Understanding freshwater boundary exceedance through territorial, consumption, and trade perspectives
Freshwater withdrawals already exceed locally sustainable limits in many river basins worldwide, making freshwater boundary exceedance a widespread and growing challenge. The processes behind such exceedance are complex, arising from the interaction between local hydrological constraints and human activities that are increasingly organized through global production and consumption systems. Understanding freshwater boundary exceedance therefore requires the integration of multiple analytical perspectives.
In her thesis, Siyu Hou develops an integrated assessment framework to analyze freshwater boundary exceedance from territorial, consumption and trade perspectives. Central to the framework is a spatially and temporally explicit estimation of regional freshwater boundaries and their exceedance, based on an ensemble of global hydrological models and environmental flow requirement methods with reduced uncertainty. Building on this foundation, Hou examines the role of intra-annual water storage in alleviating seasonal exceedance, quantifies how national consumption drives grid-level freshwater boundary exceedance along global supply chains, and evaluates how interregional trade can exacerbate or mitigate regional water overuse. The proposed framework enables the consistent identification of exceedance hotspots, the attribution of exceedance to final demand, and the assessment of redistribution and mitigation pathways across regions.
Overall, this thesis provides a policy-relevant basis for linking local water management with demand-side actions and international supply chains to address freshwater scarcity.