Rainfall in eastern river basins down 20% since 1951: Study on water availability in Indus river system

4 min readNew DelhiUpdated: Jul 10, 2026 04:34 AM IST

The study also found significant depletion of groundwater in the Sutlej and Ravi sub-basins.

In the first-of-its-kind assessment of the impact of climate change on water availability in the Indus river system, a new study has revealed that the catchment areas of the three eastern rivers — Ravi, Beas and Sutlej — saw a 20 per cent decline in precipitation in the period between 1951 and 2024.

On the other hand, rainfall in catchment areas of  three western rivers — Indus, Jhelum and Chenab — was largely stable, with only a 6 per cent reduction observed over the same period, “which is statistically non-significant”, the study has found.

The findings are relevant in view of India’s argument that the Indus Waters Treaty with Pakistan, which governs the sharing of waters of the Indus basin between the two countries, needs to be renegotiated to account for new ground realities created by climate change and other factors like demographic changes. Under the treaty, the waters of the three eastern rivers have been fully allocated to India, while that of the three western rivers are mostly meant for use by Pakistan.

After the Pahalgam terror attack last year, India had declared that it had put the treaty “in abeyance”, meaning it no longer considered itself bound by its provisions.

It has repeatedly maintained that the treaty would remain “in abeyance” until Pakistan “credibly and irrevocably” abjures its support for cross-border terrorism But much before this incident, in 2023 and 2024, India had served more than one notice to Pakistan seeking a “review and modification” of the treaty. India had argued that population pressures, changes in water demand, need for accelerated development of clean energy, and changes in water availability due to climate-induced processes had brought about “fundamental and unforeseen changes in circumstances” that required suitable modifications to be made in the 1960 treaty.

Pakistan has not responded to these notices.

The latest study is the first data-based evidence to support the argument that water availability and the flow in the rivers had been substantially altered over the decades due to climate change. The study was carried out by Vimal Mishra, a professor of Civil Engineering at IIT-Gandhinagar and one of India’s leading researchers on hydrology and the impact of climate change on water resources, and his colleague Urmin Vegad. It is due for publication in a peer-reviewed international journal.

The study also found significant depletion of groundwater in the Sutlej and Ravi sub-basins. The groundwater situation in the Chenab, Jhelum and Indus basins was found to be relatively better, “possibly reflecting limited agricultural use, lower population density, or higher recharge from snowmelt and precipitation”. The study found a “pronounced decline” in annual inflow of water in the reservoirs of major dams on the eastern rivers like Pong, Bhakra and Thein. The reservoir of Pong dam, for example, saw a decline of nearly 34 per cent in annual inflows between 1951 and 2020. The major reservoirs in Pakistan, on the other hand, were not substantially affected. Flows into Mangla and Tarbela dams, two of the biggest in Pakistan, both built on the western rivers, remained mostly stable, with very minor declines.

Story continues below this ad

“Most of these changes are due to natural causes. Maybe, groundwater depletion is man-made. But others are all a result of natural variabilities. And these do alter the situation that existed in 1960 when the Indus Waters Treaty was signed,” Mishra told The Indian Express.

The study says these largescale changes may make the treaty unsustainable in the long run. “The treaty was designed in the mid-20th century amid hydro-climatic conditions that differ remarkably from the recent period. Since the formation of the treaty, the Indus River Basin has undergone substantial hydro-climatic and geopolitical changes that have led to questions about its long-term sustainability,” it says.