Abstract:
This study evaluated the susceptibility to groundwater pollution using a modified DRASTIC model. A novel hybrid multicriteria
decision-making (MCDM) model integrating Interval Rough Numbers (IRN), Decision Making Trial and Evaluation
Laboratory (DEMATEL), and Analytical Network Process (ANP) was used to investigate the interrelationships between
critical hydrogeologic factors (and determine their relative weights) via a novel vulnerability index based on the DRASTIC
model. The flexibility of GIS in handling spatial data was employed to delineate thematic map layers of the hydrogeologic
factors and to improve the DRASTIC model. The hybrid MCDM model results show that net recharge (a key hydrogeologic
factor) had the highest priority with a weight of 0.1986. In contrast, the topography factor had the least priority, with a
weight of 0.0497. A case study validated the hybrid model using Anambra State, Nigeria. The resultant vulnerability map
shows that 12.98% of the study area falls into a very high vulnerability class, 31.90% falls into a high vulnerability, 23.52%
falls into the average vulnerability, 21.75% falls into a low vulnerability, and 9.85% falls into very low vulnerability classes,
respectively. In addition, nitrate concentration was used to evaluate the degree of groundwater pollution. Based on observed
nitrate concentration, the modified DRASTIC model was validated and compared to the traditional DRASTIC model; interestingly,
the spatial model of the modified DRASTIC model performed better. This study is thus critical for environmental
monitoring and implementing appropriate management interventions to protect groundwater resources against indiscriminate
sources of pollution.
