Melt Runoff Characteristics and Hydro-Meteorological Assessment of East Rathong Glacier in Sikkim Himalaya, India

Hydro-meteorological records of glacier meltwater are very limited in the Indian Himalayan region, especially in the Sikkim Himalaya. Hydrological data coupled with meteorological parameters (temperature, rainfall and humidity) of a catchment facilitate in understanding the dynamics of glacier’s meltwater generation at a local scale. Sikkim Himalaya, an integral part of eastern Himalaya lacks the hydro-meteorological assessment of glacier’s meltwater stream. Therefore, hydro-meteorological analysis of East Rathong Glacier was conducted for three consecutive ablation seasons (June–September) from 2013 to 2015. The data record a maximum runoff during the peak ablation month of July and August (~ 69%), reflecting the seasonal evolution of hydrologic conduits and the expansion of subglacial channels, and the rest runoff observed during June (~ 10%) and September (~ 21%). During the study period, the maximum (Qmax) and minimum runoff (Qmin) of 15.71 and 1.46 m3s−1, respectively were recorded at 17:30 and 9:30 h. The maximum monthly variability in meltwater discharge was recorded in June (Cv = 0.29) and September (Cv = 0.37), which reflects the role of the large extent of seasonal snowfall during early ablation and the seasonal evolution of sub-glacial internal drainage networks in the glacier, respectively. We found that the variability in mean (Tmean) and maximum temperatures (Tmax) has been increased over the subsequent months during the progress of the ablation season with the highest variability in minimum temperature (Tmin) during the end of the ablation season. The correlation matrix analysis shows significant hydro-meteorological relationships of glacier’s meltwater discharge (Q) with the minimum temperature (R2 = 0.43), maximum temperature (R2 = 0.93), mean temperature (R2 = 0.93), Rainfall (R2 = 0.99) and Relative humidity (R2 = 0.77), suggesting the substantial meteorological influences in producing meltwater discharge at monthly scale. The present in-situ observation on hydro-meteorological characteristics of East Rathong Glacier can be used effectively for the hydrological modelling of freshwater resources (Glaciers) which further contribute to the freshwater management under a changing climate.