Gem Lake
Gem Lake in Ramsey County, Minnesota has a water quality grade of C (Fair). Water clarity: 6.9 ft visibility. Phosphorus: 36 µg/L. Chlorophyll-a (algae): 11.6 µg/L.
- Clarity
- 6.9 ft
- Typical in August
- 73°F
- Type
- Eutrophic
- Trend
- ↓ Declining
- Public access
- No
Next lake in Ramsey County
Gem Lake is a productive, nutrient-rich eutrophic lake in Ramsey County, Minnesota. Water quality is graded C based on 2 sampling years through 2025. 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. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyModerate
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)
Moderate clarity, visible to about 6.9 ft. Phosphorus level: 36 µg/L. Chlorophyll-a: 11.6 µg/L. Trophic State Index: 53.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 6.9 ft | Not graded |
| Phosphorus | 36 µg/L | Fair |
| Chlorophyll-a (Algae) | 11.6 µg/L | Fair |
| Trophic State Index (TSI) | 53 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Gem Lake
Compare lakeside cabins, hotels, and vacation rentals near Gem 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 Gem Lake
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Water Temperature
Gem Lake typically sits around 73°F at the surface in August. 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.
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 →
Fishing Gem Lake
Water Quality Trend: ↓ Declining
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.004 m/yr | 3 |
| Phosphorus | ↓ Declining | +6.61 µg/L/yr | 6 |
| Chlorophyll-a | ↓ Declining | +6.17 µg/L/yr | 6 |
EPA Impairment Status
Gem 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 MN62-0126-00 · Official waterbody report · Matched by proximity (1.62 km)
County Ranking
Ranked #9 of 44 lakes in Ramsey County
Nearby Lakes With Higher Grades
Gem 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.
See full comparison →Nearby Lakes in Ramsey County
Frequently asked questions about Gem Lake
What is the water quality grade for Gem Lake?
- Gem Lake in Ramsey County, Minnesota has a water quality grade of C (Fair). Water clarity: 6.9 ft visibility. Phosphorus: 36 µg/L. Chlorophyll-a (algae): 11.6 µg/L.
Is Gem Lake safe to swim in?
- Generally safe for swimming, moderate water quality. Gem Lake has a water quality grade of C (Fair). Algae concentration (chlorophyll-a) is 11.6 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Gem Lake?
- Gem Lake typically sits around 73°F at the surface in August, from 52 EPA Water Quality Portal field readings (2010–2022). That is a typical value for the month, not a live reading.
Explore Gem 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 Gem Lake
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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)
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