Human intervention in Himalayas, warming may cause more floods in Ganga: Study

Climate change and anthropogenic activities are altering Ganga river’s water flow, which may result in more floods in the coming years, says a joint study conducted by the Indian Institute of Science (IISc) and the Indian Institute of Technology-Kanpur.

The research team drew its conclusions based on information on rainfall, water discharge in rivers and sediment load in the Upper Ganga Basin between 1971 and 2010.

Scientists observed that the water flow in Alaknanda river – one of the two tributaries along with Bhagirathi that merge at Devprayag to form Ganga – has doubled between 1995 and 2005, which is the cause of more flooding in the Ganga basin and is likely to take an extreme form in the years to come.

The research, published in open access journal, ‘Scientific Reports’, blames human activities in the Himalayan region over the last many years, like building dams, besides climate change, for the sorry state of the Ganga today.

Dams and reservoirs disturb sediment flow of rivers. Dams like Tehri, which is built in the upper Ganga basin, block sediment flow and prevents it from flowing downstream, thus affecting the river’s morphology.

The increased water flow is because of dams that have come up on the Alaknanda river after 2010. Climate change has only made things worse. “Dams and reservoirs have influenced the sediment transported by the rivers. Due to abrupt changes in water flow, sediment depositions in the upper reaches of the Ganga have led to changes in the sediment composition downstream,” the research stated.

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Somil Swarnkar, a postdoctoral fellow at the Interdisciplinary Centre for Water Research (ICWaR), IISc, and the lead author of the study, said, “We observed that Alaknanda basin has a high, statistically increasing rainfall trend, unlike the Bhagirathi basin. Most of these trends were observed in the downstream region of the Alaknanda. Therefore, we have also seen an increase in the magnitude of extreme flow in these regions.”

While addressing climate change would be a long-term task, governments can employ technology and new types of hydraulic structures to create a balance in water flow of the Ganga, the study suggests.

Co-author of the study, Pradeep Mujumdar said, “We cannot control what happens in the atmosphere. But on the ground, we have control. Flows can be predicted using hydrological models. With this knowledge, we can develop both structural and non-structural responses to mitigate such high flows.”