Maximum water level of Hongze Lake and its relationship with natural changes and human activities from 1736 to 2005

Hongze Lake is the fourth largest freshwater lake in China. The water level of Hongze Lake has changed significantly in the past centuries, and the maximum water level (MWL) is influenced by both natural and anthropogenic factors. This paper explores the changes and driving factors (including natural changes and human activities) of Hongze Lake water level, using the annual MWL data from both historical documents and gauged records, and investigates the relationship between the Hongze Lake MWL and the flood/drought disasters of the Huai River basin, Meiyu length, and human activities. The results shows that during the 1736-1953 period, river changes, such as the Yellow River's capture of the Huai River, contributed substantially to the changes of Hongze Lake water level. The MWL correlated also well with climate changes (e.g. flood/drought changes, Meiyu length) during this period. During 1954-2005, the flood/drought series in the Huai River basin is consistent with the flood season/annual precipitation, but the annual MWL of Hongze Lake is not. This is because a large number of hydraulic projects have been constructed around the Hongze lake during this period, and thus the MWL is greatly influenced by artificial regulations since the 1950s. The paper comes to the conclusion that the changes of the MWL were mainly driven by natural changes before the 1950s. Anthropogenic activities (especially hydraulic engineering) have played a more and more important role in the MWL changes in the past 50 years. (C) 2013 Elsevier Ltd and INQUA. All rights reserved.