Delaware Lake
Warren County, New Jersey38 acresView mapDirections
NJDEP publishes the water-quality measurements for Delaware Lake. Here is what has been measured.
- Hypereutrophic
- Impaired · Metals (other than mercury)
Delaware Lake in Warren County, New Jersey has water-quality measurements published by NJDEP, shown here as reported. Water clarity: 1.6 ft visibility. Phosphorus: 156.5 µg/L. Chlorophyll-a (algae): 106.1 µg/L. Surface area: 38 acres.
Delaware Lake is a 38-acre highly nutrient-loaded hypereutrophic lake in Warren County, New Jersey. Compared to the 1 other monitored lakes in Warren County, Delaware Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2024-09-30. Methodology: how these readings are compared.
Swimming conditions
Readings onlyBacteria advisory
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. Delaware Lake is listed impaired under Clean Water Act §303(d) (IR 5) for metals (other than mercury), nutrients (phosphorus, nitrogen), pathogens (E. coli, fecal), pH / acidity, pCBs, temperature. Check local advisories before you swim.
Whether Delaware 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 Delaware Lake
These are the measurements NJDEP publishes for Delaware 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 1.6 ft of visibility. Phosphorus 156.5 µg/L. Chlorophyll-a 106.1 µg/L. TSI 74.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 1.6ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 157µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 106µg/L | Poor GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 74 | Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Very high nutrients, dense algae, poor clarity
Ask about Delaware Lake
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Lake Details
Surface area
38 acres
No bathymetric survey has been published for Delaware Lake, so its depth is not documented here.
Stays via Stay22
Stays near Delaware Lake
Compare lakeside cabins, hotels, and vacation rentals near Delaware Lake in Warren 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 Delaware Lake are listed below.
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Fishing Delaware Lake
Reservoir Info (USACE NID)
Delaware Lake is a man-made reservoir impounded by the Delaware Lake Dam, built primarily for recreation on the Delawanna Creek; earth-type dam, 21 ft tall and 515 ft long.
- Surface area
- 38 ac
- Normal storage
- 307 ac-ft
- Drainage area
- 2.6 sq mi
- Hazard class
- Low
- Owner
- Division of Fish & Wildlife
Source: USACE National Inventory of Dams, NID ID NJ00127 · Operator website
EPA Impairment Status
Delaware 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, Recreation.
Source: EPA ATTAINS assessment unit NJ02040105060020-01 · Official waterbody report
Nearby Lakes in Warren County
Frequently asked questions about Delaware Lake
Where is Delaware Lake?
- Delaware Lake is a lake in Warren County, New Jersey. Its water-quality measurements are published by NJDEP and shown on this page as reported.
What is the water quality of Delaware Lake?
- Delaware Lake in Warren County, New Jersey has water-quality measurements published by NJDEP, shown here as reported. Water clarity: 1.6 ft visibility. Phosphorus: 156.5 µg/L. Chlorophyll-a (algae): 106.1 µg/L. Surface area: 38 acres.
Is Delaware Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Delaware Lake is listed impaired under Clean Water Act §303(d) (IR 5) for metals (other than mercury), nutrients (phosphorus, nitrogen), pathogens (E. coli, fecal), pH / acidity, pCBs, temperature. Check local advisories before you swim.
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Where this data comes from
56 measurements from 2 monitoring stations, 2023–2024. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- NJDEP Bureau of Freshwater and Biological Monitoring
NJDEP_BFBM56 samples · 2023–2024
Analytical methods
- Phosphorus by Colorimetry
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
Monitoring station identifiers (2)
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