GIS Based Fuzzy Optimization Method to Groundwater Vulnerability Evaluation

Recognition of groundwater vulnerability to pollution will help in protection groundwater sources and managing groundwater quality conflicts. The DRASTIC model has been used as a valuable tool for assessing groundwater vulnerability over the large geographical areas involving a variety of hydrogeological settings. DRASTIC index uses linear model to calculate the final vulnerability index and the factor that influence the groundwater vulnerability must be divided into ranges and then be given ratings. This system is unable to describe a continuous transition from the easiest to be polluted to the most difficult to be polluted that is fuzzy nature of the groundwater vulnerability to pollution. In this paper, GIS based fuzzy optimization model has been presented to evaluate the groundwater vulnerability to pollution by taking the fuzziness into consideration. Finally, the result is compared with DRASTIC method in a case study of Kathmandu Valley basin, Nepal. It is shown that the fuzzy optimization method incorporates more efficiently the fuzzy nature of the groundwater vulnerability to pollution and is more applicable in reality.