Seneca Lake is a productive, nutrient-rich eutrophic lake in Noble County, Ohio. Water quality is graded F based on 1 sampling years through 2021. Limited fish-species data available. Public access is available with 10 public boat landings.
Source: EPA Water Quality Portal sampling records, Ohio DNR, last sampled 2021-09-14. Grade methodology: LakeGrade methodology.
Watch Seneca Lake water quality
Subscribe for LakeQuality updates by email. No spam, unsubscribe anytime.
Swimming Safety
Avoid swimming, very poor water quality, potential algae toxins
Water Quality Grade: F, Very Poor
Very murky, less than 1.7 ft of visibility. Trophic State Index: 70.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.7 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 70 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Seneca Lake
Compare lakeside cabins, hotels, and vacation rentals near Seneca Lake in Noble County, Ohio — 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 Seneca Lake
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 Seneca Lake?
Get lake water-quality report cards plus the best cabin & lodging deals near Seneca Lake — straight to your inbox. No spam, unsubscribe anytime.
Planning a whole trip? See where to stay at Ohio’s top lakes →
Fishing Seneca Lake
Recreation & Access
Current Conditions
Latest reading Jul 6, 2026, 4:15 AM from USGS gauge 03141000. See live data ↗ — readings update every 15–60 minutes; this page refreshes on each build.
Water Temperature
Seneca Lake averages about 79°F at the surface in summer, usually warmest in Jul (about 82°F) and coldest in May (about 71°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 182 field readings (2012–2021) via the EPA Water Quality Portal. See the full Seneca Lake water temperature breakdown →
Location
County Ranking
Ranked #1 of 1 lakes in Noble County
Nearby Lakes in Noble County
Explore Seneca Lake across LakeGrade
More Ohio Lake Rankings
Other Grade F Lakes in Ohio
Eutrophic Lakes in Ohio
More records, surveys & data sources
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
6 EPA-permitted facilities operate within about 5 miles of Seneca Lake under Clean Water Act (NPDES) discharge permits. 5 facilities have a reported Clean Water Act violation in the past three years.
- Lashley Addition WwtpCaldwell · 0.8 mi away · NPDES OH0144860Recent violation
- Buffalo Hills Campground StpSenecaville · 1.8 mi away · NPDES OH0135186Recent violation
- Senecaville WwtpSenecaville · 2.8 mi away · NPDES OH0041548Recent violation
- Lake Seneca Resorts AssocSenecaville · 2.9 mi away · NPDES OH0076414Recent violation
- Antrim Mennonite Activity CenterGuernsey · 3.7 mi away · NPDES OH0091375Recent violation
- Seneca Lake Camp AreaSenecaville · 3.7 mi away · NPDES OH0059102
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
Data Sources
Water quality data from the EPA Water Quality Portal
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Public boat-access points from the USGS National Boat Ramps inventory
Most recent sample: 2021-09-14
Monitoring stations: 3