USGS Streamgage 11480390
Mad River Ab Ruth Reservoir near Forest Glen, CA
Mad River Ab Ruth Reservoir near Forest Glen, CA is USGS streamgage 11480390 in California, monitoring river discharge in hydrologic subbasin 18010102. It drains a watershed of about 94 square miles. Discharge records at this site go back to 1980. Typical flow runs near 3.2 cfs in July and 176.3 cfs in April, with the higher of the two arriving in April.
Gauge details
- State
- California
- Drainage area
- 94 sq mi
- Gauge elevation
- 2,669 ft
- Subbasin (HUC-8)
- 18010102
- Coordinates
- 40.28428, -123.33527
- USGS site number
- 11480390
- Records begin
- 1980-06-20 (46 years)
Typical flow by month
Long-term daily discharge percentiles from the USGS record (up to 46 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 | 32.9 | 290.1 | 1,554.8 | |
| February | 54.9 | 312.4 | 1,507.5 | |
| March | 55.6 | 305.1 | 1,240.8 | |
| April | 39.7 | 176.3 | 680.8 | |
| May | 20.8 | 59.3 | 241.5 | |
| June | 5.8 | 18.3 | 86.5 | |
| July | 0.9 | 3.2 | 16.2 | |
| August | 0 | 0.4 | 2.8 | |
| September | 0 | 0 | 1.5 | |
| October | 0 | 0 | 28 | |
| November | 0 | 16.7 | 359.2 | |
| December | 9.7 | 139.7 | 1,506 |
All values in cubic feet per second (cfs).
Common questions
- When does Mad River Ab Ruth Reservoir near Forest Glen, CA normally run highest?
- February, on the long-term record. The median daily flow that month is about 312.4 cfs, against 0 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 Mad River Ab Ruth Reservoir near Forest Glen, CA?
- It depends on the month. In January, half of days historically fall near 290.1 cfs, with the middle 80% of days between 32.9 and 1,554.8 cfs. The month-by-month table on this page gives the full range.
- How long has Mad River Ab Ruth Reservoir near Forest Glen, CA been measured?
- Discharge records at USGS site 11480390 begin in 1980, about 46 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 Mad River Ab Ruth Reservoir near Forest Glen, CA?
- The gauge sits at 40.28428, -123.33527, in California, in hydrologic subbasin 18010102, at an elevation of about 2,669 feet, draining roughly 94 square miles.
- Can I use Mad River Ab Ruth Reservoir near Forest Glen, 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.