USGS Streamgage 11502500
Williamson River below Sprague River near Chiloquin, OR
Williamson River below Sprague River near Chiloquin, OR is USGS streamgage 11502500 in Oregon, monitoring river discharge in hydrologic subbasin 18010201. It drains a watershed of about 3,030 square miles. Discharge records at this site go back to 1917. Typical flow runs near 543.5 cfs in July and 1,598 cfs in April, with the higher of the two arriving in April.
Gauge details
- State
- Oregon
- Drainage area
- 3,030 sq mi
- Gauge elevation
- 4,149 ft
- Subbasin (HUC-8)
- 18010201
- Coordinates
- 42.56437, -121.87971
- USGS site number
- 11502500
- Records begin
- 1917-04-27 (109 years)
Typical flow by month
Long-term daily discharge percentiles from the USGS record (up to 108 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 | 577.3 | 782.5 | 1,511 | |
| February | 599.7 | 943.7 | 2,017.2 | |
| March | 724.6 | 1,281.9 | 2,684.5 | |
| April | 781.2 | 1,598 | 3,269.3 | |
| May | 624 | 1,381.3 | 2,903.5 | |
| June | 500.4 | 810 | 1,693.7 | |
| July | 428 | 543.5 | 813.6 | |
| August | 407.5 | 505.4 | 633.3 | |
| September | 444.6 | 530 | 665.9 | |
| October | 518.5 | 593.8 | 789.2 | |
| November | 555.4 | 655.5 | 983.6 | |
| December | 565.9 | 737 | 1,333.5 |
All values in cubic feet per second (cfs).
Common questions
- When does Williamson River below Sprague River near Chiloquin, OR normally run highest?
- April, on the long-term record. The median daily flow that month is about 1,598 cfs, against 505.4 cfs in August, the lowest month. These are historical normals for the date, not a forecast and not today's reading.
- What is a normal flow for Williamson River below Sprague River near Chiloquin, OR?
- It depends on the month. In January, half of days historically fall near 782.5 cfs, with the middle 80% of days between 577.3 and 1,511 cfs. The month-by-month table on this page gives the full range.
- How long has Williamson River below Sprague River near Chiloquin, OR been measured?
- Discharge records at USGS site 11502500 begin in 1917, about 109 years, covering roughly 9,126 days of published daily values. The long record is what makes the monthly percentiles on this page meaningful.
- Where is Williamson River below Sprague River near Chiloquin, OR?
- The gauge sits at 42.56437, -121.87971, in Oregon, in hydrologic subbasin 18010201, at an elevation of about 4,149 feet, draining roughly 3,030 square miles.
- Can I use Williamson River below Sprague River near Chiloquin, OR data for flood or safety decisions?
- No. Rivermatics provides estimates, not guarantees, and the readings and forecasts here may be delayed, inaccurate, or wrong. Do not use them for navigation or for any safety, rescue, or emergency decision. Check the National Weather Service and USGS directly, and use your own judgment.