PWD appoints agency for Najafgarh drainage plan

The Public Works Department (PWD) appointed a consultant earlier this week to make a drainage master plan for Delhi’s Najafgarh basin, officials in the know of the matter said on Thursday.

Authorities floated tenders for bidding in May last year and, after selecting the consultant, have given him a year to complete the project, they said.

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“The irrigation and flood control department has already conducted the initial topographical surveys and other studies. The consultant has to now use these to come up with viable and implementable action points. The aim of this drainage master plan is to improve the drainage network so that the system can handle monsoon rain without getting overloaded,” said a senior PWD official.

Authorities also floated tenders last month to appoint consultants for master plans of the other two basins—Trans-Yamuna and Barapullah. Officials said the consultants for the other two basins are also likely to be finalised within the next few months.

To be sure, a new drainage master plan has been long overdue as the Capital’s drainage master plan was last prepared in 1976. Officials explained that when the master plan was last prepared in 1976, Delhi’s population was around 6 million. However, according to the draft of the Master Plan Delhi 2021, Delhi’s estimated population is around 25 million and the total urbanised area is likely to be around 920 square kilometres.

“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. Over the years, there have also been changes to the system, interventions for solutions at some places, blockage and encroachment at other places. All these need to be looked at and solutions implemented,” said another PWD official.

A comprehensive drainage master plan for the entire city was first proposed in 2009. Indian Institute of Technology (IIT) Delhi was initially tasked with making the draft in 2012, which was finally submitted to the authorities in 2018. However, it was not approved by the Delhi government as the solutions proposed were too “generic”.

According to the IIT report, the main problem areas of the Najafgarh basin are drainage congestion due to depressions at numerous places and drains carrying stormwater from outside Delhi. It suggested that changes be made to the cross-section of drains or the 140 small water bodies in the catchment area be rejuvenated to act as temporary storage for runoff water. Another suggestion was using public parks as recharge zones.

“The IIT study mentioned that some stormwater drains should be diverted to parks, but it did not provide implementable action plan detailing which drains should be diverted to which parks and how should that be done. It suggested slope correction but did not mention how and at which points exactly,” said the PWD official quoted above.

In 2021, theDelhi governmentassigned the job to PWD, asking the department to get three separate plans made for the three main drains of Delhi at Najafgarh, Barapullah and Trans-Yamuna basin. The bid for the Najafgarh basin was opened first in 2021 and the work has been allotted now.

Najafgarh is the biggest drain in the National Capital Territory (NCT) of Delhi. It enters southwest Delhi from Haryana. It traverses 57.489km before joining the Yamuna, downstream of Wazirabad barrage. In southwest Delhi, the drain carries floodwater, wastewater from Haryana and surface runoff from the adjoining catchment.

“Nearly 30.943km stretch of the drain passes through southwest district from near Dhansa to Kakraula. Thus, nearly 53.82% of the length of Najafgarh drain flows through southwest Delhi. Moreover, from Dhansa to Kakraula regulator, 28 small drains join this drain and after Kakraula, nearly 74 big and small drains join Najafgarh drain. The Supplementary drain is the second-largest drain in the city which joins the Najafgarh drain just before flowing into the Yamuna. About 71 small drains join the supplementary drain,” a report by the irrigation and flood control department said.

The Najafgarh drain comprises three major blocks—Alipur, Kanjhawala, Najafgarh and some urban parts of southwest Delhi. The total catchment area of Najafgarh drain within Delhi is around 977.26 sqkm.

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Experts say that the master plan is not a zonal plan and can only suggest broad measures like the IIT report did. However, the consultant needs to delve deeper.

“A city’s stormwater system plays a critical role in mitigating urban flooding. While developing a stormwater master plan for an existing city, it is imperative to take cognisance of existing ground situation, in-depth understanding of peak rainfall data along with intensity as well as geological understanding. The stormwater master plan should facilitate techniques that aid groundwater recharge, recycling and the reuse of storm water as well as preserving the natural ecosystems such as water bodies, riparian corridors etc. The plan may consider including strategies for upcoming or greenfield areas specifically,” said Prerna Mehta, associate programme director, sustainable cities and transport, WRI India.