Trend, abrupt change, and periodicity of stream flow in the mainstream of Yellow River

摘要

The Yellow River is the second largest river in China. The annual runoffof which is only about 2 % of China's total, but contributes to 9 % of China's GDP and directly supports 12 % of the population. Today, the water shortage in the Yellow River basin has been aggravated due to rapid population growth and global warming. In order to best maximize water resources management, the natural and observed streamflow series from six hydrologic gauging stations (Guide, Lanzhou, Hekou, Sanmenxia, Huayuankou, and Lijin) are obtained, and the linear regression, Mann-Kendall test, and wavelet transform methods were used to detect the characteristic of streamflow variation from 1956 to 2007. The results show that: (1) both the natural stream-flow and observed streamflow present a downward trend over the past 52 years, and the trends are intensified downstream; the decreasing rate of observed streamflow is more rapid than that of the natural stream-flow; (2) most of the abrupt changes in natural stream-flow and observed streamflow appear in the late 1980s to early 1990s through the result of the Mann-Kendall test; and (3) other than the Guide station, the stream-flows at the rest of the stations appear to have strongest periodicity of 19-21 years with a 52-year scale. The results of this study imply that less precipitation and warmer climate in the basin are the primary factors that cause this decreasing trend of natural streamflow. Additionally, the rapid ascent of water consumption by human being results in the reduction of observed streamflow further. Furthermore, human activities like reservoir construction, soil and water conservation measures, etc. influence the streamflow as well. It is recommended that the society takes some effective countermeasures to cope with the water shortage.