Monday, December 8, 2008

Water, water everywhere.....

How is water related to energy?
For a start, the sun's energy sets the water cycle into motion. Perhaps more important is that climate change will likely lead to accelerated melting of glaciers which feed many of the Himalayan rivers such as the Indus, Ganges-Brahmaputra and the Yangtze. The Gangotri glacier shown in the figure to the left is the source of the Ganges. Therefore, climate change (greenhouse gas emissions) would directly affect ~1.3 billion people who live in the drainage basin of these Himalayan rivers. The first figure shows regions of the world which are currently facing water scarcity. As defined by the "Water for food Water for life" study, economic water scarcity occurs when human, institutional and financial capital limit access to water even where water is available locally. Physical water scarcity occurs when more than 75% a region's river flows are withdrawn for agriculture, industry, and domestic purposes. I am particularly interested in sub-Saharan Africa, South Asia and China, as these are the major population centers where water scarcity is prevalent. (An interesting way to visualize this is shown on the worldmapper site).

    The IPCC Technical Paper VI projects that:
  • The per capita availability of fresh water in India will drop from 1820 m3 currently to 1000 m3 (yearly basis) as a result of population growth and climate change. In comparison, the global average by 2025 is expected to be ~5000 m3. India's population will therefore be using 1/5th of the world average per capita water consumption.
  • More intense precipitation in Asia would result in a higher runoff and reduction in the portion recharging the groundwater aquifers.
  • Agricultural irrigation demands in arid and semi-arid regions of east Asia would be expected to increase by 10% for a 1 degree C increase in temperature.
  • Changes in snow and glacier melt will cause seasonal shortages and affect 1/4th of China's population and hundreds of millions of India's population. (~0.3-0.6 billion combined).
  • Arid and semi-arid land in Africa would increase 5-8% by 2080.
  • Current water stress in Africa will likely be increased by climate change.
  • Any changes in the primary production of large lakes (Lake Chad, Lake Tanganyika) will have important impacts on local food supplies.

My perspectives: Economic water scarcity is another dimension of the "Water, water everywhere.." problem. Low-cost means to treat water and responsible aquifer management are required to overcome economic water scarcity. Physical water scarcity will need similar measures, and various end-users (farmers, industry, households) must be encouraged to conserve and recycle where possible. Farm subsidies for water-intensive crops (ex: sugarcane, paddy), will likely have significant impacts on water conservation and scarcity. Balanced policy planning is therefore required to manage local, regional and national water resources. Finally, regional cooperation, as outlined in an earlier post will be necessary to ensure equitable distribution of water resources among different stakeholders.

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