Abstract:
Because it produces 15% of the water vapour in the atmosphere, evapotranspiration is a crucial
step in the water cycle. In order to allocate water effectively, manage irrigation, assess the
effects of shifting land use on water yield, evaluate the environment, and establish best
management practises to safeguard surface and groundwater quantity and quality, accurate
quantification of ET is essential. The Penman method was modified in 1965 by Monteith through
incorporating the aerodynamic resistance and surface resistance factors, leading to the
generation of the well-known Penman-Monteith method, which can be directly used to calculate
ET. In this research work two evapotranspiration models namely one Modified Optimized
Temesgen Melese ET-TM and two Modified Hargreaves methods of ET estimation models were
compared with the Penman Monteith method interms of statistical parameter and model
performance parameters. In this research work the Modified Optimized Temesgen Melese ET TM ET estimation models have shown good model performance in terms of R2
slope and
intercept as compared with the. Penman-Monteith method.But the Hargreaves ET estimation
method was show satisfactory model performance for Debrabirhan and Mekelle stations, poor
value for Addis Ababa and good model performance for Dessie. Moreover all the other
statistical parameters such as CE, RMSE and MPE have also shown in the results. Modified
Optimized Temesgen Melese method should be compared with Penmann-Montieth (PM) method
which is the standard ET estimation method
