1 ESTIMATING LOCAL SUGARCANE EVAPOTRANSPIRATION USING LANDSAT TM IMAGERY∗

This paper presents an approach for evapotranspiration (ET) estimation using Landsat Thematic Mapper (TM) data for a sugarcane field in northern New South Wales, based on the concept of a vegetation index / temperature trapezoid (VITT). Landsat TM thermal band was used to extract surface temperature and the red and near infrared bands were used to derive the vegetation indices. Three vegetation indices (NDVI, SAVI and MSAVI) were compared, and the relationships between these indices and the surface temperature (Ts) were examined. A moisture availability index (Ma) and, subsequently, the ET rate were computed using Ts and NDVI derived from remotely sensed data. The VITT concept was evaluated using the field measurements of surface reflectance and surface obtained temperature during sugar cane growth period. The estimation of Ma was evaluated using a water balance model which uses well-established computer software and input data. Results shows that Landsat TM data can provide a practical means for studying the spatial variation in ET and making useful estimates of ET and related soil water status of the sugarcane field