Thomas Hill Reservoir
Randolph County, MissouriView mapDirections
Nutrients and algae run above the regional average.
- Eutrophic
- #7 of 7 in the county
- Public access
Thomas Hill Reservoir in Randolph County, Missouri has a water quality grade of D (Nutrient-rich). Water clarity: 2.3 ft visibility. Phosphorus: 61 µg/L. Chlorophyll-a (algae): 14.2 µg/L.
- Clarity
- 2.3 ft
- Type
- Eutrophic
- Trend
- ↑ Improving
- Public access
- Yes
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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 grade measures nutrients and algae, not lodging — cabins and rentals around Thomas Hill Reservoir are listed below.
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Thomas Hill Reservoir is a productive, nutrient-rich eutrophic lake in Randolph County, Missouri. Water quality is graded D based on 2 sampling years through 2025. 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 Safety
Grade onlyElevated nutrients
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 2.3 ft of visibility. Phosphorus 61 µg/L. Chlorophyll-a 14.2 µg/L. TSI 62. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.3 ft | Not graded |
| 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 |
County Ranking
Ranked #7 of 7 lakes in Randolph County
Nearby Lakes With Higher Grades
Thomas Hill Reservoir holds Grade D. 3 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 Randolph County
Frequently asked questions about Thomas Hill Reservoir
Where is Thomas Hill Reservoir?
- Thomas Hill Reservoir is a lake in Randolph County, Missouri. LakeQuality grades it D for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Thomas Hill Reservoir?
- Thomas Hill Reservoir in Randolph County, Missouri has a water quality grade of D (Nutrient-rich). 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?
- The D is nutrients and algae, 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.
Explore Thomas Hill Reservoir across LakeQuality
More Missouri Lake Rankings
Other Grade D 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)
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
Named boat-access points from the USGS National Boat Ramps inventory