John Flannagan Reservoir
Dickenson County, VirginiaView mapDirections
Clarity, phosphorus, and algae all sit in the cleanest band for this region.
- Oligotrophic
- Impaired · Mercury
- #3 of 4 in the county
- Limited data
John Flannagan Reservoir in Dickenson County, Virginia has a water quality grade of A (Excellent). Water clarity: 13.1 ft visibility. Phosphorus: 10 µg/L. Chlorophyll-a (algae): 1.5 µg/L.
- Clarity
- 13.1 ft
- Type
- Oligotrophic
- Phosphorus
- 10 µg/L
- Chlorophyll-a
- 1.5 µg/L
- Trend
- ↑ Improving
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Watch John Flannagan Reservoir’s letter
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John Flannagan Reservoir is a cold, clear oligotrophic lake in Dickenson County, Virginia. Water quality is graded A based on 2 sampling years through 2026. Overall water quality is improving over recent sampling years. Compared to the 3 other monitored lakes in Dickenson County, John Flannagan Reservoir ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, Virginia DEQ, last sampled 2026-06-24. Grade methodology: LakeQuality methodology.
What John Flannagan Reservoir is good for
From access and monitoring records, not editorial picks.
- Clear water13.1 ft of visibility
Swimming Safety
Grade onlyLimited data
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. John Flannagan Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, oxygen depletion (low DO). Check local advisories before you swim.
Water Quality Grade: A (Excellent)
Good clarity, visible to about 13.1 ft. Phosphorus 10 µg/L. Chlorophyll-a 1.5 µg/L. TSI 37. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 13.1 ft | Not graded |
| Phosphorus | 10 µg/L | Good |
| Chlorophyll-a (Algae) | 1.5 µg/L | Good |
| Trophic State Index (TSI) | 37 | Oligotrophic |
Low nutrients, clear water. The letter is not a swimming clearance.
Fishing John Flannagan Reservoir
Water Quality Trend: ↑ Improving
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.25 m/yr | 2 |
EPA Impairment Status
John Flannagan Reservoir is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit VAS-Q13L_PNR01A02 · Official waterbody report
County Ranking
Ranked #3 of 4 lakes in Dickenson County
Nearby Lakes in Dickenson County
Frequently asked questions about John Flannagan Reservoir
Where is John Flannagan Reservoir?
- John Flannagan Reservoir is a lake in Dickenson County, Virginia. LakeQuality grades it A for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for John Flannagan Reservoir?
- John Flannagan Reservoir in Dickenson County, Virginia has a water quality grade of A (Excellent). Water clarity: 13.1 ft visibility. Phosphorus: 10 µg/L. Chlorophyll-a (algae): 1.5 µg/L.
Is John Flannagan Reservoir safe to swim in?
- The A is nutrients and algae, not a swimming clearance. John Flannagan Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, oxygen depletion (low DO). Check local advisories before you swim.
Explore John Flannagan Reservoir across LakeQuality
Species activity outlook by water temperature and season
Where to stay at Virginia's top lakes, each with its grade
Low nutrients, clear water. The letter is not a swimming clearance.
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Where this data comes from
37 measurements from 1 monitoring station, 2025–2026. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- VIRGINIA DEPARTMENT OF ENVIRONMENTAL QUALITY
21VASWCB37 samples · 2025–2026
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