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103-524: The archaeological landmarks are still evidence of the ancient heritage of the state, where there are about 142 towers, and three castles, one of which is "Al Awamir Castle" and two castles in the town of "Al Qaryatayn", in addition to the presence of a number of archaeological houses, the most important of which are "Al Nazar and Al Yamin", along with a large fortress that was built during the reign of Said bin Sultan and some parts of it have been demolished due to

206-630: A confining layer, often made up of clay. The confining layer might offer some protection from surface contamination. If the distinction between confined and unconfined is not clear geologically (i.e., if it is not known if a clear confining layer exists, or if the geology is more complex, e.g., a fractured bedrock aquifer), the value of storativity returned from an aquifer test can be used to determine it (although aquifer tests in unconfined aquifers should be interpreted differently than confined ones). Confined aquifers have very low storativity values (much less than 0.01, and as little as 10 ), which means that

309-499: A crew of four workers can excavate a horizontal length of 40 m (130 ft) per day. When the vertical shaft reaches 40 m (130 ft), they can excavate only 20 meters horizontally per day and at 60 m (200 ft) in depth this drops below 5 horizontal meters per day. In Algeria, a common speed is just 2 m (6.6 ft) per day at a depth of 15 m (49 ft). Deep, long qanats (which many are) require years and even decades to construct. The excavated material

412-415: A critical situation in the water supply system. Still, kahrezes are the main source of potable and irrigation water for the community. Aquifer An aquifer is an underground layer of water -bearing material, consisting of permeable or fractured rock, or of unconsolidated materials ( gravel , sand , or silt ). Aquifers vary greatly in their characteristics. The study of water flow in aquifers and

515-403: A million cubic kilometers of "low salinity" water that could be economically processed into potable water . The reserves formed when ocean levels were lower and rainwater made its way into the ground in land areas that were not submerged until the ice age ended 20,000 years ago. The volume is estimated to be 100 times the amount of water extracted from other aquifers since 1900. An aquitard

618-452: A qanat is stored in a reservoir, typically with night flow stored for daytime use. An ab anbar is an example of a traditional Persian qanat-fed reservoir for drinking water. The qanat system has the advantage of being resistant to natural disasters such as 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

721-416: A qanat system had to be carefully situated, to make best use of the slow flow of water. In Iran, there were subterranean mills at Yazd and Boshruyeh ; at Taft and Ardestan mills were placed at the outflow from the qanat, before irrigation of the fields. 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

824-442: A rock unit of low porosity is highly fractured, it can also make a good aquifer (via fissure flow), provided the rock has a hydraulic conductivity sufficient to facilitate movement of water. Challenges for using groundwater include: overdrafting (extracting groundwater beyond the equilibrium yield of the aquifer), groundwater-related subsidence of land, groundwater becoming saline, groundwater pollution . Aquifer depletion

927-433: A side shaft through the easily penetrated sandstone (presumably in the direction of greatest water seepage) into the hill of Ayn-Manâwîr (also written Ayn-Manawir  [ fr ] 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

1030-523: A small dam at the end. The width is approximately 60 cm (24 in), 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

1133-605: A state contract] burdened with gifts. They travelled six months, came to me [Aššurbanipal], asked of my condition and beseeched my rule." Some believe that Izki was mentioned in Neoassyrian cuneiform texts from Nineveh. Serious archaeological fieldwork began in Izki with J. Schreiber (2007). He strove to contextualise this centre amongst other large oases in Oman by means of archaeological survey. In order to reach this goal, he studied

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1236-400: 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, reels to raise the container to the surface at the shaft head, hatchets and shovels for excavation, lights, and spirit levels or plumb bobs and string. Depending upon

1339-518: A sustainability perspective, qanats are powered only by gravity and thus have low operation and maintenance costs. Qanats transfer fresh water from the mountain plateau to the lower-lying plains with saltier soil. This helps to control soil salinity and prevent desertification . The qanat should not be confused with the spring-flow tunnel typical to the mountainous area around Jerusalem . Although both are excavated tunnels designed to extract water by gravity flow, there are crucial differences. Firstly,

1442-515: A ten-meter width, with length reckoned by the size of plot that the available water will irrigate. 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 9,370 karizes were in use in the 20th century. The oldest functional kariz which is more than 300 years old and 8 kilometers long is located in Wardak province and

1545-440: A two-dimensional slice of the aquifer) appear to be layers of alternating coarse and fine materials. Coarse materials, because of the high energy needed to move them, tend to be found nearer the source (mountain fronts or rivers), whereas the fine-grained material will make it farther from the source (to the flatter parts of the basin or overbank areas—sometimes called the pressure area). Since there are less fine-grained deposits near

1648-416: A well in a fracture trace or intersection of fracture traces increases the likelihood to encounter good water production. Voids in karst aquifers can be large enough to cause destructive collapse or subsidence of the ground surface that can initiate a catastrophic release of contaminants. Groundwater flow rate in karst aquifers is much more rapid than in porous aquifers as shown in the accompanying image to

1751-587: Is a problem in some areas, especially in northern Africa , where one example is the Great Manmade River project of Libya . However, new methods of groundwater management such as artificial recharge and injection of surface waters during seasonal wet periods has extended the life of many freshwater aquifers, especially in the United States. The Great Artesian Basin situated in Australia

1854-554: Is a zone within the Earth that restricts the flow of groundwater from one aquifer to another. An aquitard can sometimes, if completely impermeable, be called an aquiclude or aquifuge . Aquitards are composed of layers of either clay or non-porous rock with low hydraulic conductivity . Groundwater can be found at nearly every point in the Earth's shallow subsurface to some degree, although aquifers do not necessarily contain fresh water . The Earth's crust can be divided into two regions:

1957-1019: Is arguably the largest groundwater aquifer in the world (over 1.7 million km or 0.66 million sq mi). It plays a large part in water supplies for Queensland, and some remote parts of South Australia. Discontinuous sand bodies at the base of the McMurray Formation in the Athabasca Oil Sands region of northeastern Alberta , Canada, are commonly referred to as the Basal Water Sand (BWS) aquifers . Saturated with water, they are confined beneath impermeable bitumen -saturated sands that are exploited to recover bitumen for synthetic crude oil production. Where they are deep-lying and recharge occurs from underlying Devonian formations they are saline, and where they are shallow and recharged by surface water they are non-saline. The BWS typically pose problems for

2060-501: Is considered to be a high rate for porous aquifers, as illustrated by the water slowly seeping from sandstone in the accompanying image to the left. Porosity is important, but, alone , it does not determine a rock's ability to act as an aquifer. Areas of the Deccan Traps (a basaltic lava) in west central India are good examples of rock formations with high porosity but low permeability, which makes them poor aquifers. Similarly,

2163-421: Is held in place by surface adhesive forces and it rises above the water table (the zero- gauge-pressure isobar ) by capillary action to saturate a small zone above the phreatic surface (the capillary fringe ) at less than atmospheric pressure. This is termed tension saturation and is not the same as saturation on a water-content basis. Water content in a capillary fringe decreases with increasing distance from

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2266-568: Is still providing water to nearly 3,000 people. Many of these ancient structures were destroyed during the Soviet–Aghan War and the War in Afghanistan . Maintenance has not always been possible. The cost of labour has become very high, and maintaining the kariz structures is no longer possible. Lack of skilled artisans who have the traditional knowledge also poses difficulties. A number of

2369-466: Is supported by the historian Albert T. Olmstead . 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 BCE 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

2472-419: Is the level to which water will rise in a large-diameter pipe (e.g., a well) that goes down into the aquifer and is open to the atmosphere. Aquifers are typically saturated regions of the subsurface that produce an economically feasible quantity of water to a well or spring (e.g., sand and gravel or fractured bedrock often make good aquifer materials). An aquitard is a zone within the Earth that restricts

2575-403: 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 define 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

2678-453: 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

2781-644: Is very common for a qanat to start below the foothills of mountains, where the water table is closest to the surface. From this source, the qanat tunnel slopes gently downward, slowly converging with the steeper slope of the land surface above, and the water finally flows out above ground where the two levels meet. To connect a populated or agricultural area with 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 and evaporation. In some cases water from

2884-427: The saturated zone or phreatic zone (e.g., aquifers, aquitards, etc.), where all available spaces are filled with water, and the unsaturated zone (also called the vadose zone ), where there are still pockets of air that contain some water, but can be filled with more water. Saturated means the pressure head of the water is greater than atmospheric pressure (it has a gauge pressure > 0). The definition of

2987-783: The Atlas Mountains in North Africa, the Lebanon and Anti-Lebanon ranges between Syria and Lebanon, the Jebel Akhdar in Oman, parts of the Sierra Nevada and neighboring ranges in the United States' Southwest , have shallow aquifers that are exploited for their water. Overexploitation can lead to the exceeding of the practical sustained yield; i.e., more water is taken out than can be replenished. Along

3090-615: The Guarani people , it covers 1,200,000 km (460,000 sq mi), with a volume of about 40,000 km (9,600 cu mi), a thickness of between 50 and 800 m (160 and 2,620 ft) and a maximum depth of about 1,800 m (5,900 ft). The Ogallala Aquifer of the central United States is one of the world's great aquifers, but in places it is being rapidly depleted by growing municipal use, and continuing agricultural use. This huge aquifer, which underlies portions of eight states, contains primarily fossil water from

3193-876: The Indian subcontinent for a long time. Cotton appears in the Inquiry into Plants by Theophrastus and is mentioned in the Laws of Manu . As transregional trade networks expanded and intensified, cotton spread from its homeland to India and into the Middle East. One theory is that the qanat was developed to irrigate cotton fields, first in what is now Iran, where it doubled the amount of available water for irrigation and urban use. Because of this, Persia enjoyed larger surpluses of agricultural products, thus increasing urbanization and social stratification. The qanat technology subsequently spread from Persia westward and eastward. In

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3296-667: The United Arab Emirates , and uyūn in Saudi Arabia , etc. The largest extant and functional qanat systems are located in Afghanistan, Algeria, Iran, Oman , Pakistan, and the oases of the Turfan region in Xinjiang , Northwestern China . This is a system of water supply that allows water to be transported over long distances in hot dry climates without losing much of the water to evaporation . The system has

3399-661: The depositional sedimentary environment and later natural cementation of the sand grains. The environment where a sand body was deposited controls the orientation of the sand grains, the horizontal and vertical variations, and the distribution of shale layers. Even thin shale layers are important barriers to groundwater flow. All these factors affect the porosity and permeability of sandy aquifers. Sandy deposits formed in shallow marine environments and in windblown sand dune environments have moderate to high permeability while sandy deposits formed in river environments have low to moderate permeability. Rainfall and snowmelt enter

3502-481: The groundwater . Much of the population of Iran and other arid countries in North Africa and West Asia historically depended upon the water from qanats; many populated areas are close to the areas where qanats are possible. Common variants of qanat in English include kanat , khanat , kunut , kona , konait , ghanat , ghundat . Qanāh ( قناة ) is an Arabic word that means "channel". In Persian ,

3605-445: The province of Khorasan have been recorded with vertical shafts of up to 275 m (902 ft). The vertical shafts support construction and maintenance of the underground channel as well as air interchange. Deep shafts require intermediate platforms to facilitate the process of removing soil. The construction speed depends on the depth and nature of the ground. If the earth is soft and easy to work, at 20 m (66 ft) depth

3708-516: 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 (0.62 to 1.9 mi) in length, penetrates the aquifer and collects water. Families maintain the foggara and own the land it irrigates over

3811-570: The National Center for Statistics and Information for the year 2012. The majority of them are Sunni Muslims. Some of its popular and traditional arts include Razha, Al-Azi, sword fighting, and Ta'awib, which is one of the women's arts. These include leather tanning, spinning, weaving, silverware manufacturing, palm weaving, as well as trade, construction, woodworking, and blacksmithing. It has 20 schools at all educational levels, and several government offices that provide necessary services to

3914-669: The United States accelerated in the late 1940s and continued at an almost steady linear rate through the end of the century. In addition to widely recognized environmental consequences, groundwater depletion also adversely impacts the long-term sustainability of groundwater supplies to help meet the Nation’s water needs." An example of a significant and sustainable carbonate aquifer is the Edwards Aquifer in central Texas . This carbonate aquifer has historically been providing high quality water for nearly 2 million people, and even today,

4017-404: The advantage of being resistant to natural disasters such as 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. Karez are constructed as a series of well-like vertical shafts, connected by a gently sloping tunnel. This taps into underground water and delivers it to

4120-421: The aquifer is storing water using the mechanisms of aquifer matrix expansion and the compressibility of water, which typically are both quite small quantities. Unconfined aquifers have storativities (typically called specific yield ) greater than 0.01 (1% of bulk volume); they release water from storage by the mechanism of actually draining the pores of the aquifer, releasing relatively large amounts of water (up to

4223-574: The arid coastal desert of Peru, a technology of water supply similar to that of the qanats, called puquios , was developed. Most archaeologists believe that the puquios are indigenous and date to about 500 CE, but a few believe they are of Spanish origin, brought to the Americas in the 16th century. Puquios were still in use in the Nazca region in the 21st century. In arid and semi-arid regions, owing to high evaporation, transportation routes were in

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4326-488: The capital, Muscat. It has adopted the Royal Canal as its emblem. Legendarily, Izki is Oman's oldest city. Popularly revered 'oldest cities' are claimed the world over, the historicity of which usually rests on local pride. Its ancient aflaj (water canals) probably nourished such beliefs. The twin walled towns, Izki/al-Yemen and al-Nizar, differ from each other in size and appearance. The former presently has half of

4429-612: The characterization of aquifers is called hydrogeology . Related terms include aquitard , which is a bed of low permeability along an aquifer, and aquiclude (or aquifuge ), which is a solid, impermeable area underlying or overlying an aquifer, the pressure of which could lead to the formation of a confined aquifer. The classification of aquifers is as follows: Saturated versus unsaturated; aquifers versus aquitards; confined versus unconfined; isotropic versus anisotropic; porous, karst, or fractured; transboundary aquifer. Groundwater from aquifers can be sustainably harvested by humans through

4532-409: The coastlines of certain countries, such as Libya and Israel, increased water usage associated with population growth has caused a lowering of the water table and the subsequent contamination of the groundwater with saltwater from the sea. In 2013 large freshwater aquifers were discovered under continental shelves off Australia, China, North America and South Africa. They contain an estimated half

4635-487: The complexity of karst aquifers. These conventional investigation methods need to be supplemented with dye traces , measurement of spring discharges, and analysis of water chemistry. U.S. Geological Survey dye tracing has determined that conventional groundwater models that assume a uniform distribution of porosity are not applicable for karst aquifers. Linear alignment of surface features such as straight stream segments and sinkholes develop along fracture traces . Locating

4738-526: The compound Kh and Kv values are different (see hydraulic transmissivity and hydraulic resistance ). When calculating flow to drains or flow to wells in an aquifer, the anisotropy is to be taken into account lest the resulting design of the drainage system may be faulty. To properly manage an aquifer its properties must be understood. Many properties must be known to predict how an aquifer will respond to rainfall, drought, pumping, and contamination . Considerations include where and how much water enters

4841-474: 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 1,000 years. By 400 BCE, Persian engineers had mastered

4944-437: 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 (66–115 ft). 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,

5047-526: The different contexts of key sites in Central Oman first hand as a pottery specialist. The poor preservation of such continuously occupied sites scared off most archaeologists. In his survey J. Schreiber tallied in and immediately around the old twin towns 1045 sites (2007: 124) ranging from the Hafit to Islamic periods. In 2011, excavation and survey partly confirmed Schreiber's results. The town contains

5150-414: 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. The choice of the slope is a trade off between erosion and sedimentation. Highly sloped tunnels are subject to more erosion as water flows at a higher speed. On

5253-439: The drainable porosity of the aquifer material, or the minimum volumetric water content ). In isotropic aquifers or aquifer layers the hydraulic conductivity (K) is equal for flow in all directions, while in anisotropic conditions it differs, notably in horizontal (Kh) and vertical (Kv) sense. Semi-confined aquifers with one or more aquitards work as an anisotropic system, even when the separate layers are isotropic, because

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5356-469: The effort. There were still functional qanat systems in 2009. 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 were used to store supplies, and to move men and equipment underground. Qanats have been preserved in Armenia in the community of Shvanidzor , in

5459-557: The fissures. The enlarged fissures allow a larger quantity of water to enter which leads to a progressive enlargement of openings. Abundant small openings store a large quantity of water. The larger openings form a conduit system that drains the aquifer to springs. Characterization of karst aquifers requires field exploration to locate sinkholes, swallets , sinking streams , and springs in addition to studying geologic maps . Conventional hydrogeologic methods such as aquifer tests and potentiometric mapping are insufficient to characterize

5562-478: The flow of groundwater from one aquifer to another. A completely impermeable aquitard is called an aquiclude or aquifuge . Aquitards contain layers of either clay or non-porous rock with low hydraulic conductivity . In mountainous areas (or near rivers in mountainous areas), the main aquifers are typically unconsolidated alluvium , composed of mostly horizontal layers of materials deposited by water processes (rivers and streams), which in cross-section (looking at

5665-459: 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. Qanat irrigation technology was introduced to Egypt by the Achaemenid king Darius I during his reign of 522 BCE-486 BCE, which

5768-447: The form of qanats, which led groundwater to consumption areas along underground tunnels. In the long run, the qanat system is not only economical but also sustainable for irrigation and agricultural purposes.… The ground water flow was known to depend on grain size of sediments, and, therefore, the tunnels in qanats are filled in with coarser material than the surrounding host geological formations. The qanats are constructed mainly along

5871-849: 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 overground. 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

5974-526: The groundwater from rainfall and snowmelt, how fast and in what direction the groundwater travels, and how much water leaves the ground as springs. Computer models can be used to test how accurately the understanding of the aquifer properties matches the actual aquifer performance. Environmental regulations require sites with potential sources of contamination to demonstrate that the hydrology has been characterized . Porous aquifers typically occur in sand and sandstone . Porous aquifer properties depend on

6077-610: The groundwater where the aquifer is near the surface. Groundwater flow directions can be determined from potentiometric surface maps of water levels in wells and springs. Aquifer tests and well tests can be used with Darcy's law flow equations to determine the ability of a porous aquifer to convey water. Analyzing this type of information over an area gives an indication how much water can be pumped without overdrafting and how contamination will travel. In porous aquifers groundwater flows as slow seepage in pores between sand grains. A groundwater flow rate of 1 foot per day (0.3 m/d)

6180-427: 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 (see 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

6283-522: 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 windcatchers 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. Qanats (designated foggaras in Algeria ) are

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6386-450: The large farmers are abandoning their kariz which has been in their families sometimes for centuries, and moving to tube and dug wells backed by diesel pumps. However, the government of Afghanistan was aware of the importance of these structures and all efforts were made to repair, reconstruct and maintain (through the community) the kariz. The Ministry of Rural Rehabilitation and Development along with national and international NGOs made

6489-491: The left. For example, in the Barton Springs Edwards aquifer, dye traces measured the karst groundwater flow rates from 0.5 to 7 miles per day (0.8 to 11.3 km/d). The rapid groundwater flow rates make karst aquifers much more sensitive to groundwater contamination than porous aquifers. In the extreme case, groundwater may exist in underground rivers (e.g., caves underlying karst topography . If

6592-423: The lower reaches are the most likely to see substantial reductions in flow. Traditionally qanats are built by a group of skilled laborers, muqannīs , with hand labor. The profession historically paid well and was typically handed down from father to son. 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

6695-586: The main course of the Ziz River and its subsequent 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 ( haratin ) of the south were the hereditary class of qanat diggers in Morocco who build and repair these systems. Their work was hazardous. The foggara water management system in Tunisia, used to create oases, is similar to that of

6798-462: The micro-porous (Upper Cretaceous ) Chalk Group of south east England, although having a reasonably high porosity, has a low grain-to-grain permeability, with its good water-yielding characteristics mostly due to micro-fracturing and fissuring. Karst aquifers typically develop in limestone . Surface water containing natural carbonic acid moves down into small fissures in limestone. This carbonic acid gradually dissolves limestone thereby enlarging

6901-562: The most prominent tourist attractions in the state is "Al Maliki Canal", which gained its name from Malik bin Fahm Al Azdi, as well as "Ghar Wajranan", which is surrounded by many intertwined stories between reality and fiction. Located in the Al-Dakhiliyah Governorate, historians say that they date back to the 3rd millennium BC. The Zakiet archaeological tombs are situated on a cylindrical-shaped hill overlooking

7004-432: 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 depth of the water table and determine whether

7107-449: The neighborhood, 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

7210-413: 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

7313-454: 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 natural spring to renew or increase flow following a recession of the water table. Secondly, the shafts essential for the construction of qanats are not essential to spring-flow tunnels. A typical town or city in Iran, and elsewhere where the qanat

7416-418: The other hand, less sloped tunnels need frequent maintenance due to the problem of sedimentation. A lower downward gradient also contributes to reducing the solid contents and contamination in water. 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

7519-512: The outlet. When the qanat is still below ground, the water is drawn to the surface via wells or animal driven Persian wells . Private subterranean reservoirs could supply houses and buildings for domestic use and garden irrigation as well. 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

7622-570: The passage of time and erosion factors. One of the states in the Interior Governorate. It is bordered by Al Jabal Al Akhdar to the west, and by the states of Manah and Nizwa to the west and south. It is bordered by the state of Samail to the north and by the state of Al Mudhaibi in the North Eastern Governorate to the east. Its area is approximately 2500 square kilometers and it is about 138 kilometers away from

7725-419: The people of Azki used to worship an idol in the form of a golden calf named Jarnan, adorned with jewelry and precious gems. When the people of Azki embraced Islam, the calf was hidden inside a cave beneath the village of Nazar, and it was guarded by magical incantations. Since that day, no one has seen the calf. The total population of the state of Izki is 36,296 people, consisting of 4,492 families according to

7828-416: The phreatic surface. The capillary head depends on soil pore size. In sandy soils with larger pores, the head will be less than in clay soils with very small pores. The normal capillary rise in a clayey soil is less than 1.8 m (6 ft) but can range between 0.3 and 10 m (1 and 33 ft). The capillary rise of water in a small- diameter tube involves the same physical process. The water table

7931-400: The population. It also has a center for agricultural development, a municipal center, an electricity office, a post office, a police center, a Sharia court, an office for the governor, as well as tourist parks, restaurants, and recreational places. URL: http://edoc.ub.uni-muenchen.de/7548/ Qanat A qanat or kārīz is a system for transporting water from an aquifer or well to

8034-664: 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 to contribute of the community using the qanat, and the existence of a functioning water-rights system. The primary applications of qanats are for irrigation, providing cattle with water, and drinking water supply. Other applications include watermills, cooling and ice storage. Watermills within

8137-658: 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 1971 Hassan Adahkil Dam 's build in

8240-419: The qanat. And misreading the soil conditions leads to collapses, which at best require extensive rework and at worst are fatal for the crew. 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. The crew typically begins from

8343-402: The recovery of bitumen, whether by open-pit mining or by in situ methods such as steam-assisted gravity drainage (SAGD), and in some areas they are targets for waste-water injection. The Guarani Aquifer , located beneath the surface of Argentina , Brazil , Paraguay , and Uruguay , is one of the world's largest aquifer systems and is an important source of fresh water . Named after

8446-688: The remains of the entire pre-Islamic period. Numerous were the finds of the Early Iron Age and Late Iron Age . Particularly eroded and disturbed was al-Nizar. Excavation of the highest part of Al-Yemen revealed an older mosque, presumably that destroyed during the civil war (886-970 AD). On the other side of the Wadi Khalfayn lies a large cemetery which contains pottery sherds of the Samad Late Iron Age , but of other periods as well. The graves are mostly of this period. One of

8549-653: The rocks—are evident. David Mattingly reports foggara extending for hundreds of miles in the Garamantes area near Germa 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." In southern Morocco,

8652-429: The same geologic unit may be confined in one area and unconfined in another. Unconfined aquifers are sometimes also called water table or phreatic aquifers, because their upper boundary is the water table or phreatic surface (see Biscayne Aquifer ). Typically (but not always) the shallowest aquifer at a given location is unconfined, meaning it does not have a confining layer (an aquitard or aquiclude) between it and

8755-450: 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 (3.1 miles), while some have been measured at ≈70 km (43 miles) in length near Kerman . The vertical shafts usually range from 20 to 200 m (66 to 656 ft) in depth, although qanats in

8858-420: The soil type, qanat liners (usually fired clay hoops) may also be required. Although the construction methods are simple, the construction 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

8961-458: The source of water for irrigation in large oases like 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 kilometers. Although sources suggest that the foggaras may have been in use as early as 200 CE, they were clearly in use by the 11th century after the Arabs took possession of

9064-425: The source, this is a place where aquifers are often unconfined (sometimes called the forebay area), or in hydraulic communication with the land surface. An unconfined aquifer has no impermeable barrier immediately above it, such that the water level can rise in response to recharge. A confined aquifer has an overlying impermeable barrier that prevents the water level in the aquifer from rising any higher. An aquifer in

9167-571: 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 before the village was founded. The fifth kahrez was constructed in 2005. Potable water runs through three of them, and two are in poor condition. In the summer, especially in July and August, the amount of water reaches its minimum, creating

9270-419: The surface are not only more likely to be used for water supply and irrigation, but are also more likely to be replenished by local rainfall. Although aquifers are sometimes characterized as "underground rivers or lakes," they are actually porous rock saturated with water. Many desert areas have limestone hills or mountains within them or close to them that can be exploited as groundwater resources. Part of

9373-639: The surface area as the latter. In 1908 the estimated number of houses in al-Nizar at 450, and in al-Yemen at 350, which contradicts this. Al-Nizar is still inhabited; al-Yemen has been deserted since prior to 1980, but the owners still care for their own houses. The present appearance, especially the regular streets, results from the 18th century destruction and rebuilding of al-Yemen. Early Iron Age Izki appears to find mention in cuneiform texts. According to Neoassyrian sources, in 640 BCE, "Pade, king of Qade, who lives in Izke…sent envoys to cultivate good relations [and

9476-426: The surface by gravity, without need for pumping. The vertical shafts along the underground channel are for maintenance purposes, and water is typically used only once it emerges from the daylight point. The qanats still create a reliable supply of water for human settlements and irrigation in hot, arid , and semi-arid climates, but the value of this system is directly related to the quality, volume, and regularity of

9579-742: The surface through an underground aqueduct ; the system originated approximately 3,000 years ago in Iran . The function is essentially the same across the Middle East and North Africa , but the system operates under a variety of regional names: qanat or kārīz in Iran, karez in Afghanistan and Pakistan , foggara in Algeria , qanat in Malta , khettara in Morocco , falaj in Oman and

9682-420: The surface. The term "perched" refers to ground water accumulating above a low-permeability unit or strata, such as a clay layer. This term is generally used to refer to a small local area of ground water that occurs at an elevation higher than a regionally extensive aquifer. The difference between perched and unconfined aquifers is their size (perched is smaller). Confined aquifers are aquifers that are overlain by

9785-431: 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 a yakhchal (ice pit). In winter, the qanat water would be channeled to the north side of the wall, whose shade made the water freeze more quickly, increasing the ice formed per winter day. Then

9888-618: The time of the last glaciation . Annual recharge, in the more arid parts of the aquifer, is estimated to total only about 10 percent of annual withdrawals. According to a 2013 report by the United States Geological Survey (USGS), the depletion between 2001 and 2008, inclusive, is about 32 percent of the cumulative depletion during the entire 20th century. In the United States, the biggest users of water from aquifers include agricultural irrigation and oil and coal extraction. "Cumulative total groundwater depletion in

9991-443: The use of qanats leading to a well. This groundwater is a major source of fresh water for many regions, however can present a number of challenges such as overdrafting (extracting groundwater beyond the equilibrium yield of the aquifer), groundwater-related subsidence of land, and the salinization or pollution of the groundwater. Aquifers occur from near-surface to deeper than 9,000 metres (30,000 ft). Those closer to

10094-533: The valleys where Quaternary sediments are deposited. Qanats are constructed as a series of well -like vertical shafts , connected by a gently sloping tunnel which carries a water canal . Qanats efficiently deliver large amounts of subterranean water to the surface without need for pumping. The water drains by gravity, typically from an upland aquifer , with the destination lower than the source. Qanats allow water to be transported over long distances in hot dry climates without much water loss to evaporation . It

10197-472: The village. They consist of two walls made of mountain rocks resembling the shape of a beehive cell. The presence of tombs on the top of the hill leads researchers to believe that the site was used as a fortress to repel invading armies. Jarnan Cave is located in the Azki state and dates back to the pre-Islamic era. It is situated on an unstable rocky hill, overlooking the ancient neighborhood of Al-Nazar. The cave

10300-410: The water table is the surface where the pressure head is equal to atmospheric pressure (where gauge pressure = 0). Unsaturated conditions occur above the water table where the pressure head is negative (absolute pressure can never be negative, but gauge pressure can) and the water that incompletely fills the pores of the aquifer material is under suction . The water content in the unsaturated zone

10403-738: The words for "qanat" are kārīz (or kārēz ; كاريز ) and is derived from earlier word kāhrēz ( كاهریز ). The word qanāt ( قنات ) is also used in Persian. Other names for qanat include kahan ( Persian : کهن ); Kahn ( Balochi ); kahriz/kəhriz ( Azerbaijan ); khettara ( Morocco ); Galerías , minas or viajes de agua (Spain); falaj ( Arabic : فلج ) ( United Arab Emirates and Oman ); foggara/fughara ( North Africa ). Alternative terms for qanats in Asia and North Africa are kakuriz , chin-avulz , and mayun . According to most sources, qanat technology

10506-597: Was developed in ancient Iran by the Persians sometime in the early 1st millennium BCE and slowly spread westward and eastward from there. Other sources suggest a Southeast Arabian origin. Analogous systems appear to have been developed independently in China and in South America (specifically, southern Peru ). A cotton species, Gossypium arboreum , is indigenous to South Asia and has been cultivated on

10609-513: Was named Jarnan after the old name of the state in the pre-Islamic era. The entrance to the cave is in front of the Halfeen Valley. It was previously said that a person could only enter the cave by crawling, but due to erosion, these openings have become almost invisible. The length of the cave extends from approximately 15 to 20 meters. Many stories circulate about Jarnan Cave, although many locals deny their validity. The legends say that

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