Integrated variable weight model and improved DRASTIC model for groundwater vulnerability assessment in a shallow porous aquifer

•The DRASTIC and DRASHCL models were used for aquifer vulnerability assessment.•AHP and VWM methods were used to optimize the weight of the parameters in vulnerability assessment.•NO− 3, Mg2+ and COD concentration from the wells were used to verify the results of the models.•The inclusion of VWM-DRASHCL model was more reasonable for the groundwater evaluation.