There is a projection of an increase in runoff until the 2050s mainly due to an increase in precipitation in the upper Ganges, Brahmaputra, Salween and Mekong basins, where it could be due to accelerated melting in the upper Indus basin. The runoff could increase in the range of 3-27%  by mid-century compared with the reference period  for Himalayan river basins depending on the different RCP scenarios . Likewise, Khanal et al.  suggest contrasting responses to climate change for HMA rivers in which, on the seasonal scale, the earlier onset of melting causes a shift in magnitude and peak of water availability, whereas on the annual scale, total water availability increases for the headwaters. The future flow would increase in Nepal's Central Himalaya region . These changes in water availability in space and time will have serious consequences in downstream water availability for various sectoral uses and ecosystem functioning in Asia ; however, future water availability is largely uncertain due to significant variation in climate-change projections among different global climate models .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report