Black River Confluence Lake
Sullivan County, New HampshireView mapDirections
NHDES publishes the water-quality measurements for Black River Confluence Lake. Here is what has been measured.
- Mesotrophic
- Impaired · Mercury
- Public access
Black River Confluence Lake in Sullivan County, New Hampshire has water-quality measurements published by NHDES, shown here as reported. Phosphorus: 14.2 µg/L.
Black River Confluence Lake is a mesotrophic lake in Sullivan County, New Hampshire. Limited fish-species data available. Public access is available. Compared to the 23 other monitored lakes in Sullivan County, Black River Confluence Lake ranks #14 for water quality.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2022-07-31. Methodology: how these readings are compared.
Swimming conditions
Readings onlyLow algae
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. Black River Confluence Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, pH / acidity. Check local advisories before you swim.
Whether Black River Confluence Lake is safe to swim in today is a call for the New Hampshire Department of Environmental Services and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Black River Confluence Lake
These are the measurements NHDES publishes for Black River Confluence Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
No clarity data. Phosphorus 14.2 µg/L. TSI 42.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | No reading How deep a black-and-white disk stays visible from the surface. Higher is clearer. | |
| Total phosphorus | 14.2µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | No reading The green pigment in algae — a direct measure of how much algae is in the water. | |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 42 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
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Fishing Black River Confluence Lake
EPA Impairment Status
Black River Confluence Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Aquatic life, Fish consumption.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit NHIMP801060703-05 · Official waterbody report
Nearby Lakes in Sullivan County
Frequently asked questions about Black River Confluence Lake
Where is Black River Confluence Lake?
- Black River Confluence Lake is a lake in Sullivan County, New Hampshire. Its water-quality measurements are published by NHDES and shown on this page as reported.
What is the water quality of Black River Confluence Lake?
- Black River Confluence Lake in Sullivan County, New Hampshire has water-quality measurements published by NHDES, shown here as reported. Phosphorus: 14.2 µg/L.
Is Black River Confluence Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Black River Confluence Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, pH / acidity. Check local advisories before you swim.
Can I fish at Black River Confluence Lake?
- Public access to Black River Confluence Lake is listed as yes on the lake record. Seasons, size and bag limits, and whether you need a license are set by New Hampshire's fish and wildlife agency, so check its current regulations before you go.
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Where this data comes from
24 measurements from 1 monitoring station, 2021–2022. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- New Hampshire Department Of Environmental Services (BEACH)
1111330024 samples · 2021–2022
Analytical methods
- 4500 P H ~ Manual Digestion and Flow Injection Analysis for Total Phosphorus
- 4500 N C ~ Persufate Method for Total Nitrogen
Monitoring station identifiers (1)
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