Glacier meltdown

The Himalayas are losing 8 billion tonnes of frozen water annually

That the Himalayan glaciers are melting rapidly is known. But what is unnerving is that the rate of their erosion has doubled in recent years. This latest revelation calls for focused strategies to tackle its causes and consequences. The Himalayan snow deposits, the lifeline of the rivers emanating from this mountain chain, are critical to meet the water needs of millions of people in India and other Asian countries, particularly during the pre-monsoon summer months. A recent satellite data-based study of around 650 glaciers across the 2,000-km Himalayan range estimates that the rate of decline in the snow cover, which averaged around 22 cm between 1975 and 2000, has accelerated to over 43 cm between 2000 and 2016. Going by this reckoning, published in the journal, Science Advances, the Himalayas are losing nearly 8 billion tonnes of frozen water every year, which is not recompensed through snowfall. 

Though this study holds global warming as the most dominant cause for snow decay, it does not discount the conclusion of an earlier study, released in February, that the rampant environmental pollution in the plains along the Himalayan hills also contributes to it. The air pollutants, such as black soot (carbon) and dust, which find their way to the glacial ice, absorb heat from the sun and hasten snow melting. The scariest takeaway from these studies is that even if the Paris agreement’s goal of capping global temperature rise to 1.5 to 2 degrees Celsius above the pre-industrial levels is met — which seems unlikely — the Himalayas could still lose over a third of their ice cover by the end of this century. 

Glacier meltdown of this scale has varied repercussions for the water flows in the 10 major rivers and countless rivulets and other water streams originating from these hills. The main fear is that the water flows in these channels would turn uncertain, irregular and, more so, unpredictable. In the shorter run, the increased snow melting may swell their water stocks, heightening the risk of floods. But in the longer run, with the perceptible contraction of the snow cover by around, say, the 2050s, the flows would tend to taper off, causing frequent water shortages downstream. Experts believe that the mighty rivers like the Ganga and the Brahmaputra, which get sizable water inflows from the monsoon-fed tributaries, would also witness considerable variations in water availability because the pre-monsoon flows may dwindle.

The need, therefore, is to expand the water storage capacity to hold surplus rainwater during the monsoon season. The bulk of this water now runs off wastefully to the seas, eroding precious soil in the process. Though the scope for the construction of large reservoirs is rather limited for various reasons, including land submergence and its attendant population displacement-related issues,  small and medium projects can easily be taken up in large numbers. Also, thousands of old ponds, reservoirs and other water bodies, which are lying in disuse, can be revived to store water. Guiding the runoff water into the underground aquifers through rainwater harvesting structures is the best and the safest method of water preservation. This aside, the efforts to curb air pollution in areas adjoining the Himalayas also need to redouble to reduce snow melting. Otherwise, there is little hope for a water-secure future.