December 3, 2012 (Persian calendar 1391/9/13) A Kariz كاريز is one of a series of well-like vertical shafts, connected by gently sloping tunnels. They create a reliable supply of water for human settlements and irrigation in hot, arid and semi-arid climates. The qanat technology is known to have been developed by the Persian people sometime in the early 1st millennium BC and spread from there slowly west and eastward. The value of a qanat is directly related to the quality, volume and regularity of the water flow. Much of the population of Iran and other arid countries in Asia and North Africa historically depended upon the water from qanats; the areas of population corresponded closely to the areas where qanats are possible. Although a qanat was expensive to construct, its long-term value to the community, and thereby to the group that invested in building and maintaining it, was substantial. See 'Persian ancient water plant' in these videos: [English] http://www.youtube.com/watch?