Tibet's glaciers may disappear within 100 years due to global warming, threatening China's overused and polluted water supplies, the United Nations said.

``Almost all glaciers in China have already shown substantial melting,'' the UN Development Programme said in its 2006 Human Development Report. ``The 300 million farmers in China's arid western region are likely to see a decline in the volume of water flowing from the glaciers.''

Economic development in the world's fastest-growing major economy has increased competition for water resources, which are only a quarter of the world's average per person. Climate change is one of several threats to China's water supplies, including industrial pollution, overuse of chemical fertilizers and pesticides, and weak enforcement of environmental law.

Shortages of water from overuse affect 538 million people in northern China, where 42 percent of China's population is supplied by 14 percent of the country's water, according to the UN report.

More than 70 percent of the water in the Yellow, Huai and Hai rivers, which supply about half of China's population, is too polluted for human use, the report said. Half of China's rural poor live in the basin areas of these rivers, it said.

China needs to charge more for water use, and increase penalties for pollution to reflect the scarcity of the resource, Organization for Economic Co-operation and Development Deputy Secretary-General Kiyotaka Akasaka said last week in Beijing.

Industrial Accidents

China emerged as the world's fourth-largest economy last year after averaging 10 percent growth over two decades. Its government aims to cut energy use by 20 percent and reduce the discharge of major pollutants by 10 percent by 2010.

Still, China has experienced more than 150 incidents of water pollution because of industrial accidents since last November's explosion at a PetroChina Co. plant that dumped toxic benzene into the northeast's Songhua River, environmental Vice Minister Pan Yue said Nov. 9. Flawed implementation of central directives at the local level are to blame, as officials attempt to gain political clout by achieving high rates of economic growth, he said.

China's government plans to spend $125 billion with the aim of treating 70 percent of urban wastewater by the end of 2010, the Ministry of Water Resources said in August.

China should also remove subsidies for chemical fertilizer and pesticide for farmers, the OECD said in a Nov. 9 report. China's use of the substances per unit of production is as much as four times the average of OECD countries, it said.