MODELLING RUNOFF AND IMPACT OF CLIMATE CHANGE IN LARGE HIMALAYAN BASINS

The runoff regime in the basins of the rivers Ganges (917’444 km 2 ) and Brahmaputra (547’346 km 2 ) is modelled from precipitation, remotely sensed snow covered areas and temperatures. The runoff cycle roughly corresponds to a calendar year. In view of the small proportion of snowmelt, it is mainly governed by the distribution of rainfalls resulting in flow peaks in the summer and recession flow in the winter. The accuracy of runoff simulations is acceptable in view of the available data and because the SRM model was for the first time used in basins of this order of magnitude. In addition, for the given climate change scenario (T+1.5˚, summer precipitation increased by 10%), the already high risk of floods in July-September is slightly increased.