Operationalizing equity in multipurpose water systems operations

Growing energy and food demands are increasing the pressure on many water systems and are exacerbating the competition between different water users, suggesting the need for participatory approaches involving all the conflicting stakeholders in order to negotiate potential compromise solutions. However, most of the existing approaches search for efficient solutions by adopting a posteriori decision-making tool to enable the exploration of tradeoffs, but often do not quantify how the resulting benefits are distributed across the stakeholders. In this work, we investigate how to operationalize equity principles into the design of improved water systems operations to discover new operating policies that better balance the tradeoffs between the competing stakeholders’ interests. More specifically, we analyze alternative problem formulations with different number of objectives, i.e., shifting from a traditional multi-objective to a many-objective optimization, and with/without the inclusion of an equity index among the objective functions. The approach is demonstrated on the operation of Lake Como, a regulated lake in Northern Italy primarily operated for flood protection and irrigation supply, along with other operating objectives such as prevention of low levels and ecosystem preservation downstream of the lake. Our results show that including equity in the operating policy design can indirectly improve the performance in terms of secondary objectives that are not explicitly included in the optimization problem. Moreover, we show that many-objective optimization tends to search for the tradeoff between competing objectives, while an optimization incorporating equity consideration enriches the solution space by generating more compromise solutions mitigating the conflicts between the operating objectives. Lastly, we explore the sensitivity of our approach with respect to the definition of the utility functions used for aggregating the performance across the different objectives into a single equity metric. This work bridges the gap between multi-objective optimization approaches and equity-informed decision-making for real-world water resources planning and management, providing an effective tool to promote the implementation of efficient and equitable water resources policies.