Gull Lake vs Three Island Lake
Water quality, depth, fish species, and recreation comparison.
Three Island Lake has a higher water quality grade (A, Excellent) than Gull Lake (C, Fair). Both are in Beltrami County, Minnesota.
Gull Lake and Three Island Lake are both in Minnesota — 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. Three Island Lake (A) is materially cleaner than Gull Lake (C). A gap that wide is unlikely to close in a single year of remediation work; it reflects multi-decade differences in the lakes themselves.
For a recreational visitor, the wider grade gap is decisive — Three Island Lake is the better water-quality choice. For a researcher, the gap is the interesting part: what is different about the two watersheds, and which of those differences is mutable?
Gull Lake
Moderate clarity, visible to about 7.9 ft.
Three Island Lake
Good clarity, visible to about 11.8 ft.
Side-by-Side Metrics
| Metric | Gull Lake | Three Island Lake |
|---|---|---|
| Overall Grade | C (Fair) | A (Excellent) |
| Water Clarity | 7.9 ft | 11.8 ft |
| Phosphorus | 26 µg/L | 17 µg/L |
| Chlorophyll-a (Algae) | 6.3 µg/L | 4.1 µg/L |
| Maximum Depth | 23 ft | 25 ft |
| Surface Area | 2,256 acres | 729 acres |
| Public Access | Yes | Yes |
| Fish Species | 13 | 17 |
| Trophic State | mesotrophic | mesotrophic |
Bold value = better for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better).
Verdict
Three Island Lake wins on overall water quality with a Grade A versus Gull Lake's Grade C. Water clarity: 11.8 ft vs 7.9 ft. For fishing diversity, Three Island Lake also leads with 17 species.
Source: EPA National Aquatic Resource Surveys, 2026.