Comparison of hydrological regime of glacierized Marshyangdi and Tamor river basins of Nepal

Abstract

To study hydrological regime over Marshyangdi (area: 3006.77 km²) and Tamor River basins (area: 4005.22 km2), an integrated approach was performed in particular to emphasize glacio-hydrological model development. Glacio-hydrological degree-day model (GDM) version 1.0, a physical-based gridded glacio-hydrological model, developed on C-Sharp (C#) and Python-programming language is developed. GDM is calibrated for the period 2004–2007 for Marshyangdi River basin (MRB) and from 2001 to 2005 for Tamor River basin (TRB) with Nash–Sutcliffe Efficiency (NSE) of 0.81 and 0.64, respectively. Furthermore, the model is validated for the period 2008–2009 for MRB and from 2006 to 2010 for TRB with NSE of 0.84 and 0.68, respectively. The snow and ice melt contribution to total discharge in MRB during calibration period is found to be 12.3% and 11.2%, respectively, whereas, during validation period, it is 9.9% and 11.8%, respectively. In case of TRB, contribution during calibration period is found to be 14.5% and 7.3%, respectively, and during validation period 12.9% and 10.6%, respectively. The highest rate of increment in minimum temperature trend over TRB and MRB is 0.027 °C/year and 0.008 °C/year. In case of maximum temperature trend, both basins show an increment rate of 0.018 °C/year. The morphometric analysis shows low drainage densities and length of overland flows of 3.66 km and 3.73 km over MRB and TRB, respectively. In Representative Concentration Pathways (RCPs) 4.5 scenario for the period 2021–2050, an average decrease in simulated discharge as − 0.087 m³/year and − 0.366 m³/year for MRB and TRB, respectively, is seen.