Swamp Lake Deep
Swamp Lake Deep in Cook County, Minnesota has a water quality grade of C (Fair). Water clarity: 1.7 ft visibility. Phosphorus: 27 µg/L. Chlorophyll-a (algae): 9.2 µg/L.
- Clarity
- 1.7 ft
- Typical in August
- 70°F
- Mean depth
- ~11 ft est.
- Type
- Eutrophic
- Trend
- ↓ Declining
Next lake in Cook County
Swamp Lake Deep is a productive, nutrient-rich eutrophic lake in Cook County, Minnesota with an estimated average depth of about 11 feet. Water quality is graded C based on 2 sampling years through 2024. Overall water quality is declining over recent sampling years. Compared to the 43 other monitored lakes in Cook County, Swamp Lake Deep ranks #43 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-09-10. 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.
Generally safe for swimming, moderate water quality
Water Quality Grade: C (Fair)
Very murky, less than 1.7 ft of visibility. Phosphorus level: 27 µg/L. Chlorophyll-a: 9.2 µg/L. Trophic State Index: 58.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.7 ft | Not graded |
| Phosphorus | 27 µg/L | Fair |
| Chlorophyll-a (Algae) | 9.2 µg/L | Fair |
| Trophic State Index (TSI) | 58 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Swamp Lake Deep
Compare lakeside cabins, hotels, and vacation rentals near Swamp 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.
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Water Temperature
Swamp Lake Deep typically sits around 70°F at the surface in August. Summer average is about 67°F. Usually warmest in Aug (about 70°F) and coldest in Oct (about 49°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 167 field readings (2010–2024) via the EPA Water Quality Portal. See the full Swamp Lake Deep water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Average Depth | ~11 ft est. |
Depth marked “est.” is a modeled estimate from HydroLAKES, not a measured survey. Minnesota has not published bathymetry for Swamp Lake Deep.
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Fishing Swamp Lake Deep
Water Quality Trend: ↓ Declining
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -1.375 m/yr | 2 |
| Phosphorus | ↓ Declining | +2.03 µg/L/yr | 3 |
| Chlorophyll-a | → Stable | +0.1 µg/L/yr | 3 |
County Ranking
Ranked #43 of 44 lakes in Cook County
Nearby Lakes in Cook County
Frequently asked questions about Swamp Lake Deep
What is the water quality grade for Swamp Lake Deep?
- Swamp Lake Deep in Cook County, Minnesota has a water quality grade of C (Fair). Water clarity: 1.7 ft visibility. Phosphorus: 27 µg/L. Chlorophyll-a (algae): 9.2 µg/L.
Is Swamp Lake Deep safe to swim in?
- Generally safe for swimming, moderate water quality. Swamp Lake Deep has a water quality grade of C (Fair). Algae concentration (chlorophyll-a) is 9.2 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Swamp Lake Deep?
- Swamp Lake Deep typically sits around 70°F at the surface in August, from 167 EPA Water Quality Portal field readings (2010–2024). That is a typical value for the month, not a live reading.
How deep is Swamp Lake Deep?
- No published bathymetric survey covers Swamp Lake Deep, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 11 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
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Where this data comes from
106 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_WQX62 samples · 2022–2024 - 21GPBCH - Grand Portage Beaches (Tribal)
21GPBCH44 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.
Other records on this page
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder