Lolo residents have wondered for years, as far back as the 1960s, why certain stretches of Lolo Creek often run dry.
So the state of Montana, through its Groundwater Investigation Program, decided to invest in finding an answer.
“This is a fairly robust perennial stream and then in certain years in some parts it goes dry,” senior research hydrogeologist John Wheaton said. “That’s not common.
“There’s no smoking gun.”
Wheaton is with the Montana Bureau of Mines and Geology, which oversees the program, and he said his research team came up with almost a dozen reasons they think Lolo Creek would lose so much water year after year.
Now they have a little over a year to collect data and see which, if any, of those reasons are true.
The bureau started monitoring Lolo Creek in April 2016, after several years in which large portions of the creek ran dry, hurting fish and animal populations.
According to the Bureau’s webpage for the project, the creek may have run dry as far back as the 1960s, though recorded instances start in the '80s and most recently include 2007, 2011, 2013 and 2015.
An August 2016 article from the Ravalli Republic reported about a mile and a half of the creek was dry.
The site credits increasing development in Lolo, which brings more wells, as a possible cause for sucking away more water.
It also mentions a possibility that irrigators are using more than their allocated water rights, though some told the Clark Fork Coalition’s Jed Whitely in August they’d voluntarily cut back on their usage, according to the Ravalli Republic article.
Travis Ross, an Environmental Health Specialist for the Missoula Valley Water Quality District, offered some more reasons the creek might be running dry.
Variance in snowpack levels, irrigation diversions and groundwater seepage all contribute to low water levels in Lolo Creek, he said.
“It’s kind of a complex environment,” Ross said. “Ultimately it’s to understand why the creek is being depleted.”
The Missoula Board of County Commissioners approved a contract Tuesday for the Missoula Valley Water Quality District to conduct field work for the Montana Bureau of Mines and Geology’s study of Lolo Creek.
The bureau has around 80 wells it monitors, Wheaton said, and about 15 spots in the stream where it collects data.
So Ross and other employees will be out into the field gathering water level readings to compile into data sets to send to the bureau for analysis.
Wheaton and his team will then use the data to understand the “dynamics” of the creek, finally comparing it against weather reports, to determine if 2017 was a more a wet year or a dry year.
After all that, they hope to determine a cause.
The data analysis will take place through 2017, with any additional research being done in 2018. Wheaton hopes to have a final report by the end of that year.