Assessment of Vulnerability in the Gonabad Plain using the DRASTIC Model

Groundwater serves as a vital resource for agricultural, domestic, and industrial purposes, particularly in arid and semi-arid regions. The increasing pressure on groundwater resources, driven by population growth, climate change, and overexploitation, has rendered them increasingly susceptible to contamination from anthropogenic activities. Excessive use of chemical fertilizers in agriculture, improper disposal of urban and industrial wastewater, and leakage of pollutants from various sources are among the primary contributors to groundwater pollution. Assessing the vulnerability of these resources is essential for ensuring their quality and sustainability. Using the DRASTIC model, this study evaluates the groundwater vulnerability of the Gonabad Plain, situated in Khorasan Razavi Province, Iran. This model incorporates seven hydrogeological parameters: depth to the water table, net recharge, aquifer media, soil media, topography, unsaturated zone, and hydraulic conductivity. The DRASTIC index calculated for the study area ranges from ۶۳ to ۱۹۳. According to the results, the pollution risk levels in the region were classified as follows: ۰.۶۵% of the area had no pollution risk, ۲.۰۶% was categorized as very low risk, ۲۱.۶۷% as low risk, ۳۴.۶۲% as low to moderate risk, ۳۳.۵۲% as moderate to high risk, ۶.۶۶% as high risk, ۰.۸% as very high risk, and ۰.۰۰۶% was identified as thoroughly contaminated areas. The increased vulnerability index observed in the northern parts of the plain can be attributed to factors such as a shallower water table, gentle slopes (less than ۲%), and coarse-grained soils in both the aquifer and the unsaturated zone. To validate the vulnerability assessment, nitrate concentration data from wells in the region, collected in ۲۰۲۱, were analyzed. The findings confirmed the accuracy of the DRASTIC model in identifying areas vulnerable to landslides. This study underscores the importance of localized assessments of groundwater vulnerability. It emphasizes the need for targeted management and monitoring strategies in high-risk regions to mitigate pollution and ensure the long-term sustainability of groundwater resources.

کلیدواژه ها:

Groundwater ، Vulnerability ، Pollution potential ، Gonabad plain ، DRASTIC