Adaptive normative constraints to mitigate climate change induced conflicts in a snowmelt dominated water system

The sustainability of many water systems worldwide is challenged by the profound alterations in the hydrologic regime due to changes in climate and growing demands. This is particularly true for snowmelt-dominated catchments, where even marginal temperature variations might dramatically shape the snowpack and glaciers dynamics, with impacts on the inflow’s spatial and temporal distribution. Building new infrastructures to upgrade the storage capacity is nowadays considered the predominant option to cope with the new hydroclimatic regime. However, this hard solution often requires considerable financial outlays. In addition, when designed without fully considering the uncertainties in future inflow patterns, it might fail in producing the adaptation response which triggered the investment for its construction. In this context, tailoring the normative constraints which define the reservoir discretionary operational capacity upon the hydrological regime, might represent a soft and cost-effective alternative to upgrading system infrastructures. In this study, we propose an integrated approach where the reservoir control policy and discretionary operating space are jointly designed to mitigate the ongoing and future climate change impact on a multi-stakeholder water system. We employ Evolutionary Multi-Objective Direct Policy Search, possibly informed by forecast information, to the recursive planning of the discretionary operating space boundaries, internalizing the operation design problem. The approach is tested using the Lake Como system in Northern Italy, a highly regulated water system where climate change-induced hydroclimatic uncertainties are already shaping the tradeoffs between downstream irrigation, hydropower production, flood protection and the tourism sector. We show that the operating policies found via joint optimization fully dominate those obtained considering the actual normative settings. In addition, they are also more robust against the longterm perturbation in the hydrological regime induced by climate change, even though adaptation in the irrigation demand patterns appears necessary to ensure the sustainability of the water system.