Title: Evaluation of uncertainty in evapotranspiration values by FAO56-Penman-Monteith and Hargreaves-Samani methods
Authors: Hossein Talebmorad; Abdollah Ahmadnejad; Saeid Eslamian; Kaveh Ostad-Ali-Askari; Vijay P. Singh
Addresses: Department of Water Engineering, Isfahan University of Technology, Isfahan, Iran ' Department of Water Engineering, Isfahan University of Technology, Isfahan, Iran ' Department of Water Engineering, College of Agriculture, Isfahan University and Technology, Isfahan, 8415683111, Iran; Center of Excellence in Risk Management and Natural Hazards, Isfahan University and Technology, Isfahan, 8415683111, Iran ' Department of Civil Engineering, Isfahan (Khorasgan) Branch, Islamic Azad University, Isfahan, Iran ' Department of Biological and Agricultural Engineering and Zachry Department of Civil Engineering, Texas A and M University, 321 Scoates Hall, 2117 TAMU, College Station, Texas 77843-2117, USA
Abstract: Methods of calculating evapotranspiration are subject to uncertainty. It is important to evaluate their uncertainty. Using 54 years of data, this study evaluated the uncertainty values of monthly reference crop evapotranspiration calculated with the FAO-56 Penman-Monteith and Hargreaves-Samani methods. The objective of this study was to determine the range of variation in the results of each method. It was found that for both methods, the bandwidth uncertainty obtained with 95% confidence interval was more in warm months than in cold months, and the mean and variance by the Hargreaves-Samani method were always less than by the FAO-56 Penman-Monteith method. The uncertainty value of the FAO-56 Penman-Monteith method was more than of the Hargreaves-Samani method, because the number of parameters used in the FAO-56 method was more than in Hargreaves-Samani method which increased uncertainty resources.
Keywords: bootstrap; FAO-Penman-Monteith; Hargreaves-Samani; uncertainty.
DOI: 10.1504/IJHST.2020.106481
International Journal of Hydrology Science and Technology, 2020 Vol.10 No.2, pp.135 - 147
Received: 29 Jan 2018
Accepted: 10 Jun 2018
Published online: 09 Apr 2020 *