Thomas Hill Reservoir
Randolph County, MissouriView mapDirections
Missouri DNR publishes the water-quality measurements for Thomas Hill Reservoir. Here is what has been measured.
- Eutrophic
- Public access
Ask about Thomas Hill Reservoir
Answers come straight from the public measurements and survey records on this page.
Thomas Hill Reservoir in Randolph County, Missouri has water-quality measurements published by Missouri DNR, shown here as reported. Water clarity: 2.3 ft visibility. Phosphorus: 61 µg/L. Chlorophyll-a (algae): 14.2 µg/L.
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Thomas Hill Reservoir is a productive, nutrient-rich eutrophic lake in Randolph County, Missouri. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 2 public boat landings. Compared to the 6 other monitored lakes in Randolph County, Thomas Hill Reservoir ranks #7 for water quality.
Source: EPA Water Quality Portal sampling records, Missouri DNR, last sampled 2025-08-14. Grade methodology: LakeQuality methodology.
What Thomas Hill Reservoir is good for
From access and monitoring records, not editorial picks.
- Boat launch2 documented ramps
Swimming conditions
Readings onlyElevated nutrients
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Thomas Hill Reservoir is safe to swim in today is a call for the Missouri Department of Natural Resources and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Thomas Hill Reservoir
These are the measurements Missouri DNR publishes for Thomas Hill Reservoir, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 2.3 ft of visibility. Phosphorus 61 µg/L. Chlorophyll-a 14.2 µg/L. TSI 62.
| Metric | Value | EPA condition class |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.3 ft | Measured, not scored |
| Phosphorus | 61 µg/L | Poor |
| Chlorophyll-a (Algae) | 14.2 µg/L | Fair |
| Trophic State Index (TSI) | 62 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Recreation & Access
- Thomas Hill Reservoir Conservation AreaPublic
- Thomas Hill Reservoir Conservation AreaPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Thomas Hill Reservoir
Water Quality Trend: ↑ Improving
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.095 m/yr | 3 |
| Phosphorus | ↑ Improving | -1.63 µg/L/yr | 5 |
| Chlorophyll-a | ↓ Declining | +2.99 µg/L/yr | 5 |
Nearby Lakes in Randolph County
Frequently asked questions about Thomas Hill Reservoir
Where is Thomas Hill Reservoir?
- Thomas Hill Reservoir is a lake in Randolph County, Missouri. Its water-quality measurements are published by Missouri DNR and shown on this page as reported.
What is the water quality of Thomas Hill Reservoir?
- Thomas Hill Reservoir in Randolph County, Missouri has water-quality measurements published by Missouri DNR, shown here as reported. Water clarity: 2.3 ft visibility. Phosphorus: 61 µg/L. Chlorophyll-a (algae): 14.2 µg/L.
Is Thomas Hill Reservoir safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Are there boat ramps on Thomas Hill Reservoir?
- Thomas Hill Reservoir has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Thomas Hill Reservoir Conservation Area, Thomas Hill Reservoir Conservation Area. Public access is listed as yes.
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Where this data comes from
67 measurements from 2 monitoring stations, 2021–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Univ. of Missouri, Columbia
UMC64 samples · 2021–2024 - Missouri Dept. of Natural Resources
MDNR3 samples · 2025
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
- Turbidity by Nephelometry
Monitoring station identifiers (2)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Named boat-access points from the USGS National Boat Ramps inventory