Dhaka, Aug. 17 -- Bangladesh has become the first country in South Asia to join the UN Water Convention, a move that regional experts say could reshape the politics of river sharing and test India's longstanding reliance on bilateral agreements.

Observers believe Dhaka's step may encourage other South Asian nations, such as Nepal, Bhutan, and Pakistan, to consider accession, shifting the region towards a multilateral regime that India has long resisted.

On 20 June, Bangladesh formally acceded to the Convention on the Protection and Use of Transboundary Watercourses and International Lakes (Water Convention), a 1992 United Nations treaty that promotes equitable and sustainable sharing of rivers and lakes. Initially confined to Europe und...