Spatial analysis of aquifer vulnerability using DRASTIC, SI, GODS and SINTACS models, (Study area: Mashhad Plain aquifer - Northeast Iran)

Abstract The vulnerability of the Mashhad aquifer has been analyzed by spatial analysis approach using DRASTIC, SI, GODS and SINTACS models. The Mashhad aquifer in northeast Iran is now considered a critical area due to its special circumstances, the presence of industrial and agricultural activities, and large settlements. This study aims to evaluate the vulnerability zones of the Mashhad aquifer using four models DRASTIC, SI, GODS and SINTACS. The parameters of the models are explained and measured by GIS capabilities. After weighting, ranking, and integrating the layers in the ArcGIS software, we have produced vulnerability maps of the aquifer. The results have indicated that in the DRASTIC model, the study area is categorized into five vulnerability zones very low (5.81%), low (26.03%), moderate (44.45%), high (22.57%), and very high (1.13%). In the SI model, the study area is categorized into five vulnerability zones very low (0.40%), low (24.63%), moderate (23.98%), high (18.71%), and very high vulnerability (32.25%). In the GODS model, it is categorized into five vulnerability zones very low (0.93%), low (31.11%), moderate (11.45%), high (1.56%), and very high (54.95%). In the SINTACS model, the area is also categorized into the vulnerability five zones very low (0.44%), low (25.57%), moderate (28.58%), high (2.79%), and very high (42.61%). For validating the results, the vulnerability maps have been compared with the TDS quality index. The results showed that all four models have high accuracy in categorizing the vulnerability of the Mashhad aquifer. The comparison among the results of the models has indicated that the vulnerability of the aquifer generally increases from southeast to northwest and then decreases from the central region towards the northwestern areas.