Changes in statewide precipitation underline need for more data
Laura Lundquist
(Missoula Current) Over the past few decades, the effects of drought have become more variable across Montana, so the state needs more environmental information to fill in the gaps.
At Wednesday’s meeting of the Montana Drought and Water Supply Advisory Committee, committee members heard a review of the past year’s drought conditions - water years run from October to October - and discussed the increasing difficulty of deciding how to classify drought, now that climate change is causing so many seasonal shifts and variability in precipitation and temperature.
Troy Blandford, Montana State Library Water Information manager, said this summer’s weather threw him a curveball. In June, after a warm, dry spring, he’d already written the summer off as far as precipitation. Then, July and August experienced “exceptional precipitation” compared to past years although parts of the state saw more than others. It helped bring yearly precipitation totals up, but the rain came too late for the growing season so crops were still affected. Then it was followed by a warm, dry September.
The result is that the Blackfoot and Clark Fork river basins remain in extreme drought with the rest of western Montana in severe drought. East of the Continental Divide, the northern portion of the state experienced some of that July-August precipitation, so it’s only abnormally dry although the rain skipped over some areas, including the Fort Peck Reservation, leaving it in moderate drought. The bright spot with little to no drought is southeastern Montana.
Due to the government furlough, U.S. Geological Survey employees couldn’t provide a streamflow update because they’re furloughed. So Michael Downey of the Montana Department of Natural Resources and Conservation piggy-backed on Blandford’s drought discussion, explaining why some regions can be in worse categories of drought and have record low streamflows, even though they might have received decent rain and snow this year.
Going back five years, 2022 was a fairly good year for annual precipitation with most basins receiving close to normal amounts of rain and snow. But then, in 2023, 2024 and 2025, annual precipitation in several western basins has been below normal.
Zooming in on the lower Clark Fork River basin, Downey showed that each year’s accumulated precipitation decreased after 2022 and has started leveling off in July because that’s when the snowpack is gone. As a result, the Clark Fork basin has a five-year deficit of more than 77 inches of precipitation when compared to what it should have had with five years of average precipitation, which is 63.2 inches a year.
Back-to-back years of below-normal precipitation causes groundwater to decrease too, so groundwater can’t feed streams the way it used to. The Blackfoot valley is experiencing that this year where the North Fork of the Blackfoot River has some reaches with no water.
“That deficit just keeps building,” Downey said. “That’s what’s giving us our low flows. These are legacy drought issues that have caught up to us. Of course, this is only five years. If you look at 10 years, and how many droughts in that 10 years and how many inches we’re in deficit, it’s going to be even higher.”
Meanwhile, in north-central Montana, the Milk River basin has a five-year surplus of 13 inches precipitation. However, the problem there is the rain is now coming at a different time of year: July and August instead of May and June.
Shifts in annual precipitation are becoming more evident across the state, prompting the committee to question whether new parameters should categorize drought. Storm events are occurring in different months and are becoming more extreme than in the past. East of the Rocky Mountain Front, Glacier County received about 5 inches of rain in two days but it was patchy. Farther east along the county line, it was still dry.
“The question becomes: If it’s wet in late summer and we get tons of moisture, but our crops have not come to fruition, are we still in drought?” one committee member said.
It’s important to classify drought accurately, because farmers and ranchers can’t get federal funding for crop or livestock losses if their farms or ranches aren’t included in drought-designated areas. But when western Glacier County received so much rain that it saw flooding, and the other part of the county remained mostly dry, the situation can’t be described on a county-by-county basis. Similarly, southern Blaine County received none of the rain that northern Blaine County got. The committee concluded that future evaluations of drought must include aspects of precipitation timing and soil and hydrological conditions, along with agricultural impact. And they should also have enough data to identify localized differences.
“We’re lacking in some of that resolution. So that interpolation misses some of that geographic variability that we have in Montana that we don’t have in the Midwest. But in Montana, it’s statewide,” Downey said.
Because it’s such a large, diverse landscape and much of it is remote, Montana has struggled to collect enough data for thorough drought coverage. But that’s slowly changing.
Last year, the Montana State Library set up a Drought Impact Reporter that allows agricultural producers to submit information and photos about soil moisture in their area. Committee members said the reporter has helped inform them about conditions in areas where they have data gaps. Now, they need to figure out how such anecdotal information could be turned into criteria for drought designation.
For hard data, the Montana Climate Office at the University of Montana has also been installing small weather stations on the eastern side of the state to fill in the MESONET, one of the densest networks of stations in the nation, said state climatologist Kelsey Jensco. With money from the National Oceanic and Atmostpheric Association and more recently the U.S. Army Corps of Engineers, they’ve installed 36 stations for a total of 216 in Montana and hope to install at least three dozen more next year before the funding runs out in 2027.
The stations would improve resolution for drought evaluations across the eastern part of the state that forms the headwaters of the Missouri River. Future plans include expansion west into the Columbia River basin. There’s just two problems: land and money.
The Climate Office needs to find another three dozen Montana landowners in key spots to allow them to install the last stations needed for the network. More importantly, the existing funding is only for the installation of the weather stations. Once the network is set up, the Climate Office needs money to sustain the program into the future. Jensco said annual operations and maintenance costs for MESONET would run about $2.2 million.
“We’re going to continue to pursue federal support for the development of these systems, but we currently don’t have state support,” Jensco said. “State support is needed to keep all this operational. We can’t maintain it in the long run.”
The committee said a cost-benefit analysis would probably show the price tag is small compared to the value of the benefit provided to agricultural producers and water managers. DNRC administrator Anna Packenham Stevenson said it would be worth asking the Legislature to include money in the DNRC budget to support the MESONET.
“I think these components are critical to the work we all do. It would be a huge resource to go away,” Packenham Stevenson said.
Contact reporter Laura Lundquist at lundquist@missoulacurrent.com.