OLANREWAJU LAWAL, THOMAS GAISER, KARL STAHR
University of Hohenheim, Institute of Soil Science and Land Evaluation, Germany
Agriculture is often the most important economic sector in many developing countries. In Benin 80% of the active population is engaged in agricultural activities and agriculture contributes up to 37% of the GDP . Several African countries have chosen the option to increase agricultural production via an expansion of the cultivated surface area. According to the FAO (2004) the Agricultural area in Benin has increased from 1,442,000ha in 1961 to 2,815,000ha in 2001, which means an increase of 51%.
Due to its history as central territory of a formerly important kingdom, the Abomey plateau is heavily influenced by this process and currently has a population density of 225 inhabitants per km2 by the census in 1992. Nowadays, the plateau is characterised by soil degradation, scarcity of forest cover and low agricultural yields. The challenge is to bring to a halt the negative trend in agricultural productivity due to soil loss and soil degradation, and to reverse the deterioration of the productive base (soil).
In order to assess the sediment load on a regional scale which may arise from tremendous anthropogenic activities, a geographic information system on the relevant surface properties will be generated for regional modelling. This research applies the Soil and Water Assessment Tool (SWAT) model to the Zagbo River catchment area in Southern Benin to quantify the sediment load based on the changes in land use over the years. The DEM of the southern part of Benin, soil maps from the SOTER database and land use/land cover maps, digitised stream lines (Zagbo River) and weather data was used in this model to generate maps of sediment load potential for different land use scenarios and thus help in identifying the major sources of sediment movement.
Keywords: GIS, modelling, sediment yield, SOTER, SWAT, watershed hydrology