Long Lake
Iosco County, Michigan487 acresView mapDirections
Clarity, phosphorus, and algae all sit in the cleanest band for this region.
- Oligotrophic
- #3 of 5 in the county
- 62 ft max depth
- Limited data
Long Lake in Iosco County, Michigan has a water quality grade of A (Excellent). Water clarity: 14 ft visibility. Phosphorus: 14 µg/L. Chlorophyll-a (algae): 1 µg/L. Maximum depth: 62 ft. Surface area: 486.9 acres.
- Clarity
- 14 ft
- Max depth
- 62 ft
- Area
- 487 acres
- Type
- Oligotrophic
- Phosphorus
- 14 µg/L
- Chlorophyll-a
- 1 µg/L
- Trend
- → Stable
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Watch Long Lake’s letter
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Free interactive depth-contour map of Long Lake, reaching a maximum surveyed depth of 62 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Michigan DNR.
Long Lake is a 487-acre cold, clear oligotrophic lake in Iosco County, Michigan with a maximum depth of 62 feet. Water quality is graded A based on 2 sampling years through 2023. Water clarity is improving over recent sampling years. Compared to the 4 other monitored lakes in Iosco County, Long Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, EGLE, last sampled 2023-09-03. Grade methodology: LakeQuality methodology.
What Long Lake is good for
From access and monitoring records, not editorial picks.
- Clear water14 ft of visibility
- Deep water62 ft surveyed max depth
Swimming Safety
Grade onlyLimited data
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. Check local advisories before you swim.
Water Quality Grade: A (Excellent)
Good clarity, visible to about 14 ft. Phosphorus 14 µg/L. Chlorophyll-a 1 µg/L. TSI 37. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 14 ft | Not graded |
| Phosphorus | 14 µg/L | Good |
| Chlorophyll-a (Algae) | 1 µg/L | Good |
| Trophic State Index (TSI) | 37 | Oligotrophic |
Low nutrients, clear water. The letter is not a swimming clearance.
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 62 ft |
| Surface Area | 487 acres |
Fishing Long Lake
Water Quality Trend: → Stable
Based on 7 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.741 m/yr | 5 |
| Phosphorus | → Stable | +0.05 µg/L/yr | 5 |
| Chlorophyll-a | ↓ Declining | +0.18 µg/L/yr | 4 |
County Ranking
Ranked #3 of 5 lakes in Iosco County
Nearby Lakes in Iosco County
Frequently asked questions about Long Lake
Where is Long Lake?
- Long Lake is a lake in Iosco County, Michigan. LakeQuality grades it A for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Long Lake?
- Long Lake in Iosco County, Michigan has a water quality grade of A (Excellent). Water clarity: 14 ft visibility. Phosphorus: 14 µg/L. Chlorophyll-a (algae): 1 µg/L. Maximum depth: 62 ft. Surface area: 486.9 acres.
Is Long Lake safe to swim in?
- The A is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
How deep is Long Lake?
- Long Lake has a maximum depth of 62 feet. The lake covers 486.9 acres.
Explore Long Lake across LakeQuality
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Low nutrients, clear water. The letter is not a swimming clearance.
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Where this data comes from
102 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_MICORPS102 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.