新疆水危机：干涸的坎儿井

choi

杰安迪, 新疆水危机：干涸的坎儿井. 纽约时报, Sept 21, 2016
http://cn.nytimes.com/china/2016 ... ls-are-running-dry/

, which is translated from

Andrew Jacobs, Xinjiang's Ancient Water Tunnels Are Running Dry. New York Times, Sept 22, 2016.

Note: 坎儿井  karez
(a) qanāt. Encyclopaedia Britannica, undated
https://www.britannica.com/technology/qanat
(qanāt is Arabic, karez is Persian)

Quote: A qanāt is "often several kilometres long, to the places where it is needed for irrigation and domestic use. The development of qanāts probably began about 2,500 or 3,000 years ago in Iran, and the technology spread eastward to Afghanistan and westward to Egypt. Although new qanāts are seldom built today, many old qanāts are still used in Iran and Afghanistan, chiefly for irrigation.

(b) Various Authors, Harvesting Water and Harnessing Cooperation: Qanat Systems in the Middle East and Asia. Middle East Institute, Jan 18, 2014.
http://www.mei.edu/content/harve ... iddle-east-and-asia

Note: View the graphic only, where the brownish belt topped with "Vertical access shafts" are what one will see from the top, in the air.

(c)
(i) The basic feature of a qanat is an essentially horizontal channel that brings water from an underground water source to an outlet near a civilization. There is also a shaft known as a mother well that rises vertically from the underground water source to the surface of a mountain or hill. Creating such a system is extremely expensive, and was especially so in ancient times, since all of the materials excavated from the channel and mother well must be carried above ground, either through the channel outlet or the top of the mother well. To aid in the construction, there are often one or more additional vertical shafts placed at strategic locations above the underground channel. Although these shafts must also be excavated, they provide a means for lifting additional dirt from the horizontal channel."
(ii) "There are significant advantages to a qanat water delivery system including: (1) putting the majority of the channel underground reduces water loss from seepage and evaporation; (2) since the system is fed entirely by gravity, the need for pumps is eliminated"
(iii) One website says vertical shafts are also used, after construction, for maintenance of qanāts.