Lake Topanemus
Lake Topanemus in Monmouth County, New Jersey has a water quality grade of B (Good). Water clarity: 5.4 ft visibility. Phosphorus: 24.9 µg/L. Chlorophyll-a (algae): 10.2 µg/L. Surface area: 22 acres.
- Clarity
- 5.4 ft
- Area
- 22 acres
- Type
- Eutrophic
Lake Topanemus is a 22-acre productive, nutrient-rich eutrophic lake in Monmouth County, New Jersey. Water quality is graded B based on 2 sampling years through 2023. Compared to the 3 other monitored lakes in Monmouth County, Lake Topanemus ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2023-11-02. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLow algae
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Good for swimming, clear water with low algae levels
Water Quality Grade: B (Good)
Murky, only visible to about 5.4 ft. Phosphorus level: 24.9 µg/L. Chlorophyll-a: 10.2 µg/L. Trophic State Index: 52.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 5.4 ft | Not graded |
| Phosphorus | 24.9 µg/L | Good |
| Chlorophyll-a (Algae) | 10.2 µg/L | Good |
| Trophic State Index (TSI) | 52 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Lake Topanemus
Compare lakeside cabins, hotels, and vacation rentals near Lake Topanemus in Monmouth 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.
Top-rated places to stay near Lake Topanemus
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Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 22 acres |
No bathymetric survey has been published for Lake Topanemus, so its depth is not documented here.
Fishing Lake Topanemus
Reservoir Info (USACE NID)
Lake Topanemus is a man-made reservoir impounded by the Lake Topanemus Dam (completed 1915), built primarily for recreation on the McGellaird's Brook; earth-type dam, 20 ft tall and 327 ft long.
- Surface area
- 22 ac
- Normal storage
- 66 ac-ft
- Drainage area
- 1.6 sq mi
- Hazard class
- High
- Owner
- Monmouth County Engineering
Source: USACE National Inventory of Dams, NID ID NJ00219 · Operator website
EPA Impairment Status
Lake Topanemus is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit NJ02030105150020-01 · Official waterbody report · Matched by proximity (2.31 km)
County Ranking
Ranked #1 of 4 lakes in Monmouth County
Nearby Lakes in Monmouth County
Frequently asked questions about Lake Topanemus
Where is Lake Topanemus?
- Lake Topanemus is a lake in Monmouth County, New Jersey. LakeQuality grades it B for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Lake Topanemus?
- Lake Topanemus in Monmouth County, New Jersey has a water quality grade of B (Good). Water clarity: 5.4 ft visibility. Phosphorus: 24.9 µg/L. Chlorophyll-a (algae): 10.2 µg/L. Surface area: 22 acres.
Is Lake Topanemus safe to swim in?
- Good for swimming, clear water with low algae levels. Lake Topanemus has a water quality grade of B (Good). Algae concentration (chlorophyll-a) is 10.2 µg/L. Always check local health department advisories before swimming.
Explore Lake Topanemus across LakeGrade
More New Jersey Lake Rankings
Other Grade B Lakes in New Jersey
Eutrophic Lakes in New Jersey
Where this data comes from
72 measurements from 3 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_BFBM72 samples · 2022–2023
Analytical methods
- Phosphorus by Colorimetry
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
Monitoring station identifiers (3)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database