Delhi is sinking at a rate of 51 mm annually, faster than any other Indian megacity, endangering 1.7 million residents, a study has found. Groundwater over-extraction is primary cause, creating a "complex and critical nexus" of risk when combined with climate change and extreme weather. About 196 km² in Delhi is affected, with major hotspots in Bijwasan, Faridabad and Ghaziabad.