water > features > nature's water "factories" under threat
Nature's water "factories" under threatPosted: 05 Aug 2005
Pollution, dam construction and climate change, are all combining to destroy watersheds and freshwater ecosystems at a rapid rate. But by putting a price on - and protecting these - "natural services", cities and rural areas can purify drinking water, alleviate hunger, mitigate flood damages, and meet other societal goals at a fraction of the cost of conventional alternatives, says a new Worldwatch study.
Global warming is the wild card that could further degrade the natural systems that safeguard our water supply, which could result in falling water tables, shrinking wetlands, vanishing species, and a decrease in both the quality and quantity of available freshwater, warns Sandra Postel, director of the Global Water Policy Project, and author of the study, Liquid Assets: The Critical Need to Safeguard Freshwater Ecosystems.
Pollution, population growth, and antiquated policies are contributing to the litany of serious impacts. Water management methods in the twentieth century have attempted to control and manipulate the hydrological cycle to best fit human needs with dams, diversions, levees, and reservoirs. While these engineering solutions help provide food, water, and electricity for many people, they have also severely disrupted the functioning of aquatic ecosystems.
|One dam already exists on the Theun River, upstream of the proposed Nam Theun 2 project.
(Photo courtesy Statkraft SF)
Some of the impacts mentioned in the report include:
Earth's water assets
- Dam construction: Over 45,000 large dams now exist, up from 5,000 in 1950. Dams affect over half of the world's major river systems and more than three-quarters of large river systems in the United States, Canada, Europe, and the former Soviet Union. Dams contribute to species and habitat loss, deter fish migration, destroy natural flow patterns, and alter water temperature and nutrient and sediment transport.
- Pollution: Increasing amounts of fertilizer, pesticides, heavy metals, and synthetic chemicals are being released into aquatic ecosystems, drastically altering the chemistry of lakes, rivers, and streams. These pollutants lessen the safety of drinking water, harm fish and wildlife, and lead to the spread of oxygen-depleted "dead zones."
- Greenhouse gas emissions: Climate change linked to the buildup of carbon dioxide and other greenhouse gases in the atmosphere is expected to shift rainfall and runoff patterns, melt glaciers and shrink snowpacks, and increase the number and intensity of floods and droughts. Some of these trends appear to be under way already.
Rivers, lakes, wetlands, and other freshwater ecosystems provide a myriad of services that are essential to human well-being. "Healthy watersheds are nature's water factories, and it pays to protect them," says Postel. "Forests and wetlands can churn out high-quality water supplies at a lower cost than conventional treatment plants do, while providing many other valuable benefits at the same time, from recreational enjoyment to biodiversity conservation to climate protection."
|Lake Butrint, Albania, a wetland site of international importance.
Prevailing water management systems are plagued by waste and inefficiency, placing unnecessary strain on natural water sources. It is common for cities to lose 20-50 percent of their water to leaks and other problems in the distribution system. Taiwan, for example, loses nearly 2 million cubic metres of water a day to leakage-roughly equal to 325 million toilet flushes. Governments and utilities continue to spend taxpayer and customer dollars on expensive dams and treatment plants while a third or more of their existing supply is leaking away. "It almost seems as if the point of public policy is to liquidate Earth's water assets like a store going out of business," says Postel.
By reducing waste and encouraging conservation, cities can leave more water in rivers and lakes, build fewer and smaller dams, pump less groundwater, and reduce the amount of energy and chemicals needed to treat and distribute their supply. Unfortunately, notes Postel, "in most cases, watershed protection remains the neglected stepchild of water supply systems, and conservation is relegated to drought-response at best."
Many forward-thinking cities and municipalities, however, are discovering that it is more cost-effective to employ nature's services rather than further destroy them:
- In 1997, New York City reached an agreement with local and federal officials, environmental organizations, and 70 towns to spend $1.5 billion over ten years on watershed protection and conservation measures, thereby avoiding construction of a filtration plant that would cost $6 billion to build and $300 million a year to operate. As of 2004, the city had invested more than $1 billion in the watershed program.
- Through successful conservation efforts, Bogot�, Colombia, has delayed the need to build new water supply facilities for at least 20 years. By protecting the natural filtering capacity of wetlands in its watershed, the city also keeps treatment costs low. Today, 95 per cent of households in Bogot� have potable water and 87 per cent have sewage services.
- Water use in the Boston metropolitan area hit a 50-year low in 2004 due to an aggressive conservation program launched in the late 1980s that has indefinitely postponed a proposed diversion of the Connecticut River, and has saved residents over $500 million in capital expenditures alone.
Strategies that value watershed protection are also key to alleviating hunger for the 852 million people suffering worldwide, mostly in poor farming regions. Rainwater harvesting methods coupled with affordable small-plot irrigation technologies are enabling poor farmers to boost crop outputs by using local water supplies more effectively. Better management of soils, water, and nutrients has quadrupled irrigated rice yields in parts of Madagascar, while also saving water. With 5 million children dying each year from malnutrition, equitable access to water for the poor is ever more crucial as governments seek to meet the UN Millennium Development Goals of reducing hunger, poverty, and child mortality.
Disaster mitigation is another area where watershed protection is crucial. "Distinguishing a natural disaster from a human-induced one is getting more difficult," notes Postel. While storms, droughts, floods, and tidal waves are natural events, the degree to which they produce disastrous outcomes is heavily influenced by human actions. The clearing of mangroves and destruction of other aquatic habitats make coastal communities even more vulnerable to erratic storm and flooding patterns, as confirmed by the Indian Ocean tsunamis of December 2004.
For the same reason people buy home and life insurance-to avoid catastrophic losses-societies need to "buy" disaster insurance by investing in the protection of watersheds, floodplains, and wetlands. Global warming and its anticipated effects on the hydrological cycle will make the robustness and resilience of nature's way of mitigating disasters all the more important, as tropical storms, spring flooding, and seasonal droughts increase in frequency and intensity.
"Today we are apt to think that our globalized and technologically sophisticated world is immune to societal collapse from ecological degradation," notes Postel. "But there is no side-stepping human dependence on the water cycle and we are disrupting it in dangerous ways."
Sandra Postel is director of the Global Water Policy Project and a Worldwatch Institute senior fellow.
Liquid Assets: The Critical Need to Safeguard Freshwater Ecosystems
See also: Wetlands shrinking