Environmental issues and water resources in dryland alluvial fans: Examples from central Iran

Water has been always a major constrain and a core basis for the growth of urban centers and the vital environmental issues affecting the nation's social and economic goals in drylands. However, alluvial fan systems provide water resources in such environmental settings and the large fans are usually the suitable areas for developing urban areas. This has been well recognized by ancient people who lived in arid lands of central Iran. They developed the cities based on the traditional water harvesting system and potential water reservoirs in alluvial fans. However, climatic changes, increasing population and industrialization, during the last five decades, made that the water resources quite inadequate and a competition happened to pump out water from the shallow to deep aquifers along the proximal (upstream) areas to distal (downstream) parts of the alluvial-fan systems. This resulted in serious environmental problems, depending on the geographic positions of the urban areas on the fan surface. Desertification, wind erosion/deposition, water and soil salinity crisis and immigrations affected and especially concentrated in the cities and villages located in the down-fan areas.