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Parker Robinson
Parker Robinson

Qanat



Abstract:In this paper, we report the results of our work on automated detection of qanat shafts on the Cold War-era CORONA Satellite Imagery. The increasing quantity of air and space-borne imagery available to archaeologists and the advances in computational science have created an emerging interest in automated archaeological detection. Traditional pattern recognition methods proved to have limited applicability for archaeological prospection, for a variety of reasons, including a high rate of false positives. Since 2012, however, a breakthrough has been made in the field of image recognition through deep learning. We have tested the application of deep convolutional neural networks (CNNs) for automated remote sensing detection of archaeological features. Our case study is the qanat systems of the Erbil Plain in the Kurdistan Region of Iraq. The signature of the underground qanat systems on the remote sensing data are the semi-circular openings of their vertical shafts. We choose to focus on qanat shafts because they are promising targets for pattern recognition and because the richness and the extent of the qanat landscapes cannot be properly captured across vast territories without automated techniques. Our project is the first effort to use automated techniques on historic satellite imagery that takes advantage of neither the spectral imagery resolution nor very high (sub-meter) spatial resolution.Keywords: remote sensing; archaeology; qanat; karez; deep learning; convolutional neural networks (CNNs); image segmentation; CORONA; Kurdistan Region of Iraq (KRG)




qanat



Therefore, the key to generating frigid temperatures seems to be that there are very few cracks at the base of the thick structure below, but there is a significant air gap above the qanat (a water management system used to provide a reliable supply of water to human settlements or for irrigation in hot, arid and semi-arid climates). A qanat has quite a lot of water inside, because there are frequent well-like reservoirs along its path. Completely shaded from the sun, a qanat also aggregates the cold, sinking air of the night, which is then trapped within, unable to rise up to the less dense surface air. A windcatcher, however, can create a pressure gradient which sucks at least a small amount of air upwards through a house. This cool, dry night air, being pulled over a long passage of water, evaporates some of it and is cooled down further.


Over the last 30 years, the use of thermoplastic adhesives has become an established choice of treatment in the support of fragile textiles. During that time, the Textile Conservation Section at the Victoria and Albert Museum has evolved an expertise in the application of the poly (vinyl acetate) emulsion Mowilith DMC2 when such a treatment is appropriate. The methods of application are continually being refined. The recent conservation of an early 18th century chintz qanat for the Nehru Gallery of Indian Art afforded an opportunity to clarify thinking about the use of adhesive techniques and to further refine methods, in particular, the use of low pressures on the vacuum hot table.


The qanat (Museum no. IM29 1928) is one panel, measuring 71 by 217 cm, cut from a larger length of repeated niches which would have formed a tent wall (Fig.1). Off-set from the centre there is a vertical seam made with long loose running stitches along the selvedge allowances of two part loom-widths of plain weave cotton. The chintz design is made in the traditional kalamkari technique of printing, mordant dyeing and overpainting to produce a predominance of red and green with purple, brown and yellow, the natural ground of the cotton left to depict the main motifs of the irises and surrounding flowers.


To use a stitching technique alone to support the qanat would only cause more disintegration of the degraded brown and purple motifs and leave them vulnerable to further deterioration: the passage of a needle through these would invariably break up the weave structure and couching threads would not be sufficient to prevent continuing breakdown of the brittle fibre. However, an adhesive technique could first be used to consolidate both the fibre and the weave and then stitching could complement this treatment by helping to hold the most vulnerable areas in contact with the support when the textile was hanging for display.


The consolidated textile could now be given a secondary backing of cotton lawn, supporting first throughout with an alternating grid of staggered running stitches (Skala polyester thread) and then more specifically in the most degraded and damaged and still vulnerable areas with laid couching stitches (pulled Stabiltex thread). For display the top edge of the qanat was held over the curve of a roller (attached by an apron) and allowed to hang freely down.


A combination of techniques was thought to be the most appropriate treatment to support the qanat. Stitching could have been employed alone to give overall support to the textile but would not have prevented further breakdown and loss from the already deteriorating areas. Adhesion alone would help consolidate the fibre and the weave but would not give sufficient long term support for a textile which was to be displayed hanging under its own weight.


A qanat (from Template:Lang-ar) or kareez (from Template:Lang-fa) is a water management system used to provide a reliable supply of water to human settlements or for irrigation in hot, arid and semi-arid climates. The widespread distribution of qanat known in different places in their local names has confounded the question of its origin,[1] but the earliest evidence of this technology dates back to ancient Persia,[2] and spread during the Arab Muslim conquests, to the Iberian peninsula, southern Italy and North Africa.[3]


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. To reach an underground aquifer qanats must often be of extreme length.[4]


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 after the surface outlet. Water from the qanats defines both the social regions in the city and the layout of the city.[4]


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 grade, the water is drawn to the surface via Ater-wells or animal driven Persian wells. Private subterranean reservoirs could supply houses and buildings for domestic use and garden irrigation as well. Further, air flow from the qanat is used to cool an underground summer room (shabestan) found in many older houses and buildings.[4]


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, then the route is laid out aboveground.[6][4]


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, spirit levels or plumb bobs and string. Depending upon the soil type, qanat liners (usually fired clay hoops) may also be required.[6][4]


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.[6]


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.[6][4]


Most qanats in Iran run less than 5 km. The overall length of the qanat often runs up to 16 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 in Iran 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 spoils.[6][4]


The qanat's water-carrying channel is 50-100 cm wide and 90-150 cm high. The 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 which are established result in severe erosion and 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.[6][4]


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