Tappan Lake is a 2,350-acre productive, nutrient-rich eutrophic lake in Harrison County, Ohio. Water quality is graded D based on 1 sampling years through 2020. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 1 other monitored lakes in Harrison County, Tappan Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Ohio DNR, last sampled 2020-12-01. Grade methodology: LakeGrade methodology.
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Swimming Safety
Swimming not recommended, poor water quality with high algae risk
Water Quality Grade: D, Poor
No clarity data. Phosphorus level: 77 µg/L. Trophic State Index: 67.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No data | |
| Phosphorus | 77 µg/L | D |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 67 | 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
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Fishing Tappan Lake
Water Quality Trend: ↓ Declining
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -2.54 m/yr | 2 |
Recreation & Access
Water Temperature
Tappan Lake averages about 79°F at the surface in summer, usually warmest in Jul (about 80°F) and coldest in Oct (about 63°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 274 field readings (2010–2022) via the EPA Water Quality Portal. See the full Tappan Lake water temperature breakdown →
Location
County Ranking
Ranked #1 of 2 lakes in Harrison County
Nearby Lakes in Harrison County
Explore Tappan Lake across LakeGrade
More Ohio Lake Rankings
Other Grade D 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 (2.08 km)
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
2 EPA-permitted facilities 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.
- Mcwc - Tappan Lake CampgroundDeersville · 1.1 mi away · NPDES OH0125121Recent violation
- Rosebud Mining Company-Stautner MineCadiz · 4.8 mi away · NPDES OH0145122
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: 2020-12-01
Monitoring stations: 1