There is currently a contest for interesting sustainable living concepts in the Philips Livable Cities Award. One of these is about collecting rainwater in the Yemeni capital from rooftops. There is a short video on this that can be accessed here. You need to scroll down to the option called “Rainwater Aggregation.” Voting continues until March 24, 2011. If you vote, you might win a trip to the handing out of the award in The Netherlands.