Voice of the River

Average Snowpack and Early Runoff Leaves Gallatin River Streamflow Below Normal

The Gallatin River Watershed received near average precipitation this winter, but an unseasonably warm, dry April lead to early runoff and low summer flows.

Skiers and snowboarders enjoyed plentiful powder days in December 2015 and March 2016. Persistent warm, dry conditions in April and May melted snow two to three weeks before the historic average. Early runoff meant whitewater enthusiasts were on the river well ahead of schedule, but streamflow in the Gallatin has been below average and declining since the last week of May.



Snow Water Equivalent (SWE) measured at the Lone Mountain SNOTEL (black) peaked near average (green), but melted two to three weeks ahead of schedule. Data provided by NRCS National Water and Climate Center.


According to Jeff Dunn, watershed hydrologist and whitewater enthusiast, boaters enjoyed peak flows and an early paddling season, with high water quickly petering out: “Kayakers reveled in a solid week of prime whitewater flows between 3,000 and 4,000 cfs in early June that provided great big wave surfing and high water runs through House Rock rapid, followed by rapidly dropping flows that ended the whitewater season early.”

In the absence of the rain, river volume has declined throughout the summer. According to monthly average streamflow from the USGS WaterWatch, the Gallatin River is currently 62% of historic average volume for this time of year. The Surface Water Supply Index indicates that the Gallatin is one of several watersheds state-wide that has been classified as “extremely dry”.


Montana Surface Water Supply Index demonstrates extremely dry conditions for the Gallatin River when compared to the average year. Data provided by Montana Data Collections Office.

Montana Surface Water Supply Index demonstrates extremely dry conditions for the Gallatin River when compared to the average year. Data provided by Montana Data Collections Office.


Conditions in the Gallatin Watershed reflect a dry year state-wide. Lt. Governor Mike Cooney, Chair of the Governor’s Drought and Water Supply Advisory Committee (DWSAC) issued a “Drought Alert” for Glacier, Pondera, Teton, and Lewis & Clark Counties, where all users were encouraged to conserve water resources.



The US Drought Monitor for Montana shows abnormally dry conditions for the Gallatin Watershed. The Drought Monitor utilizes soil moisture, surface water supply, reservoir levels, snowpack, and local impacts to map drought severity nationwide. The U.S. Drought Monitor is produced through a partnership between the National Drought Mitigation Center at the University of Nebraska-Lincoln, the United States Department of Agriculture, and the National Oceanic and Atmospheric Administration.


Low water levels and hot weather have increased water temperatures throughout the state. Montana Fish Wildlife & Parks has declared Hoot Owl restrictions on local rivers, like the East Gallatin, Lower Gallatin, and Lower Madison.

The Upper Gallatin River has avoided fishing closures so far this year. According to the Task Force continuous monitoring station, the West Fork of the Gallatin River was as warm as 19.22 ◦C at 5:30 PM on August 13, 2016 this past week. This exceeds the 10.3 – 17 ◦C water temperatures preferred by Westslope Cutthroat Trout.

To date, the fire season has been relatively mild with recent rains providing a much needed reprieve to hot, dry weather.

Experts agree that the El Niño cycle of the past few years is over and has been one of the strongest since 1950. The anticipated La Niña cycle could bring cooler temperatures and rain in September.

Learn more: Upper Missouri River Basin Water Supply Report


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