The subterranean tunnel-wells known as Qanat are extremely important in the history of irrigation and human settlement in the arid lands of the old world. Qanats have strongly influenced village socio-economic organization and patterns of ownership and tenure. Qanats are constructed as a series of well-like vertical shafts, connected by gently sloping tunnels. Qanats tap into subterranean water in a manner that efficiently delivers large quantities of water to the surface without any need for pumping. The water drains rely on gravity, with the destination lower than the source, which is typically an upland aquifer. Qanats allow water to be transported over long distances in hot dry climates without losing a large proportion of the water due to seepage and evaporation.
A Qanāt (also called Kārīz) is a water management system originating in pre-Achaemenid Persia (Ward English 1968) and used to provide a reliable supply of water to human settlements and for irrigation in hot, arid and semi-arid climates.
The oldest written evidence regarding the use of Qanats is an inscription in cuneiform from the time of Assyrian King Sergon II (who reigned between 722 and 705 B.C.) which describes an irrigation system near the Urmia Lake ( Lass ø e 1951) . He brought this method to the town of Assur and his son Sennacherib (who reigned between 705 and 681 B.C.) who built Qanats in Nineveh and Arbela (today’s Arbil in Iraq). After this period, the Medes were also familiar with this technique. Cities such as Ecbatana (today’s Hamedan) were also watered by Qanats in the seventh century B.C. (Goblot, 1963, Braun 1974).
Over many centuries the construction technique of Qanats was introduced to other countries and was used as a method of water supply in arid areas from the far east to south America. Nowadays Qanats can be found in about 34 other countries.
Parts of Qanat
A Qanat consists of the following main parts:
· Trial Well: A well dug to determine the location of the water table and main well.
· Main Well (also known as mother well): The main water source for a Qanat
· Access Shaft: Permits access to the Qanat channel for construction or maintenance and is also used for ventilation
· Qanat Channel: The Qanat’s water-carrying channel which is (almost) horizontal and connects the bottom of the access shafts
· Outlet: The place where water is coming out of the Qanat and onto the ground surface
· Open Channel: A channel used to convey the water from the outlet to a network of dams, gates and other channels for water distribution
The main parts of a Qanat
Lass ø e , J., 1951, The irrigation systems at Ulhu (8th century B.C.) , Journal of Cuneiform Studies, Vol. 5, pp. 21-32.
Braun, C., 1974, Teheran, Marrakesch und Madrid – Ihre Wasserversorgung mit Hilfe von Qanaten, Eine stadtgeographische Konvergenz auf kulturhistorischer Grundlage. Heft 52, Bonner Geographische Anhandlungen, In Kommission bei Fred. D ü mmlers Verlag, Bonn.
Goblot, 1963, “Dans l’ancien Iran, les techniques de l’eau et la grande historie” Annales É conomies Soci étés Civilisations, 18: 499-519.
Ward English, P., 1968, “The origin and spread of Qanats in the Old World” Proceedings of the American Philosophical Society, Vol. 112, No. 3, (June 1968), pp. 170-181.