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Liu X.-Y.,Chinese Ministry of Water Resources | Wang F.-G.,Upper and Middle Yellow River Bureau | Yang S.-T.,Beijing Normal University | Li X.-Y.,Yellow River Institute of Hydrology and Water Resources | And 2 more authors.
Shuili Xuebao/Journal of Hydraulic Engineering | Year: 2014

The sediment reduction effect of level terrace in the Loess Plateau is likely to have been under-estimated before. By analyzing the water and sediment regulation mechanism of the terraces in the basin, it is realized that the level terrace can not only significantly reduce the sediment yield from itself, but also intercept the sediment yield from the upper area, and can achieve the valley sediment reduction by reducing runoff flowing from slope to valley. The sediment reduction potential of level terrace with ridges in watershed is up to 65 %. Based on the measured data of the third and the fifth sub-district of the loess hilly region in different periods, the sediment reduction effect of different scale level terraces is analyzed under average annual rainfall condition. The concept of terrace ratio is introduced to build the relationship between terrace ratio and sediment reduction magnitude, which can be used to quantitatively evaluate sediment reduction effect of level terrace on a large spatial scale, When the terrace ratio is less than 30%, the magnitude of sediment reduction is basically proportional to the terrace ratio; and when the terrace ratio is larger than 35 %, the sediment reduction effect is basically stable at about 90%. The flood sediment concentration reduction effect of level terrace is not very obvious; this characteristic can be used to measure the water-reducing effect of level terrace in the river basin.


Zuo D.,Beijing Normal University | Zuo D.,Joint Center for Global Change Studies | Xu Z.,Beijing Normal University | Xu Z.,Joint Center for Global Change Studies | And 4 more authors.
Science of the Total Environment | Year: 2016

The changes in runoff and sediment load in the Loess Plateau of China have received considerable attention owing to their dramatic decline during recent decades. In this paper, the impacts of land-use and climate changes on water and sediment yields in the Huangfuchuan River basin (HFCRB) of the Loess Plateau are investigated by combined usage of statistical tests, hydrological modeling, and land-use maps. The temporal trends and abrupt changes in runoff and sediment loads during 1954-2012 are detected by using non-parametric Mann-Kendall and Pettitt tests. The land-use changes between 1980 and 2005 are determined by using transition matrix analysis, and the effects of land-use and climate changes on water and sediment yields are assessed by using the Soil and Water Assessment Tool (SWAT) hydrological model and four scenarios, respectively. The results show significant decreasing trends in both annual runoff and sediment loads, whereas slightly decreasing and significantly increasing trends are detected for annual precipitation and air temperature, respectively. 1984 is identified as the dividing year of the study period. The land-use changes between 1980 and 2005 show significant effects of the Grain for Green Project in China. Both land-use change and climate change have greater impact on the reduction of sediment yield than that of water. Water and sediment yields in the upstream region show more significant decreases than those in the downstream region under different effects. The results obtained in this study can provide useful information for water resource planning and management as well as soil and water conservation in the Loess Plateau region. © 2015 Elsevier B.V.


Liu X.,Chinese Ministry of Water Resources | Liu C.,Beijing Normal University | Yang S.,Beijing Normal University | Jin S.,Yellow River Institute of Hydrology and Water Resources | And 2 more authors.
Acta Geographica Sinica | Year: 2014

The impact of vegetation coverage on flood or runoff yield in the Loess Plateau has been extensively studied, but the research has been primarily based on observations from slope runoff plots or secondary forest regions. This paper is based on vegetation information from remote sensing images, measured rainfall and runoff data and water consumed from the related basin in Loess Plateau over nearly 50 years. By introducing the concepts of runoff yield coefficient, flood yield coefficient, base flow yield coefficient, and the percentage of effective vegetation, we proposed the quantitative relation between vegetation coverage extracted from remote sensing images and runoff yield at the watershed scale. The response relations reveal that the runoff yield and flood volume will decrease with the increase of shrubs-herbs-arbor vegetation, especially in the dryer region, and the reduction of the runoff in sand-covered loess region is even more than that in the loess region with similar climate. But the flood volume will be kept at a stable level, when the percentage of effective vegetation is larger than 60%. The river's runoff will be stable at a threshold, which is more than its base-flow at last, with a further increase of vegetation. ©, 2014, Science Press. All right reserved.


Liu X.,Yellow River Conservancy Commission | Yang S.,Beijing Normal University | Dang S.,Yellow River Institute of Hydraulic Research | Luo Y.,Beijing Normal University | And 2 more authors.
Science China Technological Sciences | Year: 2014

The impact of vegetation coverage on erosion and sediment yield in the Loess Plateau has been extensively studied, but the research has been primarily based on observations from slope runoff plots or secondary forest regions; the scaling method remains unresolved when it is applied at a large spatial scale, and it is difficult to apply to regions with severe soil and water loss given the predominance of herbs and shrubs. To date, there is little data on the quantitative impact of changes to vegetation on sediment concentration at a large spatial scale. This paper is based on vegetation information from remote sensing images, measured rainfall and sediment data over nearly 60 years, and results from previous runoff and sediment variation research on the Yellow River. We introduce the concepts of a sediment yield coefficient and the percentage of effective vegetation and erodible area, analyze the impact of different vegetation conditions on the flood sediment concentration and sediment yield, and evaluate the effect of rainfall intensity on sediment yield under different vegetation conditions at the watershed scale. We propose models to evaluate the impact of vegetation on sediment yield in the loess gully hilly region, which are based on remote sensing data and support an application at a large spatial scale. The models can be used to assess sediment reduction that results from the current significant improvement of vegetation in the Loess Plateau. © 2014 Science China Press and Springer-Verlag Berlin Heidelberg.


Lu W.,Beijing Forestry University | Lu W.,Yellow River Institute of Hydrology and Water Resources | Cheng J.,Beijing Forestry University | Wang W.,China Academy of Transportation Science | And 2 more authors.
Forestry Chronicle | Year: 2015

Preferential flow significantly influences hydrological processes in forests. The occurrence and development of this flow is directly affected by its spatial distribution. To determine whether or not point pattern analysis method can be used to examine the horizontal spatial distribution of preferential flow paths, experiments were conducted with dye tracer permeation to observe flow processes. Results indicated that an increase in penetration water volume exerted only a specific effect on preferential flow paths of large class in the topmost soil. Moreover, such paths showed distinct clumped patterns at the 25-cm scale under both high permeation water volume and low permeation water volume treatments. Nonetheless, the distribution pattern became uniform as scale range increased. The significance of the correlation between the spatial distribution of preferential flow paths and plant roots decreased from the top soil layer to the bottom. These findings suggest that soil depth and water permeation volume are important to the horizontal spatial distribution of preferential flow paths. Moreover, point pattern analysis method is suitable for investigating the horizontal spatial distribution of preferential flow paths and determining the correlation between the spatial distribution of preferential flow paths and plant roots. © 2015 Published by NRC Research Press.

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