Gallatin River Snowpack

Houndstonge, an invasive weed, grows along the Gallatin River on Wednesday, June 6, 2018, in Gallatin Gateway. The latest snowpack report shows that winter snowpack is dwindling early.

The month of May took a hard turn toward summer, sending much of the year’s stockpile of snow into rivers in a hurry.

The latest Natural Resources Conservation Service Water Supply Outlook Report showed that the enormous winter snowpack is dwindling early, as the year’s consistently high snowpack levels are now closer to average across southwestern Montana. Parts of the Gallatin, Madison and upper Yellowstone river basins were even recorded slightly below average — a significant change following months of bawdy snow levels.

Lucas Zukiewicz, a water supply specialist with the NRCS, said that’s all a result of the abundant sunshine and warm temperatures that came in May, which turned hillsides green and left white only at the highest elevations.

“The big story is just how early we’re seeing rivers make their big push this year,” Zukiewicz said.

The early arrival of the big push shattered records for monthly streamflow totals. According to NRCS data, the Gallatin River’s gauge at Logan saw roughly 304,000 acre feet of water pass through during May — more than double the average total for the month.

Numbers were equally staggering on other streams, including the upper Yellowstone. The stream gauge at Livingston recorded a total of more than 1.1 million acre feet for the month. The average is 450,000 acre feet.

That surge brought early peak flows for multiple rivers in the area. Zukiewicz said he believes the Gallatin River peaked on June 1. He added that the Yellowstone could still go higher, but that its peak is probably not far away.

Peaks usually come in June, Zukiewicz said, so that could pose a problem for late summer flows if the dry and hot persists.

“What we need is normal at this point,” Zukiewicz said. “We need normal precipitation and cooler temperatures.”

The entire Gallatin River basin was listed at 98 percent of its normal snowpack for June 1. Snow is still holding in the Hyalite basin, which was recorded at 125 percent of normal. The Gallatin’s overall total was brought down by the other two sub-basins: the upper Gallatin, at 86 percent of normal, and the Bridger Range, at 87 percent of normal.

Numbers are similar in the Madison River basin, which was recorded at 98 percent of normal. Totals are highest above Hebgen Lake, where snowpack is still listed at 129 percent of normal. Below Hebgen, snowpack was at 86 percent of normal.

Parts of the upper Yellowstone River basin are drying out. The mountains that drained the Shields River were listed at 30 percent of normal.

And yet, there’s still a bunch of snow in parts of the basin. Above Livingston, the snowpack was reported at 127 percent of normal. The Clark’s Fork of the Yellowstone is also sitting on a bunch of snow — listed at 155 percent of normal.

Michael Wright can be reached at mwright@dailychronicle.com or at 582-2638. Follow him on Twitter @mj_wright1.

Michael Wright covers the environment and wildlife issues for the Chronicle.

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