There are thirsty regions in Iran with no river curving or crawling on it; with lowest amount of rain touching its body, yet settlements initiate and thrive in them. Living in these areas is only possible if water is transferred to the region with an inexpensive and uncomplicated way. Invention of Qanat was the brilliant solution to this matter. Qanat was born three millenniums ago in deserts of Iran as most effective technique for the best adaptation to arid areas.
Qanat is a tunnel system that carries water from a bed source of higher elevation to flat lands. It consists of a series of vertical wells built along a gentle slope that are connected to a horizontal duct at the bottom.
If you look at a Qanat from above it looks like a formicary on foot of a hill.
Duct must have enough space for Qanat workers to move and dig in it. Vertical shafts are for removing the excavated material and supplying oxygen for workers. Also they provide a proper access to different parts of the duct for repair and maintenance. Mother well is the first well that is the deepest of all. The tallest Mother Well in Iran is 300m deep in Gonabad, Razavi Khorasan Province.
The final destination of a Qanat is Mazhar-e Qanat where the water flows to the surface after its long voyage.
According to Iranian Ministry of Energy there are 363000 Qanats in Iran. For each of these Qanats If the average length of duct is 6km and total depth of wells is 4km with a mouth with one meter diameter, there will be 376068 km of soil that is 9.4 times longer than the earth equator and covers 97.9% of the distance between earth and the moon.
One remarkable Qanat in Iran is Vazvan in Isfahan province. The extraordinary character of Vazvan is that its duct is dug in stone and there are dams in some wells to save water during winter and use it on other times of the year. This Qanat was built during Sassanid era (224–651) and is one of eleven Qanats registered in world heritage list of UNESCO.
Another unique Qanats is Moon in Ardestan, Isfahan province. Moon has two ducts at two levels. The first duct is 30m bellow the ground and the second one is 3m higher at 27m depth. Water running in the second duct does not transmit to the duct below.
Creation of Qanat goes back to 7th century BC in Iran but during Achaemenid Empire it had a major extension throughout the territory. Qanat specialists started building numerous Qanats from shores of the Mediterranean Sea to Chinese Turkistan which resulted in expanding and establishing settlements in dry regions of Persia.
Arabs had a share in extending this water system worldwide by their invasions across North Africa, Sicily, and Spain.
On July 15, 2016 the World Heritage Committee of the UN Educational, Scientific and Cultural Organization (UNESCO) met in Istanbul, Turkey and registered eleven Qanats in different provinces such as Kerman, Khorasan Razavi, Yazd, Arak, and Isfahan.