Evaluating the non-stationary relationship between precipitation and streamflow in nine major basins of China during the past 50 years Zengxin Zhang a,b , Xi Chen a,⇑ , Chong-Yu Xu c,e , Lifeng Yuan d , Bin Yong a , Shaofeng Yan b a State Key Laboratory of Hydrology – Water Resources and Hydraulics Engineering, Hohai University, Nanjing 210098, China b Jiangsu Key Laboratory of Forestry Ecological Engineering, Nanjing Forestry University, Nanjing 210037, China c Department of Geosciences, University of Oslo, Norway d Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China e Department of Earth Sciences, Uppsala University, Sweden article info Article history: Received 22 September 2010 Received in revised form 8 June 2011 Accepted 29 July 2011 Available online 8 September 2011 This manuscript was handled by Andras Bardossy, Editor-in-Chief, with the assistance of Vazken Andréassian, Associate Editor Keywords: Streamflow Precipitation Variability Large river basin China summary In this paper, the trends of the annual streamflow and precipitation and cross correlations between them were analyzed in nine large river basins of China during 1956–2005. The results indicate that: (1) the annual mean streamflow decreases in arid and semi-arid regions of north China; however, increasing trends occur in south and Southwest China; (2) the annual streamflow and precipitation exhibit reason- able correlation in nine large river basins except those located in inland areas. The annual streamflow over most areas of China is fed by precipitation; however, the decline in streamflow is faster than the decreases of precipitation since 1970s in the arid and semi-arid regions of north China. The relationship between the annual precipitation and streamflow presents a non-stationary state in north China. This non-stationary relationship is strongly influenced by both human activities and precipitation changes; (3) a significant increase of water use might be the major factor responsible for the steeper decline in streamflow than in precipitation in Haihe River, Yellow River and Songliao River basins in north China. In inland river areas, increase of water use and actual evapotranspiration might result in decline in streamflow although precipitation has an increase tendency. This paper sheds light on the non-stationary relationship between annual precipitation and streamflow and possible underlying causes, which will be helpful for a better understanding of the changes of precipitation and streamflow in China at large scale and in other regions of the world. Ó 2011 Elsevier B.V. All rights reserved. 1. Introduction Access to water is already a serious issue for people in many parts of the world and, given recent United Nations estimates, the situation is not likely to improve (Meek and Meek, 2009). From a resource perspective, streamflow is a measure of sustainable water availability which is most vital for sustainable development, utilization of water resources and better governance (Dong et al., 2009). It is now common knowledge that human activities including water diversions and land development, in addition to climate, have a significant impact on streamflow and other hydrological processes (Milly et al., 2005). Many previous studies showed that continental runoff had increased during the 20th century despite more intensive human water consumption (Labat et al., 2004; Probst and Tardy, 1987; Shiklomanov, 2000; Gedney et al., 2006). However, it has also been widely discussed that decrease in streamflow in many areas during the past decades is highly influ- enced by human activity (Zhang et al., 2001, 2007, 2008; Ren et al., 2002). Regional patterns of streamflow changes are complex and less certain than those in temperature. Milly et al. (2005) analyzed the trends of observed global streamflow and found that less runoff occurred in sub-Saharan Africa, southern Europe, southernmost South America, Southern Australia and western mid-latitude North America, while the observed streamflow increases in the La Plate basin of southern South America, Southern through central North America, the Southeastern quadrant of Africa, and northern Australia. Shortage of water is becoming one of the key restricting factors of the development of Chinese society and economy. Although China’s water resources rank sixth in the world by total volume, per capita water availability is roughly one quarter of the world average. Moreover, water resources are not distributed evenly across regions and time. Based on the observed streamflow of 19 key hydrological control stations in the six large basins in east Chi- na for the past 50 years, Zhang et al. (2007) found that the ob- served annual streamflow in the six large basins has generally 0022-1694/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jhydrol.2011.07.041 ⇑ Corresponding author. E-mail address: xichen@hhu.edu.cn (X. Chen). Journal of Hydrology 409 (2011) 81–93 Contents lists available at SciVerse ScienceDirect Journal of Hydrology journal homepage: www.elsevier.com/locate/jhydrol