Sustainable hydropower challenges for transboundary Himalayan River Tista: Strengthening future water-sharing between India and Bangladesh

The growing demand for renewable energy highlights hydropower as a key source for achieving global energy security and sustainable development. Hydropower accounts for 70 % of renewable energy worldwide, yet significant untapped potential remains, particularly in transboundary river basins where socio-environmental and geopolitical challenges often hinder hydroelectric projects (HEPs). This study examines the transboundary Himalayan River Tista, shared by upstream India and downstream Bangladesh, where 14 HEPs with 3500 MW capacity have altered basin hydrology, disrupted ecosystem services, and heightened water-sharing tensions between riparian nations. The proposed equitable (50–50 proportion) water-sharing framework for resolving Tista water tensions, remain insufficient as it focuses solely on water allocation while neglecting socio-ecological demands and environmental flow concerns. Hence, this study advances a cooperation framework of hydropower as a water benefit-sharing mechanism that addresses sustainable energy generation with transboundary water governance. The study highlights key challenges of hydropower generation, including climate change, natural hazards, reduced downstream flows, and increasing dry season water demand, which affect riparian nations. By addressing these challenges, this study explores strategies to balance energy production with sustainable water management, by equitably allocating 71.5 MW of hydroelectricity to downstream Bangladesh during dry seasons. This quantification of benefit-sharing framework offers a promising solution to mitigate Tista water tensions, balances sustainable hydropower generation and enhances transboundary river cooperation. This work outlines how benefit-sharing can be expanded to explicit mechanisms of transboundary hydropower cooperation, contributing to policy strategies to foster water-energy security and regional cooperation.