Assessment of reservoir performance under climate change: A case study in Shumbrite reservoir, South Gojjam sub-basin, Ethiopia

Climate change has the potential to reduce the water resource availability and hence the amount of storage in reservoirs. In this study, we assessed the impact of climate change on the performance of the Shumbrite reservoir using outputs from the CORDEX-Africa project, MPI Global Circulation Model (GCM) under three Representative Concentration Pathways (i.e., RCP2.6, RCP4.5 and RCP8.5). The trend analysis of future precipitation shows a decrease in the range of 0.57%–4.2%, with a maximum decrease under RCP2.6, and temperature (both maximum and minimum) shows an increasing trend as compared to the baseline period. The HBV model simulated future mean annual flow volume shows a decrease (ranges 0.06% to 1.64%) for RCP2.6 and RCP4.5 and a significant increase of 5.03% for RCP8.5 compared to the baseline period. Mean annual irrigation water demand from CROPWAT shows an increase (0.74% to 8.4%) for all RCPs compared to the baseline period. The time-based reliability for the Shumbrite reservoir has an average value above 80%. The resilience values are below 50% for all RCPs and hence the reservoir will take an extended period to recover from an inability to achieve the target demand volume. The dimensionless vulnerability shows a value below 50% which indicates that the reservoir has no insufficient flow to meet the demand. Generally, the reservoir can be used sustainably with operation rule curves. Generally, this study adds a contribution to the evaluation of small-scale reservoirs under a changing climate and the preparation of guide curves for the respective release.