As a result of the same weathering processes, the fissuresfrom the fissured layer of single phase or multi-phase profilesexhibit very similar hydraulic conductivities, and showboth a higher density of conductive fissures at the top of thelayer. The preserved ancient fissures within the laminatedlayer of a multiphase profile are partly obliterated by therecent weathering; their hydraulic conductivity is thus significantlyreduced. Nevertheless, they do significantly contributeto the borewell yield.