LONDON, March 21, 2006 (RFE/RL) -Will humans destroy their rivers in a few decades?
Some scientists are increasingly asking this question, because several world rivers are already being drastically overused, almost drying up before they reach the sea.
Dr. Gwen Rees, principle hydrologist at Britain's Center for Ecology and Hydrology near Oxford, cites China's Yellow River as a particularly striking example.
Dramatically Increasing Demands
"I think the evidence speaks for itself," Rees says. "If you look at the rivers, the Yellow River is a good example where I don't think the river reaches the sea anymore. That I believe is down to the fact there are huge human demands for the water upstream. For crops, for industry, for drinking water."
Rees says that industrial activity, and demand for drinking water, have been increasing dramatically in China over recent decades. And he says the reduction in river flow cannot be explained by other causes scientists might look for, such as climate change.
"These changes that we're seeing in river flows, declining in river flows, I don't think can be attributed to climate change," he says. "I think they are more [related] to the human demand for water, the overexploitation of water resources by people, the unregulated water use or poor regulation of water use."
Irrigation Increases Evaporation
River flows can increase or decrease depending on whether winters are warmer or cooler, enlarging or shrinking the glaciers that form a river's source.
Rees says the problem is partially caused by the overuse of river water for agriculture. Simply because the water in irrigation channels largely evaporates instead of returning to the river.
The same applies to various industrial uses, further weakening the river flow. Rees points out that the sewage mixture downstream is no longer a river, and it has no value for other potential users, not to mention ecology and wildlife.
Eye On Central Asia
Professor David Collins of the University of Salford in England agrees. He says much the same situation can be seen in Central Asia.
"In the Syr Darya and Amu Darya rivers flowing towards the Aral Sea, river flow has declined substantially downstream," Collins says. "This is not a natural climatic-fluctuation effect, but more an effect, which has been brought about by the overconsumption of water from those rivers for irrigation. In particular for the growing of cotton, which uses a great deal of water."
A satellite image of the shrinking Aral Sea (epa)
Collins says that this is one area where the river flow from the glaciers of Tian Shan is expected to diminish in the longer term, not being able to sustain current levels of overconsumption for future generations.
One solution is building dams and reservoirs to retain water, but it is often an issue that leads to tension between countries through which such rivers flow, Collins says.
"The diversion of water into and retention in dams to affect river flow downstream is fairly common, and often has an international dimension," he says. "The Jordan [River] being an example, as well as the rivers in the Middle East, such as the Euphrates and the Tigris."
Collins explains that the restoration of the marshes on the two main Iraqi rivers is already showing significant ecological benefits, while a dispute over dams upstream in Syria and Turkey continues.
Cross-Border Water Disputes
And he says there are other overuse disputes elsewhere, including the Rio Grande that forms a border between the United States and Mexico, or between India and Bangladesh over the Ganges.
These disputes, Collins concludes, will have to be solved constructively in order to prevent looming water crises.
Rees concludes that the world should perhaps follow the example of the European Union, where the rivers are being strictly monitored, and all member countries must adhere to a special piece of legislation called the European Water Framework Directive.
That forces river-basin and water authorities and companies to apply an integrated water-resources management to preserve good ecological status of rivers for the future.