Estimation of Crop Reference Evapotranspiration for Remehue-Osorno, X Region

Abstract

In order to obtain reliable daily estimates of crop reference evapotranspiration (ET₀) for Remehue-Osorno, a study was carried out to analyze four calculation procedures of daily mean vapor pressure deficit (VPD) and its impact on the Penman-Monteith (PM) ET₀. Moreover, an adjustment of the Hargreaves-Samani (HS) equation coefficients was performed. Results indicated that the VPD procedure which makes use of maximum and minimum relative humidity associated with saturation vapor pressure at minimum and maximum air temperature, respectively, provides the most accurate VPD estimates with minimal effects on ET₀ estimates. The locally adjusted HS equation that uses the observed solar radiation provides reliable and robust daily ET₀ estimates similar to those obtained by the PM model. It was also found that previous studies on evapotranspiration for Remehue-Osorno would overpredict monthly ET₀ estimates.