Researchers say Yangtze sandbank should become a wetland park

Work on the Biandansha Sandbank will ensure safety of the city's drinking water as well as preserve the ecological environment at the mouth of the Yangtze.
Ti Gong

A map showing the location of the Biandansha Sandbank, as well as the city's three major reservoirs.

A blueprint to turn a century-old Yangtze River sandbank near Chongming Island into a wetland park was issued at the weekend.

Protection of the Biandansha Sandbank, the name translates to shoulder pole due to its shape, can ensure the city's drinking water safety as well as better preserve the ecological environment at the mouth of Yangtze, according to researchers from East China Normal University and a Chongming District think tank.

The sandbank, a long and shallow stretch in the middle of the river, was formed around 1861 with the accumulation of sand and mud from upstream. The sandbank keeps growing and was divided into upper and lower parts in the 1980s.

It absorbs sand and mud from upstream and serves as a purification and protection barrier for the Qingcaosha Reservoir downstream, Shanghai's main tap water source for downtown residents, as well as the other two nearby Yangtze reservoirs, Dongfeng Xisha on Chongming Island and Chenhang in Baoshan District.

However, without proper treatment and control, the still expanding sandbank is expected to eventually connect with Chongming Island, making the reservoirs lose a protective barrier as well as endangering the many near extinct fish species in the waterway, Lin Tuo, a professor at the university and a UNESCO scientist told a seminar on Saturday.

Officials from the development and reform commission, and greenery, water and transport authorities, were also involved in the discussion of the blueprint.

Fourteen species of fish, crabs and snails have been discovered on or near the Biandansha Sandbank, including the Songjiang perch, a fish with four gills that had vanished from the city nearly 40 years ago due to over-fishing and pollution. The sandbank offers an important haven for the species, and the many migratory fish and the hairy crabs that rest there before heading upstream, said Lin.

The sandbank has also attracted many birds, including the rare reed parrotbill.

"The sandbank has become an indispensable relay for the long-distance migration of the species. The plants on the wetland of the sandbank supply essential nutrients while the waterway offers a safety channel to turn around," Lin said.

Once the sandbank connects with Chongming, migratory fish and crabs would find it difficult to complete their migration, which could lead to a major decline in their numbers as well as a worsening of the ecological environment at the mouth of the Yangtze, according to the blueprint.

The disappearance of the sandbank could also threaten shipping safety since the waterway nearby  currently serves as a busy shipping channel, Lin added.

The best way to protect and restore the sandbank is to develop it into a wetland park with more aquatic plants to stabilize it while dredging the waterway, said Mao Zhichang, a professor with the State Key Laboratory of Estuarine and Coastal Research at the university.

Upon completion, ferries can take visitors to the sandbank from either Chongming Island or the cruise liner terminal in Baoshan, said Yuan Lin, another university researcher. A pedestrian bridge could also be built to take visitors to the wetland park from Chongming, she added.

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