Comparative study of the hydrological response of Lualaba and Sangha sub-catchments of the Congo basin to climate change

This study highlights the spatial variability of the hydrological response of Congo Basin by comparing two sub-basins Sangha and Lualaba, chosen for their opposed characteristics. The basin was considered as far from climate change threats; the existing predictions on its hydrology were based on the emission scenarios not adapted to the socioeconomic development conditions in the basin, and on a lumped response of hydrological processes at the large scale. The main objective was to assess the hydrological response of the selected sub-basins to climate change. There downscaled GCMs were selected: FGOALS-s2, MIROCS, and MRI-CGCM3; and tested for performance using skill test approach and also bias corrected. GW-PITMAN model was used to assess the impacts of climate change on the hydrology of the two sub-basins. The model was calibrated with the Nsh efficiency and Pbias of 68% and -3.26% for Lualaba; and 76% and 4.06% for Sangha; and validated with the Nash and Pbias of 79% and -2.13% for Lualaba; and 61% and 3.17% for Sangha. Seven hydrological processes: flow, rainfall, interception, potential evapotranspiration, actual-evapotranspiration; soil moisture storage and recharge formed the basis of the focus for this study. The results showed that, the potential evapotranspiration decreases negligibly for all GCMs in all sub-basins. Where as all other variables show, major, medium and slight increase in Lualaba for all GCMs and RCPs while in Sangha, there is major, mean and slight decrease of all variables, two GCMs and RCPs except FGOAL-s2 where variables increased except flow in RCP 4.5. from the above results, Sangha is more affected than Lualaba by climate change; and the two sub-basins exhibit different hydrological responses.