As pointed out by international organizations and an abundant scientific literature, water is a strategic issue in the Mediterranean region, mainly because of the rarefaction of the resources, in quantity and/or quality, facing the ever increasing demand and the problem of sharing water scarcity. Vulnerability linked with water is paramount in the semi-arid North Africa, where climatic hazards and environmental changes induced by human activities reinforce the likelihood of crises, and where the unequal distribution of resources contributes to increasing the competition between water uses and users. The AMETHYST project aims to analyze the co-evolutions of the water resources under the influence of global change (climate and anthropogenic changes) and of the water uses trajectories. We focus our work on the Maghreb because a large range of evolutions is still possible in this region, far from the extremely severe situations of coastal Spain or Israël on one side, from the reasonably comfortable situations of northern Italy or south-eastern France on the other side. Two case studies will be considered, the Merguellil catchment (near Kairouan, in central Tunisia) and the Tensift region (near Marrakech, Morocco). They are emblematic of water scarcity issues, with rich complementarities in terms of environmental context, water uses, sector competitions, hydraulic history and current water policies. They can also provide large sets of data because of previous long-term research works. We propose an inter-disciplinary project combining physical, social, economic and political sciences, with three research axes: (1) A numerical platform of the integrated functioning of the water resources evolution will be developed, based on models driven by in-situ, reanalysis or scenario data as well as satellite products and anthropogenic constraints arising from the study of the reciprocal impacts of water uses and policy regulations on water resources. (2) Based on a diachronic data analysis and a diagnostic run of this platform, we will analyze the evolution of water resources in the past fifty years in relation to many environmental social, economic, political and technological factors that have interacted. We’ll not only look at trends but also at the way the system reacts after events such as drought or social upheavals. (3) Various scenarios, based on climate and anthropogenic modifications associated with socio-economic projections, will be tested to anticipate effects on water resources trajectories in the next twenty years (extended to fifty years for climate change scenarios), by numerical modeling and by participative approaches. The high ambition of this project is to enhance exchanges between environmental and human sciences at every step of the research, from the acquisition of data to the common definition of prospective scenarios. This shared approach seems the best answer to the urgent water issues in the region, and in particular for providing concrete elements of information to water managers, authorities and stakeholders with whom we will work for the whole duration of the project.