Registered Charity Number: 1037414

Qanat

January 17th, 2016 in News by admin

Qanat is the generic term for an ancient environmentally sustainable water harvesting and conveyance technique believed to have originated in Persia in the early first millennium B.C. Qanat is the Arabic word for “channel”. Qanats are also called kārīz (or kārēz from Persianكاريز‎‎) kahriz/kəhriz (Azerbaijan); khettara (Morocco); galleria (Spain); falaj (from Arabicفلج‎) (United Arab Emirates and Oman); Kahn (Baloch) or foggara/fughara (North Africa). Alternative terms for qanats in Asia and North Africa are kakurizchin-avulz, and mayun. Common variants of qanat in English include kanat, khanatkunutkonakonaitghanatghundat and in Britain canal.

The qanat system consists of a network of underground canals that transport water from aquifers in highland regions to the surface at lower levels by gravity. This ingenious technology ― known as falaj In Omankhettara or foggara in North Africa, karez or kanerjing in the north-western desert of China, and karez in Afghanistan, Pakistan and Central Asia ― continues to provide reliable supply of water for human settlements and irrigation in hot, arid and semi-arid climates. In fact, qanat technology exists in more than 34 countries. In Iran alone, there are an estimated 50,000 qanats, nearly three-quarters of which are still working. In Oman, there are more than 3,000 active qanats (aflaj).

Qanats are a valuable part of the cultural heritage of the countries in which they are found. They are also a time-honoured practical tool ― underpinned by mutual dependence and communal values for sustainable water management. Yet, manyqanats have fallen into disrepair or have dried up. Many of those which remain active are threatened by silt sedimentation in canals, the urban migration of youth, and the decline of experts for managing such systems. In addition, some governments have begun to abandon traditional, sustainable water transport systems in favour of modern, less sustainable but more productive hydraulic systems, however, there is evidence of renewed interest in this ancient system of underground channels. There is a growing body of literature on the subject. In addition, the United Nations Educational, Scientific and Cultural Organization (UNESCO), the United Nations University (UNU), The International Centre on Qanats and Historic Hydraulic Systems (ISQHS) in Iran, and the IPOGEA Traditional Knowledge Centre are just a few of the increasing number of organizations that are encouraging the further study, conservation and rehabilitation of qanats and, more broadly, that are facilitating the search for ways to incorporate modern advancements with traditional knowledge about water resources management.

While qanat systems cannot replace modern advances in water resources management, they still have a role to play as a sustainable groundwater management tool.

qanat interior

A Qanat Interior

A qanat (Persian: قنات‎‎/کاریز) is a gently sloping underground channel with a series of vertical access shafts, used to transport water from an aquifer under a hill. Qanats create a reliable supply of water for human settlements and irrigation in hot, arid, and semi-arid climates.

The qanat technology is known to have been developed by the Persian people sometime in the early 1st millennium BC, and spread from there slowly westward and eastward.

Screen Shot 2016-01-17 at 20.02.43

A qanat tunnel near Isfahan

Screen Shot 2016-01-17 at 20.03.30

Cross-section of a Qanat

Qanats are constructed as a series of well-like vertical shafts, connected by gently sloping tunnels. Qanats tap into subterranean water in a manner that efficiently delivers large quantities of water to the surface without need for pumping. The water drains by gravity, with the destination lower than the source, which is typically an upland aquifer. Qanats allow water to be transported over long distances in hot dry climates without loss of much of the water to evaporation.

The qanat should not be confused with the spring-flow tunnel, typical to the mountainous area around Jerusalem. Although there are similarities in the construction techniques (both are excavated tunnels designed to extract water by gravity flow), there are crucial differences between the two. Firstly, the origin of the qanat was a well that was turned into an artificial spring. In contrast, the origin of the spring-flow tunnel was the development of a ‘real’ spring to renew or increase flow, following an episode of the water table receding. Secondly shafts, which are essential to qanats, are not essential to spring-flow tunnels.

It is very common in the construction of a qanat for the water source to be found below ground at the foot of a range of foothills of mountains, where the water table is closest to the surface. From this point, the slope of the qanat is maintained closer to level than the surface above, until the water finally flows out of the qanat above ground, i.e., the qanat is an underground tunnel, beginning from an underground water source, with a gentle slope made in such a way that water is pulled by gravity to the surface (which is at a lower level than that of the underground water source). To reach an aquifer, qanats must often extend for long distances.

Qanats are sometimes split into an underground distribution network of smaller canals called kariz. Like qanats, these smaller canals are below ground to avoid contamination. In some cases water from a qanat is stored in a reservoir, typically with night flow stored for daytime use. An ab anbar is an example of a traditional qanat-fed reservoir for drinking water in Persian antiquity.

The qanat system has the advantage of being resistant to natural disasters such as earthquakes and floods, and to deliberate destruction in war. Furthermore, it is almost insensitive to the levels of precipitation, delivering a flow with only gradual variations from wet to dry years. From a sustainability perspective, Qanats use the force of gravity to bring groundwater to the surface with no energy requirement and, thus, have low life cycle operation and maintenance costs once built. Qanats transfer freshwater from the mountain plateau to the lower lying plains that have a saltier soil. This helps to control the salinity of soil and prevent desertification.

Features common to regions that use qanat technology

The qanat technology is used most extensively in areas with the following characteristics:

  • An absence of larger rivers with year-round flows sufficient to support irrigation
  • Proximity of potentially fertile areas to precipitation-rich mountains or mountain ranges
  • Arid climate with high surface evaporation rates so that surface reservoirs and canals would result in high losses
  • An aquifer at the potentially fertile area which is too deep for convenient use of simple wells

Impact of qanats on settlement patterns

A typical town or city in Iran, and elsewhere where the qanat is used has more than one qanat. Fields and gardens are located both over the qanats a short distance before they emerge from the ground and below the surface outlet. Water from the qanats defines both the social regions in the city and the layout of the city.

The water is freshest, cleanest, and coolest in the upper reaches and more prosperous people live at the outlet or immediately upstream of the outlet. When the qanat is still below ground, the water is drawn to the surface via water wells or animal driven Persian wells. Private subterranean reservoirs could supply houses and buildings for domestic use and garden irrigation. Further, air flow from the qanat is used to cool an underground summer room (shabestan) found in many older houses and buildings.

Downstream of the outlet, the water runs through surface canals called jubs (jūbs) which run downhill, with lateral branches to carry water to the neighbourhood, gardens and fields. The streets normally parallel the jubs and their lateral branches. As a result, the cities and towns are oriented consistent with the gradient of the land; this is a practical response to efficient water distribution over varying terrain.

The lower reaches of the canals are less desirable for both residences and agriculture. The water grows progressively more polluted as it passes downstream. In dry years the lower reaches are the most likely to see substantial reductions in flow.

Construction

Traditionally qanats are built by a group of skilled labourers, muqannīs, with hand labour. The profession historically paid well and was typically handed down from father to son.

Screen Shot 2016-01-17 at 20.05.08

Alluvial Fan in Southern Iran. Image from NASA’s Terra satellite

The critical, initial step in qanat construction is identification of an appropriate water source. The search begins at the point where the alluvial fan meets the mountains or foothills; water is more abundant in the mountains because of orographic lifting and excavation in the alluvial fan is relatively easy. The muqannīs follow the track of the main water courses coming from the mountains or foothills to identify evidence of subsurface water such as deep-rooted vegetation or seasonal seeps. A trial well is then dug to determine the location of the water table and determine whether a sufficient flow is available to justify construction. If these prerequisites are met, the route is laid out aboveground.

Equipment must be assembled. The equipment is straightforward: containers (usually leather bags), ropes, capstans to raise the container to the surface at the shaft head, mattocks and shovels for excavation, lights, spirit levels or plumb lines and string. Depending upon the soil type, qanat liners (usually fired clay hoops) may also be required.

Although the construction methods are simple, the creation of a qanat requires a detailed understanding of subterranean geology and a degree of engineering sophistication. The gradient of the qanat must be carefully controlled: too shallow a gradient yields no flow and too steep a gradient will result in excessive erosion, collapsing the qanat. And misreading the soil conditions leads to collapses, which at best require extensive rework and at worst are fatal for the for those constructing the tunnel.

Construction of a qanat is usually performed by a crew of 3-4 muqannīs. 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.

The crew typically begins from the destination to which the water will be delivered into the soil and works toward the source (the test well). Vertical shafts are excavated along the route, separated at a distance of 20–35 m. The separation of the shafts is a balance between the amount of work required to excavate them and the amount of effort required to excavate the space between them, as well as the ultimate maintenance effort. In general, the shallower the qanat, the closer the vertical shafts. If the qanat is long, excavation may begin from both ends at once. Tributary channels are sometimes also constructed to supplement the water flow.

Most qanats in Iran run less than 5 km, while some have been measured at ~70 km in length near Kerman. The vertical shafts usually range from 20 to 200 meters in depth, although qanats in the province of Khorasan have been recorded with vertical shafts of up to 275 m. The vertical shafts support construction and maintenance of the underground channel as well as air interchange. Deep shafts require intermediate platforms to simplify the process of removing spoil.

The construction speed depends on the depth and nature of the ground. If the earth is soft and easy to work, at 20 meters depth a crew of four workers can excavate a horizontal length of 40 meters per day. When the vertical shaft reaches 40 meters, they can excavate only 20 meters horizontally per day and at 60 meters in depth this drops below 5 horizontal meters per day. In Algeria, a common speed is just 2 m per day at 15 m depth. Deep, long qanats (which many are) require years and even decades to construct.

The excavated material is usually transported by means of leather bags up the vertical shafts. It is mounded around the vertical shaft exit, providing a barrier that prevents windblown or rain driven debris from entering the shafts. These mounds may be covered to provide further protection to the qanat. From the air, these shafts look like a string of bomb craters.

The qanat’s water-carrying channel must have a sufficient downward slope that water flows easily. However the downward gradient must not be so great as to create conditions under which the water transitions between supercritical and subcritical flow; if this occurs, the waves that result can result in severe erosion that can damage or destroy the qanat. In shorter qanats the downward gradient varies between 1:1000 and 1:1500, while in longer qanats it may be almost horizontal. Such precision is routinely obtained with a spirit level and string.

In cases where the gradient is steeper, underground waterfalls may be constructed with appropriate design features (usually linings) to absorb the energy with minimal erosion. In some cases the water power has been harnessed to drive underground mills. If it is not possible to bring the outlet of the qanat out near the settlement, it is necessary to run a jub or canal over ground. This is avoided when possible to limit pollution, warming and water loss due to evaporation.

The vertical shafts may be covered to minimize blown-in sand. The channels of qanats must be periodically inspected for erosion or cave-ins, cleaned of sand and mud and otherwise repaired. For safety, air flow must be assured before entry.

Some damaged qanats have been restored. To be sustainable, restoration needs to take into account many nontechnical factors beginning with the process of selecting the qanat to be restored. In Syria, three sites were chosen based on a national inventory conducted in 2001. One of them, the Drasiah qanat of Dmeir, was completed in 2002. Selection criteria included the availability of a steady groundwater flow, social cohesion and willingness of the community to contribute for using the qanat, and the existence of a functioning water-rights system.

Qanat Uses

The primary applications of qanats are for irrigation and drinking water supply. Other applications include cooling and ice storage.

Screen Shot 2016-01-17 at 20.06.26

Qanats used in conjunction with a wind tower can provide cooling as well as a water supply. A wind tower is a chimney-like structure positioned above the house; of its four openings, the one opposite the wind direction is opened to move air out of the house. Incoming air is pulled from a qanat below the house. The air flow across the vertical shaft opening creates a lower pressure (Bernoulli Effect) and draws cool air up from the qanat tunnel, mixing with it. The air from the qanat is drawn into the tunnel at some distance away and is cooled both by contact with the cool tunnel walls/water and by the transfer of latent heat of evaporation as water evaporates into the air stream. In dry desert climates this can result in a greater than 15 °C reduction in the air temperature coming from the qanat; the mixed air still feels dry, so the basement is cool and only comfortably moist (not damp). Wind tower and qanat cooling have been used in desert climates for over 1000 years.

Screen Shot 2016-01-17 at 20.07.02

By 400 BC, Persian engineers had mastered the technique of storing ice in the middle of summer in the desert.

The ice could be brought in during the winters from nearby mountains. But in a more usual and sophisticated method they built a wall in the east–west direction near the yakhchal (ice pit). In winter, the qanat water would be channelled to the north side of the wall, whose shade made the water freeze more quickly, increasing the ice formed per winter day. Then the ice was stored in yakhchals — specially designed, naturally cooled refrigerators. A large underground space with thick insulated walls was connected to a qanat, and a system of wind catchers or wind towers was used to draw cool subterranean air up from the qanat to maintain temperatures inside the space at low levels, even during hot summer days. As a result, the ice melted slowly and was available year-round.

Afghanistan

The Qanats are called Kariz in Dari (Persian) and Pashto and have been in use since the pre-Islamic period. It is estimated that more than 20,000 Karizes were in use in the 20th century. Kariz which has been in their villages sometimes for centuries, and populations have modernized water supplies moving to tube and dug wells backed by diesel pumps.

However, the government of Afghanistan is aware of the importance of these structures and all efforts are being made to repair, reconstruct and maintain (through the community) the kariz. The Ministry of Rural Rehabilitation and Development along with National and International NGOs is making the effort.

There were functional qanat systems in 2009 in one area where American forces were reported to have unintentionally destroyed some of the channels during expansion of a military base, creating tensions between them and the local community. Some of these tunnels had been used to store supplies, and to move men and equipment underground.

Armenia

Qanats have been preserved in Armenia in the community of Shvanidzor, in the southern province of Syunik, bordering with Iran. Qanats are named kahrezes in Armenian. There are 5 kahrezes in Shvanidzor. Four of them were constructed in 12th to 14th Centuries, before the village was founded. The fifth kahrez was constructed in 2005. Potable water runs through I, II and V kahrezs. Kahrez III and IV are in quite poor condition. In the summer, especially in July and August, the amount of water reaches its minimum, creating a critical situation in the water supply system. Still, kahrezes are the main source of potable and irrigation water for the community.

Azerbaijan

Azerbaijan had numerous kahrizes many centuries ago. Archaeological findings suggest that long before the ninth century AD kahrizes were used to supply potable and irrigation water to their settlements. Traditionally, kahrizes were built and maintained by a group of masons called ‘Kankans’ with manual labour. The profession was, as in other countries handed down from father to son.

It is estimated that until the 20th century, nearly 1500 kahrizes, of which as many as 400 were in the Nakhichevan Autonomous Republic, existed in Azerbaijan. However, following the introduction of electric and fuel-pumped wells during Soviet times, kahrizes were neglected.

Today, it is estimated that 800 are still functioning in Azerbaijan. These operational kahrizes are key to the life of many communities.

China

The oasis of Turpan, in the deserts of Xinjiang in north-western China, uses water provided by qanat (locally called karez). There are nearly 1000 karez systems in the area and the total length of the canals is about 5,000 kilometres.

Turpan has long been the centre of a fertile oasis and an important trade centre along the Silk Road’s northern route, at which time it was adjacent to the kingdoms of Korla and Karashahr to the southwest. The historical record of the karez extends back to the Han Dynasty. The Turfan Water Museum is a Protected Area of the People’s Republic of China because of the importance of the Turpan karez water system to the history of the area.

turpan

Turpan qanat systems from the air.

The lines of sinking wells

India

In Karnataka, India, a Qanat-type structure called Suranga is used to tap underground water. However, these are rarely in use these days.

There are karez (qanat) systems in Gulburga, Bidar and Burhanpur “(Kundi Bhandara)” as well. The system in Bidar is said to extend two kilometres and originally had 21 vertical shafts. Only 17 shafts are visible today due to builders and developers closing 4. The karez vertical shafts are used by farmers and neighbourhood settlements. The Indian Heritage Cities Network Foundation (IHCNF) led by Valliyil Govindankutty has been working towards conservation of the Karez system. During its survey, IHCNF also discovered a royal bath (Bagh-e-Hammam) probably of the Bahmani period. Local knowledge claims the presence of a terra cotta pipe from the karez mouth to Bagh-e-Hammam.

Iran

iran

In the middle of the twentieth century, an estimated 50,000 qanats were in use in Iran, each commissioned and maintained by local users. Of these, only 37,000 remain in use as of 2015.

One of the oldest and largest known qanats is in the Iranian city of Gonabad, and after 2,700 years still provides drinking and agricultural water to nearly 40,000 people. Its main well depth is more than 360 meters and its length is 45 kilometres. Yazd, Khorasan and Kerman are zones known for their dependence on an extensive system of qanats.

In traditional Persian architecture, a Kariz (کاریز) is a small Qanat, usually within a network inside an urban setting. The Kariz is the structure that distributes a qanat to its final destinations. Qanats were used by early farmers and water supplies were brought to their fields of crops.

Many of the Iranian qanats are feats of engineering considering the intricate techniques used in their construction. The eastern and central regions of Iran hold the most qanats due to low precipitation and lack of permanent surface streams, whereas a small number of qanats can be found in the northern and western parts which receive more rainfall and enjoy some permanent rivers. Respectively the provinces Khorasan Razavi, Southern Khorasan, Isfahan and Yazd accommodate the most qanats, but from the viewpoint of water discharge the provinces Isfahan, Khorasan Razavi, Fars and Kerman are ranked first to forth.

Iran has a variable but, in general, arid climate, in which most of the relatively scant annual precipitation falls from October through April. In most of the country, yearly precipitation averages 250 millimetres or less. It is Henry Goblot in his book entitled “Qanats; a Technique for Obtaining Water” states that during the early first millennium BC, for the first time some small tribal groups gradually began immigrating to the Iranian plateau where there was less precipitation than in the territories they came from. They came from somewhere with many surface streams, so their agricultural techniques required more water than was available in the Iranian plateau. So they had no option but to fasten their hopes on the rivers and springs that originated in the mountains. They faced two barriers; the first was the seasonal rivers which had no water during the dry and hot seasons. The second was the springs that drained shallow groundwater and fell dry during the hot season. But they noticed some permanent runoff flowing through the tunnels excavated by the Acadian miners who were in search of copper. These farmers established a relationship with the miners and asked them to dig more tunnels in order to supply water. The miners accepted to do that, because there was no technical difficulty for them in constructing canals. In this manner, the ancient Iranians made use of the water that the miners wished to get rid of it, and founded a basic qanat system to supply the required water to their farm lands. According to Goblot, this innovation took place in the northwest of the present Iran somewhere bordering Turkey and later was introduced to the neighbouring Zagros Mountains.

sargon

Sargon II and a dignitary

According to an inscription left by Sargon II the king of Assyria, In 714 BC who captured the city of Uhlu lying in the northwest of Uroomiye Lake and part of the Urartu Empire, he noticed that the occupied area enjoyed a very rich vegetation even though there was no river running across it. He discovered the reason was water supplied by qanats. In fact it was Ursa, the king of the region, who had rescued the people from thirst and turned Uhlu into a prosperous and green land. Goblot believes that the influence of the Medeans and Achaemenids made the technology of qanat spread from Urartu (in the western north of Iran and near the present border between Iran and Turkey) to all over the Iranian plateau. It was an Achaemenid ruling that in case someone succeeded in constructing a qanat and bringing groundwater to the surface in order to cultivate land, or in renovating an abandoned qanat, the tax he was supposed to pay the government would be waived not only for him but also for his successors for up to 5 generations. During this period, the technology of qanat was in its heyday and it even spread to other countries. For example, following Darius’s order, Silaks the naval commander of the Persian army and Khenombiz the royal architect managed to construct a qanat in the oasis of Kharagha in Egypt. Beadnell believes that qanat construction dates back to two distinct periods: they were first constructed by the Persians, and later the Romans dug some other qanats during their reign in Egypt from 30 BC to 395 AD. The magnificent temple built in this area during Darius’s reign shows that there was a considerable population depending on the water of qanats. Ragerz has estimated this population to be 10,000 people. There are documents confirming the existence of qanats at this time written by Polibius who stated that: “the streams are running down from everywhere at the base of Alborz Mountain, and people have transferred much water from a long distance through some subterranean canals by spending much cost and labour”.

During the Seleucid Era, which began after the occupation of Iran by Alexander, it seems that the qanats were abandoned.

According to the historical records the Parthian kings did not care about the qanats the way the Achaemenid kings and even Sassanid kings did. As an instance, Arsac III, one of the Parthian kings, destroyed some qanats in order to make it difficult for Seleucid Antiochus to advance further while fighting him. The historical records from this time indicate a perfect regulation on both water distribution and farmlands. All the water rights were recorded in a special document which was referred to in case of any transaction. The lists of farmlands – whether private or governmental – were kept at the tax department. During this period there were some official rulings on qanats, streams, construction of dam, operation and maintenance of qanats. The government proceeded to repair or dredge the qanats that were abandoned or destroyed for any reason, and construct new qanats if necessary. A document written in the Pahlavi language pointed out the important role of qanats in developing the cities at that time. In Iran, the advent of Islam, which coincided with the overthrow of the Sassanid dynasty, brought about a profound change in religious, political, social and cultural structures. But the qanats stayed intact, because the economic infrastructure, including qanats was of great importance to the Arabs. As an instance Lombard reports that the Moslem clerics who lived during Abbasid period, such as Abooyoosef Ya’qoob (death 798 AD) stipulated that whoever can bring water to the idle lands in order to cultivate, his tax would be waived and he would be entitled to the lands cultivated. Therefore, this policy did not differ from that of the Achaemenids in not getting any tax from the people who revived abandoned lands. The Arabs’ supportive policy on qanats was so successful that even the holy city of Mecca gained a qanat. The Persian historian Hamdollah Mostowfi writes: “Zobeyde Khatoon (Haroon al-Rashid’s wife) constructed a qanat in Mecca. After the time of Haroon al-Rashid, during the caliph Moghtader’s reign this qanat fell into decay, but he rehabilitated it, and the qanat was rehabilitated again after it collapsed during the reign of two other caliphs named Ghaem and Naser. After the era of the caliphs this qanat completely fell into ruin because the desert sand filled it up, but later Amir Choopan repaired the qanat and made it flow again in Mecca.”

There are also other historical texts proving that the Abbasids were concerned about qanats. For example, according to the “Incidents of Abdollah bin Tahir’s Time” written by Gardizi, in the year 830 AD an earthquake struck the town of Forghaneh and reduced many homes to rubble. ‘The inhabitants of Neyshaboor used to come to Abdollah bin Tahir in order to request him to intervene, for they fought over their qanats and found no relevant instruction or law on qanats neither in the prophet’s (peace be upon him) quotations nor in the clerics’ writings. Abdollah bin Tahir brought together all the clergy from throughout Khorasan and Iraq to compile a book entitled “Alghani” (The Book of Qanat). This book collected all the rulings on qanats which could be of use by whoever wanted to judge a dispute over this issue. Gardizi added that this book was still applicable to his time, and everyone made references to it.’

During the Pahlavi period, the process of qanat construction and maintenance continued. A council responsible for the qanats was set up by the government. At that time most of the qanats belonged to landlords. In fact, feudalism was the prevailing system in the rural regions. The peasants were not entitled to the lands they worked on, but were considered only as the users of the lands. They had to pay rent for land and water to the landlords who could afford to finance all the proceedings required to maintain the qanats, for they were relatively wealthy. According to the report of Safi Asfiya, who was in charge of supervising the qanats of Iran in the former regime, in the year 1942 Iran had 40,000 qanats with a total discharge of 600,000 litres per second or 18.2 billion cubic meters per year. In 1961, another report was published revealing that in Iran there were 30,000 qanats of which just 20,000 were still in use, with a total output of 560,000 lit/se or 17.3 billion cubic meters per year. In 1959 a reform program named as the White Revolution was declared by the former Shah. One of the articles of this program addressed the land reform that let peasants take ownership of part of the landlords’ lands. In fact, the land reform meant that the landlords lost their motivation for investing more money in constructing or repairing the qanats which were subject to the Lnd Reform Law. On the other hand, the peasants could not come up with the money to maintain the qanats, so many qanats were gradually abandoned. The introduction of modern devices, that made it possible to drill many deep wells and extract groundwater much more quickly, accelerated the qanats’ destruction. The pumped wells had a negative impact on the qanats due to their overexploitation of the groundwater. These changes occurred in Mohammad Reza Shah’s reign inflicted great damage on the qanats of the country so that many vanished forever. The statistics related to 14,778 qanats estimates the overall discharge of these qanats to be 6.2 billion cubic meters per year between the years 1972 and 1973. If we assume the total number of the qanats at that time to be 32,000, their annual discharge would have amounted to 12 billion cubic meters. In 1963, the Ministry of Water and Electricity was established in order to provide the rural and urban areas of the country with sufficient water and electricity. Later, this Ministry was renamed the Ministry of Energy. Three years later, in 1966, the parliament passed a law protecting groundwater resources. According to this law, the Ministry of Water and Electricity was allowed to ban drilling any deep or semi-deep wells wherever surveys showed that the water table was dropping because of over pumping. In fact, this law was passed only after the growing number of the pumped wells sounded the alarm about over pumping and depletion of groundwater leading to the decline in qanat’ flow all over the country. This law, as well as the Law of Water Nationalization that was approved in 1968, and eventually the Law of Fair Distribution of water passed (in 1981) after the Islamic revolution emphasized the definition of restricted and free areas for drilling. In the restricted areas, drilling any wells (except for drinking and industry) was prohibited in order to prevent the continuous depletion of groundwater, so allowing the rest of the qanats to have a better chance of survival.

In the years 1984-1985 the ministry of energy noted 28038 qanats whose total discharge was 9 billion cubic meters. In the years 1992-1993 the census of 28054 qanats showed a total discharge of 10 billion cubic meters. 10 years later in 2002-2003 the number of qanats was reported as 33691 with a total discharge of 8 billion cubic meters.

qanat

Qanat maintenance Iran (ICQHS)

In 2000 the International Conference on Qanats in Yazd drew a lot of attention to the qanats. In 2005 the Iranian government and UNESCO signed an agreement to set up the International Centre on Qanats and Historic Hydraulic Structures (ICQHS) under the auspices of UNESCO. The main mission of this centre is the recognition, transfer of knowledge and experiences, promotion of information and capacities with regard to all the aspects of qanat technology and related historic hydraulic structures. This mission aims to fulfil sustainable development of water resources and the application of the outcome of the activities in order to preserve historical and cultural values as well as the promotion of the public welfare within the communities whose existence depends on the rational exploitation of the resources and preservation of such historical structures. Another mission is to promote research and development to restore the qanats and other traditional historic hydraulic structures for sustainable development objectives through international co-operation and global transfer of knowledge and technology. According to a report published in 2005 by the Water Resources Base Studies Department affiliated to the Ministry of Energy, there are 15 Regional Water Authorities throughout the country, based in 30 provinces, conducting research projects on water resources in 609 study sites. Each study site is the smallest research unit, containing one or several catchments. Out of 609 study sites, 214 sites with an overall area of 991,256 square kilometres have been declared as restricted regions, and 395 sites with an area of 630648 square kilometres are considered free. In the restricted regions there are 317,225 wells, qanats and springs that discharge 36,719 million cubic meters water a year, out of which 3409 million cubic meters is surplus to the aquifer capacity. This deficit in the volume of the aquifer reserves has led to a long-term groundwater level drop of 41 centimetres a year, on average. In the free regions, the number of wells, qanats and springs amounts to 241,091 with an output of 37,527 million cubic meters a year. Therefore, in 2005, in the country as a whole, there were 130,008 deep wells with a discharge of 31,403 million cubic meter, 33,804 semi deep wells with a discharge of 13,491 million cubic meters, 34,355 qanats with a discharge of 8,212 million cubic meters, and 55,912 natural springs with a discharge of 21,240 million cubic meters.

In 2014 scientists were performing rescue archaeology at the site of the future reservoir of the Seimar Dam. During this work remnants were uncovered that Iranian archaeologists claimed to be a water conduit from the late fourth millennium BC. If proven, this would be a possible forerunner of qanat technology some 2000 years earlier than is presently accepted.

Iraq

A survey of qanat systems in the Kurdish region of Iraq conducted by the Department of Geography at Oklahoma State University (USA) on behalf of UNESCO in 2009 found that out of 683 karez systems, some 380 were still active in 2004, but only 116 in 2009. Reasons for the decline of qanats include “abandonment and neglect” prior to 2004, “excessive pumping from wells” and, since 2005, drought. Water shortages are said to have forced, since 2005, over 100,000 people who depended for their livelihoods on karez systems to leave their homes. The study says that a single karez has the potential to provide enough household water for nearly 9,000 individuals and irrigate over 200 hectares of farmland. UNESCO and the government of Iraq plan to rehabilitate the karez through a Karez Initiative for Community Revitalization to be launched in 2010. Most of the karez are in Sulaymaniyah Governorate (84%). A large number are also found in Erbil Governorate (13%), especially on the broad plain around and within the city of Erbil.

Japan

In Japan there are several dozen qanat-like structures, locally known as ‘mambo’ or ‘manbo’, most notably in the Mie- and Gifu Prefectures. Whereas some link their origin clearly to the Chinese karez, and therefore to the Iranian source, a Japanese conference in 2008 found insufficient scientific studies to evaluate the origins of the mambo.

Jordan

Among the qanats built in the Roman Empire, the 94 km long Gadara Aqueduct in northern Jordan was possibly the longest continuous qanat ever built. Partly following the course of an older Hellenistic aqueduct, excavation work arguably started after a visit by Emperor Hadrian in 129-130 AD. The Gadara Aqueduct was never quite finished and was put in service only in sections.

 

Pakistan

The Chagai district is in the north west corner of Baluchistan, Pakistan, bordering with Afghanistan and Iran. Qanats, locally known as karezes, are found more broadly in this region. They are spread from Chaghai district all the way up to Zhob district. A number of them are present in Qilla Abdullah and Pishin. Karezes are also extensively found in the neighbouring areas of Afghanistan such as Kandahar. The remains of karezes found in different parts of the district are attributed to ic influence.

Syria

Qanats were found over much of Syria. The widespread installation of groundwater pumps has lowered the water table and damaged some qanat systems. Qanats have gone dry and been abandoned across the country.

Oman

In Oman from the Iron Age Period (found in Salut, Bat and other sites) a system of underground aqueducts called Falaj were constructed, a series of well-like vertical shafts, connected by gently sloping horizontal tunnels. There are three types of Falaj: Daudi (داوودية) with underground aqueducts, Ghaili (الغيلية) requiring a dam to collect the water, and Aini (العينية) whose source is a water spring. These enabled large scale agriculture to flourish in a dry land environment. According to UNESCO, some 3,000 aflaj are still in use in Oman today. Nizwa, the former capital city of Oman, was built around a falaj which is still in use today. In July 2006, five representative examples of this irrigation system were inscribed as a World Heritage Site.

 

United Arab Emirates

Screen Shot 2016-01-17 at 20.13.04

The falaj irrigation system at Al Ain Oasis

The oasis of Al Ain, on the border with Oman, uses traditional falaj (qanat) irrigation for the palm groves and gardens.

Egypt

There are four main oases in the Egyptian desert. The Kharga Oasis is one that has been extensively studied. There is evidence that as early as the second half of the 5th century BC water brought in qanats was being used. The qanats were excavated through water-bearing sandstone rock, which seeps into the channel, with water collected in a basin behind a small dam at the end. The width is approximately 60 cm, but the height ranges from 5 to 9 meters; it is likely that the qanat was deepened to enhance seepage when the water table dropped (as is also seen in Iran). From there the water was used to irrigate fields.

There is another instructive structure located at the Kharga oasis. A well that apparently dried up was improved by driving a side shaft through the easily penetrated sandstone (presumably in the direction of greatest water seepage) into the hill of Ayn-Manâwîr to allow collection of additional water. After this side shaft had been extended, another vertical shaft was driven to intersect the side shaft. Side chambers were built, and holes bored into the rock — presumably at points where water seeped from the rocks — are evident.

Screen Shot 2016-01-17 at 20.13.50

Exit of a foggara in Libya

David Mattingly reported foggara extending for hundreds of miles in the Garamantes area near Jarma in Libya: “The channels were generally very narrow – less than 2 feet wide and 5 high – but some were several miles long, and in total some 600 foggara extended for hundreds of miles underground. The channels were dug out and maintained using a series of regularly spaced vertical shafts, one every 30 feet or so, 100,000 in total, averaging 30 feet in depth, but sometimes reaching 130.

Tunisia

The foggara water management system in Tunisia, used to create oases, is similar to that of the Iranian qanat. The foggara is dug into the foothills of a fairly steep mountain range such as the eastern ranges of the Atlas Mountains. Rainfall in the mountains enters the aquifer and moves toward the Saharan region to the south. The foggara, 1 to 3 km in length, penetrates the aquifer and collects water. Families maintain the foggara and own the land it irrigates over a ten-meter width, with width reckoned by the size of plot that the available water will irrigate.

 

Algeria

Screen Shot 2016-01-17 at 20.14.41

Water “metering” through a distribution weir on a foggara in Algeria

Water “metering” through a distribution weir on a foggara in Algeria

Qanats or foggaras are the source of water for irrigation in large oases like that at Gourara. The foggaras are also found at Touat (an area of Adrar 200 km from Gourara). The length of the foggaras in this region is estimated to be thousands of kilometres.

Although sources suggest that the foggaras may have been in use as early as 200 AD, they were clearly in use by the 11th century after the Arabs took possession of the oases in the 10th century and the residents embraced Islam.

The water is metered to the various users through the use of distribution weirs that meter flow to the various canals, each for a separate user.

The humidity of the oases is also used to supplement the water supply to the foggara. The temperature gradient in the vertical shafts causes air to rise by natural convection, causing a draft to enter the foggara. The moist air of the agricultural area is drawn into the foggara in the opposite direction to the water run-off. In the foggara it condenses on the tunnel walls and the air passes out of the vertical shafts. This condensed moisture is available for reuse.

Morocco

In southern Morocco, the qanat (locally khettara) is also used. On the margins of the Sahara Desert, the isolated oases of the Draa River valley and Tafilalt have relied on qanat water for irrigation since the late 14th century. In Marrakech and the Haouz plain, the qanats have been abandoned since the early 1970s, having dried up. In the Tafilaft area, half of the 400 khettaras are still in use. The Hassan Adahkil Dam’s impact on local water tables is said to be one of the many reasons for the loss of half of the khettara.

The black berbers of the south were the hereditary class of qanat diggers in Morocco who build and repair these systems.

sinking

Qanat sinking wells or shafts in Morocco

Greece

The Tunnel of Eupalinos on Samos runs for 1 kilometre through a hill to supply water to the town of Pythagorion. It was built on the order of Polycrates around 550 BC. At either end of the tunnel proper, shallow qanat-like tunnels carried the water from the spring to the town.

Italy

The 5,653 m long Claudius Tunnel, intended to drain the largest Italian inland water, Lake Fucine, was constructed using the qanat technique. It featured shafts up to 122 m deep. The entire ancient town of Palermo in Sicily was equipped with a huge qanat system built during the Arabic period (827–1072). Many of the qanats are now mapped and some can be visited. The famous Scirocco room has an air-conditioning system cooled by the flow of water in a qanat and a “wind tower”, a structure able to catch the wind and use it to draw the cooled air up into the room.

Luxemburg

The Raschpëtzer near Helmsange in southern Luxembourg is a particularly well preserved example of a Roman qanat. It is probably the most extensive system of its kind north of the Alps. To date, some 330 m of the total tunnel length of 600 m have been opened up. Thirteen of the 20 to 25 shafts have been investigated. The qanat appears to have provided water for a large Roman villa on the slopes of the Alzette valley. It was built during the Gallo-Roman period, probably around the year 150 and functioned for about 120 years.

Spain

There are still many examples of galeria or qanat systems in Spain, most likely brought to the area by the Moors during their rule of the Iberian Peninsula. Turrillas in Andalusia on the north facing slopes of the Sierra de Alhamilla has evidence of a qanat system. Granada is another site with an extensive qanat layout.

The Americas

Qanats in the Americas, usually referred to as filtration galleries, can be found in the Nazca region of Peru and in northern Chile. The Spanish are said to have introduced qanats into Mexico in 1520 but it has been found that some installations may predate the invasion.

 

 

 

 

Author: admin

Enjoy this Post? Share it on your favorite social bookmarking site...

Submit to Mixx Submit to StumbleUpon Submit to Delicious Submit to Digg

Comments are closed.

Related Posts

Check out some more great tutorials and articles that you might like.

Designed & Maintained by Online Toolbox Ltd