Stream flows are changing in major ways along the Missouri River thanks in large part to climate change, and those shifts are having big impacts on thousands of farmers, businesses, vacationers and others who depend on it.

The news comes in a U.S. Geological Survey study published in late July, which examined stream flow data from more than 200 streamgages up and down the Missouri between 1960 and 2011.

Nearly half of the streamgages surveyed showed that flows had increased or decreased over time during the past 50 years, with areas in the river's eastern watershed -- in states like Iowa and the Dakotas -- experiencing higher streamflows, while those further west were lower.

That has led to serious water shortages for farmers in places like Montana, where one farmer told the Los Angeles Times he'd had to spend more than $10,000 to remove sand that had choked the irrigation system he uses to farm sugar beets and malted barley.

"Every year it gets worse," Rocky Norby, who has farmed his Montana land along the Missouri for more than two decades, said in an interview with the Times. "There's not enough water to get through our pumps."

But they're seeing the opposite problem to the east, in places like North and South Dakota, where fields along the river are often too muddy from flooding to plant.

It's a pattern climate scientists expect to continue in a world that keeps getting warmer. "Climate change models predict that where it is wet, it will get wetter, and where it is dry, it will get drier," Matt Rice, a program director at the conservation nonprofit American Rivers, told the Times.

Temperatures already have increased between 3 and 4 degrees Fahrenheit in the Great Plains, the Environmental Protection Agency says, and a rise of roughly 5 to 6 degrees Fahrenheit is expected for the Missouri River basin by 2050.

The nation's longest river, the Missouri begins high up in the Rocky Mountains of Montana and stretches more than 2,500 miles through 10 states before it reaches St. Louis, where it merges with the Mississippi. Together, the river and its tributaries encompass roughly one-sixth of the continental U.S.

That means the river is a critical resource for tens of millions of people. “The Missouri River and its tributaries are valuable for agriculture, energy, recreation and municipal water supplies,” said Parker Norton, a USGS hydrologist and the study lead author. “Understanding streamflow throughout the watershed can help guide management of these critical water resources.”

The study also cautions that climate change isn't the only reason the Missouri has experienced such big changes in streamflow patterns, pointing out that higher streamflows had been recorded even in places where water usage also had risen, in places like the Dakotas.

Groundwater pumping also may be to blame for lower flows in some areas, the authors note. But the impacts are undeniable, especially in states like Montana, where the Times noted that some of its famous fishing areas have had to be closed during the tourist season because of "low flows, high temperatures and too much stress on fish."

Read the full story in the Los Angeles Times or download the study from the U.S. Geological Survey.

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