BEIJING (AFP) - Seventy percent of the Chinese capital's rivers are severely polluted but authorities hope to improve water quality ahead of the 2008 Olympic Games, state media said.

A government study conducted last year found that 56 of 78 rivers monitored in Beijing failed to meet water quality standards, the Beijing News said.

Forty-seven of the rivers, comprising 838 kilometers (519 miles) of waterways, were heavily polluted with toxic substances such as ammonia.

In the Liangshui and Beiyun rivers, the pollution is so serious that the water is black and emits a foul odor, the report said.

Many of the city's lakes are also cesspools, with one-third of its 19 lakes suffering from serious pollution, the report said.

Beijing's environment protection department, which announced the findings, said the city will treat the cleaning up of its waterways as a high priority ahead of the 2008 Olympic Games.

Some of the waterways to be targeted will be used for Olympic events, such as rowing and canoeing competitions.

Prior to 2008, the city plans to build 700 kilometers of pipelines for diverting wastewater in order to reduce direct discharge of factory pollutants and other wastewater into rivers and lakes, Beijing News said.

Industrial parks will also be forced to set up wastewater treatment facilities before they can carry out production that generates polluted water.

The department said Beijing's water quality will "basically" meet national quality standards by 2010.

On one positive note, the study found that the city's drinking water supplies, such as the reservoirs, met national standards.

Beijing's problems reflect a nationwide challenge. More than 70 percent of China's rivers and lakes are polluted, while underground water supplies in 90 percent of Chinese cities are contaminated.