Little Lake Deep
Cook County, MinnesotaMesotrophic
Little Lake Deep comes in at a B on the grading rubric — a respectable showing for a Minnesota lake of its size and depth. Secchi readings are the weakest of the three parameters, suggesting suspended sediment or algal biomass dominates the optical signal.
The lake sits in the mesotrophic zone — the band where most well-managed Minnesota lakes fall. 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. Within Cook County's 128 graded lakes, Little Lake Deep ranks 65 — below the local median, though not at the bottom.
Zebra mussel presence at Little Lake Deep 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 Little Lake Deep, 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. 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 2024-09-09. Grade methodology: LakeGrade methodology.
Swimming Safety
Good for swimming, clear water with low algae levels
Water Quality Grade: B, Good
Very murky, less than -324.8 ft of visibility. Phosphorus level: 14 µg/L. Chlorophyll-a: 3.9 µg/L. Trophic State Index: 43.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | -324.8 ft | F |
| Phosphorus | 14 µg/L | A |
| Chlorophyll-a (Algae) | 3.9 µg/L | A |
| Trophic State Index (TSI) | 43 | Mesotrophic |
Moderate nutrients, good water quality
Invasive Species
Water Quality Trend: ↓ Declining
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -10.747 m/yr | 4 |
| Phosphorus | ↓ Declining | +2.28 µg/L/yr | 2 |
| Chlorophyll-a | ↓ Declining | +0.1 µg/L/yr | 3 |
Location
County Ranking
Ranked #65 of 128 lakes in Cook County
Nearby Lakes in Cook County
More Minnesota Lake Rankings
State Parks Near Little Lake Deep
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 Little Lake Deep. 2 reports on file.
- —Fish Stocking History — SuperiorFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — SuperiorPublic Water Access Sites · MN DNR LakeFinder
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Most recent sample: 2024-09-09
Monitoring stations: 2