Rivermatics

3 USGS Streamgages · Mississippi River system

Gallatin River flows and levels

Gallatin River is gauged at 3 USGS streamgages in Montana, each tracked by Rivermatics. The mainstem runs about 111 miles (179 km) from headwaters to outlet. It drains into the Mississippi River system. Drainage area at the gauges ranges from 538 square miles at Gallatin River above Deer Creek, near Big Sky, MT up to 1,789 at Gallatin River at Logan, MT. The gauged reach falls about 1,788 feet, from 5,880 feet down to 4,092. 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
Gallatin River above Deer Creek, near Big Sky, MT MT 538 5,880 319.3 703.2 14-day + temp
Gallatin River near Gallatin Gateway, MT MT 819 5,174 453.9 1,153 14-day
Gallatin River at Logan, MT MT 1,789 4,092 992.1 821.7 14-day + temp

Typical flow by month at Gallatin River at Logan, MT

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 133 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 504.7 676.3 843.6
February 509.7 670.6 869.1
March 575.2 731.6 1,020.1
April 636.5 992.1 1,509.7
May 901.3 1,973.9 3,773.2
June 1,033.3 2,805 5,298
July 271.9 821.7 1,987.8
August 255.9 421 740.4
September 341.4 564.6 940.8
October 503.4 711.1 1,062.6
November 592.8 802.2 1,050.3
December 564.8 725.7 919.5

All values in cubic feet per second (cfs).

Common questions

When does the Gallatin River run highest?
June, on the long-term record at Gallatin River at Logan, MT — the furthest-downstream gauge Rivermatics tracks on this river. Median daily flow there is about 2,805 cfs that month, against 421 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 Gallatin River?
Rivermatics tracks 3 USGS streamgages on the Gallatin River, across Montana. 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 Gallatin 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 Gallatin River part of?
The Gallatin River drains into the Mississippi 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 Gallatin 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 Mississippi River system

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