Smithville Lake by Dam
Clay County, Missouri7,190 acresView mapDirections
Nutrients and algae run above the regional average.
- Eutrophic
- #4 of 5 in the county
- Public access
Smithville Lake by Dam in Clay County, Missouri has a water quality grade of D (Nutrient-rich). Water clarity: 3.3 ft visibility. Phosphorus: 37.7 µg/L. Chlorophyll-a (algae): 25.4 µg/L. Surface area: 7190 acres.
- Clarity
- 3.3 ft
- Typical in September
- 76°F
- Area
- 7,190 acres
- Type
- Eutrophic
- Phosphorus
- 37.7 µg/L
- Chlorophyll-a
- 25.4 µg/L
- Trend
- ↑ Improving
- Public access
- Yes
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Stays near Smithville Lake by Dam
Compare lakeside cabins, hotels, and vacation rentals near Smithville Lake by Dam 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. The water-quality grade measures nutrients and algae, not lodging — cabins and rentals around Smithville Lake by Dam are listed below.
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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 2 sampling years through 2024. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 4 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: LakeQuality methodology.
What Smithville Lake by Dam is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
- Big water7,190 acres
Swimming Safety
Grade onlyAlgae risk
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
The D is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Water Quality Grade: D (Nutrient-rich)
Very murky, less than 3.3 ft of visibility. Phosphorus 37.7 µg/L. Chlorophyll-a 25.4 µg/L. TSI 60. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.3 ft | Not graded |
| Phosphorus | 37.7 µg/L | Good |
| Chlorophyll-a (Algae) | 25.4 µg/L | Poor |
| Trophic State Index (TSI) | 60 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Current Conditions
USGS snapshot Sep 7, 2026, 3:45 PM from gauge 06821140 (Smithville Reservoir near Smithville, MO). Station page ↗ — a live reading replaces this snapshot when the gauge responds. Missing live data is not an all-clear.
→ Smithville Lake by Dam water level: the live USGS gauge reading
Water Temperature
Smithville Lake by Dam typically sits around 76°F at the surface in September. Summer average is about 81°F. 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 →
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 7,190 acres |
| Public Access | Yes |
No bathymetric survey has been published for Smithville Lake by Dam, so its depth is not documented here.
Recreation & Access
- Little Platte ParkPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Smithville Lake by Dam
Water Quality Trend: ↑ Improving
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.002 m/yr | 4 |
| Phosphorus | → Stable | +0.25 µg/L/yr | 5 |
| Chlorophyll-a | ↑ Improving | -0.66 µg/L/yr | 5 |
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)
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.
County Ranking
Ranked #4 of 5 lakes in Clay County
Nearby Lakes With Higher Grades
Smithville Lake by Dam holds Grade D. 2 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Clay County
Frequently asked questions about Smithville Lake by Dam
Where is Smithville Lake by Dam?
- Smithville Lake by Dam is a lake in Clay County, Missouri. LakeQuality grades it D for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Smithville Lake by Dam?
- Smithville Lake by Dam in Clay County, Missouri has a water quality grade of D (Nutrient-rich). Water clarity: 3.3 ft visibility. Phosphorus: 37.7 µg/L. Chlorophyll-a (algae): 25.4 µg/L. Surface area: 7190 acres.
Is Smithville Lake by Dam safe to swim in?
- The D is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Smithville Lake by Dam?
- Smithville Lake by Dam typically sits around 76°F at the surface in September, from 82 EPA Water Quality Portal field readings (2010–2024). That is a typical value for the month, not a live reading.
What is the water level at Smithville Lake by Dam?
- The USGS snapshot on this page for Smithville Lake by Dam is 863.61 ft of gage height, recorded Sep 7, 2026, 3:45 PM at gauge 06821140. Current Conditions hydrates a live NWIS reading from that same station when the gauge responds. A missed live fetch is not an all-clear.
Are there boat ramps on Smithville Lake by Dam?
- Smithville Lake by Dam has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Little Platte Park. Public access is listed as yes.
Explore Smithville Lake by Dam across LakeQuality
Depth, room, public access, and the state wake-sport rules
Species activity outlook by water temperature and season
Where to stay at Missouri's top lakes, each with its grade
High nutrients, frequent algae, reduced clarity
Missouri's cleanest and most-polluted lakes, ranked
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Other Grade D Lakes in Missouri
Eutrophic Lakes in Missouri
Where this data comes from
83 measurements from 1 monitoring station, 2020–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Univ. of Missouri, Columbia
UMC83 samples · 2020–2024
Analytical methods
- Depth, Secchi disk in meters
- 4500 P E ~ Phosphorus in Water by Colorimetry- Ascorbic Acid Method
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
Monitoring station identifiers (1)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Named boat-access points from the USGS National Boat Ramps inventory