In January 2012, we were writing about the dried-out beds of Poyang Lake in Jiangxi Province of southeastern China, where drought had shrunk the lake to a fraction of its former area. After a year of poor rainfall, the lake covered less than 188 square kilometers (73 square miles). China’s two largest fresh water lakes – Dongting Lake in Hunan and Poyang Lake in Jiangxi – are both drying up dramatically and almost 40 million people had been affected in the five provinces.
Since than regions had experienced persistent heavy rains. On May 2, 2012, China.org.cn reported that Poyang Lake’s area had quadruped over the previous month, rising from 668 to 2,370 square kilometers (258 to 915 square miles). By May 21, Poyang Lake was visibly swollen compared to its extent in early April. The surface water and the volume are expected to continue to increase as the lake has a net inflow of 5,000 cubic meters of water per second.
Heavy rains caused widespread destruction in southern China in May 2012, and Jiangxi rainfall from January through April 2012 was 35% above average. But the differences in Poyang Lake shown here are probably at least partly normal seasonal changes. Fed by multiple rivers, the lake’s level can vary throughout the year, and the region’s rainy season typically starts in April and continues through June.
The flood risk is still low and more water in the lake can provide a better living environment and more food for fish living in Poyang Lake, including threatened finless porpoises. Since the beginning of this year, more than 20 of these animals have been found dead in the Yangtze River and two lakes including Poyang Lake. Initial autopsies showed that most of them died of starvation.
Jiangxi Province is just north of the Tropic of Cancer. It is classed as a typical northern subtropical monsoon climatic region. Generally speaking, Jiangxi Province has a rainy period starting from April; May and June are the months with the most rainfall; and the rain period is over in July. Then the whole province has a period of hot and sunny weather. In October, the temperature begins to drop. From midsummer to early autumn, it is sunny, hot and dry most of the time. In winter, the weather is raw with rare rain.
Poyang Lake is situated in the north part of Jiangxi province, lying on the south bank of the middle and lower reaches of Changjiang River. It swallows a large quantity of water coming from rivers Ganjiang, Fuhe, Xinjiang, Raohe and Xiuhe, together with several smaller rivers such as Qingfeng Shan, Boyang, Zhangtian and Tongjing , then spits the incoming water into the Changjiang River through the estuary after its regulation and storage. Poyang Lake is an overflow lake with a characteristic of taking in and sending out water in the light of seasonal variations. The whole Poyang Lake system has a basin area of 162200km2, occupying 9% of Changjiang River basin area. Because of its seasonal characteristic, Poyang Lake shows a unique picture that it is a lake when inflowing water is adequate, a stream when inflowing water scarce.
Sources: Earth Observatory, China.org.cn, PoyangLakeProject
Featured image credit: China.org.cn