A diesel spill from a ruptured pipeline in northwestern China has seriously contaminated two rivers that finally flow into the Yellow River, the country's second longest waterway, a local official said Monday.

The Chishui and Weihe rivers were seriously contaminated after some 150 cubic meters of diesel leaked early Wednesday from a ruptured pipeline belonging to the China National Petroleum Corporation (CNPC), the country's top oil producer, Li Xiaolian, vice director with the Shaanxi Provincial Environment Protection Administration, said at a press conference.

However, contamination to the Yellow River remained under control and its water quality was still within the state standard, he said.

The leak occurred in Huaxian County in Shaanxi, about three km away from the confluence of Chishui and Weihe rivers and 70 km upstream from the Yellow river.

The CNPC had dug a 100-meter-long channel at the source of the leak to divert uncontaminated water.

Statistics from a monitoring station in Tongguan County, where Weihe River joins the Yellow River, indicated Monday morning that each liter of the water contains about 0.79 mg of oil-like substance, still below the national limit of 1 mg per liter.

The figure showed continuous declining of oil substance in the water compared to the 1.78 mg concentration reported Friday noon at Tongguan.

Nine such stations have been set up along Chishui and Weihe rivers to continuously test water quality.

(Xinhua News Agency January 4, 2010)