USGS Streamgage 11525500
Trinity River A Lewiston, CA
Trinity River A Lewiston, CA is USGS streamgage 11525500 in California, monitoring river discharge in hydrologic subbasin 18010211. It drains a watershed of about 719 square miles. Discharge records at this site go back to 1860. Typical flow runs near 458 cfs in July and 377.7 cfs in April, with the higher of the two arriving in July. Rivermatics issues a daily machine-learned flow outlook for this gauge, reaching 14 days ahead, alongside daily high and low water-temperature forecasts.
View live conditions & forecast →
Gauge details
- State
- California
- Drainage area
- 719 sq mi
- Gauge elevation
- 1,822 ft
- Subbasin (HUC-8)
- 18010211
- Coordinates
- 40.72472, -122.80111
- USGS site number
- 11525500
- Records begin
- 1860-12-01 (166 years)
- Rivermatics forecast
- 14-day flow outlook + water temperature
14-day flow forecast
Based on observations through for Trinity River A Lewiston, 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 |
|---|---|---|---|---|
| 1,141 | 1,187 | 1,262 | ||
| 1,113 | 1,183 | 1,258 | ||
| 1,061 | 1,178 | 1,254 | ||
| 943 | 1,170 | 1,255 | ||
| 740 | 1,154 | 1,266 | ||
| 593 | 1,116 | 1,258 | ||
| 508 | 1,066 | 1,236 | ||
| 481 | 1,034 | 1,224 | ||
| 475 | 1,013 | 1,223 | ||
| 415 | 944 | 1,193 | ||
| 382 | 876 | 1,170 | ||
| 374 | 845 | 1,145 | ||
| 384 | 836 | 1,121 | ||
| 382 | 818 | 1,114 |
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 65 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 | 160.5 | 301.5 | 581.9 | |
| February | 159.3 | 304.9 | 1,313.3 | |
| March | 158.5 | 304.6 | 1,396.8 | |
| April | 158 | 377.7 | 2,384.1 | |
| May | 157 | 1,186.9 | 4,354.2 | |
| June | 153.9 | 638.6 | 2,480.7 | |
| July | 154.1 | 458 | 1,160 | |
| August | 153.4 | 449.6 | 709.9 | |
| September | 186.4 | 439.9 | 779.8 | |
| October | 221.7 | 335.3 | 401.5 | |
| November | 226.7 | 300 | 332.8 | |
| December | 161.9 | 298.3 | 365.7 |
All values in cubic feet per second (cfs).
Common questions
- When does Trinity River A Lewiston, CA normally run highest?
- May, on the long-term record. The median daily flow that month is about 1,186.9 cfs, against 298.3 cfs in December, the lowest month. These are historical normals for the date, not a forecast and not today's reading.
- What is a normal flow for Trinity River A Lewiston, CA?
- It depends on the month. In January, half of days historically fall near 301.5 cfs, with the middle 80% of days between 160.5 and 581.9 cfs. The month-by-month table on this page gives the full range.
- How long has Trinity River A Lewiston, CA been measured?
- Discharge records at USGS site 11525500 begin in 1860, about 166 years, covering roughly 9,131 days of published daily values. The long record is what makes the monthly percentiles on this page meaningful.
- Is there a flow forecast for Trinity River A Lewiston, 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. A companion model forecasts each day's water-temperature high and low. 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 Trinity River A Lewiston, CA?
- The gauge sits at 40.72472, -122.80111, in California, in hydrologic subbasin 18010211, at an elevation of about 1,822 feet, draining roughly 719 square miles.
- Can I use Trinity River A Lewiston, 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.