Estimation of Evapotranspiration by Satellite Remote Sensing by Energy Balance Approach

Estimation of Evapotranspiration by Satellite Remote Sensing by Energy Balance Approach

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Gowri. V
Assistant Engineer
PWD (WRO),
India
Email: [email protected]

Dr. D. Thirumalaivasan
Assistant Professor
Institute of Remote Sensing, Anna University, Chennai
Email: [email protected]

Evaporation is vital for regional scale hydrological modeling. It is very essential for the water managers and irrigation engineers to know the accurate ET estimations. Direct measurement of actual ET is difficult and at the best, mostly provides point values. However conventional ET measurements from point based measurements can possibly provide accurate ET estimates. An alternative ET estimation approach is to combine remote sensing observations along with common surface meteorological data and surface energy balance model. Satellite based measurements used in association with energy balance models can provide the spatial distribution of ET. This paper focuses on the estimation of actual evapotranspiration based on the Surface Energy Balance Algorithm for Land (SEBAL). SEBAL requires spectral data from the following bands visible, near-infrared and thermal infra-red, which are taken from Landsat ETM sensor. The algorithm was applied to LANDSAT ETM data for assessing the actual ET. The satellite images were preprocessed and were further processed to derive the land surface parameters as required by the energy balance models to derive ET. Having estimated the land surface parameters, the SEBAL model was employed to estimate daily actual ET. This study has considered deviation of actual ET from potential ET calculated through penman-Montieth model. The actual evapotranspiration, thus, estimated using energy balance approach could be useful for irrigation planning.