Karth Lake
Karth Lake in Ramsey County, Minnesota has a water quality grade of C (Fair). Water clarity: 6.6 ft visibility. Phosphorus: 30 µg/L. Chlorophyll-a (algae): 7.5 µg/L.
- Clarity
- 6.6 ft
- Typical in August
- 78°F
- Type
- Eutrophic
- Trend
- ↓ Declining
- Public access
- No
Next lake in Ramsey County
Karth Lake is a productive, nutrient-rich eutrophic lake in Ramsey County, Minnesota. Water quality is graded C based on 2 sampling years through 2024. Overall water quality is declining over recent sampling years. Limited fish-species data available. No public access — the lake is private or restricted. Compared to the 43 other monitored lakes in Ramsey County, Karth Lake ranks #16 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-10-18. 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)
Murky, only visible to about 6.6 ft. Phosphorus level: 30 µg/L. Chlorophyll-a: 7.5 µg/L. Trophic State Index: 51.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 6.6 ft | Not graded |
| Phosphorus | 30 µg/L | Fair |
| Chlorophyll-a (Algae) | 7.5 µg/L | Fair |
| Trophic State Index (TSI) | 51 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Karth Lake
Compare lakeside cabins, hotels, and vacation rentals near Karth Lake in Ramsey 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 Karth Lake
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Water Temperature
Karth Lake typically sits around 78°F at the surface in August. Summer average is about 77°F. Usually warmest in Jul (about 80°F) and coldest in Oct (about 58°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 39 field readings (2010–2024) via the EPA Water Quality Portal. See the full Karth Lake water temperature breakdown →
Fishing Karth Lake
Water Quality Trend: ↓ Declining
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.112 m/yr | 5 |
EPA Impairment Status
Karth Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN62-0071-00 · Official waterbody report · Matched by proximity (1.96 km)
County Ranking
Ranked #16 of 44 lakes in Ramsey County
Nearby Lakes With Higher Grades
Karth Lake holds Grade C. 2 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
Nearby Lakes in Ramsey County
Frequently asked questions about Karth Lake
What is the water quality grade for Karth Lake?
- Karth Lake in Ramsey County, Minnesota has a water quality grade of C (Fair). Water clarity: 6.6 ft visibility. Phosphorus: 30 µg/L. Chlorophyll-a (algae): 7.5 µg/L.
Is Karth Lake safe to swim in?
- Generally safe for swimming, moderate water quality. Karth Lake has a water quality grade of C (Fair). Algae concentration (chlorophyll-a) is 7.5 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Karth Lake?
- Karth Lake typically sits around 78°F at the surface in August, from 39 EPA Water Quality Portal field readings (2010–2024). That is a typical value for the month, not a live reading.
Explore Karth Lake across LakeGrade
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Fish species and best lakes in Ramsey County
Species activity outlook by water temperature and season
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High nutrients, frequent algae, reduced clarity
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State Parks Near Karth Lake
Other Grade C Lakes in Minnesota
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Where this data comes from
56 measurements from 1 monitoring station, 2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA56 samples · 2024
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Colorimetry
- Analysis of Chlorophyll in Periphyton and Plankton
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