Bangladesh has just approved one of the largest river engineering projects its history: the Padma Barrage, a vast river-control project intended to restore water in the country’s drought-prone southwest.

It comes at a dangerous moment for South Asia’s rivers. China is building the world’s largest hydropower dam upstream on the Brahmaputra, India is accelerating its own dam-building programme, and the treaty governing Ganges water-sharing between India and Bangladesh expires in December 2026.

Rather than easing regional water insecurity, the Padma Barrage risks adding to a cycle of unilateral river engineering across the subcontinent. South Asia is entering a regional dam-building race – without the institutions needed to share its rivers.

Bangladesh’s water crisis

Supporters say the barrage is a pragmatic response to chronic water insecurity in Bangladesh. The country sits at the end of the vast Ganges-Brahmaputra river system, where rivers that originate in the Himalayas spread into thousands of channels before they reach the sea. Despite all this water, the main river channels are drying up in summer and some smaller rivers are disappearing rapidly.

Bangladesh did not create this problem alone. Since the 1970s, the Farakka Barrage, built across the Ganges upstream in India, has diverted water towards the huge city of Kolkata to flush sediment away from its port.

The consequences for Bangladesh are well documented. Its rivers have dried up and become less navigable. They have also become saltier, groundwater levels have declined, and severe riverbank erosion........

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