USGS Streamgage 11087020
San Gabriel River Ab Whittier Narrows Dam, CA
San Gabriel River Ab Whittier Narrows Dam, CA is USGS streamgage 11087020 in California, monitoring river discharge in hydrologic subbasin 18070106. It drains a watershed of about 442 square miles. Discharge records at this site go back to 1955. Typical flow runs near 27.2 cfs in July and 58.2 cfs in April, with the higher of the two arriving in April.
Gauge details
- State
- California
- Drainage area
- 442 sq mi
- Gauge elevation
- 219 ft
- Subbasin (HUC-8)
- 18070106
- Coordinates
- 34.03418, -118.03812
- USGS site number
- 11087020
- 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 | 5.2 | 67.5 | 533.5 | |
| February | 3.7 | 72.6 | 988.4 | |
| March | 3.7 | 74.7 | 586.8 | |
| April | 1.8 | 58.2 | 262.7 | |
| May | 0 | 48.3 | 183.9 | |
| June | 0 | 30.7 | 160.6 | |
| July | 0 | 27.2 | 132.5 | |
| August | 0 | 26.5 | 147.4 | |
| September | 0 | 29.3 | 148.1 | |
| October | 0 | 42.1 | 178.6 | |
| November | 2.7 | 69.1 | 254.3 | |
| December | 6.8 | 73.8 | 318.6 |
All values in cubic feet per second (cfs).
Common questions
- When does San Gabriel River Ab Whittier Narrows Dam, CA normally run highest?
- March, on the long-term record. The median daily flow that month is about 74.7 cfs, against 26.5 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 San Gabriel River Ab Whittier Narrows Dam, CA?
- It depends on the month. In January, half of days historically fall near 67.5 cfs, with the middle 80% of days between 5.2 and 533.5 cfs. The month-by-month table on this page gives the full range.
- How long has San Gabriel River Ab Whittier Narrows Dam, CA been measured?
- Discharge records at USGS site 11087020 begin in 1955, about 71 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 San Gabriel River Ab Whittier Narrows Dam, CA?
- The gauge sits at 34.03418, -118.03812, in California, in hydrologic subbasin 18070106, at an elevation of about 219 feet, draining roughly 442 square miles.
- Can I use San Gabriel River Ab Whittier Narrows Dam, 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.