Cool Branch Lake
Franklin County, VirginiaView mapDirections
Clarity, phosphorus, and algae all sit in the cleanest band for this region.
- Mesotrophic
- Impaired · PCBs
- #4 of 13 in the county
- Public access
Cool Branch Lake in Franklin County, Virginia has a water quality grade of A (Excellent). Water clarity: 10.5 ft visibility. Phosphorus: 10 µg/L. Chlorophyll-a (algae): 2.1 µg/L.
- Clarity
- 10.5 ft
- Type
- Mesotrophic
- Phosphorus
- 10 µg/L
- Chlorophyll-a
- 2.1 µg/L
- Trend
- ↑ Improving
- Public access
- Yes
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Watch Cool Branch Lake’s letter
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Cool Branch Lake is a mesotrophic lake in Franklin County, Virginia. Water quality is graded A based on 2 sampling years through 2026. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available. Compared to the 12 other monitored lakes in Franklin County, Cool Branch Lake ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, Virginia DEQ, last sampled 2026-06-16. Grade methodology: LakeQuality methodology.
What Cool Branch Lake is good for
From access and monitoring records, not editorial picks.
- Clear water10.5 ft of visibility
Swimming Safety
Grade onlyLow algae
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 A is nutrients and algae, not a swimming clearance. Cool Branch Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for pCBs. Check local advisories before you swim.
Water Quality Grade: A (Excellent)
Good clarity, visible to about 10.5 ft. Phosphorus 10 µg/L. Chlorophyll-a 2.1 µg/L. TSI 39. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 10.5 ft | Not graded |
| Phosphorus | 10 µg/L | Good |
| Chlorophyll-a (Algae) | 2.1 µg/L | Good |
| Trophic State Index (TSI) | 39 | Mesotrophic |
Moderate nutrients, good water quality
Fishing Cool Branch Lake
Water Quality Trend: ↑ Improving
Based on 15 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.098 m/yr | 15 |
| Phosphorus | ↑ Improving | -0.27 µg/L/yr | 14 |
| Chlorophyll-a | ↑ Improving | -0.07 µg/L/yr | 14 |
EPA Impairment Status
Cool Branch Lake is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit VAW-L10L_COA01A10 · Official waterbody report · Matched by proximity (0.34 km)
County Ranking
Ranked #4 of 13 lakes in Franklin County
Nearby Lakes in Franklin County
Frequently asked questions about Cool Branch Lake
Where is Cool Branch Lake?
- Cool Branch Lake is a lake in Franklin County, Virginia. LakeQuality grades it A for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Cool Branch Lake?
- Cool Branch Lake in Franklin County, Virginia has a water quality grade of A (Excellent). Water clarity: 10.5 ft visibility. Phosphorus: 10 µg/L. Chlorophyll-a (algae): 2.1 µg/L.
Is Cool Branch Lake safe to swim in?
- The A is nutrients and algae, not a swimming clearance. Cool Branch Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for pCBs. Check local advisories before you swim.
Explore Cool Branch Lake across LakeQuality
More Virginia Lake Rankings
Other Grade A Lakes in Virginia
Mesotrophic Lakes in Virginia
Where this data comes from
642 measurements from 1 monitoring station, 2012–2026. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- VIRGINIA DEPARTMENT OF ENVIRONMENTAL QUALITY
21VASWCB642 samples · 2012–2026
Analytical methods
- Tyler, John. 1968. The secchi disk, Limnology and Oceanograpy, 13(1):1-6.
- Total Phosphorus After Block Digestion
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
- 446.0 ~ EPA; Chlorophylls and Pheopigments in Phytoplankton by Spectrophotometry
Monitoring station identifiers (1)
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