Acta Geographica Sinica ›› 2012, Vol. 67 ›› Issue (5): 699-709.doi: 10.11821/xb201205012

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Annual Variations in Climatic and Hydrological Processes and Related Flood and Drought Occurrences in the Poyang Lake Basin

GUO Hua1, HU QI2, ZHANG QI1, WANG Yanjun3   

  1. 1. Nanjing Institute of Geography and Limnology, and National Key Laboratory of Lake and Environmental Studies, CAS, Nanjing 210008, China;
    2. School of Natural Resources and Department of Earth and Atmospheric Sciences University of Nebraska-Lincoln, Lincoln, NE 68583-0987, USA;
    3. College of Remote Sensing, Nanjing Institute of Information Science and Engineering Nanjing 210044, China
  • Received:2011-11-03 Revised:2011-03-25 Online:2012-05-20 Published:2012-05-20
  • Supported by:
    National Basic Research Program of China, No.2012CB417003; Key Knowledge Innovation Programs of the Chinese Academy of Sciences, No.KZCX2-YW-337; Science Foundation of Nanjing Institute of Geography and Limnology, No.NIGLAS2010XK02; Natural Science Foundation of China, No.41001017; USDA Research Project, No.NEB40-040

Abstract: Observational data from 1960-2008 were analyzed to obtain the mean annual climate and hydrological variations in the Poyang Lake basin, China. These variations were explained by the surface water and energy budgets, and the characteristics of these variations and the budgets were further used to deduce the rhythms of flood and drought developments in the lake basin. Some conclusions can be drawn as follows. (1) The precipitation in the lake basin increases at a large rate from January to June, reaching the annual maximum in late June. Amplifying monthly precipitation, particularly from April to June, coupled with weak surface evaporation and transpiration (ET), saturates the soils and produces a large amount of surface runoff which raises the lake level. In July, rainfall decreases sharply with clear sky and high ET, which reduces surface runoff and reverses the hydrological processes developed in the first half of the year. These drying processes continue through October, making the basin dry again. (2) When June and July have above average monthly precipitation the lake basin becomes supersaturated, and floods develop. In such conditions, if July rainfall in the middle and upper reaches of the Yangtze River basin is above average, the Yangtze River blocking (or reversed flow) effect can trigger, intensify, and prolong Poyang Lake floods. Thus, Poyang Lake floods generally occur in July and August. (3) Because the lake basin is drying after July with strong ET, if there is below average rainfall in July and the months afterwards, ET would be greater than rainfall, causing drying. Drought could occur in fall. This fall drought can persist through the winter and into the following spring and result in severe spring drought in the lake basin. Thus, the droughts occur in the fall and spring months in the lake basin. (4) The Yangtze River effects on the floods and droughts in the lake basin are most significant during the "river-lake coupling period" from July to August. Strong effects can lead to floods in the lake basin. Lack of river effects would help lower the lake level and dry the basin, leading to drought in fall.

Key words: floods and droughts, climate, hydrology, Poyang Lake basin, the Yangtze River, river-lake interactions