Round Valley Reservoir
Hunterdon County, New JerseyView mapDirections
NJDEP publishes the water-quality measurements for Round Valley Reservoir. Here is what has been measured.
- Oligotrophic
- Impaired · Mercury
Round Valley Reservoir in Hunterdon County, New Jersey has water-quality measurements published by NJDEP, shown here as reported. Water clarity: 26.9 ft visibility. Phosphorus: 7 µg/L. Chlorophyll-a (algae): 1.3 µg/L.
Round Valley Reservoir is a cold, clear oligotrophic lake in Hunterdon County, New Jersey. Compared to the 3 other monitored lakes in Hunterdon County, Round Valley Reservoir ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2023-08-31. Methodology: how these readings are compared.
What Round Valley Reservoir is good for
From access and monitoring records, not editorial picks.
- Clear water26.9 ft of visibility
Swimming conditions
Readings onlyBacteria advisory
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. Round Valley Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, metals (other than mercury), nutrients (phosphorus, nitrogen), oxygen depletion (low DO), pathogens (E. coli, fecal), pesticides, pCBs, temperature. Check local advisories before you swim.
Whether Round Valley Reservoir is safe to swim in today is a call for the New Jersey Department of Environmental Protection and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Round Valley Reservoir
These are the measurements NJDEP publishes for Round Valley Reservoir, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Crystal clear, you can see 26.9 ft down. Phosphorus 7 µg/L. Chlorophyll-a 1.3 µg/L. TSI 32.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 26.9ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 7µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 1.3µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 32 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Round Valley Reservoir
Answers come straight from the public measurements and survey records on this page.
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Fishing Round Valley Reservoir
EPA Impairment Status
Round Valley 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: Drinking water, Aquatic life, Fish consumption, Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit NJ02030105020090-01 · Official waterbody report
Nearby Lakes in Hunterdon County
Frequently asked questions about Round Valley Reservoir
Where is Round Valley Reservoir?
- Round Valley Reservoir is a lake in Hunterdon County, New Jersey. Its water-quality measurements are published by NJDEP and shown on this page as reported.
What is the water quality of Round Valley Reservoir?
- Round Valley Reservoir in Hunterdon County, New Jersey has water-quality measurements published by NJDEP, shown here as reported. Water clarity: 26.9 ft visibility. Phosphorus: 7 µg/L. Chlorophyll-a (algae): 1.3 µg/L.
Is Round Valley Reservoir safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Round Valley Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, metals (other than mercury), nutrients (phosphorus, nitrogen), oxygen depletion (low DO), pathogens (E. coli, fecal), pesticides, pCBs, temperature. Check local advisories before you swim.
Explore Round Valley Reservoir across LakeQuality
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Where this data comes from
299 measurements from 4 monitoring stations, 2020–2023. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- NJDEP Bureau of Freshwater and Biological Monitoring
NJDEP_BFBM299 samples · 2020–2023
Analytical methods
- Phosphorus by Colorimetry
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
Monitoring station identifiers (4)
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