Upper Big Sioux HUC8 10170201
A 4,230 km² sub-basin of the Missouri region in SD. Drought coverage is from the US Drought Monitor (map of 2026-09-01); streamflow classes place each USGS gauge's latest reading against its own day-of-year record.
Health score
75
Healthy
Drought index
74
Abnormally dry
Area in D2+
0%
0% exceptional (D4)
Gauges below normal
0%
of 4 reporting
Median flow
53%
p35 of record
Water assets
4,205
4 springs · 3,369 wells
USGS gauges (5)
- BIG SIOUX RIVER NEAR WATERTOWN, SD064794381 cfsp29 · normal
- BIG SIOUX RIVER AT WATERTOWN, SD064795001 cfsp31 · normal
- BIG SIOUX RIVER NEAR CASTLEWOOD, SD0647952517 cfsp38 · normal
- BIG SIOUX RIVER NEAR FLORENCE, SD064792154 cfsp83 · above normal
- BIG SIOUX RIVER BELOW WATERTOWN, SD0647952021 cfsno long-term record
Recent conditions
| Date | DSCI | D2+ % | Gauges low | Flow pct |
|---|---|---|---|---|
| 2026-09-07 | 74 | 0 | 0/4 | p35 |
Top water assets
- 76Alois Foxriver
- 76Leonard Sigdestadwell
- 76Watertown Municipal Utilitieslake
- 76Joseph P Amdahlwell
- 76David Mcelhanywell
- 76Sd State Cement Plantwell
- 76Florence M Sandersonwell
- 76Poinsett Httrn Brthwell
- 76Css Companywell
- 76Clifford Grinolswell