Custer County, Oklahoma · Water Quality Report Card
Foss Reservoir
Foss Reservoir in Custer County, Oklahoma is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 3.9 ft visibility.
- Clarity
- 3.9 ft
- Mean depth
- ~27 ft est.
- Type
- Eutrophic
- Trend
- ↓ Declining
Foss Reservoir is a productive, nutrient-rich eutrophic lake in Custer County, Oklahoma with an estimated average depth of about 27 feet. Overall water quality is declining over recent sampling years.
Source: EPA Water Quality Portal sampling records, ODEQ, last sampled 2024-10-07. 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
Murky, only visible to about 3.9 ft. Trophic State Index: 57.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.9 ft | |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 57 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Average Depth | ~27 ft est. |
Depth marked “est.” is a modeled estimate from HydroLAKES, not a measured survey. Oklahoma has not published bathymetry for Foss Reservoir.
Where to stay near Foss Reservoir
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Fishing Foss Reservoir
Water Quality Trend: ↓ Declining
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -6.5 m/yr | 2 |
Location
Nearby Lakes in Custer County
Explore Foss Reservoir across LakeGrade
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Other Lakes in Oklahoma
Eutrophic Lakes in Oklahoma
More records, surveys & data sources
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
68 measurements from 5 monitoring stations, 2016–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- OWRB Lakes Monitoring
OKWRB-LAKES_WQX68 samples · 2016–2024
Analytical methods
- OWRB Lakes Field Data Collection
- Determination of Turbidity
Monitoring station identifiers (5)
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
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: 2024-10-07
Monitoring stations: 5