A numerical study on land subsidence due to extensive overexploitation of groundwater in Aliabad plain, Qom-Iran

Over the last decade, many areas of Iran have been increased in suffering from land subsidence due to a large exploitation of groundwater, needed to cope with the water scarcity caused by low precipitation. The plateau of Qom, especially the area of Aliabad village (Aliabad plain), has encountered many problems due to subsidence which occurs as cracks in building walls and fractures in wells. In this paper, we are going to evaluate land subsidence in some parts of Qom plateau, in particular Aliabad plain, by a numerical model (PLAXIS(A (R)) 3D; v1.6) considering aquifer pressure changes, hydrological and geotechnical data. Results of the study reveal that since 2001-2013, the average groundwater level decline was measured 26.35 m and the corresponding subsidence had been 0-76 cm in different areas of the plain. Response of the saturated geologic units toward the changes in ground water level due to groundwater extraction and, in turn, land subsidence depends on the characteristics of geological materials in the units. Moreover, the units containing a combination of grain and fine soil, such as sand and clay which are completely different in the geotechnical parameters, tend to react differently due to all changes in the groundwater level.