Study reveals sediments degrading storage capacity of reservoirs by over 50 pc across India

New Delhi, Sep 12 (PTI) Material deposited by a river in a reservoir due to upstream erosion could be deteriorating storage capacity by more than 50 per cent, an analysis of reservoirs across India has revealed.

Researchers Uma Madhuri Mogili and Somil Swarnkar from the Indian Institute of Science Education and Research Bhopal looked at nearly 370 large reservoirs -- capacity of over 100 million cubic metres -- in seven regions, including the Himalayan and Indo-Gangetic Plains.

The analysis revealed "significant regional disparities in sedimentation impacts", with most of the regions exhibiting a vulnerability due to "steep terrain, high erosion, and monsoonal sediment inflows".

"Multiple reservoirs exhibit storage capacity losses exceeding 50 per cent, severely undermining their ability to mitigate floods and manage droughts," according to the study published in the journal Stochastic Environmental Research and Risk Assessment.

The researchers added that among the regions analysed, reservoirs in the Himalayan region showed the highest loss in yearly storage capacity, further stressing their critical vulnerability.

The team also projected that by 2050, 10 reservoirs on the east-flowing rivers and seven on west-flowing ones might surpass a 50 per cent loss in storage capacity, "posing a severe threat to water security".

Further, most of the reservoirs were found to have become operational between 1939 and 1991 -- in line with India's post-independence infrastructure development phase, the authors said.

East-flowing rivers beyond Godavari, having a high number of reservoirs (160), are a critical zone in meeting south India's agricultural and industrial water needs, they added. However, west-flowing rivers up to the Narmada were noted to have fewer, but larger reservoirs.

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 team said.

The region-wise variations stress a need for diverse water management strategies across India's distinct geographical and hydrological contexts, the authors said. PTI KRS RHL