Lake Diane South Basin; Amboy Township is a 290-acre productive, nutrient-rich eutrophic lake in Hillsdale County, Michigan. Water quality is graded D based on 2 sampling years through 2021. Limited fish-species data available. Public access is available with 5 public boat landings. Compared to the 6 other monitored lakes in Hillsdale County, Lake Diane South Basin; Amboy Township ranks #5 for water quality.
Source: EPA Water Quality Portal sampling records, Michigan DNR, last sampled 2021-09-26. Grade methodology: LakeGrade methodology.
Watch Lake Diane South Basin; Amboy Township water quality
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Swimming Safety
Swimming not recommended, poor water quality with high algae risk
Water Quality Grade: D, Poor
Very murky, less than 2.5 ft of visibility. Chlorophyll-a: 29 µg/L. Trophic State Index: 64.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.5 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 29 µg/L | D |
| Trophic State Index (TSI) | 64 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 290 acres |
| Public Access | Yes |
Where to stay near Lake Diane South Basin; Amboy Township
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Fishing Lake Diane South Basin; Amboy Township
Recreation & Access
Water Temperature
Lake Diane South Basin; Amboy Township averages about 59°F at the surface in summer, usually warmest in Jul (about 60°F) and coldest in May (about 53°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 443 field readings (2011–2017) via the EPA Water Quality Portal. See the full Lake Diane South Basin; Amboy Township water temperature breakdown →
Location
County Ranking
Ranked #5 of 7 lakes in Hillsdale County
Nearby Lakes in Hillsdale County
Explore Lake Diane South Basin; Amboy Township across LakeGrade
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Fish species and best lakes in Hillsdale County
Species activity outlook by water temperature and season
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High nutrients, frequent algae, reduced clarity
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Other Grade D Lakes in Michigan
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More records, surveys & data sources
Reservoir Info (USACE NID)
Lake Diane South Basin; Amboy Township is a man-made reservoir impounded by the Lake Diane Dam (completed 1966), built primarily for recreation on the Tributary to Clark Fork Creek; earth-type dam, 19 ft tall and 190 ft long.
- Surface area
- 290 ac
- Normal storage
- 1,700 ac-ft
- Max storage
- 3,200 ac-ft
- Drainage area
- 4.3 sq mi
- Hazard class
- Significant
- Owner
- Hillsdale County Drain Commissioner
Source: USACE National Inventory of Dams, NID ID MI00416 · Operator website · Matched by proximity (0.71 km)
EPA Impairment Status
Lake Diane South Basin; Amboy Township 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 MI041000030106-01 · Official waterbody report · Matched by proximity (0.92 km)
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 Lake Diane South Basin; Amboy Township under Clean Water Act (NPDES) discharge permits. 2 facilities have a reported Clean Water Act violation in the past three years.
- Pioneer Boy Scout CampPioneer · 1.7 mi away · NPDES OH0146421Recent violation
- Aqua Ohio Lake Seneca WtpMontpelier · 2.3 mi away · NPDES OH0138631Recent violation
- Mdot-M99-Hillsdale ReconstructHillsdale · 3.2 mi away · NPDES MIG081063
- Mdot-M99-HillsdaleHillsdale · 3.2 mi away · NPDES MIG081090
- Nettle Lake Area StpMontpelier · 3.9 mi away · NPDES OH0053376
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
Public boat-access points from the USGS National Boat Ramps inventory
Most recent sample: 2021-09-26
Monitoring stations: 1