Hamid Kardan Moghaddam - Department of Water Resources Study and Research, Water Research Institute, Tehran, Iran.
Mohsen Pourreza Bilondi - Associate Professor of Water Engineering Department, University of Birjand.
Masoud Bahrainimotlagh - Department of Water Resources Study and Research, Water Research Institute, Tehran, Iran.

Due to population growth and political development of Birjand city, the status of aquifer vulnerability is important for development. Studies on the DRASTIC index indicate the lack of consideration of land use status and the effect of pollutant transfer on aquifer vulnerability. DRASTIC-LU index has eight parameters and since the incoming weights to this index can be a matter of taste, the model was calibrated according to the Nitrate concentration in the wells of the region. The model was calibrated by using AHP method and the completion of questionnaires was analyzed from the point of view of the importance of each parameter in terms of weight and rank. Questionnaire analysis was performed by couple comparison method and using Expert choice software. The calibrated results indicate an increase in the correlation coefficient between the vulnerability index and the Nitrate concentration at the aquifer. The results showed that land use was positive due to the surface concentration of pollutants in the agricultural and urban sectors, which played an important role in the vulnerability index of aquifers. The results also showed that the accuracy of the vulnerability index could be increased by using the proposed method of this research and calibrate weights and ranks by using the hierarchical analysis method. The correlation between Nitrate concentration and DRASTIC-LU index in the aquifer had increased from ۴۲% to ۶۵%.

Vulnerability, Land use, DRASTIC, LU, Calibration, Nitrate