Water Supply Planning and Operation in the Metropolitan Region of Sao Paulo: Worst Drought in History, Conflicts, Response and Resilience

摘要

The Metropolitan Region of Sao Paulo, with 20.8 million inhabitants, has one of the largest water supply systems in the world. In 2013-2014 the region suffered from the worst drought in its history. The region's water supply is derived from eight partially interlinked systems. Cantareira is the largest, formed by an inter-basin water transfer and a set of reservoirs, serving about nine million inhabitants. With water levels below the minimum active storage in the Cantareira system, floating pumps, built specially for drought, are used to pump water from the dead storage. Other mitigation measures in the region include operational changes, pressure reduction at night and discounts as water saving incentives. Though projects for capacity expansion or resilience improvement are under study, they may conflict with the priorities of neighboring basins. One alternative for improving the Cantareira system that does not increase intake and treatment capacities is the additional transfer of up to 5 m~3/s of water from the Jaguari reservoir. Currently, this source of water is used for energy production and water supply to cities in the Paraiba Valley, and is the main source of water supply to the Metropolitan Region of Rio de Janeiro and its 12.1 million inhabitants. Different modeling techniques have been employed to optimize the operation of complex reservoir systems, particularly for dealing with droughts. SISAGUA is a MINLP optimization model that has been developed for the optimal planning and operation of water distribution systems with preemptive priorities: avoiding or minimizing shortages, optimizing storage distribution and minimizing operational costs. This paper presents an example of using the SISAGUA model as a decision support tool to evaluate the benefits and impacts of the proposed water transfer alternative.