Glacial Ice-melt Contribution to Streamflow in the Marshyangdi River Basin: Using Glacio-Hydrological Degree-Day Model

Abstract

Abstract

This study uses the Glacio-Hydrological Degree Day Model (GDM) to quantify the contribution of glacier ice-melt to streamflow in order to analyze the dynamics of the Marshyangdi River Basin (MRB) in central Nepal. GDM is useful in calculating the contribution of rainfall, ice-melt, snow-melt and base-flow of a river. Glacier melt modeling is essential for future water resource planning and disaster risk management because MRB, a glacier-fed basin in the Hindu Kush Himalaya (HKH) region, is extremely vulnerable to climatic changes. Air temperature, precipitation, digital elevation models, and land cover classification are the input data needed to accurately estimate daily discharge in the GDM model, which are calibrated and validated using data from 2004 to 2007 and validated from 2007 to 2010. 2007 is used in both period for ease in comparing four years for both period. Strong agreement is found between the model's performance and the measured discharge data (NSE ≈ 0.78, R2 ≈ 0.8). The findings show that glacial ice-melt contributes 1.5% – 4% of total discharge each year from Bimalnagar Station, snow-melt accounts for 7% - 10% of MRB's total yearly discharge, rain accounts for 52% - 58% and base-flow accounts for 32% - 36.5%. The peak contribution of glacial ice-melt is observed in August, with clean glacier ice-melt contribution and debris covered glacier ice-melt contribution of 6.82 m3/s and 5.77 m3/s respectively in the calibration period. Similarly, in the validation period the clean glacier and debris covered glacier ice-melt contribution are 7.56 m3/s and 6.29 m3/s respectively in August.