USGS Streamgage 12381400
South Fork Jocko River near Arlee, MT
South Fork Jocko River near Arlee, MT is USGS streamgage 12381400 in Montana, monitoring river discharge in hydrologic subbasin 17010212. It drains a watershed of about 58 square miles. Discharge records at this site go back to 1982. Typical flow runs near 77.9 cfs in July and 52.1 cfs in April, with the higher of the two arriving in July.
Gauge details
- State
- Montana
- Drainage area
- 58 sq mi
- Gauge elevation
- 3,970 ft
- Subbasin (HUC-8)
- 17010212
- Coordinates
- 47.19555, -113.85074
- USGS site number
- 12381400
- Records begin
- 1982-09-28 (44 years)
Typical flow by month
Long-term daily discharge percentiles from the USGS record (up to 43 years of data), averaged within each month. These describe the historical normal range — they are not a forecast and not today's reading.
| Month | Low p10 | Typical p50 | High p90 | Range |
|---|---|---|---|---|
| January | 5.9 | 11.5 | 20.5 | |
| February | 6.3 | 10.9 | 19 | |
| March | 8.8 | 14.5 | 33.5 | |
| April | 20.2 | 52.1 | 116.4 | |
| May | 100.6 | 197 | 372.9 | |
| June | 97.8 | 195.8 | 348.2 | |
| July | 44.4 | 77.9 | 117.2 | |
| August | 24.6 | 38.9 | 50.5 | |
| September | 18 | 25.8 | 34.7 | |
| October | 15.1 | 20.9 | 28.5 | |
| November | 12.2 | 18.3 | 27.3 | |
| December | 7.6 | 13.6 | 23.5 |
All values in cubic feet per second (cfs).