Vulnerability Assessment of Oshnavieh Plain Aquifer by SINTACS and DRASTIC Models

This study carried out for considering the intrinsic vulnerability of Oshnavieh plain aquifer using from DRASTIC and SINTACS models with respect to increasing groundwater resources contaminations and quality deterioration by agricultural activities, industrial and urban development. Although, cleaning up of groundwater contamination is very costly and long process and often occurs when contamination is detected that decontamination of the aquifer is almost impossible. One of the methods for preventing groundwater pollution, identify areas vulnerable aquifer. For both models, seven hydrological and hydrogeological parameters such as depth to water table, net recharge, aquifer media, soil media, the impact of the unsaturated zone, hydraulic conductivity and topography were used. After preparing the layers of each of the parameters in the GIS, the layers have been combined together and the final map was prepared for the plain vulnerability. For ensuring from results of the vulnerability models nitrate data collected from 25 agricultural wells in September 2015 were used. For models optimization and efficiency, the correlation between each of the parameters with the values of nitrate was considered and according to the correlation results and expertise the model parameters were changed and the weight of each final map was prepared. Corrected DRASTIC and SINTACS models showed 76.3 and 67.56 percent correlation with nitrate values respectively. Vulnerability index obtained for corrected DRASTIC was from 68 to 191 and for the SINTACS from 108 to 224. The results showed that both Corrected DRASTIC and SINTACS models are appropriate to determine the vulnerability of Oshnavieh plain. The corrected DRASTIC and SINTACS model determines the intrinsic vulnerability of the plain better than the corrected SINTACS model. according to DRASTIC and SINTACS vulnerability models have the highest potential vulnerability of Central Plains and the Southwest and Plains Margin the least amount of potential vulnerability.