USGS Streamgage 10263500
Big Rock C near Valyermo, CA
Big Rock C near Valyermo, CA is USGS streamgage 10263500 in California, monitoring river discharge in hydrologic subbasin 18090206. It drains a watershed of about 23 square miles. Discharge records at this site go back to 1923. Typical flow runs near 6.5 cfs in July and 15 cfs in April, with the higher of the two arriving in April.
Gauge details
- State
- California
- Drainage area
- 23 sq mi
- Gauge elevation
- 4,036 ft
- Subbasin (HUC-8)
- 18090206
- Coordinates
- 34.42083, -117.83951
- USGS site number
- 10263500
- Records begin
- 1923-02-01 (103 years)
Typical flow by month
Long-term daily discharge percentiles from the USGS record (up to 104 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 | 3 | 6.6 | 30.4 | |
| February | 3.7 | 10.3 | 58.9 | |
| March | 4.1 | 13.9 | 82.8 | |
| April | 4.6 | 15 | 77.3 | |
| May | 3.9 | 13.2 | 77.5 | |
| June | 2.7 | 9 | 46 | |
| July | 1.9 | 6.5 | 25.9 | |
| August | 1.7 | 5.3 | 16.9 | |
| September | 1.6 | 4.4 | 12.1 | |
| October | 1.5 | 4 | 9.7 | |
| November | 1.7 | 4.4 | 10.7 | |
| December | 2.3 | 5.1 | 16.4 |
All values in cubic feet per second (cfs).
Common questions
- When does Big Rock C near Valyermo, CA normally run highest?
- April, on the long-term record. The median daily flow that month is about 15 cfs, against 4 cfs in October, the lowest month. These are historical normals for the date, not a forecast and not today's reading.
- What is a normal flow for Big Rock C near Valyermo, CA?
- It depends on the month. In January, half of days historically fall near 6.6 cfs, with the middle 80% of days between 3 and 30.4 cfs. The month-by-month table on this page gives the full range.
- How long has Big Rock C near Valyermo, CA been measured?
- Discharge records at USGS site 10263500 begin in 1923, about 103 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 Big Rock C near Valyermo, CA?
- The gauge sits at 34.42083, -117.83951, in California, in hydrologic subbasin 18090206, at an elevation of about 4,036 feet, draining roughly 23 square miles.
- Can I use Big Rock C near Valyermo, CA 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.