Emerald Lake
Beltrami County, MinnesotaOligotrophic
Emerald Lake earns an A — water clarity, phosphorus, and chlorophyll-a all rate among the best monitored waters in Beltrami County. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.
Trophically, Emerald Lake reads as oligotrophic — nutrient-poor, clear, and ecologically more sensitive to disturbance than richer lakes. The lake's maximum depth is not yet documented in state morphometric records — context for its physical structure remains limited. The lake's surface area is not consistently recorded across state datasets — physical context remains partial. Among the 86 graded lakes in Beltrami County, Emerald Lake ranks 5 — in the top quartile locally.
Emerald Lake has no invasive species recorded in Minnesota state databases as of 2025, though prevention practices still apply at all access points. The state fisheries records do not list documented species for Emerald Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. Monitoring depth is thin here: the LakeGrade rubric is applied to a small number of sample years, and the grade will be revised as more data accumulates.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-23. Grade methodology: LakeGrade methodology.
Swimming Safety
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A, Excellent
Crystal clear, you can see 31.2 ft down. Phosphorus level: 12 µg/L. Trophic State Index: 34.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 31.2 ft | A |
| Phosphorus | 12 µg/L | A |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 34 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Water Quality Trend: ↑ Improving
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.657 m/yr | 6 |
| Phosphorus | ↑ Improving | -0.99 µg/L/yr | 6 |
Location
County Ranking
Ranked #5 of 86 lakes in Beltrami County
Nearby Lakes in Beltrami County
More Minnesota Lake Rankings
State Parks Near Emerald Lake
Other Grade A Lakes in Minnesota
Oligotrophic Lakes in Minnesota
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Most recent sample: 2025-09-23
Monitoring stations: 1