Alocação negociada de água do Sistema Hídrico Bálsamo: estudos complementares

Abstract

Water demands have been growing significantly in the last decades in Brazil, due to the process of economic development, increasing population contingents and the more and more grounded quantification of environmental necessities. On the other hand, the limited water availability is especially characterized by being sometimes inadequately distributed over time and geography to accommodate demands. This scenario leads to the necessity to implement water resources management instruments. Thus, the water allocation mechanisms can contribute to the more efficient application of these management instruments. In Alagoas, one of the examples of conflict over the use of water which was necessary to structure a negotiated allocation term occurred in the Balsamo reservoir. The current allocation term is valid until August 2021, however, this term has limitations regarding the restitution of the historical record of water volumes in the reservoir and the preparation of a water balance with more updated data. Given the importance of this reservoir for the participants of the allocation term, this paper aimed to prepare a hydrological study on the Balsam Water System in order to analyze the demand versus availability situation and support the negotiated allocation of water in the 2021/2022 period. This paper was supported by data acquisition about both the reservoir and the water allocation, as well as on hydrological data. Therefore, the series of affluent outflows was obtained and used in the preparation of the water balance, which is used to analyze the current scenario of the term and also analyze all other proposed scenarios. The results show that the reservoir does not have enough water to supply the current demands of the term, and that the current bottom outflow is very high. The best scenario was when the bottom outflow was reduced to the minimum recommended by SEMARH, but yet failures were still verified in some years. For this best scenario, the reservoir's guide curves were developed with the hydrological states, which can help in its operation. The worst scenario was verified when the irrigation perimeter demand was simulated alongside with the current demands, showing that there are no hydrological conditions for this new demand to be installed. For all situations, the failure percentage is high. Finally, new hydrological studies to verify the possibility of increase water storage in the reservoir are strongly recommended, such as the development of more updated depth-areavolume curves, since ANA recommends it when the reservoir completes 20 years of operation, which is almost completed.