Thomas Hill Res. Nr. Dam Lake
Randolph County, WisconsinEutrophic
Thomas Hill Res. Nr. Dam Lake is a 3,500-acre productive, nutrient-rich eutrophic lake in Randolph County, MO. Water quality is graded D based on 3 sampling years through 2025. Compared to the 6 other monitored lakes in Randolph County, Thomas Hill Res. Nr. Dam Lake ranks #6 for water quality.
Source: EPA Water Quality Portal sampling records, local state DNR records, last sampled 2025-08-14. 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 2.3 ft of visibility. Phosphorus level: 61 µg/L. Chlorophyll-a: 14.2 µg/L. Trophic State Index: 62.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.3 ft | F |
| Phosphorus | 61 µg/L | D |
| Chlorophyll-a (Algae) | 14.2 µg/L | C |
| Trophic State Index (TSI) | 62 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 3.5K acres |
Location
County Ranking
Ranked #6 of 7 lakes in Randolph County
Cleaner Lakes Within 30 Miles
Thomas Hill Res. Nr. Dam Lake holds Grade D. 5 nearby lakes hold higher grades.
- BLake Nehai TonkayeaChariton County · 13.3 mi · Two grade letters higher (D → B)
- COld ReservoirRandolph County · 13.6 mi · Higher grade (D → C)
- CRothwell LakeRandolph County · 13.6 mi · Higher grade (D → C)
- CThomas Hill Lake @ Hwy TMacon County · 4.9 mi · Higher grade (D → C)
- DSugar Creek LakeRandolph County · 11.2 mi · Higher overall water quality score
Nearby Lakes in Randolph County
More Wisconsin Lake Rankings
Other Grade D Lakes in Wisconsin
St. Louis city County · Clarity: 2.3 ft
Shelby County · Clarity: 3.2 ft
Macon County · Clarity: 1.8 ft
Harrison County · Clarity: 1.7 ft
Stone County · Clarity: 2.3 ft
Knox County · Clarity: 2.1 ft
Eutrophic Lakes in Wisconsin
Reservoir Info (USACE NID)
Thomas Hill Res. Nr. Dam Lake is a man-made reservoir impounded by the Thomas Hill Reservoir Dam (completed 1966), built primarily for flood risk reduction on the MIDDLE FORK CHARITON RIVER; earth-type dam, 70 ft tall and 2,450 ft long.
- Surface area
- 3,500 ac
- Normal storage
- 70,000 ac-ft
- Max storage
- 260,458 ac-ft
- Drainage area
- 146.88 sq mi
- Hazard class
- High
- Owner
- ASSOCIATED ELECTRIC CORP
All listed purposes: Flood Risk Reduction;Recreation.
Source: USACE National Inventory of Dams, NID ID MO10134 · Operator website · Matched by proximity (0.39 km)
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Most recent sample: 2025-08-14
Monitoring stations: 2