Assessing the vulnerability of groundwater to pollution in Ireland based on the COST-620 Pan-European approach

•We assessed the intrinsic and specific vulnerability of groundwater.•We applied global sensitivity analysis to identify the most significant parameters.•We validated the method in karst areas using total organic carbon.•The results comply with the conceptual model of groundwater vulnerability in Ireland.

The aim of the analysis was to assess the intrinsic and specific vulnerability of groundwater to pollution from pesticides in Ireland at the national scale. A methodology to incorporate the effect of groundwater recharge in vulnerability assessment is described which can be particularly useful for the evaluation of dilution of groundwater pollutants. A sensitivity analysis using Monte-Carlo simulation revealed that the most important parameters of the model were subsoil (ρ = 0.79) and topsoil (ρ = 0.72), which is in agreement with the current knowledge of the parameters that have a significant effect on groundwater vulnerability in Ireland. The intrinsic vulnerability assessment was verified using total organic carbon (TOC) concentration in groundwater, a novel approach for the validation of groundwater vulnerability methods at regional scales. A statistical analysis showed that TOC concentration was significantly different (p < 0.001) between watersheds classified as highly vulnerable and watersheds classified as less vulnerable, providing evidence that the developed method can effectively classify karst areas in terms of groundwater vulnerability.