Comparative study of reference crop evapotranspiration (ETo) by different energy based method with FAO 56 Penman-Monteith method and at New Delhi, India

摘要

The use of FAO 56 Penman-Monteith method for reference evapotranspiration (ETo) calculations to get crop water requirement has been recommended globally because it provides good results under wide range of climatic conditions. In absence of reliable data required for this method various other methods viz.FAO 24 Radiation, Priestley-Taylor, Blaney-Criddle, Hargreaves, Turc, Makkink and Pan Evaporation are used commonly. Main objective of this study is to evaluate performance of these seven commonly used energy based methods based on their daily ETo predictions compared to FAO 56 Penman-Monteith method predicted ETo and lysimetric ETc under prevailing climatic conditions of New Delhi. Use of Maize (Zea mays L.) crop lysimeter ET along with other meteorological parameters for seventeen carefully selected crop seasons ranging from 1976 to 2006 had done for performance evaluation. Statistical indicators used to evaluate performance were regression coefficient (R2), least root mean square difference (RMSD), mean bias error (MBE) and t-statistics. It can be concluded from the overall study that Priestley-Taylor and FAO 24 Blaney-Criddle method can be used for ETo predictions under wide range of climatic conditions when limited data is available or non reliability of data.