Flow guided interpolation – A GIS-based method to represent contaminant concentration distributions in groundwater

This paper introduces a new interpolation method to estimate the spatial distribution of contaminant concentrations in groundwater. The method is intended to identify areas of risks in early investigation stages when groundwater sampling data is typically scarce and available interpolation methods fail to provide reasonable results. As a consequence, the method does not only incorporate available sampling data, but also makes use of information about the groundwater flow field, in order to “guide” the interpolation with e.g. ordinary kriging or inverse distance method. The guidance includes the augmentation of available data by auxiliary point data and the segmentation of the estimated plume area into a series of sectors. The method is evaluated for several settings and different sampling data sets. Each data set reflects a specific level of field investigations at the model site, an abandoned military base in Potsdam near Berlin, Germany. The results reveal that flow guidance improves the representation of contaminant distribution for all cases examined in this study compared to “unguided” interpolation. These findings are underpinned by the results of the method’s application to real sampling data. The method especially shows its strength when data of only a few sampling points are available.