In the second case (no or unsaturated SFL), techniques forwell siting such as lineament analysis, geophysics and radonsurveys (Lachassagne et al. 2001b; Reddy et al. 2006), can beused. As weathering is also the main driver of aquifer developmentin this context, linking open discontinuities to past orrecent tectonic events and to recent or paleo stress-field data isnot of interest, as indirectly shown by Holland and Witthüser(2011). This is because weathering develops along all heterogeneitieswhatever their orientation. Moreover, in most cases,regional plate-scale stresses do not influence fractures in thefirst hundreds ofmetres below the surface; topographic factorspredominate (see references cited by Lachassagne et al. 2011).