Decatur Lake vs Mattoon Lake
Water quality, depth, fish species, and recreation comparison.
Decatur Lake reads lower on nutrients and algae than Mattoon Lake. Both are in Illinois.
Both Decatur Lake and Mattoon Lake sit in Illinois. A same-state comparison strips out the state-level water-quality regime as a variable: any differences in the readings here are about the lakes themselves, not the agencies sampling them. The readings are close: Decatur Lake and Mattoon Lake sit within a narrow band of each other on phosphorus, chlorophyll-a and clarity. The per-parameter table below shows where the small differences actually live.
With readings this close, the choice between the two lakes turns on non-water-quality factors: depth, fish species, public access, distance from home. The per-lake pages below cover all of those.
Decatur Lake
Very murky, less than 1.3 ft of visibility.
Mattoon Lake
Very murky, less than 1.3 ft of visibility.
Side-by-Side Metrics
| Metric | Decatur Lake | Mattoon Lake |
|---|---|---|
| Water Clarity | 1.3 ft | 1.3 ft |
| Phosphorus | 103 µg/L Better | 294 µg/L |
| Chlorophyll-a (Algae) | 25 µg/L Better | 87.1 µg/L |
| Maximum Depth | - | - |
| Surface Area | 3,335 acres | 980 acres |
| Public Access | Yes | Yes |
| Fish Species | 0 | 0 |
| Trophic State | eutrophic | hypereutrophic |
A green ✓ marks the better value for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better). Surface area and trophic state carry no tick — a bigger lake is not a better lake.
Swap a lake
Compare Decatur Lake or Mattoon Lake against a different lake.
Verdict
Decatur Lake reads lower on nutrients and algae than Mattoon Lake. Water clarity: 1.3 ft vs 1.3 ft. For fishing diversity, Decatur Lake also leads with 0 species.
Stays via Stay22
Where to stay near Decatur Lake and Mattoon Lake
Compare cabins, hotels, and vacation rentals around Decatur Lake and Mattoon Lake. Both lakes are pinned on the map, so you can see which stays sit nearer the one you pick. Switch to Satellite to see how close each is to the water.
Top-rated places to stay near Decatur Lake and Mattoon Lake
Prices for Oct 23–25, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a trip to Decatur Lake and Mattoon Lake?
Get lake water-quality updates plus the best cabin & lodging deals near Decatur Lake and Mattoon Lake — straight to your inbox. No spam, unsubscribe anytime.
Source: EPA National Aquatic Resource Surveys, 2026.