Análise de perdas de água por meio de otimização para o projeto de integração do rio São Francisco, eixo leste - bacia do rio Paraíba.

Abstract

On a recurrent water scarcity scenario in the northeastern semi-arid region due to the characteristic climatic causes of the region, the São Francisco River Integration Project (PISF) has brought hope to the population that needs these waters. In the State of Paraíba, through the east axis, the watershed of the Paraíba River receives the waters of transposition guaranteeing the water supply of the whole stretch of the river, as well as the four reservoirs of the series - Poções, Camalau, Boqueirão and Acauã – which are receivers of the project's water flow. The PISF was planned and executed through the construction of open channels, where the water is transported in direct contact with the external environment, leading to considerable water losses for the system. Due to the importance of this system for the region and the concern with its water management, a question is placed about how this water can be distributed an used when it reaches the Paraíba river basin in a way that water and financial losses can be minimized. Thus, the objective of this research is to study the behavior of water losses in transit along the river and by evaporation in the four reservoirs in series, which are recipients of the exogenous PISF flow, and calculate the costs of water losses for each scenario. For this, four scenarios were created taking into account the current form of transposition and scenarios with a proposal of a new pipeline to the ETA (Water Treatment Station) of Gravatá, located in the city of Queimadas, in Paraíba, transporting part of the flow of the integration project. Scenarios with the usual irrigated perimeters of the study area and also with irrigated area restrictions according to the ANA / AESA Joint Resolution No. 87 of November 5, 2018, were both considered. The scenarios were evaluated by means of a multiobjective optimization model based on Sucessive Linear Programming, created by Santos (2011), for a period of 6 years (2012 to 2017), which was marked by the strong drought in the region where the reservoirs reached a critical level of accumulation. The results showed that the demands of urban supply and irrigation were fully met in all scenarios. The maximum estimated flow rate for the Acauã-Araçagi integration channel is not sustainable, since its demand has not been fully met, and it overloads the entire system, especially the Acauã reservoir. It can be concluded that the scenarios that propose the transportation of part of the flow through a pipeline, showed greater efficiency in relation to lower water losses and consequently lower costs, with an economy in the range of 11.1 to 16.8 million Reais per year. The limitations imposed on the irrigated perimeters by the Joint Resolution ANA / AESA nº 87, did not bring success to their objectives of reducing the volume of water consumed, in the optimization process occurred the opposite, that resulted in greater water losses for the system, costing a further 3,1 million Reais per year.