Suspended sediment dynamics and associated hydro-meteorological interrelations in east rathong glacier, eastern himalaya, india

Abstract

The records of suspended sediments and associated hydro-meteorology of the glacierized catchments are very limited in Sikkim Himalaya. Therefore, we carried out the first-ever estimate of suspended sediment transport from the meltwater stream of East Rathong Glacier for June-September during three consecutive melt seasons (2013–2015). These records were used to estimate the suspended sediment concentration (SSC), load (SSL), yield (SSY) and erosion rate (ER). The daily mean SSC was 105.75, 84.20, and 91.51 mg/l during melt seasons of 2013–2015 respectively. The monthly mean SSC of the combined melt season of 2013–2015 was 92.72, 107.14, 105.93 and 60.46 mg/l for June-September, respectively. The observation shows that July-August contributed to maximum SSC, accounting 70.45% of total SSC. Similarly, the monthly mean SSL for June-September was 55.64, 69.61, 65.75 and 25.72 tons, respectively. We observed high variability in SSL (CV = 0.54) than SSC (CV = 0.38) since the estimation of SSL depends on both discharge (Q) and SSC. The relationship between monthly mean SSC and Q was highly significant (R2 = 0.98) than daily SSC and Q (R2 = 0.25) due to reduced variability on a monthly scale. Further, mean SSY in the catchment was high during peak melting season (July-August), which substantially reduced during the end of the melting season. We estimated the mean SSY of 281.93 ton/yr km2 during the combined melt season (2013–2015). The average ER for the East Rathong Glacier basin was 1.04 mm/yr, which is lower than the ER of most of the Himalayan glaciers. We observed significant meteorological control of Tmean, Tmax and Rainfall in the transportation of suspended sediments from meltwater stream at a monthly scale. These in-situ based records on dynamics of suspended sediment and associated hydro-meteorological parameters are relevant for the planning and management of freshwater resources and planning for hydropower projects under a changing climate.