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Nadia
Joined: Apr 2, 2003
Posts: 4
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Country: Greece
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Water and Sustainable Development
July 29, 2003 - 04:53 AM
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The essence of sustainable development is that natural resources must be used in ways that will not limit their availability to future generations. Sustainable development of water resources requires that we respect the hydrologic cycle by using renewable water resources that are not diminished over the long term by that use.
Today, however, most easily accessible renewable fresh water resources--rivers, smaller streams and lakes and aquifers that recharge quickly--already have been developed. The cost of developing less accessible ones will be high and the process time-consuming. The environmental and human costs of projects can also be enormous. Egypt's Aswan Dam--while providing multiple benefits to farmers and others--covered priceless archeological sites, destroyed valuable ecosystems and fishing grounds, eroded beaches and damaged nutrient and sediment balances. China will pay over $3.2 billion to resettle the estimated 1 million farmers and villagers that are expected to be displaced by the planned Three Gorges Dam on the Yangtze River.
Transfers of water from one river basin to another, used for example to balance regional water supply and demand in the western United States, are generally prohibitively expensive across national borders. Schemes such as one to transport water from rivers in Alaska and Western Canada over the Rocky Mountains to water-poor states in the United States and northern Mexico have stalled because of excessive costs, technological obstacles and environmental risks.
The growing use of fossil fuels to pump water from deep underground aquifers is dramatically expanding access to fresh water today--but at the cost of access in the future. There is nothing inherently unsustainable about the use of groundwater per se; people have been drawing water from wells since the earliest civilizations of the Fertile Crescent. But to ensure that wells provide as generously next year, or next century, water must be drawn at a rate that permits water table levels to remain stable over time. The rate of sustainable water use is determined not by human needs but by the laws of nature.
Although all natural water resources are replenished through the natural hydrologic cycle, their renewal rates range from days to millennia. For rivers, renewal rates average 18 days; for large lakes and deep aquifers they can span thousands of years.
The world's oldest water reserves, such as the Nubian aquifer in North Africa, were filled when water infiltrated the earth's subsurface in past geologic ages. Because it is questionable when, if ever, "fossil" water from such aquifers will be replenished, drawing significant amounts of water from them is by definition unsustainable, and their use cannot be more than a temporary solution to water scarcity.
What do you think?
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