Glaciers are the source of 75 per cent of the fresh water on which populations and agriculture depend. For thousands of years they have fed many of the largest rivers in the world with a continuous flow of water, enabling development of huge cities, the agriculture to sustain them and burgeoning populations. The effects of their increasingly rapid depletion have the potential to be disastrous.
Six of the great rivers of Asia (Brahmaputra, Ganges, Indus, Mekong, Yangtze-Kiang, Yellow) provide water to between one and two billion people and the agriculture on which they depend. These rivers have one thing in common. All have their source in the glaciers of the Himalayas and Hindu-Kush.
Global warming is responsible for those glaciers melting faster than they are being replenished by snow which would normally compact into ice to maintain their size. Precipitation now falls more frequently as rain rather than snow. As a result, these and nearly all other land-based glaciers in the world are melting and reducing in size with increasing speed. Before the end of this century, none will be left. Many have already disappeared.
As glaciers melt more rapidly, they will produce more water, causing river flooding damaging property, destroying crops and threatening human safety. Droughts of increasing duration will follow as the size and capacity of glaciers to supply water diminishes. Rivers are unlikely to run completely dry for prolonged periods since they are supplied with water from other sources.
However, in the absence of water from glaciers and with growing population, increased demand will be placed on rivers which have diminishing water. Sooner rather than later, they will be unable to continuously supply the water needed to sustain present populations or their food supplies. The Murray-Darling is a good example of what is likely to befall glacier-fed rivers.
Initially, this would result in competition for water between urban populations and those growing crops. Popular needs will prevail and agriculture will fail on a massive scale where reduced river flows are accompanied by lack of rainfall. This will bring hunger, even famine and disease, to hundred of millions and damage the wider economies of China, India, Nepal, Bangladesh, Cambodia and Vietnam.
Political instability and mass movement of people in search of food and water is likely to eventuate. Civil war, even international hostilities, “water wars”, may ensue as relatively unaffected resident populations resist encroachment or invasion by those in need. Few countries will be immune from the effects of thirst and hunger, not even Australia.
How would an Australian government cope if hundreds of thousands of “water refugees” landed on its shores, if Indonesia was unable or declined to curb their transit and if countries of origin refused to or could not take them back? Would it sink boatloads of refugees? Would it expel illegal arrivals and if so, where would it expel them to? How would it provide for their needs? How would it effectively deter their arrival? Has government even considered the prospect of such an eventuality?
The people of California, all 37 million of them, depend on the glaciers of the Sierra Nevada for 65 per cent of their water supply. With the exception of glaciers on the upper slopes of Mt Shasta, the only ones known to be growing, all other glaciers of the Sierra Nevada are melting and shrinking at an unprecedented rate. This is due to the fact that warmer temperatures cause rain rather than snow to fall on them.
Snow falling on the glaciers compacts, turns to ice and maintains their size and capacity to produce water from melting at the periphery. Rain water causes the rate of melting to increase resulting in these glaciers shrinking in size, initially producing more water but then less and less as they contract. Within the next 40-50 years, less than 10 per cent of their present production will be available.
Glaciers of the Sierra Nevada are the main source of the Sacramento and San Joaquin rivers. These supply water to the Central Valley, one of the most productive agricultural areas in the world, yielding more than 8 per cent of total US crops for export and home consumption. The importance of the Sacramento River is that more than 20 million people rely on it alone as a major source of drinking water.
Fortunately, the Sacramento River has its source in lakes fed by the Mt Shasta glaciers. As long as these glaciers continue to grow, water supply for major urban populations will be protected. The river will also remain navigable for ocean going vessels to the city of Sacramento, the State Capital and major port for exporting the abundant produce of the Central Valley. This of course assumes that atmospheric warming does not continue to the point where rain rather than snow falls on Mt Shasta’s glaciers - a big supposition.