For 96 years, a concrete dam in central Arizona diverted almost every drop of water from a desert creek that had been flowing for thousands of years. The streambed went dry. The native fish started vanishing. The turquoise pools that once defined the canyon shrank to almost nothing. Then in 2005, Arizona did something almost nobody in the American Southwest had ever done. They shut the dam down, pulled out the flumes, and gave the river its water back. What that creek did next rewrote everything scientists thought they knew about how fast a dead ecosystem can recover.