Linking climate projections to performance: A yield-based decision scaling assessment of a large urban water resources system

Despite a decade of research into climate change impacts on water resources, the scientific community has delivered relatively few practical methodological developments for integrating uncertainty into water resources system design. This paper presents an application of the “decision scaling” methodology for assessing climate change impacts on water resources system performance and asks how such an approach might inform planning decisions. The decision scaling method reverses the conventional ethos of climate impact assessment by first establishing the climate conditions that would compel planners to intervene. Climate model projections are introduced at the end of the process to characterize climate risk in such a way that avoids the process of propagating those projections through hydrological models. Here we simulated 1000 multisite synthetic monthly streamflow traces in a model of the Melbourne bulk supply system to test the sensitivity of system performance to variations in streamflow statistics. An empirical relation was derived to convert decision-critical flow statistics to climatic units, against which 138 alternative climate projections were plotted and compared. We defined the decision threshold in terms of a system yield metric constrained by multiple performance criteria. Our approach allows for fast and simple incorporation of demand forecast uncertainty and demonstrates the reach of the decision scaling method through successful execution in a large and complex water resources system. Scope for wider application in urban water resources planning is discussed

Sustainable water management under future uncertainty with eco-engineering decision scaling

The published version of this paper can be found at: http://dx.doi.org/10.1038/nclimate2765Managing freshwater resources sustainably under climatic uncertainty poses novel challenges. Rehabilitation of aging infrastructure and the construction of new dams are viewed as solutions to manage climate risk, but attaining the broader goal of freshwater sustainability will require expansion of the water resources management paradigm beyond narrow economic criteria to include socially‐valued ecosystem functions and services. We introduce a new decision framework, called Eco‐engineering decision scaling (EEDS) that explicitly and quantitatively explores tradeoffs in stakeholder‐defined engineering and ecological performance metrics across a range of management actions and future climate states. We illustrate its potential application through a hypothetical case study of the Iowa River USA. EEDS holds promise as a powerful tool for operationalizing freshwater sustainability through incorporation of ecological vulnerability in the design and operation of resilient infrastructure