Climate change impacts on the small-scale hydropower potential for the Pungwe B hydropower scheme in Zimbabwe using a multi-model climate ensemble

Abstract

Climate change is anticipated to significantly impact hydropower generation in Southern Africa, especially for small-scale producers. This study investigated climate change impacts on the hydropower potential (Pt) of the Pungwe B hydropower scheme in Zimbabwe. The methodology combined hydro-meteorological data, 15 CMIP6 GCMs, statistical analyses, and HEC-HMS hydrological modelling to simulate streamflow. The impacts of climate change on Pt were determined using trends analysis and Power Potential Duration Curves (PPDC). The Hydrological model performed satisfactorily with a Nash-Sutcliffe Efficiency (NSE) of 0.67 and an R2 of 0.66. The results of Pt revealed a general decrease in future trends, categorized into Mid-Century Future (MCF) and Late-Century Future (LCF). The results indicated that the sustainability pathway (SSP1-2.6) forecasts a steady decline in Pt, with 53 % and 67 % of models showing a decrease during the MCF and LCF periods, respectively. The unsustainable pathways (SSP2-4.5 and SSP5-8.5) have more variable results. In the LCF period, 73 % of the models for SSP2-4.5 and 80 % for SSP5-8.5 predicted a long-term reduction. This highlights that extreme weather events and increased variability may lead to short-term fluctuations in hydropower potential rather than a genuine upward trend. Overall, the findings highlight a projected general decrease in hydropower potential for Pungwe B, with specific decreases ranging from 79.6 MW to 100.3 MW depending on the scenario and time-period. The study concludes that these results underscore the critical need for flexible adaptation plans and infrastructure investments to manage increased climate variability and ensure the long-term resilience and sustainability of the project.