Lake Nehai Tonkayea is a 250-acre cold, clear oligotrophic lake in Chariton County, Missouri. Water quality is graded B based on 3 sampling years through 2023. Overall water quality is improving over recent sampling years. Compared to the 2 other monitored lakes in Chariton County, Lake Nehai Tonkayea ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Missouri DNR, last sampled 2023-08-10. Grade methodology: LakeGrade methodology.
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Swimming Safety
Good for swimming, clear water with low algae levels
Water Quality Grade: B, Good
Moderate clarity, visible to about 8 ft. Phosphorus level: 10 µg/L. Chlorophyll-a: 1.3 µg/L. Trophic State Index: 39.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 8 ft | C |
| Phosphorus | 10 µg/L | A |
| Chlorophyll-a (Algae) | 1.3 µg/L | A |
| Trophic State Index (TSI) | 39 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 250 acres |
Where to stay near Lake Nehai Tonkayea
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Fishing Lake Nehai Tonkayea
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
Source: USGS Nonindigenous Aquatic Species (NAS) Database. Hover a chip to see scientific name, ecological context, status, and first-observed year.
Water Quality Trend: ↑ Improving
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.115 m/yr | 3 |
| Phosphorus | ↑ Improving | -0.35 µg/L/yr | 3 |
| Chlorophyll-a | ↑ Improving | -0.4 µg/L/yr | 3 |
Water Temperature
Lake Nehai Tonkayea averages about 82°F at the surface in summer, usually warmest in Jul (about 83°F) and coldest in May (about 69°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 19 field readings (2015–2023) via the EPA Water Quality Portal. See the full Lake Nehai Tonkayea water temperature breakdown →
Location
County Ranking
Ranked #1 of 3 lakes in Chariton County
Nearby Lakes in Chariton County
Explore Lake Nehai Tonkayea across LakeGrade
Species activity outlook by water temperature and season
Where to stay at Missouri's top lakes, each with its grade
Low nutrients, clear water, excellent for swimming
Missouri's cleanest and most-polluted lakes, ranked
More Missouri Lake Rankings
Other Grade B Lakes in Missouri
Oligotrophic Lakes in Missouri
More records, surveys & data sources
Reservoir Info (USACE NID)
Lake Nehai Tonkayea is a man-made reservoir impounded by the Nehai Tonkayea Lake Dam (completed 1970), built primarily for recreation on the TR-MUSSEL FORK; earth-type dam, 65 ft tall and 1,700 ft long.
- Surface area
- 250 ac
- Normal storage
- 5,417 ac-ft
- Max storage
- 9,100 ac-ft
- Drainage area
- 1.48 sq mi
- Hazard class
- Low
- Owner
- NEHAI TONKAYEA POA
Source: USACE National Inventory of Dams, NID ID MO10627 · 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 Lake Nehai Tonkayea under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Lake Nehai Tonkayea WwtpKeytesville · 0.2 mi away · NPDES MO0088510Recent 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
Most recent sample: 2023-08-10
Monitoring stations: 1