Risk and Vulnerability: Understanding Sensitivities to Climate Change in the Santa Cruz Water Supply System

Climate change and growing water demand can threaten the reliability of urban water supply systems by an increase in water shortage conditions. Foreseen increases in the vulnerability of urban water supply systems positions water managers to take action to reduce those vulnerabilities and increase the resilience of their systems. This study presents a framework for assessing the sensitivity of urban water supply systems to climate change and variability and evaluating proposed infrastructure-based adaptation strategies under anticipated scenarios of climate change. Through ongoing collaboration with the Santa Cruz Water Department, adaptations were assessed using an innovative evaluation framework based on the principles of decision-making under deep uncertainty. Results reveal the vulnerability of the Santa Cruz water supply system to shortage and highlight tradeoffs and opportunities presented by each option, as well as the challenge of summarizing performance and trade-offs between options over a wide range of possible futures. The very real complexity of long-term decisions made under climate uncertainty, including consideration of “bench posts” for decision making is explored, as well as further insights related to the co-production of decision supporting scientific information to communicate results to water utility stakeholders.