f Examination of surface-NMR within an integrated geophysical survey in Nauen, Berlin

A combined geophysical survey has been conducted at the test site Nauen near Berlin, prospecting a shallow aquifer in fluvial sediments bordered by glacial till. Some of the geophysical results have been reported earlier [1]. Comprehensive investigations of geoelectric sections and depth-soundings as well as georadar profiles were interpreted to describe subsurface conditions. The structure of the dipping glacial till is well recognisable up to a depth of 13 m. The sandy sediments above represent the aquifer with the water table at a depth of about 2 m. The radar velocities and resistivities from Block-Inversion of geoelectric sections have been used to derive hydrological parameters. The aquifer is accordingly determined to have a porosity around 24 % and a water content of 5 % in the vadose zone. At the main profile, five SNMR soundings have been carried out in order to compare the results with those from conventional geophysical methods. Inversion results show mobile water contents of less than 20 % in the first few meters of the vadose zone, increasing rapidly to 30 %. This means an aquifer with an effective porosity of at least 30 % plus adhesive water content. Decreasing water contents below 15-18 m relate to the glacial till which has low permeability and less mobile water. Increasing water contents in larger depth again to values above 30 % indicates another aquifer which is not verified with other methods yet. The decay times within the aquifer are generally about 150-250 ms and correspond in average to medium sands [2]. However, in detail they are somewhat ambiguous.