National Institute of Technology: Hyderabad likely to witness extreme unseasonal rainfall in future

HYDERABAD: Intense unseasonal rainfall leading to flooding are likely to become a routine affair in Hyderabad in near-future, says a new study. The primary reason is a climate phenomenon called El-Nino Southern Oscillation (ENSO).Researchers from National Institute of Technology (NIT), Warangal conducted a study to see the relationship between ENSO and the Indian Ocean Dipole (IOD) —another climate phenomenon—with the extreme rainfall events occurring during monsoon and non-monsoon months in Hyderabad observing two time periods—1901-1950 and 1951-2004. June-September is the monsoon season.

They found a 60 per cent increase in ENSO effect on extreme rainfall events in Hyderabad in the non-monsoon months. This is a cause of concern as global warming might add to the damage along with El Nino or La Nina—the two  discrepancies of ENSO which occur once in few years. The researchers had already established in a previous study that La Nina has more effect on extreme rainfall events in Hyderabad. It may be recalled that last year, Hyderabad witnessed many spurts of rainfall in October and November, measuring 5-10 cm per hour (categorised as extremely intense) and between 3-5 cm per hour (very intense spell), flooding various parts of the city. 

However, when it comes to ENSO effect on extreme rainfall events during monsoon, there was no significant change in the two time periods taken for study. Whereas, in the case of IOD, it was observed that there was no significant relationship between IOD and extreme rainfall during monsoon months but it was seen that the relationship of IOD on extreme rainfall events during monsoon months decreased by as much as 50 per cent, in the 1951-2004 period as compared to 1901-1950.

“With an increase in extreme rainfall events, the risk of urban flooding also increases. Our project is aimed at providing data which would help the municipality in achieving this. There is also a need to increase rain gauges in Hyderabad and store rainfall intensity information on an hourly basis,” said Dr NV Umamahesh who was part of the study.