Carlyle Lake is a 24,580-acre highly nutrient-loaded hypereutrophic lake in Clinton County, Illinois. Water quality is graded F based on 2 sampling years through 2021. Limited fish-species data available. Public access is available with 5 public boat landings.
Source: EPA Water Quality Portal sampling records, Illinois DNR, last sampled 2021-11-03. Grade methodology: LakeGrade methodology.
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Swimming Safety
Avoid swimming, very poor water quality, potential algae toxins
Water Quality Grade: F, Very Poor
Very murky, less than 1.8 ft of visibility. Phosphorus level: 200.5 µg/L. Trophic State Index: 75.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.8 ft | F |
| Phosphorus | 200.5 µg/L | F |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 75 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 24,580 acres |
| Public Access | Yes |
Where to stay near Carlyle Lake
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Fishing Carlyle Lake
Recreation & Access
Location
County Ranking
Ranked #1 of 1 lakes in Clinton County
Cleaner Lakes Within 30 Miles
Carlyle Lake holds Grade F. 2 nearby lakes hold higher grades.
- DKinmundy New LakeMarion County · 22.6 mi · Higher grade (F → D)
- DCentralia LakeMarion County · 17.6 mi · Higher grade (F → D)
Nearby Lakes in Clinton County
Explore Carlyle Lake across LakeGrade
Species activity outlook by water temperature and season
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Very high nutrients, dense algae, poor clarity
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More records, surveys & data sources
Reservoir Info (USACE NID)
Carlyle Lake is a man-made reservoir impounded by the Carlyle Dam - Keyesport Levee (completed 1966), built primarily for flood risk reduction on the KASKASKIA RIVER; earth-type dam, 23 ft tall and 9,945 ft long.
- Surface area
- 24,580 ac
- Normal storage
- 233,000 ac-ft
- Max storage
- 1,286,900 ac-ft
- Drainage area
- 0.9 sq mi
- Hazard class
- High
- Owner
- USACE - St. Louis District
All listed purposes: Flood Risk Reduction;Other;Navigation;Fish and Wildlife Pond;Recreation;Water Supply.
Source: USACE National Inventory of Dams, NID ID IL00113 · Operator website
EPA Impairment Status
Carlyle Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IL_ROA · Official waterbody report
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
3 EPA-permitted facilities operate within about 5 miles of Carlyle Lake under Clean Water Act (NPDES) discharge permits. 3 facilities have a reported Clean Water Act violation in the past three years.
- Department Of The ArmyCarlyle · 2.2 mi away · NPDES IL0025933Recent violation
- Hickory Shores Resort - StpCarlyle · 3.2 mi away · NPDES IL0061697Recent violation
- Eldon Hazlet State Park Campground StpCarlyle · 3.5 mi away · NPDES IL0053996Recent violation
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: 2021-11-03
Monitoring stations: 5