Impact of climate change on the water balance of the Sankarani river basin in West Africa

Abstract

The Sankarani River is a tributary and powerful regulator of the hydrological regime of the Niger River. It plays a big role in the socio-economic development of Mali through the supply of electricity through the hydroelectric power station of Sélingué, its contribution in rice cultivation and fish farming. However, the inflow of water from this river over the past few decades has been very low, due to climate change and the degradation of its watershed. So this study set itself the objective of analyzing the evolution over different periods of the components of Sankarani's water balance. The data used for this are Landsat / OLI and SRTM satellite images, rainfall and temperatures from the NOAA database, and measured stream flows from 1980 to 2013. All these data have been aggregated at the watershed scale before being used to estimate the components of the water balance over two different periods, according to hydrometeorological standards. The Pettitt Test was used on the annual rainfall series to detect 1994 as the year of failure. Thus, the study revealed a strong degradation of the Sankarani watershed following its continuous anthropization, having led to a very remarkable decrease in the runoff coefficient because, in fact, the decrease in rainfall of 8.7% on the period 1995-2009 compared to 1980-1994 resulted in a decrease of 32.6% of the flow rate, of 26.2% of the variation of water reserve and only of 3.9% of evaporation. On the other hand, in terms of the volume of water compared to the average quantity of rain for each period, evaporation was more intensified by 4.3%, unlike the flow and the variation in reserve which, for their part, decreased by 3.5% and 0.9% respectively. The rainfall deficit in the Sankarani watershed was more negative for runoff.