Water Source & Sustainability

Topics: Water, Water resources, Hydrology Pages: 5 (1771 words) Published: February 4, 2011
Water Water Everywhere
There is more than 1.4 billion cubic kilometres of water on the earth. If divided evenly enough to give every man, woman & child 230 million cubic meters. However 98% of that is saltwater and nearly 1% of it is locked as polar icecaps. Less than 1 percent of the Earth's freshwater is accessible in lakes, rivers, and groundwater aquifers. This vital 1 percent of available freshwater is con- stantly in motion, either flowing in rivers, evaporating and moving around the globe as water vapour, falling from the sky as rain or snow, or filtering slowly through the earth to emerge somewhere else. It is a renewable resource on which we all completely depend upon. It is the genesis and continuing source of all life on earth.

The most accessible water is that which flows in river channels or is stored in freshwater lakes and reservoirs. The major portion of the water diverted for human needs is taken from this renewable, readily accessible part of the world's freshwater resources. Although the total volume of water conveyed annually by the world's rivers is about 43,000 km3, most of this occurs as floods. The low river flows (base flows) make up only about 19,000 km3. Of this, about 12,500 km3 can be accessed, and present levels of withdrawal accounts for 4000km3. This withdrawal is expected to reach 5000 Km3 per year by the 2025. The demand for freshwater increased six-fold between 1900 and 1995 nearly twice the rate of population growth. One third of the world's population today already live in countries experiencing medium to high water stress. Water Stress

Water stress for a river basin is defined as the water resources available in that basin. The water stress for a country is the summation of water stress for all its river basins. Water stress begins when the withdrawals of water of freshwater rises above 10 percent of renewable resources. Medium to high stress translates as water use that exceeds 20 percent of available water supply. Countries experience high water stress when the ratio of water use to supply exceeds 40 percent. At such levels, their patterns of use may not be sustainable, and water scarcity is likely to become the limiting factor to economic growth. High water stress and unsustainable rates of withdrawal are already being experienced in Central and South Asia, where annual water withdrawals compared with available water resources are 50 percent or more. In the dry season, water scarcity occurs throughout Asia and the Pacific, and increased rainfall variability as a result of global climate change will worsen this problem. Water scarcity will affect food security throughout Asia and the Pacific. The global population will expand from today's 6 billion people to almost 8 billion in 2025. By then, more than 80 percent of the world's population will be living in developing countries. The World Meteorological Organization estimates, assuming the renewable water resources will remain unchanged, that the number of countries facing water stress will increase from 29 today to 34 in 2025. How these countries manage their water resources, and whether they can produce sufficient food for their growing populations while catering to their water needs and preserving natural environments, have important implications. Nearly 70 percent of global freshwater withdrawals are directed toward agriculture, mainly for irrigation. By some estimates (UN 1997), annual irrigation water use will have to increase about 30 percent above present use for annual crop production to double and meet global food requirements by 2025. The industry sector, which accounts for about 22 percent of current freshwater withdrawals globally, is likely to require an increasing share in all regions of the world. In developing countries, where 56 percent of the population will be living in urban areas by 2025, the share of water going toward domestic uses will also need to grow substantially.

Asia and Water
Asia has the...
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