One of Kumamoto’s outstanding features is its groundwater. It’s my understanding that Kumamoto City is the only major city in Japan that relies entirely on groundwater. This year, Kumamoto has received a United Nations award for its efforts to maintain and conserve its groundwater resources.

http://www.un.org/waterforlifedecade/winners2013.shtml

The article is quite detailed and worth reading. I first learned about the award here:

http://www.waterworld.com/articles/2013/03/world-water-day-2013-japan-groundwater-recharge-project-praised.html

The article seems to be a shorter version of the one I’ve introduced above.