Assessing the Roles of Regional Climate Uncertainty, Policy, and Economics on Future Risks to Water Stress: A Large-Ensemble Pilot Case for Southeast Asia

The fate of natural and managed water resources is controlled to varying degrees by interlinked energy, agricultural, and environmental systems, as well as the hydro-climate cycles. The need for risk-based assessments of impacts and adaptation to regional change calls for likelihood quantification of outcomes via the representation of uncertainty - to the fullest extent possible. A hybrid approach of the MIT Integrated Global System Model (IGSM) framework provides probabilistic projections of regional climate change - generated in tandem with consistent socio-economic projections. A Water Resources System (WRS) then tracks water allocation and availability across these competing demands. As such, the IGSM-WRS is an integrated tool that provides quantitative insights on the risks and sustainability of water resources over large river basins. This pilot project focuses the IGSM-WRS on Southeast Asia (Figure 1). This region presents exceptional challenges toward sustainable water resources given its texture of basins that traverse and interconnect developing nations as well as large, ascending economies and populations - such as China and India. We employ the IGSM-WRS in a large ensemble of outcomes spanning hydro-climatic, economic, and policy uncertainties. For computational efficiency, a Gaussian Quadrature procedure sub-samples these outcomes (Figure 2). The IGSM-WRS impacts are quantified through frequency distributions of water stress changes. The results allow for interpretation of: the effects of policy measures; impacts on food production; and the value of design flexibility of infrastructure/institutions. An area of model development and exploration is the feedback of water-stress shocks to economic activity (i.e. GDP and land use). We discuss these further results (where possible) as well as other efforts to refine: uncertainty methods, greater basin-level and climate detail, and process-level representation glacial melt-water sources. Figure 1

Figure 2