Exploring how coordination, robustness, and uncertainties shaping the management of multi-purpose water resources system

Water resources systems require robust management strategies to achieve optimal performance under uncertainties while balancing conflicting objectives. However, these strategies are often derived from a single problem framing, disregarding potential errors and uncertainties that may affect their robustness. This study advances integrated operating policy design for multi-reservoir systems by exploring the robustness of different problem formulations in mitigating the effects of uncertainties on water resources management. We employe the Evolutionary Multi-objective Direct Policy Search (EMODPS) to approximate operating policies under various problem formulations of a multi-reservoir control problem. These policies were then re-evaluated over uncertain flow sets based on different robust definitions (i.e., low to high-risk aversions). Finally, we use a bottom-up scenario discovery method to disclose the states (i.e., success or failure) of the multi-reservoir system. Results show that trade-offs between the objectives of the multi-reservoir system vary significantly across different problem formulations. Although formulations with high-dimensional objectives can improve system trade-offs, they do not necessarily guarantee sufficient robustness to achieve expected performance under uncertainties. In this system, critical runoff signatures identified through bottom-up scenario discovery are independent of the chosen robustness metrics and are most likely to cause the system to cross tipping points from success to failure. These signatures should be continuously monitored and evaluated in future management efforts. This study contributes to the field by highlighting the importance of considering multiple problem formulations and their impact on the robustness of water resources management strategies.