Estimation of actual evapotranspiration (AET) and its spatial distribution are important to understanding
of catchment hydrology. The AET is driven by net energy available to evaporate water from soil and vegetation
surfaces, and to transpirate water from vegetation. However, estimating AET is difficult as the evapotranspiration
process involves complex physical and biological processes. It is further complicated when there is lack of measured
meteorological variables data which are required for estimation. These data are essential to quantify the availability
of net energy and the aerodynamic effects of the evapotranspiration process. Remote sensing (RS) data, which are
widely available and easily accessible than the measured ground data, can be used to estimate the availability of net
energy for AET. However, still some measured ground data are required to quantify the aerodynamic effects on
AET. In this study, remote sensing data and readily available climate datasets were used as inputs to an energy
balance technique to estimate AET, as an alternative to the traditional ET estimation procedures, which require
measured hydrometeorological data. The Macalister subcatchment in the Thomson catchment in Victoria (Australia)
was used as the case study considering the study period from January 2003 to December 2008.