Estimating reference evapotranspiration using the Hargreaves - Samani formula for end-user applications

Abstract

Reference evapotranspiration is one of the main geophysical parameters, the reliable assessment of which is important in irrigation water management, planning, distribution and regulation of water resources. The Food and Agriculture Organization of the United Nations recommends using the Penman-Monteith formula to estimate ETo. However, its’ application by end-users is limited since the formula requires several parameters which are often missing. In such cases, it recommends the Hagreaves-Samani formula. In this study, the reference evapotranspiration is estimated as the case study for Uzbekistan applying both, the Penman - Monteith and the Hargreaves - Samani methods. Data used is taken from 13 state climate stations of Uzbekistan. The results of the study indicate that under data-scarce conditions, the Hargreaves – Samani formula, can be recommended for end-user applications, after the adjustment to local conditions, in order to determine the water requirements of crops and irrigation scheduling.