USGS Streamgage 11162630
Pilarcitos C A Half Moon Bay, CA
Pilarcitos C A Half Moon Bay, CA is USGS streamgage 11162630 in California, monitoring river discharge in hydrologic subbasin 18050006. It drains a watershed of about 27 square miles. Discharge records at this site go back to 1966. Typical flow runs near 1.6 cfs in July and 10.2 cfs in April, with the higher of the two arriving in April.
Gauge details
- State
- California
- Drainage area
- 27 sq mi
- Gauge elevation
- 34 ft
- Subbasin (HUC-8)
- 18050006
- Coordinates
- 37.46656, -122.4341
- USGS site number
- 11162630
- Records begin
- 1966-07-01 (60 years)
Typical flow by month
Long-term daily discharge percentiles from the USGS record (up to 60 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 | 1.8 | 11.6 | 121.5 | |
| February | 3.8 | 17.5 | 129.4 | |
| March | 2.9 | 18.3 | 112.3 | |
| April | 1.9 | 10.2 | 47.1 | |
| May | 0.8 | 4.5 | 17.7 | |
| June | 0.1 | 2.4 | 8.1 | |
| July | 0 | 1.6 | 4.4 | |
| August | 0 | 1.1 | 3.4 | |
| September | 0 | 0.7 | 3 | |
| October | 0 | 1.2 | 4.2 | |
| November | 0.2 | 2.3 | 10.1 | |
| December | 1 | 4.7 | 50.9 |
All values in cubic feet per second (cfs).
Common questions
- When does Pilarcitos C A Half Moon Bay, CA normally run highest?
- March, on the long-term record. The median daily flow that month is about 18.3 cfs, against 0.7 cfs in September, the lowest month. These are historical normals for the date, not a forecast and not today's reading.
- What is a normal flow for Pilarcitos C A Half Moon Bay, CA?
- It depends on the month. In January, half of days historically fall near 11.6 cfs, with the middle 80% of days between 1.8 and 121.5 cfs. The month-by-month table on this page gives the full range.
- How long has Pilarcitos C A Half Moon Bay, CA been measured?
- Discharge records at USGS site 11162630 begin in 1966, about 60 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 Pilarcitos C A Half Moon Bay, CA?
- The gauge sits at 37.46656, -122.4341, in California, in hydrologic subbasin 18050006, at an elevation of about 34 feet, draining roughly 27 square miles.
- Can I use Pilarcitos C A Half Moon Bay, 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.