GUANGZHOU - Plenty of water hyacinth has clogged a section of the Zhujiang River overnight in South China's Guangdong province.

On Sunday morning the section of the river running through Guangzhou, capital city of Guangdong, was blanketed by a mass of thick water hyacinth, a rapidly growing floating plant, which aroused people's concern about the quality of the river.

The river was very clear Saturday when the annual campaign "Swimming across the Zhujiang River" kicked off along the river.

A press conference was held by the city's environmental regulator to explain the inconceivable overnight change.

During the flood season, water hyacinth growing rapidly along the upper reaches of the Zhujiang River was swept to the lower reaches.

With the influence of the tide, it can hardly flow into the sea. Therefore, it was stranded in the section of Guangzhou on the lower reach of the Zhujiang River overnight, according to Zhi Wenguang, deputy director with the city's environmental management office.

Every summer, enormous quantities of water hyacinth are likely to clog some sections of the Zhujiang River.

The massive water hyacinth overlapping the river has little influence on the shipping in the Zhujiang River while it may cause troubles for some small boats, the provincial maritime affairs department warned.

Water hyacinth is a kind of water plant that can grow twice as much in just one week. Its overspreading can disrupt the waterway's ecosystems, make it unsuitable for shipping and fishing and might endanger the safety of drinking water.