USGS Streamgage 11173575
Alameda C below Welch C near Sunol, CA
Alameda C below Welch C near Sunol, CA is USGS streamgage 11173575 in California, monitoring river discharge in hydrologic subbasin 18050004. It drains a watershed of about 149 square miles. Discharge records at this site go back to 1999. Typical flow runs near 1.6 cfs in July and 15.6 cfs in April, with the higher of the two arriving in April.
Gauge details
- State
- California
- Drainage area
- 149 sq mi
- Gauge elevation
- 303 ft
- Subbasin (HUC-8)
- 18050004
- Coordinates
- 37.54049, -121.85635
- USGS site number
- 11173575
- Records begin
- 1999-10-01 (27 years)
Typical flow by month
Long-term daily discharge percentiles from the USGS record (up to 27 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 | 1.6 | 16.1 | 341.5 | |
| February | 2.6 | 16.5 | 339.4 | |
| March | 2.6 | 20.7 | 480.2 | |
| April | 2.3 | 15.6 | 260.6 | |
| May | 1.5 | 9 | 64.5 | |
| June | 0.7 | 4.7 | 18.3 | |
| July | 0.2 | 1.6 | 14.1 | |
| August | 0.1 | 0.7 | 13 | |
| September | 0 | 0.5 | 13 | |
| October | 0.1 | 0.7 | 8.7 | |
| November | 0.4 | 1.1 | 6.8 | |
| December | 0.9 | 5.1 | 131 |
All values in cubic feet per second (cfs).
Common questions
- When does Alameda C below Welch C near Sunol, CA normally run highest?
- March, on the long-term record. The median daily flow that month is about 20.7 cfs, against 0.5 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 Alameda C below Welch C near Sunol, CA?
- It depends on the month. In January, half of days historically fall near 16.1 cfs, with the middle 80% of days between 1.6 and 341.5 cfs. The month-by-month table on this page gives the full range.
- How long has Alameda C below Welch C near Sunol, CA been measured?
- Discharge records at USGS site 11173575 begin in 1999, about 27 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 Alameda C below Welch C near Sunol, CA?
- The gauge sits at 37.54049, -121.85635, in California, in hydrologic subbasin 18050004, at an elevation of about 303 feet, draining roughly 149 square miles.
- Can I use Alameda C below Welch C near Sunol, 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.