Andrew Lake vs Mary Lake
Water quality, depth, fish species, and recreation comparison.
Andrew Lake and Mary Lake both received the same overall water quality grade of A (Excellent). Both are in Douglas County, Minnesota.
Both Andrew Lake and Mary 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 — Andrew Lake (A) versus Mary 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.
Andrew Lake
Good clarity, visible to about 13.9 ft.
Mary Lake
Good clarity, visible to about 10.5 ft.
Side-by-Side Metrics
| Metric | Andrew Lake | Mary Lake |
|---|---|---|
| Overall Grade | A (Excellent) | A (Excellent) |
| Water Clarity | 13.9 ft | 10.5 ft |
| Phosphorus | 17 µg/L | 20 µg/L |
| Chlorophyll-a (Algae) | 4 µg/L | 5.5 µg/L |
| Maximum Depth | 83 ft | 40 ft |
| Surface Area | 923 acres | 2,450 acres |
| Public Access | Yes | Yes |
| Fish Species | 18 | 17 |
| Trophic State | mesotrophic | mesotrophic |
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 (Andrew Lake: 13.9 ft, Mary Lake: 10.5 ft) and what you want from the lake. Andrew Lake supports more documented fish species.
Source: EPA National Aquatic Resource Surveys, 2026.