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Study: Colorado River Flows Decreased 15% in Last Century

Cap Canal
Ted Wood
The Water Desk
The Central Arizona Project carries Colorado River water into the Phoenix area. The single largest component of the Gila River Indian Community's water rights comes from the CAP. The community recently announced plans to conserve more water in exchange for federal payments.

A new study says streamflow in the Colorado River has decreased by about 15 percent in the last century. KNAU’s Melissa Sevigny reports higher temperatures are the primary reason.

The study appears in the journal Water Resources Research.

It says the average temperature in the Colorado River Basin has risen nearly 2 degrees Celsius in the last century. The authors found this warming trend accounts for about half of the decreased runoff in the river. Other factors affecting the river’s flow include the loss of snowpack and declines in winter precipitation in certain critical areas of the Colorado River Basin.

The study’s authors say this current drought, called the Millennium Drought, began in the year 2000. It’s different from an earlier drought in the 1950s, when precipitation was unusually low. Now, temperature is playing a bigger role.

The Colorado River supplies water to nearly 40 million people. The U.S. Bureau of Reclamation has projected the first-ever shortage could be declared on the river in the year 2020.


Melissa joined KNAU's team in 2015 to report on science, health, and the environment. Her work has appeared nationally on NPR and been featured on Science Friday. She grew up in Tucson, Arizona, where she fell in love with the ecology and geology of the Sonoran desert.
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