Mapping groundwater’s susceptibility to pollution in the Triffa Plain (Eastern Morocco) using a modified method based on the DRASTIC, RIVA, and AHP models

Groundwater resources in arid and semiarid regions suffering from low precipitation, high temperatures, and high evaporation rates associated with anthropogenic stresses require appropriate and careful management to maintain water quality in the present and future. In this context, assessing the intrinsic vulnerability of the Triffa Plain phreatic aquifer is crucial to preserve the groundwater. In this study, we proceeded to the hydrogeological parameters' mapping and the inherent vulnerability evaluation using the classical DRASTIC method. In addition, we studied the reliability of estimating the recharge parameter by a qualitative approach. The study combines the DRASTIC, RIVA, and AHP techniques to improve and simplify the evaluation of the vulnerability of groundwater in agricultural areas. The AHP method weighed the parameters according to their relevance to the aquifer vulnerability process. The modified method can solve incomplete data problems, especially in agricultural areas where irrigation return flows are the major contributor to groundwater recharge. The DRASTIC and DRASTIC R-modified results delineated four regions, from extremely low to high sensitivity levels in the area. In comparison with the spatial distribution of nitrates and the original DRASTIC method, the DRASTIC R-modified method represents a realistic assessment with 12% (low), 78% (medium), and 10% (high) of the total area. Similarly, concerning the original DRASTIC method, the low vulnerability is 14%, medium 76%, and high 9%. The results were successfully validated with the spatial distribution and bivariate correlation whit nitrate concentrations. These findings highlight the robustness of incorporating a qualitative recharge parameter within the DRASTIC model, considering irrigation impact, rainfall intensity, and quantity. The obtained results provide an indispensable tool for decision-makers and managers to conceive timely protection and monitoring measures for groundwater resources.