Jacksonville Lake
Morgan County, WisconsinEutrophic
Jacksonville Lake is a 477-acre productive, nutrient-rich eutrophic lake in Morgan County, IL. Water quality is graded D based on 2 sampling years through 2022. Compared to the 1 other monitored lakes in Morgan County, Jacksonville Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, local state DNR records, last sampled 2022-10-18. 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 1.8 ft of visibility. Phosphorus level: 48 µg/L. Trophic State Index: 64.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.8 ft | F |
| Phosphorus | 48 µg/L | C |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 64 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 477 acres |
Location
County Ranking
Ranked #1 of 2 lakes in Morgan County
Nearby Lakes in Morgan County
More Wisconsin Lake Rankings
Other Grade D Lakes in Wisconsin
Eutrophic Lakes in Wisconsin
Reservoir Info (USACE NID)
Jacksonville Lake is a man-made reservoir impounded by the Lake Jacksonville Dam (completed 1939), built primarily for recreation on the SANDY CREEK; earth-type dam, 54 ft tall and 980 ft long.
- Surface area
- 477 ac
- Normal storage
- 6,099 ac-ft
- Max storage
- 12,812 ac-ft
- Drainage area
- 10.8 sq mi
- Hazard class
- Significant
- Owner
- CITY OF JACKSONVILLE
All listed purposes: Recreation;Water Supply.
Source: USACE National Inventory of Dams, NID ID IL00711 · Operator website
EPA Impairment Status
Jacksonville Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit IL_RDI · 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: 2022-10-18
Monitoring stations: 3