Assessing Nile Delta Aquifer Vulnerability by Using Drastic Index and Fuzzy Logic Methods: Comparative Study

This study implements several vulnerability mapping scenarios for both the clay cap and the quaternary aquifer in the Nile Delta. The original generic DRASTIC model, the modified DRASTIC model, and the specific DRASTIC model have all been implemented. Additionally, the Fuzzy Logic method is employed to examine its capability to accurately capture the outcomes derived from DRASTIC models. The vulnerability map for each model is generated using ArcMap 10.5 software. The results for both the clay cap and the quaternary aquifer reveal similarities and differences among the approaches. The generic DRASTIC model is applied to the clay cap layer, with the vulnerability classes classified as follows: low (0.44%), moderate (59.53%), high (39.80%), and very high (0.23%). When considering the modified DRASTIC model and the specific DRASTIC, the vulnerability map shows that more than 85% of the study area is extremely vulnerable to pollution as a result of including the land use and the population parameters in the vulnerability index equation. A mismatch is observed between the results of the DRASTIC-based methods and the Fuzzy Logic model attributed to fundamental differences in how each approach handles input data and uncertainty. Furthermore, a sensitivity analysis is conducted to evaluate the performance of each method and to identify the critical vulnerability assessment of hydrological parameters. Specifically, for the clay cap, the vadose zone stands out as the most vital parameter in all models. In the case of the quaternary aquifer, hydraulic conductivity emerges as the most important parameter across all models.