Evaluation of evapotranspiration using energy-based and water balance hydrological models

Abstract

The reliability of evapotranspiration (ET) models is crucial to comprehending land–atmosphere interactions and water balance dynamics in various available resources of the model. This study compared two different models based on energy and water balance models, a surface energy balance system (SEBS) and SPHY, and evaluated against ground observation data from flux towers for different land cover characteristics (forest and savanna) in Southeast Africa. We found that both models have a good correlation with flux tower data for both sites (ZM-Mon and ZM-Kru). The SEBS model showed a lower root-mean-square error (RMSE; 2.17 mm day−1) at the savanna site (ZM-Kru) than the SPHY model (2.27 mm day−1). However, at the forest site (ZM-Mon), the SEBS model showed a higher RMSE value (1.90 mm day−1) than the SPHY model (0.88 mm day−1). Then, we analyzed the ET model's sensitivity to the precipitation variable. We found that SPHY overestimated ET during the winter season and underestimated it during the summer season, which might be influenced by the dependency of the SPHY model to water excess and water shortage stress parameters in ET calculations. Overall, SPHY, with fewer input data, showed a reasonably good result compared to the SEBS. The results revealed that each model possesses its unique strengths and limitations in relation to specific land covers and vegetation composition, offering opportunities for improvement and optimization.