Allen County, Ohio · Water Quality Report Card
Ferguson Reservoir
Ferguson Reservoir in Allen County, Ohio has a water quality grade of C (Fair). Phosphorus: 131 µg/L. Chlorophyll-a (algae): 13.4 µg/L.
- Mean depth
- ~5 ft est.
- Type
- Eutrophic
Ferguson Reservoir is a productive, nutrient-rich eutrophic lake in Allen County, Ohio with an estimated average depth of about 5 feet. Water quality is graded C based on 2 sampling years through 2024. Compared to the 6 other monitored lakes in Allen County, Ferguson Reservoir ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, Ohio EPA, last sampled 2024-09-18. Grade methodology: LakeGrade methodology.
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Swimming Safety
Generally safe for swimming, moderate water quality
Water Quality Grade: C (Fair)
No clarity data. Phosphorus level: 131 µg/L. Chlorophyll-a: 13.4 µg/L. Trophic State Index: 65.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No data | |
| Phosphorus | 131 µg/L | Poor |
| Chlorophyll-a (Algae) | 13.4 µg/L | Good |
| Trophic State Index (TSI) | 65 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Average Depth | ~5 ft est. |
Depth marked “est.” is a modeled estimate from HydroLAKES, not a measured survey. Ohio has not published bathymetry for Ferguson Reservoir.
Where to stay near Ferguson Reservoir
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Fishing Ferguson Reservoir
Location
County Ranking
Ranked #3 of 7 lakes in Allen County
Nearby Lakes in Allen County
Explore Ferguson Reservoir across LakeGrade
More Ohio Lake Rankings
Other Grade C Lakes in Ohio
Eutrophic Lakes in Ohio
More records, surveys & data sources
EPA Impairment Status
Ferguson Reservoir 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 OH041000070306 · Official waterbody report · Matched by proximity (0.16 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
51 measurements from 1 monitoring station, 2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Division of Surface water (Ohio)
21OHIO_WQX51 samples · 2024
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: 2024-09-18
Monitoring stations: 1