Oglala Lakota County, South Dakota · Water Quality Report Card
Denby Reservoir
Denby Reservoir in Oglala Lakota County, South Dakota is not rated for water quality — its monitoring record does not meet the evidence bar.
Denby Reservoir is a lake in Oglala Lakota County, South Dakota.
Source: EPA Water Quality Portal sampling records, SD DANR, last sampled 2024-10-09. Grade methodology: LakeGrade methodology.
Watch Denby Reservoir water quality
Subscribe for LakeQuality updates by email. No spam, unsubscribe anytime.
Swimming Safety
Based on E. coli testing, Denby Reservoir occasionally exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 6.3% of 32 samples across 6 seasons.
This is a historical summary of past testing, not a current condition — bacteria levels change quickly, especially after rain. Always check South Dakota’s current beach and health-department advisories before swimming.
Water Quality Grade: Not rated
No clarity data.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No data | |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data |
Where to stay near Denby Reservoir
Compare lakeside cabins, hotels, and vacation rentals near Denby Reservoir in Oglala Lakota County, South Dakota — 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 Denby Reservoir
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 Denby Reservoir?
Get lake water-quality report cards plus the best cabin & lodging deals near Denby Reservoir — straight to your inbox. No spam, unsubscribe anytime.
Fishing Denby Reservoir
Location
Nearby Lakes in Oglala Lakota County
Explore Denby Reservoir across LakeGrade
More South Dakota Lake Rankings
Other Lakes in South Dakota
More records, surveys & data sources
Where this data comes from
18 measurements from 1 monitoring station, 2023–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Oglala Sioux Tribe (South Dakota) (Tribal)
OGLALAST18 samples · 2023–2024
Analytical methods
- Turbidity by Nephelometry
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
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion
Most recent sample: 2024-10-09
Monitoring stations: 1