The world`s rivers are in crisis including North America and Europe where governments have invested trillions of dollars to clean up freshwater supplies, a study showed on Wednesday.
"Threats to human water security and biological diversity are pandemic," said Charles Vorosmarty of the City University of New York, co-lead author of the report in the journal Nature.
The international team of scientists estimated that almost 80 percent of the world`s population -- or about 5 billion people -- lived in areas with high levels of threat to water security, caused mainly by river mismanagement and pollution.
"Rivers in Crisis," Nature said on its front cover.
A map showed high levels of threat, in red, for much of the United States including the Mississippi basin, along with almost all of Europe. India, including the Ganges basin, and eastern China with the Yangtze River were also shown in red.
Rising wealth often meant worsening threats, for instance from badly sited dams or rising pollution from fertilisers, pesticides and other chemicals. Rich nations then covered up mismanagement by installing costly treatment plants.
The authors urged a re-think to safeguard rivers, especially those now less affected in developing nations. The world population is on track to reach 9 billion by 2050 from 6.8 billion now.
The study said it was first to examine in detail a twin set of threats -- to clean water supplies for people and to the biological diversity of life in rivers, from fish to crocodiles.
THREATS TO LAST
"Given escalating trends in species extinction, human population, climate change, water use and development pressures, freshwater systems will remain under threat well into the future," they wrote.
Least affected rivers were in parts of Siberia, Canada, Alaska, the Amazon basin or northern Australia, they said. Parts of the Amazon, the Congo and the Nile had low threats.
In rich nations, people often failed to grasp the underlying problems with water supplies because tap water was cleaned.
"In the industrialised world, the water management strategy is to patch up the problems at the end of the pipeline rather than the underlying causes," said Peter McIntyre, co-lead author at the University of Michigan.
The study urged other nations not to follow the rich which had invested trillions of dollars in managing rivers, ranging from dams for hydro-electric plants to building artificial barriers to allow cropland on flood plains.
"If your concern is flooding you might wish to preserve flood plains and wetlands in low-lying areas as they absorb the shock of floods," Vorosmarty said.
"That would obviate the need to build a flood containment system costing millions of dollars," he said.
In one positive example, New York City bought an area of the Catskills Mountains to help provide naturally filtered water, reckoning it cheaper than a water treatment plant.
The authors said that it might take decades to get politicians sufficiently engaged to fix the problems. "In the meantime, a substantial fraction of the world`s population and countless freshwater species remain imperilled," they wrote.