Wednesday, June 16, 2010
Water is not distributed evenly over the globe. Fewer than 10 countries possess 60% of the world's available fresh water supply: Brazil, Russia, China, Canada, Indonesia, U.S., India, and Columbia. Less than 3% of the world's water is fresh - the rest is seawater and undrinkable. Of this 3% over 2.5% is frozen, locked up in Antarctica, the Arctic and glaciers, and not available to man and 0.5% Fresh water available. Thus humanity must rely on this 0.5% for all of man's and ecosystem's fresh water needs.
Since 1950 there has been a rapid expansion of groundwater exploitation providing: 50% of all drinking water; 40% of industrial water; and 20% of irrigation water. Over 5,000 km3 in man made storage facilities reservoirs. There has been a 7 fold increase in global storage capacity since 1950. 2,120 km3 in rivers - constantly replaced from rainfall and melting snow and ice.
As farmers, industry and people take too much water there is nothing left for nature. The concept of water stress is relatively simple: it applies to situations where there is not enough water for all uses, whether agricultural, industrial or domestic. Defining thresholds for stress in terms of available water per capita is more complex, however, entailing assumptions about water use and its efficiency. Nevertheless, it has been proposed that when annual per capita renewable freshwater availability is less than 1,700 cubic meters, countries begin to experience periodic or regular water stress. Below 1,000 cubic meters, water scarcity begins to hamper economic development and human health and well-being.
The four ways people contribute to water stress as follows-
1. Excessive withdrawal from surface waters: Over the past 30 years, the Aral Sea in the former Soviet Union has shrunk to less than half of its original size. The demise of the Aral Sea was caused primarily by the diversion of the inflowing rivers to irrigate water-intensive cotton and rice crops. This graphic shows the disappearance of the Aral Sea from 1957 to 2001. By 1987, about 60% of the Aral Sea's volume had been lost, its depth had declined by 14 meters, and its salt concentration had doubled.
2. Excessive withdrawal of water from underground aquifers: Along much of the west coast of India excessive fresh water abstraction has allowed sea water to enter aquifers thereby making the water so saline that it is unfit for human use. These consequences have been compounded due to excess irrigation water containing fertilizers and pesticides leaching into these aquifers.
3. Pollution of fresh water resources: Pollution can be so severe that the fresh water is no longer useable without incurring unacceptably high clean up costs. Pollution from many small paper mills using outdated technology has depleted the oxygen from the several river stretches in China, making them unfit for consumption by any form of life. China entered into a joint venture with a Finnish company to build a state of the art paper mill. China then closed the polluting firms and these rivers are making a remarkable recovery.
4. Inefficient use of freshwater: Poor irrigation practices, leakage in water delivery systems, inefficient use by industry and excessive consumption by individuals can all contribute to water stress.
Posted by Anurag Jain at 12:10 AM