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 #2 for water quality.
Source: EPA Water Quality Portal sampling records, Missouri DNR, last sampled 2024-09-20. Grade methodology: LakeGrade methodology.
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Smithville Lake Water Quality Report Card (2026)
A printable one-page report card for Smithville Lake: grade, clarity, phosphorus, algae, multi-year trend, depth, and fish — with sources.
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 | 7,190 acres |
| Public Access | Yes |
Where to stay near Smithville Lake
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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 | -0.001 m/yr | 5 |
| Phosphorus | ↓ Declining | +1.86 µg/L/yr | 5 |
| Chlorophyll-a | ↓ Declining | +5.13 µg/L/yr | 5 |
Recreation & Access
Current Conditions
Latest reading Jul 6, 2026, 4:45 AM from USGS gauge 06821140. See live data ↗ — readings update every 15–60 minutes; this page refreshes on each build.
Water Temperature
Smithville Lake averages about 82°F at the surface in summer, usually warmest in Jul (about 84°F) and coldest in Apr (about 59°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 72 field readings (2016–2024) via the EPA Water Quality Portal.
Location
County Ranking
Ranked #2 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
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
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
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
5 EPA-permitted facilities operate within about 5 miles of Smithville Lake under Clean Water Act (NPDES) discharge permits. 5 facilities have a reported Clean Water Act violation in the past three years.
- Bauman Park At Smithville LakeSmithville · 1.7 mi away · NPDES MO0126799Recent violation
- Mawc, Trimble WwtfTrimble · 2.4 mi away · NPDES MO0113751Recent violation
- Mawc Clinton Estates WwtpTrimble · 2.4 mi away · NPDES MO0129836Recent violation
- Mawc, Timber Springs Estates WwtfTrimble · 3.8 mi away · NPDES MO0123099Recent violation
- Mawc, Centennial Acres WwtfTrimble · 3.9 mi away · NPDES MO0117447Recent 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
Impairment status from EPA ATTAINS 303(d) database
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: 2024-09-20
Monitoring stations: 1