New 杏吧原创 has reported that rivers in the Himalayas will be starved of water when the glaciers disappear. If the glaciers were neither shrinking nor growing, the amount of water fed into the rivers from the glaciers should be roughly equal to precipitation in the Himalayas over the same period. Assuming that rainfall remains the same when the glaciers are gone, why shouldn鈥檛 the rivers still receive the same amount of water?
鈥� The water in a river does not depend only on the amount of water that falls as rain in a year, but also on when and how much. Generally, glacier-fed rivers will receive a constant trickle from melting ice in the winter and, as the temperature rises in spring, the amount of water in the river increases.
If the glaciers disappear, there will be no slowly melting ice, so the glaciers鈥� regulation of the water flow will cease. Any rain that falls will instead reach the river rapidly, while in dry spells there will be no water at all. So, instead of having a river all year round with a flow rate that is strongly linked to temperature, you will have a much lower water level most of the time with higher levels after rain. The average level over the year will indeed stay the same, but in extreme cases it could mean the difference between a constant flow and a dry river bed with occasional flash floods.
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鈥淎ny rain that falls will reach the river rapidly, while in dry spells there will be no water at all鈥�
That compares the case of no glaciers with the case of constant glaciers. In reality, glaciers have been losing mass since the end of the last ice age. Once all the ice has melted there really will be less river water available, so the average level will be lower and more erratic.
Rick, Didcot, Oxfordshire, UK
鈥� Glaciers act as reservoirs that even out the flow of water so that a given year鈥檚 precipitation takes generations to reach the sea. Without glaciers to regulate the flow, a rainy season鈥檚 precipitation 鈥� potentially all of that year鈥檚 rain 鈥� could flood down within months, leaving devastation and eroded canyons for the rest of the year. The glaciers鈥� buffering effect is huge.
Jon Richfield, Somerset West, South Africa