Variabilité spatio-temporelle des pluies de 1932 à 2014 dans le bassin versant du fleuve Kayanga/Gêba (République de Guinée, Sénégal, Guinée-Bissau)

Abstract

This article studies the spatial and temporal rainfall variability of the transboundary catchment area of Kayanga/Gêba River between the Republic of Guinea, Senegal and Guinea-Bissau. The homogenization and the filling of the gaps were ensured by the method of the regional vector. The application on annual rainfall (1932-2014) of the statistical tests of PETTITT and BUISHAND indicates ruptures of stationarity in 1964 (one case) or 1967 (five cases). The deficits after rupture are between 13.7 % and 19.6 % of the rains before rupture. The method of segmentation shows, for some stations, an improvement of the rainfall from 1992 or 2002. The spatial distribution of average annual rainfall over rolling 30-year periods shows both their northward decrease and the southward migration of isohyets after rupture. The 1961-1990 period is the driest. The rainfall indices of LAMB, studied at the decennial scale, confirm this evolution and show an improvement of the situation from the decade 1988-1997.