Yamuna loses 90% water flow in Delhi: Okhla and ITO barrages linked to river narrowing to 32% of its 1799 width; Delhi University study maps 200-year change

The Yamuna flowing through Delhi today is less than a third of the river it was two centuries ago, with its average width down 68% and its water flow down nearly 90% since 1799, according to a new study by geologists from Delhi University and the Indian Institute of Science Education and Research, Bhopal.

The findings, published in the Journal of Geological Society of India, are drawn from what researchers say is one of the longest reconstructions of the Yamuna's changing course in Delhi, covering roughly 200 years of the river's 50-kilometre stretch through the capital.

From 658 metres to 210 metres


To map the river's decline, the research team used historical maps dating to 1799, old topographic surveys, satellite imagery, and systematic river-width analysis across different time periods.

What they found was stark. The Yamuna's average bank width, which stood at around 658 metres in 1799, has narrowed to approximately 210 metres today. Its estimated discharge, once close to 30,000 cubic metres per second, has fallen to around 3,900 cubic metres per second.

Put simply, the river that runs through Delhi now carries barely 13% of the water it once did.

A river blocked at every turn

The study traces the decline to a long chain of engineering interventions, starting with the British-era Tajewala and Okhla barrages built in the 1870s, and continuing through later structures including the Wazirabad, ITO, and Hathnikund barrages.

Professor Vimal Singh of Delhi University's geology department, one of the study's authors, explained the basic problem plainly. Water gets diverted upstream through barrages and canals, leaving the river with very little to carry downstream through the city.

The researchers also found that roughly one-third of Delhi's floodplains have become disconnected from the river over the past century, cut off by embankments and urban development spreading into land the river once seasonally occupied.

River islands and channel bars, which are natural features that reflect a healthy sediment flow, have also collapsed. The study documented a fall from around 20 square kilometres of such formations in 1985 to just 4 square kilometres by 2020.

The city moved in, the river paid the price

Professor Singh pointed to a straightforward but consequential dynamic. The Yamuna floods for roughly 15 days to a month each year. Outside that window, the floodplain sits dry, and over decades, Delhi's expanding population came to see it as vacant land.

"People started seeing this as vacant land and started encroaching upon it," he said, adding that this pattern is not unique to the Yamuna and is playing out along rivers across the world.

Delhi's population has grown from around 250,000 in the early 19th century to over 21.5 million today. The river's capacity has moved in the exact opposite direction.

Why 2023 floods were worse despite lower discharge

One of the study's more striking findings concerns the 2023 Delhi floods, when the Yamuna recorded its highest-ever water level, even though the peak discharge that year was lower than during the devastating 1978 flood.

The researchers argue this is a direct consequence of what has been done to the floodplain. With embankments hemming the river in and encroachments blocking its natural spread, floodwater can no longer move laterally. It stays confined within the narrowed channel, pushing water levels higher than they would otherwise reach.

The authors describe the Yamuna in Delhi as having shifted into a permanent low-flow regime, driven not by changes in rainfall or climate, but by human intervention.

A note on the data

The research team, which also included Professor Sampat Kumar Tandon and researcher Tanya from Delhi University's geology department, alongside Professor Kumar Gaurav of IISER Bhopal, was careful to flag the limitations of working with historical data.

Some of the oldest maps were made for tourism rather than scientific survey purposes and may overstate the river's original width. Satellite-derived measurements for recent decades also carry their own margin of error.

The researchers have asked that their figures not be treated as exact historical measurements. Even so, they stand behind the study as one of the most comprehensive long-term records of how the Yamuna has changed as it moves through the capital.

(With TOI inputs)