Operationalizing equity in multipurpose water systems

Participatory decision-making is a well-established approach toaddress the increasing pressure on water systems induced by growingmulti-sectoral demands and increased competition among different waterusers. However, most existing approaches search for system-wise efficientsolutions and do not quantify their distributional effect among thestakeholders. In this work, we investigate how to operationalize equityprinciples to design improved water systems operations that better balanceefficiency and justice. More specifically, we explore the extent to which theinclusion of equity principles reshapes the space of efficient solutions.Numerical experiments are conducted on the Lake Como system, Italy, operatedprimarily for flood control and irrigation water supply while also providingrecreation and river ecosystem services. Our results show how incorporatingequity considerations into the design of water system operations enrichesthe solution space by generating more compromise solutions than thoseobtained using a traditional multi-objective optimization. Moreover, we findthat including equity in the operating policy design can indirectly improvethe performance of marginalized sectors, such as recreation and ecosystem,which are not explicitly considered by the current lake operation. Lastly,we illustrate how the aggregation of multi-sectoral interests into an equityindex strongly shapes our results. Thus, eliciting the preference structure ofstakeholders and policymakers becomes paramount for the identificationof a fair balance across competing interests. This work bridges the gapbetween multi-objective optimization approaches and equity-informeddecision-making for real-world water resources planning and management,providing an effective tool to promote efficient and equitable policies.