The Measurement Of Infiltration, Evaporation And Evapotranspiration

Student: Rajnish Singh Arnat, ID: 1315999
1) Describe the measurement of Infiltration, Evaporation and Evapotranspiration.
Describe the measurement of infiltration, evaporation and evapotranspiration.
1.0 Infiltration
Infiltration is the movement of water into a soil profile. The rate at which infiltration occurs is controlled by the inherent properties of the soil, the level of soil saturation when rainfall starts, and by the ways in which humans have modified the landscape. The measure of infiltration called the infiltration rate is usually done in the field by flooding basins or furrows or measuring water entry from infiltrometer rings. Measurement by ponding in large areas is the most reliable but due to its cost, the infiltrometer rings

The volume of water added into the tube at regular time intervals to maintain a constant depth is recorded from which the infiltration curve can be drawn.

2.0 Measurement of Evaporation
The rate of evaporation is measured using evaporation pans. The general procedure involves filling an evaporation pan with water up to a defined mark. The water lost is estimated by determining the volume of water required to fill the pan up to the defined mark on a daily basis. An allowance has to be made for rainfall. For determining lake evaporation, the evaporation pan is set up near a lake on a wood grillage,
10 cm above ground to allow circulation of air. The evaporation pan is fitted with a stilling well, a point gauge and a thermometer. The pan may be screened or not. The water that has evaporated from the pan can be read from the gauge while the air temperature can be obtained from the thermometer. Readings must be taken atleast twice daily. Water is then added to the pan so as to fill the latter up to the defined mark. An allowance has to be made for

Likewise evaporation, evapotranspiration is also difficult to measure as there are many factors like wind or water uptake that influences the measurement. The measurement of evapotranspiration for a vegetation can be carried out mostly by using lysimeters.
Lysimeters are tanks filled with soil in which crops are grown under natural conditions to measure the amount of water lost by evaporation and transpiration. This method provides a direct measurement of the crop evapotranspiration. The procedure involves weighing of the lysimeters in a given time. Though limitations are present, this is best way to measure