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: Assess the suitability rules for raingauge placement.
- Rule A: The recommended height for a non-recording gauge (Symon's gauge) is 30.5 cm above ground level. Recording gauges may be placed higher (e.g., 75 cm). A blanket rule of "at least 50 cm" is not universally applicable and conflicts with common standards. Consequently, this rule is questionable.
- Rule B: This is a critical requirement. The gauge must be located in an unobstructed area to prevent surrounding objects from interfering with rainfall capture. This rule is valid.
- Rule C: This rule addresses standard exposure to mitigate wind-induced errors and shadowing by adjacent structures. Obstructions should be at a minimum distance of twice their height from the gauge. This rule is valid.
- Rule D: The ground surrounding the raingauge must be level to prevent splash-in from elevated areas and to ensure representative rainfall collection. This rule is valid.
Step 2: Determine the correct combination.
Rules B, C, and D represent standard and essential criteria for accurate raingauge placement. Rule A is not a generally accepted standard, as the optimal height varies by gauge type and often differs from 50 cm. Therefore, the combination of B, C, and D constitutes the most accurate selection.