Climate change and extreme hydrological events over India

Nearly 80% of the annual rainfall over mast parts of India is received during the short span of 4 months from June to September, known as the southwest monsoon season. The time series of Indian monsoon rainfall (IMR) for the 126-year period (1871-1996) has been subjected to statistical tests. No long-term changes are detected. However, the short term (decadal) changes reveal that there are distinct epochs of above and below normal IMR. Further analysis reveal that the impact of El Nine (La Nina) is more severe an IMR during the below (above) normal rainfall epochs than the above (below) normal rainfall epochs. On a close examination of the epochal behaviour of IMR of the last few years, there is an indication that probably the IMR is tending towards an above normal epoch with a turning point around 1990. This suggests that the impact of El Nine on IMR may not be severe and that India is probably more vulnerable to floods than droughts during the next decade or two.