Estimation of Catchment‐Scale Evapotranspiration With the Simple Method Based on the Maximum Entropy Production Principle

ABSTRACT Estimating catchment‐scale evapotranspiration remains a difficult problem in hydrology. This study introduces a new approach on the basis of the Maximum Entropy Production (MEP) principle, which has been applied for point estimations in earlier studies. The expansion to the catchment scale is achieved by adopting the simplified MEP method and parameterization to reflect the heterogeneity in the catchment. To obtain references for the latter, the flux tower data are studied. The method is applied to a Korean catchment in two tracks of utilising satellite remote sensing and ground data. The proposed approach allows the calculation of all heat fluxes, including the latent heat flux, that is, evapotranspiration. The estimated evapotranspiration is well compared with the global product of the Penman‐Monteith‐Leuning model as well as the annual water balance, derived from ground‐measured precipitation and runoff. An appropriate temperature estimation, representative of the catchment, is found the priority for better performance. Our study shows that the MEP‐based method is found a promising option for estimating catchment‐scale evapotranspiration, whilst allowing users to utilise either ground measurement or satellite data, depending on availability.