A exploração de um sistema de reservatórios: uma análise otimizada dos usos e objetos múltiplos na bacia do rio Capibaribe-PE.

Abstract

Potable water is a finite natural resource, which per capita usable amount decreases each day as world population grows and water sources are reduced. The use of planning mathematical models for the analysis of water resources systems has developed since the 60s. Most of the revised papers shows that there are many techniques which can be applied to the analysis of reservoir systems. However, there is not a final methodology to be used in all situations, which requires each case to be verified so the most adequate methodology can be found for it. This work intends to combine optimization and simulation techniques to define the planning and operation of water use on an integrated water resources system formed by 5 reservoirs - Jucazinho, Carpina, Tapacurá, Goitá, and Várzea do Una, located at the Capibaribe river basin, to supply the demands of human need, ecological discharge, irrigation, fishery, and flooding control, some of which are conflicting. Optimization and simulation planning scenarios were created to provide a good evaluation on how the system behaves, and with the objective to obtain suggestions for operational practices concerning the use of water availability. The optimization model used was based on a linear programming for a period of 10 (ten) consecutive years, with the objective to find an optimal solution for the system operation. Acquanet was the simulation model used with the objective to analyse the system for 22 years, using operational strategies coming from optimization. Results showed that it is possible to make other uses for the Carpina and Goitá reservoirs, originally built to control floodings. Irrigation and fishery as possible uses to be implemented, strengthen local businesses, and generate work and income. The results obtained when the ecological discharges were not fixed, but calculated by methods based on discharge registers showed that human need demands as well as ecological ones were completely fulfilled, providing an even greater availability of water in the reservoirs for irrigated agricultural activities. This study included the calculation of the reservoirs sustainability index, resilience and vulnerability, to allow the evaluation of water availability and system performance for each of the environments. Indexes to evaluate the performance of irrigated areas were calculated besides those other indexes. Results obtained from the various scenarios verify adequation and applicationability of the models to the multi-reservoir system, with multiple uses and objectives. The use of the models and the analysis of the group of indexes permit the adoption of practices for the management of the operation of reservoirs which present problems like water deficit and conflicts on the use of water.