.Evaporation and Transpiration:

Factors affecting evaporation:
1. Temperature;
2. Humidity;
3. Wind;
4. Solar Radiation.


Evapotranspiration: if the ground covered with vegetation, it is
impossible to diffrenciate between evaporation
and transpiration. The two processes are linged together and referred to Evapotranspiration.

Evapotranspiration= evaporation+ transpiration.



Potential Evapotranspiration (PE): The Evapotranspiration when
water supply is unlimited.

Potential Evapotranspiration (PE): The Evapotranspiration when
water supply is unlimited.


Methods of Estimating Evaporation:

1. Water – Budget (storage) equation;
2. Energy – Budget equation;
3. Penman s Theory.
Direct Measurments of Eo:
Potential Evapotranspiration (PE):
1. Estimation of PE from Eo

2. Thornth waits formula: