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Cities battling unwanted water life

By Qian Yanfeng in Shanghai, Qin Zhongwei in Beijing and Zhan Lisheng in Guangzhou (China Daily)
Updated: 2009-06-19 09:15

Authorities in Shanghai are fighting to rid the city's waterways of duckweed, a green aquatic plant that multiplies in polluted waters, and warned the eyesore will spread rapidly in the coming months.

Massive stretches, estimated at about 390,000 sq m, in the upper reaches of Huangpu River in suburban Shanghai's Jinshan, Qingpu, and Jiading districts, are covered with the floating plant, which has found a home in the water body for the second consecutive year.

Yu Hai, spokesman for the municipal city appearance and sanitation administration, said the plant is not a threat to the city's supply of drinking water.

"Unlike the blue-green algae, duckweed does not discharge toxics into the water. It's more of a visual pollutant."

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The Huangpu River accounts for about 70 percent of the city's drinking water supply.

Latest data from the municipal environmental monitoring center showed the drinking water source on the upper reaches of the river had not yet been affected.

Yu blamed the increasing presence of chemical nutrients like nitrogen and phosphorous in the water for feeding the water plant.

Once the rainy season starts by the end of this month, summer heat and humidity will likely accelerate the growth of duckweed, Yu said, adding the authorities would leave no stone unturned to free the Huangpu River of the plant.

Yu warned that as the temperature decreases in September, the water hyacinth, a water species that grows rapidly and blocks waterways, is likely to emerge again this year and will not go away until the month of January.

Yu said pollutants from the tributaries in the neighboring Jiangsu and Zhejiang provinces have also contributed to the pollution of the Huangpu River.

"Cleaning up our water bodies will take concerted efforts from various governments," he said.

Further south in the city of Guangzhou, capital of Guangdong province, authorities are struggling to uproot stretches of water lettuce, floating in the city's rivers, ponds and reservoirs.

Water lettuce, academically known as pistia stratiotes, is an aggressive free-floating plant with many spongy, dusty green leaves, which can form thick mats atop water bodies.

The mats, once covering the entire surface of the water, can cause oxygen depletion and kill fish.

"Water lettuce has been more unbridled than ever before. We have flagged off some 700 boats to pull the plant out of the water and have set up five posts to watch its formation at several legs of the Pearl River," said Liu Yueren, an official with the municipal environment and sanitation administration of Guangzhou.

Last month, authorities pulled out over 400 tons of water lettuce from the Pearl River in just five hours, Liu said.

"We will soon put together a special team of 80 members to keep a close watch on the water quality of the city's water bodies and will come down heavily on those who release wastes and pollute the water," he said.

Zhao Huanmin, a botanical postgraduate at the South China Agriculture University, said: "Industrial wastewater and living sewage combine to create a hotbed for water lettuce."

Algae invading Qingdao

Qingdao authorities are racing to think of ways to fight a thick algae cluster fast approaching the coastal town.

According to the latest satellite observation tracking the flow of the algae, the north side of the cluster, covering an expanded area of 140 sq km, is only 62 km from Dagong Island, south of Qingdao.

The cluster is flowing northward at a speed of 8-11 km per day, China National Radio said on Wednesday.

Fearing the algae will contaminate the water and block sea transportation, Wang Shulian, vice-chief of the local oceanic administration, said 20 ships were "ready to weed off the green stuff".

The local government has already raised the alert level to three.

An official from the anti-algae emergency office in Qingdao, who would not be named, said the sea algae blanket was a "natural disaster".