A comparison of five methods for reference evapotranspiration estimation in the West, Central, Eastern, and Southern Serbia

Abstract

Current climate conditions are often characterized by frequent water shortage during periods when plants are most sensitive to drought stress. Soil moisture plays a key role in pedogenic processes as well as in supplying plants with water. Therefore, it is necessary to determine crop water requirements for the irrigaton systems design and to organize adequate irrigation scheduling. The International Commission on Irrigation & Drainage (ICID) and the Food and Agriculture Organization of the UN (FAO) deem the PenmanMonteith method (FAO56-PM) as the most suitable for estimating reference evapotranspiration (ETO). Reference evapotranspiration depends on climate parameters such as air temperature and humidity, wind speed, and net radiation but also on geographical factors which describe the position of a certain site – latitude and elevation. However, due to the lack of climate data, alternative methods for calculating evapotranspiration in specific areas have been developed. This research aims to assess the possibility for the application of several ETo methods in the climate conditions of West, Central, Eastern, and Southern Serbia. Hargreaves, adjusted Hargreaves, Turc, and JensenHaise method were compared with the Penman-Monteith which was the referent method in this study. The meteorological data used in this research were monthly data (2000-2019) collected from 17 representative meteorological stations at a district scale. The methods were compared using mean absolute error (MAE). Turc and the adjusted Hargreaves method showed the lowest deviation from the reference (MAE=0.08 mm·day-1 , 0.14 mm·day-1 respectfully), while the Hargreaves method had shown the highest deviation (MAE=0.74 mm·day-1 ). Generally, the lowest deviation was obtained for the Bor, Mačva, and Kolubara districts (0.23 mm·day-1 , 0.26 mm·day-1 and 0.29 mm·day-1 respectively). Turc method had shown the lowest deviation in the Toplica district, while Hargreaves deviated the most. The results of the research indicate that the adjusted Hargreaves and Turc methods can be used to calculate ETo in case of missing data. The adjusted Hargreaves is the most reliable in almost all districts, although it utilizes only air temperature data.