Study: Colorado River Flows Decreased 15% in Last Century

Sep 7, 2018

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.

Lake Mead
Credit U.S. Bureau of Reclamation

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.