Optimal design of water allocation networks in highly altered basins: the guandu river case, Brazil.

Abstract

Water scarcity is present in many regions around the world. Factors affecting water availability include, but are not limited to, population growth, resource depletion, alteration of natural ecosystems, and climate change. Said this, the study of water allocation networks is taking an important role worldwide due to the importance of the liquid for the development of human activities. The application of optimization models represents an opportunity to create new approaches to water resources management and to guarantee the sustainability of natural resources. Many previous optimization models focused on studying the hydraulic elements of the water allocation networks (e.g., pipes, pumps, and storage) to maximize economic profit or minimize distribution costs. These past approaches often neglected the hydrological aspects which describe the behavior of natural ecosystems. The aim of this research is to develop a multiobjective optimization model that incorporates parameters and equations for hydrological processes for the design of water allocation networks in highly altered basins. The model is applied to the Guandu basin in Brazil, one of the most altered watersheds worldwide (receiving 96% of its volume from surrounding basins). This basin supplies 9 million inhabitants of the Rio de Janeiro metropolitan area. Simultaneously, this basin is characterized by a strong relationship with the energy sector, i.e., around 25 % of the city's energy is produced in the basin through a hydropower complex. The results show that water transfer can be optimized by integrating water storage and reuse/recycling elements to satisfy water demands throughout the year. Also, through optimal allocation networks, it is possible to avoid saline intrusion downstream of the Guandu river, even if there is a reduction in the volume transferred from nearby basins. The developed tool is a highly feasible option for decision-making in water resources planning and management.