Determining the groundwater quality protection zone by considering the vulnerability of aquifer

In most areas, much of the drinking water supplies from groundwater resources are constantly threatened by various pollutants. In this paper, the groundwater quality protection zone is defined using MODFLOW, WhAEM2000 and DRASTIC models. In this research at the beginning, the conceptual model of Rudan plain aquifer has been made by MODFLOW model. The model is calibrated for the year of 1389-90 in the steady state with the root mean square error about 1.49 m error. Also, the model is calibrated for the period 1389-91 with the root mean square error about 2.32. Then, the groundwater quality protection zone is determined by using WhAEM2000 model in both constant radius and analytical methods. Finally, the vulnerability level of the aquifer was identified by using the DRASTIC model and considered for determining the protection zone area.Results showed that most of the wells are located in the highly vulnerable zone with agricultural land use. So, Because of the high risk of groundwater pollution, extra travel time for groundwater (about 10 years) must be considered for determination of protection zone. Also, for less vulnerable areas and other land use areas, a smaller protection area can be applied, since the application of greater zone in these areas will lead to a lot of social and economic costs.