Pollution of Lake Tai, China

Problems

• Water pollution in theTai Lake basin

  Lake Tai, also known as Taihu, is China’s third-largest freshwater lake and one of its most important water resources. The 2,400-square-kilometre lake in south China is the source of the Suzhou River. It also feeds the Huangpu River, the waterway along Shanghai’s Bund, perhaps the country’s most famous riverfront.
  
  Since the 1980s, the lake has experienced dramatic water quality degradation associated with rapid land development and the developing economy. The water quality is poor, and three northern bays suffer from annual algal blooms, which increase the cost of water for purification. 

• Causes of pollution

  Many factors contribute to the pollution in the Tai Lake basin. Industrial development is one of the most important aspects.  China enterprises have sprung up and developed rapidly, including the chemical, melting and dyeing industries around the lake. The industries had backward technology and low-efficiency environmental management, which caused heavy pollution around the Lake Tai basin. 
  
  Another factor is rapid population increase resulting in a large amount of Municipal discharge. Since the Lake Tai area is one of the most developed areas in China, it has with high urbanization level. According to a Jiangsu Provincial Environmental Protection Bureau (EPB) document, there are 127 functioning sewage treatment plants around the Taihu watershed combined to treat 3 million tons of sewage water daily. However, their actual treatment rate is 1.98 million tons, so wastewater treatment plants around Taihu are not fully utilized.
  
  Taihu is historically a very rich and fertile area, and many types of farming are widespread. According to a Nanjing Agricultural University study, 60 percent of Taihu's organic pollution can be attributed to agriculture—40 percent of which originates from aquaculture. Land-based agriculture also has been a significant contributor to Taihu's pollution, particularly as farmers, fearful of counterfeit chemicals and paper-thin profit margins, apply chemical fertilizers and pesticides.

• Impact of pollution

  Heavy pollution from industry, municipal, and agricultural sectors has created a eutrophic lake—a condition resulting in low oxygen levels and often measured in COD—at a "medium level." Eutrophication results in loss of biodiversity as many creatures, particularly bottom dwellers, cannot withstand the low and fluctuating levels of oxygen. Algae prosper under these conditions when the water is warm. 
  
  Toxic varieties of algae present a variety of threats to human health by damaging the liver, intestines, and nervous system. Additionally, the toxins can accumulate in fish and shellfish, becoming dangerous to humans who eat those animals. Consuming water contaminated with toxic algae can lead to diarrhea and liver failure.
  
  A large bloom of blue-green algae in Taihu Lake caused water quality to deteriorate severely in 2007. Despite the local water department’s attempts at mitigating the crisis, the water supply to a great number of households was contaminated, the water becoming putrid and very unpleasant to drink. Tap water turned yellow and foul. Drinking water for two million Wuxi residents was polluted. Since then, algal blooms have happened every year despite major government efforts to clean up the lake.
  
  In fact, policymakers were well aware of Lake Tai’s pollution problem long before the 2007 algal bloom. As early as 1991, the state launched its first project to clean up the lake and, over the subsequent 10 to 15 years, invested more than 10 billion yuan (US$1.6 billion) in the effort.
  
  Pollution in Taihu has been discussed at all levels of government and in the news for many years, yet the topic remains highly sensitive in China. Several measures and projects have been put in place over the years, including the central government measures and international initiatives, with positive results. Pollution remains a big problem in the Lake Tai basin.