Tappan Lake is a 2,350-acre productive, nutrient-rich eutrophic lake in Harrison County, Ohio. Water quality is graded F based on 1 sampling years through 2021. Limited fish-species data available. Public access is available with 3 public boat landings. Compared to the 1 other monitored lakes in Harrison County, Tappan Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Ohio DNR, last sampled 2021-09-20. Grade methodology: LakeGrade methodology.
Watch Tappan Lake water quality
Subscribe for LakeQuality updates by email. No spam, unsubscribe anytime.
Tappan Lake Water Quality Report Card (2026)
A printable one-page report card for Tappan Lake: grade, clarity, phosphorus, algae, multi-year trend, depth, and fish — with sources.
Swimming Safety
Avoid swimming, very poor water quality, potential algae toxins
Water Quality Grade: F, Very Poor
Very murky, less than 1.8 ft of visibility. Trophic State Index: 68.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.8 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 68 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 2,350 acres |
| Public Access | Yes |
Where to stay near Tappan Lake
Compare lakeside cabins, hotels, and vacation rentals near Tappan Lake in Harrison 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 Tappan 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 Tappan Lake?
Get lake water-quality report cards plus the best cabin & lodging deals near Tappan Lake — straight to your inbox. No spam, unsubscribe anytime.
Planning a whole trip? See where to stay at Ohio’s top lakes →
Fishing Tappan Lake
Recreation & Access
Current Conditions
Latest reading Jul 6, 2026, 4:15 AM from USGS gauge 03128000. See live data ↗ — readings update every 15–60 minutes; this page refreshes on each build.
Water Temperature
Tappan Lake averages about 78°F at the surface in summer, usually warmest in Jun (about 78°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 13 field readings (2010–2022) via the EPA Water Quality Portal.
Location & Depth Map
Free interactive depth-contour map of Tappan Lake, reaching a maximum surveyed depth of 27 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Ohio DNR.
County Ranking
Ranked #2 of 2 lakes in Harrison County
Nearby Lakes in Harrison County
Explore Tappan Lake across LakeGrade
More Ohio Lake Rankings
Other Grade F Lakes in Ohio
Eutrophic Lakes in Ohio
More records, surveys & data sources
Reservoir Info (USACE NID)
Tappan Lake is a man-made reservoir impounded by the Tappan Dam (completed 1936), built primarily for flood risk reduction on the LITTLE STILLWATER CREEK; earth-type dam, 52 ft tall and 1,550 ft long.
- Surface area
- 2,350 ac
- Normal storage
- 35,100 ac-ft
- Max storage
- 61,600 ac-ft
- Drainage area
- 71 sq mi
- Hazard class
- High
- Owner
- USACE - Huntington District
All listed purposes: Flood Risk Reduction;Fish and Wildlife Pond;Recreation.
Source: USACE National Inventory of Dams, NID ID OH00010 · Operator website
EPA Impairment Status
Tappan Lake 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 OH050400011503 · Official waterbody report · Matched by proximity (2.69 km)
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Tappan Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Mwcd - Tappan Lake MarinaScio · 0.4 mi away · NPDES OH0149039Recent violation
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
Impairment status from EPA ATTAINS 303(d) database
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: 2021-09-20
Monitoring stations: 2