Long Lake
Iosco County, Michigan487 acresView mapDirections
EGLE publishes the water-quality measurements for Long Lake. Here is what has been measured.
- Oligotrophic
- 62 ft max depth
- Limited data
Long Lake in Iosco County, Michigan has water-quality measurements published by EGLE, shown here as reported. Water clarity: 14 ft visibility. Phosphorus: 14 µg/L. Chlorophyll-a (algae): 1 µg/L. Maximum depth: 62 ft. Surface area: 486.9 acres.
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 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. Methodology: how these readings are compared.
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 conditions
Readings onlyLimited data
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Long Lake is safe to swim in today is a call for the Michigan Department of Environment, Great Lakes, and Energy (EGLE) and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Long Lake
These are the measurements EGLE publishes for Long Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Good clarity, visible to about 14 ft. Phosphorus 14 µg/L. Chlorophyll-a 1 µg/L. TSI 37.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 14ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 14µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 1µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 37 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Long Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
62 ft
Surface area
487 acres
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Fishing Long Lake
Water Quality Trend: Stable
Based on 7 years of monitoring (2016–2023).
Water clarity
Improving5 years
Phosphorus
Stable+0.05 µg/L/yr5 years
Chlorophyll-a
Worsening+0.18 µg/L/yr4 years
Nearby Lakes in Iosco County
Frequently asked questions about Long Lake
Where is Long Lake?
- Long Lake is a lake in Iosco County, Michigan. Its water-quality measurements are published by EGLE and shown on this page as reported.
What is the water quality of Long Lake?
- Long Lake in Iosco County, Michigan has water-quality measurements published by EGLE, shown here as reported. 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?
- Nutrient and algae readings are 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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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)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.