Evolving connectionist systems (ECoSs): a new approach for modeling daily reference evapotranspiration (ET).

Over the last few years, the uses of artificial intelligence techniques (AI) for modeling daily reference evapotranspiration (ET) have become more popular and a considerable amount of models were successfully applied to the problem. Therefore, in the present paper, we propose a new evolving connectionist (ECoS) approaches for modeling daily reference evapotranspiration (ET) in the Mediterranean region of Algeria. Three ECoS models, namely, (i) the off-line dynamic evolving neural-fuzzy inference system called DEFNIS_OF, (ii) the on-line dynamic evolving neural-fuzzy inference system called DEFNIS_ON, and (iii) the evolving fuzzy neural network called (EFuNN), were statistically compared using the root mean square error (RMSE), the mean absolute error (MAE), the coefficient of correlation (R), and the Nash-Sutcliffe efficiency (NSE) indexes. The proposed approaches were applied for modeling daily ET using climatic variables from two weather stations: Algiers and Skikda, Algeria. Five well-known climatic variables were selected as inputs: daily maximum and minimum air temperatures (T and T), daily wind speed (W), daily relative humidity (R), and daily sunshine hours (SH). The effect of combining several climatic variables as inputs was evaluated, and at least six scenarios were developed and compared. The proposed ECoS models were compared against the reference Penman-Monteith model referred as "FAO-56 PM". According to the results obtained, the DEFNIS_OF1 model having T, T, W, RH, and SH as inputs, is the best model, followed by the DEFNIS_ON1, and the EFuNN1 is the worst model. The R and NSE value calculated for the testing dataset for the Algiers and Skikda stations were (0.954, 0.910) and (0.954, 0.905), respectively. While both DEFNIS_OF1 and DEFNIS_ON1 showed good accuracy and high performances, the EFuNN1 was less accurate.