Question

Given below are two statements :
Statement (I) : Irrigation tubewells should be so located that there is no interference in the cone of depressions of the two adjoining tubewells.
Statement (II) : Drainage tubewells to lower water table should be so located that there is some interference in the cone of depressions of two adjoining tubewells.
In light of the above statements, choose the most appropriate answer from the options given below.

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

Hint:

- For water supply (irrigation): Well interference is bad (reduces yield).
- For dewatering (drainage): Well interference is good (ensures uniform lowering of the water table).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
When a tubewell is pumped, the water table around it drops in a funnel-like shape called the "cone of depression".
If two wells are spaced too closely, their cones of depression overlap, leading to well interference.
Detailed Explanation:
Let us analyze both statements:
- Statement (I) analysis: For irrigation tubewells, the primary goal is to maximize individual well discharge and minimize pumping energy costs. Overlapping cones of depression (interference) increase the drawdown required to pump the same volume of water, reducing well efficiency. Therefore, irrigation wells should be spaced far enough apart to prevent interference. Thus, Statement (I) is true.
- Statement (II) analysis: For drainage tubewells (pumping wells used to lower a high water table and prevent waterlogging), the goal is to lower the water table uniformly across the entire field. Overlapping (interference) of their cones of depression ensures that the water table is lowered everywhere, leaving no waterlogged spots between adjacent wells. Thus, some interference is highly desirable. Thus, Statement (II) is true.

Step 2: Final Answer:
Since both Statement (I) and Statement (II) are true, the correct choice is Option (A).