Assessment of groundwater vulnerability to pollution using the DRASTIC method in the Rich alluvial aquifer (Central High Atlas of Morocco)
Rapid urbanization and corresponding wastewater discharges and the increasing use of chemical fertilizers in agriculture are a potential risk for groundwater pollution. Mapping the vulnerability of groundwater to pollution minimizes this risk by identifying the most sensitive areas to help a good qualitative management of the resource. Here, the vulnerability was assessed using the DRASTIC method, in comparison with PRK method (where P is the topographic slope, R the ratio of the piezometric level fluctuations to the thickness of the unsaturated zone, and K the aquifer permeability) for the Rich alluvial aquifer (Central High Atlas of Morocco). The vulnerability map obtained was tested and validated with the electrical conductivity of 44 wells using the Kappa test and the coincidence rate. The result obtained showed a low K (0.006) and a low coincidence rate of 24%, which validated partly the obtained vulnerability map. The vulnerability classes obtained showed that 21.7% of the study area had low to very low vulnerability, 56.6% moderate vulnerability, and 21.7% high to very high vulnerability. The complexity in producing this vulnerability map comes from the choice of the parameter to reflect the state of the pollution, and also in the density of the input data and how it is introduced, often by interpolation, assigning values in sectors where no data is known or exists. Finally, an update of this vulnerability map becomes necessary by choosing a different pollution indicator or by using a greater amount of data in the model in order to have a more reliable result to be used to raise awareness of the public services concerned by groundwater in the area.