Rainfall Distribution in India

5.1 Spatial Distribution

India's rainfall distribution is highly uneven:

Very High Rainfall (>200 cm / 2,000 mm):

• Western coast (Konkan, Malabar) — windward side of Western Ghats
• Meghalaya (Khasi, Jaintia, Garo Hills) — world's wettest region
• Assam, Arunachal Pradesh
• Andaman & Nicobar Islands

High Rainfall (100–200 cm / 1,000–2,000 mm):

• West Bengal, Odisha, eastern MP
• Sub-Himalayan West Bengal, Assam valley
• Western slopes of Western Ghats (lower intensity)
• Eastern coasts of Godavari, Krishna, Kaveri basins

Moderate Rainfall (50–100 cm / 500–1,000 mm):

• Most of the Indo-Gangetic Plain (UP, Bihar, Delhi ~800 mm)
• Madhya Pradesh, Chhattisgarh
• Eastern Maharashtra, Telangana

Low Rainfall (<50 cm / <500 mm):

• Interior Karnataka, Maharashtra (Marathwada, Vidarbha)
• Interior Deccan Plateau (rain shadow zones)
• Western Rajasthan, Gujarat (semi-arid to arid)

Very Low Rainfall (<25 cm / <250 mm):

• Thar Desert (western Rajasthan — Jaisalmer: ~150 mm)
• Karakoram/Ladakh (~75–100 mm — cold desert)

5.2 Temporal Distribution — Monsoon Variability

India's rainfall variability (standard deviation as % of mean) is highest in areas of low rainfall (Thar Desert: 50–60% variability) and lowest in high-rainfall areas (Kerala, NE India: 10–15% variability). This means Rajasthan's rainfall is the most unpredictable — a "good monsoon year" and a "drought year" may differ by 200%.

Year-to-year variability causes:

• ENSO (El Niño/La Niña)
• Indian Ocean Dipole
• Madden-Julian Oscillation (MJO)
• Eurasian snow cover anomalies

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