Robustness and resilience have become central ideas in Sustainability Science in general and, more specifically, the study of social-ecological systems (SESs) and their capacity to cope with change (Anderies et al., 2013; Walker et al., 2009; Janssen et al., 2007; Janssen and Anderies, 2007; Walker et al., 2006; Adger et al., 2010; Eakin and Wehbe, 2009). Much of the development of these concepts has grown out of the natural resource management literature which has traditionally focused around smaller scale social-ecological systems including rangelands (e.g., Perrings and Walker, 1997; Janssen et al., 2004) (Anderies et al., 2006b; Walker et al., 2006), small-scale irrigation systems (Cifdaloz et al., 2010; Eakin, 2003), and shallow lakes (Carpenter et al., 1999b,a). Insights generated from these studies may not be easily generalizable to more pressing problems we face today because global social, economic, and climate change is increasing the spatial scale at which social groups interact with the environment and both the temporal and spatial scales at which these coupled human-environment systems experience shocks. Further, there has been less work on resilience and robustness of larger-scale SESs where large stocks of shared, human-made infrastructure play a critical roles in structuring interactions between humans and the environment. There are some examples of studies of the resilience of larger systems, e.g. regional-scale systems (Anderies, 2006; Anderies et al., 2006a; Anderies, 2005), but there is a need to more systematically explore modern contexts where multiple interdependent water, energy, transportation, food, and settlement infrastructures interact. Such an exploration calls for expanding the SES concept, which does not typically incorporate large scale human-made infrastructure, to encompass the concept of coupled infrastructure systems (CIS) (Anderies et al., 2016; Anderies, 2014; Anderies et al., 2013). 

Here, we contribute to filling this gap through an analysis of the regional-scale CIS comprised of the Phoenix and Tuscon Metropolitan areas and surrounding agricultural areas within the Central Arizona Project (CAP) service area (see below), and the water delivery infrastructure that connects these areas to the Colorado River Basin.