Question

The average monsoonal rainfall of India is

• A. 400 M ha-m
• B. 119 M ha-m
• C. 180 M ha-m
• D. 300 M ha-m

Hint:

Remember the national water budget breakdown: 400 M ha-m is the total annual rainfall, and 300 M ha-m (or 75%) is the monsoon contribution.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
The water resources of India are evaluated based on annual precipitation volumes.
The standard unit used for country-wide volumetric measurements is Million Hectare-meters ($\text{M ha-m}$).

Step 2: Detailed Explanation:
Let us analyze the national water budget of India:
- The total geographical area of India is approximately $329\text{ million hectares}$.
- The average annual depth of rainfall over the country is about $1190\text{ mm}$ ($1.19\text{ m}$).
- This corresponds to a total annual precipitation volume of:
\[ V_{\text{total}} = 329\text{ M ha} \cdot 1.19\text{ m} \approx 400\text{ M ha-m} \]
- The South-West Monsoon (monsoon season, June to September) is the primary source of rainfall, contributing approximately 75% of this total annual precipitation.
- Therefore, the volume of rainfall received during the monsoonal period is:
\[ V_{\text{monsoon}} = 75\% \text{ of } 400\text{ M ha-m} = 300\text{ M ha-m} \]
The remaining $100\text{ M ha-m}$ is received during winter, pre-monsoon, and post-monsoon showers.

Step 3: Final Answer:
The average monsoonal rainfall of India is 300 M ha-m.