Abstract:

The Gaobao lakes refer to a group of lakes to the west bank of the Grand Canal in the central part of Jiangsu Province. They used to be one of the important passages for the Huaihe River draining into the Yangtze River. Under the influence of the changing relationship between the Yellow River and the Huaihe River and land reclamation activities, the shape of the Gaobao lakes has changed dramatically in recent 300 years. This article analyzes three digitized earliest surveyed maps of the Gaobao lakes, discusses related historical literature and investigates some borehole data. In doing so, this article discovers that the evolution of the Gaobao lakes can be divided into three stages. The first stage is from the Kangxi reign to the Qianlong reign (1662-1795), when the Gaobao lakes in recent 300 years reached the top in area - 1606 km2 on the first surveyed map of China complied in 1717. The second stage is after the Qianlong reign, when sandbars began to develop in the Gaobao lakes as the sediments from the Hongze Lake gradually deposited to its northwest. The third stage is after 1851 when the Sanhe River which originated from the southeast part of the Hongze Lake became a main passage for the Huaihe River to empty into the Yangtze River. The Sanhe River brought a large amount of sediments into the Gaobao lakes and formed the Sanhe delta. With the expansion of the Sanhe delta, the Gaobao lakes have been quickly shrinking, from 1606 km² in 1717 to 1494 km2 in 1868, 1072 km² in 1916 and 887 km² in 2011. This article argues that the sediments deposited from the Hongze Lake is a main reason for the shrinkage of the Gaobao lakes. Human reclamation activities expedited the process of sedimentation and changes of the Gaobao lakes.

Key words: Huaihe River, Gaobao lakes, Hongze Lake, Sanhe River