Water-Wise: On Glaciers And Climate Change
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The link between climate change, glaciers and water security works in the following way. A rise in global temperatures leads to warmer winter temperatures. On the other side, average summer temperatures also increase. Both these conditions cause higher melting and lesser new ice formation in glaciers. The net effect is that glaciers begin to retreat. Retreating glaciers lead to changes in water availability for communities that rely on glacial sources e.g. rivers fed by glacial melt for drinking water.
The state of glaciers is one indicator of climate change. It is studied through mass balance measurements. The mass balance of a glacier is the difference between the amount of glacial ice mass formed during winter and the amount of melting that happens in summer. A positive mass balance is when there is more formation than melting. A negative mass balance is when there is more melting and less formation of new ice. A healthy glacial system would ideally be one with a positive mass balance. A glacier could be said in retreat or at risk of being lost if the negative mass balance continues.
In its special report on the ocean and cryosphere in a changing climate, the Intergovernmental Panel on Climate Change (IPCC) includes data on glaciers worldwide. The chart below shows glacier mass budgets for eleven mountain regions assessed by the IPCC. The mass budget is measured in kg per metre square per year and mm sea level equivalent (SLE) per year.
The implication of this trend is that water availability in mountainous regions will change significantly, perhaps with erratic flows. The habitations in the mountains and downstream regions rely on glaciers for their water supply. If the glaciers are to retreat, water availability for the communities will be threatened.
In Nepal, one of the countries where Frank Water works, a major urban water supply project of the government – Melamchi Water Supply Project, depends on glacial flows for its source. The WASH needs of the Kathmandu valley that are currently met by the project will be directly impacted if the upstream glacier continues to retreat.