AMONG the 310 rivers in Shenzhen, more than half of them (173) are black, polluted and smelly, though authorities started treating the water a decade ago, an investigative report of Shenzhen Evening News said yesterday.

    Almost all the rivers are seasonal and only five of them — namely the Shenzhen River, Guanlan River, Maozhou River, Longgang River and Pingshan River — cover an area of more than 100 square kilometers. Limited rainfall and large amounts of sewage discharged into rivers without being treated are blamed as major factors of the pollution.

    The lack of sewage pipelines to collect wastewater for treatment is another reason for worsening water quality.

    The city has built 4,268 kilometers of sewage pipelines and is still facing a shortage of 4,600 kilometers. Around 932,000 tons of wastewater is being discharged into rivers every day without treatment.

    The Maozhou River, the longest in Shenzhen, is also the most heavily polluted river in the Pearl River Delta region, according to the report. This is primarily due to the 250 industrial enterprises along the 41.6-km river, which borders Shenzhen and Dongguan.

    The main stream of the Maozhou River and its 15 major tributaries were given Grade V standards for water pollution on average (only Grade I and II water can be used as drinking water sources, according to regulations).

    Filled with floating trash, stinking of sewage and darkened to a shade of black, the Maozhou River is called the “black river” by Shenzhen residents and is most polluted in its tributaries, which are filled with construction sewage and other waste accumulated from nearby industrial complexes. The 250 factories near the river are well-known for heavy polluting, and the region’s large population of migrant workers has kept the factories in business and done little to stem the tide of pollution.

    Shenzhen decided last year to spend 1.93 billion yuan (US$313 million) on an extensive cleanup of the Maozhou River that’s scheduled to be finished in 2015.

    The Maozhou River Rehabilitation Project is part of a larger Guangdong Clean Water Action Plan designed to improve environmental conditions in the Pearl River Delta region.

    The cleanup includes two water treatment plants, one in Gongming and one in Shajing. The two plants, along with other existing plants, have a capacity of handling 900,000 tons of polluted water a day. A 124-kilometer sewage pipe will be built in Guangming to treat wastewater and other refuse.

    (Han Ximin)