Little Lake Deep
Cook County, MinnesotaView mapDirections
Minnesota PCA publishes the water-quality measurements for Little Lake Deep. Here is what has been measured.
- Mesotrophic
- 6 aquatic invasives
- Public access
- Limited data
Little Lake Deep in Cook County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 4.9 ft visibility. Phosphorus: 14 µg/L. Chlorophyll-a (algae): 3.9 µg/L.
Little Lake Deep is a mesotrophic lake in Cook County, Minnesota. 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. Methodology: how these readings are compared.
Swimming conditions
Readings onlyLimited data
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Little Lake Deep is safe to swim in today is a call for the Minnesota Pollution Control Agency and the Minnesota DNR and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Little Lake Deep
These are the measurements Minnesota PCA publishes for Little Lake Deep, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Murky, only visible to about 4.9 ft. Phosphorus 14 µg/L. Chlorophyll-a 3.9 µg/L. TSI 47.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 4.9ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 14µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 3.9µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 47 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Little Lake Deep
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Little Lake Deep typically sits around 63°F at the surface in September. 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.
Column height runs from this lake’s coldest month (60°F) to its warmest (69°F).
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 →
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
Stays via Stay22
Stays near Little Lake Deep
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Top-rated places to stay near Little Lake Deep
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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.
Water Quality Trend: Worsening
Based on 5 years of monitoring (2020–2025).
Water clarity
Worsening4 years
Phosphorus
Worsening+2.28 µg/L/yr2 years
Chlorophyll-a
Worsening+0.1 µg/L/yr3 years
Nearby Lakes in Cook County
Frequently asked questions about Little Lake Deep
Where is Little Lake Deep?
- Little Lake Deep is a lake in Cook County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Little Lake Deep?
- Little Lake Deep in Cook County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. 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?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Little Lake Deep?
- Little Lake Deep typically sits around 63°F at the surface in September, from 31 EPA Water Quality Portal field readings (2010–2024). That is a typical value for the month, not a live reading.
Can I fish at Little Lake Deep?
- Public access to Little Lake Deep is listed as yes on the lake record. Seasons, size and bag limits, and whether you need a license are set by Minnesota's fish and wildlife agency, so check its current regulations before you go.
Explore Little Lake Deep across LakeQuality
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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)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.