Prediction of Monthly Streamflow Using Shannon Entropy and Wavelet Theory Approaches (Case study: Maroon River)

River flow is one of the most important components of the hydrological cycle, which depends on several climatic factors and its accurate estimation is used in various fields of water resources management. Therefore, in the present study, random forest (RF) and support vector machine (SVM) models were used to predict the monthly streamflow of the Maroon River in the period of 1981- 2017. One of the important steps in the application of artificial intelligence models is the definition of input patterns and determining the effective variables in the modeling process. The Shannon entropy method was used to select the most efficient inputs among precipitation, evaporation, and minimum, maximum, and average temperatures. The results showed that the total weight of precipitation and evaporation was more than 85 percent. In the next step, three different structures were developed for modeling. In the first case, climate-based patterns were defined that used meteorological data as input. In the second case, nonlinear periodicity was added to the climate-based patterns, and in the third case, the climate-based input data were decomposed using five mother wavelet functions, and W-RF and W-SVM hybrid models were created. The performance evaluation of the standalone RF and SVM models showed that by considering the periodic term, the accuracy is somewhat increased compared to the climate-based inputs, but the analysis of the data with wavelet theory significantly reduced the modeling error. In the meantime, the performance of the two models W-RF and W-SVM was very close to each other, but according to the violin plot, the W-SVM model is suggested as the most suitable option for predicting the monthly streamflow of the Maroon River.