St Clair Lake
St Clair Lake in Becker County, Minnesota has a water quality grade of D (Nutrient-rich). Water clarity: 4 ft visibility. Phosphorus: 50 µg/L. Chlorophyll-a (algae): 14.3 µg/L. Surface area: 45 acres.
- Clarity
- 4 ft
- Typical in August
- 72°F
- Mean depth
- ~9 ft est.
- Area
- 45 acres
- Type
- Eutrophic
- Trend
- ↑ Improving
- Public access
- No
Grade D measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near St Clair Lake →
Next lake in Becker County
St Clair Lake is a 45-acre productive, nutrient-rich eutrophic lake in Becker County, Minnesota with an estimated average depth of about 9 feet. Water quality is graded D based on 2 sampling years through 2025. Overall water quality is improving over recent sampling years. Limited fish-species data available. No public access — the lake is private or restricted. Compared to the 83 other monitored lakes in Becker County, St Clair Lake ranks #74 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-16. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyElevated nutrients
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.
Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum
Water Quality Grade: D (Nutrient-rich)
Murky, only visible to about 4 ft. Phosphorus level: 50 µg/L. Chlorophyll-a: 14.3 µg/L. Trophic State Index: 58.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 4 ft | Not graded |
| Phosphorus | 50 µg/L | Poor |
| Chlorophyll-a (Algae) | 14.3 µg/L | Fair |
| Trophic State Index (TSI) | 58 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near St Clair Lake
Compare lakeside cabins, hotels, and vacation rentals near St Clair Lake in Becker 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. The water-quality grade measures nutrients and algae, not lodging — cabins and rentals around St Clair Lake are listed below.
Top-rated places to stay near St Clair Lake
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Planning a whole trip? See where to stay at Minnesota’s top lakes →
Water Temperature
St Clair Lake typically sits around 72°F at the surface in August. Summer average is about 72°F. Usually warmest in Jul (about 75°F) and coldest in Sep (about 67°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 223 field readings (2016–2025) via the EPA Water Quality Portal. See the full St Clair Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Average Depth | ~9 ft est. |
| Surface Area | 45 acres |
| Public Access | No |
Depth marked “est.” is a modeled estimate from HydroLAKES, not a measured survey. Minnesota has not published bathymetry for St Clair Lake.
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 St Clair Lake
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
Water Quality Trend: ↑ Improving
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.042 m/yr | 6 |
| Phosphorus | ↑ Improving | -4.14 µg/L/yr | 6 |
| Chlorophyll-a | ↑ Improving | -0.86 µg/L/yr | 6 |
Reservoir Info (USACE NID)
St Clair Lake is a man-made reservoir impounded by the Long Lake (completed 1936), built primarily for recreation on the Pelican River-TR; gravity-type dam, 9 ft tall.
- Surface area
- 45 ac
- Normal storage
- 4,365 ac-ft
- Max storage
- 5,335 ac-ft
- Drainage area
- 3.2 sq mi
- Hazard class
- Low
- Owner
- MNDNR
Source: USACE National Inventory of Dams, NID ID MN00882 · Operator website · Matched by proximity (0.96 km)
EPA Impairment Status
St Clair 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 MN03-0382-00 · Official waterbody report
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of St Clair Lake under Clean Water Act (NPDES) discharge permits, including 1 classified by the EPA as major discharger. 1 facility has a reported Clean Water Act violation in the past three years.
- Detroit Lakes Water Reclamation FacilityDetroit Lakes · 1 mi away · NPDES MN0020192MajorRecent violation
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
County Ranking
Ranked #74 of 84 lakes in Becker County
Nearby Lakes With Higher Grades
St Clair Lake holds Grade D. 3 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 Becker County
Frequently asked questions about St Clair Lake
What is the water quality grade for St Clair Lake?
- St Clair Lake in Becker County, Minnesota has a water quality grade of D (Nutrient-rich). Water clarity: 4 ft visibility. Phosphorus: 50 µg/L. Chlorophyll-a (algae): 14.3 µg/L. Surface area: 45 acres.
Is St Clair Lake safe to swim in?
- Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum. St Clair Lake has a water quality grade of D (Nutrient-rich). Algae concentration (chlorophyll-a) is 14.3 µg/L. Always check local health department advisories before swimming.
What is the water temperature of St Clair Lake?
- St Clair Lake typically sits around 72°F at the surface in August, from 223 EPA Water Quality Portal field readings (2016–2025). That is a typical value for the month, not a live reading.
How deep is St Clair Lake?
- No published bathymetric survey covers St Clair Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 9 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate. The lake covers 45 acres.
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Where this data comes from
136 measurements from 2 monitoring stations, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA136 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 (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
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder