Mercer County Lake Quality
New Jersey, 8 lakes, measured by NJDEP
Mercer County has 8 monitored lakes — a thin enough sample that one or two stressed lakes can move the county average noticeably. Use the per-lake pages below for what actually matters. 5 of those lakes carry recent nutrient and algae readings. The county-level summary describes that subset, not every water body listed. Most monitored lakes in Mercer County are productive, shallow basins; each lake page shows its own phosphorus and chlorophyll-a readings beside the EPA condition class.
The county's lakes lean shallow, which makes the readings sensitive to wind, sediment-resuspension, and any nutrient inputs from the watershed. The cleanest measured lake is Meadow Lakes.
Where to stay near Mercer County
Top-rated places to stay near Mercer County
Prices for Oct 9–11, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a trip to Mercer County?
Get lake water-quality updates plus the best cabin & lodging deals near Mercer County — straight to your inbox. No spam, unsubscribe anytime.
Quick Answers for Mercer County
Planning a trip? Check special fishing regulations for Meadow Lakes — or check the official New Jersey fishing regulations.
All Lakes in Mercer County
8 lakes · 5 ranked on readings, 3 without enough sampling5 lakes ranked on readings · 3 without enough sampling, hidden
| # | Lake | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|
| 1 | Meadow LakesMercer | 4.3 ft | 26.9 µg/L | 7.6 µg/L | No recent samples | Not recorded |
| 2 | Gropp LakeMercer | 3.3 ft | 35 µg/L | 25.8 µg/L | No recent samples | ✓ Public |
| 3 | Carnegie LakeMercer | 2.1 ft | 110.5 µg/L | 40.8 µg/L | No recent samples | Not recorded |
| 4 | Curlis LakeMercer | 2.4 ft | 121 µg/L | 49.8 µg/L | No recent samples | Not recorded |
| 5 | Etra LakeMercer | 3.9 ft | 46.6 µg/L | 35.4 µg/L | No recent samples | Not recorded |
| Grovers Mill PondMercer | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| Mercer County LakeMercer | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| Spring LakeMercer | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded |
NR = no nutrient or algae reading on record. The measurements are published as the authority reports them. Where the data comes from.
Lake Match
Which lake suits how you actually use one?
Six questions — swimming, fishing, quiet, cabins, drive time — and a shortlist of lakes that fit, with the water quality behind each one.
Other Counties in New Jersey
Browse every New Jersey lake, or the full directory of lakes across all United States (49 states), Canada (Ontario, Québec, Nova Scotia, British Columbia and Newfoundland and Labrador), and 38 other country hubs..
Source: the New Jersey Department of Environmental Protection. See data sources.