Everyone knows the Los Angeles river. Even if it’s not part of your neighborhood, the concrete-lined channel is familiar worldwide, because nothing else in the movies or television better depicts “urban wasteland” than this drain. But soon this stark, 51-mile (82-km) waterway may symbolize something else: tough choices amid water scarcity. California’s historic five-year drought has prompted the Los Angeles region to look at using the river as a water supply – a role it has not served in over a century.