Delhi’s wetlands shrink by 9 per cent in 30 years, 97 per cent loss in South Delhi: DU study

Delhi has lost nine per cent of its wetlands in the past three decades as construction and population growth continue to expand, a study conducted by Delhi University (DU) along with HCL Tech and Terna Global Business School has found.

Some districts, including South Delhi, have seen a drop of almost 97 per cent in their wetland area, the study also found.

Published in the journal Research in Ecology in June 2025, the study examined satellite data from 1991, 2001, 2011 and 2021 to track how Delhi’s water bodies have changed over time.

Researchers said the total wetland area in the national capital fell by around nine per cent from 32.9 sq km in 2000 to 30.2 sq km in 2022.

During the same period, the city's built-up area grew from 485.6 sq km to 825.6 sq km, an increase of more than 70 per cent.

The study said the expansion of residential colonies, roads and industries had led to the steady loss of natural water systems. Wetlands, which once helped recharge groundwater and store rainwater, are now being reclaimed or polluted.

According to the findings, South Delhi saw the steepest decline, losing about 97 per cent of its wetland area from 0.8 per cent of its land in 1991 to just 0.025 per cent in 2021.

East Delhi also recorded a major fall, from 0.39 per cent to 0.016 per cent, while North Delhi dropped from 0.27 per cent to 0.001 per cent.

Central Delhi managed to retain most of its water bodies, falling only slightly from 3.72 per cent to 3.26 per cent, helped by its proximity to the Yamuna river and government-protected zones. North East Delhi also maintained better coverage due to its floodplains and conservation work, it said.

The study found that South West Delhi, home to the Najafgarh wetland system, lost more than 90 per cent of its wetland area between 2001 and 2021.

Only New Delhi showed some improvement, with water cover increasing from 0.012 per cent in 2011 to 0.49 per cent in 2021, supported by planned landscaping and restoration projects.

“The continued loss of wetlands has serious implications for groundwater recharge, flood control and biodiversity,” the study said, adding that even small decreases in wetland area can disturb Delhi’s water balance and make the city more prone to flooding.

The researchers said Delhi’s population has grown from 1.47 million in 1951 to nearly 33 million in 2023, while its geographical area has expanded from 201 sq km to 1,467 sq km. This growth, they said, has placed huge pressure on natural water systems.

Satellite images showed how the Yamuna river, once wide and connected to its floodplain, has narrowed over the years. Wetlands such as Najafgarh Lake, Bhalswa and Hauz Khas have shrunk, while Sanjay Lake is now surrounded by dense construction, reducing its function as a natural reservoir.

The paper said the city’s vegetation cover dropped by about 30 per cent, forests by 35 per cent and open land by more than 50 per cent between 2000 and 2022, reducing Delhi’s ability to absorb rainwater and regulate temperature.

It called for strict zoning laws to prevent encroachments, declaring wetlands as protected zones, and building artificial wetlands and rain gardens in urban layouts.

The paper also suggested using satellite monitoring and drone mapping to detect illegal land use and encouraging community participation in restoration drives.

“Delhi’s wetlands are its natural safety valves,” the study said.

“Losing them means losing the city’s ability to store water, cool its air and prevent floods,” it added.