Summer to bring drought, low rivers for most of Montana
Laura Lundquist
(Missoula Current) As we head into summer, much of Montana is also heading into deepening drought, so certain streams, including the Clark Fork and Blackfoot rivers, are already running low and will continue to drop.
When it comes to the spring runoff, Montana has a glass-half-full scenario, Aaron Fiaschetti of the U.S. Geological Survey told the Montana Drought and Water Supply Advisory Committee on Wednesday morning. But the glass won't stay that way.
River flows in the south-central portion of the state - the Yellowstone, Tongue and Musselshell rivers - are normal to above normal. But the streams along the Rocky Mountain Front - the Dearborn, Sun and Marias rivers - and parts of western Montana, notably the Clark Fork River, are already running below normal to much below normal.
The low flows along the Rocky Mountain Front means some reservoirs weren’t able to fill before irrigation withdrawals started, said Clayton Jordan of the Bureau of Reclamation. For example, this year, Gibson Reservoir on the Front west of Augusta was far below average during the winter and peaked at about 20 feet below full. This will be the second year the reservoir didn’t fill.
“You have to go back to the 1940s to find back-to-back years and maybe the only other time that Gibson Reservoir hasn’t filled in back-to-back years,” Jordan said. “We will continue to draw down, so irrigation water supply is being impacted. The allotments for both Greenfields and Fort Shaw (irrigation districts) are about half of what they would be.”
That’s concerning, because right now is the tail-end of spring runoff when streams are at or near their highest flow. It’s only downhill from here through the rest of the summer, and much of Montana’s mountain snowpack isn’t high enough to sustain streams through the summer, said Troy Blandford, Montana State Library Water Information Manager.
“June is the wettest month for most counties, so the time is right now. But as you see, we’re not set up great right now,” Blandford said.
February storms helped build a decent snowpack, and the drought levels improved in central Montana. But the warm nighttime temperatures of March and low precipitation through April caused the snowpack to decline, particularly in the southwest and along the Front. Helena recorded its 2nd lowest April precipitation on record.
Last month, temperatures were above average overall but the swings were erratic. Temperatures dropped to near freezing some weeks and soared into the 90s in other weeks, breaking records in western Montana. Missoula hit 94 degrees on May 31, breaking the previous record set in 1986 by 2 degrees. The average temperature for the month was more than 2 degrees above average in Missoula, Kalispell and Butte, according to the National Weather Service.
As a result, much of the snowpack melted out early, and several streams have already experienced their peak run-off, even though many streams didn’t reach the peaks they have in the past. For example, Prickly Pear Creek near Helena had little to no runoff peak this year.
Stephen Begley, Fish, Wildlife & Parks water conservation specialist, said FWP managers in Region 2 around Missoula and Region 4 along the Front have already seen stream temperatures creeping up, so they are anticipating the need for early hoot-owl closures. Hoot-owl closures mean fishermen are prohibited from fishing during the heat of the day to avoid stressing fish that are already suffering due to warm stream water.
While snowpack plays a role in streamflow, many areas are also entering their second and third years of drought, so their river baseflows - winter flows fed mainly by groundwater - are dropping too. The groundwater is decreasing and many producers are reporting low soil moisture levels. In Philips and Liberty counties, producers are saying they probably won’t harvest winter wheat because it’s too stressed, while Dawson County producers reported that alfalfa planted in mid-April never came up.
Blandford said 20% of the state has been in some level of drought for the past five years.
“We’re seeing some of those deficits really stack up, When you look year to year and suddenly, if you’re down 3 or 4 inches a year, and that’s five years in a row, it really starts to stack up,” Blandford said. “It’s that multi-year situation.”
Only south-central Montana has continued to receive enough snow and precipitation since October to keep the snowpack healthy, the streamflows normal and the drought at bay. Remote-sensing maps show that vegetation health is still good in south-central and southeast Montana, but in northern Montana, especially along the Rocky Mountain Front and the region around Peck Reservoir, vegetation is stressed.
If June were to bring more moisture, that would turn things around. But the weather outlook doesn’t look promising, Blandford said. The National Weather Service outlooks for June show Montana is likely to have above-normal temperatures and the precipitation is likely to be below-average, according to the National Weather Service.
“The key takeaways are, in general, we’ve been making more degradations than improvements to the drought map. That’s not where we want to be headed in the spring,” Blandford said. “The West in the last 60 days (is) looking concerning. Let’s keep that in mind for the fire season.”
According to the National Interactive Fire Center, more than half of Montana - all but the southeast and far eastern portions of the state - will have above-normal potential for wildland fire by July. That will increase in August to cover all of the state except a region around Yellowstone National Park.
Contact reporter Laura Lundquist at lundquist@missoulacurrent.com.