By Elizabeth Zach, staff writer

Colorado RiverA U.S. Geological Survey shows that a little more than half of the Colorado River, the West’s primary water source, is groundwater before it seeps into the river bed. The preliminary finding may help city water supply managers anticipate future volumes amid rising temperatures and less snowfall.

Questions remain, however, said Matthew Miller, the survey’s lead author.

“How old is the groundwater coming into the river system?” he told The Denver Post. “If it is young, you might expect the flow would change more rapidly in response to a change in precipitation. If the groundwater is very old water, then you can say we have a cushion.”

The Colorado River supplies water to more than 50 million residents in the arid American West, and by 2030, the number could increase by another 23 million. The river provides water for crop irrigation and livestock, residential neighborhoods, electricity generation and industries such as mining.

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