Interactions and feedbacks between water availability and domestic consumption in São Paulo Metropolitan Area

Water supply in large cities has challenged governments and water authorities because of the complexity involved in meeting water demands. The traditional challenges stem from the seasonality of precipitation and population growth. Although water resources management strategies assume potential scenarios for water demand growth to design water infrastructure, unexpected changes in the hydrological cycle may cause shocks to urban water supply systems and generate unanticipated patterns of consumption, such as occurred during the water crisis experienced by the São Paulo Metropolitan Area (SPMA) from 2014 to 2016. This work explores the coevolution of the coupled human-water system variables associated with the water supply system within the SPMA, from the late twentieth century to the present, to explain how water demand has influenced water availability, and vice-versa, in particular for the Cantareira Reservoir System. The challenges facing the human-water system in the region are of critical importance, given that it supplies water to more than 9 million people, and it supports economic activities that represent 12% of Brazil’s Gross Domestic Product. The analysis reveals that hydrological shifts are responsible for major structural transformations and they also have led to changes in domestic consumption. We conclude that modelling the interactions and feedbacks between water availability and consumption can provide more realistic storylines to implement strategies to address water scarcity than merely considering long-term demand scenarios, as it is normally done. In addition, policies implemented to promote water savings can have different responses at sub-regional scales and this can be explored also in the context of long-term scenarios.