Development and application of statistical seasonal forecasts for reservoir optimization in the Tekezé Basin, Ethiopia

The Tekezé Reservoir in northern Ethiopia is a crucial resource for hydropower generation regionally and nationally, with electricity demand expected to increase in the coming decades. However, achieving reliable power generation is complicated by significant spatial and temporal variability in precipitation within the basin. Additionally, seasonal hydrological forecasts must be developed at an appropriate spatial scale for successful water resources management and decision-making. Chapter 2 develops local-scale precipitation and inflow forecasts leveraging the asymmetric relationship between El Niño Southern Oscillation (ENSO) phase and local hydrological conditions, thereby unveiling additional teleconnections influencing atmospheric moisture transport to the basin. This work demonstrates that a locally tailored statistical forecast approach is skillful for our study site, with potential applications in other regions subject to highly variable hydrological patterns. Chapter 3 couples the forecast developed in Chapter 2 with a reservoir optimization model to determine an optimal operation strategy for maximizing hydropower generation during the rainy season. Adopting a flexible reservoir operation strategy based on seasonal forecast information results in improved maximum hydropower generation and increased minimum firm energy generation compared to climatology-based static operational rule curves. This case study demonstrates the potential benefits of incorporating local-scale hydrological forecast information at the decision-making scale to mitigate the effects of a variable climate for sustainable power generation