A punishing drought in the U.S. is threatening millions of livelihoods, as extreme heat and lack of rain are bringing the Colorado River and Lake Mead to some of their lowest water levels ever.

Those levels and their barren landscapes won't just impact the environment and the 40 million American people who rely on that water. They could even prevent the Hoover Dam from generating enough electricity, too.

Reggie Cecchini looks at what could happen if states can't reduce water usage.