Groundwater Hydrology MCQ with answer and solution

Concept

In a strainer tube well, a blank (blind or sump) pipe closed by a bail plug is placed at the bottom, and the strainer sits just above it.

Step-by-step solution

1. A strainer tube well has three main parts. From top to bottom they are the housing pipe, the strainer, and the blank (sump) pipe. 2. The blank pipe is at the bottom. It is closed at its lower end by a bail plug and collects sand and silt. 3. The strainer is fitted just above the blank pipe, against the water-bearing layer. 4. So the strainer is just above the blank pipe.

Explanation

In a tube well, a plain blank pipe is kept at the bottom to collect fine sand that passes through. The strainer, which lets water in from the aquifer, is fitted just above this blank pipe. The housing pipe is at the top.

Why the other options are wrong

B: The main or housing pipe is at the top, above the strainer, not directly above the blank pipe. C: Barrel is not a standard tube-well component. D: Fulcrum is a lever term and has nothing to do with tube wells.

Shortcut

Order from bottom to top: bail plug, blank pipe, strainer, housing pipe.

Common mistake

Students confuse the blank pipe at the bottom with the blind pipes between strainers, and so pick the main pipe.