Gull Lake
Gull Lake in Cook County, Minnesota has a water quality grade of A (Excellent). Water clarity: 15.5 ft visibility. Phosphorus: 8.5 µg/L. Chlorophyll-a (algae): 2.5 µg/L.
- Clarity
- 15.5 ft
- Type
- Oligotrophic
- Trend
- ↓ Declining
- Public access
- Yes
Next lake in Cook County
Gull Lake is a cold, clear oligotrophic lake in Cook County, Minnesota. Water quality is graded A based on 2 sampling years through 2025. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 3 public boat landings. Compared to the 43 other monitored lakes in Cook County, Gull Lake ranks #8 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-08-05. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLow algae
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)
Crystal clear, you can see 15.5 ft down. Phosphorus level: 8.5 µg/L. Chlorophyll-a: 2.5 µg/L. Trophic State Index: 37.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 15.5 ft | Not graded |
| Phosphorus | 8.5 µg/L | Good |
| Chlorophyll-a (Algae) | 2.5 µg/L | Good |
| Trophic State Index (TSI) | 37 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Gull Lake
Compare lakeside cabins, hotels, and vacation rentals near Gull Lake 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.
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Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Gull LakePublic
- Sea Gull Lake (North)Public
- Saganaga LakePublic
Fishing Gull Lake
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Gull Lake. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Public Water Access Sites — Gull (Main Basin)Public Water Access Sites · MN DNR LakeFinder
Water Quality Trend: ↓ Declining
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.032 m/yr | 6 |
| Phosphorus | → Stable | +0.2 µg/L/yr | 5 |
| Chlorophyll-a | ↓ Declining | +0.37 µg/L/yr | 5 |
EPA Impairment Status
Gull Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit MN16-0632-01 · Official waterbody report · Matched by proximity (0.64 km)
County Ranking
Ranked #8 of 44 lakes in Cook County
Nearby Lakes in Cook County
Frequently asked questions about Gull Lake
What is the water quality grade for Gull Lake?
- Gull Lake in Cook County, Minnesota has a water quality grade of A (Excellent). Water clarity: 15.5 ft visibility. Phosphorus: 8.5 µg/L. Chlorophyll-a (algae): 2.5 µg/L.
Is Gull Lake safe to swim in?
- Excellent for swimming, crystal clear water with minimal algae. Gull Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 2.5 µg/L. Always check local health department advisories before swimming.
How deep is Gull Lake?
- The available depth estimate for Gull Lake is shallower than its measured water clarity, which cannot be right, so no depth is shown.
Are there boat ramps on Gull Lake?
- Gull Lake has 3 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Gull Lake, Sea Gull Lake (North), Saganaga Lake. Public access is listed as yes.
Explore Gull Lake across LakeGrade
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Where this data comes from
34 measurements from 1 monitoring station, 2021–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA34 samples · 2021–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (1)
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.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Named boat-access points from the USGS National Boat Ramps inventory