the heavy rainfall in the north - eastern states can be attributed to their hill ranges and the Eastern Himalayas. Figure . : India : Seasonal Rainfall (June-September) (iii) The monsoon rainfall has a declining trend with increasing distance from the sea. Kolkata receives cm during the southwest monsoon period, Patna cm, Allahabad cm and Delhi cm.
(iv) The monsoon rains occur in wet spells of few days duration at a time. The wet spells are interspersed with rainless interval known as ‘breaks’. These breaks in rainfall are related to the cyclonic depressions mainly formed at the head of the Bay of Bengal, and their crossing into the mainland. Besides the frequency and intensity of these depressions, the passage followed by them determines the spatial distribution of rainfall.
(v) The summer rainfall comes in a heavy downpour leading to considerable run off and soil erosion. (vi) Monsoons play a pivotal role in the agrarian economy of India because over three-fourths of the total rain in the country is received during the south- west monsoon season. (vii) Its spatial distribution is also uneven which ranges from cm to more than cm. (viii) The beginning of the rains sometimes is considerably delayed over the whole or a part of the country.
(ix) The rains sometimes end considerably earlier than usual, causing great damage to standing crops and making the sowing of winter crops difficult. Season of Retreating Monsoon The months of October and November are known for retreating monsoons. By the end of September, the southwest monsoon becomes weak as the low pressure trough of the Ganga plain starts moving southward in response to the southward march of the sun. The monsoon retreats from the western Rajasthan by the first week of September.
It withdraws from Rajasthan, Gujarat, Western Ganga plain and the Central Highlands by the end of the month. By the beginning of October, the low pressure covers northern parts of the Bay of Bengal and by early November, it moves over Karnataka and Tamil Nadu. By the middle of December, the