Gallatin River at Big Sky
Montana · Paddling & whitewater
Measured at USGS 06043500 — Gallatin River near Gallatin Gateway, MT · NWS forecast point GLGM8
Reading taken Jul 28, 11:00 PM UTC
On the low side — bony, but runnable in a plastic boat
At 577 CFS, this gauge is running 79% of normal for late July — below the 733 CFS median USGS has recorded for this date across 96 years of record (1889–2026).
Data-derived guidance from USGS and NWS published values — not official advice, and not a safety assessment.
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Flood stages at Big Sky
Official National Weather Service categories for gauge GLGM8, issued by WFO TFX. Impact statements are the NWS's own wording for this location, reproduced verbatim.
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Major flood 7.5 ft · 11,200 CFS
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Moderate flood 7.0 ft · 9,726 CFS
- 7.0 ft Minor roads in gallatin gateway covered with water.
- 7.1 ft Water flows over road connecting two bridges over gallatin river. Three forest service campgrounds flood, including the one at squaw creek.
- 7.2 ft Small bridge near gallatin gateway and a few homes west of town are beginning to flood.
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Minor flood 6.0 ft · 6,886 CFS
- 6.0 ft Water flows over roads as well as several smalller bridges. Several forest service campgrounds as well as some home west of town begin to flood.
- 6.1 ft Flooding of the lowlands along the gallatin river.
- 6.3 ft Water flows over the axtell and irwin bridges.
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Action 5.0 ft · 4,846 CFS
- 5.0 ft Gallatin river on west side of gallatin gateway can come out of banks at mill road near where the road crosses the river. Water may work into area yards and fields, and may encroach onto mill road.
- Right now 1.76 ft
12 months of flow at Big Sky
Daily values from USGS gauge 06043500. Provisional data, subject to revision.
Highest crests on record at Big Sky
| Stage | Flow | Date |
|---|---|---|
| 7.38 ft | 9,100 CFS | Jun 17, 1974 |
| 6.71 ft | 9,160 CFS | Jun 2, 1997 |
| 6.70 ft | 8,980 CFS | Jun 13, 2022 |
| 6.51 ft | 8,410 CFS | Jun 30, 2011 |
| 6.50 ft | 7,640 CFS | Jun 6, 1991 |
| 6.49 ft | 7,610 CFS | Jun 27, 1971 |
| 6.48 ft | 7,600 CFS | Jun 9, 1970 |
| 6.31 ft | 7,330 CFS | Jun 6, 1995 |
| 6.27 ft | 7,950 CFS | Jul 4, 1975 |
| 6.23 ft | 7,230 CFS | Jun 15, 1959 |
Historical crests published by the National Weather Service for this gauge.
About Gallatin River at Big Sky
This gauge measures Gallatin River at Big Sky, Montana — the reading paddlers, anglers and outfitters on this stretch check before committing to a shuttle.
Gallatin Canyon and the Mad Mile.
Raw CFS means little on its own, so every reading on this page is shown against the USGS median for the same calendar day — 733 CFS for late July, from 96 years of record.
Because the National Weather Service also operates a forecast point here, the page carries the official flood-category ladder and the NWS's own stage-by-stage impact statements.
Gallatin River at Big Sky — common questions
What is the current flow on Gallatin River at Big Sky?
As of the last reading on this page, Gallatin River at Big Sky was running 577 CFS at a gage height of 1.76 ft, or 79% of the USGS median for this date. The number updates automatically from USGS gauge 06043500, which reports every 15 to 60 minutes.
Is that high or low for this time of year?
The USGS median flow for late July at this gauge is 733 CFS, calculated from 96 years of record (1889–2026). Comparing today's reading against that median is the only way a raw CFS number tells you anything — 200 CFS is a drought on one river and a flood on another.
How often does this reading update?
USGS transmits from this gauge every 15 to 60 minutes. This page bakes in the most recent reading when it is rebuilt, then refreshes live from USGS when you open it. Readings are provisional and subject to revision by USGS.
What is a runnable level on this stretch?
riverlvl deliberately does not publish a runnable range. American Whitewater and the local paddling community maintain the correlations for this reach, and they are the authority. This page gives you the raw inputs — current CFS, gage height, the seasonal median, and the 12-month hydrograph — so you can apply whatever range you trust.
How fast can this gauge come up?
This is a free-flowing gauge, so it rises with rain in the basin. The 12-month chart on this page shows the shape of the past year's rises, which is the best available guide to how flashy this particular reach is.
Where does this data come from?
The flow and gage height come from USGS gauge 06043500, public-domain data from the U.S. Geological Survey. The flood categories, impact statements and forecast come from the National Weather Service's National Water Prediction Service, gauge GLGM8.