GRAIN SIZE DISTRIBUTION OF SUSPENDED Wq SEDIMENTS IN ALAKNANDA RIVER

Abstract

Suspended sediments play a key role in determining water quality. It plays a direct role in determining water clarity, bridge scour and reservoir storage. They also bind contaminants, including nutrients, trace metals, semi-volatile organic compounds, and numerous pesticides and serve as a vehicle of transport.Hence, in order to understand the sediment characteristics of the rivers it becomes essential to study the suspended sediments in detail. Grain size is the most fundamental property of sedimentary particles and influences the amount of particle bound matter associated with the sediments.It also exerts an important control on the trap efficiency of reservoirs. The main focus of the present study is to observe the grain size variations over different locations from upstream to downstream on the river Alaknanda and understand the factors affecting them. For the purpose of this study, river water along 20 locations was collected IM from the river Alaknanda and its tributaries in the post monsoon season. These were filtered to obtain suspended sediments. The grain size analysis for the sediments was performed using laser diffraction technique. In particular this study deals with (i) grain size distributions along the 20 sampling locations (ii) Variation of mean grain size with respect to TSS (Total Suspended Sediments) (iii) Variation of mean grain size with respect to SiO2 content (iv) Variation of mean grain size with respect to elevation (v) Relationship between mean grain size of sediments and river energy. The data is presented with various interpretations