The Atlas on Water Cooperation refers to an empirically based tool thought to analyze the interactions between biophysical and socio-economic factors able to influence cooperation or tensions over water in shared watersheds. The idea was to develop a tool able to monitor availability, uses and abuses of water and water-stressed hot spots at national and regional scales. This is not only directed at analyzing water supply and demand, as for a water stress indicator, but also the socio-economic, institutional, legal, and cultural context evolutions that are likely to influence the hydro-political tensions or cooperation.