Rainfall Variability in Sine Saloum River Basin in a Context of Climate Change and Variability

Abstract

Drought is one of the most worrying manifestations of variability and change of climate in many West African countries. Due to its threats on human life, socio-economic activities, agricultural productivities, shortage of water, natural resources and environments, the problems related to drought have caught the attention of scientists, researchers and policy makers in recent decades. The aim of this paper is to characterize and analyze climatic events and their impact on water resources, environmental ecosystems and population. For this, we have selected rainfall time series of Sine Saloum river basin at Foundioune’s rain gauge. We have first conducted an exploratory analysis based on the graphic study. So, histograms relating to annual rainfall, monthly rainfall decadal, interannual monthly rainfall and interannual monthly averages, were analyzed separately compared to the corresponding average; this has highlighted the spatial and temporal distribution of intra and inter annual rainfall compared to the average and allowing viewing wet and dry years and months. We have secondly calculated the drought indices such as standardized precipitation index and normal precipitation index to evaluate climate fluctuations, characterize the progression of drought and its degree of intensity. This has also highlighted the deficit years and surplus years. In total, over the 43 years of the study period, we have counted 13 wet years and 20 dry years. We have also noted that 1971 was the wettest year and 2007 the least wet year. Characterization of these 30 deficit years has highlighted 3 categories of drought: mild drought, moderate drought and great drought. It appears from this study that the impacts of drought can be attributed in part to a deficit or erratic rainfall. Analysis of the results has showed the high vulnerability of the watershed to drought. Examination of drought years revealed a higher frequency in space and in the time of light drought. These results are very useful for drought monitoring, evaluation and mitigation.