Recent Variation of Runoff and Sediment in Response to the High Intensity Human Activities in Dongchuan Basin of Jinghe River

According to the field survey data and measured typical hydrological data of the Dongchuan basin of the Jinghe River,the causes of runoff and sediment variation in response to the recent high intense human activities were analyzed.Theindex methodwas used to calculate the reduction of runoff,sediment and soil erosion of soil and water conservation measures,such as terraces,woodland,grassland,dam field and closing hillside for erosion control,and the concept ofwater conservation measures reduce erosion and sediment trapping volumewas proposed.New soil erosion amount caused by human activity containing basin oil well site and roads of oil exploitation,steep slope farming,road construction and brickyard were quantitatively calculated for the first time.The results showed that(1)the relationship between rainfall flood and sediment bounded on the average areal rainfall of 100 mm in the basin was divided into low and high value two areas of runoff generation and sediment yield.In high value area,the relationship between rainfall flood and sediment was very close,and the amount of runoff generation and sediment yield by the unit millimeters rainfall were 29 times and 38 times the value of the low area.(2)By the end of 2013,the amount of runoff,sediment and erosion respectively decreased by 12.1 million m3,7.43 million t and 16.06 million t,caused by water and soil conservation measures in the basin,the effects of runoff and sediment reduction were 10.1% and 21.8% respectively.During the period of 2009 to 2013,annual increased amount of anthropogenic soil erosion was new 2.24 million t/a,accounting for 14% of reduction of erosion by soil and water conservation measures over thesame period.The increased amount of anthropogenic soil and water loss of oil exploration annual spoil loss was in the lead,followed by cultivation on steep slopes.(3)The main reason for an increase of the sediment discharge and hyper-concentration sediment flood was that the frequency of heavy rain increased significantly in the basin since 2008.The increased amount of anthropogenic soil and water loss and oil exploration,steep slopes cultivation,and so on had an increasing trend.In recent,comprehensive treatment of soil and water conservation was not enough,and the proportion of dam field was low.While the capacity of reduction of runoff and sediment by the recent forest and grass measures in Dongchuan basin,the reason for hyperconcentration sediment flood,and effects of soil and water loss management were discussed.Research results had important reference value to deepen the study of recent changes in runoff and sediment of the Yellow River,and the continue to carry out effective governance of the loess plateau soil and water loss.