SANITATION workers are trying to clear duckweed from waterways in Songjiang District to stop it entering the Huangpu River, Shanghai Xinmin Evening News reported yesterday.
Since last week, teams have been removing 400 tons of weeds a day, the report said.
The problem worsened after Tuesday’s heavy rains, which flushed more plants into rivers in the district, it said.
Two boats have been sent to Tongbo Pond, which connects the Huangpu to Dianshan Lake, where teams have set up 60 nets to catch the weeds.
June is the peak growing season for duckweed due to the warm and wet conditions.
Plants grow on the surface of the water and can double in size every 48 hours. They feed on nitrogen and phosphorous from sewage, absorb oxygen and kill fish.
Meanwhile, the water quality in the Huangpu and mouth of the Yangtze improved slightly last year, according to the latest Shanghai Environment Quality report, released on Wednesday.
The water quality in a sixth of the Huangpu is classed as Category III, with the remainder being Category IV, the document said.
Water quality at the mouth of the Yangtze was Category III, but Suzhou Creek was below Category V, it said.
Drinking water should be Category II or III, and water of Category V standard should be used only for agriculture.
The Shanghai Environmental Protection Bureau has made improving water quality its main task for this year.
To mark World Environment Day‚ which falls today, the bureau will collect samples from waterways and post the results on its website.
If the quality is substandard, the bureau will send a report to water affairs authority or district government.