Spatial and temporal variations in the occurrences of wet periods over major river basins in India

This study highlights the hydro-climatic features of the five wet periods contributing in different percentages to the annual rainfall total over major river basins in India. Spatial and temporal variations in the parameters such as starting date, duration and rainfall intensity of these wet periods throughout India have been discussed using daily gridded rainfall data for the period 1951-2007. An attempt is also made here, to assess the impact of global SSTs on the start and duration of the wet periods in Indian river basins. It is observed that, for almost all river basins in India, the 10% wet period occurs in the months of July/August with an average duration of 1-3 days and rainfall intensity varying from 44 to 89 mm/day. The duration of the wet period contributing 90% to the annual rainfall varies from 112 days in the ceatral parts of India to 186 days in the northern parts of the country. Significant increase in the rainfall intensity has been observed in the case of some river basins of central India. The late start of 75% wet period along the West Coast and in peninsular river basins has been observed with increase in Nino 3.4 SSTs (MAM), while increase in the duration of the 75% wet period over the Krishna basin is associated with increase in Nino 3.4 SSTs (concurrent JJAS).