Is Little River Lake Polluted?
Yes — Little River Lake in Decatur County, Iowa is on the EPA's Clean Water Act 303(d) impaired-waters list (2024 assessment cycle). It is cited for Mercury, Pathogens (E. coli, fecal). A formal cleanup plan — a Total Maximum Daily Load (TMDL) — has been written. "Impaired" is a legal designation, separate from the lake's A–F water-quality grade: it means at least one designated use (such as swimming, aquatic life, or fish consumption) does not meet state standards for the listed pollutant.
EPA 303(d) Listing
| On 303(d) impaired list | Yes |
| Cleanup plan (TMDL) | Completed |
| Assessment cycle | 2024 |
| EPA IR category | 5 |
| Location | Decatur County, Iowa |
Pollutants Cited
- Mercury — Mercury accumulates in fish tissue and is the single most common impairment in northern lakes. It usually arrives via atmospheric deposition from coal combustion rather than local discharge — which is why even remote, clear lakes can be mercury-impaired. It triggers fish-consumption advisories, not swimming closures.
- Pathogens (E. coli, fecal) — listed by EPA as exceeding water-quality standards for at least one designated use.
Specific parameters in the EPA record: ESCHERICHIA COLI (E. COLI), MERCURY - FISH CONSUMPTION ADVISORY.
What this means for using Little River Lake
Because Little River Lake is listed for Pathogens (E. coli, fecal), swimming can be affected — check for posted beach advisories, especially after heavy rain or during visible algae. An impairment listing does not mean the lake is closed — most impaired lakes remain open for boating and swimming. It means a specific pollutant exceeds a standard for a specific use. Little River Lake carries an overall water-quality grade of F, with algae (chlorophyll-a) at 70 µg/L and phosphorus at 85 µg/L — see the full breakdown on the lake report. The official EPA assessment is available in the ATTAINS waterbody report.
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