A river in Colorado that was turned sickly yellow by a mine waste spill reopened for recreational use today after the now-diluted toxic plume passed through and reached Lake Powell—a huge reservoir 300 miles downstream that feeds the Colorado River and supplies water to the Southwest. Water officials said the plume that includes lead, arsenic, and other heavy metals now presents little danger to users beyond Lake Powell—such as the city of Las Vegas—because the contaminants will further settle out and be diluted in the reservoir along the Utah-Arizona border.