Rapid Himalayan glacier melt poses severe climate threat to Northeast & Bangladesh: Expert

Guwahati, April 19: Due to the rapid melting of the Himalayan glaciers, the Third Pole", that is the Hindu Kush Himalayan (HKH) region has been turned into one of the hot spots of climate change and if the current situation continues, the unfolding scenario specifically in the North East region of India and Bangladesh would be very grim in the days to come, said the internationally acclaimed river expert and former Professor of the Indian Institute of Technology (IIT) Roorkee, Prof Nayan Sharma.

The Hindu Kush Himalayan region has the largest concentration of frozen water on Earth after the North Pole and South Pole, hence it is referred to as "the Third Pole". Like the Arctic and part of Antarctica, the Hindu Kush Himalayan region is warming faster than the global average. The melting of snow in the North and South Poles has become a matter of serious concern for the entire world. However, in recent decades, the melting of snow cover has been faster in the Third Pole HKH, which is a matter of very serious concern.

Talking to The Assam Tribune, Prof Sharma pointed out that the mountainous areas like the Hindu Kush Himalayas are more susceptible to the effects of global temperature rise. He revealed that as per scientific studies, the forecast is truly alarming because of the fast melting of snow and the glaciers. Recalling his first-hand experience, he said, "As part of an international research project, 1 visited the Austrian Alps and saw the receding glacier there because of fast melting of snow. "IPCC AR4 report warned that "Glaciers in the Himalayas are receding faster than in any other part of the world and the likelihood of many of them dis appearing by the year 2035 is high if the Earth keeps warming at the current rate. Total glaciers area (in HKH) may reduce from the present 500,000 to 100,000 sq km by the year 2035.

Prof Sharma said that as per scientists, the temperature gradient between the Himalayan snow cover mass and the sea surface temperature (SST) of the Bay of Bengal closely influences the prevailing climatic behaviour of the Brahmaputra plains. Due to the fast melting of snow, the summer discharge of the rivers may progressively increase, which may give rise to dangerous portents. Besides amplified flood-erosion, physical infrastructures in the Brahmaputra Basin including the numerous bridges, dams and age-old irrigation structures would come under threat. Their critical design review is urgently necessary for retrofitting with the appropriate latest technology to withstand increasing climatic extremes as well as to derive optimal output by eliminating obsolescence.

Prof Sharma specifically highlighted the obsolescence of more than 30 irrigation headworks built over half a century ago with sub-optimal benefits. He also advised to convert on priority these age-old irrigation canal systems into Level-Top Canals to de-rive In-Canal Storage provision as an adaptive measure of climate change effects to sustain agriculture productivity.

Prof Sharma warned that a notable pitfall on the bridge foundation depths which are provided based on conventional hydrological analysis to assess anticipated floods performed on recorded stream flow data, without considering climate-induced flood escalations. Prof Sharma said that there may be a serious threat to the bridges if the river dis-charge increases exceeding the conventional design flood value.

Researchers cautioned of a massive 50 per cent upsurge in the sediment concentration in the Brahmaputra waters by the end of the century. Sharing his own experience, Prof Sharma sounded a grim warning that this predicted sediment upsurge together with an unrelenting intensification of the channel braiding process may pose a very serious threat to the bridge pier foundations, particularly in the receding phases of flood events. Similarly, in the lean season, the Brahmaputra is most likely to dry up due to the unabated retreat of the source glaciers, which would also pose severe water shortages in riparian areas including Assam.

Geologically, the tectonic instability of Eastern Himalayan Tibet is frequently rocked by earthquakes, and this region presents formidable challenges for any mega-dam project. Prof Sharma reiterated that the construction of a mega-dam by China, high up in the geologically fragile seismic-prone Great Bend of the Brahmaputra is a huge threat to the North East Region. Though China is claiming it to be a run-of-the-river dam, experts believe that there would have to be a mega dam in the project. The sudden release of excess flows from the dam during monsoon may spell grave disaster in the Brahmaputra plains as it may exceed the capacity of the proposed Indian dam at Yingkiong. Also, the lean flow of the Yarlung Tsangpo is likely to be stored in the Chinese dam causing reductions in dry weather Brahmaputra flow. Also, the possibility of China diverting away the water of the dam cannot be ruled out. He suggested planning the Yingkiong dam for large storage adequately with sufficient spillway capacity using advanced technology to cushion the effects of any Chinese dam break floods.