Lake of Egypt
Williamson County, Illinois2,265 acresView mapDirections
Nutrients and algae run above the regional average.
↓ down from C at the last regrade
- Eutrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- #1 of 1 in the county
- 75 ft max depth
- Public access
- Limited data
Lake of Egypt in Williamson County, Illinois has a water quality grade of D (Nutrient-rich). Water clarity: 3.2 ft visibility. Phosphorus: 40.5 µg/L. Chlorophyll-a (algae): 22.1 µg/L. Surface area: 2265 acres.
- Clarity
- 3.2 ft
- Typical in August
- 85°F
- Max depth
- ~75 ft est.
- Area
- 2,265 acres
- Type
- Eutrophic
- Public access
- Yes
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Stays near Lake of Egypt
Compare lakeside cabins, hotels, and vacation rentals near Lake of Egypt in Williamson County, Illinois — 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 grade measures nutrients and algae, not lodging — cabins and rentals around Lake of Egypt are listed below.
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Lake of Egypt is a 2,265-acre productive, nutrient-rich eutrophic lake in Williamson County, Illinois with an estimated average depth of about 75 feet. Water quality is graded D based on 2 sampling years through 2020. Limited fish-species data available. Public access is available with 9 public boat landings.
Source: EPA Water Quality Portal sampling records, Illinois EPA, last sampled 2020-10-26. Grade methodology: LakeQuality methodology.
What Lake of Egypt is good for
From access and monitoring records, not editorial picks.
- Boat launch9 documented ramps
- Big water2,265 acres
Swimming Safety
Grade onlyLimited data
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
The D is nutrients and algae, not a swimming clearance. Lake of Egypt is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen), pesticides, pCBs. Check local advisories before you swim.
Water Quality Grade: D (Nutrient-rich)
Very murky, less than 3.2 ft of visibility. Phosphorus 40.5 µg/L. Chlorophyll-a 22.1 µg/L. TSI 60. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.2 ft | Not graded |
| Phosphorus | 40.5 µg/L | Poor |
| Chlorophyll-a (Algae) | 22.1 µg/L | Poor |
| Trophic State Index (TSI) | 60 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Water Temperature
Lake of Egypt typically sits around 85°F at the surface in August. Summer average is about 82°F. 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 →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~75 ft est. |
| Average Depth | ~43 ft est. |
| Surface Area | 2,265 acres |
| Public Access | Yes |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Illinois has not published bathymetry for Lake of Egypt.
Lake Size & Watershed
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.
Recreation & Access
- Lake of EgyptPublic
- Lake of EgyptPublic
- Lake of EgyptPublic
- Lake of EgyptPublic
- Lake of EgyptPublic
- Lake of EgyptPublic
Showing 6 of 9 documented landings from the USGS National Boat Ramps inventory.
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Lake of Egypt
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
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.
County Ranking
Ranked #1 of 1 lakes in Williamson County
Nearby Lakes in Williamson County
Frequently asked questions about Lake of Egypt
Where is Lake of Egypt?
- Lake of Egypt is a lake in Williamson County, Illinois. LakeQuality grades it D for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Lake of Egypt?
- Lake of Egypt in Williamson County, Illinois has a water quality grade of D (Nutrient-rich). Water clarity: 3.2 ft visibility. Phosphorus: 40.5 µg/L. Chlorophyll-a (algae): 22.1 µg/L. Surface area: 2265 acres.
Is Lake of Egypt safe to swim in?
- The D is nutrients and algae, not a swimming clearance. Lake of Egypt is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen), pesticides, pCBs. Check local advisories before you swim.
What is the water temperature of Lake of Egypt?
- Lake of Egypt typically sits around 85°F at the surface in August, from 217 EPA Water Quality Portal field readings (2010–2020). That is a typical value for the month, not a live reading.
How deep is Lake of Egypt?
- No published bathymetric survey covers Lake of Egypt, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 75 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 2265 acres.
Are there boat ramps on Lake of Egypt?
- Lake of Egypt has 9 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Lake of Egypt, Lake of Egypt, Lake of Egypt, Lake of Egypt, among others. Public access is listed as yes.
Explore Lake of Egypt across LakeQuality
Depth, room, public access, and the state wake-sport rules
15 mi away · 100 ft
Species activity outlook by water temperature and season
Where to stay at Illinois's top lakes, each with its grade
High nutrients, frequent algae, reduced clarity
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Where this data comes from
56 measurements from 3 monitoring stations, 2020. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- illinois epa
IL_EPA_WQX56 samples · 2020
Analytical methods
- MEASURED IN FIELD
- Phosphorus by Colorimetry
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
Monitoring station identifiers (3)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated 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)
Named boat-access points from the USGS National Boat Ramps inventory