Variations in runoff and erosion and their distributions in the Yellow River basin

WANG Yangui;CHEN Kang;CHEN Yin;LIU Xi;International Research and Training Center on Erosion and Sedimentation (IRTCES);China Institute of Water Resources and Hydropower Research;Beijing Jiaotong University;

runoff and erosion;;runoff depth;;sediment transport modulus;;spatial distribution;;the Yellow River basin

[Background] With climate changes and the frequent occurrences of human activities such as reservoir construction,soil and water conservation,and water diversion project,water and sediment characteristics in the Yellow River basin would be changing. [Methods] In order to understand the processes of the runoff and sediment yields in the Yellow River basin,according to the water and sediment field data of the main hydrological stations in the mainstreams and the main tributaries in1950—2015,the variation process and spatial distribution characteristics of runoff and erosion in the basin were studied with the Mann-Kendall statistical test method( called M-K Method) and the hydrological accumulation curve method by introducing the parameters of regional runoff depth and regional sediment transport modulus. [Results] 1) For the runoff depth in the basin,there are no variation trend in the Tangnaihai station of the mainstream with an average value of 164. 4 mm,and decrease trends in the Lanzhou station of the mainstream and in the tributaries of the Yan River and the Beiluo River and obvious decrease trends for the other hydrologic stations in the basin in an exponential form,which shows the runoff generation capacity in other areas of the Yellow River basin gradually orobviously attenuates except for the area above the Tangnaihai station. 2) For the sediment transport modulus in the basin,except for no change trend in the Tangnaihai station with an average value of 97 t/( km2·a),there are obvious decrease trends for the other hydrological stations in the stem mainstream and 11 tributaries in the exponential decay law,which shows that sediment yield capacities in the basin are greatly weakened and soil erosion is reduced except for the area above the Tangnaihai station. 3) In the Yellow River basin,the upper reaches is the main area of runoff yield with the great regional runoff depth value of 138. 9 mm and the small regional sediment transport modulus value of 260. 6 t/( km2·a) in the area above the Lanzhou station,the middle reaches is the main area of sediment yield with the small regional runoff depth value of 39. 1 mm and the great regional sediment transport modulus value of 2776. 9 t/( km2·a) in the Longmen-Tongguan area,and the lower reach area is the main consumption area of runoff and sediment with the negative regional runoff depth value of-340. 8 mm and the negative regional sediment transport modulus value of-7 060. 6 t/( km2·a). It still exists,but weakened for the runoff and sediment from different sources. [Conclusions] Therefore,there are obvious variations in runoff and sediment yield characteristics because of influence of the human activities in the Yellow River basin,and it is weakened for that the runoff and sediment are from different sources,which needs to be paid attention.