Abstract

BA, Khalidou M. et al. Hydrological modeling of large watersheds: case study of the Senegal River, West Africa. Tecnol. cienc. agua [online]. 2013, vol.4, n.2, pp.129-136. ISSN 2007-2422.

The present paper is focusing on improving the rainfall-runoff modeling in a large basin, at a daily scale, using the distributed hydrological model CEQUEAU and the GIS IDRISI. A hydrogeomatic module was implemented using a supervised process to provide the input data required by the hydrological model. SRTM (Shuttle Radar Topography Mission, USGS) images were used, with a spatial resolution of 30" (≈ 1 km), for the purpose of defining watershed divides, which eliminates significant sources of uncertainty and reduces processing times. On the other hand, the discharge of the Senegal River has been gauged at the Bakel hydrometric station since the beginning of the 20th century until today, so a relatively long time series of data is now available. Various hydrologic studies about this basin have been performed, reporting a watershed area of roughly 289 × 103 km2, which is greatly underestimated according to the present study. The basin contains very diverse climatic conditions, with high variability in total annual precipitation, from 2 000 mm in the south to 50 mm in the north. Physiographic parameters have been computed taking into account the extensive area of the basin located in Mauritania, which had been neglected as part of this watershed by previous studies. Since the simulations of daily volumes for the period 1970-2000 produced good results (Nash coefficients generally above 0.80), it is concluded that simulations are more suitable when using the new hydrogeomatic module and the CEQUEAU and represent a solid basis for water resources management in the area.

Keywords : hydro-geomatic module; large watersheds; Senegal River; distributed model; GIS-IDRISI; CEQUEAU.

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