The Grimsel test site: geological background of the area and special aspects of water flow

This article gives a brief outline of the geological background of the Grimsel area. Since the investigation programme at the GTS is aimed at developing methods and instrumentation and does not involve an actual site assessment, the geology is investigated only in so far as this contributes to achieving these objectives and understanding the experiments. Special aspects of water flow in the area are described in more details as most of the experiments are affected directly or indirectly by water movements in the rock. (author) 10 figs