Assessment of reference evapotranspiration (ETo) methods under data scarcity scenarios (case study: Kermanshah)

Document Type : Original Article

Authors

Irrigation and drainage Dep., Aburaihan campus, University of Tehran

10.22125/iwe.2018.93443

Abstract

Many studies have evaluated different methods to estimate evapotranspiration as one of the most important parameters of water resources and irrigation management in recent decades. The result of these studies confirmed that the FAO Penman-Monteith (PM) is the standard method for calculating reference evapotranspiration. This method requires numerous meteorological data such as air temperature, solar radiation, air humidity and wind speed. Since in most regions of Iran, the weather station is not available or all of the meteorological data is not measured, hence investigation of methods to estimate evapotranspiration is necessary in these situations. In this study, data scarcity scenarios, (when one, two and three meteorological variables are not available: relative humidity, wind speed and sunshine hours), have been evaluated. Also, the FAO-56 manual recommended methods (PM-R), PM-CI (computation-then-interpolation), PM-IC (interpolation-then-calculation) and Hargreaves–Samani (HS) were compared using different statistical parameters. The results showed that in absence of wind speed (when one or two meteorological parameters are not available), the PM-IC method estimated more accurately (R2> 0.96), while precision of the PM-R method is higher (R2 ≈ 0.99) in absence of other weather parameters (sunshine hours and air humidity). Also, the HS method, temperature-based methods (absence of three meteorological data), provided a more acceptable result (PBIAS = -3.091, ME = -0.156, MAE = 0.337) than other methods.

Keywords

Irrigation and Water Engineering
Volume 9, Issue 1 - Serial Number 33
January 2019
Pages 183-197

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