Big Mcdonald Lake vs Sybil Lake
Water quality, depth, fish species, and recreation comparison.
Big Mcdonald Lake and Sybil Lake both received the same overall water quality grade of A (Excellent). Both are in Otter Tail County, Minnesota.
Both Big Mcdonald Lake and Sybil Lake sit in Minnesota. A same-state comparison strips out the state-level water-quality regime as a variable: any grade differences here are about the lakes themselves, not the agencies grading them. These two are within a letter of each other on the rubric — Big Mcdonald Lake (A) versus Sybil Lake (A). 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.
Big Mcdonald Lake
Crystal clear, you can see 17.4 ft down.
Sybil Lake
Crystal clear, you can see 20 ft down.
Side-by-Side Metrics
| Metric | Big Mcdonald Lake | Sybil Lake |
|---|---|---|
| Overall Grade | A (Excellent) | A (Excellent) |
| Water Clarity | 17.4 ft | 20 ft |
| Phosphorus | 12 µg/L | 9 µg/L |
| Chlorophyll-a (Algae) | 3.2 µg/L | 2.4 µg/L |
| Maximum Depth | 46 ft | 74 ft |
| Surface Area | 992 acres | 683 acres |
| Public Access | Yes | Yes |
| Fish Species | 15 | 16 |
| Trophic State | oligotrophic | oligotrophic |
Bold value = better for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better).
Verdict
Both lakes earn the same Grade A. The tiebreakers come down to clarity (Big Mcdonald Lake: 17.4 ft, Sybil Lake: 20 ft) and what you want from the lake. Big Mcdonald Lake has fewer fish species than Sybil Lake.
Source: EPA National Aquatic Resource Surveys, 2026.