Processed data supporting the study. The archive contains the catchment-averaged inflow series (historical 1985-2014 and projected) for the Akosombo, Kpong and Bui catchments under five CMIP6 models and the SSP2-4.5, SSP3-7.0 and SSP5-8.5 scenarios; the reservoir and generation model outputs (firm power, capacity factor and spill); the grid-adequacy and energy-security results; and the observed-versus-simulated discharge used for validation at the Nawuni and Bamboi gauges. Analysis code is not included. See the accompanying article for the full methods.