Lake of Egypt is a 2,265-acre productive, nutrient-rich eutrophic lake in Williamson County, Illinois. Water quality is graded C based on 2 sampling years through 2020. Limited fish-species data available. Public access is available with 11 public boat landings.
Source: EPA Water Quality Portal sampling records, Illinois DNR, last sampled 2020-10-26. Grade methodology: LakeGrade methodology.
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Swimming Safety
Generally safe for swimming, moderate water quality
Water Quality Grade: C, Fair
Very murky, less than 3.2 ft of visibility. Phosphorus level: 26 µg/L. Trophic State Index: 56.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.2 ft | F |
| Phosphorus | 26 µg/L | B |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 56 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 2,265 acres |
| Public Access | Yes |
Where to stay near Lake of Egypt
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Fishing Lake of Egypt
Recreation & Access
Water Temperature
Lake of Egypt averages about 82°F at the surface in summer, usually warmest in Aug (about 85°F) and coldest in Apr (about 60°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 217 field readings (2010–2020) via the EPA Water Quality Portal. See the full Lake of Egypt water temperature breakdown →
Location
County Ranking
Ranked #1 of 1 lakes in Williamson County
Cleaner Lakes Within 30 Miles
Lake of Egypt holds Grade C. 3 nearby lakes hold higher grades.
- BGlendale LakePope County · 18.9 mi · Higher grade (C → B)
- BOne Horse Gap LakePope County · 26.1 mi · Higher grade (C → B)
- CVienna Correctional Center LakeJohnson County · 15.3 mi · Higher overall water quality score
Nearby Lakes in Williamson County
Explore Lake of Egypt across LakeGrade
More Illinois Lake Rankings
Other Grade C Lakes in Illinois
Eutrophic Lakes in Illinois
More records, surveys & data sources
Reservoir Info (USACE NID)
Lake of Egypt is a man-made reservoir impounded by the Lake of Egypt Dam (completed 1962), built primarily for other on the SOUTH FORK SALINE RIVER; earth-type dam, 55 ft tall and 2,850 ft long.
- Surface area
- 2,265 ac
- Normal storage
- 41,215 ac-ft
- Max storage
- 82,942 ac-ft
- Drainage area
- 33.3 sq mi
- Hazard class
- High
- Owner
- SOUTHERN ILLINOIS POWER COOPERATIVE
All listed purposes: Other;Recreation.
Source: USACE National Inventory of Dams, NID ID IL00015 · Operator website
EPA Impairment Status
Lake of Egypt 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_RAL · Official waterbody report
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of Lake of Egypt under Clean Water Act (NPDES) discharge permits, including 1 classified by the EPA as major discharger. 1 facility has a reported Clean Water Act violation in the past three years.
- Southern Illinois Power Coopertive - Marion StationMarion · 2.6 mi away · NPDES IL0004316MajorRecent violation
- Lake Egypt Water Dist WtpMarion · 2.4 mi away · NPDES IL0076261
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: 2020-10-26
Monitoring stations: 3