Qanat

A qanāt (Persian: قَنَات) or kārīz (کَارِیز) is a water supply system that was developed in ancient Iran for the purpose of transporting usable water to the surface from an aquifer or a well through an underground aqueduct. Originating approximately 3,000 years ago, its function is essentially the same across the Middle East and North Africa, but it is known by a variety of regional names beyond today's Iran, including: kārēz in Afghanistan and Pakistan; foggāra in Algeria; khettāra in Algeria and Morocco; the daoudi-type falaj in Oman and the United Arab Emirates; and ʿuyūn in Saudi Arabia. In addition to those in Iran, the largest extant and functional qanats are located in Afghanistan, Xinjiang in China (the Turpan water system), Oman, and Pakistan.

Proving crucial to water supply in areas with hot and dry climates, a qanat enables water to be transported over long distances by largely eliminating the risk of much of it evaporating on the journey. The system also has the advantage of being fairly resistant to natural disasters, such as floods and earthquakes, as well as to man-made disasters, such as wartime destruction and water supply terrorism. Furthermore, it is almost insensitive to varying levels of precipitation, delivering a flow with only gradual variations from wet to dry years.

The typical design of a qanat is a gently sloping tunnel accessed by a series of well-like vertical shafts visible at ground level. This taps into groundwater and delivers it to the surface at a lower level some distance away, via gravity, therefore eliminating the 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.

To date, the qanat system still ensures a reliable supply of water for consumption and irrigation across human settlements in hot, arid, and semi-arid climates, but its value to a population is directly related to the quality, volume, and regularity of the groundwater in the inhabited region. Since their adoption outside of the Iranian mainland in antiquity, qanats have come to be heavily relied upon by much of the Middle Eastern and North African populations for sustenance. Likewise, many of the continuously inhabited settlements in these regions are established in areas where conditions have historically been favourable for creating and sustaining a qanat system.

Common variants of qanat in English include kanat, khanat, kunut, kona, konait, ghanat, ghundat and quanat.

Qanāh (قناة) is an Arabic word that means "channel". In Persian, two words are used: kārīz or kārēz (كاريز), which is derived from the earlier word kāhrēz (كاهریز); and qanāt (قنات). Other names for qanat include kahan (Persian: کهن); kahn (Balochi); kahriz/kəhriz (Azerbaijan); khettara (Morocco); galerías, minas or viajes de agua (Spain); daoudi-type falaj (Arabic: فلج) (United Arab Emirates and Oman); foggara/fughara (North Africa). Alternative terms for qanats in Asia and North Africa are kakuriz, chin-avulz, and mayun.

According to most sources, qanat technology was developed by the ancient Iranians sometime in the early 1st millennium BCE and slowly spread westward and eastward from there. Other sources suggest a Southeast Arabian origin. Analogous systems appear to have been developed independently in China and in South America (specifically, southern Peru).

A cotton species, Gossypium arboreum, is indigenous to South Asia and has been cultivated on the Indian subcontinent for a long time. Cotton appears in the Inquiry into Plants by Theophrastus and is mentioned in the Laws of Manu. As transregional trade networks expanded and intensified, cotton spread from its homeland to India and into the Middle East. One theory is that the qanat was developed to irrigate cotton fields, first in what is now Iran, where it doubled the amount of available water for irrigation and urban use. Because of this, Persia enjoyed larger surpluses of agricultural products, thus increasing urbanization and social stratification. The qanat technology subsequently spread from Persia westward and eastward.