Lake of Egypt
Williamson County, WisconsinEutrophic
Lake of Egypt is a 2,265-acre productive, nutrient-rich eutrophic lake in Williamson County, IL. Water quality is graded C based on 2 sampling years through 2020.
Source: EPA Water Quality Portal sampling records, local state DNR records, last sampled 2020-10-26. Grade methodology: LakeGrade methodology.
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 | 2.3K acres |
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
More Wisconsin Lake Rankings
Other Grade C Lakes in Wisconsin
Cook County · Clarity: 9 ft
Cook County · Clarity: 8.5 ft
Johnson County · Clarity: 4.5 ft
Gallatin County · Clarity: 3.9 ft
Rock Island County · Clarity: 4.2 ft
Cook County · Clarity: 5.4 ft
Eutrophic Lakes in Wisconsin
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
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Grading methodology based on Metropolitan Council standards
Most recent sample: 2020-10-26
Monitoring stations: 3