Construction of world’s largest dam causes uncertainty for downstream countries India, Bangladesh

China has recently approved the construction of what will become the world’s largest hydropower dam, located on the Yarlung Tsangpo River in Tibet. Once operational, it is set to become the most powerful energy-generating facility on Earth by a wide margin but neighbours India and Bangladesh have cause for concern.

The project has sparked widespread concern over its potential impact on both the environment and local communities, which are particularly acute in downstream countries like India and Bangladesh. The river is known as the Brahmaputra in those countries, an article by The Conversation on this energy project recalls. Critics fear the dam will displace residents, disrupt ecosystems, and worsen existing water-related challenges.

The project underscores the complex geopolitical dynamics of rivers that cross national borders. Key questions arise: who owns a river that flows through multiple countries? Who has the right to its water? Are nations obligated to prevent pollution or maintain open navigation channels? And can downstream communities thousands of miles away claim a right to rainfall that falls upstream? These are difficult questions, and international law currently offers limited clarity or consensus on them.

Originating on the Tibetan Plateau, often dubbed the Earth's "third pole" due to its vast glacial reserves second only to the Arctic and Antarctic, the Yarlung Tsangpo is one of several major rivers feeding into South and Southeast Asia. These rivers are vital for more than a billion people across countries such as Pakistan, India, Nepal, Bangladesh, and Vietnam.

But this critical region is already facing water stress due to climate change. Shrinking glaciers and shifting rainfall patterns are reducing river flow during dry seasons, while increasing the frequency and intensity of floods during monsoons. These extremes pose significant risks to agriculture, water supply, and human settlements across the region.

Historically, dam-building in the Himalayas has resulted in the displacement of communities, ecological damage, and increased flood risks. The new Yarlung Tsangpo Grand Dam is unlikely to be an exception. Located in a seismically active area where the Indian and Eurasian tectonic plates meet, the site is prone to earthquakes, landslides, and flash floods, all of which increase the potential danger.

Further downstream, the Brahmaputra River is a lifeline for millions and plays a crucial role in the agriculture and ecology of the region. It carries some of the world’s highest sediment loads, which are essential for maintaining the fertile delta and ecosystems such as the Sundarbans mangrove forest, a UNESCO World Heritage Site. A dam of this magnitude would trap large volumes of sediment, disrupting these natural processes and threatening both food security and coastal resilience.

Despite the Brahmaputra’s transboundary nature, no comprehensive treaty exists to govern its use. The absence of a cooperative framework between China, India, and Bangladesh makes coordinated management and disaster preparedness difficult. While models of successful river-sharing agreements exist, such as the Danube River Convention involving 14 nations and the European Union, many rivers in the Global South, including the Brahmaputra, suffer from a lack of similar international cooperation and scientific research.

By Nazrin Sadigova