Integrating Economic Models with Biophysical Models in the Willamette Water 2100 Project

This paper highlights the human system modeling components for Willamette Water 2100, a comprehensive, highly integrated study of hydrological, ecological, and human factors affecting water scarcity in the Willamette River Basin (WRB). The project is developing a spatiotemporal simulation model to predict future trajectories of water scarcity, and to evaluate mitigation policies. Economic models of land use and water use are the main human system models in WW2100. Water scarcity depends on both supply and demand for water, and varies greatly across time and space (Jaeger et al., 2013). Thus, the locations of human water use can have enormous influence on where and when water is used, and hence where water scarcity may arise. Modeling the locations of human uses of water (e.g., urban versus agricultural) as well as human values and choices, are the principal quantitative ways that social science can contribute to research of this kind. Our models are empirically-based models of human resource allocation. Each model reflects private behavior (choices by households, farms, firms), institutions (property rights, laws, markets, regulations), public infrastructure (dams, canals, highways), and also 'external drivers' that influence the local economy (migration, population growth, national markets and policies). This paper describes the main model components, emphasizing similarities between human and biophysical components of the overall project, and the model's linkages and feedbacks relevant to our predictions of changes in water scarcity between now and 2100. Results presented include new insights from individual model components as well as available results from the integrated system model. Issues include water scarcity and water quality (temperature) for out-of-stream and instream uses, the impact of urban expansion on water use and potential flood damage. Changes in timing and variability of spring discharge with climate change, as well as changes in human uses of lands in flood-prone areas, will alter the tradeoff for the optimal use of reservoir storage capacity. We emphasize three concepts: i) institutions, ii) scarcity, and iii) the role of social science in projects of this kind. Institutions represent the main instrument or tool that humans use to influence how resources are used, to reduce waste, promote efficiency, and foster predictability. Water scarcity when defined in human normative terms. The concept provides a lens through which to recognize the wide range of ways that water scarcity can arise and persist even in water-abundant settings. We conclude with observations about the role of social science in research on biophysical and human systems. Reference Jaeger, W.K., et al., 2013. Toward a formal definition of water scarcity in natural-human systems. Water Resources Research, Volume 49. Published online: 8 JUL 2013 | DOI: 10.1002/wrcr.20249