Operação de reservatórios no contexto de transferência de água entre bacias hidrográficas

Abstract

Demands for water have increased substantially in recent decades due to the process of economic development and, when aligned with the spatial and temporal heterogeneity of rainfall, there is an increase in the risk of water scarcity in the regions. A solution traditionally used in semiarid regions has been the construction of reservoirs, however, in some situations the increase in demand exceeds the capacity to regulate the reservoirs and the water transfer inter basin is one of the possible solutions. Inter-basin water transfer projects are often expensive and require large infrastructure, therefore it is necessary to maximize their benefits and reduce their costs. In this context, the general objective of this study is the definition of technical criteria for the operation of water reservoirs in the context of water transfer between river basins, having as study area the Engenheiro Armando Ribeiro Gonçalves (ARG) reservoir in the state of Rio Grande do North, one of the reservoirs receiving water from the São Francisco River Integration Project (PISF). For this, there are two specific objectives: (i) to assess what future demand the reservoir is capable of meeting with the desired guarantees, considering the constant transposed flow; (ii) analyze when and how much to transfer PISF flow to minimize deficits in meeting the demands and the transferred volume. To achieve the objectives, a diagnostic scenario was analyzed, considering the constant flow of the PISF, and two other operation scenarios, with the optimization of the transferred flow based on the hydrological state of the reservoir in August, the first being transferring the water in all year and the other only in the rainy season (January to June). The results demonstrate that with a constant and permanent transfer of the exogenous flow from the PISF, the regularized flow of the ARG should increase in proportion to the volume transferred, and the increase in water availability results in a greater efficiency in the use of water from the reservoir, reducing the percentage of leakage and evaporation losses. It was also found that optimizing the transfer between basins based on the hydrological state of the reservoir, reduces the total volume of exogenous flow to be transferred, meeting the same demand, thus reducing the transfer costs that the State would have. And when comparing the transfer of water between basins throughout the year or just in the rainy season, the results were similar so that other factors should be used to assist in decision-making on when to transfer.