Serious flooding after serious drought in the Poyang lake watershed

 
 

Poyang Lake, China’s largest freshwater lake, has suffered from the most serious drought of the last 60 years. Unlike the normal cycle, this year’s drought lasted from the whole spring to the summer. The serious drought has caused many problems: the land cracked, some lakes and rivers dried, fish died and rice products decreased enormously in the area of Poyang Lake watershed. According to the hydrological station of Xingzi, the area of Poyang Lake shrunk to one-tenth of its original size of 2010.

 

April and May are normally the months of flooding in Poyang Lake watershed, but long-lasting drought raised widespread concerns, including us – MRLSD (Promotion Association for Mountain-River-Lake Regional Sustainable Development). In May, MRLSD, in cooperation with MRLDO, took actions for strategic analyses by investigating several hydrological stations of Poyang Lake and analyzing satellite data of the same periods over the last ten years.

 

These are the researched results by MRLDO:

 

The water levels of Poyang Lake in the same period of 3 different years.

 
 Settling at Lake Poyang
 
 Water level on April 23, 2011
 Water level on May 10, 2000
 Water level on April 23, 1988

April 23, 2011

Water level: 9.56 m above sea level 

 

May 10, 2000

Water level: 13 m above sea level

 

April 23, 1988

Water level: 13.06 m above sea level

 
 

According to 20-years of research on Poyang Lake watershed by MRLDO, one major reason of the serious spring-summer drought are the area’s plants as they have only inferior water storage capacity, due to deforestation and agricultural development. Dr. Yan Bangyou, vice director of MRLDO, noted that although some provinces have high rates of forest coverage, the shrubs under the trees are week and only a few what causes further inferior water storage capacity. As a consequence, terrible droughts would be inevitable.

 

However, while the whole country was busy in conquering the drought of North China, the strong and continuous rain came at the beginning of June, and more than ten provinces faced flood disasters within one day - including Jiangxi Province. The sudden turn from drought to flooding is a terrible phenomenon of climate change. These changes already happened in the history, but never as seriously and widely as this time, official meteorological sources reported. MRLSD suggested that it is important to optimize the forest structure and to improve the water storage function of lands. Flooding management by changing the circulations of rivers and lakes through reservoirs and dams are also a critical problem. Rather, lakes and rivers should be left in their natural form, as lake structures and bends of rivers can store more water and control flood more effectively.

 

Poyang Lake, the relationship with Yangtze River

 

“Dongting Lake is the largest fresh-water lake of China, and Poyang Lake is in the second place” written in the high school history book of 1970. With a beautiful map below, the two lakes, just like two Chinese lanterns, are hanging on the long and bending ribbon – the Yangtze River.

 

In 40 years, Dongting Lake shrunk to be the second place due to the natural geographical facts. While Poyang Lake kept its wetland function of water adjustment for Yangtze.

 

Poyang Lake, located in the North of Jiangxi Province, is connected to Yangtze River by a narrow waterway and accumulates water from 5 rivers of Jiangxi Province. The average depth of water is about 8 meters, and the deepest point is at about 25 meters. Poyang Lake has the function to adjust the water quantity of Yangtze River. When the water level of Yangtze River is lower than that of Poyang Lake, the clean water of Poyang Lake will flow into Yangtze River. In contrast, the water of Yangtze River will pour into Poyang Lake, which normally happens at raining season, generally in April and May each year. That is why the area of the lake can grow to more than 5.000 sq. km during rainy season and drop to approximately 1.000 sq. km at dry season. But most of the time, strong rain at rainy seasons produces large amounts of water in all three: the Yangtze River, the Poyang Lake and the Dongting Lake. As a result, flooding and debris flow are happening each year in the widespread area around Yangtze River, causing serious loss in both, the economy and human life.

 

During the decades, the people along Yangtze River and around Poyang Lake became tired of flooding. The biggest flooding of history happened in 1998, which impacted 29 provinces, covered over 20 million ha in total, affected over 200 million people, and accounted for 27 billion dollars in economical loss.

 

During the current drought, fishermen and farmers were severely affected. However, at third of June, the strong raining came and even more severe disasters are likely to happen. It was reported that the flooding destroyed several villages within one day and even took the live of hundred people in the debris flow. It can be forecasted that those provinces around South of Yangtze River have to face a month of flooding, which is much more terrible than the drought before.

 
 Grassland during the dry season
 Rice paddies in the catchment area of Lake Poyang
 Vegetation in the surroundings
 Settlemt directly on the shoreline
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