CNH2-S: Water-mediated coupling of natural-human systems: drought and water allocation across spatial scales

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In many parts of the country, rivers are the primary water source for uses such as irrigation, recreation, cities, and power generation. Each water use has a different economic value. Also, the withdrawal of water from each river may follow a different institutional rule-system, for example private ownership of ‘water rights’ versus a public system of water allocation. Differences in the value of water combined with the local rule-system can lead to more- or less-productive outcomes, both economically and in terms of environmental sustainability. The effects of these differences are not well understood across scales and climate regimes, but it is known that any differences will be exacerbated during periods of water scarcity, e.g. droughts. To investigate these interactions, this research plan combines models of hydrology, infrastructure, and economics for different river systems and evaluates outcomes following a range of water allocation systems. The investigated water allocation systems span a spectrum ranging from more rigid systems based on established water rights, to those in which water goes to the highest-value uses. The modeling framework permits analyzing systems at different spatial scales and for rivers that primarily receive water from snowmelt versus rainfall. As populations grow and climate changes, the rules used to manage water will need to evolve and adapt, underscoring the importance of this research.The demand for water exceeds supply for many river systems in the drought-prone western U.S. This shortfall necessitates enhanced knowledge of the linkages and feedbacks between the natural variations in water availability and the human decisions that govern water movement in these stream-supplied systems. In these systems, water is used for agriculture, recreation, municipal uses, power generation, and other activities—each with a different valuation of water. Variations in the natural system, in particular drought, constrain the total amount of water available for human use. Water allocation rules and available water infrastructure connect the natural and human components. The proposed effort will advance knowledge of how hydrologic, climatic and economic processes jointly determine the value and allocation of water, across a range of drought intensities and spatial scales. Previous studies have shown that feedbacks and thresholds influence the coupling between hydrologic and societal systems. Yet, development and evaluation of advanced modeling approaches is needed to more fully understand the implications of human-natural interactions for different watersheds. The proposed research will develop a new system for modeling water-focused coupled human and natural systems that utilizes an operational water allocation model to link the hydrologic and economic components. This architecture will enable a direct evaluation of how two contrasting agent-based models of human behavior (microeconomic versus institutional-based rules) yield different outcomes across a range of conditions and scales. The growing demands for water and changing climate will require new ways of managing water, highlighting the importance of this research.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.