Abstract
Improving our knowledge of the water cycle in the West Africanmonsoon system and the way it is represented in numerical models is one of the major goals of the AMMA programme. The water cycle results from complex interactions between the atmosphere and the continent, with contrasted behaviour depending on the region and the space and time scales at which it is analysed. The properties of the surface, the soil and the sub-soil strongly drive water redistribution over the continent and towards the atmosphere, resulting in complex feed back loops that are still not fully understood. Process studies and water budgets computed from a mixture of observations and simulation products provided advances in the knowledge of thesemechanisms. Some of the processes still remain uncertain, such as the links between evapotranspiration, vegetation and ground water storage. Beyond a better knowledge of the monsoon system, model improvement, better numerical weather predictions and the development of tools for water resources assessment and management are among the main applications of these studies.