How can Africäs finite water and land resources be managed sustainably under the influence of Global Change so as to meet the growing needs of humans in ways that avert the looming crisis? The need to find answers to this question has taxed the brains of many scientists who recognize the urgency of these problems. The pressing water problems must clearly be tackled from an integrated perspective, taking into account environmental, human and technological factors and in particular their inter-dependence. This is the approach adopted by the German GLOWA-IMPETUS project and presented in this book. It is based on the wealth of research results gained in two representative African watersheds: the Ouémé catchment in Benin and the Drâa catchment in Morocco. Interdisciplinary, application-oriented tasks were accomplished with the help of a unique mix of scientists from the social sciences, natural sciences, agricultural science and medicine. The book is organized as follows: Part I deals with the fundamentals and process understanding regarding all major aspects of the hydrological cycle. Part I forms the basis of Part II of the book, which focuses on future climate and socio-economic projections and on the decision support for the sustainable management of natural resources.