Antensay Mekoya
At Tharandt, Germany for the summer half-year of 2004-2013, methods of estimation of Potential Evapo-Transpiration (PET) according to Haude, Wendling, and Penman and Class A pan evaporation (Ep) were compared with each other with respect to the reference evapo-transpiration (ETo) using box plot, trend check, linear regression model, and model evaluation statistics. Similarly, Class A pan coefficients (Kp) from the equation of Snyder and Frevert as well as a trial method of estimation of Kp were compared using box plots. For the calculation of ETo, calibrated values of as=0.014 and bs=0.50 were used. The total amount of summer half-year evaporation schemes were >459 mm while the precipitation was 478.8 mm; this implied that the climate water balance was close to zero. The result of the comparison showed that all the evaporation schemes had a very good correlation with the reference method and all were considered suitable methods of estimation of evaporation or evapo-transpiration. Comparatively, first to fourth ranks were given to PET and Ep defined by different researchers. Similarly, the trial method of estimation of Kp gave the most accurate estimates. As compared to Kp from the equation of Snyder, Kp from the equation of Frevert gave better estimates for fetch distances of 10 m, 20 m, 100 m, and 500 m.