Poyang Lake

Poyang Lake is the largest freshwater lake in China.

It is located within the Jiujiang Prefecture of Jiangxi Province. Three specific rivers feed the lake: the Gan, Xin, and Xiu rivers. These rivers flow into the lake before moving north. The water then flows into the Yangtze River through a single channel. The surface area of the lake fluctuates dramatically between wet and dry seasons. In recent years, the overall size of the lake has been decreasing.

The lake's formation is tied to the changing path of the Yangtze River. Before the Han dynasty, the Yangtze followed a more northerly course. It flowed through what is now known as Longgan Lake. At that time, the Pengli Marsh formed the lower reaches of the Gan River. The area of the current Poyang Lake was simply a plain along the Gan River. Around AD 400, the Yangtze River switched to a more southerly course. This change caused the Gan River to back up further. This process eventually formed Lake Poyang.

History provides several names and stories for this water system. It was called Pengli Lake in the past, though it is not the same as the modern lake. The lake was named after Poyang County. This county, along with Haihun County, was flooded by the lake. This flooding forced a mass migration to Wucheng Township. Wucheng is located in what is now Yongxiu County. This event created the Chinese idiom, "Drowning Haihun County gives rise to Wucheng Township." The name Poyang also relates to the earlier Po County from the Qin dynasty. That county was named for the city of Poyi in the state of Chu.

The lake has reached massive sizes throughout history. During the Tang dynasty, the lake reached its greatest size. Its area was approximately 20,000 square kilometers during that period. However, modern environmental factors have caused the lake to shrink. In early 2012, the lake area dropped to about 2,665 square kilometers. This was caused by drought, sand quarrying, and water storage at the Three Gorges Dam. In October of that year, only 1,500 square kilometers of land were underwater. This is much smaller than the normal area when the lake is full.

Many animals depend on this ecosystem for survival. The lake provides a habitat for half a million migratory birds. It is a major destination for birdwatching. During the winter, many Siberian cranes migrate to the lake. Up to 90% of this critically endangered species spend their winters there. The lake is also home to the finless porpoise. Locals call this animal the "jiangzhu," or river pig. There are about 500 of these porpoises in Poyang and Dongting Lakes. However, their population is dropping by 7.3 percent every year. In 2007, their numbers were less than half of what they were in 1997.

Several human activities impact the wildlife in the lake. Sand dredging is a major source of revenue for the local economy. However, high-density dredging is a principal cause of wildlife death. Dredging makes the water much muddier. This makes it hard for porpoises to see. They must rely on sonar, which is a system of sound waves, to find food. Additionally, two large ships enter or leave the lake every minute. This high density of shipping makes it hard for porpoises to hear their food. It also prevents them from swimming freely between banks.

Conservation efforts are currently underway to protect the region. In January 2020, China imposed a 10-year fishing moratorium. This ban covers 332 sites along the Yangtze, including Poyang Lake. This measure aims to protect marine biodiversity. In 2019, Conservation International China began working in the Poyang Lake basin. They use the Freshwater Health Index to identify challenges. This helps them prioritize actions for wetland protection and sustainable resource use. The local government has also proposed a Poyang Lake Dam. This would involve a sluice wall to maintain water levels. However, scientists argue this could hurt wildlife diversity.