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.

Agricultural irrigation strongly affects groundwater pollution in cultivated areas. Groundwater vulnerability was evaluated using the DRASTIC method by considering agricultural activities that affect water infiltration and pollutant transport to the groundwater. Three scenarios, using different water recharge sources and calculation methods, were considered for the Tongliao area of northern China. For Scenario 1, only precipitation contributed to the net recharge estimation and ~33.77% of the area was under high pollution risk. For Scenarios 2 and 3, both precipitation and irrigation return water were considered for net recharge estimations. The fractional areas of high pollution risk regions were 40.60% and 19.22% for Scenarios 2 and 3, respectively. The modified infiltration coefficients for this study area were used in Scenario 3, and the fractional area of the high-risk region was 21.38% lower than for Scenario 2. The use of empirical infiltration coefficients in Scenario 2 overestimated the water infiltration ability in the cultivated areas, which also overestimated the fractional area of high-risk regions in this study. Accurate assessment of the impact of agricultural activities on the groundwater pollution risk is essential for cultivated areas. Emphasis should be placed on the calculation method of proper parameters for DRASTIC model construction.