Indus basin water flows rose while Ganga declined since 1980, study shows

A study reveals rising Indus Basin water flows contrast with declining Ganga flows since 1980, impacting regional water security.

The Indian sub-continent’s two great northern river systems — the Indus and the Ganga — are moving in opposite hydrological directions, with important implications for water security across South Asia, according to a study published in the peer-reviewed Earth’s Future, a publication of the American Geophysical Union.

Researchers from the Indian Institute of Technology, Gandhinagar analysed changes in streamflow — or how the quantity of water in rivers, lakes, and groundwater varied — between 1980 and 2021 using a high-resolution, physics-based hydrological model that links rainfall, groundwater, river flow, and irrigation pumping. Their findings show that while overall flows in the Indus Basin have increased modestly, the Ganga Basin has experienced a sharp and sustained decline.

According to the study, annual streamflow in the Indus Basin rose by about 8% over the past four decades. In contrast, the Ganga Basin saw a 17% reduction in flow over the same period.

In the Indus system, rising precipitation — particularly linked to western disturbances and variable monsoon contributions — appears to be the main driver of increased river flow. The study finds that the strongest increases are seen in the main Indus River and its western tributaries, the Jhelum and the Chenab. However, the increase is not uniform: two eastern tributaries, the Ravi and Sutlej, have experienced significant declines despite the basin-wide upward trend.

In the Ganga Basin, the picture is starkly different. Rainfall has declined by roughly 10%, while temperatures and atmospheric water demand have increased. But the dominant factor behind falling river flows, the researchers concluded, is intensive groundwater pumping for irrigation.

The research findings intersect with the 1960 Indus Waters Treaty (IWT), which allocates the eastern rivers — Ravi, Beas and Sutlej — to India, and the western rivers — Indus, Jhelum and Chenab — primarily to Pakistan. India suspended the treaty in April 2025, following the Pahalgam terror attack. It has since fast-tracked procedural clearances for hydropower projects to accelerate usage of its share of the western rivers.