Mattoon Lake
Cumberland County, WisconsinHypereutrophic
Mattoon Lake is a 980-acre highly nutrient-loaded hypereutrophic lake in Cumberland County, IL. Water quality is graded F based on 2 sampling years through 2022.
Source: EPA Water Quality Portal sampling records, local state DNR records, last sampled 2022-10-27. Grade methodology: LakeGrade methodology.
Swimming Safety
Avoid swimming, very poor water quality, potential algae toxins
Water Quality Grade: F, Very Poor
Very murky, less than 1.3 ft of visibility. Phosphorus level: 206 µg/L. Trophic State Index: 77.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.3 ft | F |
| Phosphorus | 206 µg/L | F |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 77 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 980 acres |
Location
County Ranking
Ranked #1 of 1 lakes in Cumberland County
Cleaner Lakes Within 30 Miles
Mattoon Lake holds Grade F. One nearby lake has a higher grade.
See full comparison →Nearby Lakes in Cumberland County
More Wisconsin Lake Rankings
Other Grade F Lakes in Wisconsin
Hypereutrophic Lakes in Wisconsin
Reservoir Info (USACE NID)
Mattoon Lake is a man-made reservoir impounded by the Lake Mattoon Dam (completed 1957), built primarily for recreation on the LITTLE WABASH RIVER; earth-type dam, 46 ft tall and 2,250 ft long.
- Surface area
- 980 ac
- Normal storage
- 11,820 ac-ft
- Max storage
- 22,569 ac-ft
- Drainage area
- 57 sq mi
- Hazard class
- Significant
- Owner
- CITY OF MATTOON
All listed purposes: Recreation;Water Supply.
Source: USACE National Inventory of Dams, NID ID IL00141 · Operator website
EPA Impairment Status
Mattoon Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IL_RCF · Official waterbody report
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Grading methodology based on Metropolitan Council standards
Most recent sample: 2022-10-27
Monitoring stations: 5