Detection of evapotrairation is very important for the identification and precise determination of the contribution of each of the components of evapotrairation and is the basis of many management plans and irrigation planning. The purpose of this research is to determine the contribution of pistachio evapotrairation components whit using Landsat 8 satellite imagery and the use of the Beer's-Lambert Law. In this research, 14 gardens were selected in Bahadoran region of Yazd province. In each garden, a tree representing the whole garden was selected, then I / I 0 was measured using the light meter, That I is the amount of radiation reaching the surface under the canopy and I 0 is the amount of radiation reaching the high level of the canopy In addition, a set of Landsat 8 satellite imagery (including 16 images) was developed and using ILWIS software, LAI index maps were extracted in the study area. Then, using the Beer's-Lambert law, the amount of extinction coefficient (K) of the pistachio tree was calculated. The results showed that the amount of pistachio tree extinction coefficient in Bahadoran region is 0.67. After determining the actual evapotrairation using the SEBAL algorithm (ETa) at the points of the study area, the Beer method was used to separate the actual evaporation (Ea) from the actual evapotrairation (ETa). The results showed that the evaporation contribution on average accounts for 17% of the total evapotrairaton, and trairation is a major contribution in the Bahadaran pistachio gardens. To evaluate the calculated evaporation using the Beer formula in three gardens that were well-dispersed soil moisture was measured. After determining the volumetric moisture content of the soil at two time steps, it was possible to calculate the average surface evaporation through the formation of soil moisture balance equation for duration of between two measurements. The results showed that the measured and calculated evaporation using Beer's-Lambert formula were not significantly different whit RMSE of 0.049. It can be said that the Beer's-Lambert law and Landsat 8 satellite imagery can estimate the evaporation. Key word : Pistachio, Evaporation Separation, Trairation, extinction coefficient, Landsat 8, SEBAL Model
