India is said to be Monsoon country because the climate in India is Monsoon climate. But the distribution of Monsoon rainfall is uneven both regionally and seasonally. Moreover, it is undependable as its occurrence is not at stipulated times.
Unevenness of Monsoonal rainfall in India is found both regionally and seasonally:
Regional unevenness in Indian rainfall is described in the following terms:
□ Mysinram receives the heaviest rainfall in the world. Here the annual rainfall exceeds 1080 cm. On the contrary there are also places in India which receive the least rainfall. Barmer in Thar Desert receives only less than 12 cm annual rainfall. Sometimes it also happens that the western-most part of Rajasthan Desert does not experience even a single centimeter of rainfall for years together.
□ In the Great Plains of the North (the Ganga-Yamuna Plain) Monsoonal rainfall goes on decreasing from east to west during the period of South-West Monsoon. Rainfall on Assam hills exceeds 250 cm while Bihar plain receives only 125 to 150 cm rainfall. In Punjab it decrease to 75 cm only.
□ In the Peninsular India Monsoonal rainfall decreases from west to east. Western slopes of the Western Ghats enjoy more than 250 cm of Monsoonal rainfall. Rainfall decreases from 75 to 100 cm on the eastern slopes of the Western Ghats. It further comes down in the Maidan region of Karnataka, thus putting it in the rainshadow area of the South-west Monsoon. Here rainfall is only 40 to 60 cm.
During winter also, regional variations are found in rainfall distribution; North-west India obtains upto 25 cm of winter rainfall while on the coasts of Tamilnadu as much as 75 cm winter rainfall occurs. In other parts of country winter rainfall is negligible.
Seasonal unevenness is very glaringly experienced in the Monsoonal rainfall of India. This unevenness is revealed in the following account.
1. During summer and rainy season India receives 75% to 85% of the total annual rainfalls while only 15 to 25% of the total annual rainfall is obtained in the remaining period of the year. Southwest Monsoon provides rains in summer and rainy season while North-east Monsoon and western disturbances cause winter rainfall.
2. Tropical cyclones bring rainfall on the coastal region in summer and in the season of Retreating Monsoon.