MC EXPLAINER Flushing of Salal and Baglihar dams reduces water flow to Pakistan, Kishanganga next

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With the Indus Waters Treaty (IWT), 1960, no longer binding, India, for the first time, has undertaken full flushing exercises of its 690 MW Salal and 900 MW Baglihar hydroelectric projects on the Chenab river – a process which Pakistan used to object to when the IWT was honoured by both countries.

The Chenab starts in the Himalayas near the Baralacha Pass in Himachal Pradesh, where it is also known as Chandrabhaga, and ends by joining the Indus river at Mithankot in Pakistan.

Officials told Moneycontrol that as part of the flushing or desilting process, which takes multiple days, the flow of the Chenab was curtailed over the weekend to collect water to full capacity in the reservoirs at the Salal and Baglihar plants.

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“It is true that water was held up at the two projects over the weekend as part of the desilting process. But now, water is being released to flush out the reservoirs,” said a senior official from NHPC Ltd requesting anonymity.

The flushing exercise, which follows the process of holding water to fill the reservoir, is carried out to clear sediments that not only reduce the capacity of the reservoirs but also affect the performance of hydropower plants. Sediments in reservoirs consist of solid particles, such as sand, silt, and clay, that settle at the bottom over time. This process is known as sedimentation.

Kishanganga to be taken up next

While the Salal and Baglihar dams are somewhat regulating the flow of the Chenab through such desilting activities, the next plant to be taken up for cleaning will be the Kishanganga project, which is on a tributary of the Jhelum. Unlike Salal, Kishanganga is a relatively new project, commissioned in 2018. Hence, the issue of sedimentation is not as grave.

Also Read: Suspending the Indus Water Treaty stops flow of information, gives India a window to accelerate hydropower projects.

The 330 MW Kishanganga project has been the most disputed under the IWT, with Pakistan raising as many as six objections in 2007 relating to water storage, reservoir silt management, design and other such issues. Each of these objections was being adjudicated separately, thereby taking years to be concluded. While two objections were resolved by January 2024, four were still being fought over in the Court of Arbitration set up by the World Bank.

The two projects in Uri (Uri-I and Uri-II) already underwent similar flushing exercises a week ago.

Frequent flushing to become routine now

Officials said such flushing of reservoirs in Jammu & Kashmir and Ladakh will be routine and more frequent now as India has suspended the IWT, which otherwise placed multiple restrictions on India's use of the Western rivers (Chenab, Jhelum and Indus).

Many of the reservoirs in the region have so much sedimentation that the water storage capacities in some of them have reduced by more than 50 percent. Salal which is one of the oldest projects, the last unit of which was commissioned in 1995, has a massively constrained reservoir due to excessive sedimentation. Reports suggest that the Salal reservoir has a design capacity of 284 million cubic metres, but now it can store less than half that volume.

Also Read: Turning Off The Tap: Tearing up the Indus treaty won’t bite Pak anytime soon.

“The frequency of flushing will be increased to improve the operational efficiency of our assets. Water flow regulation to Pakistan would be a default byproduct of it. We hope that power generation will also increase with this,” said the official.