Onway Lake-Seannikki
Onway Lake-Seannikki in Rockingham County, New Hampshire has a water quality grade of B (Good). Phosphorus: 10.6 µg/L.
- Type
- Oligotrophic
- Public access
- Yes
Onway Lake-Seannikki is a cold, clear oligotrophic lake in Rockingham County, New Hampshire. Water quality is graded B based on 1 sampling years through 2025. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 50 other monitored lakes in Rockingham County, Onway Lake-Seannikki ranks #10 for water quality.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2025-07-01. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLimited data
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)
No clarity data. Phosphorus level: 10.6 µg/L. Trophic State Index: 38.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 10.6 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 38 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Onway Lake-Seannikki
Compare lakeside cabins, hotels, and vacation rentals near Onway Lake-Seannikki in Rockingham County, New Hampshire — 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 Onway Lake-Seannikki
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Recreation & Access
- Onway LakePublic
Named access points from the USGS National Boat Ramps inventory, snapped within 5 km. More lakes with boat ramps
Fishing Onway Lake-Seannikki
EPA Impairment Status
Onway Lake-Seannikki is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit NHLAK600030703-03-01 · Official waterbody report · Matched by proximity (0.53 km)
County Ranking
Ranked #10 of 51 lakes in Rockingham County
Nearby Lakes in Rockingham County
Frequently asked questions about Onway Lake-Seannikki
Where is Onway Lake-Seannikki?
- Onway Lake-Seannikki is a lake in Rockingham County, New Hampshire. LakeQuality grades it B for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Onway Lake-Seannikki?
- Onway Lake-Seannikki in Rockingham County, New Hampshire has a water quality grade of B (Good). Phosphorus: 10.6 µg/L.
Is Onway Lake-Seannikki safe to swim in?
- Good for swimming, clear water with low algae levels. Onway Lake-Seannikki has a water quality grade of B (Good). Always check local health department advisories before swimming.
Are there boat ramps on Onway Lake-Seannikki?
- Onway Lake-Seannikki has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Onway Lake. Public access is listed as yes.
Explore Onway Lake-Seannikki across LakeGrade
More New Hampshire Lake Rankings
Top 25 by overall water quality score
Top 25 by Secchi water clarity
Grade A/B + low algae filter
Panfish-rich, public access
Full state directory
Other Grade B Lakes in New Hampshire
Oligotrophic Lakes in New Hampshire
Where this data comes from
5 measurements from 1 monitoring station, 2021–2025. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- New Hampshire Department Of Environmental Services (BEACH)
111133005 samples · 2021–2025
Analytical methods
- 10-115-01-1 F ~ LACHAT; Total Phosphorus- Manual persulfate digest
Monitoring station identifiers (1)
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
Named boat-access points from the USGS National Boat Ramps inventory