Last week heavy rain brought a torrent of runoff into the Chicago River, bringing it above the walls designed to protect the downtown riverwalk construction. The excess water caused the city to open the locks, spilling millions of gallons of not-so-clean water into Lake Michigan, closing the beaches to swimmers for part of the holiday weekend. We explore what runoff does to a river so many have worked so hard to clean up, and how we might capture and use clean rainwater before it hits the river or runs down the sewers. Photo: Flickr/Mr Ush