Long Lake is a mesotrophic lake in Cass County, Michigan. Water quality is graded B based on 1 sampling years through 2022. Overall water quality is improving over recent sampling years. The lake supports 25 documented fish species including Blacknose shiner, Blackside darter, and Blackstripe topminnow. Public access is available. Compared to the 22 other monitored lakes in Cass County, Long Lake ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, Michigan DNR, last sampled 2022-09-16. Grade methodology: LakeGrade methodology.
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Swimming Safety
Good for swimming, clear water with low algae levels
Water Quality Grade: B, Good
Good clarity, visible to about 10.5 ft. Trophic State Index: 43.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 10.5 ft | B |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 43 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Long Lake
Compare lakeside cabins, hotels, and vacation rentals near Long Lake in Cass County, Michigan — 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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Fish Species
Click a species to see every graded lake where it is documented.
Fishing Long Lake
Water Quality Trend: ↑ Improving
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +1.57 m/yr | 4 |
| Chlorophyll-a | ↑ Improving | -0.35 µg/L/yr | 3 |
Location & Depth Map
Free interactive depth-contour map of Long Lake, reaching a maximum surveyed depth of 42 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Michigan DNR.
County Ranking
Ranked #4 of 23 lakes in Cass County
Nearby Lakes in Cass County
Explore Long Lake across LakeGrade
Fish species and top-graded lakes across Michigan
Fish species and best lakes in Cass County
Species activity outlook by water temperature and season
Where to stay at Michigan's top lakes, each with its grade
Moderate nutrients, good water quality
Michigan's cleanest and most-polluted lakes, ranked
More Michigan Lake Rankings
Other Grade B Lakes in Michigan
Van Buren County · Clarity: 11.5 ft
St. Joseph County · Clarity: 10.5 ft
Kalamazoo County · Clarity: 9.5 ft
Kalamazoo County · Clarity: 8 ft
Kalamazoo County · Clarity: 9.5 ft
Allegan County · Clarity: 14 ft
Mesotrophic Lakes in Michigan
More records, surveys & data sources
EPA Impairment Status
Long 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 MI040500011303-06 · Official waterbody report
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Long Lake under Clean Water Act (NPDES) discharge permits.
- Porter Twp WwtpWhite Pigeon · 3.6 mi away · NPDES MI0057602
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.
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Most recent sample: 2022-09-16
Monitoring stations: 1