Evaluation of Hargreaves method for calculation of reference evapotranspiration in selected stations of Slovakia

Evapotranspiration has an essential role in the hydrological cycle by affecting the volume of surface runoff and the amount of available water on the land. It is an input parameter for many hydrological models based on water balance; it is an important parameter for calculating agricultural land irrigation and water management. In the current hydrology, the role of evapotranspiration is increasingly important because of global warming and the increasing occurrence of drought. Many methods for evaluating drought are based on the value of Actual evapotranspiration, which is not directly measured, and data about this variable are not available from a national database. For this reason, the Reference evapotranspiration, which can be calculated from more frequently measured meteorological variables, is gaining in importance. FAO Penman-Monteith (P-M) method is a method for the calculation of Reference Evapotranspiration recommended by many international organizations and worldwide used by researchers like reference method in research. However, the high demand for required P-M method input meteorological parameters caused its difficult usability in the case of research covering large regions. For this reason, the methods less demanding on inputs for reference evapotranspiration calculation were derived. The accuracy of this method is necessary to verify in local conditions.

This research aims to describe the spatial and temporal distribution of reference evapotranspiration and evaluate the Hargreaves method accuracy in the selected stations of Slovakia. The punctuality of the Hargreaves method showed a positive correlation with the increasing altitude of the Climatological station. The correlation coefficient of P-M and Hargreaves reaches more accuracy in comparing monthly values for all Climatological stations. The results bring information about the usability of the Hargreaves method in different conditions, which is mainly essential for hydrological modelling.

This publication is the result of the project implementation: „Scientific support of climate change adaptation in agriculture and mitigation of soil degradation” (ITMS2014+ 313011W580) supported by
the Integrated Infrastructure Operational Programme funded by the ERDF; and was supported by the Slovak Research and Development Agency under Contract No. APVV-18-0347; and grant number VEGA 1/0782/21.