Assessment of Vulnerability Index and Risk Zoning in Ardabil Plain

Determining the vulnerability and risk of groundwater is a good approach for groundwater management with reliable and accurate models, taking into account surface pollutants, the ability to contaminate groundwater, and the pathways affecting wells. In the present study, this evaluation is based on a new index with three factors of pollutant point source density, intrinsic vulnerability and contamination range of wells presented for a groundwater aquifer in Ardabil. A modified version of the Drastic method was used to map the intrinsic groundwater vulnerability of the study area to an area of 886 square kilometers. Density of point source pollutants were measured such as industries, villages, gas stations in the sub basins and used as potential indicators of point source pollutants. Numerical modeling was also performed to determine the catchment areas using MODFLOW and MODPATH models. The spatial and descriptive integration of these three factors created a mechanism and vulnerability index for assessing the risks of groundwater contamination as well as identifying and prioritizing areas requiring groundwater monitoring. The parameters used in this method were sensitivity analysis. The results of this index were calibrated based on nitrate and chloride concentration which had a positive correlation with the vulnerability index. Groundwater vulnerability and risk index values vary from zero to one thousand with respect to the integration of 3 factors with a value range of 10. The value of this index was low in most of the lowlands. But maximum values of this index were in populated areas, high roads and industrial areas in Ardabil plain. In general, according to this indicator, Ardabil plain is at low vulnerability and risk. This research will lead to a rigorous and cost-effective approach to protecting drinking and agricultural water resources and achieving sustainable groundwater for future generations.