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Jacksonville Lake reads lower on nutrients and algae than Otter Lake. Both are in Illinois.

Reviewed by LakeQuality Editorial Team · Updated

Both Jacksonville Lake and Otter 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. These two sit close on their nutrient and algae readings, Jacksonville Lake versus Otter Lake. The deciding factors for a recreational visitor are likely physical (depth, access, fish species) rather than water-quality differences.

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.

Jacksonville Lake

Morgan County, Illinois

Very murky, less than 1.8 ft of visibility.

Otter Lake

Macoupin County, Illinois

Very murky, less than 1.8 ft of visibility.

Side-by-Side Metrics

MetricJacksonville LakeOtter Lake
Water Clarity1.8 ft1.8 ft
Phosphorus60.5 µg/L Better81 µg/L
Chlorophyll-a (Algae)42.2 µg/L33.1 µg/L Better
Maximum Depth--
Surface Area477 acres760 acres
Public AccessYesYes
Fish Species00
Trophic Statehypereutrophichypereutrophic

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.

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Verdict

Jacksonville Lake and Otter Lake read the same on nutrients and algae overall. The tiebreakers come down to clarity (Jacksonville Lake: 1.8 ft, Otter Lake: 1.8 ft) and what you want from the lake. Jacksonville Lake matches its peer on species count.

Stays via Stay22

Where to stay near Jacksonville Lake and Otter Lake

Compare cabins, hotels, and vacation rentals around Jacksonville Lake and Otter 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 Jacksonville Lake and Otter Lake

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Source: EPA National Aquatic Resource Surveys, 2026.