Aplicação de técnicas de redes neurais e modelagem atmosférica para elaboração de previsões de vazão na Bacia do Rio Grande (MG)

Abstract

The purpose of this study was to elaborate a ten-year runoff forecast model for the Furnas hydroelectric plant. The facility is located in the Rio Grande Basin in the state of Minas Gerais, Brazil. Artificial neural networks were used to determine natural flow as well as observed and predicted precipitation. The model was created using the Matlab® Neural Network Toolbox software, and the multi-layers perceptron (MLP) was trained with supervised learning algorithm Levenberg-Marquardt. Precipitation forecasts derived from ETA/ Centro de Previsão do Tempo e Estudos Climáticos (CPTEC) model, and both raw and mathematical adjusted data were used. Historical data was separated in three different periods in order to calibrate, validate and test the model. The first share was used for calibration, the second portion was used for validation and the third one to test the model. In each experiment the input data was modified; thus, in the first experiment, to forecast the ten day runoff, only the past runoff data was considered. In the second experiment, observed precipitation was added; and in the third one, the forecast precipitation was added. The rainfall-runoff modeling results did not show any significant improvement in the statistics when ETA input data is compared with the experiments that only used past information as input. Nevertheless, when forecast precipitation was used with mathematical adjustment, a mild improvement was shown for the statistics index and for the forecast hydrogram simulation. As a result, the modeling performance proposed in this study is similar to that found in conceptual models of rainfall-runoff type.