Question

The actual evapotranspiration divided by crop coefficient gives-

• A. Actual evaporation
• B. Potential evapotranspiration
• C. Actual transpiration
• D. Potential transpiration

Hint:

The crop coefficient ($K_c$) is a dimensionless ratio.
Because it has no units, dividing $ET_a$ (typically in $\text{mm/day}$) by $K_c$ maintains the same units ($\text{mm/day}$), yielding the potential evapotranspiration ($ET_0$).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Crop water requirements vary throughout the growing season.
To standardize these requirements, agricultural hydrologists use a reference potential evapotranspiration rate alongside a crop-specific factor known as the crop coefficient.
Key Formula or Approach:
The relationship between actual evapotranspiration, reference/potential evapotranspiration, and the crop coefficient is given by the formula:
\[ ET_a = K_c \times ET_0 \]
where $ET_a$ is the actual evapotranspiration, $K_c$ is the dimensionless crop coefficient, and $ET_0$ is the reference or potential evapotranspiration.

Step 2: Detailed Explanation:
The crop coefficient ($K_c$) integrates the effects of crop characteristics, planting date, rate of development, and canopy cover.
By rearranging the standard equation to solve for the reference or potential evapotranspiration ($ET_0$), we get:
\[ ET_0 = \frac{ET_a}{K_c} \]
Therefore, dividing the actual evapotranspiration by the crop coefficient ($K_c$) yields the potential (or reference) evapotranspiration.
This reference evapotranspiration represents the evapotranspiration rate from a standardized, well-watered grass or alfalfa reference surface under specific climatic conditions.

Step 3: Final Answer:
Dividing actual evapotranspiration by the crop coefficient gives the potential evapotranspiration, which corresponds to option (B).