5Emerging water scarcity concerns in many urban regions are associated with several 6 deeply uncertain factors, including rapid population growth, limited coordination across ad-7 jacent municipalities and the increasing risks for sustained regional droughts. Managing 8 these uncertainties will require that regional water utilities identify coordinated, scarcity-9 mitigating strategies that trigger the appropriate actions needed to avoid water shortages 10 and financial instabilities. This research focuses on the Research Triangle area of North 11 Carolina, seeking to engage the water utilities within Raleigh, Durham, Cary and Chapel 12Hill in cooperative and robust regional water portfolio planning. Prior analysis of this region 13 through the year 2025 has identified significant regional vulnerabilities to volumetric short-14 falls and financial losses. Moreover, efforts to maximize the individual robustness of any 15 of the mentioned utilities also have the potential to strongly degrade the robustness of the 16 others. This research advances a multi-stakeholder Many-Objective Robust Decision Mak-17 ing (MORDM) framework to better account for deeply uncertain factors when identifying 18 cooperative drought management strategies. Our results show that appropriately designing 19 adaptive risk-of-failure action triggers required stressing them with a comprehensive sample 20 of deeply uncertain factors in the computational search phase of MORDM. Search under 21 the new ensemble of states-of-the-world is shown to fundamentally change perceived perfor-22 mance tradeoffs and substantially improve the robustness of individual utilities as well as 23 the overall region to water scarcity. Search under deep uncertainty enhanced the discovery 24 1of how cooperative water transfers, financial risk mitigation tools, and coordinated regional 25 demand management must be employed jointly to improve regional robustness and decrease 26 robustness conflicts between the utilities. Insights from this work have general merit for 27 regions where adjacent municipalities can benefit from cooperative regional water portfolio 28 planning. 29 1 INTRODUCTION 30 Understanding and exploring the combined states-of-the-world (SOWs) that shape wa-31 ter supply risks is a fundamental challenge in any drought mitigation application, defining 32 perceptions and preferences related to key performance objectives, vulnerabilities, and/or 33 the robustness of a system. Fundamental to this challenge is the choice of what uncertain 34 factors should be sampled or included in generating alternative scenarios. Broadly, there 35 are two dominant methodologies that are at present used in water supply planning contexts: 36 (1) pre-specified deterministic scenarios/narratives and (2) globally sampled stochastic sce-37 nario analysis. As an example of deterministic scenario-based planning, Liu et al. (2008) 38 analyzed four semi-arid river basins in the south-western United States seeking to find water 39 management strategies based on integrat...
Regional cooperation among water utilities can improve the robustness of urban water supply systems to challenging and deeply uncertain futures. Through coordination mechanisms such as water transfers and regional demand management, water utilities can improve the efficiency of resource allocation and delay the need for new infrastructure investments. Though cooperation provides utilities with the potential for reduced cost strategies for improving the reliability of their services, two important challenges are worthy of careful consideration. First, regional utilities often have to navigate robustness conflicts stemming from potential asymmetries in their risk exposure, demand dynamics, and the availability of supply resources. Second, successful implementation of candidate compromise water portfolios requires that cooperating utilities understand their operational tolerances to deviations from the recommended regional actions (“imperfect implementation”). This study contributes a framework for identifying compromises across regional robustness conflicts and quantifying tolerances to implementation uncertainties. The framework is demonstrated on a system of four interdependent but institutionally independent water utilities in the Research Triangle region of North Carolina that are confronting robustness conflicts given asymmetries in their vulnerabilities to growing demands and hydroclimatic uncertainties. Our findings highlight that seemingly balanced compromise management strategies can yield significant and potentially surprising unintended consequences that could degrade regional cooperation. Moreover, asymmetries in regional robustness can be amplified with modest deviations from their agreed upon actions. Results of this analysis are broadly applicable to water supply regionalization as a global challenge and provide insights for discovering robust compromises and safe operating spaces for multi‐actor water supply systems.
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