Groundwater Vulnerability Evaluation of Tehran-Karaj Aquifer Using DRASTIC Method and Fuzzy Logic

In recognition of the need for effective and efficient methods for protecting groundwater resources from future contamination, scientists and resource managers have sought to develop aquifer vulnerability assessment techniques for predicting which areas are more likely than others to become contaminated as a result of activities at or near the land surface. This research is focused on the evaluation of Tehran- Karj groundwater vulnerability to pollution. Among several assessment methods, DRASTIC has been selected for this study. A major portion of Tehran’s drinking water is supplied from groundwater. ArcGIS has been used to overlay and calculate different layers and obtain the vulnerability map. In addition, groundwater balance has been evaluated in order to calculate the net recharge parameter in DRASTIC index. About 50 percent of the aquifer has been classified as moderate and almost 20 percent has low pollution vulnerability. The Boolean algorithm is usually used in categorizing the index but it is proved that using the Boolean algorithm causes the discrepancy in classification. On the other hand, fuzzy algorithm can produce more accurate results. Therefore, in this research, both Boolean and Fuzzy algorithms were used and compared together. Fuzzy algorithm could recognize the areas with low and very low vulnerability potentials while the Boolean model was not able to do so, therefore, the fuzzy model showed better performance. According to the developed map, most of the areas in the moderate class and very high class had the minimum area in the region.