Local rivers peak this week

Recent warm weather has accelerated runoff and river flows in the Flathead Basin, but rivers have remained well below flood stage.

The National Weather Service showed the North Fork, Middle Fork and South Fork and main stem Flathead Rivers all cresting Thursday, with a projected drop in flows because of the arrival of lower temperatures.

But warm weather is expected to return next week, said Ray Nickless, a hydrologist with the National Weather Service in Missoula.

"We're melting out the [snow] pack pretty quick," Nickless said.

Snowpack above the Flathead Basin is now at 75 percent of the historic average for the beginning of May. Although the snowpack has been shrinking, enough potential runoff still exists for Flathead rivers to exceed this week's cresting flows.

The Flathead Basin river flows have potential to "surpass this week as we go through the rest of the runoff period," Nickless said. "You can have quite a few different crests through the hydrograph."

Although there was some rain, this week's flow increases were entirely because of snowmelt, Nickless said.

The Flathead River at Columbia Falls rose 4 feet during the week, peaking at the 10-foot mark on the river gauge, roughly 4 feet below flood stage. The North, Middle and South Forks had proportionately similar flow increases.

Nickless said continued snowmelt will have implications for river and stream flows this summer.

"We actually could use as much cooling as possible," he said. "It could be hard to sustain streamflows later in the summer if the runoff is too rapid."

Meanwhile, the U.S. Army Corps of Engineers on Thursday dropped releases from Libby Dam to 14,400 cfs, after weeks of running 25,000 cfs through the turbines. The higher releases were intended to make room in Lake Koocanusa for the peak spring runoff.

Mick Shea, Libby Dam project manager, said reservoir inflows have been about 20,000 cfs in recent days. Reducing flows Thursday was possible because the reservoir elevation is down to 2,386 feet, leaving roughly 73 vertical feet of storage.

That should be plenty of room to avoid what happened last spring, when a rapid runoff forced the Corps to release water over the dam's spillway for 19 days, violating Montana water-quality standards and causing flooding at Bonners Ferry, Idaho.

River information for the Flathead and Kootenai basins is available on the Internet through the Flathead Lakers Web site at http://www.flatheadlakers.org/.

Reporter Jim Mann may be reached at 758-4407 or by e-mail at jmann@dailyinterlake.com