GUIYANG - The Chinese government will enhance monitoring of drinking water sources, control poisonous contaminants and step up early warning mechanisms to ensure drinking water safety, an environmental official told an ecological forum that concluded on Sunday.

Ling Jiang, deputy director of the pollution prevention department under the Ministry of Environmental Protection, said that although 95.3 percent of the monitored drinking water sources in 113 major cities across China met national standards last year, people should not be too optimistic about the situation.

China has no special national standards to monitor drinking water sources, according to Ling.

The figures were obtained from 387 drinking water sources in the 113 cities and by testing only about 20 indicators based on surface water standards. "Some harmful and poisonous contaminants for drinking water were not included," he said.

"We can not conclude that the water sources are of good quality only because these routine indicators meet the criteria," Ling said.

Aside from setting down national standards, the ministry plans to expand monitoring points and include more indicators in the future, according to Ling.

The ministry also plans to take measures to get a more clear view of the quantity and quality of the country's underground water and set up a sound pollution prevention mechanism for underground water within five years, he said.

Ling said the government aims to enhance control of poisonous contaminants from sources of pollution, especially the chemical industry, which has seriously threatened drinking water sources.

"It, however, will be extremely difficult for the government to trace and monitor chemical products from production, transportation to usage," he said.

Last month, the country's supreme court and procuratorate jointly issued a new judicial explanation aimed at easing difficulties in investigating environmental pollution cases and convicting polluters.

Discharging, dumping or treating radioactive waste or waste containing infectious disease pathogens or toxic substances into sources of drinking water and nature reserves will be considered crimes of polluting the environment, according to the document.

"Compared with administrative punishment, the judicial document will increase the costs of environmental pollution, which was previously believed to have been too low to curb polluting activities," Ling said.

The outlook on the quality of China's water sources is "far from optimistic," according to a report released by the Ministry of Environmental Protection last month.

The quality of underground water in 57.3 percent of the 4,929 monitoring points in 198 cities around the country is "relatively poor" or "extremely poor." In addition, the resources in about 30 percent of water monitoring points in major rivers was of poor quality, according to the country's surface water standards.

Environmental pollution scares have popped up across China in recent years.

In March, thousands of pig carcasses were discovered in the Huangpu River, which provides 22 percent of Shanghai's tap water. The incident raised significant concerns, despite local authorities' attempts to reassure local residents about the safety of the water.

Liu Changming, a hydro-engineer and academician with the Chinese Academy of Sciences, said Chinese cities are facing an imbalance in water supply and demand, expanding pollution and excessive use of underground water after about three decades of urbanization.

The government should intensify management and control of water, remedy nonpoint source pollution, allocate water supplies in a more scientific and rational way, and selectively develop water supply sources, he said.