Distribution of Annual Rainfall
The regional variations in average annual rainfall are well pronounced. The distribution map of rainfall shows that northeastern parts of Jammu and Kashmir and extreme western Rajasthan receive a rainfall of less than 20 cm.
On the other hand, the west coastal plains, Sub-Himalayan areas of northeast India including the Shillong plateau receive more than 200 cm of annual rainfall. Southern slopes of Khasi and Jayantia Hills, particularly the Cherrapunji valley receive the highest rainfall exceeding 1000 cm.
Starting from the southern coast of Gujarat, the isohyte of 200 cm runs somewhat parallel to the coast of Western Ghats upto kanyakumari. To the east of Western Ghats, the rainfall drops abruptly below 60 cm over interior Maharashtra and Karnataka. Most parts of Punjab, Haryana, central and eastern Rajasthan and western Gujarat also receive rainfall below 60 cm. Starting from the southwestern parts of Jammu and Kashmir, the isohyte of 100 cm moves eastwards upto east of Allahabad from where it bends to the west and south west, running over western Madhya Pradesh, eastern Maharashtra and northern Andhra Pradesh, it joins eastern coast near Visakhapattnam.
To the west and south west of this isohyte, the areas receive less rainfall. Some parts of Coromondel coast receive a rainfall of more than 100 cm. The areas receiving less than 100 cm of rainfall depend on means of irrigation for agricultural activities. In India, distribution of rainfall particularly of the southwest monsoon has a close relationship with the relief. Hence it is even described as “relief” or “orographic” rainfall. By and large places with higher altitude have greater chance to catch more rainfall than the places with less altitude. The direction of moist winds also matters.
Summary
The distribution of annual rainfall in different parts of India shows the following trends:
- The rainfall decreases as one moves from Kolkata to Amritsar.
- It shows declining trend towards interior from the coastal areas on Deccan Plateau.
- Northeastern parts receive more rainfall than north western parts of India.
- Areas lying on the windward side receive more rains than the areas lying on the leeward side.