Updated Aug 2026
Indiana Lake Water Quality
Water quality grades for 2 of the 387 lakes we list here, across 64 counties.
Grade Distribution
All 387 Indiana lakes in the index: 2 (0.5%) carry an A–F grade and 385 (99.5%) are not rated, because they lack enough recent nutrient or algae sampling to support a letter.
Top-Graded Indiana Lakes
The highest water-quality grades in Indiana — clarity, depth, and A-F grade at a glance.
Lake Map
Get Indiana water-quality updates
New grades, clarity readings, and algae advisories for Indiana lakes as samples come in. Unsubscribe anytime.
Where to stay near Indiana's top-graded lakes
Cabins, resorts, and vacation rentals around Middle Lagoon Lake and the other top-graded Indiana lakes pinned on the map. Live availability and prices.
Top-rated places to stay near Middle Lagoon Lake
Prices for Sep 11–13, 4 adults. Change dates on the map below.
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Explore Indiana Lakes
Indiana reports, fishing & travel
Indiana's cleanest and most-polluted lakes, ranked A–F
Species activity outlook by water temperature and season
Where to stay at Indiana's top lakes, each with its grade
Best-graded lakes within 50 miles of Indianapolis
Best-graded lakes within 50 miles of Fort Wayne
Reservoirs in Indiana
View all 5 reservoirs →5 of 387 Indiana lakes (1%) are man-made reservoirs in the USACE National Inventory of Dams. 5 carry a High or Significant hazard rating. The oldest matched dam dates to 1835.
EPA-Impaired Lakes in Indiana
View all 15 impaired lakes →15 of 387 Indiana lakes (4%) are officially listed as impaired under Clean Water Act §303(d) in the most recent EPA ATTAINS reporting cycle.
Indiana Fishing & Recreation
Licenses, regulations, records, and where to fish across Indiana.
Counties
All 64 Indiana 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.
Indiana Lake Water Quality Dataset (2026)
Every graded Indiana 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.
Cleanest Indiana Lakes
2 lakes2 graded lakes
| # | Lake | County | Grade | Clarity | Trophic | Access |
|---|---|---|---|---|---|---|
| 1 | BMiddle Lagoon Lake | Lake | B | No recent samples | Oligotrophic | Not recorded |
| 2 | CGrand Calumet Lagoon Lake | Lake | C | No recent samples | Mesotrophic | Not recorded |
Indiana Lakes Needing Attention
2 lakes2 graded lakes
| # | Lake | County | Grade | Clarity |
|---|---|---|---|---|
| 1 | CGrand Calumet Lagoon Lake | Lake | C | No recent samples |
| 2 | BMiddle Lagoon Lake | Lake | B | No recent samples |
2 of the 387 Indiana lakes in this index carry an A–F water-quality grade, spread over 64 counties. Those grades rest on measurements from the Indiana Department of Environmental Management, alongside federal programs and volunteer monitoring networks. The rest are listed for their size, depth and location, without enough recent nutrient or algae sampling behind them to support a letter.
By surface area the largest lake here is Brookville Lake, at about 4,364 acres, and 19 of the lakes in this index cover more than 500 acres. Size is worth knowing before you go: a large deep basin buffers nutrient inputs by sheer volume, while a shallow one warms quickly and can turn over its whole water column in a single summer storm. The cleanest county on average is Lake (grade B); the most-stressed is Lake. The gap between the top and bottom counties is large enough that a single figure for Indiana 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.