Spatial Variation in Hydrosedimentary Characteristics of the Alaknanda River Basin in the Indian Himalayas: A Field Study

The Himalayas are the source of several perennial rivers with significant hydropower potential. In the region, many hydropower projects are in operation, and many more are being built. Sediment transport in Himalayan rivers is high. The Alaknanda River basin (ARB) in the Indian Himalayas has a total hydropower potential of 4,081 MW. Only 871 MW of this capacity is being utilized; the remaining 3,210 MW still needs to be tapped. Comprehensive information on hydrosedimentary characteristics is required to design and develop hydropower projects. The present study assessed the spatial variation of the hydrosedimentary characteristics of the ARB. Suspended sediment samples were collected in polyethylene bottles from 19 locations in the ARB. Suspended sediment concentration (SSC), particle size distribution (PSD), shape, and mineral composition were evaluated for all the selected locations. There were minor variations in SSC for the sampling locations. The Pindar tributary was the main influence on SSC in the ARB. Most locations exhibited clay to very fine sand particles. A graphic test method indicated sediment with moderate sorting, coarse skewness, and leptokurtic distributions at most locations. Sorting tended to increase with increasing skewness. Kurtosis showed an increasing trend with skewness; it began decreasing after reaching a maximum value (1.5). No significant spatial variations in particle shape were observed in the ARB. Most of the sampling locations had sediments with high sphericity and slight elongation. No significant spatial variation of mineralogy was observed in the ARB. Numerous minerals were identified in the ARB. Quartz (68.78% to 79.93%) was the most dominant mineral. This dominance was confirmed by an elemental analysis, in which silicon (Si) and oxygen (O) were the most abundant elements (54.73% and 37.92%, respectively). Following a procedure outlined in an international standard, the mean shape and hardness factors for the ARB were estimated at 1.36 and 0.84, respectively. The maximum random uncertainty values for SSC, PSD, sphericity, and aspect ratio were found to be 1.46%, 0.37%, 0.64%, and 0.65%, respectively.