Impaired Lakes in Indiana
15 of 22 graded Indiana lakes (68%) are officially listed as impaired under Clean Water Act §303(d) in the most recent EPA ATTAINS reporting cycle.
Top Causes of Impairment in Indiana
Reading the Indiana impairment landscape
68% of Indiana's tracked lakes — 15 of 22 — appear on the EPA Clean Water Act §303(d) impaired-waters list. At that share, impairment is the default state rather than an exception: the majority of lakes are flagged for at least one pollutant exceeding water-quality standards. Trip-planning for clean water in Indiana typically requires checking impairment status as a first filter, not as an edge case.
The leading impairment category in Indiana is Nutrients (phosphorus, nitrogen) — nutrient enrichment, typically from agricultural fertilizer runoff, septic discharge, or stormwater carrying lawn-care residue. Nutrient-impaired lakes can still be safe for contact recreation in many conditions, but they're prone to algal blooms (including potentially toxic cyanobacteria) during warm-water periods. Check the state's beach-monitoring or harmful-algal-bloom dashboard before swimming on nutrient-impaired waters in summer.
Impaired-waters listings come from the state environmental agency's §303(d) submission to EPA, refreshed on a roughly 2-year cycle. A listed lake stays on the list until either a TMDL is established and the cleanup completes, or subsequent monitoring shows the pollutant concentrations no longer exceed water-quality standards. The list below reflects the most recent available Indiana submission to the EPA Assessment, Total Maximum Daily Load Tracking and Implementation System (ATTAINS) dataset.
All 15 EPA-Listed Impaired Lakes in Indiana
| Lake | County | Grade | Causes | TMDL |
|---|---|---|---|---|
| Middle Lagoon Lake | Lake | A | PCBs | — |
| Oswego Lake | Kosciusko | B | Impaired biota (cause unknown) | — |
| Grand Calumet Lagoon Lake | Lake | B | PCBs | — |
| Big Chapman Lake | Kosciusko | C | Nutrients (phosphorus, nitrogen) | — |
| Tippecanoe Lake | Kosciusko | C | Impaired biota (cause unknown) | — |
| Center Lake | Kosciusko | C | Nutrients (phosphorus, nitrogen) | — |
| Koontz Lake | Starke | D | Nutrients (phosphorus, nitrogen) | — |
| Lake Wawasee | Kosciusko | D | PCBs | — |
| Webster Lake | Kosciusko | D | Nutrients (phosphorus, nitrogen) | — |
| James Lake | Kosciusko | D | Impaired biota (cause unknown) | — |
| Winona Lake | Kosciusko | F | PCBs | — |
| Yellow Creek Lake | Kosciusko | F | Nutrients (phosphorus, nitrogen) | — |
| Pike Lake | Kosciusko | F | Nutrients (phosphorus, nitrogen), PCBs | — |
| Beaver Dam Lake | Kosciusko | F | Nutrients (phosphorus, nitrogen) | — |
| Big Barbee Lake | Kosciusko | F | Nutrients (phosphorus, nitrogen) | — |
Frequently Asked Questions
How many lakes are impaired in Indiana?
15 of 22 graded Indiana lakes (68%) are listed as impaired in the most recent EPA ATTAINS reporting cycle. Of those, 15 are on the federal Clean Water Act §303(d) list and 0 have an approved Total Maximum Daily Load (TMDL) restoration plan.
What does Clean Water Act §303(d) mean?
Section 303(d) of the federal Clean Water Act requires every state to identify waters that don't meet water quality standards even after pollution control measures. Each listed water must then have a Total Maximum Daily Load (TMDL) developed — a plan that caps how much of each pollutant can enter the waterbody. The "303(d) list" is the impaired-waters list. The EPA reviews each state's list every two years.
What are the top causes of impairment in Indiana?
The most common causes flagged across Indiana's impaired lakes are: Nutrients (phosphorus, nitrogen) (8 lakes); PCBs (5 lakes); Impaired biota (cause unknown) (3 lakes). Mercury is widespread in fish tissue across the upper Midwest from atmospheric deposition. Nutrient impairment (phosphorus, nitrogen) typically reflects agricultural runoff and urban stormwater.
Can I swim in an impaired lake?
It depends on the cause of impairment. A lake impaired for "mercury in fish tissue" is generally safe to swim in — the warning is about long-term consumption of fish. A lake impaired for "pathogens" (E. coli) or "algal growth" may pose a swimming risk and often has a separate beach advisory. Check the cause categories listed for each lake below, and consult your state health department's beach monitoring program for current advisories.
Where does this impairment data come from?
Every impairment record on this page comes from the EPA's ATTAINS (Assessment and TMDL Tracking and Implementation System) public dataset, the federal repository of state-reported water quality assessments. EPA ATTAINS is published as GeoParquet files on the EPA Office of Water S3 bucket and refreshed several times per year. Causes and use-support codes follow EPA's standard taxonomy.
Data source
Impairment data from the EPA ATTAINS (Assessment and TMDL Tracking and Implementation System) public dataset. Assessment unit IDs are matched to LakeGrade waterbodies by name and proximity; some lakes may not appear here if their ATTAINS name doesn't match our naming convention. For an official query, consult Indiana's state water-quality agency.