New Delhi
The capacity of the Wazirabad pondage, which is the primary water storage area for the Yamuna in Delhi, will be restored to its original capacity — over twofold the current capacity — through dredging and desilting the riverbed between the Wazirabad barrage and Ram Ghat, the Delhi Jal Board (DJB) said on Tuesday.
This increased storage will act as a buffer, especially during peak summer when water shortage affects the Capital, officials said. The project, which is expected to cost ₹25.79 crore and take around two months, will involve selecting an agency to remove accumulated silt, weeds and shoal.
A senior DJB official said the exercise will entail removing around 363,000 cubic metres of silt. “The pondage area has not been cleared for more than a decade and its capacity has almost halved. Currently, it is only able to hold around 100 million gallons of water per day and once the project is complete, its capacity will be between 200-250 million gallons a day (mgd). We estimate that there is an average of 2.15 metres of siltation in the riverbed,” the official said.
Dredging involves the removal of sediment and debris from the bottom of rivers and other water bodies to increase the water storage capacity. Desilting refers to the removal of silt or fine particles from a body of water to improve flow and prevent flooding. Water from the pondage ahead of the Wazirabad barrage is sent to the three treatment plants at Wazirabad, Chandrawal and Okhla, accounting for a quarter of the city’s daily water requirement.
“The exercise will involve removing shoal up to the base level of 204 metres through mechanical intervention,” the official said.
The official said weeds with roots above the slushy soil will be removed, besides clearing silt and sand by dredging the riverbed using cutter-suction dredgers with pipelines for disposing of water slurry. “This slurry will be transported to the shore of the lake area downstream for disposal away from the river,” the official said.
Officials said that dredgers attached to kilometre-long and 30-centimetre-wide pipelines will remove slurry at a rate of 1,200 cubic metres per hour. For its disposal, a private contractor will be hired, who will also sell the sand against a portion and royalty to DJB and the revenue department, they said.
According to a DJB report, the work of desilting the Yamuna at Wazirabad was last undertaken in 2013, and that was done on a smaller scale. It was, however, stopped by the National Green Tribunal over sand mining concerns. In 2015, the tribunal permitted the work, noting that “dredging needs to be carried out in public interest and to maintain the flow of the river”. NGT also directed the contractor concerned to pay ₹500 per cubic metre of sand, and said the same will be used for environmental restoration.
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