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Animal Waste turns Chinese lake green – Eutrophication

Animal husbandry is contaminating China’s water and has been linked to turning lakes bright green, a phenomenon known as eutrophication.

The farm, located at the end of a narrow dirt path, announces its presence with a piercing stench. At first, the caretaker of the collective facility in Kunming says the farm recycles all the animal waste into manure fertiliser. But later, he sheepishly points behind the pigsty.  There, hordes of flies swarm above a festering field of grey-black dung. A few times a month, Cai shovels the steaming excrement produced by some 100 swine owned by local families into a nearby creek, where a mile downstream, villagers fish on the rocky shores of a small lake.

The hilltop fishing spot feeds into Dianchi Lake in south-western Yunnan province, a major tourist attraction and one of China’s largest fresh water bodies. Dianchi is famous for a number of reasons: its sheer size (nearly 40km long), its distinctive “crescent moon” shape and the surrounding scenic hills and rock gardens. But it has another distinguishing feature; for several decades, each summer the surface of Dianchi has turned bright green from algae blooms caused by excess nutrients such as nitrogen and phosphorus – a largely manmade phenomenon known as eutrophication.

Eutrophicationplagues areas around the world where rapid urbanisation and agricultural growth has taken place near bodies of water. When it rains, chemicals from cities, factories and fertilisers or untreated animal waste on farms can wash into lakes, streams and rivers. The extra nutrients feed algae on the surface of the water that can proliferate enough to block light. This deprives organisms of the light they need to photosynthesise. In the UK, for example, Tamar Lakes in south-western England suffered intense eutrophication pollution between 1975 and the 2000s, and the phenomena is also widespread in estuaries and coastal areas in the US.

Polluted water is a chronic problem in China, with citizens increasingly speaking out in frustration and even suing the government. In early 2013, some 16,000 dead pigs (including corpses infected by porcine circovirus) floated to Shanghai along the Huangpu river – a grisly sight that raised public concern about both unethical agricultural practices and water contamination. Some local governments have resorted to digging deeper wells to reach safe water, following an official survey finding as much as 80% of groundwater in major river basins is unsafe for human consumption.

Animal husbandry is a major contributor to contamination of China’s vital drinking water and seafood sources. The extensive survey of the impact of China’s agricultural transition published in Environmental Research Letters in 2016 found that in 2000, when the country was systematically expanding the size of farms, 30% to 70% of manure was dumped directly into rivers. Before 1970, when farms were mostly owned by single families, only 5% of manure was dumped into rivers. Later, a field test by Anhui Agricultural University showed that agricultural activity around Chaohu Lake in central Anhui province was the primary cause of pollution, according to a 2013 state newspaper report.

Read full article at The Guardian

Verde Environmental Consultants have built a team of water resource assessment specialists who are focused on delivering quality hydrogeological services such as:

  • groundwater abstraction feasibility assessments
  • authorisation of discharges to groundwater technical assessments
  • water quality/level monitoring
  • dewatering services

The development of sustainable groundwater resources is a key element in helping our clients to reduce costs associated with the use of water.

Read Chapter 5 of Ireland’s Environment, An Assessment 2016 report by the EPA

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