Horsehead Lake
Mecosta County, MichiganView mapDirections
Clarity, phosphorus, and algae all sit in the cleanest band for this region.
- Mesotrophic
- Impaired · Mercury
- #4 of 6 in the county
- Public access
Horsehead Lake in Mecosta County, Michigan has a water quality grade of A (Excellent). Water clarity: 9 ft visibility. Phosphorus: 14 µg/L. Chlorophyll-a (algae): 2.5 µg/L.
- Clarity
- 9 ft
- Typical in September
- 61°F
- Type
- Mesotrophic
- Phosphorus
- 14 µg/L
- Chlorophyll-a
- 2.5 µg/L
- Trend
- ↑ Improving
- Public access
- Yes
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Watch Horsehead Lake’s letter
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Horsehead Lake is a mesotrophic lake in Mecosta County, Michigan. Water quality is graded A based on 2 sampling years through 2023. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available. Compared to the 5 other monitored lakes in Mecosta County, Horsehead Lake ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, EGLE, last sampled 2023-09-14. Grade methodology: LakeQuality methodology.
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.
The A is nutrients and algae, not a swimming clearance. Horsehead Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, oxygen depletion (low DO). Check local advisories before you swim.
Water Quality Grade: A (Excellent)
Moderate clarity, visible to about 9 ft. Phosphorus 14 µg/L. Chlorophyll-a 2.5 µg/L. TSI 42. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 9 ft | Not graded |
| Phosphorus | 14 µg/L | Good |
| Chlorophyll-a (Algae) | 2.5 µg/L | Good |
| Trophic State Index (TSI) | 42 | Mesotrophic |
Moderate nutrients, good water quality
Water Temperature
Horsehead Lake typically sits around 61°F at the surface in September. Summer average is about 60°F. Usually warmest in Aug (about 62°F) and coldest in May (about 56°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 439 field readings (2021–2023) via the EPA Water Quality Portal. See the full Horsehead Lake water temperature breakdown →
Fishing Horsehead Lake
Water Quality Trend: ↑ Improving
Based on 7 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.324 m/yr | 7 |
| Phosphorus | → Stable | -0.04 µg/L/yr | 7 |
| Chlorophyll-a | ↑ Improving | -0.09 µg/L/yr | 7 |
EPA Impairment Status
Horsehead Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MI040601020801-03 · Official waterbody report · Matched by proximity (0.49 km)
County Ranking
Ranked #4 of 6 lakes in Mecosta County
Nearby Lakes in Mecosta County
Frequently asked questions about Horsehead Lake
Where is Horsehead Lake?
- Horsehead Lake is a lake in Mecosta County, Michigan. LakeQuality grades it A for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Horsehead Lake?
- Horsehead Lake in Mecosta County, Michigan has a water quality grade of A (Excellent). Water clarity: 9 ft visibility. Phosphorus: 14 µg/L. Chlorophyll-a (algae): 2.5 µg/L.
Is Horsehead Lake safe to swim in?
- The A is nutrients and algae, not a swimming clearance. Horsehead Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, oxygen depletion (low DO). Check local advisories before you swim.
What is the water temperature of Horsehead Lake?
- Horsehead Lake typically sits around 61°F at the surface in September, from 439 EPA Water Quality Portal field readings (2021–2023). That is a typical value for the month, not a live reading.
Explore Horsehead Lake across LakeQuality
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Where this data comes from
166 measurements from 1 monitoring station, 2016–2023. Retrieved from the EPA Water Quality Portal on 2026-08-26.
Collected and reported by
- Michigan EGLE - MiCorps
21MICH_MICORPS166 samples · 2016–2023
Analytical methods
- Phosphorus by Colorimetry
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
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