How Oroville went from drought to an overflowing dam in just two years

An unusual amount of rain, climate change and unexpected erosion of an emergency spillway created a perfect storm at Lake Oroville in California

It was only two years ago that the receding waters of Lake Oroville - California's second largest reservoir, located about 70 miles north of Sacramento - became the defining image of the state's historic drought.

"It was so low you couldn't take your boat out on it," said Joe Pederson, a 52-year-old resident of Oroville. "There are fish but you can't get to them. It was so low you could walk along sections of the lake."