Water conservation policies under drought conditions: the Sao Paulo Metropolitan Area case study

Abstract:

Water supply augmentation and water demand management are two possible responses to drought events in urban centers. While the former refers to the possibility to increase water availability, the later focuses on reducing consumption through water conservation policies. Between 2013 and 2015, the São Paulo Metropolitan Area was affected by the most severe hydrological drought since 1980s when the Cantareira Reservoir System, which supplies water to more than 8 million people, reached the dead pool level. Although the drought management effectively avoided the collapse of the supply system, it is still unclear how each group responded to demand management strategies. The aim of this work is to analyze two policies implemented during the 2013-2015 water crisis, the bonus tariff, which provides discounts in water bills for consumers who voluntarily reduced their consumption, and the contingency tariff, which increases water bills for consumers who increased their consumption. In addition, we assess whether the population changed their consumption after the crisis or if their consumption rebounded to pre-drought and pre-demand management levels. We clustered the numerous supply areas into 51 larger units, according to the water source, elevation, income and pipeline connection, to perform statistical tests to identify breakpoints in consumption trends, assess policy effectiveness, test for causality relationships and the rebound effect. The results demonstrate that communities have particular feedbacks at different intensities for each policy. Therefore, the comprehension of these responses during and after droughts might help decision makers optimize the demand management under extreme drought conditions.