Question

Which terminology defines the ratio between the irrigated area and the quantity of water used

• A. Delta
• B. Duty
• C. Base
• D. Intensity of irrigation

Hint:

Remember the classic relationship between Duty (D in hectares/cumec), Delta (\(\Delta\) in meters), and Base Period (B in days):
\[ \Delta = \frac{8.64 B}{D} \]
A higher duty means less water is needed to irrigate a unit area of land.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
In irrigation engineering, several terms are used to define the relationships between the volume of water supplied to agricultural fields, the duration of supply, and the total crop area irrigated.

Step 2: Detailed Explanation:
Let us define the primary irrigation terms to identify the correct ratio:
- Duty: This is defined as the area of land (typically in hectares) that can be fully irrigated by a continuous unit discharge of water (typically \(1\text{ m}^3/\text{s}\) or cumec) flowing throughout the base period of the crop.
Therefore, duty represents the direct ratio between the irrigated area and the quantity of water used:
\[ \text{Duty (D)} = \frac{\text{Area irrigated (hectares)}}{\text{Discharge (cumecs)}} \]
- Delta (\(\Delta\)): This is the total depth of water (usually in cm or meters) required by a crop during its entire growing period in the field.
- Base Period (B): This is the total time in days from the first watering of a crop at the time of its sowing to its last watering before harvesting.
- Intensity of Irrigation: This is the percentage of the Culturable Command Area (CCA) proposed to be irrigated annually or during a specific cropping season.
Thus, the term that defines the ratio of irrigated area to the quantity of water used is Duty.

Step 3: Final Answer:
The terminology that defines this ratio is Duty.