NEW DELHI: India should urgently initiate adequate measures for extreme events in the water sector as number of rainy days is falling across the river basins in India and rainfall intensities are seen to be increasing, said a study.
The study by a team of experts from the National Institute of Hydrology, Roorkee found the changes in heavy precipitation and peak flood for seven major river basins -- Cauvery, Godavari, Krishna, Mahanadi, Narmada, Sabarmati and Baitarani and Brahamani.
Data pertaining to daily flows for about 30-odd years and precipitation for 61 years (from 1951 to 2012) were analysed. It included number of rainy days, annual average rainfall and annual peak rainfall series of different intensities.
“The number of rainy days is falling across the basins and rainfall intensities are seen to be increasing. During the concurrent period annual peak rainfall is seen to decrease in the upstream areas of the basin, whereas plain areas of the basins show increasing annual peak rainfall,” said the study published in Current Science.
It is noteworthy to mention that the number of events is more in the plain-region compared to head reaches of the basins. There is minimum increase of 28 percent (year 1979) in 50 mm rainfall events in the Mahanadi basin and maximum increase of 236 percent during the period 2001 in the Cauvery basin.
Besdies, floods of small magnitude show a falling trend, possibly due to higher upstream water use and development of storages which trap high flows and release the water later. Floods of high magnitude have almost no appreciable trend in the studied basins at the gauged locations downstream.
“Increasing rainfall intensities and decreasing number of rainy days indicate that the country should urgently initiate adequate measures for extreme events in the water sector,” it found.