What is Obruk

Land subsidence which is defined as gradual settling or sudden collapse of Earth's surface, is a geohazard phenomenon that occurs worldwide. Land subsidence occurs in time mainly due to excessive groundwater abstraction. This problem occurs usually in semi-arid regions where the groundwater is the sole source of water. Eliminating the adverse effects of land subsidence requires careful observations on the temporal change of elevation coupled with groundwater flow modeling. In this study, numerical groundwater flow modeling technique is applied to a confined aquifer system in the Konya Subbasin of Konya Closed Basin (KCB), central Anatolia, Turkey. Groundwater head in the KCB has been declining with a rate of about 1m/year since early 1980s. Recent GPS observations reveal subsidence rates of 22 mm/year over the southern part of KCB. MODFLOW numerical groundwater flow model coupled with subsidence (SUB) package is used to simulate the effect of long term groundwater abstraction on the spatial variation of subsidence rates.