Groundwater Vulnerability Assessment for Nitrate Pollution Based on Modified Drastic Method: A Case Study in Southwest China

Groundwater vulnerability assessment using DRASTIC is an important tool for groundwater pollution prevention and management.However, traditional DRASTIC methods are not suitable for accurate assessment of groundwater vulnerability in hilly and mountainous regions of southern China.The improved method in this paper retains the basic structure of DRASTIC, and obtains more accurate evaluation results by adding parameters and modifying parameter rating Scale and weights.Comparison of the modified DRASTIC-LY vulnerability map with the map of original DRASTIC-LY method revealed differences in 28.6% of the study area.The risk map shows that the very high vulnerability area decreased from 3.6% to 2.1%, while the high vulnerability area increased from 9.4% to 5.6%.Areas with low vulnerability increased by 10.7%, while areas with medium vulnerability increased by 4.9%.The areas with very high groundwater vulnerability are mainly distributed at the confluence of the Han River and Baojiang River, the areas with high groundwater vulnerability are mainly distributed in the southeast of Mian County, Nanzheng County, Chenggu County and Yang County, while the areas with low groundwater vulnerability are distributed in the northern part of the basin.The Pearson's correlation factor was 0.55 in the original DRASTIC model, 0.58 in the DRASTIC-LY method, and 0.65 in the modified DRASTIC-LY model, which indicated that the revised DRASTIC-LY model was more appropriate than that constructed by the original model.The vulnerability map of the DRASTIC-LY model can assist government planning and decision-making departments to facilitate water resource protection and water quality control.