Water accounting under climate change in the transboundary Volta River Basin with a spatially calibrated hydrological model

•Integrating a spatially explicit hydrological model with WA+ under climate change.•Multi-scale water account assessment across climatic zones, sub-basins and countries.•Increase in water availability under RCP8.5 corresponding to increase in rainfall.•Higher inter-model and inter-annual variabilities of water accounts over 2021–2050.•Better land and water management is required to increase cross-sectoral benefits.