Distribution of rainfall across India, with climate tables
India's rainfall is very uneven: over 200 cm on the west coast and in the north-east, under 60 cm in western Rajasthan and Ladakh.
Patterns to remember
- In the northern plains, rainfall decreases from east to west.
- In the peninsula, rainfall decreases from the coasts to the interior.
- In the north-east, rainfall increases with height.
- India has some of the rainiest and some of the driest places in the world.
- Mawsynram and Cherrapunji (Sohra) in the Khasi hills of Meghalaya are among the wettest places on Earth. Western Rajasthan is among the driest parts of India.
Four rainfall zones
| Zone | Annual rainfall | Main areas |
|---|---|---|
| Heavy | More than 200 cm | West coast; sub-Himalayan north-east; Garo, Khasi and Jaintia hills |
| Moderate | 100 to 200 cm | Parts of the Western Ghats, West Bengal, Odisha, Bihar |
| Low | 60 to 100 cm | Parts of Uttar Pradesh and Rajasthan; interior Deccan |
| Inadequate | Less than 60 cm | Western Rajasthan and Gujarat; Ladakh; parts of the interior south |
Activity: reading a climate table
Mumbai's monthly figures from the lesson's climate table. Temperature (°C): 24, 24, 24, 28, 30, 29, 27, 27, 27, 28, 27, 25. Rainfall: 4, 2, 2, 2, 18, 465, 613, 329, 286, 65, 18, 2. Find the annual range and the mean of temperature, the total and monthly average of rainfall, and the rainiest month.
- Annual range of temperature = highest − lowest = 30 − 24 = 6 °C.
- Sum of the 12 temperatures = 320. Mean annual temperature = 320 ÷ 12 = 26.7 °C (rounded to one decimal place).
- Total rainfall = 4 + 2 + 2 + 2 + 18 + 465 + 613 + 329 + 286 + 65 + 18 + 2 = 1,806.
- Monthly average rainfall = 1,806 ÷ 12 = 150.5.
- Rainiest month = July (613). June to September give 1,693 of the 1,806, almost all the year's rain.
- Units: values of this size are millimetres, so 1,806 mm is about 181 cm. The lesson's table heads the column 'cm'; in the exam, use the unit the question gives.
Range 6 °C and mean 26.7 °C: an equable coastal climate. Total 1,806 mm (monthly average 150.5 mm), with July the wettest month: a monsoon pattern.
Three more stations from the lesson's table
| Station | Annual range of temperature | Rainiest month | What it shows |
|---|---|---|---|
| Leh (Ladakh) | 17 − (−8) = 25 °C | July and August (13 mm each) | Cold, very dry and extreme |
| Chennai (Tamil Nadu) | 33 − 25 = 8 °C | November (350 mm) | Coastal and equable; most rain in October and November from north-east winds |
| Shillong (Meghalaya) | 21 − 10 = 11 °C | June (476 mm) | A cool, very wet hill station of the north-east |
Activity: a floods and droughts diary
- 1Keep a notebook through one rainy season, or longer.
- 2Cut out or copy every news report of a flood or a drought from newspapers, radio or TV.
- 3For each report, write the place, date, cause and effect.
- 4Mark each place on an outline map of India: one colour for floods, another for droughts.
- 5★Look at the pattern. Floods often hit the Brahmaputra valley of Assam, north Bihar (the Kosi), West Bengal and the Odisha deltas. Droughts often hit western Rajasthan, Kachchh and the rain-shadow parts of interior Maharashtra and Karnataka.
- 6Note the causes: very heavy rain in a short time, a late or weak monsoon, long breaks, and poor management of water.
★ key step
On the map
- Above 200 cm (west): a strip along the west coast and the Western Ghats, from the Konkan to Kerala.
- Above 200 cm (north-east): the Garo, Khasi and Jaintia hills of Meghalaya and the sub-Himalayan parts of Assam and Arunachal Pradesh. Mawsynram and Cherrapunji lie in the Khasi hills.
- Below 60 cm (west): western Rajasthan and Kachchh in Gujarat, west of the Aravallis.
- Below 60 cm (north): Ladakh, the cold desert behind the Himalayas.
- Below 60 cm (south): rain-shadow pockets of the interior Deccan, east of the Western Ghats.
- How to show it: shade the area lightly, write its name, and add a small key such as 'more than 200 cm'.
Water tankers in dry districts of Rajasthan and boats on flooded roads in Assam can appear in the same week's news. Both come from India's uneven rainfall.
2 marks: “Why is the distribution of rainfall in India uneven? Give two reasons.” Monsoon winds shed most rain where they first meet coasts and hills, then lose moisture as they move inland and westwards. Areas in rain shadow, or where winds blow parallel to the hills (as along the Aravallis), get little rain.
4 marks: “On an outline map of India, mark and label: (i) an area of over 200 cm rainfall on the west coast (ii) an area of over 200 cm rainfall in the north-east (iii) an area of less than 60 cm rainfall in western India (iv) Ladakh.” (i) The Konkan or Malabar coast strip. (ii) The Meghalaya hills. (iii) Western Rajasthan. (iv) The far north, behind the Himalayas. Shade each lightly and add a key.
1 marks: “Name the hills of Meghalaya that receive more than 200 cm of rain.” The Garo, Khasi and Jaintia hills.
Wet: West coast and North-east (above 200 cm). Dry: Desert and Ladakh (below 60 cm). Learn the lines 200, 100 and 60.