Updated August 2026
Cleanest Lakes in Indiana: Top 25 Ranked by Water Quality
Ranked from the Indiana lakes that carry an A–F grade. Lakes with fewer than three sampling years, and lakes nobody has sampled, are not rated and are not ranked here.
The single cleanest lake in Indiana is Lake George (Steuben County, IN), with the highest combined water quality score in our 2026 dataset (grade A). Cleanliness is measured by Secchi depth (clarity), total phosphorus, and chlorophyll-a — all sourced from EPA Water Quality Portal and state agency sampling. The full top 25 ranked list appears below.
Ranking the cleanest Indiana lakes means picking the basins with the strongest nutrient-and-algae letters, then the clearer water among lakes that share a letter. Lake George (Steuben County, IN) leads the list with a grade of A, with Lake Pleasant close behind.
The top of the cleanest-lakes list is dominated by deep, glacial, cold-water basins — the same basins that produce the A-grade bracket overall. The pattern is not coincidence: depth and watershed land-use are the dominant inputs to water-clarity and nutrient-loading both.
| Rank | Lake | County | Grade | Clarity | Phosphorus | Chlorophyll-a | Area |
|---|---|---|---|---|---|---|---|
| 1 | Lake George (Steuben County, IN) | Steuben | A | 14.5 ft | 22 µg/L | 2 µg/L | 538 acres |
| 2 | Lake Pleasant | Steuben | A | — | 23.5 µg/L | 4 µg/L | 355 acres |
| 3 | Lake James | Steuben | A | — | 21 µg/L | 2 µg/L | 1,883 acres |
| 4 | Myers Lake | Marshall | A | — | 23 µg/L | 3.5 µg/L | 92 acres |
| 5 | Lake Maxinkuckee | Marshall | A | — | 17.5 µg/L | 3 µg/L | 1,910 acres |
| 6 | Big Long Lake | LaGrange | A | — | 22 µg/L | 4 µg/L | 392 acres |
| 7 | Long Lake | Porter | B | — | 27 µg/L | 8 µg/L | 67 acres |
| 8 | Pike Lake | Kosciusko | C | 1.9 ft | 60.5 µg/L | 2 µg/L | - |
| 9 | Oswego Lake | Kosciusko | C | 9.9 ft | 33 µg/L | 2.2 µg/L | - |
| 10 | Tippecanoe Lake | Kosciusko | C | 8.5 ft | 28.5 µg/L | 5 µg/L | - |
| 11 | James Lake | Kosciusko | C | 5.3 ft | 30 µg/L | 7 µg/L | - |
| 12 | Brookville Lake | Union | C | — | 49 µg/L | 5.4 µg/L | 4,364 acres |
| 13 | Loomis Lake | Porter | C | — | 40 µg/L | 11.5 µg/L | 58 acres |
| 14 | Martin Lake | LaGrange | C | — | 22 µg/L | 3 µg/L | 26 acres |
| 15 | Olin Lake | LaGrange | C | — | 12.5 µg/L | 2 µg/L | 103 acres |
| 16 | Oliver Lake | LaGrange | C | — | 12.5 µg/L | 3 µg/L | 390 acres |
| 17 | Cordry Lake | Brown | C | — | 19.5 µg/L | 1.5 µg/L | 167 acres |
| 18 | Papakeechie Lake | Kosciusko | C | — | 29 µg/L | 4 µg/L | 187 acres |
| 19 | Shriner Lake | Whitley | C | — | 27 µg/L | 3.5 µg/L | 126 acres |
| 20 | Cedar Lake | Whitley | C | — | 25 µg/L | 3 µg/L | 102 acres |
| 21 | Big Turkey Lake | Steuben | D | — | 51 µg/L | 19 µg/L | 470 acres |
| 22 | Lake of the Wood | Marshall | D | — | 41 µg/L | 17 µg/L | 421 acres |
| 23 | Holem Lake | Marshall | D | — | 35 µg/L | 10 µg/L | 109 acres |
| 24 | Colonial Pond | Fulton | D | — | 49 µg/L | 19 µg/L | 810 acres |
| 25 | Lake Louise | Porter | D | — | 48 µg/L | 20.5 µg/L | 226 acres |
Get updates when Indiana's cleanest-lake list changes
New nutrient and algae samples can move a lake up or down this ranking. Unsubscribe anytime.
Clearest lakes in Indiana by water clarity
“Clearest” ranks by Secchi depth — how far you can see into the water — which can differ from the combined cleanliness score above. The clearest water in Indiana is Lake George at 14.5 ft of Secchi visibility.
- 1. Lake George — 14.5 ft, Steuben County
- 2. Dewart Lake — 10.2 ft, Kosciusko County
- 3. Oswego Lake — 9.9 ft, Kosciusko County
- 4. Koontz Lake — 9.8 ft, Starke County
- 5. Syracuse Lake — 8.8 ft, Kosciusko County
Frequently Asked Questions
What is the cleanest lake in Indiana?
Lake George (Steuben County, IN) has the highest water quality score in our 2026 Indiana dataset (grade A). Lakes are graded A to F on nutrients and algae — total phosphorus, total nitrogen, chlorophyll-a, and turbidity — measured against the EPA National Lakes Assessment 2022 condition classes for that lake's own ecoregion, so a lake is judged against the lakes it would naturally resemble. Cleanliness here means a low nutrient load and little algae, measured directly from EPA and state DNR samples; where two lakes tie on the letter, the deeper Secchi reading ranks first.
What is the most polluted lake in Indiana?
Among monitored Indiana lakes, Waldron Lake ranks among the most polluted by combined phosphorus and chlorophyll-a load. See our full ranking on the most-polluted-lakes trend page for state-by-state details.
Where in Indiana has the cleanest water?
Indiana's clearest waters are concentrated in deeper, lower-nutrient glacial basins with forested or low-agriculture watersheds. Among the current top-ranked lakes above, counties like Kosciusko, Steuben, and Marshall produce the highest-scoring lakes.
What is the clearest lake in Indiana?
Lake George is the clearest lake in Indiana by water clarity, with a Secchi depth of 14.5 feet — the deepest transparency in our 2026 dataset. "Clearest" ranks by Secchi depth (how far you can see into the water) specifically, while "cleanest" combines clarity with phosphorus and chlorophyll-a. See our full clearest-lakes ranking for Indiana for the top 25 by Secchi clarity.
Are these lakes safe to swim in?
Not on the letter alone. An A or B is a nutrients-and-algae classification, not a swimming clearance — it does not measure E. coli, cyanotoxins, or a posted beach closure, and a lake with low chlorophyll-a can still bloom. Always check current posted advisories before swimming: water quality changes seasonally, especially in late summer when blue-green algae bloom risk peaks.
How are these grades calculated?
The letter is nutrients and algae — phosphorus, nitrogen, chlorophyll-a, and turbidity — scored against EPA National Lakes Assessment 2022 condition classes for that lake’s ecoregion, not a Indiana-only 0–100 average and not an equal-weight mean with Secchi. Water clarity is shown; it is not scored. Lakes without enough recent sampling are UNRATED. Our methodology page has the full rubric.
What are the top 5 cleanest lakes in the US?
There is no single national ranking of cleanest lakes — each state agency uses different metrics. Crater Lake (Oregon) is widely cited as the clearest US lake, with Secchi depths over 30 m. Lake Tahoe and Lake Superior are also top-tier nationally. Within Indiana, the 25 lakes ranked above are the graded lakes with the highest letters in our 2026 dataset.
How we rank cleanest lakes
Cleanliness here means three things working together:
- Secchi clarity — how deep you can see into the water (in feet). Greater depth = clearer water = lower suspended sediment and algae.
- Total phosphorus — the nutrient that fuels algae. Lower phosphorus levels mean less algae growth potential.
- Chlorophyll-a — the green pigment in algae. Direct measurement of how much algae is currently in the water.
Each signal is normalized against Indiana state norms and combined into a single 0–100 score. The lakes above are sorted by that combined score.Full methodology →
More on clean water
The cleanest and dirtiest U.S. lakes in the monitoring record, ranked on EPA nutrient and algae condition classes across thousands of graded lakes.
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 U.S. lakes under 500 acres, ranked on measured nutrients, algae, and water clarity — with the size cutoff applied to the lake, not the sample.
A practical checklist for picking a lake with good water quality — clarity, phosphorus, algae history, depth, and the data to check before you commit.
Where to stay near Indiana's cleanest lakes
Compare cabins, resorts, and rentals around Lake George (Steuben County, IN) and the other lakes in this ranking, with live availability and prices for your trip. Each pin on the map is one of the ranked lakes above.
Top-rated places to stay near Lake George (Steuben County, IN)
Prices for Sep 11–13, 4 adults. Change dates on the map below.
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Source: EPA National Aquatic Resource Surveys, 2026.