Greenwood Lake
Passaic County, New Jersey1,733 acresView mapDirections
NJDEP publishes the water-quality measurements for Greenwood Lake. Here is what has been measured.
- Impaired · Mercury
- Limited data
Greenwood Lake in Passaic County, New Jersey has water-quality measurements published by NJDEP, shown here as reported. Water clarity: 2.1 ft visibility. Surface area: 1733 acres.
Greenwood Lake is a 1,733-acre lake in Passaic County, New Jersey.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2025-10-23. Methodology: how these readings are compared.
What Greenwood Lake is good for
From access and monitoring records, not editorial picks.
- Big water1,733 acres
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Greenwood Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, pH / acidity, temperature. Check local advisories before you swim.
Whether Greenwood 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 Greenwood Lake
These are the measurements NJDEP publishes for Greenwood 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 2.1 ft of visibility. TSI 66.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 2.1ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | No reading The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. | |
| 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. | 66 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Greenwood Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
1,733 acres
No bathymetric survey has been published for Greenwood Lake, so its depth is not documented here.
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Fishing Greenwood Lake
Reservoir Info (USACE NID)
Greenwood Lake is a man-made reservoir impounded by the Greenwood Lake Dam (completed 1928), built primarily for recreation on the Wanaque River; concrete-type dam, 17 ft tall and 270 ft long.
- Surface area
- 1,733 ac
- Normal storage
- 13,269 ac-ft
- Drainage area
- 27.1 sq mi
- Hazard class
- High
- Owner
- Division of Parks and Forestry
Source: USACE National Inventory of Dams, NID ID NJ00187 · Operator website
EPA Impairment Status
Greenwood 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, Fish consumption.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit NJ02030103070030-01 · Official waterbody report
Nearby Lakes in Passaic County
Frequently asked questions about Greenwood Lake
Where is Greenwood Lake?
- Greenwood Lake is a lake in Passaic County, New Jersey. Its water-quality measurements are published by NJDEP and shown on this page as reported.
What is the water quality of Greenwood Lake?
- Greenwood Lake in Passaic County, New Jersey has water-quality measurements published by NJDEP, shown here as reported. Water clarity: 2.1 ft visibility. Surface area: 1733 acres.
Is Greenwood Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Greenwood Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, pH / acidity, temperature. Check local advisories before you swim.
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Where this data comes from
9 measurements from 3 monitoring stations, 2025. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- Princeton Hydro LLC
PRINCETONHYDRO9 samples · 2025
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