Question

Given below are two statements:

Statement (I): Penman proposed an equation for evaporation from an open water surface based on a combination of energy balance and sink strength.

Statement (II): For converting PET into ET, suitable crop coefficients should be evolved for different crops, soils and climatic conditions and also for different stages of growth for the same crop.

In light of the above statements, choose the most appropriate answer from the options given below.

• A. Both Statement (I) and Statement (II) are correct.
• B. Both Statement (I) and Statement (II) are incorrect.
• C. Statement (I) is correct but Statement (II) is incorrect.
• D. Statement (I) is incorrect but Statement (II) is correct.

Hint:

Recall what the Penman equation combines and how PET is converted into actual crop water use.

Answer 1

The Correct Option is A

Take each statement and place it against what is actually taught about Penman's method and crop coefficients.

Penman's evaporation formula is famous precisely because it merges two older separate approaches, the energy balance method that uses net radiation and the aerodynamic method that uses wind speed and humidity deficit, the sink strength term, into one workable equation for open water evaporation. That matches Statement (I) directly.

Once potential evapo-transpiration is known, actual crop water use is obtained by multiplying it with a crop coefficient, $ET_{crop} = K_c \times PET$. Since $K_c$ changes with the crop, its growth stage, the soil, and the climate of the region, agronomists build separate coefficient tables for each of these situations, which is exactly what Statement (II) describes.

Both statements hold up under this check.

\[\boxed{\text{Both Statement (I) and Statement (II) are correct}}\]