Groundwater depletion drying up Ganges in summer

Kolka ta: groundwater depletion in the Gangetic aquifers of north India is possibly causing a reduction in the base flow of the mega Himalayan river, leading to it drying up during summer, according to a study.

The research, undertaken by three scientists, including Abhijit Mukherjee, Associate Professor of Geology and Geophysics at Iit-kharagpur, demonstrated quantitatively that the present phenomenon of the Ganges drying up in the summer months is possibly also dependent on the groundwater depletion in the Gangetic aquifers of north India because of extensive groundwater pumping. Research scholar Soumendra Nath Bhanja, currently in Canada, and Yoshihide Wada from the International Institute of Applied Systems Analyses (IIASA) in Laxenburg, Austria, were also involved in the study.

“During the non-monsoon period, a river usually is fed either by glacier inflow or by input (base flow) from the groundwater system. In fact, groundwater input in the water volume of the Ganges during summer is at least 30 per cent. Decline in contribution from groundwater to the Ganges’ water volume would lead to loss of its total water volume,” Mukherjee said.

He said the “base flow might have decreased by over 50 per cent from the beginning of irrigation-pumping age in the 1970s”.

“Future (up to 2050) conservative, predictive analyses of Ganges river water-groundwater interactions, without effects of climate change or human interferences, provides an alarming scenario. The authors suggest that in the forthcoming summer for next 30 years, groundwater contribution to Ganges river water flow would continue to decrease in the impending years and can decrease up to 75 per cent of the 1970s, causing a catastrophic effect,” the study suggested.

Acknowledging the study, Observer Research Foundation’s (ORF) Distinguished Fellow Jayanta Bandyopadhyay said there is “a mutual bilateral link” between the water flow on the river and ground water.

A former professor at the Indian Institute of Management-calcutta, Bandyopadhyay, pointed out that any large river feeds the ground water laterally when the level of water flow on the river is high and in return, when the flow is low, which is near to base flow, the groundwater feeds the river.

“With no availability of ground water, lean season base flow of a river depends on water coming from upstream. It is true groundwater extraction reduces water flow of the Ganges,” Bandyopadhyay said.