Little Lake Deep
Little Lake Deep in Cook County, Minnesota has a water quality grade of A (Excellent). Water clarity: 4.9 ft visibility. Phosphorus: 14 µg/L. Chlorophyll-a (algae): 3.9 µg/L.
- Clarity
- 4.9 ft
- Typical in July
- 69°F
- Type
- Mesotrophic
- Trend
- ↓ Declining
- Public access
- Yes
Next lake in Cook County
Little Lake Deep is a mesotrophic lake in Cook County, Minnesota. Water quality is graded A based on 2 sampling years through 2024. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available. Compared to the 43 other monitored lakes in Cook County, Little Lake Deep ranks #33 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-09-09. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLimited data
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A (Excellent)
Murky, only visible to about 4.9 ft. Phosphorus level: 14 µg/L. Chlorophyll-a: 3.9 µg/L. Trophic State Index: 47.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 4.9 ft | Not graded |
| Phosphorus | 14 µg/L | Good |
| Chlorophyll-a (Algae) | 3.9 µg/L | Good |
| Trophic State Index (TSI) | 47 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Little Lake Deep
Compare lakeside cabins, hotels, and vacation rentals near Little Lake Deep in Cook County, Minnesota — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near Little Lake Deep
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Water Temperature
Little Lake Deep typically sits around 69°F at the surface in July. Summer average is about 69°F. Usually warmest in Jul (about 69°F) and coldest in May (about 60°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 31 field readings (2010–2024) via the EPA Water Quality Portal. See the full Little Lake Deep water temperature breakdown →
Fishing Little Lake Deep
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
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.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fish Stocking History — SuperiorFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — SuperiorPublic Water Access Sites · MN DNR LakeFinder
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 |
County Ranking
Ranked #33 of 44 lakes in Cook County
Nearby Lakes in Cook County
Frequently asked questions about Little Lake Deep
What is the water quality grade for Little Lake Deep?
- Little Lake Deep in Cook County, Minnesota has a water quality grade of A (Excellent). Water clarity: 4.9 ft visibility. Phosphorus: 14 µg/L. Chlorophyll-a (algae): 3.9 µg/L.
Is Little Lake Deep safe to swim in?
- Excellent for swimming, crystal clear water with minimal algae. Little Lake Deep has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 3.9 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Little Lake Deep?
- Little Lake Deep typically sits around 69°F at the surface in July, from 31 EPA Water Quality Portal field readings (2010–2024). That is a typical value for the month, not a live reading.
Explore Little Lake Deep across LakeGrade
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Species activity outlook by water temperature and season
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Moderate nutrients, good water quality
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State Parks Near Little Lake Deep
Other Grade A Lakes in Minnesota
Mesotrophic Lakes in Minnesota
Where this data comes from
31 measurements from 2 monitoring stations, 2020–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Grand Portage Reservation
GPC5_WQX18 samples · 2022–2024 - 21GPBCH - Grand Portage Beaches (Tribal)
21GPBCH13 samples · 2020
Analytical methods
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- Turbidity by Nephelometry
Monitoring station identifiers (2)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.