Horseshoe Lake
Horseshoe Lake in Isanti County, Minnesota has a water quality grade of A (Excellent). Water clarity: 3.5 ft visibility. Phosphorus: 13 µg/L. Chlorophyll-a (algae): 2.7 µg/L.
- Clarity
- 3.5 ft
- Typical in August
- 75°F
- Mean depth
- ~9 ft est.
- Type
- Mesotrophic
- Trend
- ↓ Declining
- Public access
- No
Next lake in Isanti County
Horseshoe Lake is a mesotrophic lake in Isanti County, Minnesota with an estimated average depth of about 9 feet. Water quality is graded A 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 16 other monitored lakes in Isanti County, Horseshoe Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-29. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLow algae
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.
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A (Excellent)
Murky, only visible to about 3.5 ft. Phosphorus level: 13 µg/L. Chlorophyll-a: 2.7 µg/L. Trophic State Index: 47.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.5 ft | Not graded |
| Phosphorus | 13 µg/L | Good |
| Chlorophyll-a (Algae) | 2.7 µg/L | Good |
| Trophic State Index (TSI) | 47 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Horseshoe Lake
Compare lakeside cabins, hotels, and vacation rentals near Horseshoe Lake in Isanti 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.
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Water Temperature
Horseshoe Lake typically sits around 75°F at the surface in August. Summer average is about 76°F. Usually warmest in Jul (about 77°F) and coldest in May (about 63°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 38 field readings (2017–2025) via the EPA Water Quality Portal. See the full Horseshoe Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Average Depth | ~9 ft est. |
| Public Access | No |
Depth marked “est.” is a modeled estimate from HydroLAKES, not a measured survey. Minnesota has not published bathymetry for Horseshoe 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 Horseshoe Lake
Water Quality Trend: ↓ Declining
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.496 m/yr | 6 |
| Phosphorus | ↓ Declining | +2.34 µg/L/yr | 6 |
| Chlorophyll-a | ↓ Declining | +1.09 µg/L/yr | 6 |
EPA Impairment Status
Horseshoe Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit MN30-0004-00 · Official waterbody report · Matched by proximity (1.73 km)
County Ranking
Ranked #1 of 17 lakes in Isanti County
Nearby Lakes in Isanti County
Frequently asked questions about Horseshoe Lake
What is the water quality grade for Horseshoe Lake?
- Horseshoe Lake in Isanti County, Minnesota has a water quality grade of A (Excellent). Water clarity: 3.5 ft visibility. Phosphorus: 13 µg/L. Chlorophyll-a (algae): 2.7 µg/L.
Is Horseshoe Lake safe to swim in?
- Excellent for swimming, crystal clear water with minimal algae. Horseshoe Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 2.7 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Horseshoe Lake?
- Horseshoe Lake typically sits around 75°F at the surface in August, from 38 EPA Water Quality Portal field readings (2017–2025). That is a typical value for the month, not a live reading.
How deep is Horseshoe Lake?
- No published bathymetric survey covers Horseshoe 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.
Explore Horseshoe Lake across LakeGrade
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Where this data comes from
90 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
MNPCA90 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by 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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder