Unl Lake
Sussex County, New Jersey4 acresView mapDirections
NJDEP publishes the water-quality measurements for Unl Lake. Here is what has been measured.
- Eutrophic
- Impaired · Impaired biota (cause unknown)
- Limited data
Unl Lake in Sussex County, New Jersey has water-quality measurements published by NJDEP, shown here as reported. Water clarity: 3.3 ft visibility. Phosphorus: 43.1 µg/L. Chlorophyll-a (algae): 12.9 µg/L. Surface area: 4 acres.
Unl Lake is a 4-acre productive, nutrient-rich eutrophic lake in Sussex County, New Jersey. Compared to the 17 other monitored lakes in Sussex County, Unl Lake ranks #13 for water quality.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2021-11-22. Methodology: how these readings are compared.
Swimming conditions
Readings onlyLimited data
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. Unl Lake is listed impaired under Clean Water Act §303(d) (IR 5) for impaired biota (cause unknown). Check local advisories before you swim.
Whether Unl Lake 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 Unl Lake
These are the measurements NJDEP publishes for Unl Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 3.3 ft of visibility. Phosphorus 43.1 µg/L. Chlorophyll-a 12.9 µg/L. TSI 58.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 3.3ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 43.1µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 12.9µg/L | Fair GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 58 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Unl Lake
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Lake Details
Surface area
4 acres
No bathymetric survey has been published for Unl Lake, so its depth is not documented here.
Stays via Stay22
Stays near Unl Lake
Compare lakeside cabins, hotels, and vacation rentals near Unl Lake in Sussex 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. The water-quality readings cover nutrients and algae, not lodging. Cabins and rentals around Unl Lake are listed below.
Top-rated places to stay near Unl Lake
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Fishing Unl Lake
Reservoir Info (USACE NID)
Unl Lake is a man-made reservoir impounded by the Branchville Reservoir Dam (completed 1934), built primarily for water supply on the Dry Brook; earth-type dam, 22 ft tall and 690 ft long.
- Surface area
- 4 ac
- Normal storage
- 21 ac-ft
- Drainage area
- 1 sq mi
- Hazard class
- Significant
- Owner
- Borough of Branchville
Source: USACE National Inventory of Dams, NID ID NJ00009 · Operator website · Matched by proximity (0.85 km)
EPA Impairment Status
Unl Lake 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: Aquatic life.
Source: EPA ATTAINS assessment unit NJ02040105040020-01 · Official waterbody report
Nearby Lakes in Sussex County
Frequently asked questions about Unl Lake
Where is Unl Lake?
- Unl Lake is a lake in Sussex County, New Jersey. Its water-quality measurements are published by NJDEP and shown on this page as reported.
What is the water quality of Unl Lake?
- Unl Lake in Sussex County, New Jersey has water-quality measurements published by NJDEP, shown here as reported. Water clarity: 3.3 ft visibility. Phosphorus: 43.1 µg/L. Chlorophyll-a (algae): 12.9 µg/L. Surface area: 4 acres.
Is Unl Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Unl Lake is listed impaired under Clean Water Act §303(d) (IR 5) for impaired biota (cause unknown). Check local advisories before you swim.
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Where this data comes from
22 measurements from 3 monitoring stations, 2021. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- NJDEP Bureau of Freshwater and Biological Monitoring
NJDEP_BFBM22 samples · 2021
Analytical methods
- Phosphorus by Colorimetry
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
Monitoring station identifiers (3)
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