Navigating Regional Robustness Conflicts By Discovering Cooperative Safe Operating Spaces for Regional Water Supply Portfolios

The performance of short-term urban water supply portfolios may be heavily influenced by uncertainties relating to long-term hydroclimatic or socio-economic trends. Regional cooperation among urban water utilities can improve the efficiency and robustness of water supply portfolios to such uncertainties through coordination mechanisms such as water transfers, demand management and shared infrastructure. Regionalization does however come at a cost. Regionally coordinated water supply plans may be vulnerable to emerging instabilities in the regional coalition. If one or more actors does not cooperate or follow the robust regional actions suggested, the robustness of the overall regional system, as well as its component sub-systems, may severely degrade. Prior work regarding uncertainty in water supply planning and management has largely neglected uncertainties surrounding implementation for regional systems. This study contributes a methodology for discovering individual and cooperative "safe operating spaces" across the decision and uncertainty spaces of cooperating regional water utilities. The safe operating spaces specify operational tolerances to ensure the stability of the regional coalition and identify important thresholds within the uncertainty space that cause portfolios to fail to meet stakeholder criteria. The methodology is demonstrated on a system of four interconnected water utilities in the Research Triangle region of North Carolina for which robust regional water supply portfolios have previously been designed using multi-objective optimization. Results of this analysis will assist utilities in choosing the appropriate regional portfolio for implementation and creating a monitoring plan to trigger adaptive actions as information about future states of the world is observed.