Long Lake
Todd County, MinnesotaLimited DataOligotrophic
Long Lake carries a solid B grade — strong on most parameters, with measurements that hold up well across the summer season.
The lake's low TSI puts it in oligotrophic territory — the cleanest of the four trophic classes, but also the most vulnerable to nutrient-driven shifts. 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. Long Lake ranks 6 of 17 in Todd County — solidly in the upper half of the local distribution.
Long Lake has no invasive species recorded in Minnesota state databases as of 2024, though prevention practices still apply at all access points. The state fisheries records do not list documented species for Long Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. A documented public access point at Long Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. Ice-out has been logged at Long Lake more than two dozen times, putting the median around Apr 13 — a useful baseline for tracking climate trends. 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 2024-08-13. Grade methodology: LakeGrade methodology.
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Swimming Safety
Good for swimming, clear water with low algae levels
Water Quality Grade: B, Good
Good clarity, visible to about 14 ft. Trophic State Index: 39.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 14 ft | B |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 39 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Water Quality Trend: → Stable
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.07 m/yr | 5 |
Ice Season
Historical ice data from Minnesota DNR (64 observations).
Estimated open water season: 229 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2024-03-12 (2024) | 2018-05-02 (2018) |
| Ice-In | 2018-11-13 (2018) | 2015-12-19 (2015) |
Most recent ice-out: 2024-03-12
Location
County Ranking
Ranked #6 of 17 lakes in Todd County
Cleaner Lakes Within 30 Miles
Long Lake holds Grade B. One nearby lake has a higher grade.
Nearby Lakes in Todd County
More Minnesota Lake Rankings
Other Grade B Lakes in Minnesota
Oligotrophic Lakes in Minnesota
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Long Lake. 1 report on file.
- —Public Water Access Sites — Long (Main Basin)Public Water Access Sites · MN DNR LakeFinder
EPA Impairment Status
Long Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN77-0150-02 · Official waterbody report · Matched by proximity (2.96 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
Ice data from Minnesota DNR Climate
Most recent sample: 2024-08-13
Monitoring stations: 2