Most reservoirs become ineffective due to sedimentation, says study

NEW DELHI: Most of the dams in the country are facing severe siltation, which reduces their effectiveness in flood control and water storage, a new study by the Indian Institute of Science Education and Research (IISER) has said, highlighting that Himalayan and Indo-Gangetic plain rivers are classified as highly vulnerable and require immediate attention. The study analysed data from the Central Water Commissions recent report, Compendium on Sedimentation of Reservoirs in India, and found that a majority of the dams have lost over 50% of their total reservoir capacity. By 2050, 10 reservoirs in east-flowing rivers and 7 in west-flowing rivers are projected to surpass 50% storage capacity loss, posing a severe threat to water security, said the study, Sedimentation-induced vulnerabilities of large reservoirs in India, published in the journal Stochastic Environmental Research and Risk Assessment. Researchers Uma Madhuri Mogili and Somil Swarnkar from the IISER, Bhopal looked at nearly 370 large reservoirs capacity of over 100 million cubic metresin seven regions, including the Himalayan and Indo-Gangetic plains. Most of the analysed reservoirs were found to have become operational between 1939 and 1991. East-flowing rivers beyond Godavari, having nearly 160reservoirs, are a critical zone in meeting south Indias agricultural and industrial water needs, the researchers added. However, west-flowing rivers up to the Narmada were noted to have fewer, but larger reservoirs. According to the research, several reservoirs in the Himalayan and Indo-Gangetic plains rivers are classified as high or very high vulnerability, requiring immediate attention and management interventions. The limited number of reservoirs on rivers in the Himalayan region and Indo-Gangetic plains highlight terrain-related challenges in mountains in the former and a heavy reliance on natural river flows in the latter, the study said.