Physico-chemical and hydrochemical measurements have been made at an experimental site equipped with seven boreholes (26 to 100 m deep) in fractured granites and seven piezometers (1 to 3 m) in colluvial and weathered material. It has been found possible to differentiate between those two types of formation from a hydrochemical point of view and to deduce from this their degree of connectivity and their flow regimes.