Evaluation of FAO WaPOR product and PYSEBAL algorithm in estimating The amount of water consumed

Document Type : Research Paper


1 Department of Water Engineering, Faculty of Agricultural and Natural Resources, Imam Khomeini International University, Qazvin, Iran

2 Water Eng. and Science Dept., Imam Khomeini International University


Evapotranspiration is an essential component of the hydrological cycle and a key element of water resources management, especially in arid and semi-arid regions. Today, remote sensing has made it possible to estimate evapotranspiration on a large scale, so the use of this technology can be considered a promising method order to overcome the spatial variation of evapotranspiration. In this study, daily, monthly and seasonal changes of evapotranspiration using WaPOR product and PYSEBAL algorithm in Qazvin from 2015 to 2021 were investigated. The results obtained in this study were compared with the experimental method of Hargreaves and Samani (1985) which is the best experimental method in the region. Examination of the mean deviation of the estimated values from the values observed in the daily scale in both models shows that the PYSEBAL has less difference and in most cases is close to the values obtained from the experimental method. While in WaPOR product, it was associated with underestimation compared to the experimental method during almost the entire period under study. Also, although WaPOR has been able to show a fair amount of seasonal ET changes it does not have good accuracy, so this product has acceptable accuracy in spring and summer, but in autumn and winter, these details are not well observed. Finally, WaPOR products with relatively good spatial resolution can provide water requirements for any time period. WaPOR products can play an important role in water resources management, determining the required water consumption. But PYSEBAL algorithm produces more accurate results than the WaPOR product. if studies to estimate the amount of evapotranspiration for large areas and long time periods are considered, the use of WaPOR products due to the lack of data vacuum can play an important role in managing water resources and water needs of the region or basin.


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