Finding a mathematical model for calculating the Evapo Transpiration Potential (Middle section of the Assi Basin

الملخص

In this research an analytical study was conducted for the values of (Evapo Transpiration Potential)(ETP) measured in the field by a (lysimeter)device and linked to the most important climatic factors affecting the determination of the values of (ETP)and consequently on the plants consumption of water. The most important of these factors are humidity air temperature and speed wind and number of hours of solar brightness and precipitation and then finding an empirical (linear) mathematical equation to calculate (ETP) based on those climatic factors in the study area (the middle section of the Orontes Basin) and making a comparison between its calculated and measured value during the studied time period and in the dry months the six (april, may , june , july , august , September) irrigation water, This equation simulates the reference evaporation and transpiration values in the well-studied area, where the correlation coefficient of this equation reached (R=80%).accordingly there is a need to derive other equations for different climatic zones in order to check the calculation of water needs. Climatic data were  taken from the Homs climatic station, located in the study area near the village of (TIR MAlEH) on the Homs-Hama highway, about 12km north of the city of Homs.