Water and energy are two fundamental elements for achieving sustainable development in South Asia, a region facing many challenges of achieving the sustainable development goals under resource constraints. Water and energy are inherently inter‐dependent which requires a nexus perspective to address their synergy. However, sectoral approaches have been often used to deal with these twos interacting issues. It is therefore important to understand the quantitative linkage of water and energy and therefore find the opportunities by addressing the nexus at the planning stage for better resource management and utilization. This study aims to conduct an integrated assessment on water‐energy nexus which will be influenced by climate change up to 2050. An empirical study for the Ganges Basin have been conducted to develop and apply a methodology by linking different modelling techniques (hydrological modelling, energy scenario analysis and GIS spatial analysis) to address the practical conflicts between water and energy supply. Three case studies on the projection of water availability under future climate scearnios (RCP4.5 and RCP8.5) at the river basin or sub-river basin levels using the hydrological modelling tool (SWAT), the projection on water demand in agriculture sector, industrial sector and domestic sector and power plant field surveys on water use under different power generation technologies and cooling systems were conducted for Nepal, India and Bangladesh. Together with energy scenario analysis and GIS spatial analysis to be conducted in Year 2 of this project, this study can be expected to deliver an integrated assessment on the linkage of water and energy and a planning‐aid tool for the energy sector based on water stress analysis.