Harrison County, Ohio · Water Quality Report Card
Tappan Lake @ Cadiz Public Water Supply Intake
Tappan Lake @ Cadiz Public Water Supply Intake in Harrison County, Ohio is not rated for water quality — its monitoring record does not meet the evidence bar. Phosphorus: 66.1 µg/L. Chlorophyll-a (algae): 72.1 µg/L.
- Mean depth
- ~30 ft est.
- Type
- Eutrophic
- Trend
- ↓ Declining
Tappan Lake @ Cadiz Public Water Supply Intake is a productive, nutrient-rich eutrophic lake in Harrison County, Ohio with an estimated average depth of about 30 feet. Overall water quality is declining over recent sampling years.
Source: EPA Water Quality Portal sampling records, Ohio EPA, last sampled 2022-08-22. Grade methodology: LakeGrade methodology.
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Swimming Safety
Not rated for swimming — there is not enough monitoring data to judge this lake
Water Quality Grade: Not rated
No clarity data. Phosphorus level: 66.1 µg/L. Chlorophyll-a: 72.1 µg/L. Trophic State Index: 69.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No data | |
| Phosphorus | 66.1 µg/L | |
| Chlorophyll-a (Algae) | 72.1 µg/L | |
| Trophic State Index (TSI) | 69 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Average Depth | ~30 ft est. |
Depth marked “est.” is a modeled estimate from HydroLAKES, not a measured survey. Ohio has not published bathymetry for Tappan Lake @ Cadiz Public Water Supply Intake.
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Fishing Tappan Lake @ Cadiz Public Water Supply Intake
Water Quality Trend: ↓ Declining
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -2.54 m/yr | 2 |
| Phosphorus | → Stable | +1.35 µg/L/yr | 2 |
Location
Nearby Lakes in Harrison County
Explore Tappan Lake @ Cadiz Public Water Supply Intake across LakeGrade
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More records, surveys & data sources
EPA Impairment Status
Tappan Lake @ Cadiz Public Water Supply Intake 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 (2.06 km)
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Where this data comes from
5 measurements from 1 monitoring station, 2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Division of Surface water (Ohio)
21OHIO_WQX5 samples · 2022
Analytical methods
- Total Phosphorus After Block Digestion
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
- 2130 B ~ Nephelometric Method
Monitoring station identifiers (1)
Grade thresholds come from the U.S. EPA National Lakes Assessment 2022 Technical Support Document (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated.
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion
Most recent sample: 2022-08-22
Monitoring stations: 1