Decatur Lake vs Sara Lake
Water quality, depth, fish species, and recreation comparison.
Decatur Lake has a higher water quality grade (D, Nutrient-rich) than Sara Lake (F, Algae-prone). Both are in Illinois.
Decatur Lake and Sara Lake are both in Illinois — a same-state head-to-head where the comparison comes down to lake-specific differences in depth, watershed, and monitoring history rather than the broader state-level water-quality regime. These two are within a letter of each other on the rubric — Decatur Lake (D) versus Sara Lake (F). The deciding factors for a recreational visitor are likely physical (depth, access, fish species) rather than water-quality differences.
With grades 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.
Sara Lake
Very murky, less than 2.2 ft of visibility.
Side-by-Side Metrics
| Metric | Decatur Lake | Sara Lake |
|---|---|---|
| Overall Grade | D (Nutrient-rich) Better | F (Algae-prone) |
| Water Clarity | 1.3 ft | 2.2 ft Better |
| Phosphorus | 103 µg/L | 59.5 µg/L Better |
| Chlorophyll-a (Algae) | 25 µg/L Better | 33.9 µg/L |
| Maximum Depth | - | - |
| Surface Area | 3,335 acres | 586 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 Sara Lake against a different lake.
Verdict
Decatur Lake wins on overall water quality with a Grade D versus Sara Lake's Grade F. Water clarity: 1.3 ft vs 2.2 ft. For fishing diversity, Decatur Lake also leads with 0 species.
Source: EPA National Aquatic Resource Surveys, 2026.