In light of the new cooperative water development agreements in South Asia since 1996 and, in particular, the 1996 Ganges Waters Treaty between India and Bangladesh, this paper explores the geopolitical obstacles to cooperation between states in the joint development of large-scale river systems and current opportunities for successful development. The general problems of cooperation faced by the riparian states which share successive rivers are examined with reference to the geopolitical obstacles to cooperation in the Bengal delta since the Partition of the Indian subcontinent through which India and Pakistan gained Independence as separate states in 1947. Against the background of repeated attempts to resolve water-sharing issues between India and East Pakistan and its successor state, Bangladesh, this paper concludes that for cooperation to succeed contemporary large-scale river development has to meet a wide range of criteria which go beyond conventional engineering or economic cost-benefit analyses to include geopolitical criteria. These range from global-scale environmental concerns to micro-scale issues of mutual regional benefit. This paper proposes a major new development on the Brahmaputra and Ganges which the authors argue could break the log-jam of a zero-sum game approach to surface water development in the Bengal delta. Unlike most large-scale dam-building proposals, the barrage construction outlined would cause negligible population displacement, and making maximum use of existing river channels would minimize the environmental impacts associated with the large canal or dam construction envisaged in earlier Ganges–Brahmaputra–Meghna (GBM) schemes. Yet the paper also recognizes that while such a proposal could bring economic, environmental and political advantages to all users in the GBM basin, new thinking on the management of international rivers is less in favour of supply-side solutions, and the case would need to be substantiated by detailed evaluation.