Spatial and temporal variation of rainfall from 1970 to 2016 in the lower Ouémé Valley in Benin.

Abstract

West Africa has experienced spatio-temporal variability in rainfall regimes for several decades, characterized by the increase in extreme weather events leading to floods and droughts. Benin is not immune to these hydrological and climatic fluctuations in terms of flood and drought hazards. Precipitation is an important variable in the hydrological cycle and has a strong influence on irrigated and rain-fed agricultural crops, therefore a direct impact managed wetland for agriculture. This study aims to analyze the spatial and temporal variation of precipitation over the period from 1970 to 2016 at 8 rainfall stations in the lower valley of Ouémé River Basin. The method used is based on the analysis of the variability and trends of the annual series of precipitation and temperature through three drought indices: the standardized precipitation index (SPI), the Palmer drought severity index (PDSI) and the hydrological drought index (PHDI). The results obtained with the three methods used show that it is reasonable to believe that the basin has retained unstable and poor rainfall characteristics over several decades. The estimated drought indices show that the lower valley of Ouémé River Basin has experienced in the past a long period of extremely severe and severely dry drought followed also by moderate droughts with relatively wet periods in most of the study area.