Variation of turbidity during subsurface abstraction of river water: A case study

Rivers are known to carry sediment loads. Many rivers in Asia including Kosi, Brahmaputra, Bagmati rivers in India and Yellow and Yarlung Tsangpo rivers in China are well known for their carriage of excessive sediment loads. In India, many water abstraction units are located along river banks. Their success depends on how the sediment load is trapped as the sediment laden water flows towards the pumping wells located few hundred meters away from river bank. In this work, based on the analysis of a data of one year on suspended load variations in a canal, located at Haridwar, India, trap efficiency variations are studied during the passage of source water to the abstraction well. Considering the subsurface basin, located within the source water and the abstraction well, as a hypothetical settling basin, variation of trap efficiency is related with the influent concentration. It is observed that the trap efficiency depends on the influent concentration. Appropriate functional forms for the variation of trap efficiency with the influent concentrations are also identified.