In 1980, Nagra, the Swiss National Cooperative for the Storage of Radioactive Waste, began a comprehensive field investigation programme to assess the feasibility and safety of a repository for the final disposal of high-level radioactive waste in northern Switzerland. An international team of scientists has carried out a comprehensive study on the isotope hydrogeology of deep groundwaters. One of the major implications of this work pertains to the storage of radioactive waste. The study goes far beyond an in-depth regional study as it draws together the results of diverse techniques, many of which have been re-evaluated or further developed.This book presents in great detail the results of one of the most comprehensive isotope hydrology studies ever undertaken.