Application of Glacio-hydrological degree-day Model to simulate hydrological regime of Tamakoshi River Basin, Nepal

Abstract

The glaciers and snow-covered areas has been highly influential in the hydrology of the glacierized basin. Long-term water management will become more difficult as a result of climate change, which is anticipated to alter water availability. Here we have set up Glacio-hydrological Degree day Model Version 2 (GDM V.2) as a hydrological model to simulate the discharge in Tamakoshi River basin (TRB) and quantified various runoff components. The model is first calibrated and validated for the period of 2004-2009 and 2011-2020, respectively where Nash-Sutcliffe Efficiency (NSE) is 0.77 and 0.80 for calibration and validation periods. The monsoonal rain was anticipated to influence stream flow changes the most (46.86%), followed by base flow (37.57%), snowmelt (12.17%), and ice melt (3.18%) form the year 2004-2009 and rain (46.33%), followed by base flow (38.79%), icemelt (3.27%), and snowmelt (10.77%) from 2011-2020 according to the model. Forecasts indicate a rise in discharge under SSP58.5, notably reaching 3.68 m3/s according to EC-Earth3, in stark contrast to the declines projected under SSP24.5, such as the decrease to 0.09 m3/s under Nor ESM2-MM, between SSP24.5 and SSP58.5, constituent contributions exhibit significant variations, shedding light on potential shifts in resource availability.