Horseleg Lake
Isanti County, MinnesotaMesotrophic
On the LakeGrade scale Horseleg Lake grades a B, with clarity at 3.7 ft and 17 µg/L of phosphorus placing it above the Minnesota median. Secchi readings are the weakest of the scored parameters, suggesting suspended sediment or algal biomass dominates the optical signal.
Mesotrophic conditions dominate at Horseleg Lake: enough nutrients for a healthy fishery, not so much that algal blooms become a chronic problem. 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. Horseleg Lake ranks 6 of 19 in Isanti County — solidly in the upper half of the local distribution.
No invasive species are currently listed at Horseleg Lake — the lake remains off the Minnesota infested-waters roster. The state fisheries records do not list documented species for Horseleg Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. No formal public access is documented at Horseleg Lake — most use is by shoreline residents and their guests. Multiple sampling years from Minnesota PCA volunteers and partner agencies back the grade, so the letter should hold steady absent a major watershed shift.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-09-18. Grade methodology: LakeGrade methodology.
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Swimming Safety
Good for swimming, clear water with low algae levels
Water Quality Grade: B, Good
Murky, only visible to about 3.7 ft. Phosphorus level: 17 µg/L. Chlorophyll-a: 4 µg/L. Trophic State Index: 49.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.7 ft | D |
| Phosphorus | 17 µg/L | A |
| Chlorophyll-a (Algae) | 4 µg/L | A |
| Trophic State Index (TSI) | 49 | Mesotrophic |
Moderate nutrients, good water quality
Water Quality Trend: ↓ Declining
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.731 m/yr | 5 |
| Phosphorus | ↓ Declining | +0.75 µg/L/yr | 5 |
| Chlorophyll-a | ↑ Improving | -1.3 µg/L/yr | 2 |
Location
County Ranking
Ranked #6 of 19 lakes in Isanti County
Cleaner Lakes Within 30 Miles
Horseleg Lake holds Grade B. 2 nearby lakes hold higher grades.
- ALower Birch LakeIsanti County · mi · Higher grade (B → A)
- AUpper Birch LakeIsanti County · mi · Higher grade (B → A)
Nearby Lakes in Isanti County
More Minnesota Lake Rankings
State Parks Near Horseleg Lake
Other Grade B Lakes in Minnesota
Mesotrophic Lakes in Minnesota
EPA Impairment Status
Horseleg Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit MN30-0004-00 · Official waterbody report · Matched by proximity (2.61 km)
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Grading methodology based on Metropolitan Council standards
Most recent sample: 2024-09-18
Monitoring stations: 1