Smithville Lake by Dam 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 1 public boat landing. Compared to the 8 other monitored lakes in Clay County, Smithville Lake by Dam ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, Missouri DNR, last sampled 2024-09-12. 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 3.3 ft of visibility. Phosphorus level: 37 µg/L. Chlorophyll-a: 25.3 µg/L. Trophic State Index: 60.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.3 ft | F |
| Phosphorus | 37 µg/L | C |
| Chlorophyll-a (Algae) | 25.3 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 by Dam
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Fishing Smithville Lake by Dam
Water Quality Trend: ↓ Declining
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.002 m/yr | 4 |
| Phosphorus | ↓ Declining | +0.8 µg/L/yr | 5 |
| Chlorophyll-a | → Stable | +0.32 µg/L/yr | 5 |
Recreation & Access
Water Temperature
Smithville Lake by Dam averages about 81°F at the surface in summer, usually warmest in Jul (about 83°F) and coldest in Apr (about 57°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 82 field readings (2010–2024) via the EPA Water Quality Portal. See the full Smithville Lake by Dam water temperature breakdown →
Location
County Ranking
Ranked #4 of 9 lakes in Clay County
Cleaner Lakes Within 30 Miles
Smithville Lake by Dam holds Grade D. 2 nearby lakes hold higher grades.
- BWeatherby LakePlatte County · 14.2 mi · Two grade letters higher (D → B)
- CWaukomis LakePlatte County · 12.5 mi · Higher grade (D → C)
Nearby Lakes in Clay County
Explore Smithville Lake by Dam across LakeGrade
More Missouri Lake Rankings
Other Grade D Lakes in Missouri
Eutrophic Lakes in Missouri
Compare Smithville Lake by Dam With Nearby Lakes
More records, surveys & data sources
Reservoir Info (USACE NID)
Smithville Lake by Dam 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 · Matched by proximity (0.52 km)
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
4 EPA-permitted facilities operate within about 5 miles of Smithville Lake by Dam under Clean Water Act (NPDES) discharge permits, including 2 classified by the EPA as major dischargers. 2 facilities have a reported Clean Water Act violation in the past three years.
- Smithville WwtpSmithville · 2.1 mi away · NPDES MO0055204MajorRecent violation
- Kc Rocky Branch WwtpKansas City · 4.2 mi away · NPDES MO0048305MajorRecent violation
- Raptor Recycle And Transfer SmithvilleSmithville · 3.2 mi away · NPDES MONX01016
- Pcrsd South Gale WwtpSmithville · 4.9 mi away · NPDES MO0128074
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: 2024-09-12
Monitoring stations: 1