Context

Human activities have had a disastrous impact on the Ganga river basin, ranging from severe pollution to changing its course, and are behind the landslides and floods seen in recent years, according to a new study.

About

The study

• For the study, researchers analysed the effects of past human activity on mountainous regions, focusing on Bhagirathi and Alaknanda.
  • These two major tributaries merge at Devprayag to form the Ganga, the lifeline of half a billion Indians.
• Researchers examined data on rainfall, water discharge in the rivers and sediment load from weather stations across the Upper Ganga Basin from 1971 to 2010.
• They analysed the data corresponding to two periods: pre-1995 and post-1995.

What activity is responsible for this situation?

• Anthropogenic activities (activities driven by humans) have had disastrous impacts on Ganga, from severe pollution to changing its course.

What has been found?

• Catastrophic landslides and floods in the Ganga basin have become more frequent in recent years.
• Increasing number of flooding events: Researchers found a steady increase in the number of flooding events in both river basins after 1995. The change in low flows and middle-level flows in Bhagirathi can be attributed to three major dams — Maneri, Tehri, and Koteshwar — on the river.
• Lack of sedimentation: Building of dams in the Alaknanda regioncoupled with climate change have modified the water activity as dams and reservoirs have influenced the sediment transported by the rivers.
• Alteration of river’s morphology: The lack of sedimentation in the downstream Ganga basin has altered the river's morphology.
• Extreme flow: The Alaknanda basin saw a doubling of water flow from 1995 to 2005 at Joshimath weather station, while also seeing an increase in the rate of flow of water, termed extreme flow.
• Severe impact of ecological process: The Himalayan regions are one of the worst affected by climate change in India, meanwhile increasing numbers of dams and reservoirs on these freshwater sources has severely impacted the ecological processes in the Himalayan River basins.

Indian Himalayan Region The Indian Himalayan Region includes most parts of the north-eastern states and hill areas of West Bengal. The large rivers emerging from the IHR are the Ganga, Brahmaputra, Barak (in the Meghna basin) and Indus. These rivers are joined by many tributaries from the Himalayan region, especially from Bhutan and Nepal.

• Tehri dam plays a crucial role in the upper Ganga basin region. Being a large reservoir and flow control structure, it blocks sediment flow from upstream and controls the volume of water that flows downstream.

The Ganga River Basin

• The Ganges River originates in the Himalaya Mountains at Gomukh, the terminus of the Gongotri Glacier.
• When the ice of this glacier melts, it forms the clear waters of the Bhagirathi River.
• As the Bhagirathi River flows down the Himalayas, it joins the Alaknanda River, officially forming the Ganges River.
• The Ganges River Basin is sometimes considered part of a larger river basin consisting of the nearby Brahmaputra and Meghna rivers.
• Known as the Ganges-Brahmaputra-Meghna (GBM) River Basin, it is one of the largest river systems in the world.

Structure of the Basin

• It crosses five states of India namely Uttarakhand, Uttar Pradesh, Bihar, Jharkhand and West Bengal.
• Major tributaries of River Ganga are Yamuna, Ramganga, Gomti, Ghaghara, Gandak, Damodar, Kosi and Kali-East
• Flowing through major cities/towns like Srinagar, Rishikesh, Haridwar, Roorkee (in Uttarakhand), Bijnor, Narora, Kannauj, Kanpur, Allahabad, Varanasi, Mirzapur (in Uttar Pradesh), Patna, Bhagalpur (in Bihar) and Beharampore, Serampore, Howrah and Kolkata (in West Bengal), it drains into the Bay of Bengal.