The hydraulic conductivity of the alloterite is lessthan that of the isalterite as the first is more clayey. Thehydraulic conductivity is much less in fine-grainedrocks’ saprolite such as shales, for instance, than incoarse-grained rocks. In these coarse granites, the baseof the saprolite can be permeable enough to sustain thedischarge of a well, even if it may be difficult to identifyif this permeability originates from the base of the saproliteor the top of the SFL