Urban areas face an array of environmental stressors including droughts and heat waves that challenge the resilience of critical sectors such as water supply, the electricity grid, and human health. Moreover, because cities and their inhabitants interact with local environmental processes in tightly coupled ways, efforts to manage the impact of environmental stressors in one sector can often influence impacts in other sectors. For instance, efforts to increase urban forestry to mitigate heat waves and improve public health can have the added benefit of reducing stress on the electricity grid, but may require additional water inputs, particularly in times of drought. As cities continue to develop, global and regional scale climate changes will interact with local-scale changes in urban form, vegetation management practices, and water infrastructure to yield complex outcomes across multiple sectors. Understanding and managing the inherent multi-objective tradeoffs for cities seeking to achieve simultaneous water, energy, and health goals in the context of a changing climate presents a multi-disciplinary challenge requiring physical and social sciences as well as co-production of new knowledge in close coordination with stakeholders.

Here we present a series of studies using physics-based modeling (the Weather Research and Forecasting Model coupled to an Urban Canopy Model enhanced with satellite-based landcover and vegetation information) to examine the fine-scale interactions among water, energy, and health sector outcomes subject to changing regional climate conditions and alternative urban development pathways. Using the major metropolitan areas of CA as a case study, we explore how future warming affects irrigation demands, air conditioning loads, and exposures to heat waves. We also examine how changes in vegetation and urban form interact with these larger scale effects, sometimes in unexpected ways. For instance, we find that the local-scale atmospheric cooling associated with reflective roof materials can substantially influence evapotranspiration from near-by irrigated landscapes, but larger-scale warming associated with global climate change does not have an equally proportionate inverse effect on evapotranspiration owing in part to larger-scale adjustments in absolute humidity. This work points to the value of resolving fine-scale physical processes in urban areas as part of a larger framework for examining multi-sector tradeoffs among realistic development pathways.