Did you see this one?
http://www.nationalgeographic.com/ngm/0009/feature1/index.html
Everybody's doing it!
Another map...I was under the impression most of these discoveries were taking place in the Moche Valley, but I can't see it named on the map.
Moche Valley - irrigation channels.
http://kyapa.tripod.com/agengineering/canaltechnology/canals.htm