TROPICAL GEOGRAPHY ›› 2016, Vol. 36 ›› Issue (4): 700-709.

Influence of the Yangtze River Droughts on the Exposure Characteristics of the Poyang Lake Wetlands

LI Mengfan1,3，ZHANG Qi1,2，LI Yunliang1,4，YAO Jing1

1. （1．Key Laboratory of Watershed Geographic Sciences，Nanjing Institute of Geography and Limnology，Chinese Academy of Sciences，Nanjing 210008，China；2．Key Laboratory of Poyang Lake Wetland and Watershed Research of Ministry of Education，Jiangxi Normal University，Nanchang 330022，China；3．University of Chinese Academy of Sciences，Beijing 100049，China；4．State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering，Hohai University，Nanjing 210098，China）
• Received:2015-06-15 Online:2016-07-05 Published:2016-07-05

Abstract:

The variations in flow regime of the Yangtze River inevitable affect the hydrological condition in the Poyang Lake, and thus affect the spatial pattern of the exposure characteristics of the lake wetlands. In this study,we used a physically based hydrodynamic modeling (MIKE 21) to explore the influence of the Yangtze River droughts on the characteristics of spatial-temporal distribution of exposure area of the Poyang Lake. The objectives were achieved through the comparison of two simulation scenarios. One was the reference case representing for an average condition over a long period of 1953-2000 (marked as S0). The other represented the typical dry year in 2006 for the Yangtze River (marked as S1). Simulation results were assessed for the lake’s recession period from July to December. Results indicated that the Yangtze River drought caused the onset of the exposure of wetland about one month earlier compared to that for the reference case. In 2006, it took only half month to reach an exposure area of 50% of the maximum, which was 1.5 months shorter than that for the reference case. Simulation results also showed that the most significant period affected by the Yangtze River discharge was from August to November. In early August, the expansion of wetland mainly distributed in the Ganjiang delta and the eastern bay of the Poyang Lake. During the period from middle August to November, the expansion of wetland shifted to the northern (downstream) and middle regions of the Poyang Lake. It was found that the flow regime change in the Yangtze River had more impacts on the northern-central parts of the Poyang Lake than the southern (upstream) regions. It was also found that the average wetland expansion rate for 2006 was 25 km2/d, which was 72% more than that for the reference case (14.5 km2/d). This paper was the first attempt to use a physically based hydrodynamic modeling to reveal the interaction between the wetland exposure characteristics of the Poyang Lake and the seasonal flows of the Yangtze River.