TENDANCE DEVOLUTION ET MODE D OCCURRENCE DES PLUIES EXTREMES DANS LE DOMAINE CLIMATIQUE SUD-SOUDANIEN A L OUEST DU BURKINA FASO

Knowledge of the evolution and temporal distribution of extreme rainfall events in the southern Sudanian region to the west of Burkina Faso is of vital importance. This will help in decision-making to prevent the effects of the risks associated with these phenomena. The aim of this study is to characterise, through statistical and graphical analysis, the trends in the occurrence of extreme rainfall events that are likely to compromise the development of people's activities. The results show that some aspects of these rainfall extremes are declining while others are increasing. The frequency indices for these types of rainfall all show a non-significant upward trend, and are homogeneous over the study period (1980-2019) at the used stations. As for rainfall intensity, it shows both a downward and an upward trend, depending on the station and the index used. Very heavy daily rainfall of the order of 38.80 mm or more at Bobo, and 40 mm or more at Gaoua, can occur every year. Between 1980 and 2019, 55% of these rains were recorded between July and August in Gaoua. In Bobo, around 80% of this rain fell between August and September. As for the extremely heavy rains which are greater than 68.80 mm and 65 mm at Bobo and Gaouya station respectively, they have a return period of 2 years. Over the study period, 57% of these types of rain occurred at Gaoua between July and August. At Bobo, 44% of these rains occurred between August and September. Extreme rainfall thus seems to be more frequent in the study area during the months of July, August and September, which are the rainiest months of the year. They arrive later in Bobo compared to Gaoua