Hydroclimatologie et dynamique de l’occupation du sol du bassin versant du Haut Bandama à Tortiya (Nord de la Côte d’Ivoire)

Abstract

This present study performed in the upper Bandama catchment at Tortiya station in Northern Côte d’Ivoire aims to improve our knowledge on hydroclimatic and land cover in order to lead to a better water resources management. It is based on the exploitation of rainfall and runoff data and satellite images. Thus application of statistic tests (Pettitt, Lee, Heghinian) highlights changes in rainfall regime during the 1970s. This modification reveals a decrease of 12 % and 22 % in rainfall depending on the stations (16.5 % in average) causing a stronger decrease in runoff (62.5 %) at Tortiya station. Depletion coefficients become very high (more than 8 10-2 j-1) after the 1970s. Groundwater recharge decreases with an average effective infiltration of 212 mm in decade 1980-1989 and 184 mm in the decade 1990-1999. In the same time, diachronic study of land cover of satellite images from November 1986 (TM sensor) and January 2000 (ETM+ sensor) on test area of watershed allowed to obtain a trend of land cover. The main observed changes are the increase of habitats (+3.1 %), bare soil (+6.64 %) and crops areas (+21.60 %) and inversely a reduction of the area covered by savannah (-29 %) and forests (-1.38 %). These modifications led to changes on hydrological behaviour of catchment.

Keywords

• water resources
• Africa
• land cover
• hydroclimatology
• catchment area
• Landsat