Environmental and social considerations in hydropower development in the South Asian Himalayas: a NEXUS perspective

Hydropower plays a critical role in combating climate change while offering significant socio-economic and environmental benefits. However, realizing these benefits in the South Asian Himalayas requires careful integration of environmental and social considerations into hydropower development. We synthesized findings from 204 studies to examine the key challenges associated with hydropower projects in the region, with particular attention to climate change impacts, and nexus approach that integrates water, energy, and food systems. Even though climate change has significantly altered river flow regimes and heightened the risks of glacial lake outburst floods (GLOFs), the study finds that the integration of robust climate risk assessments across the region remains in its infancy and is often regarded as unnecessary. Sedimentation, driven by Himalayan geology, and climate-induced erosion, reduces reservoir capacity and damage turbines with studies indicating up to 25% capacity loss in projects like Kulekhani, Nepal due to inadequate sediment management. Despite the benefits hydropower has offered to the nation and community, social issues such as displacement and compensation, gender and social inclusion concerns, weak governance, and inadequate stakeholder engagements are evident in the SAH region. Furthermore, the review finds that hydropower development in the Himalayas creates intricate trade-offs across water-energy-food-ecosystem nexus, such as reduced downstream sediment affecting agriculture and food security, and synergies like irrigation benefits. This study underscores that sustainable hydropower development in the region requires climate-resilient project designs with GLOFs risk mapping, science-based sediment control to prevent turbine damage and reservoir siltation, inclusive benefit-sharing mechanisms for displaced communities, and WEFE-informed policies to balance energy production with irrigation and ecosystem flows.