Impact of Climate Change on River Flows in the Black Volta River (International Journal)

This paper assess the impact of climate change inthe Black Volta River by using output from the AtmosphericGeneral Circulation Model 20 km resolution(hereinafter AGCM20) by the Japanese MeteorologicalAgency/Meteorological Research Institute.TheBlack Volta River is a major tributary of the VoltaRiver. It flows mainly in Burkina Faso and Ghanain West Africa. The basin covers 142,056 km2 andbelongs to the semi-arid tropical climate. Before applyingAGCM20 output to a rainfall-runoff model, theperformance of the AGCM20 rainfall is investigatedby comparing with the observed rainfall in the BlackVolta basin. Then, in order to assess the possible impactof rainfall change on river flows, the kinematicwave model with considering the saturated and unsaturatedsub-surface soil zones was performed. Therainfall analysis shows that, the correlation coefficientof the monthly rainfall between the observed rainfalland AGCM20 for the present climate (1979-2004) is0.977. The analysis also shows that AGCM20 overestimatesprecipitation during the rainy season and underestimatesthe dry season for the present climate.The analysis of the AGCM20 output show the precipitationpattern change in the future (2075-2099). Precipitationis expected to increase by 3 persen, while evaporationby 5 persen and transpiration by 8 persen in the future.Also, daily maximum rainfall is expected to be20 mm (60 persen) higher. Thus, the future climate in thisregion is expected to be severer. The rainfall-runoffsimulation is successfully calibrated at the Bamboi dischargegauging station in the Black Volta from June2000 to December 2000 with 0.72 of the Nash-Sutcliffmodel coefficiency index. The model is applied withAGCM20 ouputs for the present climate (1979-2004)and the future climate (2075-2099). The results indicatethat the future discharge will decrease from Januaryto July at the rate of the maximum of 50 persen andincrease from August to December at the rate of themaximum of 20 persen in the future. Therefore, the comprehensiveplanning for both floods and droughts areurgent in this region. Journal of Disaster Research Vol.9 No.4, 2014