Randolph Lake
Randolph County, WisconsinEutrophic
Randolph Lake is a productive, nutrient-rich eutrophic lake in Randolph County, IL. Water quality is graded D based on 2 sampling years through 2021. Compared to the 2 other monitored lakes in Randolph County, Randolph Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, local state DNR records, last sampled 2021-10-13. Grade methodology: LakeGrade methodology.
Swimming Safety
Swimming not recommended, poor water quality with high algae risk
Water Quality Grade: D, Poor
Very murky, less than 1.7 ft of visibility. Phosphorus level: 49 µg/L. Trophic State Index: 65.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.7 ft | F |
| Phosphorus | 49 µg/L | C |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 65 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Location
County Ranking
Ranked #1 of 3 lakes in Randolph County
Cleaner Lakes Within 30 Miles
Randolph Lake holds Grade D. One nearby lake has a higher grade.
See full comparison →Nearby Lakes in Randolph County
More Wisconsin Lake Rankings
Other Grade D Lakes in Wisconsin
Eutrophic Lakes in Wisconsin
Reservoir Info (USACE NID)
Randolph Lake is a man-made reservoir impounded by the Randolph County Lake Dam (completed 1960), built primarily for recreation on the MORRISON BRANCH; earth-type dam, 47 ft tall and 665 ft long.
- Normal storage
- 946 ac-ft
- Max storage
- 1,563 ac-ft
- Hazard class
- Significant
- Owner
- ILLINOIS DEPARTMENT OF NATURAL RESOURCES
Source: USACE National Inventory of Dams, NID ID IL00551 · Operator website · Matched by proximity (0.44 km)
EPA Impairment Status
Randolph 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_RIB · 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: 2021-10-13
Monitoring stations: 3