Round Valley Reservoir
Round Valley Reservoir in Hunterdon County, New Jersey has a water quality grade of A (Excellent). Water clarity: 26.9 ft visibility. Phosphorus: 7 µg/L. Chlorophyll-a (algae): 1.3 µg/L.
- Clarity
- 26.9 ft
- Type
- Oligotrophic
Round Valley Reservoir is a cold, clear oligotrophic lake in Hunterdon County, New Jersey. Water quality is graded A based on 2 sampling years through 2023. 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. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyBacteria advisory
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.
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A (Excellent)
Crystal clear, you can see 26.9 ft down. Phosphorus level: 7 µg/L. Chlorophyll-a: 1.3 µg/L. Trophic State Index: 32.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 26.9 ft | Not graded |
| Phosphorus | 7 µg/L | Good |
| Chlorophyll-a (Algae) | 1.3 µg/L | Good |
| Trophic State Index (TSI) | 32 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Round Valley Reservoir
Compare lakeside cabins, hotels, and vacation rentals near Round Valley Reservoir in Hunterdon County, New Jersey — 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.
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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
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit NJ02030105020090-01 · Official waterbody report · Matched by proximity (2.18 km)
County Ranking
Ranked #1 of 4 lakes in Hunterdon County
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. LakeQuality grades it A for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Round Valley Reservoir?
- Round Valley Reservoir in Hunterdon County, New Jersey has a water quality grade of A (Excellent). 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?
- Excellent for swimming, crystal clear water with minimal algae. Round Valley Reservoir has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 1.3 µg/L. Always check local health department advisories before swimming.
Explore Round Valley Reservoir across LakeGrade
More New Jersey Lake Rankings
Other Grade A Lakes in New Jersey
Oligotrophic Lakes in New Jersey
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)
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
Impairment status from EPA ATTAINS 303(d) database