Excessive nitrogen and phosphorus are the major water pollutants
in the Three Gorges Dam area, the 2007 Yangtze Conservation and
Development Report has said.
The report on the Three Gorges Dam, the largest hydro-power
plant in the world, was released at the second Yangtze Forum held
in Changsha, capital of central China's Hunan Province, over the
weekend.
"Nitrogen and phosphorus, which come mainly from domestic
disposals and fertilizers, account for 60-70 percent of the
pollutants in the Three Gorges Dam area," said Weng Lida, of the
Yangtze River Water Resources Protection Bureau under the Ministry
of Water Resources.
"Such pollution from non-point sources is very hard to control,"
Weng said. "If the pollutants had been discharged by a few plants,
they could have been moved out of the area. But nitrogen and
phosphorus are used by millions of people living there, hence, it
is difficult to ask them to stop using substances containing the
pollutants."
The excessive amount of nitrogen and phosphorus has caused
rampant growth of algae, which makes the water look like soy sauce,
Weng said.
Statistics show that in 2004, over 75,000 tons of nitrogen-based
and 25,000 tons of phosphorus-based fertilizer were used in the
area. Added to that were large amounts of phosphorus in detergents
used by millions of people living there.
There are no figures on the exact amounts of nitrogen and
phosphorus that flow into the Yangtze River in the area.
"Pollution has worsened after the Three Gorges Hydro-power Plant
started running," Weng said. "The water in the dam now flows at the
speed of 1 or 2 centimeter a second, as a result it seems almost
still. That to a large extent has weakened the river's
self-purifying capability."
The report warns against point-source pollution, such as those
from industrial plants, and floating-source pollution (from ships),
too. In 2004, for instance, the Three Gorges Dam area received
about 500 million tons of wastewater from industries, 2 million
tons from domestic sources and another 2 millions from ships.
(China Daily April 16, 2007)
