Qanats are a remarkable system for managing water without pumps and with minimal evaporation even when water is transferred over considerable distances. A mother well starts the qanat and then an underground canal set at a minimal pitch carries the water for many kilometers until it comes to the surface.
Some qanats were 70 km or longer.[i] The sizes of the tunnel and wells vary widely from narrow, barely large enough to fit a person, to substantial. In less consolidated materials the access shafts may need to be much larger. The spacing of the access shafts may be 20-150 m or more. The depth of the access wells can be estimated by looking at the depth of the soil cone deposited around the well and the spacing between wells. The outlet of the qanat may be very simple or elaborate.
These amazing water systems are dug and maintained with little more than a pick, shovel, baskets, ropes, and considerable courage and skill. Qanat workers, muqannis, worked in very tight spaces. Over generations they have developed an understanding of geology and engineering that enables them to manage the tunnels safely.[ii] To dig the horizontal transport tunnel (canal) carrying water a series of vertical wells are dug to remove material, provide access, and supply fresh air for diggers.
Construction of a qanat is usually performed by a crew of 3-4 muqannīs.[iii] For a shallow qanat, one worker typically digs the horizontal shaft, one raises the excavated earth from the shaft and one distributes the excavated earth at the top. A fourth may prepare food and tea.
Evidence suggests they were first used in Persia (now Iran) about 1,000 BCE. One of the most remarkable questions is who dug the first one? It is not intuitive and would have taken remarkable courage (as it does today). This system may have evolved from observations of year round water flow from mine shafts.[iv] Early farmers may have then dug their own shafts or paid miners to dig them. The technology evolved and was spread by the Persians, Romans and Silk Road and then later by the Moors, Arabs, Spanish and others. Mecca had its own qanat at times.
The relationships between land owners, qanat owners, users, and service providers are often complex and intertwined.[v] A qanat was often excavated over a long distance, covering the lands of hundreds of families with unequal shares and rights. The construction and management of qanats also evolved and changed with different rulers over the hundreds of years. Some were built with local resources, but in other cases the government invested in the construction. In many cases tax policy favored building and repairing qanats.[vi] At times a wealthy individual, village or community might invest in a qanat. A water master would often oversee water use and apportion water to users depending on the number of shares they owned or rented.
Around AD 1010, Abubakr Mohammad Karaji wrote a book on the “Extraction of Hidden Waters” discussing the technical issues associated with qanats.[vii]. He hoped to provide guidance for constructing, maintaining and repairing a qanat, how to find a groundwater supply, how to do the sophisticated leveling, etc. This important book wasn’t translated into English until 2011. Abdollah bin Tahir managed to bring together all the clergymen from throughout Khorasan and Iraq to compile a book entitled “Alghani” (The Book of Qanat).
This book took up all the rulings on qanats which could be of use to whoever wanted to judge a dispute over this issue focusing on qanat-related rulings based on Islamic principles.[viii] This was published about the same time as Karaji’s book.[ix] Eventually the understanding of qanats spread around the world and they were adopted and are still used in many countries.
Qanats are sometimes known as a chain of wells. Other names for qanats include kanat, khanat, kunut, kona, konait, ghanat, ghundat.[x] In Persian, other words for “qanat” are kārīz (or kārēz; كاريز) for smaller distribution canals, kahan, and qanāt (قنات). Called کهن) and Kahn in Balochi; kahriz/kəhriz in Azerbaijan; khettara in Morocco; Galerías, minas or viajes de agua in Spain; falaj in Arabic: فلج) in the United Arab Emirates and Oman; and foggara/fughara in North Africa. In Asia and North Africa kakuriz, chin-avulz, and mayun may also be used. A similar system was found with the puquios of Peru.[xi] This concept may have come from the Spanish in the 1500s, but a good argument can be made that it was invented locally.
For a system with such great efficiency, low cost for tools and operation, and value; (and so many names) the qanat remains little known. In Iran alone there may have been 50,000 qanats with a total length of 360,000 km.[xii] This made it possible to live in areas with little or no surface runoff.
In well-consolidated soil and subsoils test wells could be dug to find a reliable water source. These wells might be only 1 m in diameter, not for the claustrophobic. Once water was found a larger access shaft would be dug. This is considered the “mother” well. Several wells might be linked to feed the start of the qanat. Digging out in the horizontal shaft would have been challenging. By the time Kariji was working the surveying tools were quite sophisticated.
When hauling the debris back and up required too much work a new vertical shaft would be dug. These shafts might be 20-80 m or more apart and were usually not too deep, but parts of the 2,700-year old Gonabad Qanat were dug to a remarkable 300 m. Access shafts would also add fresh air for the workers. In porous soils the bottom of the horizontal tunnel would need a waterproof coating. In weaker soils wood, plaster or stone bracing might be needed for the access shafts and tunnels.
Qanats required maintenance to clear debris and keep flows steady. The debris cones made from all the excavated soil provided some protection from flood waters, but because they were often in alluvial deposits and following stream channels. They would have been vulnerable to very rare but large flash floods.
Qanats provide a low technology way to collect and move water over considerable distances by gravity. These underground aqueducts, built thousands of years ago, suffer almost no evaporation loss. The qanat water was split into a distributing network of smaller underground canals called kariz when reaching villages or cities.[xiii]
Like qanats, these smaller canals were below ground (perhaps 20 steps), and were built in ways that protected them from contamination. They could provide clean drinking water and a relatively steady flow of water. Qanats are ideal for dispersed rural populations and villages with low population density and steady water demand during the year.[xiv] Larger qanats also supported larger towns and extensive farming. Smaller qanats may service just a couple of fields
An Example: Zarch Qanat[xv] Length 80 km, greatest depth 90 m
The town of Zārch is located in Yazd Province, Iran. This arid area has low precipitation, high temperatures and high evaporation. There is no permanent river or surface runoff so groundwater is the only resource for much of the year. Seasonal runoff enters the area from the northern foothills of Siyah Kuh mountains. The mother well of the Shur branch is 3 km from Fahraj village in SE of Yazd at a depth of 90 m. It provides about 25 liters/second.
The qanat has three branches, but only the Shur one is operational. The horizontal tunnel is 1.8 m tall and 60 cm wide. The gradient is about 0.5° The qanat provides water for 300 ha of farms. The water is delivered to farmers once every 15 days. The qanat is owned by the farmers managed by a council. Shares can be rented.
Looking for qanats with Google Earth is instructive. A good place to start is around Yazd, Iran.
Try going to 31° 47.517’N 54° 36.565’E for starters. Several small and large qanats are visible.
In Iran the cool air delivered in the horizontal well is used to cool buildings.[xvi] This enables air cooled by evaporation to be drawn up into the building by out flow from the downwind side, exhaust into the low pressure area of the wind tower (bâdgir) and pressure on the upwind side. In some cases the qanat flow is used to operate a small water mill to grind flour.[xvii] These were not large but could operate year round with little effort or attention.
Qanat Tourism – A Promising Venture
Cities such as Yazd, Kashan, and Gonabad have well-preserved qanats that still serve as functional water sources and cool buildings. They also offer unique tourist experiences.[xviii] A beginning effort is bringing tourists to some of the qanats, including a walk in the horizontal channel, marvel at ancient qanat structures, and the opportunity to witness traditional qanat maintenance techniques. Additionally, some tour operators offer experiential activities such as qanat hiking, where participants trek along qanat routes and discover hidden water sources and natural landscapes.
Qanats are a remarkable and sustainable water management technology that could help revitalize many desert locations around the world. They can help provide drinking water and some irrigation water in arid zones with no surface water and move water without electrical energy, fossil fuel driven pumps, and very low evaporation losses. Classes or workshops taught by the muqannis could help introduce qanats in other areas. Universities might consider adding certificate programs for qanat building and maintenance.
References
[i] Traditional water sources of Persian antiquity. Wikipedia. https://en.wikipedia.org/wiki/Traditional_water sources_of_Persian_antiquity Accessed January 20, 2025
[ii] Nasiri, F., Mafakheri, M. S. Qanat water supply systems: a revisit of sustainability perspectives. Environ Syst Res 4, 13 (2015). https://doi.org/10.1186/s40068-015-0039-9
[iii] Qanat. Clean River Trust.
[iv] Semsar Yazdi, A. A. and Askarzadeh. S. A historical review on the qanats and historic hydraulic structures of Iran since the First Millenium BC. pp. 311-322. International History Seminar on Irrigation and Drainage Tehran-Iran May 2-5, 2007. Iranian National Committee on Irrigation, and Drainage-International Commission on Irrigation and Drainage. ( 2007)
[v] Kobori, I. Some notes on the diffusion of the qanat. Orient 9:43–66 (1973)
[vi] Saatsaz, M. and Rezaei, A. The technology, management, and culture of water in ancient Iran from prehistoric times to the Islamic Golden Age. Humanities and Social Sciences Communications. 142: 1-22. (2023)
[vii] Ataie-Ashtiani, B. Simmons, C. T. The millennium-old hydrogeology textbook The Extraction of Hidden Waters by the Persian mathematician and engineer Abubakr Mohammad Karaji (953 CE–1029 CE) Hydrology and Earth Systems Science.. 24, 761–769, 2020 https://doi.org/10.5194/hess-24-761-2020
[viii] Semsar Yazdi and Askarzadeh (2007)
[ix] Litwin, D. The Extraction of Hidden Waters: 11th century Persian scientist laid the foundations for hydrology and water engineering. Geobites. Jan 26. (2020)
[x] Qanat. Wikipedia
[xi] Proulx, D. A. Nasca Puquios and Aqueducts. Originally published in German in: Nasca: Geheimnisvolle Zeichen im Alten Peru, edited by Judith Rickenbach, Pp. 89-96. Zürich.
[xii] Salih, A. Qanats a unique groundwater management tool in arid regions: The case of Bam Region in Iran. pp. 79-87. In International Symposium on Groundwater Sustainability (ISGWAS), January 2006.
[xiii] Qanat and Kariz. Traditional water sources of Persian antiquity. Wikipedia. Accessed Jan 24, 2025.
[xiv] Motiee H, Mcbean E, Semsar A, Gharabaghi B, Ghomashchi V. Assessment of the contributions of traditional Qanats in sustainable water resources management. Water Resources Development 22:575–588 (2006)
[xv] Zarch Qanat World Heritage Irrigation Structures, ICID_CIID, New Delhi. https://icid-ciid.org/award/his_details/136.
[xvi] One of my students complained that it made for buildings that, for her, were too cool.
[xvii] Yazdi, A. A. S. and Khaneiki, M. L. Barriers and limitations on qanat construction and rehabilitation. pp. 77-97 in Qanat Knowledge. Springer, Netherlands.
[xviii] Raheleh. Exploring Iran’s Ingenious Water Management System: The Persian Qanat. June 15, 2024. Accessed January 21, 2025. https://www.adventureiran.com/persian-qanat/.