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The scarcity of water in arid lands highlights the importance of qanats, whereas in the populated areas of the Kavir borders, groundwater utilization by deep tube wells stresses and gradually dries out the ancient qanats. This case study is from the history and fate of ancient qanats in Abarkoh Plain, where is located in the western part of the Gavkhoni-Abarkoh-Sirjan depression in central Iran. The studied area is a large Quaternary alluvial fan (more than 35 km long and 20 km wide) in the western border of Abarkoh depression, which terminates into a playa lake in the center of this depression. The reason for the drying up of ancient qanats has been studies based on the rock-facies analysis of the exposed geology and 1400 recently drilled samples from 94 shallow and deepwater wells. The Abarkoh qanats are constructed in the proximal to mid-fan deposits of the alluvial fans. The tube wells are also scattered in this area and in the distal part of the alluvial fans, where they grade into the playa lake sediments. The complex distribution of the basin-fill deposits (alluvial fan to playa sediments) mainly controlled the position, water discharge and quality of the aquifers. The recoverable groundwater is also within the karstified, coral-algal limestones of the Qom Formation, which occurs as shallow to deep, confined and unconfined aquifers under the mid-fan sediments. The relation between the depth of qanats (mother wells and galleries) and adjacent, recently drilled, deep tube wells, controlled their competition in water discharge. Drop in water tables, not only dried most of the qanats, but also changed the quality of water, due to the penetration of the salty water of the playa lake to the upper-hand aquifers.
This study highlights the contrast between the use of deepwater tube wells and the life of ancient qanats. The greatest effort and achievement in ground-water utilization by ancient people in arid lands and Kavir borders is under threat. This needs to be considered carefully because the level of underground water table in Kavir borders (salt-flat apron) and its effect on desertification is a well-known fact.