DISTRIBUTION OF MEAN SPATIAL RAINFALL IN THE CHARI-LOGONE BASIN FROM 1960-2015

The Chari-Logone basin (BCL), which is the focus of this work, is the hydrologically active part of the Lake Chad Basin. It covers an area of 613 000 km², and its banks are surrounded by a series of mountain ranges: Guera, Ouaddaï, Central African Massif and Adamaoua. The climate of the Chari-Logone basin is contrasted, from the tropical climate to the Sahelian climate. We synthesized, analyzed and exploited all rainfall data available on the Chari-Logone basin during the period 1950-2015 in order to characterize spatial contrasts, temporal variations and sensitivities to climatic variations. These data come from Chad's national services and literature. We used the method of Kriging interpolation with the software R for the spatialization of these data. The interpolation is made on eighty-nine rainfall stations, and the mesh chosen is a regular grid with a pitch of 0.1°. Data analysis showed that the distribution of interannual mean rainfall is mainly along a typical south - north gradient of the Sudano - Sahelian region. The highest values are always recorded at the southwestern extremities corresponding to the direction of entry of the monsoon flow in the basin, with probably a slight orographic effect. Thus, Sudan's wetter regions of the southwest (1600 to 800 mm) are progressively transferred to the Sahelian regions, which are sparsely watered in the north-east (between 800 and 200 mm).