Denby Reservoir
Oglala Lakota County, South DakotaView mapDirections
No nutrient or algae sampling on record from SD DANR for this lake.
- Limited data
Denby Reservoir in Oglala Lakota County, South Dakota has water-quality measurements published by SD DANR, shown here as reported.
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. Methodology: how these readings are compared.
Swimming conditions
No readingBacteria tested: exceedances
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.
Whether Denby Reservoir is safe to swim in today is a call for the South Dakota Department of Agriculture and Natural Resources and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Denby Reservoir
These are the measurements SD DANR publishes for Denby Reservoir, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
No clarity data.
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Frequently asked questions about Denby Reservoir
Where is Denby Reservoir?
- Denby Reservoir is a lake in Oglala Lakota County, South Dakota. Its water-quality measurements are published by SD DANR and shown on this page as reported.
What is the water quality of Denby Reservoir?
- Denby Reservoir in Oglala Lakota County, South Dakota has water-quality measurements published by SD DANR, shown here as reported.
Is Denby Reservoir safe to swim in?
- 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. That is a historical summary of past bacteria testing, not a current reading and not a swimming clearance. Bacteria levels can spike quickly after heavy rain, so whether Denby Reservoir is safe to swim in today is a call for South Dakota's water agency and the county health department; check their current beach advisories before you swim.
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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)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.