ESTIMATION AND COMPARISON OF POTENTIAL EVAPOTRANSPIRATION BASED ON DAILY AND MONTHLY DATA FROM SPERCHIOS VALLEY IN CENTRAL GREECE

There is no golden rule concerning the optimal equations to estimate reference potential evapotranspiration (PETref) under various climates because even in the same climatic type, different studies have produced mixed results in relation to the performance of the empirical PETref equations. Knowledge of reference potential evapotranspiration (PETref) conditions is important for a number of vegetation and hydrological related applications. Direct estimations of PETref are difficult and require sophisticated instrumentation and methods. The equations of estimating potential evapotranspiration require several meteorological variables (e.g. solar radiation, wind speed), which most of the times are rarely available in daily values for the Greek meteorological stations. In the current research there is an attempt to estimate the potential evapotranspiration with EmPEst software which includes 13 different approaches, using daily and monthly data of the meteorological station of Lamia which is located within Sperchios river valley in central Greece. Finally, by the use of the statistical indicators that occur as an output from the software, there is a comparison and analysis of the exported results. The differentiations of the results showed which PET methods and series data (daily - monthly) were more suitable for the estimation of PET in the area of research.