ANN-based PCA to predict evapotranspiration: a case study in India

The Penman-Monteith evapotranspiration (ET) model has superior predictive ability than the other methods, but it is challenging to apply for several Indian stations, owing to the need for a large number of climatic variables. The study investigated an artificial neural network (ANN) model for calculating ET for various agro-climatic regions of India. Sensitivity analysis showed that the overall average change in ET0 values for 25% change in the climatic variables were 18, 16, 14, 7, 5, and 4%, respectively, for T-max, RHmean, R-n, wind speed, T-min, and sunshine hours. The dominant climatic variables were identified from the principal component analysis (PCA) and ET0 was computed using an ANN with dominant climatic variables. The ANN architecture with backpropagation technique had one hidden layer and neurons ranging from 10 to 30 for all climatic variables and from 5 to 10 for PCA variables. The new ET models were statistically compared with Penman-Monteith ET estimate, and found reliable. PCA variables guaranteed an estimate of ET0 accounting for 98% of the variability. The average values of coefficient of determination, standard error of estimate, and percentage efficiency were observed as 0.96, 0.24, and 94%, respectively.