As part of its mission to clean the Yamuna river, the Delhi government has initiated drone surveys of smaller drains that discharge untreated waste into larger drainage systems.

Delhi Water Minister Parvesh Verma said on 15 July, 2025, that around 300 sub-drains are contributing to the pollution load by emptying waste into the city’s 22 major drains, including the Najafgarh, Shahdara, and Supplementary drains, which flow into the Yamuna. “We are doing drone surveys of all the sub-drains that are adding waste to larger drains. It is important for us to know the origin, entire map and outflow of each of these drains for a comprehensive policy. After we identify the source and the full length of these drains, further steps like installation of D-STPs (decentralised sewage treatment plants) will be taken up,” Minister Verma said.

The Irrigation and Flood Control Department and the Delhi Jal Board (DJB) are simultaneously desilting large drains and treating waste. Due to space limitations for large STPs, DJB plans to install 40 D-STPs, with tenders already floated. The 45-point action plan also includes completing the Interceptor Sewer Project (ISP) by year-end to link drains to treatment plants.