Study rings drought alarm for Northeast

TT, New Delhi, Dec. 12: India's traditionally wet northeastern region has experienced a higher frequency of drought than arid western India over the past 15 years, researchers have said, cautioning that this trend has implications for crop productivity in the region.

An analysis of the summer monsoon rainfall since 2000 has shown that the probability of drought was 54 per cent in the northeastern region and 27 per cent in the traditionally arid zones of Kutch, Saurashtra and Rajasthan.

"This is a surprise because the Northeast has been considered a region of rainfall abundance," said Bikash Ranjan Parida, assistant professor of civil engineering at the Shiv Nadar University, Noida (Uttar Pradesh), and lead author of the study whose research specialisation covers climate change.

But the findings appear to corroborate an independent study by scientists at the Space Applications Centre, Ahmedabad, which had last year also detected a decreasing trend in the summer monsoon rainfall across the country, with a sharper decrease in the Northeast.

The study by Parida and his colleague Bakimchandra Oinam, a civil engineer at the National Institute of Technology, Imphal, Manipur, has shown that the summer monsoon rainfall in the northeastern region has "gradually dropped" over the past 15 years compared to the rainfall it received during the 1980s and 1990s. The results of their study were published this week in the journal Current Science, published by the Indian Academy of Sciences.

The researchers analysed rainfall patterns and measures of soil moisture - specifically the departure from normal rainfall - over Assam and Meghalaya and in Kutch, Saurashtra and Rajasthan between 2000 and 2014.

Assam and Meghalaya experienced drought in eight of the 15 years, while the western India zones had only four drought years. "We don't know whether this is a long-term trend and whether it is linked to global warming - we need more research to study that," Parida said.

The scientists picked Assam to examine the impact of the drought on crop productivity. Paddy is the main crop in the state cultivated through winter, summer and autumn. Other major crops include jute, tea and pulses.

They found, as anticipated, that paddy production was adversely affected during the drought years. Assam, for instance, received 30 per cent below normal rainfall in 2006 and rice crops were severely affected in several districts, including Dhubri, Nalbari and Jorhat.

But senior meteorologists say a drought in the Northeast is likely to have fewer implications on crop productivity than a drought in western India - because the amount of normal rainfall that the Northeast gets is traditionally high and small departures from normal will not have significant impacts.

The northeastern region has long been classified as a zone of high rainfall with a subtropical and humid climate. The scientists say the drought pattern they have observed may reflect an increasing variability - erratic behaviour - of the monsoon predicted to occur under the influence of global warming. A temperature rise associated with global warming could lead to warming-induced droughts and also adversely impact crop yields.

Last year, Markand Oza and C.K. Kishtwal at the Space Applications Centre had analysed century-long rainfall patterns across the country and observed that the rainfall decrease is two-fold steeper in the Northeast than in the rest of the country. "The rate of decrease is steeper towards the east," Oza and Kishtwal wrote in their paper.