Gem Lake
Ramsey County, MinnesotaView mapDirections
Minnesota PCA publishes the water-quality measurements for Gem Lake. Here is what has been measured.
- Eutrophic
Gem Lake in Ramsey County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 6.9 ft visibility. Phosphorus: 36 µg/L. Chlorophyll-a (algae): 11.6 µg/L.
Gem Lake is a productive, nutrient-rich eutrophic lake in Ramsey County, Minnesota. 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, Gem Lake ranks #9 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-24. Methodology: how these readings are compared.
If you are planning to stay, you can search lake houses and cabins around Gem Lake on Vrbo, or look for a hotel room near the lake on Booking.com or Expedia.
Swimming conditions
Readings onlyModerate algae
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 Gem Lake 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 Gem Lake
These are the measurements Minnesota PCA publishes for Gem Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Moderate clarity, visible to about 6.9 ft. Phosphorus 36 µg/L. Chlorophyll-a 11.6 µg/L. TSI 53.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 6.9ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 36µg/L | Fair GoodFairPoor |
| Chlorophyll-a (algae) | 11.6µg/L | Fair GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 53 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Gem Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Gem Lake typically sits around 68°F at the surface in September. Summer average is about 72°F. Usually warmest in Jul (about 76°F) and coldest in May (about 57°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (57°F) to its warmest (76°F).
Typical surface water temperature by month, from 52 field readings (2010–2022) via the EPA Water Quality Portal. See the full Gem Lake water temperature breakdown →
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Stays near Gem Lake
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Fishing Gem Lake
Water Quality Trend: Worsening
Based on 6 years of monitoring (2020–2025).
Water clarity
Stable3 years
Phosphorus
Worsening+6.61 µg/L/yr6 years
Chlorophyll-a
Worsening+6.17 µg/L/yr6 years
Nearby Lakes in Ramsey County
Frequently asked questions about Gem Lake
Where is Gem Lake?
- Gem Lake is a lake in Ramsey County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Gem Lake?
- Gem Lake in Ramsey County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 6.9 ft visibility. Phosphorus: 36 µg/L. Chlorophyll-a (algae): 11.6 µg/L.
Is Gem Lake 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 Gem Lake?
- Gem Lake typically sits around 68°F at the surface in September, from 52 EPA Water Quality Portal field readings (2010–2022). That is a typical value for the month, not a live reading.
Can I fish at Gem Lake?
- Public access to Gem Lake is listed as no on the lake record, so confirm before you make the trip. 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 Gem Lake across LakeQuality
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Fish species and best lakes in Ramsey County
Species activity outlook by water temperature and season
Where to stay at Minnesota's top lakes, each with its readings
Minnesota's cleanest lakes, ranked on agency measurements
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Other Lakes in Minnesota
Eutrophic Lakes in Minnesota
Where this data comes from
133 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA133 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (1)
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.