"Millions of gallons of water used to flow every day from the Rocky Mountains to the Gulf of California. Now, the Colorado River ends at Morelos Dam on the U.S.-Mexico border. Below it, one of North America's largest wetlands is dry.
Karl Flessa, a geoscientist at the University of Arizona, began researching the damage two decades ago. Then he started asking how much water it would take to bring back some of the habitats.
That push for restoration paid off. Mexico is releasing part of its river allotment for eight weeks — the first time ever that water has been released to benefit the environment. It's called a pulse flow because it mimics a spring flood: a one-time event, before possible drought restrictions."