Document Type : Research Paper
Authors
1 گروه عمران - آب دانشکده فنی دانشگاه آزاد اراک ایران
2 Assistant Professor, Department of Civil Engineering, Arak Branch, Islamic Azad University, Arak, Iran.
3 Assistant Professor, Department of Water Engineering, Urmia University, Urmia, Iran.
Abstract
Evaporation is one of the main components of the hydrological cycle. Accurate estimation and prediction of this phenomenon plays an important role in irrigation management. In this study, using the values of evaporation data from the pan in 31 evaporating stations of the provincial centers of the country in the statistical period of 1996-2014, the trend of monthly changes of evaporation from the pan was investigated using the age slope estimator. For this purpose, in order to prepare the data, unstable factors were eliminated and the basic assumptions of time series analysis were provided. In order to remove unstable factors from the series, first these factors were identified, then they were removed from the series. The rest of the series is static and represents the random component of the model. SARIMA, ARMA, BL and FARIMA time series models were reviewed and their results were compared to model and predict monthly evaporation values from the pan of evaporator stations. Finally, the accuracy of each of these models was evaluated using Mann-Kendall test. The results of the trend of changes in the monthly scale showed an increase in the trend of evaporation data from the pan in the eastern half and a decrease in the western half of the country. The results of the root mean square error (RMSE) evaluation criteria showed that SARIMA, BL, ARMA and FARIMA models with values of 20.61, 168.118, 02.2182 and 223.47, respectively, have the best performance in modeling evaporation from the pan.
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