Leech Lake
Cass County, MinnesotaMesotrophic
On the LakeGrade scale Leech Lake grades a B, with clarity at 12.5 ft and 12 µg/L of phosphorus placing it above the Minnesota median. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.
A TSI near 42 places Leech Lake in the mesotrophic band — moderate productivity, with seasonal swings between clearer spring water and richer late-summer conditions. 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. Leech Lake sits at rank 83 of 132 in Cass County, in the lower half of the local distribution.
Zebra mussel presence at Leech Lake means the lake's clarity numbers carry an asterisk — filtered water is not the same as nutrient-poor water. The state fisheries records do not list documented species for Leech Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. Public access is available — the lake is on the Minnesota PCA public-access list. Ice-out has been logged at Leech Lake more than two dozen times, putting the median around Apr 28 — a useful baseline for tracking climate trends. The grade is supported by multiple sampling years from Minnesota PCA volunteers and partner agencies, giving the letter a reasonably stable foundation.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-10-10. 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 12.5 ft. Phosphorus level: 11.5 µg/L. Chlorophyll-a: 5.3 µg/L. Trophic State Index: 42.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 12.5 ft | B |
| Phosphorus | 11.5 µg/L | A |
| Chlorophyll-a (Algae) | 5.3 µg/L | B |
| Trophic State Index (TSI) | 42 | Mesotrophic |
Moderate nutrients, good water quality
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
Water Quality Trend: ↑ Improving
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.239 m/yr | 5 |
| Phosphorus | → Stable | +0.1 µg/L/yr | 5 |
| Chlorophyll-a | ↑ Improving | -0.7 µg/L/yr | 2 |
Ice Season
Historical ice data from Minnesota DNR (74 observations).
Estimated open water season: 200 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 1945-04-09 (1945) | 1950-05-23 (1950) |
| Ice-In | 2018-11-13 (2018) | 2021-11-25 (2021) |
Most recent ice-out: 2022-05-08
Location
County Ranking
Ranked #83 of 132 lakes in Cass County
Cleaner Lakes Within 30 Miles
Leech Lake holds Grade B. 5 nearby lakes hold higher grades.
- AWalker Bay LakeCass County · mi · Higher grade (B → A)
- AAgency Bay LakeCass County · mi · Higher grade (B → A)
- AJack LakeCass County · mi · Higher grade (B → A)
- AKabekona Bay LakeCass County · mi · Higher grade (B → A)
- ATraders Bay LakeCass County · mi · Higher grade (B → A)
Nearby Lakes in Cass County
More Minnesota Lake Rankings
Other Grade B Lakes in Minnesota
Mesotrophic Lakes in Minnesota
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Leech Lake. 1 report on file.
- —Public Water Access Sites — Leech (Main Basin)Public Water Access Sites · MN DNR LakeFinder
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Ice data from Minnesota DNR Climate
Most recent sample: 2024-10-10
Monitoring stations: 11