AGP - China - Water weeds
 

The problem of water weeds in China

By Lucky Amarasinghe and Ricardo Labrada

 

Introduction

The floating weed water hyacinth (Eichhornia crassipes)is a plant native to southern America, which was introduced into China as an ornamental plant from 1960 to 1980. Due to its rapid growth, it has been largely used for feeding pigs. However, with new developments in China for feeding pigs with other products, water hyacinth is not longer used. At this point, the plant proliferates and infests large areas of water bodies in China.  

Water eutrophication has become more intensive in recent years, and under this condition, water hyacinth grows much better and creates serious ecological concerns for agricultural production, fish production, navigation (an important traditional and efficient transport system), and the environment.

Water hyacinth is now among the ten most harmful weeds in China and found in 19 of the country’s provinces. Large infestations are localized in water bodies of the Yangtze River basin and south of this river. It infests reservoirs, lakes, rivers and channels, affecting negatively local water flora and is both polluting environment and hindering local economic development. For example, water hyacinth can grow in Huangpu river of Shanghai from April to October, producing a mass of about 1 840 000 tonnes in the river in 2002, but only 600 000 tonnes were removed, while the rest still covers the sub-rivers. It is a hard task to clean the river systems and not economically feasible. Water hyacinth in Pearl River of Guangdong has increased by ten times each decade. An average of only 0.5 tonne of the hyacinth was collected daily in the river in 1975, five tonnes per day in 1985 and 50 tonnes per day in 1995. Currently, water hyacinth that needs to be collected is almost 500 tonnes a day on average. About two thirds of the water surface areas of Dianchi Lake (Yunnan Province) are covered by this weed, which blocks navigation routes, creates breeding grounds for mosquitoes and flies, competes for oxygen with aquatic fauna and flora, and leads to economic losses for fish production.

According to statistics, the removal of water hyacinth consumes large amounts of labour especially in Zhejiang, Guangdong, Yunnan, Fujian provinces. The labour costs in Wenzhou (Zhejiang) and Putian (Fujian) in 1999 for water hyacinth removal were RMB 10 million Yuan and 5 million Yuan, respectively, while the total labour costs for water hyacinth control are more than 100 million Yuan each year for the whole country. Despite these huge inputs in terms of labour and funds for the removal of the weed, spreading in water bodies is not yet under control.

Hangjiahu Plain is located in the south of Yangtze River and in the north of Zhejiang Province. It is part of Taihu Lake Basin. The altitude of this region is about seven metres above sea level and in some places paddy fields lie between 1.7 and 4.7 metres above sea level. This region is not only one of the national key production centers for grains, mulberry, fish, livestock and rapeseed, but also an area with developed township enterprises and rural industry. There are many lakes, pools, ponds, water-channels and a network of river systems. The density of the river system network is 12.7 km/km2, with a total water surface area of
83 000 hectares.

 

Core Themes