Floodwater sluiced from nearby rivers is introducing pollutants
into Shanghai's water resources, but tap water in the city remains
safe.
Shanghai Water Authority said yesterday that a high content of
harmful substances - ammonia, azote and nitrite - has been detected
at the intake spots of Shanghai's two reservoirs on the Yangtze and
Huangpu rivers.
The pollution is caused by floodwater sluiced from nearby
rivers. The city's drinking water remains safe due to carefully
choosing the intake times from the reservoirs and increased levels
of water sanitation.
The Shanghai water authority said it has been closely monitoring
the water quality in nearby water channels, especially following
the onset of flood season and the outbreak of blue-green algae in
Taihu Lake. The growth of algae shut down the city of Wuxi's
drinking water supply for a week.
Continuous downpours, which started last month, have brought
floods, landslides and death to several provinces.
Liuhe River in Jiangsu Province, with floodwater from Taihu Lake
and other water channels from Suzhou, has been pouring large
amounts of polluted water into the part of Yangtze River near
Shanghai.
A sampling on Tuesday at the intake spot of Chenhang Reservoir,
which is 4 km from the Liuhe and Yangtze rivers, found the ammonia
and azote content more than 20 times higher than usual but still
within acceptable standards. The Chenhang Reservoir contributes
one-third of the city's water supply.
The other reservoir in the upper reaches of Huangpu River, also
connected to Taihu Lake, was also found to have nitrite higher than
standard at its intake spot. The nitrate is mainly from
agricultural and industrial waste dumped in nearby rivers,
according to an expert quoted by Shanghai Morning Post.
To safeguard Shanghai's tap water, city water companies have
adjusted their intake hours to avoid low tide, when pollution is
comparatively higher. They have also extended the chemical
precipitation period and added chemicals when necessary.
(China Daily July 12, 2007)
