An Estimation of Aquifer Vulnerability Subjected to Agricultral Activities: A Case Study of Tabriz Aquifer

The best solution to protect the aquifers is preventing the entrance of contamination to aquifers instead of remediating the contaminated aquifers. To do this، the vulnerability of aquifers should be evaluated. In this study، DRASTIC، SINTACS and SI models were used to evaluate the intrinsic vulnerability in Tabriz aquifer. To this، were prepared the data included the aquifer media، vadose zone media، water table، recharge rate، soil media، hydraulic conductivity، topography and land use map and then zonation map of the vulnerability for each model. To evaluate the performance of the models، the correlation between vulnerability index and nitrate concentration were calculated. Regarding to confidence level of calculated correlation index، the map of aquifer vulnerability was calibrated using the parameter modification method. The results showed that modified DRASTIC model with 0. 724 correlation index is the best model for evaluating of aquifer vulnerability. Finally، by overlaying the vulnerability and land use maps، were determined the areas affected by contamination from agricultural activities. According to this، the most areas of the study area have been located in average and low vulnerability risk and 4. 31% in high vulnerability risk. Hence، to prevent increasing of vulnerability of aquifer suggested the using fertilizer and pesticide decrease in the agricultural lands in Tabriz plain.