3 USGS Streamgages
Mad River flows and levels
Mad River is gauged at 3 USGS streamgages in California, each tracked by Rivermatics. The mainstem runs about 111 miles (179 km) from headwaters to outlet. Drainage area at the gauges ranges from 94 square miles at Mad River Ab Ruth Reservoir near Forest Glen, CA up to 485 at Mad River near Arcata, CA. The gauged reach falls about 2,655 feet, from 2,669 feet down to 14. Rivermatics issues a daily machine-learned 14-day flow outlook at 2 of them.
Gauges on this river, upstream to downstream
Ordered by drainage area, which is how far down the river each gauge sits. April and July figures are long-term median daily flows for that month from the USGS record — historical normals, not a forecast and not today's reading.
| Gauge | State | Drainage sq mi | Elevation ft | April p50 cfs | July p50 cfs | Forecast |
|---|---|---|---|---|---|---|
| Mad River Ab Ruth Reservoir near Forest Glen, CA | CA | 94 | 2,669 | 176.3 | 3.2 | 14-day |
| Mad River below Ruth Reservoir near Forest Glen, CA | CA | 121 | — | 255.7 | 47.9 | — |
| Mad River near Arcata, CA | CA | 485 | 14 | 1,287 | 61.3 | 14-day |
Typical flow by month at Mad River near Arcata, CA
The furthest-downstream gauge on this river, so the fullest flow it carries here. Long-term daily discharge percentiles from the USGS record (up to 64 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 | 282.3 | 1,960.3 | 8,613.9 | |
| February | 465.6 | 1,896.9 | 7,313.4 | |
| March | 524.2 | 2,031.6 | 6,251.3 | |
| April | 344.6 | 1,287 | 3,748 | |
| May | 150.2 | 475 | 1,543.2 | |
| June | 58.6 | 141.8 | 529.7 | |
| July | 26.6 | 61.3 | 113.4 | |
| August | 18.2 | 43.3 | 71.4 | |
| September | 21.9 | 43.4 | 88.3 | |
| October | 30.2 | 62.1 | 321.5 | |
| November | 53.6 | 302.6 | 2,896.2 | |
| December | 128.1 | 1,277.2 | 7,048.1 |
All values in cubic feet per second (cfs).
Common questions
- When does the Mad River run highest?
- March, on the long-term record at Mad River near Arcata, CA — the furthest-downstream gauge Rivermatics tracks on this river. Median daily flow there is about 2,031.6 cfs that month, against 43.3 cfs in August, the lowest. Upstream gauges peak on their own schedule; the table on this page gives April and July for each.
- How many gauges are on the Mad River?
- Rivermatics tracks 3 USGS streamgages on the Mad River, across California. Each has its own page with the site's full flow record and monthly normals. The river may carry other gauges that publish neither daily values nor discharge statistics; those are not tracked here.
- Is there a flow forecast for the Mad River?
- Yes, at 2 of the 3 gauges. Rivermatics trains a machine-learned model — a temporal-fusion transformer — on each basin's observed flows, weather and snowpack, and issues a daily 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 each gauge's live screen.
- Can I use Mad River 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.