Smithville Lake is a 7,190-acre productive, nutrient-rich eutrophic lake in Clay County, Missouri. Water quality is graded D based on 3 sampling years through 2024. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 3 public boat landings. Compared to the 8 other monitored lakes in Clay County, Smithville Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, Missouri DNR, last sampled 2024-09-19. Grade methodology: LakeGrade methodology.
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Swimming Safety
Swimming not recommended, poor water quality with high algae risk
Water Quality Grade: D, Poor
Very murky, less than 2.6 ft of visibility. Phosphorus level: 34 µg/L. Chlorophyll-a: 27.6 µg/L. Trophic State Index: 60.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.6 ft | F |
| Phosphorus | 34 µg/L | C |
| Chlorophyll-a (Algae) | 27.6 µg/L | D |
| Trophic State Index (TSI) | 60 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 7,190 acres |
| Public Access | Yes |
Where to stay near Smithville Lake
Compare lakeside cabins, hotels, and vacation rentals near Smithville Lake in Clay County, Missouri — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
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Fishing Smithville Lake
Water Quality Trend: ↓ Declining
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.007 m/yr | 5 |
| Phosphorus | ↓ Declining | +1.14 µg/L/yr | 5 |
| Chlorophyll-a | → Stable | +0.23 µg/L/yr | 5 |
Recreation & Access
Water Temperature
Smithville Lake averages about 80°F at the surface in summer, usually warmest in Jul (about 82°F) and coldest in Apr (about 58°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 60 field readings (2017–2024) via the EPA Water Quality Portal.
Location
County Ranking
Ranked #3 of 9 lakes in Clay County
Cleaner Lakes Within 30 Miles
Smithville Lake holds Grade D. 2 nearby lakes hold higher grades.
- CWaukomis LakePlatte County · 13.6 mi · Higher grade (D → C)
- DWatkins Mill LakeClay County · 13.4 mi · Higher overall water quality score
Nearby Lakes in Clay County
Explore Smithville Lake across LakeGrade
More Missouri Lake Rankings
Other Grade D Lakes in Missouri
Eutrophic Lakes in Missouri
Compare Smithville Lake With Nearby Lakes
More records, surveys & data sources
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
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Smithville Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Johnson Ridge WwtfSmithville · 4.3 mi away · NPDES MO0132110Recent violation
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
Data Sources
Water quality data from the EPA Water Quality Portal
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Public boat-access points from the USGS National Boat Ramps inventory
Most recent sample: 2024-09-19
Monitoring stations: 1