Question

The general rules applicable for locating the raingauges:
A. The opening of the raingauge should be at least 50 cm above the ground level.
B. The raingauge should be located in an open space free from obstructions.
C. The distance of the raingauge from the obstruction should be at least twice the height of the obstruction.
D. Uneven topography should be avoided.
Choose the correct answer from the options given below:

• A. A, B and D only
• B. A, B and C only
• C. A, B, C and D
• D. B, C and D only

Hint:

The most important rule for raingauge placement is exposure: place it in a level, open area far from obstructions, at a distance of at least 2 times the height of any nearby object.

Answer 1

The Correct Option is D

Step 1: Evaluate each rule for siting a raingauge.
- Rule A: The standard height for a non-recording gauge (Symon's gauge) is 30.5 cm above the ground. For recording gauges, it can be higher (e.g., 75 cm). Stating it should be "at least 50 cm" is not a universally correct rule and contradicts the most common standard. Therefore, this statement is questionable.
- Rule B: This is a fundamental requirement. The gauge must be in an open space to prevent surrounding objects from shielding it from rain. This is correct.
- Rule C: This is the standard exposure rule to avoid wind-eddy effects and interception from nearby objects. The distance to any obstruction should be at least twice its height. This is correct.
- Rule D: The ground around the raingauge should be level to avoid splashing into the gauge from higher ground and to ensure a representative catch. This is correct.
Step 2: Conclude the correct combination.
Rules B, C, and D are standard, essential criteria for accurately locating a raingauge. Rule A is not a standard general rule (the height is specific to the gauge type and often different from 50 cm). Therefore, the combination of B, C, and D is the most accurate answer.