Abstract
Risk‐based water resources planning is based on the premise that water managers should invest up to the point where the marginal benefit of risk reduction equals the marginal cost of achieving that benefit. However, this cost‐benefit approach may not guarantee robustness under uncertain future conditions, for instance under climatic changes. In this paper, we expand risk‐based decision analysis to explore possible ways of enhancing robustness in engineered water resources systems under different risk attitudes. Risk is measured as the expected annual cost of water use restrictions, while robustness is interpreted in the decision‐theoretic sense as the ability of a water resource system to maintain performance—expressed as a tolerable risk of water use restrictions—under a wide range of possible future conditions. Linking risk attitudes with robustness allows stakeholders to explicitly trade‐off incremental increases in robustness with investment costs for a given level of risk. We illustrate the framework through a case study of London's water supply system using state‐of‐the ‐art regional climate simulations to inform the estimation of risk and robustness.
Highlights
The 21st century water manager faces significant challenges
This paper has presented a framework for water resources management under uncertainty that links risk-based decision-making and robustness analysis
The framework takes as its starting points the challenges of climate nonstationarity and the importance of robustness to uncertainty to suggest that water management requires a new approach to decisions based on the analysis of trade-offs between robustness and cost under different risk attitudes
Summary
The 21st century water manager faces significant challenges. Climate change, population growth, urbanization, and governance failures are putting pressure on limited and variable resources (AghaKouchak et al, 2015; Liu et al, 2017). Faced with the need to develop long-term strategies, water resources managers seek decisions that achieve robustness over a long period of time and will do so by building flexibility in their water investments Building on these theoretical considerations, this paper presents two methodological innovations for risk-based decision analysis applied to water systems. The water supply system is located in Thames river basin and serves more than 8 million water users, including the city of London It presents the characteristics of many large urban water systems, faced with challenging investment choices to ensure supply security in the context of population growth, climate change, and uncertain regulatory constraints
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