The Water Requirements to Feed a Megacity: Explorations for Mexico City with a Multi-regional Input–Output Database

Satisfying the demand for food in urbanizing economies increasingly requires complex supply chains spanning large distances and involving several industrial activities. The understanding of the ecological sustainability of these supply chains calls for establishing the links between natural resources, technologies for food production, inter-regional trade and food consumption in urban contexts. This paper explores these links for the case of water in the Mexican economy and the food demand in the Mexico City Metropolitan Area (MCMA), which houses 22 million people and generates a third of Mexico’s national output. This paper quantifies the demand for food in the MCMA, describes the national supply chain generating the output required to meet such demand and estimates its water requirements throughout the country. The method consists of an environmentally extended input–output computation with a multi-regional database describing the Mexican economy as of 2013. This paper finds that the Mexican supply chain satisfying the food demand in the MCMA requires 4.5[Formula: see text] per year of water nationally, 96% of which is utilized by agricultural activities outside the MCMA, even though they are responsible for less than 10% of the supply chain’s economic value. The MCMA is found to be a net importer of embedded water, while the major net exporters are the Mexican States of Hidalgo, Michoacán and Sinaloa. With these findings, this paper contributes to the understanding of the links between water, food and cities with methods and databases from input–output economics.