Process begins to hire experts for Delhi’s drainage basins

Officials said the move will be crucial to help rid the Capital of its annual waterlogging woes during the monsoon

The Public Works Department (PWD) has started the process of hiring private consultants to undertake a topographical survey of two of Delhi’s three drainage basins — Barapullah and Trans-Yamuna — to implement drainage solutions and prevent urban flooding. Officials aware of the project said the move will be crucial to help rid the Capital of its annual waterlogging woes during the monsoon, and will help devise flood mitigation measures.

Officials said the experts will help formulate flood mitigation in wake of the flooding experience in July earlier this year. (Sanchit Khanna/HT)

Delhi has 201 natural drains, divided into three natural drainage basins — Najafgarh basin with 123 drains covering an area of 977.2sqkm, the Barapullah basin (44 drains across 376sqkm) and the Trans-Yamuna basin (34 drains spread over 197sqkm). Though Delhi’s drains are overseen by nine different agencies, the government in 2021 appointed PWD as the nodal agency for implementation of the drainage masterplan.

A PWD official said a consultant for the Najafgarh basin was appointed in May this year, but the process to hire consultants for the Barapullah and Trans-Yamuna basins stalled due to the participation of very few bidders. This process, the official said, declining to be named, has now been restarted, with norms tweaked to increase the participation of experts who can meet the criterion.

The official said that Delhi’s last drainage masterplan was prepared in 1976, when the city’s population was around 6 million, which has now swelled to an estimated 25 million. “With changing geographical and demographic conditions over the years, it is important to upgrade and modify the drainage network so that it can handle the discharge,” the official said.

According to the official, a study for the Najafgarh basin is already underway. “Bids will be finalised on September 19. The consultants will focus on turning a July 2018 report by the Indian Institute of Technology, Delhi (IIT-D) on the drainage masterplan into actionable interventions and tackling waterlogging at vulnerable sites. They will also undertake hydrological studies and help formulate flood mitigation in wake of the flooding experience in July earlier this year. In July, many drains witnessed backflow and flooding due to the Yamuna level rising,” the official said.

Once finalised, the agencies will be provided six months to complete the topographical survey, field survey and hydraulic study, as well as finalise a solution-providing report. “One year would be provided to help in the execution of work to remodel the drainage network, and the subsequent one-year testing and monitoring of the locations and the impact made due to the interventions would be under scanner,” the official said.

Activist Diwan Singh, who led the Yamuna Satyagrah to rejuvenate the Yamuna and other water bodies in Delhi, said the scientific mapping of Delhi’s natural drainage network is a welcome step but must be followed by corrective steps. “A large number of natural drains in the city are either encroached, some are even missing. As far as possible, we should rely on natural gravity based drainage flow for which natural drainage in basins needs to be restored,” he said.