Updated Aug 2026
Indiana Lake Water Quality
Water quality grades for 22 monitored lakes across 7 counties.
Indiana has 22 graded lakes in our dataset, sampled across 7 counties, drawing on monitoring by the Indiana Department of Environmental Management plus federal and volunteer measurements. Only about 0% of Indiana's lakes pull an A grade — the smaller, agricultural-watershed lakes that dominate the dataset tend to carry persistent nutrient loads. 0% of lakes fall in the D or F brackets.
The state's dominant trophic class is oligotrophic: clear, nutrient-poor, slow-growing. These lakes are also the most sensitive to disturbance — the same volume that buffers them against nutrients also slows recovery if those nutrients arrive in quantity. Lake ranks highest on average county grade (B). Lake sits lowest. With only 7 counties in the state, the cross-county spread is narrower than the within-county spread for most lakes.
Grade Distribution
All 22 Indiana lakes in the index: 2 (9.1%) carry an A–F grade and 20 (90.9%) are not rated, because they lack enough recent nutrient or algae sampling to support a letter.
Where to stay near Indiana
Top-rated places to stay near Indiana
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Top-Graded Indiana Lakes
The highest water-quality grades in Indiana — clarity, depth, and A-F grade at a glance.
Lake Map
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 22 Indiana lakes (23%) 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 22 Indiana lakes (68%) 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 7 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 |
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
The top-graded lake in every state we cover, picked grade-first with water clarity as the tie-breaker — plus the states whose winner is still not clean.
State-by-state Secchi champions: the clearest measured lake in each U.S. state we grade, which is not the same as the cleanest nutrient grade.
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.