Urbanization and climate change are significant planning challenges for water supply management. Adaptive management and flexible infrastructure have been proposed to address this challenge; however, standard evaluation methods use a narrow set of assumptions of societal response to changing conditions, limiting our ability to assess the adaptive or flexible strategies that must be executed over time. To improve evaluation of water supply reliability alternatives, an approach that incorporates the human agency inherent in water management is needed. The first objective of this study is to develop a coupled conceptual model of the system that illuminates the dynamic interactions between the biophysical and institutional systems. The second is to build a partially coupled quantitative model that can be used to test alternative structures of the policymaking process. Las Vegas is used as a test case due the water management changes observed in response to rapid population growth and drought.
Las Vegas water management responded to three key events during the study period: creation of a regional utility, drought, and the financial crisis. The decision-making processes initiated by these three events were analyzed using the socio-ecological systems framework . This analysis, along with data on the biophysical structure, informed the development of a conceptual model incorporating the interactions between the biophysical system and the governing institutions. All aspects of the conceptual model, except the policy subsystem, were then quantified in a system dynamics model in Vensim software. After testing the model against historic reference modes, I tested the system’s performance under set of scenarios of hydrologic and demand futures. I then tested the performance of policies, identified by the local utility, under these conditions.
The conceptual model developed of Las Vegas water management consists of five coupled submodules: water supply, water demand, finances, public perception, and policymaking process. From this base, I developed a draft quantified model; the policy process subsystem was included to facilitate testing of multiple structures to enhance the robustness of the coupled model. The model performed well under reproduction of observed trends in variables such as reservoir levels, water demand, and population. The scenario analysis showed that low reliability under plausible future conditions if no action is taken. The policy analysis demonstrates the potential improvements and the sensitivity of system performance to the decision rules used to trigger policy options. Next steps include testing alternative structures of the policy process and fully coupling the model.
 Ostrom E. (2009). A general framework for analyzing sustainability of social-ecological systems. Science, 325(5939), 419–22. doi:10.1126/science.1172133.
Wei Liu and Brian Fath, Risk, Policy and Vulnerability, IIASA
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Last edited: 29 September 2015
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