The two major northern river systems of the Indian subcontinent—the Indus and the Ganges—move in opposite hydrological directions, with important implications for water security across South Asia. a study published in the peer-reviewed journal Earth’s Future, publication of the American Geophysical Union.
Researchers at the Indian Institute of Technology in Gandhinagar analyzed streamflow changes – or how the amount of water in rivers, lakes and groundwater changed – between 1980 and 2021 using a high-resolution, physics-based hydrological model that links rainfall, groundwater, river flow and irrigation. Their findings show that while total flows in the Indus basin increased slightly, the Ganges basin experienced a sharp and sustained decline.
According to the study, annual flow in the Indus basin has increased by about 8% over the past four decades. In contrast, the Ganges basin experienced a 17% reduction in flow over the same period.
Significant differences
In the Indus system, increasing rainfall—especially associated with western disturbances and variable monsoons—appears to be the main driver of increased river flow. The study found that the strongest increases are seen in the main river Indus and its western tributaries, the Jhelum and the Chenab. However, the increase is not uniform: two eastern tributaries, the Ravi and the Sutlej, have seen significant declines despite a basin-wide upward trend.
In the Ganga basin, the picture is quite different. Rainfall has decreased by about 10%, while temperatures and atmospheric water demand have increased. But the dominant factor behind declining river flows, the researchers concluded, is intensive groundwater pumping for irrigation.
Implications of the Indus Waters Treaty
The findings of the research intersect with the Indus Waters Treaty (IWT) of 1960, which allocates the eastern rivers – Ravi, Beas and Sutlej – to India and the western rivers – Indus, Jhelum and Chenab – mainly to Pakistan. India suspended the treaty in April 2025 after the Pahalgam terror attack. Since then, it has expedited the permitting process for hydroelectric projects to speed up the use of its stake in western rivers.
Vimal Mishra, an IIT-G professor and one of the co-authors of the study, told The Hindu that these trends showed that climate change and human use of water “demanded” a rethinking of water-sharing arrangements under the IWT. “Agriculture in Pakistan is heavily dependent on water from the main Indus and increased rainfall means it is not as affected as in eastern Punjab, India, where groundwater is depleting,” he told The Hindu.
Depleted impact on groundwater
Groundwater normally supplies rivers gradually through underground discharge, especially during dry months. The study estimates that in parts of the Ganges basin, groundwater contributes 50% to 70% of the river’s annual flow. When farmers pump heavily—especially during weak monsoon years—less groundwater enters rivers. In some stretches of the Yamuna and the upper Ganges, the natural direction of flow between aquifers and rivers has even reversed, with rivers losing water to depleted groundwater systems.
Using a two-stage statistical attribution framework, the authors estimate that 60% to 80% of the decline in flow in major Ganga sub-basins such as the Yamuna, Upper Ganga and Ramganga can be traced to groundwater extraction, including withdrawals induced by rainfall deficits during drought years.
The study’s methodology relies on a surface and groundwater model known as ParFlow-CLM, which has been running at a resolution of roughly 5 kilometers for 42 years. The model was then given input data such as observed rainfall, temperature, soil, land use and irrigation. Its results were validated against available flow measurements, observations from the Gravity Recovery and Climate Experiment (GRACE) satellite, and data from more than 1,500 monitoring wells, which show strong agreement in groundwater trends.
Integrated management needed
The authors call for integrated surface and groundwater management. Treating rivers and aquifers as separate systems, he argues, is no longer viable in an agriculture-dominated region where pumping decisions directly affect river flows. “We cannot continue to indiscriminately pump water as if it were a free resource. Water use efficiency, changes in the types of crops grown must be seriously considered,” Prof Mishra added.
In their study, the authors recommend more adaptive irrigation practices, crop diversification away from water-intensive crops in drought-prone years, and water planning in line with long-term climate variability. Without coordinated groundwater regulation and climate-aware management, the study warns, river drying in the Ganges basin is likely to intensify.
Published – 14 Feb 2026 19:50 IST