Smithville Lake
Clay County, WisconsinEutrophic
Smithville Lake is a 7,190-acre productive, nutrient-rich eutrophic lake in Clay County, MO. Water quality is graded D based on 3 sampling years through 2024. Compared to the 8 other monitored lakes in Clay County, Smithville Lake ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, local state DNR records, last sampled 2024-09-20. 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 ft of visibility. Phosphorus level: 48.8 µg/L. Chlorophyll-a: 27.2 µg/L. Trophic State Index: 64.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2 ft | F |
| Phosphorus | 48.8 µg/L | C |
| Chlorophyll-a (Algae) | 27.2 µg/L | D |
| Trophic State Index (TSI) | 64 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 7.2K acres |
Location
County Ranking
Ranked #4 of 9 lakes in Clay County
Cleaner Lakes Within 30 Miles
Smithville Lake holds Grade D. 3 nearby lakes hold higher grades.
- BWeatherby LakePlatte County · 17.5 mi · Two grade letters higher (D → B)
- CWaukomis LakePlatte County · 16 mi · Higher grade (D → C)
- DWatkins Mill LakeClay County · 15.1 mi · Higher overall water quality score
Nearby Lakes in Clay 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)
Smithville Lake is a man-made reservoir impounded by the Smithville Dam (completed 1979), built primarily for flood risk reduction on the LITTLE PLATTE RIVER; earth-type dam, 105 ft tall and 4,000 ft long.
- Surface area
- 7,190 ac
- Normal storage
- 144,600 ac-ft
- Max storage
- 246,500 ac-ft
- Drainage area
- 213 sq mi
- Hazard class
- High
- Owner
- USACE - Kansas City District
All listed purposes: Flood Risk Reduction;Other;Fish and Wildlife Pond;Recreation;Water Supply.
Source: USACE National Inventory of Dams, NID ID MO12084 · Operator website
EPA Impairment Status
Smithville Lake is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit MO_7077.00 · 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: 2024-09-20
Monitoring stations: 1