Controlling Water in Arid Lands: Qanats, Karezes, Foggaras, and Aflaj

What is a Qanat, Foggara, Khettera, or Kariz?

Row of Shafts into the Qanat at Ain Manawir, Egypt from NYU Excavations at Amheida (2006)
Row of Shafts into the Qanat at Ain Manawir, Egypt from NYU Excavations at Amheida (2006). copyright 2006 NYU Excavations at Amheida (used with permission)

Qanats are ancient water control systems made up of a combination of shaft wells and horizontal tunnels built to tap into subsurface water stores called aquifers. Qanats are one of several water control technologies developed in the ancient past to compensate when surface water supplies are sporadic or not drinkable. Qanat technology is at least 3,000 years old, and they are still found operating today in areas of the Mediterranean, the Near and Middle East, North Africa, and central Asia.

The Iranian word "qanat" derives from an ancient Semitic word meaning "to dig": but they are known in Palestine and Algeria as fuqara, fuqara or foggara; in Spain as madjira or mayra; in Arabia as falaj (plural aflaj); in Morocco and parts of the Sahara as khotara, khettera or khottara; and in Afghanistan and China, they are called karez, qareez, or kariz.

Qanats are not the only type of water control used anciently in arid and semi-arid lands in these regions: others are canals moving water above ground, found near the Euphrates and Tigris rivers; norias--water wheels, screw-like mechanisms that raise water upwards--found along the deeply entrenched ranges of the Orontes River valley; and dams to contain and raise the water level. Societies in the past learned to adopt and adapt what technologies were most appropriate to the circumstances. Qanats were best in situations where surface waters rapidly disappeared as a result of rapid evapo-transpiration.

What Engineering Skill Does it Take to Build a Qanat?

Qanat Cross-Section
Qanat Cross-Section. Samuel Bailey

A qanat consists of several working parts. The mother well (called "madari chah"), was a 1-meter (3.5-foot) wide opening dug perhaps over 100 m (350 ft) deep that opened into the aquifer. At the opposite end of the system was a collection pool where the water could be distributed ("mazhar"). An underground tunnel leading between the the mother well and the collection pool was excavated to a specific gradient to allow gravity to push the water downhill. And finally, a row of ventilation wells were excavated down into the underground tunnel at intervals to allow maintenance of the below ground channel.

The size of a qanat system depends on its specific environment. In the lower reaches, the ventilation shafts may only be a few meters deep; some of the mother wells are well over 100 meters deep. The size of the horizontal tunnels varies between .5-1 m (2-3.5 ft) wide and 1.2-1.8 m (4-6 ft) high. The tunnel often opens into an above-ground channel and that often leads to a pond where water is stored at night or a comblike structure called a kasria that divides the water into separate canals. Qanats can be linear, with water flowing along a single tunnel, or radial, with branched subground tunnels flowing out of the main channel tapping the aquifer.

Digging a Qanat

The method of building a qanat was described in an 11th century document by the Muslim mathematician Abu Bakr Al-Karaji. Qanats were planned and executed by muqannis, a hereditary guild of professional diggers from the town of Yazd, who were highly esteemed and highly paid for their dangerous work.

The muqannis would first locate and excavate the mother well in the best location to pierce the aquifer. Then, they would survey the area and identify the destination site (mazhar). They'd have to figure out the feasiblity of the project, based on achievable channel slope, soil type and gradient. The most dangerous part of the task was the tunnel excavation, which must be started from the lowest collection point and then extend gradually upward into the aquifer where it meets the mother well.

When Was Qanat-Assisted Water Control Invented, and How Did it Spread?

Gate in the Qanat Tunnel beneath the Water Mill at Nain, Iran
Gate in the Qanat Tunnel beneath the Water Mill at Nain, Iran. NAEINSUN

Most scholars believe the qanat originated during the Persian Empire about 700 BC--certainly they were in use under the rule of the Achaemenid ruler Darius the Great [558-486 BC]. Darius' Persian conquests spread the system outward; and eventually the Roman and Islamic Empire were partly responsible for further spreading the technology.

Qanats were the main water supply for such ancient cities as Tehran (Iran), Marrakech (Morocco), Palermo (Sicily), Setubal (Portugal), and Madrid and Majorca (Spain). Madrid used qanats from the foundation of the city in the 9th century until the late 19th century; some linguists believe the city's name comes from the Arabic word "mayrit", which means "the place of many qanats". Madrid's qanat system ran for a length of some 125 kilometers (77 miles) during its prime.

The central Asia Turpan oasis, in Xinjiang province in China, contained over 1,000 qanat systems; as of 2009, 238 of them were still functioning. Turpan's qanat system, perhaps adopted at least as early as the early Tang Dynasty (AD 618-907], is considered the third great construction project in ancient China, after the Great Wall and the Grand Canal. Some scholars believe the qanat system at Turpan may date as early as the Han Dynasty [206 BC-220 AD], and Han Dynasty Silk Road travelers could definitely have learned about the technology and spread it eastward into Turpan. 

Sources and Help for Additional Research into Qanat Water Control

Inside a Qanat Motherwell, near Yadz, Iran
Inside a Qanat Motherwell, near Yadz, Iran. reibai

Much of the recent research on qanats are on their modern day use, including the sustainability of qanat water control, the detection and repair of ancient systems, and discovering the technologies of the engineers who built them. See in particularly Joshka Wessels' essay on Qanats and Water Coopration for a Sustainable Future posted on the Middle East Institute's website.

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Bertrand A. 2010. The hydraulic systems in Turfan (Xinjiang). The Silk Road 8:27-41.

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Martínez-Santos P, and Martínez-Alfaro PE. 2014. A priori mapping of historical water-supply galleries based on archive records and sparse material remains. An application to the Amaniel qanat (Madrid, Spain). Journal of Cultural Heritage 15(6):656-664. doi: 10.1016/j.culher.2013.12.003

Naghibi SA, Pourghasemi HR, Pourtaghi ZS, and Rezaei A. 2015. Groundwater qanat potential mapping using frequency ratio and Shannon’s entropy models in the Moghan watershed, Iran. Earth Science Informatics 8(1):171-186. doi: 10.1007/s12145-014-0145-7

Parks YP, and Smith PJ. 1983. Factors affecting the flow of aflaj in Oman: A modelling study. Journal of Hydrology 65(4):293-312. doi: 10.1016/0022-1694(83)90083-5

Remini B, Achour B, and Albergel J. 2014. The qanat of Algerian Sahara: an evolutionary hydraulic system. Applied Water Science:1-8. doi: 10.1007/s13201-014-0195-5

Shams A. 2014. A rediscovered-new ‘Qanat’ system in the High Mountains of Sinai Peninsula, with Levantine reflections. Journal of Arid Environments 110:69-74. doi: 10.1016/j.jaridenv.2014.06.006

Stiros SC. 2006. Accurate measurements with primitive instruments: the "paradox" in the qanat design. Journal of Archaeological Science 33:1058-1064.

Taghavi-Jeloudar M, Han M, Davoudi M, and Kim M. 2013. Review of Ancient Wisdom of Qanat, and Suggestions for Future Water Management. Environmental Engineering Research 18(2):57-63. doi: 10.4491/eer.2013.18.2.057

Wessels J. 2014. Qanats and water cooperation for a sustainable future. Middle East Institute.

Yousefirad M, Mokhtar S, and Mahbod A. 2012. The influential factors on the qanat hydrogeology. Journal of Food, Agriculture & Environment 10(2):843-848.