In the parched Colorado River basin, water managers are turning over every stone looking for ways to keep the taps flowing. Now, they’re finding more water in some unusual places – shower drains and toilet flushes.

At a sprawling sewage treatment plant in Carson, California, the occasional breeze delivers a pungent whiff of a reminder of how used water becomes “reused.” Here, the Metropolitan Water District of Southern California is planting the seeds for a massive new facility, where a multi-billion-dollar installation could help recycle wastewater and keep drinking supply flowing for the agency’s 19 million customers.