Christoph J. Keysers

Dr. rer. nat., Diplom-Physiker

Ch.J. Keysers, H.-J. Kümpel

  Use of Archie's Formation Factor in delineating fresh/saline water mixing - a case study from a saline spring location

 J. Ind. Geophys. Union, 3, 25-38, 1999

A resistivity survey was conducted in the area of natural saline springs in Salzböde Valley, Germany. We describe a study which aimed at delineating fresh/salt water mixing and has made use of Archie's concept of formation factor in the light of modern resistivity inversion technique. The research site was mapped through Constant Separation Traversing (CST) in conventional Wenner configuration for different electrode spacings (a = 1.11 m, 3.33 m, 10 m). Moreover, five pseudesections were recorded in the contaminated area in alpha-, beta-, and gamma-Wenner configurations. Conductivity values of groundwater probes indicate that low ground resistivity reflects high saline content of  the pore fluid. For the interpretation of data, conventional analysis tools as the lateral variation index and the beta/gamma ratio were used but also the algorithm SIRT for inversion of the pseudosections. From the vertical 2D-inversion models we extracted horizontal 2D-slices. Then, with the help of Archie's formation factor and the assumption of parallel conductivity we calculated a spatial distribution of pore fluid resistivity. Conventional and modern techniques proved to be consistent. The local communities in Salzböde Valley are engaged in promoting nature-oriented tourism and plan to reestablish the original ecological habitats around the saline spring. The results of our investigations help to determine the layout of biotopes. The methods presented can also be used to address other environmental problems such as leakage from dumps and waste deposits, and seawater intrusion in coastal regions.