Cupsaw Lake
Passaic County, New Jersey69 acresView mapDirections
NJDEP publishes the water-quality measurements for Cupsaw Lake. Here is what has been measured.
- Impaired · Mercury
- Limited data
Cupsaw Lake in Passaic County, New Jersey has water-quality measurements published by NJDEP, shown here as reported. Water clarity: 4.3 ft visibility. Surface area: 69 acres.
Cupsaw Lake is a 69-acre lake in Passaic County, New Jersey.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2022-06-21. Methodology: how these readings are compared.
Swimming conditions
No readingBacteria advisory
Nutrient and algae readings are not a swimming clearance. Cupsaw Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, metals (other than mercury), pathogens (E. coli, fecal). Check local advisories before you swim.
Whether Cupsaw 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 Cupsaw Lake
These are the measurements NJDEP publishes for Cupsaw 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 4.3 ft. TSI 56.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 4.3ft | 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. | 56 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Cupsaw Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
69 acres
No bathymetric survey has been published for Cupsaw Lake, so its depth is not documented here.
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Fishing Cupsaw Lake
Reservoir Info (USACE NID)
Cupsaw Lake is a man-made reservoir impounded by the Cupsaw Lake Dam (completed 1930), built primarily for recreation on the Cupsaw Brook; earth-type dam, 35 ft tall and 430 ft long.
- Surface area
- 69 ac
- Normal storage
- 698 ac-ft
- Drainage area
- 4.2 sq mi
- Hazard class
- High
- Owner
- Cupsaw Lake Inprovement Association
Source: USACE National Inventory of Dams, NID ID NJ00194 · Operator website
EPA Impairment Status
Cupsaw 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, Fish consumption, Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit NJ02030103070050-01 · Official waterbody report
Nearby Lakes in Passaic County
Frequently asked questions about Cupsaw Lake
Where is Cupsaw Lake?
- Cupsaw 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 Cupsaw Lake?
- Cupsaw Lake in Passaic County, New Jersey has water-quality measurements published by NJDEP, shown here as reported. Water clarity: 4.3 ft visibility. Surface area: 69 acres.
Is Cupsaw Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Cupsaw Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, metals (other than mercury), pathogens (E. coli, fecal). Check local advisories before you swim.
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Where this data comes from
1 measurement from 1 monitoring station, 2022. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- North American Lake Management Society
NALMS1 sample · 2022
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