Duhernal Lake
Middlesex County, New Jersey195 acresView mapDirections
NJDEP publishes the water-quality measurements for Duhernal Lake. Here is what has been measured.
- Mesotrophic
- Impaired · Impaired biota (cause unknown)
Duhernal Lake in Middlesex County, New Jersey has water-quality measurements published by NJDEP, shown here as reported. Water clarity: 4.6 ft visibility. Phosphorus: 64 µg/L. Chlorophyll-a (algae): 4.4 µg/L. Surface area: 195 acres.
Duhernal Lake is a 195-acre mesotrophic lake in Middlesex County, New Jersey. Compared to the 2 other monitored lakes in Middlesex County, Duhernal Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2023-11-21. Methodology: how these readings are compared.
Swimming conditions
Readings onlyModerate 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. Duhernal Lake is listed impaired under Clean Water Act §303(d) (IR 5) for impaired biota (cause unknown), mercury, metals (other than mercury), oxygen depletion (low DO). Check local advisories before you swim.
Whether Duhernal 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 Duhernal Lake
These are the measurements NJDEP publishes for Duhernal Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Murky, only visible to about 4.6 ft. Phosphorus 64 µg/L. Chlorophyll-a 4.4 µg/L. TSI 55.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 4.6ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 64µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 4.4µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 55 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
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Lake Details
Surface area
195 acres
No bathymetric survey has been published for Duhernal Lake, so its depth is not documented here.
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Fishing Duhernal Lake
Reservoir Info (USACE NID)
Duhernal Lake is a man-made reservoir impounded by the Duhernal Dam (completed 1939), built primarily for recreation on the South River; earth-type dam, 13 ft tall and 878 ft long.
- Surface area
- 195 ac
- Normal storage
- 780 ac-ft
- Max storage
- 1,520 ac-ft
- Drainage area
- 94.6 sq mi
- Hazard class
- Significant
- Owner
- Borough of Sayreville
Source: USACE National Inventory of Dams, NID ID NJ00381 · Operator website
EPA Impairment Status
Duhernal 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: Drinking water, Aquatic life, Fish consumption.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit NJ02030105160030-01 · Official waterbody report
Nearby Lakes in Middlesex County
Frequently asked questions about Duhernal Lake
Where is Duhernal Lake?
- Duhernal Lake is a lake in Middlesex County, New Jersey. Its water-quality measurements are published by NJDEP and shown on this page as reported.
What is the water quality of Duhernal Lake?
- Duhernal Lake in Middlesex County, New Jersey has water-quality measurements published by NJDEP, shown here as reported. Water clarity: 4.6 ft visibility. Phosphorus: 64 µg/L. Chlorophyll-a (algae): 4.4 µg/L. Surface area: 195 acres.
Is Duhernal Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Duhernal Lake is listed impaired under Clean Water Act §303(d) (IR 5) for impaired biota (cause unknown), mercury, metals (other than mercury), oxygen depletion (low DO). Check local advisories before you swim.
Explore Duhernal Lake across LakeQuality
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Where this data comes from
219 measurements from 4 monitoring stations, 2022–2023. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- NJDEP Bureau of Freshwater and Biological Monitoring
NJDEP_BFBM219 samples · 2022–2023
Analytical methods
- Phosphorus by Colorimetry
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
- 2120 B ~ Color in Water by Visual Comparison
Monitoring station identifiers (4)
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