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Zheng M.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research | Qin F.,Henan University | Yang J.,Yellow River Institute of Hydraulic Research | Cai Q.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research
Catena | Year: 2013

The spatio-temporal variation underlies and complicates studies related to earth surface processes. Subsequent to our previous studies reporting the temporal invariability of sediment concentration, this study further reports the spatial invariability of sediment concentration or the flow-sediment relationship in the hilly part of the Chinese Loess Plateau. The dense channel network dissects this area into numerous sub-watersheds, which are composed of entire slopes (a combination of the hill slope and the valley side slope). Our data mainly involves ten experimental sites of entire slope and sub-watershed and 580 flood events at three locations. Our analysis at the intra-event time scale shows that the instantaneous sediment concentrations in runoff can generally approach the detach-limited maximum sediment concentration since the active massing wasting ensures an abundant sediment supply. Consequently, the event mean sediment concentration does not only remain fairly constant among flow events but also among the experimental sites despite the possible differences in topography, soil management or land cover, water source, soil surface properties, etc. This observation also holds at the annual time scale. Our result implies that a single proportional function is adequate to fit the flow-sediment relationship for any entire slope or sub-watershed, where eroded sediments are primarily sourced, over a considerable areal extent unless soil property has changed or check dams are installed. Moreover, the proportionality coefficient, which is indicative of the maximum detachment capacity, can be approximated through flume experiments rather than necessarily through long-term field observations. Our finding can facilitate the obtainment of spatially distributed information on soil loss in the Chinese Loess Plateau and is also indicative of other locations where sediment supply is sufficiently available. © 2013 Elsevier B.V. Source

Yao W.,Yellow River Institute of Hydraulic Research | Xu J.,CAS Institute of Geographical Sciences and Natural Resources Research
Environmental Earth Sciences | Year: 2013

Fluvial suspended sediment has multi-fold environmental implications and the study of the variation in suspended sediment load (SSL) of rivers is important both in environmental earth sciences and in river environmental management. Based on data collected for the upper Yellow River of China in the past 50-60 years, the purpose of this study is to elucidate the impact of human activity and climate change on SSL, thereby to provide some knowledge for the improvement of the drainage basin management. The results show that the SSL of the upper Yellow River exhibited a remarkable decreasing trend. A number of reservoirs trapped a considerable amount of sediment, resulting in a reduction in SSL at Toudaoguai station, the most downstream station of the upper Yellow River. The analyses based on Mann-Kendall'U and double-mass plot indicate some turning points, which were caused by the Liujiaxia and Longyangxia Reservoirs, two major reservoirs on the upper Yellow River. The implementation of soil and water conservation measures reduced the runoff coefficient, and therefore, the intensity of soil erosion. The climate change also played a role in reducing sediment yield. The increase in air temperature enhanced the evapo-transpiration and reduced the runoff, by which the SSL decreased. The decreased frequency of sand-dust storms reduced the amount of wind-blown, sand and dust to the river reaches located in desert, also reducing the SSL. Seven influencing variables are selected to describe the changing human activity and climate. As some of the influencing variables are strongly inter-correlated, the principle component regression was used to establish the relationship between SSL and the influencing variables. The squared multiple correlation coefficient is R 2 = 0.823. Some further research is suggested with the minerals and pollutants related with the SSL. © 2013 Springer-Verlag Berlin Heidelberg. Source

Jiang D.,CAS Yantai Institute of Coastal Zone Research | Fu X.,Yellow River Institute of Hydraulic Research | Wang K.,Beijing Normal University
Quaternary International | Year: 2013

Based on SPOT Vegetation NDVI data, streamflow data and meteorological data, the variation of vegetation cover, measured by the Normalized Difference Vegetation Index (NDVI), and its response to freshwater inflow, precipitation and temperature in the Yellow River Delta and its buffer zones have been investigated for the period 1998-2009. The results show that NDVI has a remarkable regional and seasonal difference. The farther from the Yellow River Channel and the nearer to the Bohai Sea Coastline, the smaller the NDVI value, as influenced by the interaction between freshwater and saltwater on vegetation. Seasonally, high NDVI values appear in summer (August) and low in spring (April). From 1998 to 2009, growing season NDVI significantly increases in the Yellow River Delta. Summer and autumn NDVI have a similar trend pattern to growing season NDVI, while spring NDVI significantly decreases. NDVI shows different strengths of correlation with freshwater inflow, precipitation and temperature respectively and these correlations vary in different seasons and months. Freshwater inflow is a key factor for vegetation dynamics and NDVI variation. Climate features play a dominant role in seasonal variation in vegetation cover. However, the impacts of freshwater inflow and climate variables on vegetation have been greatly modified by a range of human activities such as land use pattern and land use change as well as water diversion from the Yellow River. Overall, the results of this study can be helpful for decision-making of regional ecological protection and economic development. © 2012 Elsevier Ltd and INQUA. Source

Yang L.,Yellow River Institute of Hydraulic Research
Applied Mechanics and Materials | Year: 2014

After introducing the basic definition, technical principle and applied scope of elastic wave CT technology, the paper makes a detailed introduction of the development process of elastic wave CT technology domestic and overseas and main technical problems it faces and believes that the imagining precision of elastic wave CT is often influenced by various factors such as the observation system, test precision, imaging method and error control. Thereinto, the hot issue in the research is put onto the study about inversion algorithm and the paper also elaborates the research direction and development tendency of current inversion algorithm at home and abroad. © (2014) Trans Tech Publications, Switzerland. Source

Chen J.J.,Yellow River Institute of Hydraulic Research
Applied Mechanics and Materials | Year: 2014

Suction jet scheme has brought forward sediment suspension transport work parameter in the scheme of water and sediment transporting and sediment adding in discharge water before the flood season of Xiaolangdi Reservoir. Suction jet system starts suspended sediments as per 1% natural bottom slope of Xiaolangdi Reservoir while jet pump eject muddy water, which forms into density current and transport forward, and makes longitudinal deposition in the process of sediment transport. Transport distance shall be 1,264~1,903m while 50% longitudinal attenuation of sediments as effective transport distance. Bottom slope of sediment deposition is reduced to 6.7% with obscure longitudinal attenuation of sediments and can transport to longer distance. © (2014) Trans Tech Publications, Switzerland. Source

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