A warming climate is drying out tiny mountain streams that feed the West’s biggest rivers

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By Chris Clements, KNAU News - Arizona Public Radio. 

Excerpt: Western rivers like the San Juan and the Colorado are mostly fed by burbling mountain streams, which are themselves fed by groundwater and snowmelt. But a study published on June 5 says those tiny streams are in trouble. The study in the journal Earth's Future says the base amount of water in streams and rivers that doesn’t come from rain, also known as “base flow,” has been steadily declining since 1950, though that trend varies depending on the specific time period. ...The study...predicts that if climate warming continues, by the end of the century, headwater streams could have anywhere from 45% to 65% less base flow to sustain them. ...water levels in Lake Mead reach their lowest point ever. The Colorado River Basin has faced aridification for the last 26 years. Tiny, ephemeral streams like Flagstaff’s Rio de Flag give mighty rivers the juice to flow freely. But they depend on base flow to do that. ...[The Rio de Flag] could be seen as a headwater stream that leads to the Little Colorado, which leads to the Colorado, et cetera.... Mroczek says less base flow in streams and rivers is a big deal, because that water keeps them alive during dry periods like late summer and times of drought.... 

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