China's environment authority Tuesday introduced emergency measures to ensure water supplies to those living along the Yellow River.

The move comes as water shortages reach their worst in more than half-a-century and massive pollution seriously threatening the nation's `mother river.'

Under the emergency plan issued by the State Environmental Protection Administration, the discharge of waste into the Yellow River by cities along its shores between Longmen in Shaanxi Province, and Huayuankou in Henan Province, will be strictly governed.

When the water flow is less than 470 cubic metres per second at the Huayuankou section, local environmental authorities will issue warnings and adopt precautionary measures.

In particular, special attention will be paid to potentially polluting industries, such as those of medicine, smelting and paper making and also civil sewage treatment plants, to ensure no improperly treated waste is discharged directly into the river.

"Those found to have breached the regulations during times of emergencies, will either be closed down or have their production scale reduced,'' said Liu Guozheng, a leading publicity official with the administration.

Periods classified as "emergencies'' will come into effect when the water flow at a particular section is less than 250 cubic metres per second.

Liu said the waste control measures were necessary because this year's reduced water levels in the Yellow River, combined with a lack of effective pollution curbs are likely to endanger the quality of drinking water supplies for those in the middle and lower reaches of the river.

While the ineffectively checked pollution of the Yellow River has much to do with the steadily growing economy along its banks, resulting in increased industrial and civil waste, Liu admitted it also had something to do with slack supervision.

For example, a national campaign several years ago succeeded in improving the water quality of the river. It reduced the number of small mines, paper and smelting plants in its upper reaches, whose backward technology and shabby production methods made them major polluters. But despite the clampdown a number of the polluters are back in business.

Therefore, said Liu, it is essential to improve supervision, especially in those designated "key pollution control areas,'' which include five river valleys and 12 medium to large cities.