The next India-Bangladesh Ganges treaty must also protect the river

With the Bangladesh National Party’s recent announcement that the future of its ties with India will “depend on” the Ganges water treaty, it is clear that this is a hugely significant moment for their diplomatic relationship. But the overarching focus on water allocation and diplomacy could mean that another important aspect — river health — is overlooked. As climate change alters the assumptions underlying many existing water-sharing arrangements, we should also be asking the question: Just how much ecological stress can the Ganges system continue to absorb?

South Asia is among the regions most vulnerable to climate change, according to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). That vulnerability is being intensified by rapid population growth, poverty, water scarcity, weak governance and growing tensions over transboundary rivers. Few regions in the world have been shaped by rivers as profoundly as South Asia. The Ganges, Brahmaputra and Meghna river systems have sustained civilisations, economies and cultures for centuries.

Climate change is already disrupting Himalayan glaciers, monsoon patterns and river flows across the region. In parallel, there are emerging signs of ecological stress across the basin, including impacts on livelihoods, fisheries, flooding and salinity. Recent research suggests that several major rivers in the region, including the dry-season Ganges flows, are approaching dangerous ecological limits. Reduced river flow – driven by a combination of climate pressures, changing hydrology and upstream water diversion – has contributed to rising salinity, pressure on agriculture, degradation of aquatic ecosystems and declining river-based fisheries.

The transboundary nature of rivers means that local water pressures can quickly become regional challenges. Across the Ganges-Brahmaputra-Meghna basin, reduced river flow and rising salinity are increasing environmental stress, particularly in vulnerable coastal regions of eastern India and Bangladesh. Sustained freshwater flows are essential to counter sea-level rise from the Bay of Bengal and protect the Sundarbans, the world’s largest mangrove forest shared by India and Bangladesh.
At the same time, pollution from industrial waste, sewage and agricultural runoff continues to degrade river systems across South Asia, underlining the need for stronger regional cooperation on river management. Altered flow regimes have further reduced hydrological connectivity between the river and adjacent wetlands. Declining seasonal flooding limits nutrient exchange and habitat availability, undermining biodiversity and weakening wetlands that function as carbon sinks and buffers against climate variability.

The consequences of river disruption are also being felt within India itself. Indian experts have linked the Farakka Barrage to increased flood risks in parts of Bihar due to sediment build-up upstream between Patna and Bhagalpur, which can reduce river capacity and intensify flooding during heavy monsoon periods. The Ganges once delivered large sediment loads that sustained floodplains and the delta. The Farakka Barrage now traps much of this sediment upstream, creating a major imbalance. Upstream aggradation raises flood risk, while downstream sediment depletion weakens the delta’s capacity to resist erosion and sea-level rise. Intensified riverbank erosion, land subsidence, and habitat loss now threaten long-term river stability.

In West Bengal, declining fish populations, particularly Hilsa, continue to affect livelihoods and cultural traditions, including festivals such as Durga Puja and Jamai Sasthi. The Farakka Barrage blocks the migratory pathways of fish. The collapse of Hilsa fish migration, once widespread across the Ganges basin, illustrates the scale of disruption to both ecology and fisheries. In addition, the ecological impacts of declining biodiversity are evident through the endangerment of the Gangetic dolphin, gharial, and diverse fish communities due to disruption of habitats and ecological connectivity caused by the Farakka Barrage.

The Ganges is not merely a river but a dynamic living system that sustains millions of people and a rich diversity of species. Safeguarding its ecological integrity demands science-driven policy, coordinated action across sectors, and a sustained commitment to long-term, sustainable river management.
One solution could be introducing the concept of a “safe operating space” for rivers. An international study I led with colleagues at Bangladesh University of Professionals, Bangabandhu Sheikh Mujibur Rahman Agricultural University and Riverine People was the first to define a safe operating space (SOS) for major rivers in the Ganges Delta. Our research found that four out of ten rivers in the Bangladesh Delta exceeded the SOS and that the majority of river flow has been significantly altered, with the remaining six rivers classified as being in a cautious state. The study shares valuable scientific evidence that will inform science and policy related to transboundary water and contribute to the achievement of Sustainable Development Goals (SDGs) in Bangladesh and South Asia. It is something that is worthy of consideration when reconfiguring the Water Treaty.

Ultimately, while it is important to ensure that shared rivers remain a source of regional stability rather than growing geopolitical tension, we must also take immediate action to ensure the river remains resilient enough to support both countries in the decades ahead — not doing so risks leaving insufficient healthy water for everyone whose livelihood depends on it.

The writer is Associate Professor, School of Social and Environmental Sustainability, University of Glasgow