USGS Streamgage 11136100
San Antonio C near Casmalia, CA
San Antonio C near Casmalia, CA is USGS streamgage 11136100 in California, monitoring river discharge in hydrologic subbasin 18060009. It drains a watershed of about 135 square miles. Discharge records at this site go back to 1955. Typical flow runs near 0.5 cfs in July and 1.8 cfs in April, with the higher of the two arriving in April.
Gauge details
- State
- California
- Drainage area
- 135 sq mi
- Gauge elevation
- 107 ft
- Subbasin (HUC-8)
- 18060009
- Coordinates
- 34.78219, -120.53012
- USGS site number
- 11136100
- Records begin
- 1955-10-01 (71 years)
Typical flow by month
Long-term daily discharge percentiles from the USGS record (up to 71 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 | 0.5 | 1.7 | 15.7 | |
| February | 0.6 | 2.6 | 52.4 | |
| March | 0.6 | 3.1 | 41.6 | |
| April | 0.5 | 1.8 | 7.9 | |
| May | 0.4 | 1.1 | 2.6 | |
| June | 0.3 | 0.7 | 1.7 | |
| July | 0.2 | 0.5 | 1.1 | |
| August | 0.3 | 0.5 | 1.2 | |
| September | 0.3 | 0.5 | 1.2 | |
| October | 0.2 | 0.5 | 1.5 | |
| November | 0.3 | 0.7 | 2.8 | |
| December | 0.4 | 1.1 | 4.3 |
All values in cubic feet per second (cfs).
Common questions
- When does San Antonio C near Casmalia, CA normally run highest?
- March, on the long-term record. The median daily flow that month is about 3.1 cfs, against 0.5 cfs in July, the lowest month. These are historical normals for the date, not a forecast and not today's reading.
- What is a normal flow for San Antonio C near Casmalia, CA?
- It depends on the month. In January, half of days historically fall near 1.7 cfs, with the middle 80% of days between 0.5 and 15.7 cfs. The month-by-month table on this page gives the full range.
- How long has San Antonio C near Casmalia, CA been measured?
- Discharge records at USGS site 11136100 begin in 1955, about 71 years, covering roughly 4,959 days of published daily values. The long record is what makes the monthly percentiles on this page meaningful.
- Where is San Antonio C near Casmalia, CA?
- The gauge sits at 34.78219, -120.53012, in California, in hydrologic subbasin 18060009, at an elevation of about 107 feet, draining roughly 135 square miles.
- Can I use San Antonio C near Casmalia, 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.