Hydrometeorological assessments and suspended sediment delivery from a central Himalayan glacier in the upper Ganga basin

Abstract

Integrated hydrometeorological investigations are not frequently available at a regional scale over a longer time period, especially near the terminus of Indian Himalayan glaciers. An integrated approach to the collection of hydrological data has major advantages for understanding the runoff generation mechanisms at basin scale, particularly when coupled with meteorological observations. The current study involves time series analysis of hydrometeorological records collected near the terminus of the Chorabari Glacier, for four consecutive ablation seasons (June–Sept.) 2009–2012. The analysis shows that variation in rainfall was higher (cv = 0.9) at the same elevation over proximal sites, while the intensity of extreme rainfall events was 121–160 mm/d. The diurnal temperature range (DTR) has a tendency to reduce over the ablation season because of the onset of the Indian Summer Monsoon (ISM) and then further increases during the ISM withdrawal indicating humid-temperate conditions. The peak discharge (Qpeak) was found to be higher during July and August. Snow and glacier melt contributed 76% of the total suspended sediment transport during peak ISM months (July and August) reflecting seasonal evolution of the hydrologic conduits. The results indicate that Karakoram and western Himalayan glaciers produce comparatively low sediment yield compared to central Himalayan glaciers. The hydrological variations are depicted through flow duration curves (FDC) for meltwater discharge and sediment load. The flow corresponding to Q50, Q75, and Q90 (where Qx is the discharge that is exceeded x percent of the time referred to as % dependability) are 4.2, 3.7, and 2.8 m3/s; and the corresponding dependability for suspended sediment loads (SSLs) are 409.0, 266.0, and 157.2 t/d, respectively. The daily SSL and discharge (Q) from 2009 to 2012 were used to develop a sediment rating curve (SSL = 39.55 × Q1.588, R2 = 0.8). Multiple regressions are used to determine the impacts of meteorological parameters on glacier melt. The meteorological conditions, hydrological characteristics, and suspended sediment delivery for the Chorabari Glacier provide insight on meltwater generation processes and sediment transport patterns during the ISM season.