USGS Streamgage 11098000
Arroyo Seco near Pasadena, CA
Arroyo Seco near Pasadena, CA is USGS streamgage 11098000 in California, monitoring river discharge in hydrologic subbasin 18070105. It drains a watershed of about 16 square miles. Discharge records at this site go back to 1910. Typical flow runs near 0.7 cfs in July and 5.6 cfs in April, with the higher of the two arriving in April. Rivermatics issues a daily machine-learned flow outlook for this gauge, reaching 14 days ahead.
View live conditions & forecast →
Gauge details
- State
- California
- Drainage area
- 16 sq mi
- Gauge elevation
- 1,400 ft
- Subbasin (HUC-8)
- 18070105
- Coordinates
- 34.22223, -118.17756
- USGS site number
- 11098000
- Records begin
- 1910-12-01 (116 years)
- Rivermatics forecast
- 14-day flow outlook
14-day flow forecast
Based on observations through for Arroyo Seco near Pasadena, CA. Each day carries a median estimate and the band the model expects the flow to fall within — not a single number to plan against. Forecasts are re-issued daily; see the live screen for the current outlook.
| Date | Low p10 | Expected p50 | High p90 | Range |
|---|---|---|---|---|
| 0.1 | 0.2 | 0.2 | ||
| 0.1 | 0.2 | 0.2 | ||
| 0.1 | 0.2 | 0.2 | ||
| 0.1 | 0.2 | 0.2 | ||
| 0.1 | 0.2 | 0.3 | ||
| 0.1 | 0.2 | 0.3 | ||
| 0.1 | 0.2 | 0.3 | ||
| 0.1 | 0.2 | 0.3 | ||
| 0.1 | 0.2 | 0.3 | ||
| 0.1 | 0.2 | 0.4 | ||
| 0 | 0.2 | 0.4 | ||
| 0 | 0.2 | 0.4 | ||
| 0 | 0.2 | 0.4 | ||
| 0 | 0.2 | 0.4 |
All values in cubic feet per second (cfs). Estimates only — do not use them for navigation or for any safety, rescue, or emergency decision.
Typical flow by month
Long-term daily discharge percentiles from the USGS record (up to 116 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 | 0.9 | 3.2 | 30.5 | |
| February | 1.3 | 6 | 64.6 | |
| March | 1.6 | 7 | 72.8 | |
| April | 1.3 | 5.6 | 32.3 | |
| May | 0.8 | 3.4 | 14.9 | |
| June | 0.4 | 1.7 | 8.6 | |
| July | 0.1 | 0.7 | 4.9 | |
| August | 0 | 0.4 | 2.9 | |
| September | 0 | 0.3 | 2.5 | |
| October | 0.1 | 0.5 | 2.7 | |
| November | 0.2 | 1 | 4 | |
| December | 0.5 | 1.8 | 14.2 |
All values in cubic feet per second (cfs).
Common questions
- When does Arroyo Seco near Pasadena, CA normally run highest?
- March, on the long-term record. The median daily flow that month is about 7 cfs, against 0.3 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 Arroyo Seco near Pasadena, CA?
- It depends on the month. In January, half of days historically fall near 3.2 cfs, with the middle 80% of days between 0.9 and 30.5 cfs. The month-by-month table on this page gives the full range.
- How long has Arroyo Seco near Pasadena, CA been measured?
- Discharge records at USGS site 11098000 begin in 1910, about 116 years, covering roughly 9,130 days of published daily values. The long record is what makes the monthly percentiles on this page meaningful.
- Is there a flow forecast for Arroyo Seco near Pasadena, CA?
- Yes. Rivermatics trains a machine-learned model — a temporal-fusion transformer — on this basin's observed flows, weather, and snowpack, and issues a daily flow outlook reaching 14 days ahead: a median estimate inside a confidence band, not a single number to bet on. Every forecast is scored against days the model never trained on, and that track record is published on the live gauge screen. Open live conditions to see the current outlook.
- Where is Arroyo Seco near Pasadena, CA?
- The gauge sits at 34.22223, -118.17756, in California, in hydrologic subbasin 18070105, at an elevation of about 1,400 feet, draining roughly 16 square miles.
- Can I use Arroyo Seco near Pasadena, 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.