IWRA Proceedings

AbstractLong years of observing hydrological networks by Orstom lead hydrologists to editing monographies of major West and Central African rivers (Congo, Niger, Senegal…). Data processing permitted to manage a high quality data base of all the data collected. More recently, new computer tools permitted us to build a geographical data base and finally an Environmental Information System gathering chronological and spatial data within SIEREM. What we show on this poster is the constitution of the Geographical part of this EIS. The first aim was to model the hydrological basins of Western and Central Africa so the processed stations had to fill two conditions: the first one was a long enough observation period (20 years at least) and the second one was to drain a large enough basin (at least 2500 km²). The process was first an automatic one, using ArcInfo tools, GTOPO30 digital elevation model, and Digital Chart of the World drainage network. But, the topography is so that the flat areas are numerous and the automatic process is unable to delineate the basins in those areas. We had so to refer to the monographies and reports edited by IRD. The result is a geographical data base spread over more than 6 million square kilometres of West and Central Africa. Other basins have been delineated and added, located in South and East Africa. This poster shows the operating processes used to carry out this work. The GIS products can be browsed on the web site (http://www.hydrosciences.fr/sierem) and the “product” part of this site offers the visitor to download freely the geographical “layers”. Let’s add that this work is available and shared with researchers participating to international programs and cooperation such as FRIEND projects.