Climate change and impacts on the hydrology of the Congo Basin: The case of the northern sub-basins of the Oubangui and Sangha Rivers

Abstract

This study assesses the hydrological response of the Congo Basin’s runoff to future changes of climatic conditions. The study is carried out at the sub-basin scale in the northern part of the Congo Basin for which downscaled GCM data have been obtained. In order to assess the impacts of climate change scenarios on water resources availability of the Congo Basin, three downscaled and bias corrected GCMs were used to drive a semi-distributed rainfall-runoff model which was initially established for the whole Congo Basin through manual calibration and physically-based a priori parameter estimation approaches. The analysis focuses on the variables of the hydrological processes such as rainfall, interception, potential evapotranspiration, soil moisture store, surface runoff, soil moisture runoff, and recharge. In general terms, the study shows that there is a decrease in runoff for the near-future projections in the northern part of the Congo Basin which has a tropical transition regime. For the three GCMs used in this study, there is very little change in rainfall from the historical conditions. The major change is observed in evapotranspiration, due to an increase in air temperature. There is a clear indication of the translation of climate signal into flows. There is more than 10% decrease in total runoff, which is a consequence of relatively little increase in rainfall and a consistent increase in potential evapotranspiration.