Applying the management scenarios in prediction of groundwater level fluctuations by using the conceptual and mathematical MODFLOW model (Case study: Khezel-Nahavand Plain)

Groundwater resources are the main source of water supply in many arid countries such as Iran. Because of uncontrolled increasing of the population, limitation of surface water resources and excessive extraction from aquifers, sharp drop in groundwater level in many plains such as Khezel plain located in Hamedan province was occurred. Khezel plain is important because of strategic crop farming and water supply for the region. so needs serious qualitative and quantitative studies on its groundwater resources. In this study quantitative model of the aquifer was prepared with MODFLOW code. By the trial and error method the model was first calibrated in the both conditions: steady flow condition for October 2006 and unsteady flow condition from September 2006 to July 2007 then validated in October 2008. During the model calibration in steady condition, hydraulic conductivity of aquifer material and conductance coefficient of rivers bed and general head boundaries were optimized. On the other hand, specific yield and specific storage coefficients of the aquifer material were elevated through the model calibration in unsteady condition. After the model validation and confidence to the model result the water level fluctuations was predicted for one, three and 10 year later in two approaches: current conditions and applying the management scenario by 10% reduction in discharge of pumping wells. The results showed that, the most amount of ground water level drop occurs in the northeast area of the plain. The amounts of this water level drop were calculated 1.82, 3.6 and 8.2 meters for one, three and 10 years later respectively. But with applying the management scenario, the amounts of water level drop were calculated 0.52, 2.7 and 7.07 meters for the mentioned years.