New Delhi, Oct. 19: Swathes of eastern India resembled a gigantic overflowing bucket for parts of this week, with several areas flooded though the monsoon rainfall in the region till September was a staggering 28 per cent below average.
Twelve of the region’s 15 large river-fed reservoirs were brimming with water on Thursday night. (See chart)
Water levels in three of Jharkhand’s five large reservoirs were above the full capacity although the operators, facing the threat of overflowing dams, had released water earlier in the week, causing floods in Bengal’s East and West Midnapore, Hooghly and Howrah.
Bounteous October rain and the after-effects of Cyclone Phailin have made up for the deficient monsoon (till September) in the eastern states, causing rivers to swell, reservoir levels to rise and threatening crops and homes across Bengal, Bihar and Odisha, weather scientists and hydrologists have said.
Between October 1 and 17, Jharkhand received nearly 309 per cent of the average rainfall that it witnesses during this period of the year. October rain has been 216 per cent above average in Bihar and 135 per cent above average in Gangetic Bengal, according to India Meteorological Department (IMD) data released today.
“The states of the rivers and reservoirs here have dramatically changed through the October rain and Phailin,” said Biswajit Chakravorty, a scientist and the head of the Centre for Flood Management Studies in Patna.
The withdrawal of the monsoon from India’s northwest has been unusually late this year, said a senior IMD scientist in New Delhi. The emergence of Phailin further delayed the withdrawal.
“A cyclone in the Bay of Bengal makes the monsoon current stronger,” the scientist said.
The IMD said the monsoon today withdrew from Uttar Pradesh, Madhya Pradesh, Gujarat, Bihar, Jharkhand and Chhattisgarh, from most parts of Odisha, and from some parts of Gangetic Bengal.
A Central Water Commission official said stored reservoir water is typically released only when absolutely necessary.
“It’s near the end of the monsoon season — no (reservoir) operator would want to release water now,” said Vijay Kumar Nagpure, director of water management at the commission.
The commission monitors 15 large reservoirs in eastern India scattered across Jharkhand, Odisha, Bengal and Tripura and daily updates their water levels.
Nagpure said reservoir operators at each site have standard procedures to determine the water levels that can be allowed to accumulate before the water is discharged downstream.
Chakravorty said the two days of torrential rains in distant Uttarakhand that had devastated several towns in the mountain state in June this year may also have contributed to the higher-than-anticipated river flows downstream in the Ganga basin.
“Some of the tributary flows eventually join the Ganga,” Chakravorty said.
In Bihar’s Arwal district, the Punpun river is swollen. The rain brought by Phailin, which crossed the Odisha coast on October 12 night, has damaged crops and property in Purnea, Katihar and Vaishali.
The monsoon rainfall deficit in the Northeast, though, has persisted through October and may explain why stretches of the Brahmaputra have remained relatively flood-free this year.
Rainfall in Arunachal Pradesh, through which the river passes before entering Assam, has been 50 per cent below average in October, while the deficit in Assam is 29 per cent.
Hydrologists say that eastern India’s flat terrain and its high density of river tributaries have throughout history rendered it especially vulnerable to flooding by swollen and shifting rivers.
Besides, the deforestation upstream in the northern states contributes to the sediment deposits downstream in Bihar and Bengal.
“The sedimentation raises the river bed downstream,” said Chakravorty. “There is less space for water to flow and it spreads on both sides, causing floods.”