Analysis of Land Subsidence with Groundwater Numerical Modeling in Najaf Abad Plain, Iran
Nagheli, Setareh1; Samani, Nozar1; Shirani, Kourosh2; Pasandi, Mehrdad2
1Shiraz University, IRAN, ISLAMIC REPUBLIC OF; 2University of Isfahan, IRAN, ISLAMIC REPUBLIC OF
Iran is large country, arid, with a poor distribution of surface water. On the other hand, the distribution of precipitation and surface water in most areas is not consistent with the water needed for agriculture. Thus, groundwater is the most important source of the agriculture water in the country. Pumping wells are the most common way of extracting groundwater. Concentration of pumping wells causes large drawdown, increases effective pressure and creates permanent compaction of sediments and land subsidence. This phenomenon is observed in many plains in Iran. Najaf Abad is one of these plains. In this plain, subsidence was calculated 40 cm in 21 years by the National Survey Organization. This plain is located in the west of Isfahan city and has 14000 pumping wells. In this thesis, subsidence is analyzed with numerical groundwater modeling. For this purpose, in the first step of analysis groundwater flow was simulated for the period of 2004 to 2009 using MODFLOW 2000 linked to GMS software. In the next step of analysis, output data from groundwater model was entered to PMWIN software (another component of GMS) for the subsidence modeling. In addition, European Space Agency's data was used for the calibration of subsidence model. The data was from 2007 to 2009. In this stage, 3 DEM maps were simulated via D-InSAR method; these were used as observation data in numerical model to calculate elastic and inelastic specific storage. When the elastic and inelastic storage factors were calibrated in IBS package, the model was run for future years with different pumping rates. The main result of this research and the only solution to reduce subsidence is reducing pumping rate in Najaf Abad plain by 50%.