The Ganga that has nourished the Indian civilisation for centuries has recorded a historically low inflow in its lower reaches this year, going by the evidence on the ground. The inflow at the Farakka barrage in West Bengal nearly halved, compared with the quantum of water available in the last two years. The NTPC’s plant beside the barrage had to shut operations from March 10.
Though statistical information on the inflow is not in the public domain, because the river is an international resource, protected for strategic purposes, The Hindu obtained local water level data to verify claims of a reduced inflow. A.K. Pal, superintending engineer at the Farakka barrage, confirmed: “On March 29, the inflow discharge observed in the Ganga by the India-Bangladesh joint observation team was 50,710 cusecs, while in comparison the discharge on 29/03/2014 and 29/03/2015 were 91,001 cusecs and 83,807 cusecs respectively.”
Himanshu Thakkar, coordinator of the South Asia Network on Dams, Rivers and People, said this was a scary development with the summer just beginning. “We are already seeing a historically low inflow downstream of the Farakka in the Ganga, which reflects the health of the entire river basin,” he said. He blamed the situation not only on deficit rainfall and a dry winter but also on the increasing exploitation of the river in its upper reaches.
West Bengal Pollution Control Board chairman Kalyan Rudra, considered an authority on the river, ruled out greater quantum of water being diverted to Bangladesh, under the international water sharing treaty, as the cause for the reduced levels.
Glaciers are receding, but the Gangotri is not going to vanish, says an expert
“While this is the initial understanding, the reasons could be more varied. In the upper catchments, the first intersection of water happens in the hydel power projects, then once the river reaches near Haridwar, there is withdrawal for irrigation. From hereon, there is considerable exploitation of groundwater for irrigation, which affects the base flow. Indiscriminate withdrawal might be one of the causes. Though the Ganga goes dry during the lean season from March, historically low inflow underscores serious concerns over upstream withdrawal,” he said.
However, with the onset of Himalayan snowmelt in mid-April, the water levels would improve from the first week of May. In June, with the monsoon, the levels would rise again, he said.
Glaciologists studying the Himalayan sources of the river allay concerns that reduced snowmelt from the retreating glaciers might further affect the water levels, though they are divided over the extent of the impact. “That the glaciers are receding is true, but the Gangotri is not going to vanish,” argues Manohar Arora, scientist at the National Institute of Hydrology (NIH), Roorkee.
The glacial retreat has affected the flow in the river but its effects have been more localised, according to NIH Director R.D. Singh. “…the amount of water coming from the glacial melt to the Ganga is not so significant as to affect the entire river basin. So we need to look at tributaries to the river coming from Nepal as 80 per cent of the river’s flow downstream comes from there.”
The coordinator of the Ganga River Basin Management Plan, Vinod Tare, also a professor at the IIT-Kanpur, said studies conducted by the IIT had shown that anthropogenic stress through expansion of cities by the river, denudation of forests, encroachment of floodplains and excess groundwater extraction had affected the river severely. “In order to protect the cities by the river from floods, embankments are constructed, and these elevate the river. As a result, there is more run-off during the rains, and rainwater doesn’t percolate deep enough to recharge its aquifers. And this is a gradual process whose effects are now being felt.”
But all the scientists The Hindu spoke to were unanimous in their demand for more detailed investigation into the causes of water levels dipping, including the glacial retreat, as there is a dearth of information.