Tracking grid-level freshwater boundary exceedance along global supply chains from consumption to impact

Consumption behaviors exert pressure on water resources both locally and globally through interconnected supply chains, hindering the achievement of Sustainable Development Goals (SDG) 6 (Clean water and sanitation) and 12 (Responsible consumption and production). However, it is challenging to link hotspots of water depletion across spatial scales to final consumption while reflecting intersectoral competition for water. Here, we estimate the global exceedance of regional freshwater boundaries (RFBs) due to human water withdrawal at a 5-arcmin grid scale using 2015 data, enabling the identification of hotspots across different spatial scales. To reduce uncertainty, we use average estimates from 15 global hydrological models and 5 environmental flow requirement methods. We further attribute the hotspots of exceedance to final consumption across 245 economies and 134 sectors via a multi-region input-output model, EMERGING. Our refined framework reveals previously unknown connections between regional hotspots and consumption through international trade. Notably, 24% of grid-level RFB exceedance (718.0 km³/yr; 95% confidence interval of 659.2-775.5 km³/yr) is outsourced through trade, with the largest flows (51.8 km³/yr; 95% confidence interval of 47.1-56.0 km³/yr) from water-stressed South-Central Asia to arid West Asia. The demand for cereals and other agricultural products dominates global consumption-based RFB exceedance (29.0%), while the exports of textiles and machinery and equipment exacerbate territorial exceedance in manufacturing hubs within emerging economies. Our analysis facilitates tracing global hotspots of water scarcity along the supply chain, and assigning responsibilities at finer scales.