AR5  concluded that increases in the mean annual runoff are projected in high latitudes and the wet tropics and decreases in dry tropical regions, but with very considerable uncertainty. Both the patterns of change and uncertainties were found to be primarily driven by projected changes in precipitation. SR1.5  concluded with medium confidence that areas with either positive or negative changes in mean annual runoff/streamflow are projected to be smaller for 1.5°C than for 2ºC of global warming. AR6 WGI  conclude with medium confidence that global runoff will increase with global warming but with significant regional and seasonal variations. WGI further concluded with high confidence that runoff will increase in the high northern latitudes and decrease in the Mediterranean and southern Africa. However, there was medium confidence that runoff will increase in central and eastern African regions and decrease in Central America and parts of southern South America. The magnitude of the change is projected to increase with emissions. There is medium confidence that the seasonality of runoff and streamflow will increase with global warming in the subtropics. In snow-dominated regions, there is high confidence that peak flows associated with spring snowmelt will occur earlier in the year and medium confidence that snowmelt-induced runoff will decrease with reduced snow, except in glacier-fed basins where runoff may increase in the near term.
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report