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Title: ACCESS TO WATER RESOURCES IN DIFFERENT PARTS OF ALLUVIAL MEGAFANS, EXAMPLES FROM ARID LANDS OF CENTRAL IRAN

Author: N. Arzani

Year: 2009

Publisher: European Water Resources Association (EWRA)

Description:

The increasing demand for freshwater supplies as the result of growing populations and industrialization is in contrast with the limited water supplies in arid and semi-arid countries worldwide. Water scarcity has been of concern in arid and semi-arid lands of Central Iran since ancient people invented Qanats as a potential technology to harvest the underground water. However, the challenge of sustainable water management has been magnified by the climate, geomorphology and inherited social issues. The arid lands of Central Iran have only one main sources of renewable freshwater that is limited rainfall, occasionally transformed into flash floods. The best renewable water resources in these arid lands are the natural groundwater reservoirs developed in alluvial megafans, where the ancient people well recognized to dig the long underground tunnels of Qanats. Climatic fluctuations accentuated by periodic drought, affect water availability in cities built upon these alluvial megafans while this resulted quite different situations in wells and Qanats drilled in different parts of these megafans. The sedimentary facies association of alluvial megafans represents the ideal water reservoirs in semiarid to arid lands. Megafan has been defined as a large (103-105 km2), fan shaped mass of sediment deposited by the migration of a permanent or intermittent channelized stream with a point source from the outlet of a large mountainous drainage network. These fans are usually characterized by the large size of the catchment, which is capable to conduct water to the apex of the fan and sedimentary basins adjacent to mountain belts.
The morphology, facies distribution and tectonics control the distribution of recharge, lateral flow, and discharge zones in the fan aquifers. This study highlights the importance of alluvial megafans as the potential water reservoirs in arid land and with examples from central Iran demonstrates how the high quantity of groundwater pumping in proximal to distal areas of the megafans, associated with rural development in these areas, could bring along serious environmental problems. One of the key points to focus is the past and future of
Qanats, the greatest effort and achievement in ground-water utilization by ancient people, who well recognized the importance of alluvial-fan aquifers in arid lands.