Wetland can improve water quality of reservoir

Shanghai is restoring a wetland ecosystem around the Qingcaosha Reservoir, the main source of drinking water for the city's 13 million-plus residents.

Experts noticed signs of eutrophication – excessive nutrients in a lake or other body of water due to run-off of fertilizers and sewage from the land – in the country's largest reservoir earlier this year.

The reservoir also faces the threat of saltwater intrusion from the East China Sea during certain months of the year.

The city's water authority has done some experiments to reduce the growth of algae in the reservoir by restoring wetland around the reservoir and introducing algae-eating fish.

"We face constant pressure from upstream pollutions," said Shen Yichen, general manager of Chengtou Raw Water Co, the operator of the reservoir.

More than 20,000 monitoring items are collected each day from the reservoir, which provides 80 percent of tap water to downtown districts, Shen said.

The city is also looking for new water sources by building reservoirs further upstream, for instance, in the Taihu Lake, instead of pumping water directly from navigation channels, water officials said.