Response of water and sediment to ecological construction of soil and water conservation in the typical watersheds of the Loess Plateau
[Background]Determining the mechanisms that drive the changes in the water-sediment processes in basins due to changes in the environment is a frontier and hot topic of international research.Due to climate change and strong anthropogenic influences,the water-sediment processes in the Yellow River basin have changed drastically,which poses significant challenges for the coordination of water-sediment relationships and the balancing of water and land resources in the basin.Research on the response to the water-sediment processes in basins to the ecological construction of water and soil conservation has an important reference significance for increasing our understanding of the causes of the dramatic changes in the water-sediment processes in the Yellow River basin.[Methods]In order to explore the evolution characteristics of water sediment relationship and its response to soil and water loss control in the sandy and coarse sand area of the Loess Plateau,the Wuding River basin in the middle reaches of the Yellow River was taken as the research object and methods such as the water-sediment relationship curve were used to analyze the multi-time-scale evolution characteristics and driving mechanisms of the water-sediment relationship in the Wuding River basin.[Results]1)The annual runoff and annual sediment discharge in the Wuding River basin from 1956 to 2019 significantly and suddenly decreased(P＜0.05),and the decrease mutation occurred around 1970.The relationship between water and sediment in the basin has undergone profound changes in inter-annual and field flood scales.There were obvious changes in the rainfall-flood and rainfall-sediment relations under extreme rainfall conditions.The parameters of the water sediment relationship curve demonstrated strong temporal variability characteristics.2)Parameter a showed the tendency rising up at the beginning and sharply declining in late,indicating a significant decrease in sediment supply in the watershed.On the contrary,parameter b displayed the tendency declining at the beginning and sharply rising up in late,indicating extreme precipitation is highly likely to cause high sediment concentration floods.3)After 2010,the frequent occurrence of heavy rains led to a significant increase in the source supply of the eroded materials in the basin and a small increase in the sediment transport capacity of the river channels in the basin.4)The implementation of water and soil conservation measures had a significant impact on the water and sediment reduction in the basin.Under similar rainfall conditions,around 2000,the runoff per unit of rainfall and the sediment discharge per unit of rainfall decreased by 47％and 62％,respectively,compared with the values in the 1970s.The increase in the area of soil and water conservation measures was consistent with the decrease in runoff and sediment discharge in the basin.[Conclusions]Soil erosion control has played an important role in improving soil erosion resistance in the sandy and coarse sand area of the Yellow River.These results provide a reference for improving our understanding of the effectiveness of regional soil erosion control measures and the causes of the sharp decrease in the sediment influx in the Yellow River.
water-sediment relationshipextreme rainstormsoil erosionmanagement effectivenessYellow River
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