Understanding a Himalayan tragedy

| Updated on February 08, 2021 Published on February 08, 2021

Climate change has transformed flowing glaciers into lakes that cause flooding downstream, as Dhauliganga deluge shows

In 2004-05, the International Center for Integrated Mountain Development (ICIMOD), Kathmandu, and Wadia Institute of Himalayan Geology (WIHG), Dehradun, prepared an inventory of glacial lakes in Uttaranchal (Uttarakhand) Himalaya. The study identified 1,439 glacial lakes with a total area of 4,060 square kilometres.

In view of global and regional warming, the lakes have expanded in size as the glaciers are shrinking and have become more vulnerable to Glacier Lake Outburst Floods (GLOFs) as happened on Sunday in Dhauliganga valley and in Kedarnath in 2013.

Chinese glaciologists have projected a 43 per cent decrease in the glacial area on average by 2070, and 75 per cent decrease by the end of the 21st century at the current exponential warming rate. If that happens, it will have a far-reaching effect on the hydrological processes in the Himalayan-Tibetan region.

Recently, using satellite data and mathematical modelling, more and more climate scientists have started to recognise the impact of short-lived black carbon deposits or soot on glacier melting. Improving air quality control can help address climate change and delay accelerated glacial melting as clean industry, clean transport and clean energy will give us clean air and a stable climate.

The north-bound glacier tongues in Kashmir and Zanskar valleys show speeds of several tens to over 200 m a year . They are almost debris free as the ice flux drains the large accumulation areas through the north-bound valleys, in order to keep the glacier in geometric equilibrium. These glaciers dynamically adjust to climate variations and thus respond by retreat to atmospheric warming than local decay.

In contrast, the southern flowing glaciers in Sikkim and Uttarakhand, and Bhutan have high debris cover and velocity of around 40 m a year near the tongues, which appear to be nearly stagnant. The response to atmospheric warming for these glacier tongues is downwasting — essentially decoupled from the dynamics of upper glacier parts. They are more vulnerable to form glacial lakes near tongues.

Mutual feedback

The Indian climate and the Himalayan ecosystem represent a mutual feedback relationship. While the Himalayan ecosystem plays a significant role in regulating the climate system of the Indian subcontinent, it is in turn getting affected by the changes in the climate system due to global warming and regionally by atmospheric brown clouds. Huge anthropogenic influences have further exacerbated the vulnerability of Himalayan ecosystem.

Himalayan glaciers make the largest extent of freshwater source outside the polar regions. Glaciers and snow-melt in the Himalayan ecosystem are the source of water for several rivers that flow across the Indian subcontinent and are responsible for maintaining the perennial supply of water in river systems like the Indus, the Ganga, and the Brahamputra to over a billion people.

The Himalayan glaciers have reduced considerably in their mass and surface area from the size attained during the Little Ice Age. Global temperatures began to rise after 1850 .They climbed more rapidly in the 20th century as the use of fossil fuels proliferated and greenhouse gas levels continued to soar. The rise has been even steeper since the early 1980s, with record-breaking summer heat and mild winter during the 1990s.

The Little Ice Age has given way to a new climatic regime, marked by prolonged and steady warming, with no sign of downturn. Certain models predict that an increase of 2 degrees Celsius by 2070 would result in 45 per cent of the present of large and medium size glaciers and 70 per cent small glaciers having an area under 10 sq km disappearing.

This would cause reduced water supplies. Unpredictability in snow cover will further reduce water availability during spring and early summer times. Shrinking glaciers have led to the formation of large numbers of glacier lakes all across Himalayas. Many of these high-altitude lakes are potentially dangerous and GLOFs can cause catastrophic flooding downstream, with serious damage to life and high-value investment on power plants.

Remote sensing

Glacial lakes are still being created and many that exist continue to grow. The formation and growth of lakes need to be monitored on a routine basis to determine possible instability and potential threats to downstream communities and infrastructure like power projects.

Repeated remotely sensed images of high resolution can be used to observe the changes in glacial lakes such as expansion mechanisms for monitoring purposes. But sole reliance on remote sensing data is inadequate as it cannot provide repeat bathymetric information (depth of glaciers), changes in the height of moraines (glacial debris), or changes in lake levels.

To meet the threat posed by formation of glacial lakes, a structural and geo-technical engineering solution oriented approach is also to be adopted — that is, draining out water from glacial lakes, construction of channels for gradual and regulated discharge of water.

These approaches are by themselves beset with formidable challenges arising from altitude and inaccessibility of glacial lakes for a significant part of the year. The Nepalese government has installed an alarm system on many potentially dangerous glacial lakes.

Journalist Bryan Walsh, in his piece ‘Climate Change: The Tragedy of the Himalaya’ in TIME magazine published on December 14, 2009, had rightly said: “What’s needed is cold, hard data in a cold, hard place.”

The writer, a former Professor of Glaciology, School of Environmental Sciences, JNU, is Pro-Chancellor Jamia Hamdard University, New Delhi

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Published on February 08, 2021
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