Estimation of suspended sediment concentration and meltwater discharge draining from the Chaturangi glacier, Garhwal Himalaya

Abstract

In this study, we present analysis of stream flow near the snout of Chaturangi glacier during the ablation season (June to September (JJAS)) in the year 2015 with an aim to estimate the sediment and water input into the Bhagirathi River from the glacier. In order to assess the variation in meltwater discharge from Chaturangi glacier and to determine its relationship with suspended sediment concentration (SSC), the meltwater and discharge data were analyzed from near the snout to avoid mixing of water and sediment from other glacier tributaries. The meltwater discharge was measured by area velocity method, and the SSC was calculated by vacuum filtration technique. During the entire ablation season (JJAS), marked seasonal variations were observed in the SSC and meltwater discharge. The higher variation is observed in suspended sediment load (SSL) (Cv = 1.17) than SSC (Cv = 0.54) because computation of SSL includes both discharge (Cv = 0.76) and SSC. The average monthly SSC for JJAS was found to be 0.99, 2.29, 4.20, and 1.84 g l−1, respectively, and average monthly meltwater discharge for same period was observed as 5.83, 14.48, 39.81, and 12.69 m3 s−1, respectively. It suggested that throughout the ablation season, the cumulative percentage delivery of SSC follows meltwater discharge. The average suspended sediment yield (SSY) for the entire ablation season was estimated to be 2264.03 ton/km2, and consequent catchment denudation rate was measured as 0.85 mm. A strong positive correlation (r2 = 0.88), found between the discharge and SSC, revealed that both the parameters are dependent on each other. Our results also suggest that the Chaturangi glacier is a major contributor for transportation of sediment into the Bhagirathi River, compared with other tributaries of the Gangotri glacier system.