Quantitative contribution of climate change and human activities on flood-season streamflow in the middle of Loess Plateau, China

Abstract:

The Yanhe River Basin (YRB) is the first-order tributary of the Yellow River, which is located at the middle of the Loess Plateau, China. The Yanhe River is the main river that causes floods and damages to the Yanan city. The YRB contributes significantly to the total sediment yield in the Yellow River. A great number of water and soil conservation measures including terracing, afforestation, and construction of sediment-trapping dams have been implemented since the 1960s. It is important to investigate the contributions of climate change and human activities affecting the changes of flood-season streamflow and to provide a scientific basis for future flood prevention. The data from six hydrological stations and 22 meteorological stations of YRB are used in this study. Two nonparametric methods, the Mann-Kendall test and the Pettitt test, are used to detect change trend and change point in the flood-season streamflow for the period of 1952 to 2003. The lumped conceptual daily hydrological model SIMHYD and one kind of sensitivity-based method are used to assess the impact of climate change and human activities to flood-season streamflow. The results show that the change point in flood-season streamflow occurred in 1972. The flood-season streamflow has decreased by 34.2% from 1972 to 2003 compared with the period from 1952 to 1971. The flood-season streamflow becomes more sensitive to change in precipitation than change in potential evapotranspiration (PET) in 1972-2003. The impact of human activities is greater than climate change after 1972. The effects of climate change and human activities on flood-season streamflow account for about 36% and 64% respectively.