The Los Angeles River...what's left of it (starts @~1:36)!

Southern California is naturally a dry region, but it has millions of people (drawn by nice climate, etc.)!  It has to import lots of water from far away, like the Colorado River and the Owens Valley...check out the Los Angeles River in this video clip chase scene (starting at ~1:36) when the motorcycle heads down into the concrete ditch.  The concrete ditch is the Los Angeles River . . . What do you think . . . would the Los Angeles River support 7 million+ people in the area?