ANALYSIS OF DIFFERENT REFERENCE EVAPOTRANSPIRATION METHODS IN SOUTH-EASTERN SERBIA

Abstract

Evapotranspiration is an important component of hydrological balance, and it represents a complex process of water evaporation form water bodies, soil and plants. The Food and Agriculture Organization of the UN proposed the Penman-Monteith equation as the most reliable method for calculating reference evapotranspiration. However, the application of Penman-Monteith is often limited in many regions, due to the requirement for a large amount of meteorological data. In such circumstances, it is necessary to identify an alternative method with similar efficiency. The goal of the paper is to define the best method, out of the Hargreaves, adjusted Hargreaves, Thornthwaite, calibrated Thornthwaite and adjusted Thornthwaite methods, which gives results similar to those of the Penman-Monteith method (but does not require a wide range of input data) for South-eastern Serbia. South-eastern Serbia was observed through Nis, Vranje and Dimitrovgrad stations, for the period 1989-2018. In order to define the best match with the Penman�Monteith method, statistical indicators were used: mean bias error � MBE, mean absolute error � MAE and root mean square error � RMSE. The final results of the indicators showed that, from all the analyzed methods, the adjusted Hargreaves method matches the Penman-Monteith method best, i.e. the adjusted Hargreaves method has the following values: MBE = -0.076, MAE = 0.225 and RMSE = 0.318, which are the lowest values, compared to other methods.