Carnegie Lake
Mercer County, New Jersey245 acresView mapDirections
NJDEP publishes the water-quality measurements for Carnegie Lake. Here is what has been measured.
- Hypereutrophic
- Impaired · Impaired biota (cause unknown)
Carnegie Lake in Mercer County, New Jersey has water-quality measurements published by NJDEP, shown here as reported. Water clarity: 2.1 ft visibility. Phosphorus: 110.5 µg/L. Chlorophyll-a (algae): 40.8 µg/L. Surface area: 245 acres.
Carnegie Lake is a 245-acre highly nutrient-loaded hypereutrophic lake in Mercer County, New Jersey. Compared to the 14 other monitored lakes in Mercer County, Carnegie Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2023-09-26. 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. Carnegie Lake is listed impaired under Clean Water Act §303(d) (IR 5) for impaired biota (cause unknown), mercury, metals (other than mercury), nutrients (phosphorus, nitrogen), pathogens (E. coli, fecal), pesticides, pH / acidity, pCBs. Check local advisories before you swim.
Whether Carnegie 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 Carnegie Lake
These are the measurements NJDEP publishes for Carnegie 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. Phosphorus 110.5 µg/L. Chlorophyll-a 40.8 µg/L. TSI 69.
| 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 | 111µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 40.8µg/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. | 69 | Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Very high nutrients, dense algae, poor clarity
Ask about Carnegie Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
245 acres
No bathymetric survey has been published for Carnegie Lake, so its depth is not documented here.
Stays via Stay22
Stays near Carnegie Lake
Compare lakeside cabins, hotels, and vacation rentals near Carnegie Lake in Mercer 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 Carnegie Lake are listed below.
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Fishing Carnegie Lake
Reservoir Info (USACE NID)
Carnegie Lake is a man-made reservoir impounded by the Carnegie Lake Dam (completed 1900), built primarily for recreation on the Millstone River; concrete-type dam, 28 ft tall and 724 ft long.
- Surface area
- 245 ac
- Normal storage
- 1,344 ac-ft
- Max storage
- 5,326 ac-ft
- Drainage area
- 159.1 sq mi
- Hazard class
- Significant
- Owner
- Princeton University
Source: USACE National Inventory of Dams, NID ID NJ00150 · Operator website
EPA Impairment Status
Carnegie 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 NJ02030105110020-01 · Official waterbody report
Nearby Lakes in Mercer County
Frequently asked questions about Carnegie Lake
Where is Carnegie Lake?
- Carnegie Lake is a lake in Mercer County, New Jersey. Its water-quality measurements are published by NJDEP and shown on this page as reported.
What is the water quality of Carnegie Lake?
- Carnegie Lake in Mercer County, New Jersey has water-quality measurements published by NJDEP, shown here as reported. Water clarity: 2.1 ft visibility. Phosphorus: 110.5 µg/L. Chlorophyll-a (algae): 40.8 µg/L. Surface area: 245 acres.
Is Carnegie Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Carnegie Lake is listed impaired under Clean Water Act §303(d) (IR 5) for impaired biota (cause unknown), mercury, metals (other than mercury), nutrients (phosphorus, nitrogen), pathogens (E. coli, fecal), pesticides, pH / acidity, pCBs. Check local advisories before you swim.
Explore Carnegie Lake across LakeQuality
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Where this data comes from
116 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_BFBM116 samples · 2022–2023
Analytical methods
- Phosphorus by Colorimetry
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
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