Permaculture has at its heart water retention, with ponds and swales. Swales are holes dug into hillsides above trees to allow rainwater to seep into the the ground to reach the roots of trees and other plants. simple and effective water conservation.

In Portugal where I live, cobblestones are used to pave sidewalks and in villages on the roads too. The water seeps between the cracks and into the sand that they are set in, a technic first used by the Romans.