In west Africa, significant spatial variability in river flow is projected in the upper reaches of several rivers, with no clear pattern overall  and large uncertainties in estimations of change in runoff . In some higher altitude regions, like the Niger Inland Delta in west Africa, river flows and water levels are expected to increase  . In the Lower Niger Basin, combined average annual rainfall and erosivity for all the climatic models in all scenarios shows increasing rainfall amounts are projected to result in an increasing average change in rainfall-runoff erosivity of about 14%, 19% and 24% for the 2030s, 2050s and 2070s, with concomitant increase in soil loss of 12%, 19% and 21% . In the Volta River system, increasing wet season river flows  and Volta lake outflow  are anticipated under RCP8.5  . In the Volta River basin, compared to 1976-2005, drought events are projected to increase by 1.2 events per decade at around 2°℃ to 1.6 events per decade at around 2.5℃ global warming, and drought area extent is projected to increase by 24% to 34% . In central Africa, runoff in the Congo river system may increase by up to 50% , especially in the wet season, enhancing flood risks in the entire Congo Basin, particularly in the central and western parts . Average river flows are expected to increase in most parts of central Africa, with expected increases in total potential hydropower production , but see Box 9.5.
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report