Attribution of the changes in annual streamflow in the Yangtze River Basin over the past 146 years

Water resources in the Yangtze River, the longest river in China, are of great importance for the water security of China. In this study, 146 years (1865–2010) of streamflow data were used to investigate the changes in streamflow of the Yangtze River. The Mann-Kendall test and wavelet coherence analysis were used to test the change points in annual streamflow. The streamflow data, combined with the meteorological dataset of the Climatic Research Unit (CRU) from 1901 to 2010, showed that the Yangtze River streamflow changes occurred in four major periods over the past century: 1901–1930, 1931–1960, 1961–1990, and 1991–2010. The average annual streamflow for the four periods was 497.26, 499.11, 476.25, and 471.93 mm, respectively. The period from 1901 to 1930 was considered the baseline period for estimating the streamflow changes during the other three periods. We found that the streamflow increase during 1931–1960 was mainly influenced by climatic variation, while the streamflow decrease during 1961–1990 was mainly attributed to human activities because of tremendous population growth and rapid economic development. During the period 1991–2010, both climatic variation and human activities led to a decrease in streamflow, and human activities were still the main driving factor for the streamflow decrease. However, the contribution proportion of human activities to the streamflow decrease during 1991–2010 was much smaller than that during 1961–1990. The estimation results indicated that human activities have become the dominant driving factors of the streamflow changes in the Yangtze River Basin since 1961. Human activities, such as booming socio-economic development and fast population growth, have brought new challenges for water resources management in the Yangtze River Basin.