New Delhi: A study by geology researchers at Delhi University and Indian Institute of Science Education and Research (IISER), Bhopal, has shown that the Yamuna flowing through Delhi today is a fraction of what it was two centuries ago. The study has found that the river’s average width has shrunk by nearly 68%, while its estimated discharge has dropped by 89% since the late 18th century.The researchers have argued that the cumulative impact of the construction of barrages, embankments, canals and rapid urbanisation has fundamentally altered the river’s natural seasonal flow.A TOI report, dated Sept 5, 2025, during the flooding of the Yamuna, pointed out how the carrying capacity of the river had shrunk. The study bore out the extent of this observation.Published in the Journal of Geological Society of India, the study reconstructed around 200 years of changes on the 50-km Delhi stretch of the Yamuna. The geologists used historical maps dating back to 1799, old topographic surveys, satellite imagery and river-width analysis.They estimated that the river’s average width of the banks reduced from around 658 metres in 1799 to about 210 metres now. Correspondingly, the estimated discharge declined from nearly 30,000 cubic metres per second to around 3,900 cubic metres per second.The research linked these changes to a series of engineering interventions, beginning with the British-era Tajewala and Okhla barrages in the 1870s, followed by structures such as the Wazirabad, ITO and Hathnikund barrages. Professors Vimal Singh of Delhi University’s geology department, who is one of the authors of this study, explained that “water gets diverted and river itself has little water downstream becasue of the barrages and canals upstream.”“The irony is that Delhi’s population has grown and thus the city also needed space to expand. Now, the maximum flooding is around 15 days to roughly a month annually. Other than that time, the water does not occupy the floodplain. So, people started seeing this as vacant land and started encroaching upon it. The width thus reduced from 658m in 1799 to just 250m. With floods, the river is actually claiming its area. We also started making embankments. Its not just with Yamuna. This is happening all over the world,” professor Singh said.The researchers estimated that about one-third of Delhi’s floodplains have become disconnected over the past century because of embankments and urban development. They also documented a sharp decline in river islands or channel bars — from roughly 20 sqkm in 1985 to about 4 sqkm by 2020 — reflecting major changes in the river’s sediment dynamics.The study said the alterations have reduced the Yamuna’s natural ability to absorb extreme floods. During the 2023 flooding, Delhi experienced its highest recorded water level despite a lower peak discharge than the devastating 1978 flood. The authors suggested that embankments and floodplain encroachments prevented the water from spreading laterally, forcing more water to remain confined within the narrowed river corridor, thereby raising the water level.The authors pointed out that Yamuna in Delhi has transitioned into a “lower flow” regime, driven largely by human intervention, rather than natural climatic shifts. While Delhi’s population has grown from roughly 250,000 in the early 19th century to about 21.5 million at present, the river’s discharge has moved in the opposite direction.Other than professor Singh, professors Sampat Kumar Tandon and Tanya from the department of geology, University of Delhi, along with Kumar Gaurav of IISER Bhopal conducted the research. The researchers also cautioned against treating their estimates as exact historical measurements. They acknowledged that historical maps are scarce and vary in accuracy, with some prepared for tourism rather than for scientific surveys. The oldest maps may overestimate the river’s width, while satellite-derived estimates for recent decades also carry measurement uncertainties.Even with these limitations in mind, the study presents one of the longest reconstructions of the Yamuna’s changing riverscape in Delhi.
