Hydraulic parameters in a porous aquifer: hydrogeological and geophysical logging methods

摘要

Several hydrogeological, hydrochemical and geophysical logging methods have been applied to an alluvial aquifer in the upper Rhone valley (Bois de Finges, Central Wallis, Switzerland). The following methods were used: drilling campaign, pumping test, tracer test, dilution technique and borehole logging. The groundwater chemical composition of the Rhone alluvial aquifer indicates a mixture of weakly mineralized water infiltrating from the Rhone River and SO_4-rich water flowing from the south valley side. Temporal changes in groundwater chemistry and in groundwater levels reflect seasonal variations of the different contributions of groundwater recharge. Borehole geophysical logging allows to determine the variations with depth of total and effective porosity in accordance with the lithological succession, whereas the dilution technique determines filtration velocity and hydraulic conductivity. Vertical groundwater flow was measured with a heat pulse flowmeter. Each hydrogeological, hydrochemical or geophysical method allows to determine one or several hydraulic parameters in a well-defined environment of the studied heterogeneous porous aquifer. This means that often a hydraulic parameter is only valid for the applied method and a given environment. Applying hydrogeological, hydrochemical and geophysical methods simultaneously significantly increases their respective capability to understand linked hydrochemical and hydraulic processes in a porous aquifer.