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
- Impaired · Algal growth
- Public access
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.
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. Methodology: how these readings are compared.
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. Thomas Hill Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth. 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.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 2.3ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 61µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 14.2µg/L | Fair GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 62 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Thomas Hill Reservoir
Answers come straight from the public measurements and survey records on this page.
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
Stays via Stay22
Stays near Thomas Hill Reservoir
Compare lakeside cabins, hotels, and vacation rentals near Thomas Hill Reservoir in Randolph 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 readings cover nutrients and algae, not lodging. Cabins and rentals around Thomas Hill Reservoir are listed below.
Top-rated places to stay near Thomas Hill Reservoir
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Fishing Thomas Hill Reservoir
Water Quality Trend: Improving
Based on 5 years of monitoring (2021–2025).
Water clarity
Improving3 years
Phosphorus
Improving-1.63 µg/L/yr5 years
Chlorophyll-a
Worsening+2.99 µg/L/yr5 years
EPA Impairment Status
Thomas Hill Reservoir is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Aquatic life.
Source: EPA ATTAINS assessment unit MO_7173.00 · Official waterbody report
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. Thomas Hill Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth. 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.
Can I fish at Thomas Hill Reservoir?
- Thomas Hill Reservoir has 2 documented boat landings in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Missouri's fish and wildlife agency, so check its current regulations before you go.
Explore Thomas Hill Reservoir across LakeQuality
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Other Lakes in Missouri
Eutrophic Lakes in Missouri
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
Impairment status from EPA ATTAINS 303(d) database
Named boat-access points from the USGS National Boat Ramps inventory