Discovering key tradeoffs and consequential vulnerabilities for robust water supply investment partnerships under deep uncertainty

Collaborative infrastructure investments are a central component of the Water Resilience Portfolio Initiative, California Governor Gavin Newsome’s blueprint for bolstering water supply reliability and sustainability. The Initiative encourages water suppliers to cooperate in developing shared regional infrastructure to achieve economies of scale, diversification, and other benefits. However, these partnerships also present new risks and challenges. Future climate, demands, and other factors are deeply uncertain over the multidecadal time horizon of these investments, so traditional planning frameworks based on expected costs and benefits may not capture key tradeoffs and vulnerabilities. Moreover, the large number of water suppliers within the interconnected network makes it difficult to select the best subset of partners and an appropriate cost sharing arrangement. Interactions and nonlinear tradeoffs across the infrastructure network amplify the challenge of designing partnerships to provide reliable and affordable water supplies to all participating partners under a broad range of future scenarios. This presentation will demonstrate the use of Many-Objective Robust Decision-Making to discover robust water supply partnerships under deep uncertainty. The Borg Multi-Objective Evolutionary Algorithm is used to discover alternative partnerships representing the optimal tradeoffs between conflicting objectives related to water supply, cost, and size. Resulting partnerships are reevaluated under a broader range of deeply uncertain factors related to climate, demand, regulation, cost, and infrastructure performance, to assess their multi-partner robustness under different states-of-the-world. Finally, scenario discovery techniques are used to elucidate the most consequential uncertainties that tend to lead to partnership success or failure. This work is applied in the context of canal expansion and groundwater banking investments in the Central Valley, using the California Food-Energy-Water System (CALFEWS) simulation model.