Lake Diane
Hillsdale County, Michigan290 acresView mapDirections
EGLE publishes the water-quality measurements for Lake Diane. Here is what has been measured.
- Eutrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- 27 ft max depth
- Public access
Lake Diane in Hillsdale County, Michigan has water-quality measurements published by EGLE, shown here as reported. Water clarity: 2.5 ft visibility. Phosphorus: 51 µg/L. Chlorophyll-a (algae): 20 µg/L. Surface area: 290 acres.
Lake Diane is a 290-acre productive, nutrient-rich eutrophic lake in Hillsdale County, Michigan with an estimated average depth of about 27 feet. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available. Compared to the 1 other monitored lakes in Hillsdale County, Lake Diane ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, EGLE, last sampled 2021-09-26. Methodology: how these readings are compared.
Lake Diane covers about 290 acres in Hillsdale County. If you are planning to stay, you can search lake houses and cabins around Lake Diane on Vrbo, or look for a hotel room near the lake on Booking.com or Expedia.
Swimming conditions
Readings onlyAlgae risk
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. Lake Diane is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Lake Diane 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 Lake Diane
These are the measurements EGLE publishes for Lake Diane, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 2.5 ft of visibility. Phosphorus 51 µg/L. Chlorophyll-a 20 µg/L. TSI 62.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 2.5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 51µg/L | Fair GoodFairPoor |
| Chlorophyll-a (algae) | 20µg/L | Poor GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 62 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Lake Diane
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Lake Diane typically sits around 57°F at the surface in September. Summer average is about 59°F. Usually warmest in Jul (about 60°F) and coldest in May (about 53°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (53°F) to its warmest (60°F).
Typical surface water temperature by month, from 443 field readings (2011–2017) via the EPA Water Quality Portal. See the full Lake Diane water temperature breakdown →
Lake Details
Max depth
~27 ft est.
Surface area
290 acres
Public access
Yes
Listed by EGLE
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Michigan has not published bathymetry for Lake Diane.
Lake Size & Watershed
Watershed (drainage) area
3 sq mi
HydroLAKES / HydroSHEDS
Shoreline
7.8 mi
HydroLAKES / HydroSHEDS
Elevation
951 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Stays via Stay22
Stays near Lake Diane
Compare lakeside cabins, hotels, and vacation rentals near Lake Diane in Hillsdale 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. The water-quality readings cover nutrients and algae, not lodging. Cabins and rentals around Lake Diane are listed below.
Top-rated places to stay near Lake Diane
Prices for Oct 23–25, 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 →
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Fishing Lake Diane
Water Quality Trend: Worsening
Based on 5 years of monitoring (2016–2021).
Water clarity
Worsening4 years
Phosphorus
Worsening+5.04 µg/L/yr5 years
Chlorophyll-a
Worsening+4.89 µg/L/yr4 years
Reservoir Info (USACE NID)
Lake Diane 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 is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Aquatic life.
Source: EPA ATTAINS assessment unit MI041000030106-01 · Official waterbody report
Regulated Pollution Sources Nearby
5 EPA-permitted facilities operate within about 5 miles of Lake Diane 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.
Nearby Lakes in Hillsdale County
Frequently asked questions about Lake Diane
Where is Lake Diane?
- Lake Diane is a lake in Hillsdale County, Michigan. Its water-quality measurements are published by EGLE and shown on this page as reported.
What is the water quality of Lake Diane?
- Lake Diane in Hillsdale County, Michigan has water-quality measurements published by EGLE, shown here as reported. Water clarity: 2.5 ft visibility. Phosphorus: 51 µg/L. Chlorophyll-a (algae): 20 µg/L. Surface area: 290 acres.
Is Lake Diane safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Lake Diane is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
What is the water temperature of Lake Diane?
- Lake Diane typically sits around 57°F at the surface in September, from 443 EPA Water Quality Portal field readings (2011–2017). That is a typical value for the month, not a live reading.
How deep is Lake Diane?
- No published bathymetric survey covers Lake Diane, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 27 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate. The lake covers 290 acres.
Can I fish at Lake Diane?
- Public access to Lake Diane is listed as yes on the lake record. Seasons, size and bag limits, and whether you need a license are set by Michigan's fish and wildlife agency, so check its current regulations before you go.
Explore Lake Diane across LakeQuality
Depth, room, public access, and the state wake-sport rules
Fish species and the cleanest lakes across Michigan
Fish species and best lakes in Hillsdale 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
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Other Lakes in Michigan
Eutrophic Lakes in Michigan
Where this data comes from
66 measurements from 1 monitoring station, 2016–2021. Retrieved from the EPA Water Quality Portal on 2026-08-26.
Collected and reported by
- Michigan EGLE - MiCorps
21MICH_MICORPS66 samples · 2016–2021
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.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)