Canyon Lake is a 29-acre cold, clear oligotrophic lake in Pennington County, South Dakota. Water quality is graded A based on 1 sampling years through 2021.
Source: EPA Water Quality Portal sampling records, South Dakota DNR, last sampled 2021-06-09. Grade methodology: LakeGrade methodology.
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Swimming Safety
Based on E. coli testing, Canyon Lake frequently exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 14.3% of 7 samples across 3 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: A, Excellent
No clarity data. Chlorophyll-a: 1.3 µg/L. Trophic State Index: 33.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No data | |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 1.3 µg/L | A |
| Trophic State Index (TSI) | 33 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 29 acres |
Where to stay near Canyon Lake
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Fishing Canyon Lake
Location
County Ranking
Ranked #1 of 1 lakes in Pennington County
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Reservoir Info (USACE NID)
Canyon Lake is a man-made reservoir impounded by the Canyon Lake Dam (completed 1976), built primarily for irrigation on the RAPID CREEK; earth-type dam, 31 ft tall and 1,325 ft long.
- Surface area
- 29 ac
- Normal storage
- 140 ac-ft
- Max storage
- 610 ac-ft
- Drainage area
- 66 sq mi
- Hazard class
- High
- Owner
- CITY OF RAPID CITY
All listed purposes: Irrigation;Recreation;Water Supply.
Source: USACE National Inventory of Dams, NID ID SD02137 · Operator website
Regulated Pollution Sources Nearby
7 EPA-permitted facilities operate within about 5 miles of Canyon Lake under Clean Water Act (NPDES) discharge permits. 4 facilities have a reported Clean Water Act violation in the past three years.
- Sd Gfp - Cleghorn Fish HatcheryRapid City · 0.5 mi away · NPDES SD0000060Recent violation
- Gcc DacotahRapid City · 2.3 mi away · NPDES SD0000027Recent violation
- Pete Lien & Sons, IncRapid City · 4.1 mi away · NPDES SD0000094Recent violation
- Black Hills Corp LctfRapid City · 4.5 mi away · NPDES SD0027871Recent violation
- Sd Army National GuardRapid City · 1.9 mi away · NPDES SD0027332
- Black Hills Power, IncRapid City · 2.4 mi away · NPDES SD0000141
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
Data Sources
Water quality data from the EPA Water Quality Portal
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Grading methodology based on Metropolitan Council standards
Most recent sample: 2021-06-09
Monitoring stations: 1