The distribution of rainfall across India is highly variable and significantly impacts agriculture, water resources, and overall climate conditions. Understanding this distribution is crucial for recognizing the climatic diversity in the country.

1. Monsoon System

The Indian monsoon system is a key factor in determining rainfall distribution:

• Southwest Monsoon: The southwest monsoon, which typically arrives in June, brings the majority of rainfall to the Indian subcontinent. It originates from the Indian Ocean and moves towards the northwest.
• Onset and Retreat: The monsoon usually reaches the southwestern coast first, particularly Kerala, and gradually spreads across the country. By September, it begins to retreat, marking the end of the rainy season.

2. Rainfall Patterns

Rainfall patterns vary widely across different regions of India:

• Heavy Rainfall Areas: Coastal regions and the Western Ghats receive heavy rainfall, with annual averages exceeding 200 cm. The city of Mawsynram in Meghalaya holds the record for the highest average rainfall in the world.
• Moderate Rainfall Areas: The Indo-Gangetic plains experience moderate rainfall, averaging between 75 cm to 150 cm annually. This region is crucial for agriculture due to its fertile soil.
• Low Rainfall Areas: The Thar Desert and parts of northwest India, such as Rajasthan, receive less than 25 cm of rainfall annually, resulting in arid conditions.

3. Factors Influencing Rainfall Distribution

Several factors influence the distribution of rainfall in India:

• Topography: The physical features of the land, such as mountains and plateaus, significantly affect rainfall. The Western Ghats create a rain shadow effect, resulting in heavy rainfall on the windward side and dry conditions on the leeward side.
• Latitude: Latitude affects temperature and the angle of sunlight, which in turn influences evaporation rates and moisture availability in different regions.
• Proximity to Water Bodies: Areas close to the sea receive more rainfall due to the moisture-laden winds blowing inland. Coastal areas benefit from this maritime influence.

4. Seasonal Variation

Rainfall in India is not uniform throughout the year and varies seasonally:

• Monsoon Season: The southwest monsoon accounts for about 75% of India's annual rainfall, primarily occurring between June and September.
• Post-Monsoon Rains: Some regions, especially the southeastern coast, receive additional rainfall during the post-monsoon season, typically from October to December.
• Winter and Summer Rains: Northern India experiences winter rains from the western disturbances, while summer showers can occur in the form of thunderstorms in various regions.

5. Impact of Rainfall Distribution

The distribution of rainfall has far-reaching effects on agriculture, water supply, and livelihoods:

• Agricultural Productivity: Areas with adequate rainfall support diverse agricultural activities, while regions with low rainfall face challenges in crop production, leading to food security concerns.
• Water Resources: Rainfall patterns influence the availability of water for drinking, irrigation, and industrial use, impacting local economies.
• Socioeconomic Impacts: Regions suffering from insufficient rainfall may experience migration, poverty, and conflicts over water resources.

6. Climate Change Effects

Climate change is altering rainfall patterns in India:

• Variability in Rainfall: Increased frequency of extreme weather events, such as floods and droughts, is affecting agricultural planning and water resource management.
• Changing Monsoon Patterns: The monsoon season is becoming increasingly unpredictable, impacting farming schedules and crop yields.
• Regional Disparities: Some regions may experience increased rainfall while others suffer from reduced precipitation, exacerbating existing disparities in water availability.