Posey Lake is a 150-acre productive, nutrient-rich eutrophic lake in Lenawee County, Michigan. Water quality is graded D based on 1 sampling years through 2022. Overall water quality is improving over recent sampling years. The lake supports 7 documented fish species including Bluegill, Common carp, and Golden redhorse. Compared to the 7 other monitored lakes in Lenawee County, Posey Lake ranks #8 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
Swimming not recommended, poor water quality with high algae risk
Water Quality Grade: D, Poor
Murky, only visible to about 4.5 ft. Trophic State Index: 55.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 4.5 ft | D |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 55 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 150 acres |
Where to stay near Posey Lake
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Fish Species
Click a species to see every graded lake where it is documented.
Fishing Posey Lake
Water Quality Trend: ↑ Improving
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +1.295 m/yr | 3 |
| Chlorophyll-a | ↑ Improving | -3.7 µg/L/yr | 2 |
Location
County Ranking
Ranked #8 of 8 lakes in Lenawee County
Cleaner Lakes Within 30 Miles
Posey Lake holds Grade D. 3 nearby lakes hold higher grades.
Nearby Lakes in Lenawee County
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High nutrients, frequent algae, reduced clarity
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More records, surveys & data sources
Reservoir Info (USACE NID)
Posey Lake is a man-made reservoir impounded by the Posey Lake Level Control Structure (completed 1955), built primarily for recreation on the Posey Lake Drain; gravity-type dam, 7 ft tall and 15 ft long.
- Surface area
- 150 ac
- Normal storage
- 190 ac-ft
- Max storage
- 715 ac-ft
- Drainage area
- 0 sq mi
- Hazard class
- Low
- Owner
- Lenawee County Drain Commissioner
Source: USACE National Inventory of Dams, NID ID MI02265 · Operator website
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
5 EPA-permitted facilities operate within about 5 miles of Posey Lake under Clean Water Act (NPDES) discharge permits. 3 facilities have a reported Clean Water Act violation in the past three years.
- Hartland Farms-CafoClayton · 1.3 mi away · NPDES MI0057536Recent violation
- Bakerlads Farm-CafoClayton · 3.8 mi away · NPDES MI0059009Recent violation
- Hudson WwtpHudson · 4.1 mi away · NPDES MI0021377Recent violation
- Hartland Farms, IncClayton · 1.3 mi away · NPDES MIA000002
- Bakerlads FarmsClayton · 3.9 mi away · NPDES MIA000014
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
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