Twelve Mile Lake
Union County, WisconsinEutrophic
Twelve Mile Lake is a 633-acre productive, nutrient-rich eutrophic lake in Union County, IA. Water quality is graded F based on 2 sampling years through 2024. Compared to the 5 other monitored lakes in Union County, Twelve Mile Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, local state DNR records, last sampled 2024-09-30. Grade methodology: LakeGrade methodology.
Swimming Safety
Avoid swimming, very poor water quality, potential algae toxins
Water Quality Grade: F, Very Poor
Very murky, less than 2.4 ft of visibility. Chlorophyll-a: 45 µg/L. Trophic State Index: 66.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.4 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 45 µg/L | F |
| Trophic State Index (TSI) | 66 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 633 acres |
Location
County Ranking
Ranked #3 of 6 lakes in Union County
Cleaner Lakes Within 30 Miles
Twelve Mile Lake holds Grade F. 3 nearby lakes hold higher grades.
- DThree Mile LakeUnion County · 2.4 mi · Higher grade (F → D)
- DThayer LakeUnion County · 10.1 mi · Higher grade (F → D)
- DNodaway LakeAdair County · 20.5 mi · Higher grade (F → D)
Nearby Lakes in Union County
More Wisconsin Lake Rankings
Other Grade F Lakes in Wisconsin
Eutrophic Lakes in Wisconsin
Reservoir Info (USACE NID)
Twelve Mile Lake is a man-made reservoir impounded by the Twelve Mile Creek Watershed Site M-1 (completed 1983), built primarily for flood risk reduction on the TWELVE MILE CREEK; earth-type dam, 66 ft tall and 2,100 ft long.
- Surface area
- 633 ac
- Normal storage
- 10,200 ac-ft
- Max storage
- 27,200 ac-ft
- Drainage area
- 23 sq mi
- Hazard class
- High
- Owner
- Creston Waterworks
All listed purposes: Flood Risk Reduction;Recreation;Water Supply.
Source: USACE National Inventory of Dams, NID ID IA02194 · Operator website · Matched by proximity (0.34 km)
EPA Impairment Status
Twelve Mile 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 IA 05-GRA-1367 · Official waterbody report · Matched by proximity (2.25 km)
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: 2024-09-30
Monitoring stations: 1