Estudo para alocação ótima das águas de um sistema de reservatórios em série em paralelo, para usos e objetivos múltiplos, na bacia do rio Capibaribe, PE.

Abstract

Over the last few years, modern techniques of water resources management have been applied to problems of allocating scarce water resources among competitive water users at the northeast region of Brazil. They are applied at planning and operation of existing regional water infrastructures. Although their applications improve financial investments' efficiency and reservoir water allocation efficacy, their use is still considered modest. This work is concerned with reducing the gap between theoretical developments and practical analysis of reservoir operation systems through the use of combined simulation and optimization techniques. The operation of an integrated system of five reservoirs and an irrigated perimeter, located at the Capibaribe River basin in the Pernanbuco State, were used as a case to study. This river basin is of great socioeconomic importance to the region due its function in food production - fishing and agriculture -, reception and dilution of served waters, industrial uses and drinking water supply for human and animal uses. An optimization model, based on nonlinear programming, was used to maximize the net profit of the agricultural and extensive fishing system's management for several scenarios. Taking into account the operation strategy, which was obtained from the system optimization, the simulation model, based on a network flow model to allocate water according to priority scenarios for fulfillment of multi use demand requirements, was carried out. Concepts of reliability, resilience and vulnerability were used to compare different scenarios. At the optimization study, in which a monthly flow release for each reservoir was established to meet irrigation demands, was noticed that the Carpina reservoir, exclusively projected to flood protection, may regulate a significant water flow to reinforce the Recife urban water demand supply. Moreover, the optimization results have shown that it is possible to practice irrigated agriculture, supported by the reservoirs, in order to promote significant socioeconomic improvements at the region through generation of jobs and incomes. Only part of the available land for agriculture can be used for irrigation. The sustainability criterion, when applied to meeting irrigation water demand associated with its net profit and hierarchy performance indexes, can provide support to establish operation preference polices, once the agriculture is prone of risks due hydro-meteorological uncertainties. Although deterministic approach, where the future is known through planning scenarios, was used, this research revealed that the used methodological approach provided interesting decision support results to improve the operation of operations and the efficiency of water uses, mainly within regions subject to frequent water scarcity problems as the Capibaribe River basin.