Hydrometeorology instrumentation: What is the standard rim height of a standard (Symons-type) rain gauge above ground level used for measuring rainfall?

Introduction / Context:
Rain gauges must be installed at a prescribed height above ground to minimize splash-in/splash-out errors and interference from surrounding features. In Indian practice (Symons rain gauge), a standard mounting height is adopted to ensure consistency across stations.

Given Data / Assumptions:

• Standard non-recording rain gauge installation.
• Open exposure, away from obstructions per siting guidelines.
• Rim elevation above ground is fixed by standard.

Concept / Approach:
The standard rim height is maintained to reduce local turbulence and ground splash effects while keeping access practical. In the Symons gauge commonly used, the rim is set at approximately 30 cm above ground level.

Step-by-Step Solution:
Install the gauge on a level base.Adjust stand so that the orifice rim is 30 cm above the soil surface.Verify verticality and unobstructed exposure as per siting recommendations.

Verification / Alternative check:
Field manuals and bureau standards specify the rim height; periodic inspections confirm compliance and calibration.

Why Other Options Are Wrong:
10 cm or 20 cm: too low, prone to splash and local effects.50 cm: higher than standard; increases wind-induced error potential.

Common Pitfalls:
Placing the gauge near walls or tall vegetation; mounting at non-standard heights; poor leveling leading to biased catch.

Final Answer:
30 cm