Grenloch Lake
Gloucester County, New Jersey21 acresView mapDirections
NJDEP publishes the water-quality measurements for Grenloch Lake. Here is what has been measured.
- Mesotrophic
- Impaired · Mercury
- Limited data
Grenloch Lake in Gloucester County, New Jersey has water-quality measurements published by NJDEP, shown here as reported. Water clarity: 4.8 ft visibility. Phosphorus: 30 µg/L. Chlorophyll-a (algae): 4.3 µg/L. Surface area: 21 acres.
Grenloch Lake is a 21-acre mesotrophic lake in Gloucester County, New Jersey. Compared to the 2 other monitored lakes in Gloucester County, Grenloch Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2024-10-31. 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. Grenloch Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, metals (other than mercury), nutrients (phosphorus, nitrogen), oxygen depletion (low DO), pathogens (E. coli, fecal). Check local advisories before you swim.
Whether Grenloch 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 Grenloch Lake
These are the measurements NJDEP publishes for Grenloch 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 4.8 ft. Phosphorus 30 µg/L. Chlorophyll-a 4.3 µg/L. TSI 51.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 4.8ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 30µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 4.3µg/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. | 51 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Grenloch Lake
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Lake Details
Surface area
21 acres
No bathymetric survey has been published for Grenloch Lake, so its depth is not documented here.
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Fishing Grenloch Lake
Reservoir Info (USACE NID)
Grenloch Lake is a man-made reservoir impounded by the Grenloch Lake Dam (completed 1907), built primarily for recreation on the South Branch Timber Creek; earth-type dam, 21 ft tall and 250 ft long.
- Surface area
- 21 ac
- Normal storage
- 92 ac-ft
- Max storage
- 272 ac-ft
- Drainage area
- 14.6 sq mi
- Hazard class
- Significant
- Owner
- Township of Washington
All listed purposes: Recreation;Water Supply.
Source: USACE National Inventory of Dams, NID ID NJ00402 · Operator website
EPA Impairment Status
Grenloch 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.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit NJ02040202120030-01 · Official waterbody report
Nearby Lakes in Gloucester County
Frequently asked questions about Grenloch Lake
Where is Grenloch Lake?
- Grenloch Lake is a lake in Gloucester County, New Jersey. Its water-quality measurements are published by NJDEP and shown on this page as reported.
What is the water quality of Grenloch Lake?
- Grenloch Lake in Gloucester County, New Jersey has water-quality measurements published by NJDEP, shown here as reported. Water clarity: 4.8 ft visibility. Phosphorus: 30 µg/L. Chlorophyll-a (algae): 4.3 µg/L. Surface area: 21 acres.
Is Grenloch Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Grenloch Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, metals (other than mercury), nutrients (phosphorus, nitrogen), oxygen depletion (low DO), pathogens (E. coli, fecal). Check local advisories before you swim.
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Where this data comes from
27 measurements from 2 monitoring stations, 2024. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- NJDEP Bureau of Freshwater and Biological Monitoring
NJDEP_BFBM27 samples · 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