Rivermatics

3 USGS Streamgages · Columbia River system

Long Tom River flows and levels

Long Tom River is gauged at 3 USGS streamgages in Oregon, each tracked by Rivermatics. The mainstem runs about 57 miles (92 km) from headwaters to outlet. It drains into the Columbia River system. Drainage area at the gauges ranges from 89 square miles at Long Tom River near Noti, OR up to 391 at Long Tom River at Monroe, OR. Rivermatics issues a daily machine-learned 14-day flow outlook for every one 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.

USGS streamgages on this river, ordered upstream to downstream
Gauge State Drainage sq mi Elevation ft April p50 cfs July p50 cfs Forecast
Long Tom River near Noti, OR OR 89 — 203.6 29 14-day + temp
Long Tom River near Alvadore, OR OR 252 — 53.2 45.3 14-day + temp
Long Tom River at Monroe, OR OR 391 — 263.3 42.2 14-day + temp

Typical flow by month at Long Tom River at Monroe, OR

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 105 years of data), averaged within each month. These describe the historical normal range — they are not a forecast and not today's reading.

Historical monthly discharge percentiles in cubic feet per second
Month Low p10 Typical p50 High p90 Range
January 341.5 1,539.7 4,529.7
February 188.9 936.3 4,101.4
March 171.8 480.5 2,548.7
April 119.9 263.3 1,344.9
May 71.3 164.5 513.1
June 42.1 74.1 192.5
July 26.8 42.2 64.3
August 19.8 37.9 76
September 17.8 46.9 443.2
October 23.6 664 1,276.7
November 59.9 571.7 2,048.7
December 160.1 971.8 3,993.9

All values in cubic feet per second (cfs).

Common questions

When does the Long Tom River run highest?
January, on the long-term record at Long Tom River at Monroe, OR — the furthest-downstream gauge Rivermatics tracks on this river. Median daily flow there is about 1,539.7 cfs that month, against 37.9 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 Long Tom River?
Rivermatics tracks 3 USGS streamgages on the Long Tom River, across Oregon. 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 Long Tom River?
Yes, at 3 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.
What river system is the Long Tom River part of?
The Long Tom River drains into the Columbia River system — it is a tributary somewhere in that chain, following the flowpath down to its terminal river. Rivermatics builds this from the USGS/geoconnex reference-mainstem network rather than from names.
Can I use Long Tom 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.

Other rivers in the Columbia River system

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