Terrain Correction for Increasing the Evapotranspiration Estimation Accuracy in a Mountainous Watershed

Evapotranspiration (ET) plays a major role in the energy and water balances of the hydrological cycle. Monitoring ET at a regional level has become feasible with the advance of remote-sensing technology. This letter presents a module that incorporates satellite images, surface meteorological data, and topographic information in estimating ET over a tropical montane watershed. The satellite images used include Thematic Mapper (TM), Landsat-7 Enhanced Thematic Mapper Plus, and Advanced Spaceborne Thermal Emission and Reflection Radiometer with visible, near infrared, shortwave infrared, and thermal infrared bands. The estimated surface energy fluxes are compared with the in situ measurements. The results demonstrate that, compared to other model estimations, the proposed module with terrain correction provides the highest correlation (r = 0.75) between the estimated latent heat flux associated with ET and its corresponding in situ measurement. The proposed module will be further refined and applied to monitor long-term ET over mountainous watersheds.