A qanat or kārīz is a system for transporting water from an aquifer or well to the surface through an underground aqueduct; the system originated approximately 3,000 years ago in Iran.[1] The function is essentially the same across the Middle East and North Africa, but the system operates under a variety of regional names: qanat or kārīz in Iran, karez in Afghanistan and Pakistan, foggara in Algeria, qanat in Malta, khettara in Morocco, falaj in Oman and the United Arab Emirates, and uyūn in Saudi Arabia, etc.[1] The largest extant and functional qanat systems are located in Afghanistan, Algeria, Iran, Oman, Pakistan, and the oases of the Turfan region in Xinjiang, Northwestern China.[1]
This is a system of water supply that allows water to be transported over long distances in hot dry climates without losing much of the water to evaporation. The system has the advantage of being resistant to natural disasters such as floods and to deliberate destruction in war. Furthermore, it is almost insensitive to the levels of precipitation, delivering a flow with only gradual variations from wet to dry years.
Karez are constructed as a series of well-like vertical shafts, connected by a gently sloping tunnel. This taps into underground water and delivers it to the surface by gravity, without need for pumping. The vertical shafts along the underground channel are for maintenance purposes, and water is typically used only once it emerges from the daylight point.
The qanats still create a reliable supply of water for human settlements and irrigation in hot, arid, and semi-arid climates, but the value of this system is directly related to the quality, volume, and regularity of the groundwater. Much of the population of Iran and other arid countries in North Africa and West Asia historically depended upon the water from qanats; many populated areas are close to the areas where qanats are possible.[2]
