The focal area of the Sahara and Sahel Observatory (OSS) is located in the Sahara and Sahel zone which contains large sedimentary basins covering each a surface of several hundreds of thousands of km². OSS promotes the concept of "basin awareness" by encouraging the countries sharing transboundary basin to work together in order to manage the groundwater resource in a rational manner. This was experimented in the North Western Sahara Aquifer System (NWSAS), shared by Algeria, Libya and Tunisia, and the Iullemeden Aquifer System (IAS), shared by Mali, Niger and Nigeria. The key element of this management is the consultation based on the development of decision making tools: Database, Geographic Information System (GIS) and Model. In this context, data and information were collected, treated, harmonized and then gathered into a common database, associated with a Geographical Information System (GIS) which supply the groundwater model. Layers of the (GIS) consist of treated and homogenized thematic maps (topographic, hydrogeological, etc.). The development of models enabled the countries to build forecasting simulations for optimal and rational management of the shared resource. The development of all these tools contributed in updating the aquifers knowledge, improved the exchange and strengthened cooperation between countries.