United States Department of Geological Survey hydrologists inspect flood waters while attaching a water level sensor onto a tree at Riverbend Park in Oroville, California, U.S., on Wednesday, Feb. 15, 2017. Crews worked overnight into Wednesday to reduce the risk of catastrophic flooding at the nation's tallest dam, racing to stay ahead of rains forecast for Wednesday. As the authorities lowered the level of the reservoir behind the dam, more than 100,000 people who had been evacuated began to return to their homes in the valley below it. Photographer: Michael Short/Bloomberg via Getty Images
