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Mule Lake reads lower on nutrients and algae than Blackwater Lake. Both are in Cass County, Minnesota.

Reviewed by LakeQuality Editorial Team · Updated

Both Blackwater Lake and Mule Lake sit in Minnesota. 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: Blackwater Lake and Mule 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.

Blackwater Lake

Cass County, Minnesota

Good clarity, visible to about 14.1 ft.

Mule Lake

Cass County, Minnesota

Crystal clear, you can see 18 ft down.

Side-by-Side Metrics

MetricBlackwater LakeMule Lake
Water Clarity14.1 ft18 ft Better
Phosphorus12 µg/L10 µg/L Better
Chlorophyll-a (Algae)4 µg/L2.4 µg/L Better
Maximum Depth67 ft Better47 ft
Surface Area771 acres525 acres
Public AccessYesYes
Fish Species16 Better11
Trophic Statemesotrophicoligotrophic

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

Blackwater Lake and Mule Lake read the same on nutrients and algae overall. The tiebreakers come down to clarity (Blackwater Lake: 14.1 ft, Mule Lake: 18 ft) and what you want from the lake. Blackwater Lake supports more documented fish species.

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Where to stay near Blackwater Lake and Mule Lake

Compare cabins, hotels, and vacation rentals around Blackwater Lake and Mule 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.

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Source: EPA National Aquatic Resource Surveys, 2026.