Hydrogeological mapping of treated waste water infiltration using resistivity surveys / Hydrogeologisk kartläggning av infiltration av renat avloppsvatten genom resistivitetsmätningar
This field study constitutes an evaluation of resistivity surveys as a method of following subsurface water transport. An ABEM Terrameter LS was used to detect chloride enriched infiltrating water. A resistivity profile was established at a field site in Omma outside of Sjöbo, Sweden. The profile followed a slope starting atop a glacifluvial sand deposit going towards a stream in a valley along a hydraulic gradient. A water treatment facility at the top of the glacifluvial deposits large volumes of chloride enriched water that is infiltrated through the soil surface. Resistivity measurements were made repeatedly with the Terrameter during a ten day time period. Inversion was used to create models of the resistivity distribution in a vertical cross section. The data sets were analyzed via time-lapse inversion in order to track change in resistivity due to the infiltration. Supported by existing documentation of the local geology, hydrogeological interpretations of the model results were made. The models indicate that the majority of the infiltration water’s horizontal transport has taken place in the ground water zone. The method was capable of detecting the chloride-rich infiltration water and its progress through the profile stratigraphy during the measurement period. The results indicate that repeated resistivity surveys are a feasible method for tracking subsurface water transport in future projects.