Groundwater Vulnerability Assessment Through a Modified DRASTI-LU Framework: Case Study of Saiss Basin in Morocco

摘要

The groundwater vulnerability assessment is an effective tool for protecting groundwater from pollution. The objective of this study is to determine the groundwater vulnerability of the Plio-Quaternary aquifer to pollution in the Saiss basin of Morocco using the DRASTI-LU framework. As validation of groundwater vulnerability map using the Pearson correlation between nitrate (NO3-) concentrations observed at 51 wells and corresponding vulnerability indices calculated showed a poor correlation coefficient (r = 0.35, p < 0.01), the rates and weights of each DRASTI-LU framework parameter were modified using the Wilcoxon rank-sum test and single sensitivity analysis. Afterwards the vulnerability indices were calculated using the modified rates [DRASTI-LU(R)], the modified weights [DRASTI-LU(W)], and both modified rates and weights [DRASTI-LU(RW)]. According to the results, the modification of the rates provided significantly improved vulnerability map as compared to DRASTI-LU(W) and DRASTI-LU(RW). Based on DRASTI-LU(R), four vulnerability classes were identified, namely very low, low, medium, and high, with a dominance of the medium vulnerability class. Furthermore, the sensitivity analysis applied to the DRASTI-LU(R) revealed that land use was the most effective parameter, while topography and soil media were the least effective parameters in the groundwater vulnerability assessment. The current research can support the environment-related groundwater management and planning in the study region.