Schematic hydrogeological map of the Buntsandstein aquifer. Isopiezes in m above mean sea level. Boreholes are mentioned in the text. Location of the Permian SE-Luxembourg Graben (SELG) according to Schintgen and Förster (2013) is shown. Diagonally hatched and cross-hatched zones indicate areas of low permeability in the Buntsandstein aquifer known from boreholes as well as from Kremb-Wagner (1996) and Weiler (1991).