Watkins Mill Lake
Clay County, Missouri100 acresView mapDirections
Nutrients and algae sit mid-range for this region.
↑ up from D at the last regrade
- Eutrophic
- #1 of 5 in the county
- 29 ft max depth
Watkins Mill Lake in Clay County, Missouri has a water quality grade of C (Fair). Water clarity: 3.2 ft visibility. Phosphorus: 39.2 µg/L. Chlorophyll-a (algae): 17.7 µg/L. Surface area: 100 acres.
- Clarity
- 3.2 ft
- Typical in September
- 79°F
- Max depth
- ~29 ft est.
- Area
- 100 acres
- Type
- Eutrophic
- Phosphorus
- 39.2 µg/L
- Chlorophyll-a
- 17.7 µg/L
- Trend
- ↓ Declining
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Watch Watkins Mill Lake’s letter
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Watkins Mill Lake is a 100-acre productive, nutrient-rich eutrophic lake in Clay County, Missouri with an estimated average depth of about 29 feet. Water quality is graded C based on 2 sampling years through 2024. Overall water quality is declining over recent sampling years. Compared to the 4 other monitored lakes in Clay County, Watkins Mill Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Missouri DNR, last sampled 2024-08-07. Grade methodology: LakeQuality methodology.
Swimming Safety
Grade onlyBacteria D
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.
Based on E. coli testing, Watkins Mill Lake frequently exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 11.7% of 264 samples across 8 seasons.
This is a historical summary of past testing, not a current condition — bacteria levels change quickly, especially after rain. Always check Missouri’s current beach and health-department advisories before swimming.
Water Quality Grade: C (Fair)
Very murky, less than 3.2 ft of visibility. Phosphorus 39.2 µg/L. Chlorophyll-a 17.7 µg/L. TSI 59. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.2 ft | Not graded |
| Phosphorus | 39.2 µg/L | Fair |
| Chlorophyll-a (Algae) | 17.7 µg/L | Fair |
| Trophic State Index (TSI) | 59 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Water Temperature
Watkins Mill Lake typically sits around 79°F at the surface in September. Summer average is about 82°F. Usually warmest in Jul (about 84°F) and coldest in May (about 74°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 63 field readings (2010–2024) via the EPA Water Quality Portal. See the full Watkins Mill Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~29 ft est. |
| Average Depth | ~13 ft est. |
| Surface Area | 100 acres |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Missouri has not published bathymetry for Watkins Mill Lake.
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Fishing Watkins Mill Lake
Water Quality Trend: ↓ Declining
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.08 m/yr | 4 |
| Phosphorus | ↓ Declining | +1 µg/L/yr | 5 |
| Chlorophyll-a | ↑ Improving | -2.21 µg/L/yr | 5 |
Reservoir Info (USACE NID)
Watkins Mill Lake is a man-made reservoir impounded by the Watkins Mill State Park Dam (completed 1971), built primarily for recreation on the TR-WILLIAMS CREEK; earth-type dam, 55 ft tall and 1,600 ft long.
- Surface area
- 100 ac
- Normal storage
- 2,600 ac-ft
- Max storage
- 2,600 ac-ft
- Drainage area
- 2.95 sq mi
- Hazard class
- High
- Owner
- MO. DNR PARKS
All listed purposes: Recreation;Flood Risk Reduction.
Source: USACE National Inventory of Dams, NID ID MO10011 · Operator website · Matched by proximity (0.11 km)
Regulated Pollution Sources Nearby
9 EPA-permitted facilities operate within about 5 miles of Watkins Mill Lake under Clean Water Act (NPDES) discharge permits. 5 facilities have a reported Clean Water Act violation in the past three years.
- Shelton Estates WwtfExcelsior Springs · 2.2 mi away · NPDES MO0103276Recent violation
- Excelsior Estates WwtpLawson · 3.3 mi away · NPDES MO0108511Recent violation
- Indian Ridge Mobile Home Court WwtfExcelsior Springs · 3.9 mi away · NPDES MO0107492Recent violation
- Homestead Village WwtpExcelsior Springs · 4 mi away · NPDES MO0056545Recent violation
- Mawc, Lawson LagoonLawson · 4.5 mi away · NPDES MO0091031Recent violation
- Watkins Woolen Mill State Park & StateLawson · 0.2 mi away · NPDES MO0034959
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 #1 of 5 lakes in Clay County
Nearby Lakes in Clay County
Frequently asked questions about Watkins Mill Lake
Where is Watkins Mill Lake?
- Watkins Mill Lake is a lake in Clay County, Missouri. LakeQuality grades it C for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Watkins Mill Lake?
- Watkins Mill Lake in Clay County, Missouri has a water quality grade of C (Fair). Water clarity: 3.2 ft visibility. Phosphorus: 39.2 µg/L. Chlorophyll-a (algae): 17.7 µg/L. Surface area: 100 acres.
Is Watkins Mill Lake safe to swim in?
- Based on E. coli testing, Watkins Mill Lake frequently exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 11.7% of 264 samples across 8 seasons. That works out to a bacteria swim-safety grade of D — a historical summary of past testing, not a current reading. Watkins Mill Lake has a water quality grade of C (Fair). Bacteria levels can spike quickly after heavy rain, so always check Missouri's current beach and health-department advisories before you swim.
What is the water temperature of Watkins Mill Lake?
- Watkins Mill Lake typically sits around 79°F at the surface in September, from 63 EPA Water Quality Portal field readings (2010–2024). That is a typical value for the month, not a live reading.
How deep is Watkins Mill Lake?
- No published bathymetric survey covers Watkins Mill Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 29 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate. The lake covers 100 acres.
Explore Watkins Mill Lake across LakeQuality
More Missouri Lake Rankings
Other Grade C Lakes in Missouri
Eutrophic Lakes in Missouri
Where this data comes from
83 measurements from 2 monitoring stations, 2020–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Univ. of Missouri, Columbia
UMC80 samples · 2020–2024 - Missouri Dept. of Natural Resources
MDNR3 samples · 2020
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
- Nitrogen and Phosphorus, Total, Whole-water, Alkaline Persulfate Digest
Monitoring station identifiers (2)
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)
Lake size & watershed from HydroLAKES (HydroSHEDS)