Análise de alternativas para o uso das águas do projeto de integração do rio São Francisco - eixo norte, no Estado da Paraíba através de um modelo de otimização multiobjetivo.

Abstract

Being a limited and variable resource, many factors has pressed the water and its relationated sectors around the world, such as superexploration and aquifers‟ contamination. The world‟s demografic explosion has taken to an exponencial increase about hydrics demand at many society‟s segments, situation that requires the adoption of methods that optimize the water uses. The water‟s scarcity question is especially important to planet‟s regions like brazilian semiarid, that is strongly marked by long drought‟s periods, high evaporation rates, as well as high rains variability spacial and temporally and low precipitation‟s intensity. These atributes configure themselves as an important dificulty to economic and social region‟s development. In order to promote hydric‟s security for brazilian‟s semiarid, the Federal Government started, at 2006, the San Francisco‟s river integration project with the Northeast septentrional‟s basins. The mentionated project was divided in two axis: north and east. The first aims to attend the Sertão region and the second correspond to Borborema and Agreste regions attendance. At north axis, the prevision is to provide 2.7 m³/s of flow acessing the Piranhas-Açu river‟s basin by two areas: Piranhas‟ river high course region and Peixe‟s river subbasin. Each one will receive, respectively, 1.7 m³/s and 1.0 m³/s. An important condition was imposed by the basin‟s principal management instrument, that is 1.7 m³/s as residual flow to the neighboring state Rio Grande do Norte. So, from a multiobjective optimization model, based on Linear Programming, it has done a survey about the demands on urban supply and irrigation at whole study area to be used as inputs for the mentioned otimization model and to diagnosticate hydric system‟ potentialities, vulnerabilities and sustainability, from the water‟s transposition reinforcement. It were established four scenarios, that simulated: exactly the Hydric Resources Plan proposes (Scenario 1); as if all of external reinforcement flows was drained, exclusively, by the Piranha‟s river high course region (Scenario 2); as if the whole external contribution was drained by Peixe‟s river subbasin (Scenario 3); and the model left free to arbitrate the optimum exogenous flow values by the system (Scenario 4). The results pointed that the extreme scenarios (like the second and the third) are bad and hardly prejudice the deprecated basins, by recurrent events of fail at various consumers units. The basic scenario, although its greater balance relatively the extremes scenarios, is needy of pontuals adjustments. The fourth scenario, by its turn, presented very good results through no events of fail. However, it is needy a rigorous managements plans in a smaller temporal scale, to be demanded as an exogenous flow reinforcement only the necessary to that management horizont.