The analysis of a abruption and key factors on precipitation and Natural runoff in Hai River Basin

In this paper, the abruption analysis of precipitation and runoff were researched by using Mann-Kendall method, based on the hundred year´s rainfall information of the representative stations including Beijing, Tianjin and Baoding. The rainfall and runoff materials lasting fifty years of four secondary regions in Hai River Basin. The results revealed that the precipitation of Hai River Basin had taken significant changes for four times in the last 100 years, the abrupt change points were separately 1893, 40-50 years in the 20th century, 1962 and 1980; for Natural runoff, it mainly contained twice in the last 50 years, one was 1961, and another was around 1980. The last abrupt change point of precipitation in the basin was caused by the climate change in 1980, which was the decrease of water vapor inflow. Correspondingly, the reasons for natural runoff spiking were the abrupt change of precipitation and dramatic changes of underlying surface impacted by human activities since 1980.