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Qanat

Qanat


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The qanat (called foggara in North Africa and the Levant, falaj in the United Arab Emirates and Oman, kariz in Iran, and puquios in Peru) is an ancient Middle Eastern irrigation technique in which a long tunnel is dug into arid land that allows water from underground aquifers to be accessed for use by the local population, supporting large settlements in spite of hostile environmental conditions. Qanats begin as deep wells dug into elevated land and culminate in streams flowing through outlets into a human settlement. Outflows sustain settlements by providing water for crops and drinking water for the population. Powered only by gravity, these simple wonders of ancient architecture allowed settlements in arid climates to have dependable access to water, sometimes for centuries at a time. Today, tens of thousands of qanats still function in around 35 countries across the globe.

Origin & Spread of Qanats

Qanat is Arabic for 'conduit,' and is the most widely-used term for the irrigation system among English-speakers. The earliest examples of qanats have been found in ancient Persia, modern-day Iran, Arabia, Iraq, and Turkey, with the most commonly-held view being that qanats are one of the inventions and innovations of ancient Persia and were spread throughout the region during the expansion of the Achaemenid Empire (c. 550-330 BCE). This view was also held by the ancient Greek historian Polybius, who wrote:

They say that at the time when the Persians were the rulers of Asia they gave to those who conveyed a supply of water to places previously unirrigated the right of cultivating the land for five generations, and consequently as the Taurus has many large streams descending from it, people incurred great expense and trouble in making underground channels reaching a long distance, so that at the present day those who make use of the water do not know whence the channels derive their supply. (The Histories X.IV)

However, an emerging view is that qanats originated in Southern Arabia (modern-day Oman and UAE) and were then either spread into Persia (modern-day Iran) or developed in Persia independently. Regardless of the qanat's exact place of origin, archaeological evidence suggests that settlements as old as 1,000 BCE were dependent upon qanat systems of irrigation, meaning that qanats are at least 3,000 years old.

The source of a qanat's water supply is groundwater, rather than a lake, river, or spring.

Historians disagree on the developmental trajectory of qanat technology throughout North Africa and the Mediterranean region in the years following the Achaemenid Empire, with some claiming independent development, some a Mediterranean path, and others a Saharan path. Those who claim that independent development occurred suggest that qanat technology was a natural response to the arid conditions found in North Africa, the Sahara Desert, and across the Middle East. This idea allows for technological diffusion as well, acknowledging the spread of qanats into Europe and throughout the Middle East as a result of connection.

The Mediterranean path of development suggests that conquest and resettlement were the driving forces behind the spread of this technology. The Romans learned from the Persians, and later conquered North African territories, introducing the learned technology to these arid regions from across the Mediterranean. Meanwhile, Persians seeking refuge fled across the Sahara, bringing their technological advancements with them.

Finally, the Saharan path of development suggests that qanat technology spread westward into North Africa from the Achaemenids to Egypt to Libya and Algeria, then finally northward into the Roman Empire and continental Europe. Whatever the western trajectory of the technology may have been in the years following the Achaemenid Empire, scholars generally agree that qanats in the Americas were the result of Spanish colonization, and the eastern diffusion of qanats into Afghanistan, Pakistan, China, and Japan was the result of interconnectedness along trade routes, particularly the Silk Road.

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Qanats are similar to other aqueducts found in ancient civilizations in that they carry water through underground tunnels; however, they differ in that the source of a qanat's water supply is groundwater, rather than a lake, river, or spring. For example, the Neo-Assyrian Empire (912-612 BCE) developed a river-fed system of aqueducts that even included the same type of vertical ventilation shafts found in qanats. Tunnels and canals were added to this system over time by famous kings such as Ashurnasirpal II, Tiglath-Pileser III, Esarhaddon, and Sennacherib. Contemporaries of the Assyrians, such as Israel, also built similar underground aqueducts. In Israel, King Hezekiah oversaw the construction of a conduit supplied by an underground spring. Even the renowned Roman aqueducts were mostly fed by springs and rivers until adopting qanat technology in their Middle Eastern and North African territories. It was the use of groundwater that separated qanats from their counterparts.

Building Qanats

The sustainability and longevity of a qanat are owed to its design. In ancient Iran, qanats were built exclusively by muqqanis, professional traveling Persian craftsmen. These ancient architects would first identify an alluvial fan as a source of groundwater, then dig a 'mother well' to reach the water table. These wells often would be nearly 100 meters (328 ft) deep, with the deepest recorded well measuring at 300 meters (984 ft). If the aquifer yielded sufficient water, the muqqanis would begin plotting the course of the qanat from the mother well to the surface. The builders would take into account the gradient of a downhill slope so that water flow remained consistent but did not stir up sediment or damage the tunnel.

Once the course had been plotted all the way to the mouth of the tunnel, the muqqanis would begin digging ventilation shafts regularly along the charted course of the qanat. Not only did these shafts provide ventilation for the diggers but they also served as guides for the diggers as they excavated the tunnel. Excavation began at the mouth of the tunnel, where the walls were often reinforced with stone, and moved upstream, eventually reaching the mother well and the aquifer. Once the qanat had been completely excavated, construction was complete; however, the muqqanis continued to work, providing maintenance to ensure the qanat remained functional over time. Such techniques have remained the standard of qanat construction across the world for millennia, as recent qanats have been built using similar methods.

Qanats could be as short as 1 km (3,280 ft) or as long as 50 km (31 mi), but they always attracted settlers with a consistent water supply. In many cases, the qanat could be used to identify social status. The elites often settled the upper sections near the mother well, while the poor settled near the lower section, where water flows were lesser and water was more likely to be polluted by those upstream. Despite the drawbacks of being located near the mouth of the qanat, the poor could still rely on a consistent supply of water, as evaporation occurs at a much slower rate in underground conduits. This advantage, in addition to its dependence solely on gravity as an energy source, made the qanat an ideal solution for ancient settlements in arid climates. Its reliability and environmental sustainability have even brought it renewed attention from modern climate scientists.

Impact of the Qanat

Despite advancements in technology over time, qanats have remained a reliable source of water for Iran from the first millennia BCE to the present time.

The Middle East is one of the driest areas in the world, containing regions where rainfall remains below 50 mm (1.9 in) annually. Such low levels of water supply are incapable of sustaining a growing population, which is why the Persians found such an innovative way to access groundwater. Despite advancements in technology over time, qanats have remained a reliable source of water for Iran from the first millennia BCE to the present time. Today, there are still over 30,000 qanats in Iran. Even now, these qanats bring substantial water supply to compensate for the lack of rainfall. For example, the Gonabad qanat system in Khorasan Province was built around the 6th century BCE by the Achaemenids, yet this long complex of tunnels, wells, and outlets remains in use today. Outlets extending from the Gonabad system can discharge up to 150 l/s (39 gal/s), allowing for the irrigation of 150 hectares (370 acres) of agricultural land. Likewise, over 3,000 qanats in Yazd are still functioning today. Some are over 1,000 years old. The Yazd qanats discharge around 340 million cubic meters (over 92 billion gal) of water each year, supplying around 25% of the province's total groundwater. This is an amazing accomplishment considering the 60 mm (2.4 in) of total rainfall that Yazd receives each year.

Qanats have also made an impact on water supply and irrigation in arid regions outside of Iran as well. One such example lies in the Turfan (or Turpan) Basin of Xinjiang, China. The Turfan Oasis qanat system provides water to the Turfan Basin from the Tianshan Mountains. The Turfan Basin, located in Western China, is a dry desert climate that averages only 17 mm (0.67 in) of rainfall annually. However, through the use of over 1,000 qanats, the Turfan Basin can receive an additional 150 million cubic meters (39 billion gal) each year. The constant water supply provided by the qanat system supports a sizable population and allows for substantial irrigation in an area that would be otherwise uninhabitable.

Legacy of the Qanat

The reliable supply of water made possible by qanat technology helped transform the Middle East and contributed to globalizing trade routes by allowing settlements and trading posts to be established in the arid regions of the Middle East, North Africa, and Western China. Additionally, qanats brought societal change through the establishment of the practice of sharing and managing water resources flowing from the qanat. Because of qanats, areas far removed from oceans and seas with scarce rainfall and river water also have been able to support population growth in an environmentally sustainable and energy-efficient way since ancient times, inspiring modern experts in their quest to help modern society adapt water production systems to meet the needs of an expanding global population.


Zarch Qanat, Yazd

Qanat of Zārch is a plain qanat with a gallery length of 80 km, its mother well is 90 m deep and has more than a thousand well shafts. It is still functional despite the sharp decline in the aquifer’s water levels. According to the existing documents, this qanat dates back to preIslamic Era. History books too, indicate that this qanat had been running across Yazd city about 700 years ago and people used its water for drinking and sanitation purposes through pāyābs which are a kind of access corridors.

The starting point of this qanat is in a village of Fahraj located in the north east of Yazd. The qanat runs at the depth of 30-40 m beneath the city of Yazd. Then it reaches Zārch, where the water is used for irrigation in lower lands of the city of Yazd.

The history of Qanat of Zārch can be studied in terms of the formation of Zārch city, the age of the hydraulic structures built over it and in terms of existing historical documents. The history of Zārch city not only can be found in history books, but also myths, fables and epic stories mention it frequently, all of which are indicative of its long history. Now if we consider this qanat as the factor behind the formation of this city, it is as old as the city itself.

The study of the history of Qanat of Zārch shows that it has been frequently mentioned in various references. A sample of this references is a history book written by Ja’fari in the 1500 AD. This historian writes: “Qanat of Zārch enjoys two branches, one is outside the city and the other flows into the city. It is one of the oldest qanat. During the invasion of the enemy forces, when they surrounded the city and blocked the water resources, it was the only water resource for the residents. To access water, people have to climb down 70 steps. Although it tastes a little bit salty, when it is cold it tastes fresh”.

The hydraulic structures built over or close to this qanat are another proof for its long history. Based on the results of studies conducted, some of the well shafts date back to pre-Islamic Era. The sections of these well shafts are rectangular in the bottom. Experts maintain that such well shapes were mostly common during Zoroastrian period, and in local dialect such well shafts are known as “Gabri” (Zoroastrian) wells. In addition to qanat itself, some of the pāyābs in this area are very old and their names have been mentioned in history books. The book entitled The New History of Yazd holds that the pāyāb of Masjed-e Jāmé Yazd has been constructed during Alaud-Daulla reign in 1480 AD.

The archaeological researches conducted about Qanat of Zārch attribute it Archimedean Era. The bricks of 40×40×10 cm thickness obtained from the remains of Zārch castle belong to Archimedean Era.

Some ceramic pieces belonging to Sassanid Period have also been found in the upper parts of Qanat of Zārch. If we place the records for the formation of Zārch city beside other historical references, we can conclude that the age of this qanat most likely goes back to pre-Islamic Era.

Needless to say that this qanat has been fully operational during 1200-1300 AD supplying potable water for the people of Yazd, meanwhile the residents of Zārch used its water for irrigation, sanitation and consumption purposes. Therefore, this qanat is among the oldest qanats.

On the other hand, this qanat enjoys numerous pāyābs, some of which are very old. The New History of Yazd, as a sample of numerous history books says that Alaud-Daulla ruler of Yazd had a Masjed-e Jāmé built in Yazd and beside it a pāyāb to access the water of qanat. “And Alaud-Daulla constructed a mosque where Arsalān Khātun had constructed the minaret and beside the minaret built a dome, then he joined a branch of Zārch to the back side of the masque.


SH Archive Qanat Tunnels, UNESCO World Heritage Sites

A qanat tunnel near Isfahan

Cross-section of a Qanat

KD Archive

Not actually KorbenDallas

Archive

SH.org Archive

Feralimal

Active member

The thing that struck me, is why the need for shafts at all? If they worked backwards into the water table they could get the slope they needed.

The page says the shafts are essential, and a distinguishing feature. I don't doubt it. I just wish they would say why!

While you might dig one shaft to confirm there is water where you expect (like a well), the rest of the shafts sound like extra work!

Anyway, what do I know! There probably is a good reason, but I don't get it from wiki. No change there then!


See the Ancient Water Tunnels Below Iran's Desert

The combined length of the thousands of tunnels is about the same as the distance between the Earth and the moon.

Beneath Iran's Dusty Desert Lie Ancient Water Tunnels Still in Use

From above, it seems as though a series of holes were pierced in the desert’s dry surface. But a hundred feet below the mysterious pits, a narrow tunnel carries water from a distant aquifer to farms and villages that wouldn’t exist without it.

These underground aqueducts, called qanats, are 3,000-year-old marvels of engineering, many of which are still in use throughout Iran. Beginning in the Iron Age, surveyors—having found an elevated source of water, usually at the head of a former river valley or even in a cave lake—would cut long, sloping tunnels from the water source to where it was needed.

The orderly holes still visible aboveground are air shafts, bored to release dust and provide oxygen to the workers who dug the qanats by hand, sometimes as far as forty miles. The tunnels eventually open at ground level to form vivid oases. (Watch: the secret history of saffron, the world's priciest spice.)

Constructing qanats was a painstaking task, made even more so by the need for great precision. The angle of the tunnel’s slope had to be steep enough to allow the water to flow freely without stagnating—but too steep and the water would flow with enough force to speed erosion and collapse the tunnel.

Although difficult work—even after completion, qanats require yearly maintenance—the irrigation tunnels allowed agriculture to bloom in the arid desert. The technology spread, through Silk Road trade and Muslim conquest, and qanats can be found as far as Morocco and Spain. (Read about the Persian legacy in modern Iran.)

For Komeil Soheili, an Iranian filmmaker who produced the video above, qanats are an integral part of the landscape of his native Khorasan Province.

“The diversity of landscapes and cultures [in Iran] is something that’s not well understood by the world,” Soheili says. “One of the oldest civilizations in the world came from this amazing creation, [the qanat.]” (See some of Iran's most wild and beautiful places.)

Gholamreza Nabipour, 102, is one of the last and almost certainly the oldest mirab, or caretaker of qanats. Recognized by the Iranian government as a national living treasure, Nabipour tries to share his craft with younger generations—including one of his sons, who uses a qanat to irrigate his pistachio farm—but fears for the future of this fragile tradition. (See Iran's centuries-old windmills in action.)

In the 1960s and 1970s, the subdivision of the large estates that relied on qanats caused an administrative tangle, and many qanats fell into disrepair without the traditional communal maintenance. And as modern agriculture takes root, Soheili explains, “people don't depend on qanats anymore, as it was before. It’s not possible to feed your family and earn money by working in qanats,” which have become less a way of life and more of a “hobby.”

In 2016, UNESCO listed the Persian qanats as a world heritage site.

“These qanats have been the source of life for me and all of my ancestors,” says Nabipour in the video. “It’s my duty to preserve them until the last second of my life.”


Qanat - History

Qanats were studied in the mid-1990s in Syria as pan of a broader project examining the role of qanats in a modern world. Fieldwork was conducted in winter 1993 and summer 1994 in order to determine the distribution and status of qanats throughout Syria evaluate the historic role of these qanats, determine why qanats were built where they were, why their use has so dramatically declined in recent decades, and what impact these changes have had on Syria's ground-water resources. Empirical and secondary data were collected from documents, field reconnaissance (qanat visits and tunnel exploration), and interviews with resources officials, felaheen (peasant/farmer) union members, and mukhtars (town or village advisors).

Figure 1. Distribution and status of Syrian qanats (as of 1994).

Click on the image for a larger version.

Qanats have been used in Syria to irrigate fields and gardens for centuries, and many of these - especially around Damascus, Selemiya, Palmyra, Qadeym, and Taibe - have been examined in some detail in published reports. There are many others scattered across the Syrian landscape which have never been described in written accounts, yet nevertheless have provided an important source of irrigation and drinking water for dozens of isolated settlements, even in areas where no surface water is available.

Existing records show that qanats were in use in Syria (and elsewhere in the Roman world) by Roman times, about 2000 years ago (Caponera, 1954, p. 45), and Syrians still refer to these features as 'qanat Romani' (Roman canals). So we know that there were qanats in Syria at the time of the Romans, but that doesn't mean that all Syrian qanats were built by Romans and then cleaned/maintained from that time forth.

The diversity of qanat types seems to reflect a great variety of origins. For example, engineering and architectural forms associated with qanat shafts and vent openings are not consistent (e.g. masonry or dirt in shaft and around vent shoulder variations in diameter and spacing), qanat tunnels vary widely in design (e.g. height and width oval to rectangular profiles natural interior or various forms of wood, masonry, brick, or cement casing continuous gradient vs. the floor of the tunnel excavated to create one or more subterranean reservoirs in line with vertical shafts), and the water may exit to flow into a canal, a birka (small reservoir or holding tank for irrigation water), or a large well.

Syrians today refer to all qanats as 'Roman canals', or 'qanat Romani'. The term 'Romani' in Syria is commonly applied to Roman features, but it can also be interpreted to mean 'pre-Islamic' or simply 'old', and not necessarily 'Roman'. There is some evidence that the first Syrian qanats were pre-Roman.

Some historians have maintained that the Hailan-Aleppo qanat, a 12-km long subterranean channel which still functioned until the early part of this century, is coeval with the Aramaeans and their fortress at Aleppo (13th century B.C.) (Russel, 1794, p. 42). However, this is highly unlikely as the best evidence (archaeological and written accounts) suggests that qanat irrigation was first invented in the Armenian-Persian region about 600-700 B.C. Some scholars have suggested that qanats were originally introduced in Syria by the Persians, when Syria was incorporated as a province within their empire in the 6th century B.C. Persians had already used qanats nearby to open up the water supply for Egypt's Kharga Oasis by about 500 B.C. (Forbes, 1964, p. 183), and ancient Persian potsherds found inside qanats in the Arava Valley, in the Israeli Negev, suggest that these qanats were first constructed during the Persian rule of the Holy Land (537-332 B.C.) (Evenari et al., 1971, p. 178 Ron, 1989, p. 219).

Goblot (1979, p. 132) asserts that, regardless of who later built the majority of Syria's qanats, this technology had already been transferred to the area by at least the 2nd century B.C., placing qanats contemporary with the Greeks in Syria. A historian from Selemiya (Syria) maintains that the first qanats in that area were built by the Greeks (with most of them built later by the Romans) (Amin, 1993, pers. comm.), though evidence for this is circumstantial and not artifactual. The Greeks adopted Near East water technologies and freely applied them where they settled the first conduit supplying Athens with water from Mt. Pentelicus was a qanat-type channel (Sandstrom, 1963, p. 60 Forbes, 1964, p. 164). That the Greeks borrowed this technology from the Persians is almost certain that they applied it to Syria and built qanats there is not. There is no material evidence that the Greeks -or the later Hellenized Seleucids - constructed any of Syria's qanats, and few places in Syria settled during the Greek or Seleucid periods are even near qanats.

It is certain that many of Syria's qanats were first constructed during the Roman- Byzantine era. The Romans (64 B.C. to A.D. 330) and their eastern Roman empire successors, the Byzantines (A.D. 330-630) gave Syria a great number of aqueducts and wells, many of which are still in use, and generally improved irrigation techniques and expanded arable land in the region. Numerous pottery fragments, oil lamps, and other artifacts found in qanats have clearly shown that qanats in this region date from Roman times (Reifenberg 1955, p. 54 Puller, 1986 Fuller, unpublished Ph.D. dissertation). Other archaeological evidence (e.g. inscriptions, putei (surface shafts), Roman wells at qanat termini) and historic records show that the Romans constructed qanats in Syria, Jordan, Tunisia, and other places throughout their empire (Caponera, 1954 Goblot, 1979 Fuller, 1986, 1987 Fleming & Barnes, 1993). Syrian qanats also show a high degree of spatial correlation with Roman-Byzantine sites. Almost 40% of these qanat sites are found within or adjacent to (former) Romano-Byzantine towns or fortified villages, and another 50% are sited in the immediate vicinity of smaller Romano-Byzantine outpost or guardhouse ruins (Fig. 2 ). Because the supporting evidence is strong, most scholars believe that the majority of Syrian qanats were first built by the Romans and Byzantines in the first to seventh centuries.

There exists good evidence that some of the qanats we see in Syria today were built by other (post-Roman/Byzantine) groups during periods of relative prosperity (Moussly, 1951, p. 146). Although many qanats in Syria are located near Romano- Byzantine outposts or guardhouses, it is not likely that very labor-intensive qanats were routinely built to supply drinking water or support agriculture around these small, often temporary outposts. Furthermore, a few qanats in Syria exhibit no association with arable land in the immediate vicinity of Roman or Byzantine sites, offering further evidence that some of Syria's qanats were built by post-Roman, Islamic groups.

A number of scholars have attributed some of these qanats to the Umayyad caliphate (A.D. 661-750), when the Islamic empire was at political and geographical zenith (Sourdel, 1968 Goblot, 1979 Kobori, 1990). Damascus, as the capital of this empire, achieved a glory unrivaled among cities of that period, Syria became the most prosperous province of any Islamic caliphate, and agricultural production was expanded throughout much of the region (Goblot, 1979, pp. 127-132 Collelo, 1988, p. 10). Most of the sites associated with qanats were occupied and farmed during this period, and Umayyad architecture was added to that of the Romans and Byzantines at Damascas, Aleppo, Rusafah, Qasr el-Hayr, Hawarin, and other places in Syria where qanats are found (Sauvaget, 1939). The Umayyad contribution to Syria's qanats is further suggested by interior tunnel casings and birkas (reservoirs) of 7th century Umayyad design at qanat sites around Amsareddi and Qasr el-Hayr, among others (Kobori, 1990, pp. 323-324).

By A.D. 750 the Islamic Abbasids had conquered the Umayyads and established the caliphate in Baghdad. Syria was reduced to a province within this empire, yet the Abassids continued to develop Syria's resources (Goblot, 1979, p. 129 Collelo, 1988, p. 12). These Islamic empires brought Syria into frequent contact with Persia(ns) - where qanats originated and where they were still being built in great numbers - which surely contributed to the post-Roman construction of qanats in Syria, and Islamic peoples are known to have built qanats in other parts of the Middle East and North Africa in the post-Roman era. The diffusion and historic utilization of qanats in the Old World -from the Iberian peninsula to central Asia -mirrors the historic dispersal of Islam.

Once built, these ancient qanats were sometimes maintained throughout the centuries by periodic cleaning (removal silt/debris from the qanat tunnel in a schedule which varies according to the soil and configuration of the land), repairing the well entrances and shafts, and sometimes deepening the mother well or extending collecting galleries further into the aquifer in an attempt to increase the flow of qanats. In other cases, Roman-Byzantine or Umayyad-Abassid qanats fell into disrepair as these empires waned, only to be cleaned and repaired at a later date as people moved back into abandoned sites refurbished with funds from state or local administrative coffers, or (more often) through the efforts of village cooperatives or wealth) landowners. Some of Syria's qanats were repaired and extended in the 1930s by the Mandate French authorities. A few of the many qanats around Selemiya may even have been built in the late 19th century by Ismailis (a Shia Islamic sect) who settled in the region in the 1870s (Lewis, 1949, p. 286 English, 1968, p. 176). Some landowners within the Ghouta of Damascus have not only continued to preserve and operate ancient qanats but, at least as late as the early 20th century, constructed new qanats (Tresse, 1929 Goblot, 1979, p. 127).

Because qanats must be constantly repaired in order to maintain water flow, the appearance of a qanat may change over time, as tunnels are reshaped, shaft openings are lined with masonry or bricks, or birkas are incorporated into the qanat channel or at its terminus. While some of these additions are clearly recent (and documented as such), many historic modifications cannot be distinguished from original qanat construction. As culture after culture replaced the one which preceded it, each added its own qanats to those already built, and/or refurbished earlier qanats according to its own designs, leading to the great variety of engineering and architectural forms we see in the qanats today. Many of Syria's qanats lay abandoned for centuries early European travelers to Syria described dead qanats in accounts of their 18th and 19th century travels (Creswell, 1932, p. 342 Goblot, 1979, p. 128). Many more have been abandoned in the latter half of this century as water tables have fallen since the introduction and widespread use of electric and diesel-pumped wells.

Figure 2. Relationship between qanat sites and Romano-Byzantine sites.

Click on the image for a larger version.

Regardless of who built qanats in any region of Syria, they were all constrained by the same physical environment which limited useful qanat construction to a relatively small number of locales. In the following sections the relationship of qanat sites to rainfall, evapo-transpiration, topography and geology will be examined, to see if there are any consistent patterns in the siting of Syrian qanats, in order to understand why early engineers built qanats where they did.

Most qanats in Syria (75%) were constructed within semi-arid regions receiving 100-300 mm average annual precipitation, and all are found at or below the 500 mm isohyet. This also mirrors the pattern in Iran, where the major qanat systems are found where precipitation totals range from 100-300 mm per year (Beaumont, 1989, p. 27). People in wetter areas - where perennial streamflow is adequate - rarely built qanats, and drier regions were inhabited by nomadic Bedouin herdsmen not inclined toward irrigation-dependent sedentism. In this century, however, many Bedouin have moved into permanent settlements and have refurbished or re-opened some long-abandoned qanats in eastern Syria.

Regardless of incoming precipitation, the potential for evapo-transpiration (Et) will affect the evaporation of surface water, so areas with increasingly higher potential Et would gain an incrementally greater advantage by relying on the subterranean waters of a qanat. Annual precipitation is lower than potential Et throughout Syria - i.e. the entire country experiences water deficit - and the driest areas of the country, with the greatest discrepancy between incoming precipitation and potential Et, are where qanats are found in abundance. Qanats were mostly built within the region of 1600-2800 mm potential Et and where potential Et is 4 to 20 times greater than average annual precipitation. Almost one-half of the qanat sites are found in hyper-arid regions where potential Et exceeds precipitation by a factor of 10 to 20.

The chain of wells associated with a qanat usually runs across relatively flat terrain, though often adjacent to, or even surrounded by, mountains or hills. Qanats commonly tap into shallow aquifers (alluvial fans or synclinal bedrock) at the base of these hills or mountains, or along the margins of larger wadis (stream channels) coming out of the mountains. Therefore, there is a close relationship between qanats and mountains/hills almost 90% of Syria's qanat sites lie within 25 km of uplands, and 75% lie completely within piedmont slopes at elevations of 500 to 1000 m. Some of the qanat sites which appear beyond the piedmont zone actually lie at the base of low escarpments. Furthermore, the collecting galleries of qanats at the base of larger hills/mountains often tap into water tables adjacent to the large wadis which flow out of these highlands, so there is a great mix of piedmont and wadi aquifers feeding all of these qanats, yet each of these aquifers is recharged with precipitation primarily falling in the uplands. Where ground-water water is available farther out from the uplands, it tends to be brackish and otherwise of poorer quality than water found in or very near the mountains, where the water has not yet been adulterated by salt, silt, or other impurities. Thus, the uplands supplied qanats with both a greater quantity and quality of ground-water, and they were rarely built beyond the montane-piedmont zone.

To ensure long-term, perennial flow from a qanat, and thus an adequate return on the investment in time and money required to construct qanats, they were constructed to exploit aquifers that are seasonally recharged. These aquifers usually are shallow - a few meters to tens of meters deep -and located in areas of permeable rock, thus allowing regular recharge to the aquifer below. Qanats were not built in regions with impermeable surface materials. In most of the steppe and desert regions of Syria, deposits of calcium carbonate and silica form impervious layers beneath the permeable marly and calcareous formations nearer the surface (Reifenberg, 1955, p. 53). It is in regions with these conditions that the Roman and Islamic empires exploited the water-bearing strata to build qanats tunneling most of their qanat channels through solid beds of chalk and limestone.

The nature of the subsurface waters tapped by a qanat can, and has, changed. Land reform and the infusion of new technology have, since the 1950s, radically changed water needs and perceptions regarding the utility of qanats. Heavily irrigated export crops and poorly regulated tube wells have led to rapidly falling water tables. There are many reasons why a qanat may fall into disuse some physical, others purely social or economic in nature. In the end, environmental and cultural forces all converge to replace the old with the new, and qanats continue to be abandoned as a result.

The inside of old qanat tunnels may become choked with calcareous deposits, and/or the interior of the mother well and feeder wells become coated with mineral deposits, which reduces water seepage from the aquifer. Qanats may be abandoned if they are severely damaged by earthquake or flood, or if a major portion of the channel collapses during cleaning operations - which is increasingly common where dynamite has replaced picks and shovels for qanat maintenance (more prevalent in the Maghreb than the Middle East).

More commonly, qanats are abandoned as the water table falls, which in recent times has resulted as newer and expanded irrigation systems have over-used ground- water. This has occurred not only in hilly areas where qanats tap into small, perched aquifers, but even across expansive plains (e.g. the Selemiya Plain, where large, regionally-scaled aquifers, now severely drawn down, once fed an expansive qanat network) .The greatest impact on qanat systems worldwide has been the introduction and widespread use of the pumped tube well, mostly since the 1950s. Electric and diesel-pumped wells offer advantages over qanat irrigation by allowing water to be brought to the surface on command, and the depth of tube wells can be easily extended to increase the supply of water during droughts. But exponential growth in the number of pumped wells has, in recent decades, induced its own form of ground-water drought. Overpumping from tube wells has caused water tables to fall and qanats to be abandoned at an accelerating pace in Pakistan, Iran, Oman, Jordan, Syria, Morocco, and many other places (Beaumont, 1968, 1973, 1989 Kobori et at 1980 Allan, 1982 Birks, 1984 EWers & Saidi, 1989 Achakzai & Toor, 1990 Safadi, 1990 Simarski, 1992 Lightfoot, 1996, in press).

Many of the people interviewed at qanat sites in southern Syria (roughly from Ghunthur and Qaryateyn to Damascus) attribute qanat desiccation to a combination of overpumping and diminished rainfall. Annual rainfall in this Anti-Lebanon Mountains region of Syria has slightly diminished since the 1960s, reducing recharge to aquifers east of this range. However, while a more 'normal' rainfall rate would certainly have reduced the impact of overpumping on qanats, it could not have prevented some diminution of flow and at least limited desiccation in this region where the unchecked growth of diesel and electric-pumped wells expanded from a few dozen in the 1950s to about 6400 in the 1980s (about 3900 in the Ghoutas of Damascus and another 2500 in the region from Ghunthur to Haleh (see Fig. 1 ).

Figure 3. Relationship between qanat sites and surface geology (permeable vs. impermeable materials).

Click on the image for a larger version.

Qanat irrigation often expanded coincident with the growth of ancient settlements. Smaller settlements, supported originally by perennial surface streams or springs, sometimes augmented their water supplies with qanat waters, becoming larger and more prosperous as each new qanat tunnel allowed them to increase agricultural production, commercial activity, and even political power (Huntington) 1945) p. 540). When sites associated with the construction of qanats disappeared (e.g. because the Roman-Byzantine or Umayyad-Abassid settlements broke down as these empires waned), and the routine maintenance required to keep qanats flowing ceased) they were abandoned.

More recently) the adoption of newer technologies has altered the political and social land-use patterns which evolved through historic reliance of villages on qanat waters. For example, qanats and their waters are usually publicly operated and collectively maintained (Caponera, 1954) p. 46) p. 84 Sutton) 1984) p. 9 Dutton) 1989 Achakzai & Toor) 1990, p. 289 Lightfoot, 1996). Intricate relationships have evolved to manage these waters and distribute them according to each individual shareholder's inputs of land, labor, tools, and money. Mechanically-pumped wells are often privately owned, and, as a result, the traditional 'ties that bind' in village society are breaking down. Furthermore, the majority of qanat shareholders are small landowners who do not possess sufficient resources to complement the scarcity of qanat water by excavating tube wells (Achakzai & Toor) 1990) p. 289). Yet many land owners and farmers now widely prefer pumped wells and allow their qanats to languish.

This scenario has effected change in Syria, where new land reforms since the late 1950s have redistributed property and improved the security of land tenure (except for the bourgeoisie), thus increasing the number of farmers and farm cooperatives, and encouraging capital improvements to farm lands (Keilany, 1980). The result has been a rapid increase in the number of electric and diesel-pumped tube wells, and an expansion of surface irrigation systems, fed mostly by the Euphrates, Khabur, and Orontes rivers. Most of these newly irrigated lands are found in eastern and southern Syria, where annual precipitation is less than 200 mm, where wheat and barley are now produced for export, and in the 200-400 mm isohyet zone of central and northern Syria where cotton production has increased geometrically.

Landowners of the village where qanat waters arise may be loath to let the water flow away to the lands of another village, and may favor replacing qanats with more localized schemes, such as pumped wells, so that they, and not others, derive benefit from the waters which lie beneath them. In effect, the traditional sense of water resources management for the benefit of the community seems to be giving way to an 'every man for himself' mentality. Communities that depend on ground-water supplies, and have been able to sustainably manage these resources for centuries, could -and should -incorporate an element of cooperative water management into their modem schemes.

Finally, non-farm sources of income continue to draw people away from the villages, which disrupts the social organization of qanat systems (Birks, 1984, p. 29 Suttorn, 1984, p. 11 Achakzai & Toor, 1990 Lightfoot, 1996). For example, as more of the working-age men move out of villages in search of higher paying jobs elsewhere, membership in the cooperatives responsible for qanat maintenance dwindles to a few, dozen (mostly) elderly men, and qanats silt up or otherwise fall into disrepair.

Once a qanat dries up or is reduced to a useless trickle, (whether for physical reasons - the water table falls - or for socio-economic reasons which reduce or halt qanat maintenance), the qanat is abandoned. However, qanats that have not yet collapsed have sometimes been repaired and reused decades, or even centuries, after abandonment. For example, many of Syria's qanats were abandoned as the frontier of settlement and agriculture in the region retreated westward after the l0th century, yet the qanats of the Selemiya Plain - where roughly one-half of the qanat galleries of Syria are found - were still being praised by Arab geographers as late as the 14th century for the purity of their water (Furon, 1967, p. 62). Tamerlane ravaged all of Syria in 1400, yet the qanats of Selemiya were again being protected and maintained by the late 15th century (Furon, 1967, p. 62). In 1516 the country fell to the Turks and for the next four centuries Syria slowly decayed (Lewis, 1949, p. 285). The qanats of the Selemiya region were abandoned and were not cleaned and used again until the late 1800s when pioneering Ismailis, settling on the Selemiya Plain, and immigrant Circassians settling north of Selemiya, cleaned and repaired as many as 125 old qanat galleries to provide water for irrigating 1240 ha (Lewis, 1949, p. 284, p. 286). By the 1950s diesel-pumped wells were growing in popularity in the Selemiya area, especially as a means of expanding water supplies for irrigating cotton, and the qanats of the region began drying up as the water table fell. Today, about 5000 mechanized wells pump water to irrigate 36,000 ha around Selemiya. As a result, the water table has fallen from 1-3 m depth (1950) to 10-30 + meters (today), and all 125 qanats of the Selemiya Plain have either dried up or been reduced to a useless trickle. Only five qanats in the region still flow, albeit with diminished and inintermittentlow all of these are found around Sa'an, where a small dam and reservoir 2 km north-west of the town helps to recharge the aquifer in the immediate vicinity of these five qanats.

Qanats at Taibe oasis (eastern Syria) also were probably abandoned along with the village after Tamerlane's rampage through Syria in 1400. These qanats were refurbished in the 18th-19th centuries during the Turkish (Ottoman) occupation (1 the region, but were abandoned again as the Turks departed in 1917. They were once again refurbished when Bedouin families settled in Taibe in 1940 but were abandoned in 1952 when new diesel-pumped wells drew down the aquifer which fed Taibe's qanats. One qanat (of four) was later opened that same year by digging deeper collecting wells (Kobori, 1980, pp. 12-14 Kobori et at., 1980, p. 53). The last operational Taibe qanat was once again abandoned in 1987, after a flood choked it with sediment it has been replaced with new diesel-pumped wells (Kobori, 1990, p. 323). This cycle of qanat use and abandonment has occurred at other qanat sites particularly at those sites in central and eastern Syria that have remained on the frontier of settlement and agriculture.

Because qanats have been the key to life in many settlements, numerous laws have been developed to regulate their construction and use. The expansion of old qanats or the construction of new ones must be done in such a way that the flow of water in existing qanats will not be diminished. The initial installation or placement of modern water-pumping devices is usually controlled by these same traditional water laws, often based on shari'a, or Islamic law. For example, harim - the area around each well which is protected so that new wells will not affect the yield of existing ones - is prescribed for tube wells just as it is for qanat mother wells. But the protected harim area for qanat wells is much greater - usually about six to eight times greater in radius - than that for tube wells, legally permitting a much denser concentration of mechanically-pumped wells within any given region (Caponera, 1954, p. 31 Nutahara, 1982, p. 62). There are even reports of pumped wells belonging to one village being installed - illegally, though with impunity - within the harim of active qanat mother wells belonging to a neighboring village. For example, farmers from Al Mouzamiya installed about 15 pumps in 1979-1980 near and within the harim of the mother wells belonging to Ruhaybah village, and though Ruhaybah elders complained to the government about this infringement on their water rights, the pumps continued to operate and both of Ruhaybah's qanats ceased flowing by 1981.

Once pumped wells are installed, their use is never monitored, so that the cumulative and sustained impact of hundreds and thousands of electric and diesel-pumped wells all drawing from the same aquifer is not assessed. Traditional water laws and the village-level regulation of water shares by the mirab (an official in charge of water distribution for irrigation) need to be expanded to a regional scale, perhaps by creating a state mirab to coordinate pumping rates and otherwise regulate the use of ground-water resources throughout Syria. This imperative may be mitigated in the near future - albeit temporarily - by the conservation of surface water supplies, which are plentiful enough in Syria - at present rates of use - to compensate for a loss of ground-water resource officials estimate that surface water resources could be stretched much farther as about one-half of the country's surface water resources are presently wasted through evaporation, leaky municipal water systems, and other inefficiencies.

Qanats are being abandoned in Syria as water tables fall and qanat galleries go dry. This is not an isolated phenomenon this same scenario is being played out in Pakistan, Iran, Oman, Morocco and many other places where qanats are still used, or have recently been in use. The effect on individual qanat-dependent communities has been a loss of local control over traditional water resources and (often) out-migration from farm communities to cities to find non-farm employment. In some cases, employment opportunities offered by urban-based industries or regional oil development provides an incentive for working age males to leave their villages. If these laborers do return, they will often work only for higher wages. These factors reduce the labor pool for qanat maintenance, leaving them prone to neglect (Sutton, 1984, p.11).

Qanats now play only a marginal, diminishing role in Syrian agriculture. These features are useful in only a few limited areas, with highly localized use at each of those locales. Yet, as long as shallow, perennial aquifers are not depleted by overpumping, qanats can still be used to exploit these waters in a sustainable fashion. They could even be improved by farmers committed to sustainable irrigation by lining the susubterraneanhannel to prevent collapse and to reduce erosion and silting in the tunnel. Adding a shut-off valve would restrict the flow of water to periods when it is needed. Building a large holding tank or reservoir at the terminus would help to store the water which flows overnight and between irrigation periods. Policies designed to preserve and improve qanats are futile, however, if falling water tables are not stabilized.

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The Qanat: An Ancient Technology Still Delivering Water Today

I was doing some light reading on hydrogeology the other day and came upon something that interested me, and hopefully will be of some interest and/or use to you. I’m always fascinated by history and the way ancient civilizations came up with ingenious ways to survive in harsh conditions, and what I found in my book was exactly that.

The technology I’m talking about is called a qanat. Well, that’s what it was called in what is present-day Iran, which is where the first one was constructed. Since then it has spread to a number of other countries throughout the world where it is known by a number of names kanat, khanat, kunut, kona, konait, ghanat, and ghundat.

A qanat is a fairly simple way to bring groundwater from one place to another. Well, simple on paper construction took a lot of knowledge, time, and manpower. Let me start with a picture so you can see what I’m talking about and then I’ll describe it in more detail.

Qanats are used to move water from underground aquifers deep inside a hillside to lower elevations. The system is simple and basically consists of a gently sloping horizontal shaft (called qanat channel in picture) and vertical access shafts. Not surprisingly, the first step in constructing a qanat is finding the water. The location for a qanat is usually a hillside or somewhere where sediment has been (at some point in time) washed out and has formed an alluvial fan.

The process starts with a surveyor, or someone who is knowledgeable about the geology of the area, going out and finding a site that they believe has water. From there 2-4 people start digging the first vertical shaft up on the hillside to see if they’re on the water. As they get dipper a windlass is set up to collect the spoils and haul them to the top. The shaft can be anywhere from 50 feet deep to hundreds of feet deep depending on the depth of the groundwater. One simple, but ingenious step in the process is to dump the spoils around the opening of the vertical shaft. This creates a buffer around the opening and keeps rain water that is running down the hill from pouring into the shaft and adding sediment or contaminants to the groundwater. If this first shaft does not hit water then additional shafts will need to be dug in different locations until the water is found.

Once water is found the next step is deciding on a path for the qanat to follow in order to carry water down to a place where it will be useful (a town, village, field, etc.). Then, more vertical shafts are added along the path. These additional vertical shafts serve as a way to ventilate the qanat as well as to guide the people digging the qanat along the decided on path. Also, the spoils accumulated along the way are hauled up through these vertical shafts. Once all the vertical shafts are complete the diggers can begin digging the qanat. Once the qanat is complete the water should start flowing, and can continue to do so for years to come.

Well, there’s actually a decent amount of other work that needs to be done before that. Someone needs to figure out the slope of the qanat. This seems like a simple task, but the slope is very important and must be given a lot of thought. If you dig the slope too steep the water will move too quickly through the qanat and wash away or damage the tunnel. If you dig the slope too gentle then the water will not flow down the tunnel.

Once the slope is worked out then the depth of all of the vertical shafts need to be calculated to match the slope. If the shafts don’t go deep enough then they will never intersect the qanat and will serve no purpose, and if they go too deep they will disrupt the flow of water.

All of this work is not easy. Actually it is very hard, back-breaking, work. On average a typical qanat is 6-10 miles long. One very old qanat is Iran is 30 km long! To give you an idea of how much work goes in, they say that it takes one year to dig one km. Wow!

This work is not only hard, it’s dangerous. Cave-ins are one of the dangers faced. If a tunnel is being dug in hard rock or compacted clay it is fairly safe, and should not cave in. However, if the qanat is being dug through less desirable ground then reinforcing of some kind will be needed. Suffocation is another danger faced. Lack of oxygen or the presence of gas can kill the workers. To stay safe the workers watch their oil lamps for signs of depleting oxygen. Lastly, and maybe most dangerous, is the point when the workers reach the first shaft. It could be years before the initial shaft is reached, and over that time it could have partially filled with water. As the diggers break through into the shaft a wall of water can come through and drowned them, or wash them away (hitting them on rocks and injuring them). To avoid this the first vertical shaft should be drained of water before it is penetrated if there is a means of doing this. Otherwise, the diggers need to use caution to tap the shaft very gently and let the water drain into the qanat before continuing.

Finally, it must be decided what will happen at the mouth of the qanat. In most cases there is one, or several, canals that branch off from the mouth and distribute the water to different places.

For a technology to still be in use thousands of years after it was introduced to the world it must be beneficial to the population it’s serving. In the case of the qanat there are several benefits. Considering qanats are generally used in arid/semi-arid environments where it can get very hot, one of the benefits of keeping the water underground as long as you can is that it is not lost to evaporation. This may seem like a small thing, but over the years keeping the water underground can save millions of gallons. A second benefit is that no electricity is needed for pumps since the system uses gravity to keep the water flowing. Thirdly, a qanat is sustainable because its source is groundwater. The qanat will never significantly deplete an aquifer because it only takes as much as the aquifer can give. If the level of the aquifer drops too much then the water will stop flowing into the qanat, and the aquifer can recharge itself. Further, once the water gets into a town or village the water can be used as a power source to turn mills. And finally, needless to say, a qanat brings much needed water to an area so that it can flourish, grow crops, and establish itself.

While qanats were first developed centuries ago, they are still very much in use today. For instance, in Iran there are still 37,000 qanats in use that are providing water to millions of people (and that is just in Iran). It astounds me that an idea someone had thousands of years ago is still providing an essential need to so many people around the world. It’s nice to know that in our day and age, where you can’t turn a corner without hearing about some new technology, there are still some traditional, simple, technologies being put to use. Below you’ll find a great video where you can get a closer look at the inside of a qanat and how they were/are built. Finally, this is just a brief overview there are a lot more details of the qanat system that I did not include in this article. If you’d like to read some more please take a look at the sources listed below.

As always, thank you for reading, and please leave a comment and let me know what you thought.


Power from Water and Wind

The Muslim geographers and travelers leave us in no doubt as to the importance of corn-milling in the Muslim world. This importance is reflected by the widespread occurrence of mills from Iran to the Iberian Peninsula. Arab geographers were rating streams at so much 'mill-power'. Large urban communities were provided with flour by factory milling installations.

The ship-mill was one of the methods used to increase the output of mills, taking advantage of the faster current in midstream and avoiding the problems caused by the lowering of the water level in the dry season. Another method was to fix the water-wheels to the piers of bridges in order to utilize the increased flow caused by the partial damming of the river. Dams were also constructed to provide additional power for mills (and water-raising machines) In the twelfth century al-Idrisi described the dam at Cordoba in Spain, in which there were three mill houses each containing four mills. Until quite recently its three mill houses still functioned.


Existing Mill Houses on a Dam Near Cordoba Were Described by al-Idrisi

Evidence of the Muslims' eagerness to harness every available source of water power is provided by their use of tidal mills in the tenth century in the Basra area where there were mills that were operated by the ebb-tide. Tidal mills did not appear in Europe until about a century after this.
Water power was also used in Islam for other industrial purposes. In the year 751 the industry of paper-making was established in the city of Samarqand. The paper was made from linen, flax or hemp rags. Soon afterwards paper mills on the pattern of those in Samarqand were erected in Baghdad and spread until they reached Muslim Spain. The raw materials in these mills were prepared by pounding them with water-powered trip-hammers. Writing about the year 1044, al-Biruni tells us that gold ores were pulverized by this method "as is the case in Samarqand with the pounding of flax for paper". Water power was also used in the Muslim world for fulling cloth, sawing timber and processing sugarcane. It is yet to be established to what extent industrial milling in Europe was influenced by Muslim practices. A likely area of transfer is the Iberian Peninsula, where the Christians took over, in working order, many Muslim installations, including the paper mills at Jativa.


The Persian Qanat

“A traveler flying over Iran can see plainly that the country has an arid climate. The Iranian plateau is largely deserted. Most of Iran (excepting areas in the northwestern provinces and along the southern shores of the Caspian Sea) receives only 6 to 10 inches of rainfall a year. Other regions of the world with so little rainfall (for example the dry heart of Australia) are barren of attempts at agriculture.

Yet Iran is a farming country that not only grows its own food but also manages to produce crops for export, such as cotton, dried fruits, oil seeds and so on. It has achieved this remarkable accomplishment by developing ingenious system for tapping underground water. The system, called qanat (from a Semitic word meaning “to dig”) was invented in Iran thousands of years ago, and it is so simple and effective that it was adopted in many other arid regions of the Middle East and around the Mediterranean” (Wulff-Dieter Heintz).

The origin of the word qanat is still controversial. Some believe that it has a Persian origin and changed into the present pronunciation. According to this theory the word qanat derives from the Persian word Kene, which means digging. However, some believe that this word is originally Arabic, from which the English word canal has derived. Throughout the world there are over 27 names for this traditional technique. For example, the names used in southwest Asia are: Quanat, Can ant, Connought, Kanat, Khanate, Khad, Kanayet, Ghannat, Karez, Kariz, Kahriz, Kahrez, Karaz, Kakoriz, and Falaj.

In addition, one may come across the following names for qanat in northern Africa: Foggara, Faghare, Mayon, Iffeli, Negoula, Khettara, Khottara, Rhettara, and Foggaras.

All these names refer to a horizontal tunnel, which drains groundwater, usually in alluvial fans. The mechanism of this structure is the same around the globe a horizontal tunnel with a gentle slope that partly cuts through the aquifer. Water in saturated layers seeps into the tunnel, accumulates and flows down the tunnel.

It is very typical for deserts to have a landscape of many craters in a row. The craters, which can be easily seen from air, are actually the mouths of a Qanat’s shaft wells running across a desert. These wells are vital for Qanats as they act as means of ventilation as well as a way through which debris and excavated materials can be hauled onto the surface International Centre on Qanats and Historical Hydraulic Structures in Iran there are Qanats with lengths over 10 km, sometimes cutting through a very hard formation.

It is amazing how a qanat 70 km long can be constructed by a human being. This is why in some rural areas locals attribute the creation and construction of qanats to supernatural powers or creatures such as genies. But the fact is that these long qanats were invented by normal people hu s of years ago, and extended by by their offspring during periods of
drought as far as the aquifer would allow in order to keep the qanat discharge steady. Thus, a qanat became longer and longer through years where the pick axe was handed down from father to son.

This process resulted not only in the physical development of qanats, but also in the accumulation of knowledge and the buildup of a distinct civilization- qanat civilization, which is rooted in the technical characteristics of the qanat. In general, qanats are examples of how deeply culture, environment and technology are interwoven. They cut through history, and bring not only water to quench the thirst of lands, but also this priceless message: Earth is our kind mother as long as we are grateful sons.

Definition

Qanat is a gently sloping subterranean canal, which taps a water-bearing zone at a higher elevation than cultivated lands. In 2014 there have existed some 37000 active qanats running all over Iran, discharging about 7 billion m3 groundwater a year. A qanat consist of a series of vertical shafts in sloping ground, interconnected at the bottom by a tunnel with a gradient flatter than that of the ground.

The first shaft (mother well) is sunk, usually into an alluvial fan, to a level below the groundwater table. Shafts are sunk at intervals of 20 to 200 m in a line between the groundwater recharge zone and the irrigated land. From the air, a qanat system looks like a line of anthills leading from the foothills across the desert to the greenery of an irrigated settlement.

Qanat engages a variety of knowledge and its studying entails an interdisciplinary approach. In a traditional realm, qanats are embraced by a socio-economic system that guarantees their sustainability. The facets of this socio-economic system operate closely together and make it possible for the qanats to remain into future.

Technical Overview

A qanat is constructed by tunneling into a cliff, scarp or base of a mountainous area, following a water-bearing formation (Karaji, 1987).

On the Iranian plateau, an important heartland of qanat- watered settlement, this change in water technology is draining aquifers, altering the distribution of towns and villages, and transforming the life worlds of Iranian villagers. Qanat is a sustainable technique to tap groundwater without inflicting any damage on the aquifer.

Qanat system carries some advantages as follows: Qanat system works only with the force of gravity and does not consume any kind of fuel unlike pumped wells. Qanat system just drains out the overflow of groundwater and does not throw the aquifer inflow-outflow off balance.

For qanat does not use up the groundwater and empty the porous layers of water, no soil compression would come about and accordingly no subsidence on the surface. Given that qanat does not suck up the groundwater, the water extraction by means of qanat does not make the saline water creep into the fresh water reserves. The qanat system does not manipulate the structure of soil, so it does not diminish the soil capacity to hold groundwater.

Digging a qanat depends on the climatic, hydrogeological and topographical condition of the region. Qanats are dug at areas with temporary surface water resources, a land slope of up to 0.5 in 1000 and permanent underground waters. The length of a qanat which also affects its water outputs different in various natural conditions. These circumstances depend on the land gradient and the depth of the mother well. On the other hand, a lower level of underground water means a deeper mother well. The most important factor specifying qanat length is land gradient. Here the former factor has an inverse proportion to the latter.

Wulff, H. E. (1966). The traditional crafts of Persia: Their development, technology and influence on Eastern and Western civilizations.

Nadji, M., & Voigt, R. (1972). “Exploration for Hidden Water” by Mohammad Karaji—The Oldest Textbook on Hydrology?. Groundwater, 10(5), 43-46.


Qanat

Qanat, karez, falaj eller andre namn er ein type vatningssystem brukt til å skapa pålitelege vassforsyning i varme, tørre og halvtørre klimaer.

Ordet qanat (arabisk قناة) blir brukt i Iran, Syria og Jordan. [1] Vassforsyningssystemet er også kjend som falaj (Dei sameinte arabiske emirata og Oman), kariz eller kareze (persisk skrift كاريز) i Iran, Afghanistan, Pakistan og Sentral-Asia, kahan (persisk کهن), khettara (Marokko), galeria (Spania), kahn (Balutsjistan) og foggara eller fughara ( Nord-Afrika). [1] Alternative namn i Asia og Nord-Afrika er kakuriz, chin-avulz og mayun. Andre stavemåtar for qanat med latinske bokstavar er mellom anna kanat, khanat, kunut, kona, konait, ghanat og ghundat.

Systemet er nært i slekt med vatningssystemet i Turfan i Kina. Teknologien utvikla seg truleg i Iran i oldtida, [2] [3] [4] og deretter spreidd seg til andre kulturar via mellom anna Silkevegen, men to nyleg oppdaga falaj-system i al Ain i Dei sameinte arabiske emirata og Umm Safah i Sharjah er datert til høvesvis 1000 f.Kr. [5] [6] og jernalderen. [7] [8] Den eldste skriftlege omtalen stammar frå perioden 722 til 705 f.Kr. i ei skildring av felttoget til Sargon II av Assyria.

Verdien av ein qanat er direkte knytt til kvaliteten, volumet og regulariteten til vasstraumen. Historisk sett har ein stor del av folkesetnaden i Iran og andre tørre land i Asia, Midtausten og Nord-Afrika vore avhengige av vatn frå qanatar busetjingsområda svarte tett til områda der ein kunne byggja slike vatningskanaler. Sjølv om det var dyrt å byggja ein qanat hadde han ein langsiktige verdi for samfunnet, og var derfor av stor tyding for gruppa som investerte i å byggja og vedlikehalda han. [9]

Qanatsystemet er bygd som ein serie av brunnliknande sjakter som er knytte til kvarandre ved hjelp av såvidt slake tunnelar. Dei blir tappa ut i underjordisk vatn på ein måte som effektivt leverer store mengder vatn til overflaten, uten at ein treng pumpa. Vatnet drenerer ved hjelp av tyngdekrafta mot eit område som ligg lågare enn kjelda, som vanlegvis er ein høgareliggjande akvifer. Qanatar gjer det mogleg å transportere vatn over lange avstandar i varme, tørre klimaer uten å tapa ein stor del av vatnet gjennom vassig og fordamping.


Qanats, Surangams

Qanats and surangams are examples of water accessing systems which have similar technologies. Qanat technology originated in Iran and was used extensively in the dry, arid desert regions of the Middle East and surangam technologyis used in the hilly terrains of the Western Ghats. Both systems essentially consist of underground tunnels that source the aquifer and use gravity to convey the water to groundlevel.

In both systems, construction is undertaken by hand by labourers or farmers. The most important aspect of building these structures is identifying the source of water. The traditional Qanat builders, called muqannis, follow the water courses coming down the mountains and identify subsurface water sources. They dig a trial well to test the quantum and flow of water before beginning work on the Qanat. Similarly, in India, workmen who traditionally undertook the digging of surangas, were people who were familiar with the slopes, soil structure, catchment areas and used their knowledge of local flora and fauna to identify water sources.

Parameter Qanats Surangams
Physical conditions Arid, desert region with high surface evaporation rates. Absence of rivers Coastal hill areas underlain by lateritic and weathered rocks with high rainfall. Rapid discharge of river water due to steep slopes
Water source Groundwater Groundwater
Type of structure A series of wells connected by a tunnel Tapping groundwater directly
Length of tunnel 30 &ndash 150 m sometimes as long as 6000 m to 8000m 3 - 300 m
Height 1m - 1.5 m 0.9 -15 m
Width 0.5 &ndash 1m 0.5 &ndash 0.8 m
Vertical shafts At intervals of 20 &ndash 35m Generally no shafts unless tunnels are very long
Style of construction Began from where water was to be delivered and worked its way up the slope to mother well Began from the source of water


Qanats: Originating in Armenia 2,500 years ago, Qanats have reemerged into the international spotlight as &ldquorational irrigation systems,&rdquo says Dr. Ali A. Semsar Yazdi the Director of the newly formed International Centre on Qanat and Historic Hydraulic Structures (ICQHS) in Yazd, Iran.
Today in Iran, more than 34,355 of the structures are still functioning. Sophisticated, self-regulating, and structurally sound, Qanat systems were an integral part of Iranian cotton production in the ninth and tenth centuries AD, and have since been found in 35 countries including China, India, Egypt, and even as far westward as Spain and Peru.

Qanats (also called kariz, lyoun, aflaj) use underground water channels to drive the natural flow of aquifers to the earth&rsquos surface for irrigation and domestic use. An intricate series of vertical shafts run from a point source near a hill or mountaintop and continue downhill to a field or village extending between one kilometer (km) and 70 km in length.The Qanat system was used widely across Persia and the Middle East for many reasons. First, the system requires no energy, reliant on the force of gravity alone. Second, the system can carry water across long distances through subterranean chambers avoiding leakage, evaporation, or pollution. And lastly, the discharge is fixed by nature, producing only the amount of water that is distributed naturally from a spring or mountain, ensuring the water table is not depleted. More importantly, it allows access to a reliable and plentiful source of water to those living in otherwise marginal landscapes.

Anthony Smith, a well known author covering the social importance of Qanats in Iran, explains the system as &ldquothe life of the village, without it, the village would be dust. The systems can deliver water at a rate between one liter per second and 500 liters per second, and a single Qanat can irrigate hundreds of hectares.The well is horizontal, instead of vertical, relying on gravity and pressure from upland shafts to channel water up to the surface.

Over the centuries, the abundance of Qanats has varied amidst shifting dynasties and new landowners. More recently, the resurgence of Qanats is fighting years of inevitable modernization in which wells and piped water systems were constructed for growing populations under new land arrangements. Variable and decreasing rainfall have also hindered development efforts. In Syria, 92% of all Qanats have run dry since the introduction of pumped tube-wells in the mid-1970s. In both Syria and Iran, Qanats were constructed in areas that received 100-300 millimeters (mm) of precipitation each year. According to Professor Dale Lightfoot at the University of Colorado, these areas have received more variable rainfall in recent decades, compromising the efficacy of Qanats. Time and money is also a serious obstacle to new construction. New systems take anywhere between 25 and 75 years to construct with traditional materials and strategies.Thus, ICQHS focuses its resources in village-level education, training users how to revitalize and repair existing Qanats. Since 2008, ICQHS has taken on six projects to restore Qanat systems in villages surrounding the Center in Yazd, successfully increasing drinking water and irrigation supplies.

Surangams

Similar to the technology of quanats is the surangam technology that was in vogue in Dakshin Kannada district of Karnataka and Kasaragod district of Kerala. A Surangam is basically a tunnel dug through a laterite hillock through which water seeps out and into the tunnel. Water is then collected at the end of the tunnel in a storage pit. A surangam is also known as thurangam, thorapu, mala in different parts of Kasaragod. The only cost of the a surangam is the initial cost of digging which was done by local workmen who were familiar with the geology, soil, slope etc.

Generally a surangam was about 0.45&ndash0.70 m wide and about 1.8-2.0 m in height. The length of the tunnel varied between 3 m to 300 m. For long tunnels, air shafts were provided to ensure atmospheric pressure. Surangams are dug in places where the hydrogeological profile consists of is lateritic and weathered rocks. Surangams are used to provide water for drinking, domestic use and sometimes even for irrigation. According to Harish Halemane of Kasaragod, there are about 2000 surangams in Bayar village in Kasaragod. In Sheni village in Kasaragod, there is a 90-year old, 250 m long surangam with seven air events.

In Manila village in Dakshin Kannada district, Achyut Bhat&rsquos family dug nearly 20 surangams, of which 14 are still functional. The family&rsquos 15 acre property lies in a rocky area, where it digging a well is not economical. Today, the plot has areca nut and cocoanut gardens. Achyut Bhat is passionately committed to the idea of surangams and has propagated the idea in his village. He says that there are about 300 surangams in the village.


Watch the video: Iran Kariz ancient underground water plants كاريزها و فناوري باستاني آب در ايران (May 2022).