Analysis of to Techniques of Determination of Evapo-Transpiration, Using Satellite Imageries

Determination of Evapo-Transpiration (ET) in the vast area with a suitable temporal resolution is a powerful instrument in the optimum management of water resources, agricultural management in determination of the optimum cultivation for different region and for climate studies. Measurement of ET in the vast area using Lypsimeters, is very costly and time consuming. On the other hand, error in determination of ET by theoretical dilemmas such as Eddy Correlation or between ratio due to the need in using meteorological parameters are inevitable. These limitations resulted in the use of remote sensing data in determination of ET in the vast area with a suitable temporal resolution to be improved. Until now, a comprehensive study regarding remote sensing of ET in Iran either has not been implemented or is not published. Of course, occasionally some study in the possible relation between ET and parameters such as NDVI has been carried out but no simultaneous filed data to confirm such relation has been gathered.In this study we tried to introduce several methods in ET assessment using satellite images. In addition, the main difficulties in deploying the available algorithms and ways of their mitigation have been discussed.