a clean reading is not a clearance.
The clearest lakes in America, ranked by measured Secchi depth in feet from EPA monitoring data — and why the famously clear lakes are missing.