Evaluating Streamflow Forecasts in Hydro-Dominated Power Systems

Seasonal streamflow forecasts are a chief tool that enables operators of water-energy systems to deal with uncertainty in future hydro-meteorological conditions. However, our understanding of the actual potential, or value, of streamflow forecasts remains myopic: this is because their value is typically assessed by considering metrics related to hydropower availability, thus overlooking the role played by hydropower dams within the power grid. With the aim of understanding how the value of streamflow forecasts penetrates through the power grid, we developed a coupled-water energy model that is subject to reservoir inflow forecasts with different levels of predictive performance. We implement the modelling framework on real-world case studies in Southeast Asia, where power supply largely relies on hydropower, coal, gas, and cross-border power trading. In particular, we evaluate the forecast value in terms of metrics selected from both reservoir and power systems, including available and dispatched hydropower, power production costs, CO₂ emissions, and transmission line congestion. Through this framework, we demonstrate that streamflow forecasts can positively impact the operations of hydro-dominated power systems, especially during the transition from wet to dry seasons. Moreover, we show that the value largely varies with the specific metric of performance at hand as well as the level of operational integration between water and power systems.