Processo de concessão de outorgas em sistemas hídricos superficiais controlados por reservatórios

Abstract

The increasing demand for water resources associated with decreasing water quality leads to a scenario of conflict over its use. In this context, the Water Law (Law 9.433/1997) introduces the granting of the right to use water resources as an important tool to support water resource management. Despite being provided for in national and state legislation and decrees, the granting process is complex in its implementation and administration. In order to assist in this process, methodologies have been developed for determining the maximum grantable flow, which are generally based on two principles: reference flow and pre-determined failure quantity, which have the disadvantage of tending to limit the growth of water resource uses most of the time. Thus, in order to efficiently meet water needs, a methodology has been developed to support the granting process in water systems controlled by reservoirs. This methodology is based on the operation of the water system, either in isolation and/or integrated, evaluating the impact of the insertion of a new grant through performance indicators of demand fulfillment and water systems. The methodology was applied in the Paraíba river basin, considering reservoirs with a capacity greater than or equal to 10 million cubic meters. Ten scenarios for the operation of the water system were designed, which present variations in the exogenous flow of the São Francisco River Integration Project (average, minimum, and real flows), in the system layout (integrated and isolated), and in temporality (current and future grants for a period of 20 years). A simulation tool was used, which allowed the insertion of the proposed water system in both isolated and integrated forms, defining the reliability indicator and water losses to evaluate the proposed scenarios. The results showed that the proposed methodology is capable of granting licenses, minimizing specific water deficit problems and water use conflicts. The use of a simulation model based on flow networks allowed the incorporation of priorities for meeting various uses and allowed the system to operate in different configurations, making it possible to analyze the impact of granting a license both upstream and downstream. With the results obtained in the case study, it was observed that isolated systems showed lower water losses for the system, allowing an increase in the number of licenses granted. It is found that the proposed methodology enabled the granting of more licenses compared to the maximum grantable flow, and also indicated that the reference flow used for the São Salvador reservoir is higher than its capacity to meet demand.