Avaliação do aumento das demandas na região receptora do Projeto de Integração do Rio São Francisco- Eixo Norte no Estado da Paraíba.

Abstract

The region of the Piranhas River - located in Paraiba's outback - recently went through one of the worst droughts that affected the Northeast of Brazil. Rural and urban populations have suffered from water shortages, with agricultural activities being suspended or limited. This region will benefit from the São Francisco River Integration Project (PISF, in Portuguese), with a contribution of 2.7 m³/s (steady flow) according to the Water Resources Plan for the Piancó-Piranhas-Açu Watershed (PRH-PPA, in Portuguese). Part of such contribution (1.0 m³/s) will meet water demands in Paraíba State while 1.7 m³/s will attend Rio Grande do Norte State. However, studies carried out by the PRH-PPA did not consider current water demands along the course of the Piranhas River or even the last drought that hit the region between 2012 to 2017. The objective of this study was to investigate whether the steady flow proposed by PRH-PPA is sufficient to meet the current water demands in the region of Piranhas River (in Paraíba State) and verify the possibility of increasing or decreasing these demands, considering critical hydroclimatic events (droughts and floods). To this end, first, we identified the main water demands and the water system infrastructure along the course of the Piranhas River, where the PISF waters arrive. Then, we defined two distinct scenarios. The first scenario (C1) intended to verify the fulfillment of the current water demands considering the exogenous flow from the PISF. The second scenario (C2) aimed to analyze the possibility of increasing (up to 100%) or decreasing the value of water demands in the São Gonçalo Irrigated Perimeter (PISG, in Portuguese) and of the diffuse areas along the course of Piranhas River and around São Gonçalo reservoir. We operated the water system with a multiobjective optimization model, whose main goal was to minimize the deficits in meeting water demands. To do that, the model took into account hydroclimatic processes (e.g., precipitation and flows) from 2000 to 2019. This period includes years with floods (2004 to 2009) and droughts (2012 to 2017). The results found that the steady flow of 1.0 m³/s of the PISF destined for the state of Paraíba is not sufficient to meet all water demands when considering the period of the last drought (2012 to 2017). It was possible to increase, by up to 100%, the water demand values of the PISG and diffuse areas; however, in the last drought, a decrease in water demand values was necessary. It is worth noting that such changes have prompted, on average, an annual water saving of more than 50 million cubic meters for the system. It being, therefore, correlated with the programmatic objectives of the ODS 2030 schedule, in relation to the item 06 – Drinking water and sanitation, and item 12 – Comsumption and sustainable production.