International Journal of Plant & Soil Science

The determination of reference evaporation method in a region with different simple or complex equations requires a wide range of meteorological data. It is difficult task particularly in regions with lacking data collection facilities. One of the common methods for this purpose is the use of lysimeters. In the present study, daily lysimeteric data for two years (2012 to 2013) from April to July in each year were used to evaluate nine different grass evapotranspiration models including FAO-56 Penman–Monteith, Penman-Kimberly 1996, FAO-Penman equation, Blaney–Criddle, FAO-24 Radiation, Makkink, Turc, Priestley–Taylor, and Hargreaves in Kermanshah western part of Iran with semi-arid climate. Finally, the values of RMSE indicate that, the FAO - Penman-Monteith, Makkink and Hargreaves and Samani were found to be the most appropriate models for the studied region. Penman-Kimberly and FAO-Penman methods had the worst results among the studied models. FAO- Penman-Monteith, Makkink and Hargreaves-Samani methods recommended for reference evaporation estimation, irrigation planning and scheduling, dams reservoirs design and different surface or pressurized irrigation projects water requirement application under different crop patterns in Kermanshah region, while weather, radiation and temperature data have been available. Based on RMSE values, the FAO- Penman-Monteith, Makkink and Hargreaves & Samani methods estimated the lysimeter reference evaporation values most closely and Penman-Kimberly and FAO-Penman methods had the worst results in the region.