The sheer scale of the calamity that devastated the temple town and pretty much anything it encountered nearly 40 km downstream is now stirring scientists to the reality of a long-ignored but potentially catastrophic threat posed by the rapidly melting Himalayan glaciers-Glacial Lake Outburst Floods (GLOFS) triggered without warning by extreme rainfall, unpredictable seismic events or increased glacial melting.

"The Kedarnath floods may be only a small precursor to never-seen-before mega floods," says Maharaj K. Pandit, director, Centre for Inter-disciplinary Studies of Mountain & Hill Environment, Delhi University. Scientists like him believe that the high precipitation on June 16 rapidly filled up Chorabari Tal, a glacial lake less than 4 km upstream from Kedarnath, and the continuing downpour the next morning caused the lake to overflow and possibly burst out from its loosely packed rim of moraines (glacial sediments).

SHAPE OF THINGS TO COME

There is evidence from the field suggesting that a sudden outflow from the lake, located below the south-facing snout of the Chorabari Bamak Glacier, 'connived' in the destruction in Kedarnath. On June 17 morning, two young researchers of Dehradun's Wadia Institute of Himalayan Geology's (WIHG) glaciology station, located at the base of Chorabari Tal, went about recording their observations with a distinct sense of foreboding. The lake was filling up too fast. Trouble was inevitable.

The men heard a loud bang, only mildly muffled by the sound of the incessant rain and the rushing river. "It was like a big explosion," they later told their boss, WIHG's senior glaciologist Dwarika Prasad Dhobal. "The boys barely escaped to safety, clambering up the nearest hill as they helplessly watched the lake rim collapse and flooding water sweeping away their tented observation station," Dhobal told INDIA TODAY.

Though relatively unknown or, perhaps, not adequately recorded in the upper Ganga basin, the last 100 years have witnessed at least 50 glacial lake outburst floods at several places across the Hindu Kush Himalayas, from Afghanistan to Myanmar. The earliest recorded events include one in August 1929 when a lake at the base of the Chong Kumdan Glacier in the Karakoram mountains broke its margins to release 15 billion cubic metres of water to flood the Indus Valley. Water levels rose to more than 8 m at Attock (Pakistan), situated more than 1,300 km downstream. More recently, a GLOF on August 4, 1985, from the Dig Tsho glacial lake in eastern Nepal destroyed a hydroelectric power project, 14 critical mountain bridges besides hundreds of hectares of farmland.

Pradeep Mool, programme coordinator for glaciers and GLOFS at the International Centre for Integrated Mountain Development (ICIMOD) in Kathmandu, has used satellite-based geographical information system (GIS) and high resolution remote sensing technology to locate nearly 20,000 glacial lakes across the Himalayas, straddling Afghanistan, Pakistan, Tibet, India, Nepal and Bhutan. "More than 200 of these have been classified as potentially dangerous," he says.

It is like a ticking time bomb. GLOFS are capable of releasing billions of cubic metres of glacial water, stored for decades, in a few short hours or even in a matter of minutes and virtually without warning to those living downstream. "They have a huge potential for causing damage," Mool says, echoing a growing community of scientists who are already pressing the panic button on what they describe as "Himalayan tsunamis."

Pandit says the significantly pronounced 'warming' in the snowbound higher Himalayas is not only resulting in the expansion (in volume) of existing glacial lakes but also causing the formation of new water bodies. A report compiled by the scientist and his colleagues at Delhi University for the Ministry of Environment and Forests in 2008 showed the existence of 316 glacial lakes in Sikkim's Teesta basin, 50 more than what ICIMOD reported just four years earlier.

The surface air temperatures in the Indian Himalayas have increased by one degree Celsius in the past decade, which is significantly higher than the global average. The warming of Sikkim, thrice the world average, is even more worrying. Eddy Moors of the Earth System Sciences and Climate Change group at Alterra Wageningen University, Netherlands, says that the average temperatures in the Ganga basin are set to increase by one-two degrees Celsius by 2050. "Since the total precipitation will increase due to rising temperatures, snowfall in the Himalaya will decrease by about 30 per cent," the Dutchman had predicted in a 2012 interview.

In a 2012 study in the journal Conservation Biology, Pandit and coauthor R. Edward Grumbine employed endemic Himalayan plants and animals to demonstrate an upward altitudinal shift by several species in response to the rising heat. "Biological indicators cannot be fudged," Pandit says, concerned over the evidence that suggests that the warming is greater during the winter than in summer. "This means there is reduced snow accumulation and this is why our glaciers are melting and receding," he says.

THE THREAT OVERFLOWS

The threat from hitherto disregarded glacial lake outburst floods in the Indian Himalayas has been most pronounced in Sikkim. Based on a detailed study of the 5,000 m high Shako Cho glacial lake below the southern face of the Kangchenjunga Swiss geologist Raphael Worni and his colleagues reported in 2012 that a breach of the lake margin was capable of releasing 16 million cubic metres of water at a devastating rate of 7,000 cubic metres every second. Another potentially dangerous water body at the base of the 7,000 m high South Lhonak glacier (in Northeast Sikkim) is reportedly spread over 99 hectares and bears an incredible 19.7 billion litres of water, poised precariously close to causing another gigantic flood capable of seriously affecting downstream populations for hundreds of kilometres.

The hazard is evidently spreading to other Himalayan terrains with glaciers receding up-mountain and assuming steeper gradients. Besides the evidence now available from Kedarnath, which is located in an area not generally known for GLOFS, two years ago researchers from IIT-Mumbai spotted seven new glacial lakes in the Chandrabhaga basin of Lahaul-Spiti, all formed between 1963 and 2010. The new lakes have grown significantly in size. Studies also show that glaciers of the basin have been receding at over 15 m per year with the maximum retreat taking place in the past decade.

Unlike in Nepal and Bhutan, among the first countries in the world to make glacial outburst floods a national priority, information on basic glaciology and more specifically the threat from GLOF in the Indian Himalayas is scattered and of little real value. Few scientists and geologists have been willing to take on the hazard of field checks to confirm satellitebased data collected in the comforts of an air-conditioned GIS laboratory.

But Pandit says "obliviousness" and "lethargy" may no longer be an option. Kedarnath seems to be telling us just that. While WIHG glaciologist Dhobal says he is not inclined to view the June 16-17 flooding as the consequence of a GLOF because he has "never recorded such an event in the Ganga basin in the last 20 years", he admits that the signs are ominous.