Time filter

Source Type

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.

Ma Y.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research | Huang H.Q.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research | Nanson G.C.,University of Wollongong | Li Y.,Yellow River Institute of Hydraulic Research | Yao W.,Yellow River Institute of Hydraulic Research
Geomorphology | Year: 2012

The Yellow River in China carries an extremely large sediment load. River channel-form and lateral shifting in a dynamic, partly meandering and partly braided reach of the lower Yellow River, have been significantly influenced by construction of Sanmenxia Dam in 1960, Liujiaxia Dam in 1968, Longyangxia Dam in 1985 and Xiaolangdi Dam in 1997. Using observations from Huayuankou Station, 128. km downstream of Xiaolangdi Dam, this study examines changes in the river before and after construction of the dams. The temporal changes in the mean annual flow discharge and mean annual suspended sediment concentration have been strongly influenced by operation of theses dams. Observations of sediment transport coefficient (ratio of sediment concentration to flow discharge), at-a-station hydraulic geometry and bankfull channel form observed from 1951 to 2006 have shown that, although variations in flow and sediment load correspond to different periods of dam operation, changes in channel form are not entirely synchronous with these. The channel has been subject to substantial deposition due to the flushing of sediment from Sanmenxia Dam, resulting in a marked reduction in bankfull cross-sectional area. Flows below bankfull had a greater impact on channel form than higher flows because of very high sediment load. At-a-station hydraulic geometry shows that the variation of channel cross-sectional area below bankfull in this wide and relatively shallow system largely depends on changes in width. Such at-a-station changes are significantly influenced by (1) events below bankfull and (2) overbank floods. Bankfull depth is the main component of channel adjustment in that depth adjusts synchronously with channel area. The channel adjusts its size by relatively uniform changes in depth and width since 1981. Channel morphology is not the product of single channel-forming flow frequency. It is determined by the combination of relatively low flows that play an important role in fine sediment transport and bed configuration as with relatively high flows that are effective at modifying the channel's morphology. The sediment transport coefficient is a useful index for efficiently guiding the operation of the dams in a way that would minimize channel changes downstream. Sedimentation over the nearly 60. years of study period caused the lower Yellow River to aggrade progressively, the only significant exception being the two years following completion of Sanmenxia Dam. © 2011 Elsevier B.V.

Dong N.-H.,China Institute of Water Resources and Hydropower Research | Dong N.-H.,Yellow River Institute of Hydraulic Research
Shuili Xuebao/Journal of Hydraulic Engineering | Year: 2010

Based on field data analysis and mathematical model simulation, the non-equilibrium sediment transport law in the Three Gorges Reservoir under large water depth was studied. It is revealed that, after the reservoir was put into operation, the flood propagates in the form of gravity wave, and the suspended sediment transported from the Cuntan to Huanglingmiao is lagged behind the flood for a long time. By considering the unsteady flood process, the calculated sediment deposited in the reservoir is more than that predicted in the past. Most fine sediment particles are deposited in the reservoir and the different percentage of particles in size does not obviously make the calculation result. This phenomenon can not be explained by non-equilibrium sediment transport theory if the flocculatiou is not considered. When flocculation of fine sediment is taken into account, the simulated reservoir outlet concentration is in good agreement with observation data. It implies that the flocculation may exist in the reservoir and further study on this phenomenon is needed.

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.

Yu S.,Yellow River Institute of Hydraulic Research
Advances in Science and Technology of Water Resources | Year: 2016

In order to examine the effect and possible influence of the implementation of two-bank regulation of the wandering lower Yellow River, through summary of the background of implementation and the expected effect, project and social environmental problems regarding two-bank regulation are analyzed. Although the flood control situation in the lower Yellow River Basin is improved, there exist some problems, such as the insufficient sediment transport capacity of the wandering lower river and the deteriorated river regime of some lower channels. Two-bank regulation can generate a narrow deep channel through spur dikes or other regulation projects, cause most of the sediment to be transported by floods due to the large sediment transport capacity of the narrow deep channel and the operation of the Xiaolangdi Reservoir, and eliminate adverse river regimes, such as transverse rivers and inclined rivers. It is pointed out that the main problems regarding two-bank regulation are as follows: large floods are still likely to occur in the lower Yellow River, the regulation project leads to rises in the water lever, the increasing sediment-carrying capacity causes the discharged sediment to influence the narrow channels in Shandong Province and the Yellow River Estuary, and the implementation of regulation projects leads to land ownership problems, diversion of water from the Yellow River, and environmental impacts. © 2016, Editorial Board of Advances in Science and Technology of Water Resources, Hohai University. All right reserved.

Zeng X.,Wuhan University | Hu T.,Wuhan University | Guo X.,China Institute of Water Resources and Hydropower Research | Li X.,Yellow River Institute of Hydraulic Research
Water Resources Management | Year: 2014

This paper proposes a new water transfer triggering mechanism for multi-reservoir system to divert water from abundant to scarce regions with a constant diversion flow in an inter-basin water transfer-supply project. Taking into account of the uncertain nature of inflow, the storage of reservoir is taken as a signal for decision-making to indicate water abundance or water scarcity. In this study, a set of rule curves based on storage of donor reservoir and storage of recipient reservoir are used together to determine when to start water transfer. To initiate water diversion to each recipient reservoir effectively, several water transfer rule curves of the donor reservoir are set for each recipient reservoir respectively in the multi-reservoir system with one donor reservoir and several recipient reservoirs, which is the main difference in comparison with other water transfer triggering mechanisms. In addition, a systematic framework is developed to integrate the water transfer rule curves with hedging rule curves to simultaneously solve the water transfer and water supply problems, since they interact with each other during the operation process. In order to verify the utility of the new water transfer triggering mechanism, an inter-basin water transfer-supply project in China is used as a case study and an improved particle swarm optimization algorithm (IPSO) with a simulation model is adopted for optimizing the decision variables. The results show that the proposed water transfer triggering mechanism can improve the operation performances of the inter-basin system. © 2014 Springer Science+Business Media Dordrecht.

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.

Qi P.,Yellow River Institute of Hydraulic Research | Qi H.,Parsons Brinckerhoff | Tian S.,Yellow River Institute of Hydraulic Research
Advances in Science and Technology of Water Resources | Year: 2013

With the construction of large hydropower projects on the upper and middle reaches, the development of soil-water conservation and irrigation projects, the probability that a big flood event will occur and flood peak discharges have been greatly reduced. It is unnecessary to widen the lower-reach river to allow floodplain inundation for flood peaks reduction. In recent years, there is a major breakthrough in the understandings of the mechanism and capacity of the sediment transport in the narrow and deep channel of the Yellow River. Lower-reach channel has huge flood discharge and sediment transport capacity, which points out the future direction of harnessing the river. After the reconstruction of Sanmenxia Reservoir and the operational mode of “storing clear water and releasing muddy water” to reduce deposition, non-siltation has already been achieved for the channel upstream of Huayuankou. After the operation of Xiaolangdi Reservoir for 13 years, great changes have taken place in the lower-reach channel with maximum longitudinal water surface elevation reduction of 1.0-2.2 meters, and the bankfull discharge has been increased dramatically. But the wandering reaches are still wide, shallow, scatter and ill-conditioned, and they need to be regulated at both banks to form a stable, deep and narrow channel. Through multi-year sediment regulation of valley type of reservoirs like Xiaolangdi, the combinations of flow and sediment entering the lower-reach can be optimized, and the reservoir can be used for a long time. Sediment should be managed to be released when discharge is greater than 3 000 m3/s, and it should be transported through the regulated new channel to sea. By using this approach, the river bed will not be elevated by deposition, and the beneficial use of the reservoir will be significantly increased too.

Yang L.,Yellow River Institute of Hydraulic Research
Applied Mechanics and Materials | Year: 2012

This essay presents the development history, field of application, research status, and its main products of the technology of ground penetrating radar, and it also discusses the major issues that be faced with by the technology of ground penetrating radar as well as its development direction in the future. © (2012) Trans Tech Publications, Switzerland.

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.

Loading Yellow River Institute of Hydraulic Research collaborators
Loading Yellow River Institute of Hydraulic Research collaborators