Climate Change

Change in rainfall patterns is behind regular floods in Rajasthan

Number of ‘heavy rain’ days have gone up in recent years, finds IMD analysis

 
By Anil Ashwani Sharma
Published: Wednesday 27 July 2022
Jodhpur reported 118mm of rainfall between the evening of July 25 and the morning of July 26. Photo: RavindraYogii/Twitter
Jodhpur reported 118mm of rainfall between the evening of July 25 and the morning of July 26. Photo: RavindraYogii/Twitter Jodhpur reported 118mm of rainfall between the evening of July 25 and the morning of July 26. Photo: RavindraYogii/Twitter

Climate change might be behind the change in rainfall pattern in recent years, leading to regular floods. The rainfall pattern in the state has changed over the last decade, with a greater number of ‘heavy rain’ days. 

Days receiving more than 65 millimetres of rainfall are called ‘heavy rainfall’ days.

Western, eastern and southern districts of the state have been inundated with floods this monsoon. Jodhpur reported 118 mm of rainfall from Monday evening to Tuesday morning. 

The state now reports floods almost every year. However, the state's climate action plan is still made with drought in mind, showing a lack of preparation.

Analysis of rainfall data from the India Meteorological Department (IMD) of 1989-2018 showed a significant increase in the number of ‘heavy rain’ days in the last decade. This was especially true for western parts of the state. 

The analysis said there were fewer rainy days, but there was a rapid increase in the days with ‘heavy rainfall’.

This might be why sudden torrential rains are causing flood-related disasters in the state almost every year. The number of severe cyclonic storms in the areas adjoining the Indian Ocean has also increased significantly over the last few years.

However, another weather expert disagrees. 

The contribution of monsoon rains in June, July and September to India’s annual rainfall is decreasing while the contribution of August rainfall is increasing in some areas, said TI Khan in another analysis. 

Khan is the former director of Indira Ghandi Centre for Human Ecology, Environment Studies and Population Studies at the University of Rajasthan, Jaipur. 

“There has not been a significant difference in the amount of monsoon rain in India every year, only in the form of the rain,” he said.

Another IMD study showed that Rajasthan recorded more seasonal rainfall, especially in western parts. 

In the last ten years, there have been only two such years when the monsoon rains were below average, the analysis said.

The normal level of average rainfall in western Rajasthan has increased by 32 per cent since 2010, while in eastern Rajasthan, it has increased by 14 per cent.

The analysis said the desert areas of western Rajasthan received 18 days of rain in 2016 and the average single-day rainfall crossed 120 mm. In east Rajasthan, it rained 126 times. 

But the analysis shows a definite change in the rainfall pattern. 

The turning point in the rain situation came in the form of the floods in Barmer in 2006. This desert district received 750 mm of rain in the last week of August 2006, which was five times its average annual rainfall. 

The severe floods caused more than 300 deaths. It was described as the most dangerous flood in the 200-year history of Rajasthan.

A 2013 research by the Max Planck Institute tried to explain and define the effects of climate change in recent years with the help of high-resolution multimodality.  

The average level of rainfall in west Rajasthan will increase by 20-35 per cent and east Rajasthan will increase by 5-20 per cent in 2020-2049, compared with 1970-1999 data. 

The density and frequency of rains will increase in Rajasthan in the future, a 2009 report by Swiss Agency for Development and Cooperation had stated. The single-day rainfall in the state is expected to increase to a maximum of 20 mm and five-day rainfall up to 30 mm by 2071-2100.

These estimates and data on the floods in the desert clearly indicate the direction the state is headed in terms of heavy rains. However, a serious and in-depth research is urgently needed.

Another study published in 2009 analysed data from 1871 to 200 and estimated a secondary trend of decline in the annual and seasonal average of rainfall. 

The study, published in The Journal of Geophysical Research, reported June and July as the months with heavy rainfall. Until the 1970s, there were signs of more rain only in June, it said. 

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