Saint Mary'S River Shore Lake is a mesotrophic lake in Chippewa County, Michigan. Water quality is graded A based on 2 sampling years through 2022. Water clarity is improving over recent sampling years. Compared to the 17 other monitored lakes in Chippewa County, Saint Mary'S River Shore Lake ranks #8 for water quality.
Source: EPA Water Quality Portal sampling records, Michigan DNR, last sampled 2022-10-03. Grade methodology: LakeGrade methodology.
Watch Saint Mary'S River Shore Lake water quality
Subscribe for LakeQuality updates by email. No spam, unsubscribe anytime.
Swimming Safety
Based on E. coli testing, Saint Mary'S River Shore Lake rarely exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 2.7% of 336 samples across 8 seasons.
This is a historical summary of past testing, not a current condition — bacteria levels change quickly, especially after rain. Always check Michigan’s current beach and health-department advisories before swimming.
Water Quality Grade: A, Excellent
No clarity data. Phosphorus level: 22.5 µg/L. Chlorophyll-a: 4.3 µg/L. Trophic State Index: 47.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No data | |
| Phosphorus | 22.5 µg/L | B |
| Chlorophyll-a (Algae) | 4.3 µg/L | A |
| Trophic State Index (TSI) | 47 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Saint Mary'S River Shore Lake
Compare lakeside cabins, hotels, and vacation rentals near Saint Mary'S River Shore Lake in Chippewa County, Michigan — 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 Saint Mary'S River Shore Lake
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a trip to Saint Mary'S River Shore Lake?
Get lake water-quality report cards plus the best cabin & lodging deals near Saint Mary'S River Shore Lake — straight to your inbox. No spam, unsubscribe anytime.
Planning a whole trip? See where to stay at Michigan’s top lakes →
Fishing Saint Mary'S River Shore Lake
Water Quality Trend: → Stable
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.234 m/yr | 4 |
| Phosphorus | → Stable | +0.24 µg/L/yr | 5 |
| Chlorophyll-a | ↓ Declining | +20.7 µg/L/yr | 3 |
Water Temperature
Saint Mary'S River Shore Lake averages about 60°F at the surface in summer, usually warmest in Aug (about 65°F) and coldest in May (about 47°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 673 field readings (2010–2022) via the EPA Water Quality Portal. See the full Saint Mary'S River Shore Lake water temperature breakdown →
Location
County Ranking
Ranked #8 of 18 lakes in Chippewa County
Nearby Lakes in Chippewa County
Explore Saint Mary'S River Shore Lake across LakeGrade
Fish species and top-graded lakes across Michigan
Fish species and best lakes in Chippewa County
Species activity outlook by water temperature and season
Top lakes and where to stay in the Upper Peninsula area
Where to stay at Michigan's top lakes, each with its grade
Moderate nutrients, good water quality
Michigan's cleanest and most-polluted lakes, ranked
More Michigan Lake Rankings
Other Grade A Lakes in Michigan
Mesotrophic Lakes in Michigan
More records, surveys & data sources
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Data Sources
Water quality data from the EPA Water Quality Portal
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Most recent sample: 2022-10-03
Monitoring stations: 1