ORIGINAL PAPER Atmospheric moisture budget and floods in the Yangtze River basin, China Zengxin Zhang & Qiang Zhang & Chongyu Xu & Chunling Liu & Tong Jiang Received: 28 July 2007 / Accepted: 12 February 2008 / Published online: 11 April 2008 # Springer-Verlag 2008 Abstract In this paper, we explored the trends of the atmospheric moisture budget, precipitation, and streamflow in summer during 1961 to 2005 and possible correlations between them by using the linear regression method in the Yangtze River basin, China. The results indicate that: (1) increasing tendencies can be detected in the atmospheric moisture budget, precipitation and streamflow in the Yangtze River basin; however, the significant increasing trends occur only in the atmospheric moisture budget and precipitation in the middle and lower Yangtze River basin; (2) both the ratio of summer moisture budget to annual moisture budget and the ratio of summer precipitation to annual precipitation exhibit a significant increasing trend in the Yangtze River basin. The ratio of summer streamflow to annual streamflow is in a significant increasing trend in Hankou station. Significant increasing summer precipita- tion can be taken as the major controlling factor responsible for the higher probability of flood hazard occurrences in the Yangtze River basin. The consecutively increasing summer precipitation is largely due to the consistently increasing moisture budget; (3) the zonal geopotential height anomaly between 1991 and 2005 and 1961 and 1990 is higher from the south to the north, which to a large degree, limits the northward propagation of the summer monsoon to north China. As a result, the summer moisture budget increases in the middle and lower Yangtze River basin, which leads to more summer precipitation. This paper sheds light on the changing properties of precipitation and streamflow and possible underlying causes, which will be greatly helpful for better understanding of the changes of precipitation and streamflow in the Yangtze River basin. 1 Introduction Global warming, which is due to the enhanced greenhouse effect, is likely to have significant effects on the hydrolog- ical cycle (IPCC 2007). The accelerated hydrologic cycle of the last two decades is believed to be one of the consequences of global warming, especially for some parts of the northern hemisphere (Brutsaert et al. 1998; Karl et al. Theor Appl Climatol (2009) 95:331–340 DOI 10.1007/s00704-008-0010-z Z. Zhang (*) State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China e-mail: zhangzengxin77@yahoo.com.cn Z. Zhang Jiangsu Key Laboratory of Forestry Ecological Engineering, Nanjing Forestry University, Nanjing 210037, China Z. Zhang Graduate School of the Chinese Academy of Sciences, Beijing 100039, China Q. Zhang : T. Jiang Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China Q. Zhang : C. Liu Department of Geography and Resource Management and Institute of Space and Earth Information Science, The Chinese University of Hong Kong, Shatin, Hong Kong, China Z. Zhang : Q. Zhang : T. Jiang Laboratory for Climate Studies, National Climate Center, China Meteorological Administration, Beijing 100081, China C. Xu Department of Geosciences, University of Oslo, Oslo, Norway