Longterm Lake
Allegan County, MichiganView mapDirections
No nutrient or algae sampling on record from EGLE for this lake.
- Impaired · Mercury
- Limited data
Ask about Longterm Lake
Answers come straight from the public measurements and survey records on this page.
Longterm Lake in Allegan County, Michigan has water-quality measurements published by EGLE, shown here as reported.
Stays via Stay22
Stays near Longterm Lake
Compare lakeside cabins, hotels, and vacation rentals near Longterm Lake in Allegan 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.
Top-rated places to stay near Longterm Lake
Prices for Sep 18–20, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Michigan’s top lakes →
Follow Longterm Lake’s readings
Email me when new measurements post for this lake. Updates stay free.
Or email
Longterm Lake is a lake in Allegan County, Michigan. Overall water quality is declining over recent sampling years.
Source: EPA Water Quality Portal sampling records, EGLE, last sampled 2024-10-23. Grade methodology: LakeQuality methodology.
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Longterm Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Whether Longterm 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 Longterm Lake
These are the measurements EGLE publishes for Longterm Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
No clarity data.
| Metric | Value | EPA condition class |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples |
Fishing Longterm Lake
Water Quality Trend: ↓ Declining
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.25 m/yr | 2 |
| Phosphorus | ↓ Declining | +24.79 µg/L/yr | 4 |
EPA Impairment Status
Longterm Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MI040500030803-01 · Official waterbody report · Matched by proximity (1.66 km)
Nearby Lakes in Allegan County
Frequently asked questions about Longterm Lake
Where is Longterm Lake?
- Longterm Lake is a lake in Allegan County, Michigan. Its water-quality measurements are published by EGLE and shown on this page as reported.
What is the water quality of Longterm Lake?
- Longterm Lake in Allegan County, Michigan has water-quality measurements published by EGLE, shown here as reported.
Is Longterm Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Longterm Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Explore Longterm Lake across LakeQuality
Fish species and the cleanest lakes across Michigan
Fish species and best lakes in Allegan County
Species activity outlook by water temperature and season
Where to stay at Michigan's top lakes, each with its readings
Michigan's cleanest lakes, ranked on agency measurements
More lakes in Michigan
Other Lakes in Michigan
Where this data comes from
17,611 measurements from 1 monitoring station, 2019–2024. Retrieved from the EPA Water Quality Portal on 2026-08-26.
Collected and reported by
- Match-e-be-nash-she-wish Band of Pottawatomi Indians of Michigan (Gun Lake)
GNLK01_WQX17,611 samples · 2019–2024
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.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database