Pan evaporation modeling using four different heuristic approaches

- The effects of climatic factors on pan evaporation are analyzed.
- FG, LSSVR, M5Tree, MARS and MLR models are used for predicting Ep.
- Cross validation method is used for evaluate the model performances.

Evaporation plays important roles in regional water resources management, climate change and agricultural production. This study investigates the abilities of fuzzy genetic (FG), least square support vector regression (LSSVR), multivariate adaptive regression spline (MARS), M5 model tree (M5Tree) and multiple linear regression (MLR) in estimating daily pan evaporation (Ep). Daily climatic data, air temperature (Ta), surface temperature (Ts), wind speed (Ws), relative humidity (RH) and sunshine hours (Hs) at eight stations in the Dongting Lake Basin, China are used for model development and validation. The first part of this study focuses on testing the model accuracies at each station using local input and output data. The results show that LSSVR and FG models with more input variables perform better than the MARS, M5Tree and MLR models in predicting daily Ep at most stations with respect to mean absolute errors (MAE), root mean square errors (RMSE) and determination coefficient (R2). In the second part of this study, the models are tested using cross-validation method in two different applications. The daily Ep of Yueyang station is estimated using the input and output data of Jingzhou and Changsha, respectively. Comparisons of the models indicate that the FG, LSSVR and MARS models outperform the M5Tree model, Ts, Hs and Ta are major influencing factors and adding Ws or RH into model inputs significantly improve the model performances. The overall results indicate that above models can be successfully used for estimating daily Ep using local input and output data while the FG and LSSVR generally perform better than the other models without local input and outputs.