Qanat, Traditional Eco-technology for Irrigation and Water Management

To make use of the limited amounts of water in arid region, the Iranians developed man-made underground water channels called qanats (kanats) .In fact, qanats may be considered as the first long-distance water transfer system. Qanats are an ancient water transfer system found in arid regions wherein groundwater from mountainous areas, aquifers and sometimes from rivers, was brought to points of re-emergence such as an oasis, through one or more underground tunnels. The tunnels, many of which were kilometers in length, had designed for slopes to provide gravitational flow. The tunnels allowed water to drain out to the surface by gravity to supply water to lower and flatter agricultural land. Qanats are up to 3000 years old artificial sub-horizontal underground water channels, 5 to 80 km long, widespread in Iran, but also common in western China, Arabia and the Mediterranean; they were excavated from the bottom of vertical shafts, starting from their exit and advancing upstream till main, productive wells, constructed at the very beginning of the project were met. In this paper, structure, function and also distribution of qanats in Iran are illustrated using library documents. According to the results, qanat is the most sustainable technology for groundwater management and also complies with social, environmental and economic circumstances of the region.