ProPublica has published part four of its series on Colorado River water use. This one focuses on the Navajo Generating Station in Page in far northern Arizona.

The plant has troubled the EPA because of the pollution it spews into the air, but it also helps move trillions of gallons of water into Arizona’s biggest cities like Phoenix and Tucson. The coal-fired plant also uses a lot of water.

So what would happen if alternative energy such as solar became more prominent? We asked Martin Pasqualetti, senior sustainability scientist at ASU’s Global Institute of Sustainability.