Reference evapotranspiration in agro-climatic regions of India

The FAO-56 Penman–Monteith method for estimation of evapotranspiration provides accurate results under a wide range of climatic conditions and is considered as the standard method. If complete input data are unavailable, other methods can be used. This study evaluates the performance of these methods and compares them to results obtained from the standard method. Mean square error, mean absolute error, relative mean square error and relative mean absolute error are used to evaluate the performance of the methods for agro-climatic regions of India. Based on the results, recommended alternative methods for estimating evapotranspiration when full weather data are not available are provided for 14 agro-climatic regions of India.