Optimizing the DRASTIC Method for Nitrate Pollution in Groundwater Vulnerability Assessments: a Case Study in China

摘要

Groundwater vulnerability assessments, using DRASTIC, are important and useful tools for groundwater pollution prevention and control. The DRASTIC method, however, is not appropriate for accurate specific vulnerability assessments where nitrate concentrations are high. A new method has been developed that retains the basic structure of DRASTIC while adding or subtracting parameters, and modifying the parameter ratings and weightings. The resulting DRACILM model was used to assess vulnerability to nitrate pollution in the West Liaohe Plain and as a basis for vulnerability mapping. The accuracy, appropriateness, and reliability of the vulnerability mapping were analyzed using a group of integrated indicators, such as correlation, ANOVA F-statistics, and single-parameter sensitivity analysis. The correlation between vulnerability class and the concentration of NO3-N in the DRACILM model improved to 0.649, which was 40.6% higher than that obtained by DRASTIC. The ANOVA F-statistic was 27.71, which indicated a lower overlap between the mean values of nitrates in the different vulnerability classes. The single-parameter sensitivity analysis revealed that land use type exhibited the highest and hydraulic conductivity the lowest effective weighting values. The vulnerability maps by DRACILM model could assist planners and government decision-makers with preliminary investigations into planning water protection projects or establishing management scenarios for water resource quality.