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Rivers flow across aeolian dunes and develop braided stream channels. Both aeolian and fluvial sediment supplies regulate sediment transport and deposition in such a cross-dune braided river. Here we show a significant selective deposition in response to both aeolian and fluvial sediment supplies in the Ulan Buh desert braided channel. This selective deposition developed by the interaction between the flows and the Aeolian-fluvial sediment supplies, making the coarser sediments (>0.08 mm) from aeolian sand supply and bank erosion to accumulate in the channel center and the finer fluvial sediments (<0.08 mm) to be deposited on the bar and floodplain surfaces and forming a coarser-grained thalweg bed bounded by finer-grained floodplain surfaces. This lateral selective deposition reduces the downstream sediment transport and is a primary reason for the formation of "above-ground river" in the braided reach of the Upper Yellow River in response to aeolian and fluvial sediment supplies. [ABSTRACT FROM AUTHOR]

Ice disasters occurred frequently in Ningxia-Inner Mongolia reach, and safety of the Yellow River, people's lives and property security are seriously threatened. In this paper ice control condition in the Upper Yellow River is introduced for the first time to clarify the relationship between flow routing and ice control security. Based on the feature of flow routing during ice control period, the improved method for different reaches and periods is proposed in this paper. Three sections in the Ningxia-Inner Mongolia reach of the Upper Yellow River are selected as research objects. The 10-day flow data of sections over the past 20 years are used for parameter calibration, training and verification. To investigate the method performance, we applied a number of criteria factors (Relative Error, Root Mean Square Error, Mean Absolute Error, and Correlation Coefficient) and two methods, conventional method and improved one. The results demonstrate that the improved method which considers ice impact factors such as data on freeze-up and break-up, channel storage increment, temperature, has consistently superior performance in comparison with the conventional method. The accuracy and superiority of the improved method are verified by comparative methods. [ABSTRACT FROM AUTHOR]

Based on remote sensing data and investigations, this paper focuses mainly on a general evaluation of environmental quality in the middle-upper areas of the Yellow River region using GIS technology, Arc/Info, and ArcView. In this paper, the upper areas of the Yellow River regions are divided into three parts: the north-east Qinghai-Tibet Plateau ecosystem areas, the Erdos Plateau-Hetao Plain ecosystem areas, and the Loess-Plateau ecosystem areas. The study analyses the current environmental situation and the overall environmental quality in each ecosystem area and determines the law of distribution of environmental quality in the three areas. Finally, the paper provides some suggestions to improve the ecological environment in each area, in the hope of yielding a scientific foundation based on planning ecological environment protection in the Yellow River basin. [ABSTRACT FROM AUTHOR]

The levels, spatial variation, congener profiles, impact factors, and ecological risk of polychlorinated biphenyls (PCBs) in the sediment from the Yellow River of Henan section, China, were investigated in this paper. Total concentration of 31 PCBs and seven indicator PCBs varied from ND to 1015 pg g−1 and ND to 423 pg g−1, respectively. Compared with other aquatic environments around China, PCB levels in the studied area were relatively low. Spatial variations revealed that tributaries possessed higher PCB levels, in comparison to mainstream, which acted as input sources of PCBs in the mainstream. The homolog profiles were dominated by lighter PCBs (Tri-PentaCBs), contributing above 70% of total PCBs. Correlation analysis between PCB concentrations and total organic carbon indicated that local input or atmospheric deposition was the primary controls of spatial variation of PCBs. According to simple sediment quality guidelines (SQG), the risks posed by PCBs in the sediments might be negligible. [ABSTRACT FROM AUTHOR]

Based on graphical and quantitative methodology of landscape ecology and Geo-information Tupu, this paper studies the landscape spatial-temporal evolution characteristics of the Yellow River Delta (YRD), which was built up by periodic physical swings of the Yellow River (YR) rump channel during 1855-2000. According to the research on spatial-temporal evolution of YRD and YR rump channel, we conclude that the Qingshuigou channel has reached its limit and a new flow channel for YR should be built up sooner or later. It suggests that the shift of YR channel should abide by its natural rules of flowing through depressions among previous channels and could be carried out by artificial efforts. The paper discusses the problems and alternate ways out for treatment of the high content of silt in the YR flow at the estuary. [ABSTRACT FROM AUTHOR]

It has been the conventional assumption that wash load is supply limited and is only indirectly related to the hydraulics of a river. Hydraulic engineers also assumed that bed-material load concentration is independent of wash load concentration. This paper provides a detailed analysis of the Yellow River sediment transport data to determine whether the above assumptions are true and whether wash load concentration can be computed from the original unit stream power formula and the modified unit stream power formula for sediment-laden flows. A systematic and thorough analysis of 1,160 sets of data collected from 9 gauging stations along the Middle and Lower Yellow River confirmed that the method suggested by the conjunctive use of the two formulas can be used to compute wash load, bed-material load, and total load in the Yellow River with accuracy. [ABSTRACT FROM AUTHOR]

Purpose: Few studies have described the bacterial community structures of turbid rivers. In this paper, the characteristics of the bacterial community in the water and surface sediment of the Yellow River, China, the largest turbid river in the world, were studied. Materials and methods: Water and sediment samples were collected from six sites along the river. Bacterial community composition was determined using the 16S ribosomal RNA (rRNA) gene clone library technique. The relationship between environmental parameters and bacterial diversity was analyzed. Results and discussion: A total of 1,131 gene sequences were obtained and clustered into 639 operational taxonomic units (at the 97 % identity level), with Proteobacteria as the predominant phylum. The Shannon index for water samples ranged from 3.39 to 4.40 and was generally higher than that in other rivers; this was probably due to the high suspended particulate sediment (SPS) concentration in the Yellow River, which can provide more habitats for both aerobic and anaerobic bacteria. Also, the bacterial diversity of the water samples was slightly higher than that of the surface sediment samples. The bacterial diversity of water increased along the river in the downstream direction, while there was no trend for the sediment. Redundancy analysis indicated that pH, dissolved organic carbon (DOC), and SPS were the main factors controlling the water bacterial community in the Yellow River, and pH, nitrate-nitrogen, and water content were the main factors for the surface sediment bacterial community. Conclusions: This study indicated that the bacterial diversity of the Yellow River is generally higher than that in other rivers, suggesting that SPS plays an important role in regulating bacterial diversity and community structure in aquatic environments. [ABSTRACT FROM AUTHOR]

In order to verify the feasibility of using microwave to study Yellow River ice, the reflected power of pure ice and mixed ice is measured by electromagnetic waves of different polarisations and frequencies in the microwave chamber. The measured data of microwave chamber measurement was processed to obtain radar cross section values. Based on the experiments in the microwave chamber, this study presents a reflection model for calculating the reflection of pure ice. The calculated value obtained by the model is consistent with the measured values, which also proves the validity of the model. The results of this study will provide some basis for the follow-up study of retrieval Yellow River ice thickness. [ABSTRACT FROM AUTHOR]

ABSTRACT Due to the temporal decoupling of water and sediment sources in a large river basin, a flood from a sediment source area with high suspended sediment concentration (SSC) may be diluted by flow from a major runoff source area with low SSC. In this paper, this dilution effect is considered for 145 flood events from the Yellow River, China. Two indices ( β1 and β2) describing the dilution effect are proposed, based on water and sediment from the clear water source area and the coarse sediment producing area. Regression equations between channel sedimentation ( Sdep) and β1 and β2 are established based on flood events and annual data, respectively. The results show that dilution reduces channel sedimentation in the lower reaches by 34∙1% and that this is related to a reduced frequency of hyperconcentrated flows in the lower reaches. The Longyangxia Reservoir for hydro-electric generation has stored huge quantities of clear runoff from the upper Yellow River during high-flow season since 1985, greatly reducing the dilution of the hyperconcentrated floods and therefore enhancing sedimentation in the lower reaches. For the purpose of reducing sedimentation, changing the operational mode of the Longyangxia Reservoir to restore the dilution effect is suggested. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

An economic valuation of flood reductions arising from land use changes induced by the Conversion of Cropland to Forest and Grassland Program (CCFGP) in China is detailed in this paper. A distributed hydrologic model is used to analyze and predict changes in the probability of flood occurrences in the Yellow River Basin (YRB) due to revegetation activities under the CCFGP. The expected value of flood reductions due to the avoided flood damage potential is then estimated. Losses brought about by each type of flood in the YRB over time and the probability change in flood occurrences are used in the calculation. Results show that the economic benefits from flood reductions will total China Yuan 362 million during 2010–2020. The inclusion of this economic benefit into a benefit-cost analysis of the CCFGP provides a more comprehensive assessment of the program. Implications for prioritizing management options to mitigate flood disasters in the YRB are drawn. [ABSTRACT FROM AUTHOR]

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Due to the water resource shortage in the lower reaches of the Yellow River in recent years, this paper presents a study on water dispatching. From the view of temporal and spatial allocation of water resources) water dispatching consists of two components: reservoir regulation and water dispatching for reaches in order to implement the total volume control and coordination between users. The combined regulation model of Sanmenxia reservoir and Xiaolangdi reservoir giving full consideration to the priorities of user's water demands, conforms to the reality of the Yellow River The water-dispatching model for reaches applies various methods including the equal proportion method, weighting method, and user-involving method, which are characteristic of simplification, flexibility, and practice. In addition, the influence of flow routine time has also been considered to enable the water-dispatching scenarios obtained to be more practical The methods and models have been applied in the praxis of water dispatching in the lower reaches of Yellow River in 2000 and have resulted in significant economic and social benefits. [ABSTRACT FROM AUTHOR]

The fluvial processes are considerably complicated in the braided reach of the Lower Yellow River; and the lateral or transverse channel deformation process is especially pronounced. The state-of-the-art of simulation techniques for the channel deformation in the Lower Yellow River was analyzed in this paper, and such a conclusion was drawn that existing mathematical alluvial models only can simulate the longitudinal channel deformation and cannot simulate such the lateral deformation as lateral erosion and failure of bank. Then a new two-dimensional (2D) composite model was developed herein, consisting of a 2D flow and sediment transport submodel and a riverbank-erosion submodel. This model not only can simulate the longitudinal and lateral channel deformations, but also can be used to simulate the fluvial processes of natural alluvial rivers with complex bed morphology. Through using the proposed composite model, the flood routing and channel deformation processes during the August 1982 flood were simulated. The maximum stage along the reach and the discharge hydrograph at the outlet so obtained were in good agreement with the observed data. Simulated results of the channel deformation processes showed that during the flood season, the main channel scours and the flood plain deposits; during the dry season, the main channel deposits and banks of the floodplain retreat due to lateral erosion by the flow and failure under gravity. Such results accord with the annual varying law of bed scouring and deposition in the braided reach. [ABSTRACT FROM AUTHOR]

A series of annual natural runoff recorded at eight hydrological stations in the Yellow River basin (YRB) and distributed at the main channel and two sub-basins (Weihe basin and Fenhe basin) are studied during the period from 1951 to 1998. The trends and the beginning points (or abrupt changes) of these series are detected with Mann-Kendall test (M-K test) and its progressive application. The results show that there are similar trends for different stations. The annual natural runoff series, except for stations of Lanzhou, Hekouzhen, and Longmen, have a downward tendency at some stations whose beginning points of the trend or abrupt changes occurred in the early or mid 1990s. However, their initial years of decrease are different. The decreasing trend of runoff has led to drying-up in lower reaches of the YRB, a water resources scarcity crisis, and a deterioration of the ecosystem. The reasons for the trends have been analyzed in this paper The trends of precipitation in the corresponding regions are similar to those of annual natural runoff It is an important aspect for runoff decrease. In addition, human activities have changed the hydrological cycle and lead to a reduction in runoff to a certain degree. Finally, two countermeasures for the runoff decrease are put forward. One is to develop water savings in irrigation regions, and the other is to plan South-to-North water transfer projects for the YRB. However the conflict between supply and demand will still exist for a long time because of the water scarcity in the future. [ABSTRACT FROM AUTHOR]

In recent decades, the streamflow and sediment of the Yellow River has decreased sharply, especially the sediment discharge. The factors that lead to this phenomenon have become a widely concerned problem of the whole society. The analysis of abrupt change points of hydrological series is the key to divide datum period, so it is an important work in the research of streamflow and sediment reduction cause. So far, many methods have been proposed to detect abrupt change. However, most methods have great uncertainty due to the deficiencies of irrational structure of test statistics, ideal hypothesis or subjectivity. In this paper, a new method called moving average difference method for abrupt change points detection is proposed. It is proved to be effective through comparison with four commonly used methods via both synthetic series and real data case study. The results show that the proposed method has four distinct advantages: (1) The test statistic structure of the method has physical significance and is intuitive to understand; (2) It is more accurate in abrupt change detection; (3) It can detect all of the abrupt change points at one time; (4) It can detect the abrupt changes and calculate the corresponding mutation intensity simultaneously. [ABSTRACT FROM AUTHOR]

Abstract: The suspended sediment deposition (SSD) in the alluvial reach between the Qingtongxia station and the Toudaoguai station of the upper Yellow River has shown a dramatic variation since 1952. However, its spatial and temporal changing pattern and driving factors are still not clear. This paper examines the detailed spatial and temporal variations of the SSD based on the annual suspended sediment load at five gaging stations located in this alluvial reach in 1952–2007. The mean annual SSDs in four sub-reaches (Qingtongxia–Shizuishan, Shizuishan–Bayangaole, Bayangaole–Sanhuhekou, and Sanhuhekou–Toudaoguai) were calculated and analyzed for different periods. The mean annual kilometric SSDs in 1952–2007 were −0.228∗105, 0.97∗105, 0.165∗105 and 0.006∗105 ta−1 km−1 in the four sub-reaches, respectively, with the highest SSD occurred in the Shizuishan–Bayangaole sub-reach. Results also suggested that SSD was mainly accumulated in 1952–1959 before major reservoirs were constructed and in 1986–2007 after three major reservoirs (Qingtongxia, Liujiaxia and Longyangxia) were constructed in the main stream. During 1960–1985, all sub-reaches except the Shizuishan–Bayangaole sub-reach experienced channel erosion. Although climate change may play some roles, the changes in SSD were mainly influenced by human activities. In particular, the water and soil conservation actions, such as the construction of check dams from 1958 in upper stream tributaries, intercepted significant amount of suspended sediment and cause the net erosion of the main channel in the 1960s. The operation of the Qingtongxia reservoir reduced the SSD in this downstream reach in the 1970s and 1980s because upper stream suspended sediment was trapped by the reservoir and reservoir-released relative clear water scoured the downstream channel. Although the Liujiaxia and Longyangxia reservoirs trapped relatively small amount of suspended sediment, they stored a large amount of water during the flood season, reducing the discharge and the erosion capability of the downstream flow. Therefore, this operation mode may increase the SSD in this river reach. In addition, with the gradual loss of the Qingtongxia reservoir''s capacity in sediment storage, more suspended sediment was released to the downstream channel, causing strong SSD in this reach after 1990. [Copyright &y& Elsevier]

Abstract: Wetland, located in the terrestrial-aquatic transverse zone, is an important landscape and ecosystem. This paper describe the features and functions of wetlands, and take the case of lower reaches of the Yellow River wetlands, analysis on existing problems of ecological safety on wetland in lower reaches of the Yellow River. Using of GIS and two-dimensional water-sediment mathematical model of the Lower Yellow River, in accordance with the requirement of wetland areas, submerged areas for floods of below the 8000m3 /s magnitude designated as different functional areas. The ideal patterns of ecological security on the wetlands are divided into the core zone, buffer zone and experiment zone. [Copyright &y& Elsevier]

This paper proposes using an interactive fuzzy satisfying method to solve multi-objective optimization problems in integrated water management of the Yellow River Delta, China. The approach involves economic, social and ecological objectives represented by net returns, water deficiency and ecological water requirements, respectively. It considers the decision-maker’s preferences in terms of fuzzy satisfying of each objective and holistic satisfying of all objectives based on Euclid distance. The method avoids the subjectivity of having decision-makers assigning weights to the multiple objectives to some degree. The method is applied to the Yellow River Delta, China. Results indicate that considerably more water should be allocated to ecological uses of water in the Yellow River than currently occurs. An interactive fuzzy satisfying approach for the multi-objective optimization problems has significant potential in the field of integrated water management. [ABSTRACT FROM AUTHOR]

Base-flow separation has long been an important research topic in hydrology. In the Yellow River Basin in China, base flow is of special concern in the headwater catchments because of its importance for integrated water resources management in the basin as a whole. To quantify base flow in the headwater catchments of the Yellow River Basin for 1956–2000, the two-parameter Kalinin method has been proposed with improved implementation procedures and parametrization techniques. Results show that base flow contributes a larger proportion to streamflow in the headwater catchments than that of surface flow, but with a rather low variation. The results are consistent with that of the other two digital filter methods. Sensitivity analysis of parameter performance in the Kalinin method shows, in detail, that the hydrograph of separated base flow is sensitive to a recession constant, and the other parameter (β) is highly related to the base-flow index and the ratio of base flow against surface flow (δ). [ABSTRACT FROM AUTHOR]

Great achievements have been gained in assuring the safety of the lower Yellow River through arduous work in the past fifty years. But the disadvantages of boundary for river-flow are obvious, such as topography, tectonic movement and crustal stability. The main conflicts of less water and more sand, and the speeding up of sedimentation still exist, causing continuous river shrinkage. However, all the existing methods cannot completely avoid flood catastrophe, so a new control method needs to be explored. The method of changing-route based on geographical theory has always been a focus of debate over whether there are other feasible routes for the current Yellow River. From geoscientific point of view, this paper investigates whether there is a best feasible reservation route in Huang-Huai-Hai plain. Under the actual condition that the conflict between water and sand cannot be eradicated, the selection of the best reservation route should be the overlaying area of the optimum boundary conditions and the less social and economic loss. By detailed analysis of topography, tectonic movement, crustal stability and social-economic progress in the region of the lower Yellow River, the best reservation route is obtained by using the distance weighted function and the minimum cost function. The analysis result indicates that the reservation route can get rid of the influence of the elevation in central western Shandong Province, and the whole route flows through the Hal-Huang rift valley, which is good for channel stability. As to the basic parameters of water and sand movements, the gradient increases 36.2%, the length shortens 15.4% and the curvature reduces 12.2%. Using the reservation route can comparatively reduce the flood risk of the Yellow River, except that it will induce such problems as resettlement and relocation of towns, infrastructure reconstruction, water shortage in the abandoned area of the present route, as well as the resultant ecological and environmental degradation. But in contrast to the huge accumulative input to the harnessing of the Yellow River by the state, the absolute input of dealing with the above-mentioned problems is still acceptable. In the construction of corresponding infrastructures, using the reservation route will promote the region's socio-economic development and offer a rare chance of burgeoning. [ABSTRACT FROM AUTHOR]

This paper analyses the processes and mechanisms of a three-stage channel adjustment over a cycle of the Yellow River mouth channel extension based on data comprising hydrologic measurements and channel geometric surveys. Rapid siltation in the mouth channel takes place in the young stage when the channel is being built by deposits and in the old stage when the channel cannot further adjust itself to keep sediment transport in equilibrium. It is disclosed that the bankfull width–depth ratio, bed material size and slope decrease in the young and mature stages but do not change in the old stage. The reduction of bankfull width–depth ratio and bed material size during the young and mature stages is found to be able to offset the effect of the slope reduction on sediment transport due to continuous mouth progradation. They reach their limits in old stage, and a constant slope is kept by unceasing sediment accumulation. The grain size composition of incoming sediment and the fining mechanism are responsible for the occurrence of lower limit of bed material size. The reason for the existence of a limit of bankfull cross-sectional shape is that the large flows can fully transport the sediment load they are carrying, and siltation in the channel in the old stage takes place mainly in the low flows. It is suggested that the bankfull discharge plays an important role in shaping the channel but that the entire channel form is the product of both the large and low flows plus the effects of interaction between them. Channel pattern change shows a process from a braided pattern in the young stage to a straight pattern in the mature and old stages, and the straight channel becomes gradually sinuous. The occurrence and transformation of the channel patterns are supported by two planform predictors, but are also facilitated by some other conditions. Copyright © 2003 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: This paper is to highlight the threatening of climate change on the water shortage problem in North China, a semi-arid and arid area. Observations show that the runoff of the major rivers is decreasing dramatically especially in the lower reaches where water ishighly demanded. Most noticeable are the dry-outs of the Yellow River, the so-called ‘mother river of China’.Water scarcity would be the most front challenge for the society and economy in China, especially the urban area with extremely high population density. The government already paid attention to the deepening of the underground water level at Beijing. Sustainable water resource management should the top priority for the local community to adapt to climate change. Studies show that human activities heavily impact on the local climate and environment in China and a dramatics amount of clean water is wasted or polluted. [Copyright &y& Elsevier]

In recent decades, climate change has affected vegetation growth in terrestrial ecosystems. We investigated spatial and temporal patterns of vegetation cover on the Loess Plateau's Shaanxi-Gansu-Ningxia region in central China using MODIS-NDVI data for 2000-2014. We examined the roles of regional climate change and human activities in vegetation restoration, particularly from 1999 when conversion of sloping farmland to forestland or grassland began under the national Grain-for-Green program. Our results indicated a general upward trend in average NDVI values in the study area. The region's annual growth rate greatly exceeded those of the Three-North Shelter Forest, the upper reaches of the Yellow River, the Qinling-Daba Mountains, and the Three-River Headwater region. The green vegetation zone has been annually extending from the southeast toward the northwest, with about 97.4% of the region evidencing an upward trend in vegetation cover. The NDVI trend and fluctuation characteristics indicate the occurrence of vegetation restoration in the study region, with gradual vegetation stabilization associated with 15 years of ecological engineering projects. Under favorable climatic conditions, increasing local vegetation cover is primarily attributable to ecosystem reconstruction projects. However, our findings indicate a growing risk of vegetation degradation in the northern part of Shaanxi Province as a result of energy production facilities and chemical industry infrastructure, and increasing exploitation of mineral resources. [ABSTRACT FROM AUTHOR]

The Sanmenxia Dam built in 1960 in the middle reach of the Yellow River has experienced severe sedimentation problems, not only in the reservoir area itself but also extending hundreds of kilometers in the backwater region. Morphological responses in the middle Yellow River and its tributary, the Wei River, upstream of the dam have generally lagged behind the causal changes in upstream and downstream controls. Based on the geometrical characteristics of a wedge-shaped sedimentation body, a method was derived for calculating equilibrium values of the accumulated sedimentation volume in the channel reaches. Combining the method for calculating with rate law models for channel morphological adjustment, a method for calculating the accumulated deposition volumes was derived. The results showed that the proposed method can accurately simulate sedimentation processes in the study reaches during 1960 and 2011, in the response to the integrated impacts of base level fluctuations and changes in incoming water and sediment discharges. The characteristics of the potential adjusted (equilibrium) morphology was analyzed and it is shown that while the nature of the adjusted (or equilibrium state) of the fluvial system varies dynamically with external conditions, it generally acts as the target for the observed channel adjustments, although the actual values of variables defining the fluvial system seldom adjust to their corresponding equilibrium values due to the effects of multiple disruptions, continuously varying water and sediment inputs, and delayed responses in the fluvial system. [ABSTRACT FROM AUTHOR]

Under the impacts of climate variability and human activities, there are statistically significant decreasing trends for streamflow in the Yellow River basin, China. Therefore, it is crucial to separate the impacts of climate variability and human activities on streamflow decrease for better water resources planning and management. In this study, the Qinhe River basin (QRB), a typical sub-basin in the middle reach of the Yellow River, was chosen as the study area to assess the impacts of climate variability and human activities on streamflow decrease. The trend and breakpoint of observed annual streamflow from 1956 to 2010 were identified by the nonparametric Mann-Kendall test. The results showed that the observed annual streamflow decreased significantly ( P < 0.05) and a breakpoint around 1973 was detected. Therefore, the time series was divided into two periods: 'natural period' (before the breakpoint) and 'impacted period' (after the breakpoint). The observed annual streamflow decreased by 68.1 mm from 102.3 to 34.2 mm in the two periods. The climate elasticity method and hydrological model were employed to separate the impacts of climate variability and human activities on streamflow decrease. The results indicated that climate variability was responsible for 54.1 % of the streamflow decrease estimated by the climate elasticity method and 59.3 % estimated by the hydrological modeling method. Therefore, the climate variability was the main driving factor for streamflow decrease in the QRB. Among these driving factors of natural and anthropogenic, decrease in precipitation and increase in water diversion were the two major contributions of streamflow reduction. The finding in this study can serve as a reference for regional water resources management and planning. [ABSTRACT FROM AUTHOR]

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 = 0.823. Some further research is suggested with the minerals and pollutants related with the SSL. [ABSTRACT FROM AUTHOR]

The eco-hydrological requirements of a river are related to the health of the river. In recent years, changing climate and intensifying human activities have further aggravated water problems in the Yellow River. Considering hydrological changes, this study addressed the ecological water requirements of the Yellow River basin, wherein the threshold ecological water requirement corresponded to the streamflow with the largest occurrence probability determined by the Pearson Type III distribution. Instream flow ± one standard deviation was adopted as the water resource management target and abrupt changes in streamflow were detected by using the Mann-Whitney test. The results of the analysis indicated that: (1) the annual flow of the Yellow River substantially decreased after abrupt changes and the probability significantly dropped that the amount of annual streamflow satisfied the ecological instream flow requirement; and (2) the water resource management target was satisfied well after th echange point only at the Tangnaihai station, located in the upper Yellow River basin. From the upper to the lower Yellow River basins, the probability has dramatically decreased that the ecological water requirement target is satisfied. Therefore, the Yellow River basin will likely face increasingly serious water problems, particularly in the middle and lower parts. [ABSTRACT FROM AUTHOR]

We analyze 4000-year flood history of the lower Yellow River and the history of agricultural development in the middle river by investigating historical writings and quantitative time series data of environmental changes in the river basin. Flood dynamics are characterized by positive feedback loops, critical thresholds of natural processes, and abrupt transitions caused by socio-economic factors. Technological and organizational innovations were dominant driving forces of the flood history. The popularization of iron plows and embankment of the lower river in the 4th century bc initiated a positive feedback loop on levee breaches. The strength of the feedback loop was enhanced by farming of coarse-sediment producing areas, steep hillslope cultivation, and a new river management paradigm, and finally pushed the flood frequency to its climax in the seventeenth century. The co-evolution of river dynamics and Chinese society is remarkable, especially farming and soil erosion in the middle river, and central authority and river management in the lower river. [ABSTRACT FROM AUTHOR]

A holistic approach using multiple modules is used to recommend the environmental flow for fish in the lower Yellow River. The basic steps are as follows: (1) acquire the flow-related information on selected fish in the lower Yellow River, including fish species composition, abundance and habitat use in relation to flow conditions; (2) link the selected fish to key aspects of the flow regime using a conceptual model; (3) identify the environmental flow objectives; and (4) use hydraulic and hydrologic models to determine the magnitude, duration, frequency and timing of flows required to meet these objectives. [ABSTRACT FROM AUTHOR]

The Yellow River in China carries large amounts of sediments in suspension at concentrations up to several hundreds of kilograms per cubic metre; the sediment is composed mainly of silt. These high sediment concentrations influence the hydrodynamics (flow velocity and turbulence) which, in turn, determine the sediment concentration profile, whereas both the high sediment concentrations and pseudo-cohesive properties of silt determine the morphodynamics of the Yellow River. The effect of sediment on the hydrodynamics is analysed using the Richardson number and the Reynolds number to provide a framework to differentiate between various flow regimes in the Yellow River, which is calibrated and validated with Yellow River data. The flow may be sub-saturated (stable flow), super-saturated (unstable flow characterized by high deposition rates, caused by collapse of turbulence), or hyperconcentrated sub-saturated (stable flow because of hindered settling effects), depending on the Richardson number. Independent of this, the flow may be turbulent, transitional or laminar, depending on the Reynolds number. Analysis of these flow types improves understanding of the flow regimes and morphodynamics of the Yellow River. The morphodynamics of the Yellow River are also affected by pseudo-cohesive behaviour caused by shear dilatance, which results in increasing critical shear stress for erosion at decreasing grain-size. This pseudo-cohesive behaviour may be partly responsible not only for the high deposition rates which characterize the lower Yellow River, but also for mass erosion during river floods. [ABSTRACT FROM AUTHOR]

There has been growing interest in the use of reflectance spectroscopy as a rapid and inexpensive tool for soil characterization. In this study, we collected 95 soil samples from the Yellow River Delta of China to investigate the level of soil salinity in relation to soil spectra. Sample plots were selected based on a field investigation and the corresponding soil salinity classification map to maximize variations of saline characteristics in the soil. Spectral reflectances of air-dried soil samples were measured using an Analytical Spectral Device (ASD) spectrometer (350-2500 nm) with an artificial light source. In the Yellow River Delta, the dominant chemical in the saline soil was NaCl and MgCl2. Soil spectra were analysed using two-thirds of the available samples, with the remaining one-third withheld for validation purposes. The analysis indicated that with some preprocessing, the reflectance at 1931-2123 nm and 2153-2254 nm was highly correlated with soil salt content (S SC). In the spectral region of 1931-2123 nm, the correlation R ranged from -0.80 to -0.87. In the region of 2153-2254 nm, the S SC was positively correlated with preprocessed reflectance (0.79-0.88). The preprocessing was done by fitting a convex hull to the reflectance curve and dividing the spectral reflectance by the value of the corresponding convex hull band by band. This process is called continuum removal, and the resulting ratio is called continuum removed reflectance (CR reflectance). However, the S SC did not have a high correlation with the unprocessed reflectance, and the correlation was always negative in the entire spectrum (350-2500 nm) with the strongest negative correlation at 1981 nm (R = -0.63). Moreover, we found a strong correlation (R = 0.91) between a soil salinity index (S SI: constructed using CR reflectance at 2052 nm and 2203 nm) and S SC. We estimated S SC as a function of S SI and S SI' (S SI': constructed using unprocessed reflectance at 2052 nm and 2203 nm) using univariate regression. Validation of the estimation of S SC was conducted by comparing the estimated S SC with the holdout sample points. The comparison produced an estimated root mean squared error (RMSE) of 0.986 (S SC ranging from 0.06 to 12.30 g kg-1) and R 2 of 0.873 for S SC with S SI as independent variable and RMSE of 1.248 and R 2 of 0.8 for S SC with S SI' as independent variable. This study showed that a soil salinity index developed for CR reflectance at 2052 nm and 2203 nm on the basis of spectral absorption features of saline soil can be used as a quick and inexpensive method for soil salt-content estimation. [ABSTRACT FROM AUTHOR]

The article discusses the possibility that the glaciers of the Tibetan plateau could be melted by global warming. This would lead to short-term floods and long-term drought for large sections of Asia, including China and India. Scientific studies are cited which indicate that glaciers around the world began to diminish in the 1950's, staged a modest comeback in the 1970's, and rapidly began shrinking again in the 1980's. Large and geopolitically important river systems such as the Yellow River and the Mekong are dependent on water from the glaciers of the Tibetan plateau.

The article provides information about a study conducted on the spatial variability of hydrologic alterations caused by the dam construction along the middle and lower Yellow River in China for the past five decades. It focuses on the impacts of human activities like dam construction on hydrological processes. It also indicates the results of the study that include the impacts of the Sanmexia reservoir on the hydrologic alteration, the changes on the Xiaolangdi reservoir and the impacts of reservoirs on hydrological processes downstream of the dams. In addition, it discusses climate change as a cause of alterations of streamflow regimes. Moreover, it presents the significance of the study.

The spatial and temporal variability of winter extreme low-temperature events and summer extreme high-temperature events was investigated using daily air temperature series (1960–2004) from 66 sites in the Yellow River basin, China, with the help of Mann–Kendall trend test method. In this study an extreme temperature event is defined by exceeding or falling below various threshold values of daily maximum and daily minimum air temperature: 90th percentile, 95th percentile for the high-temperature events; 10th percentile and 5th percentile for the low-temperature events. The analysis results indicate that: 1) significant upward trend of frequency and intensity of the high-temperature events is found in the stations in the west and north part of the Yellow River basin, but trends in most stations in the middle and lower Yellow River basin are not significant at >95% confidence level; 2) almost the whole Yellow River basin is dominated by the significant downward trend of frequency of the cold events. Stations featured by the increasing winter minimum temperature are also more than those featured by changing summer maximum temperature; and 3) annual warming trend in the Yellow River basin mainly results from the increase in winter minimum temperature. Significant warming in the upper reach of the Yellow River will be likely to threaten the availability of the water resource in the whole basin, which should draw certain concerns from local policy-makers and water resource management agency in the region. [ABSTRACT FROM AUTHOR]

Climatological features and variations of wet spells, especially their trends over China, are investigated using a dataset of 594 meteorological stations across China from 1951 to 2003. The results show that the lower the latitude is, the longer the annual duration of wet spells is. The mean annual precipitation from wet spells is higher in southeastern coastal areas and much lower in western and northern China. The longest wet spells are found in Southwest China and the eastern Tibetan Plateau. The maximum daily precipitation of wet spells decreases from the southeast to the northwest, with the highest in southeastern coastal areas and the lowest in western China. The trends of wet spells exhibit striking regional differences. In most areas of western China, the annual number of days in wet spells has slightly increased, but significantly decreased over North China, Central China and Southwest China. The annual precipitation amount from wet spells displays significant downward trends in North China, eastern Northeast China and the eastern part of Southwest China, but upward trends in the eastern Tibetan Plateau and some southeastern coastal areas. Two clearly-contrasting regions in climatic changes of wet spells are the mid-lower reaches of the Yellow River and the eastern Tibetan Plateau, characterized by a decrease of about 24 days and an increase of about 6 days in annual wet spell days from 1953 to 2003, respectively. [ABSTRACT FROM AUTHOR]

Based on monitoring data of 123 meteorological stations from 1960 to 2000 near or in the Yellow River Basin, the spatial and temporal distributions and their trends for pan evaporation (PE) are investigated in this study. The results indicate that, despite the annual mean air temperature over the Yellow River Basin has, on average, increased by 0.6° over the past 40 years, the rate of PE has steadily decreased, especially in summer and spring. Compared with the period of 1960s to 1970s, the rate of annual pan evaporation during 1980s to 1990s has decreased by 126mm or 7.0 percent Spatial distribution of the rate of change show that this kind of trend is general but not universal, PE has significantly decreased over the upper and lower reaches of the Yellow River, but increased to a small degree over the middle reaches. Further analyses show that the decrease of PE is mainly related to reductions in sunshine durations and solar irradiance, owing to more clouds and aerosols. [ABSTRACT FROM AUTHOR]

Variation of δ18O, δD, and ³H in the Yellow River water were analyzed based on the isotope test results of water samples in 18 sections of the Yellow River in rainy and dry seasons. The results show the trend of the ratios of the stable isotopes increases while the ³H concentration decreases progressively from the river source to the estuary. The main factors affecting the isotopes in the river water are the mixing of foreign water bodies, evaporation, and human activities. River runoff mostly comes from the source and the middle reaches of the river. The changes of the isotopes in the river water could be served as a good indicator of the recharge of different foreign water to the Yellow River. [ABSTRACT FROM AUTHOR]

The Yellow River with high silt concentration is the main source of domestic water supply for downstream cities. After desilting, 85% silt is removed but fine suspended particles remain in the water, which may cause health and environmental risks, and the traditional water treatment technology by a water plant is ineffective in removing fine suspended particles. Atrazine is one of eight priority-controlled trace organic pollutants in Yellow River water. As one of the effective measures, managed aquifer recharge (MAR) is adopted to improve the Yellow River water quality. The model of colloid-associated atrazine transport is simulated at laboratory scale. The migration experiment of atrazine in heterogeneous porous medium (non-uniformity coefficient of 25.2) with saturated and steady flow is conducted under sand washing condition. The observed data of breakthrough curves are numerically simulated using convection-dispersion equation and CXTFIT 2.1 software. Results show that in the absence of montmorillonite, atrazine reaches a peak at approximately 100 min, and the peak is 82% of the initial value; whereas in the presence of montmorillonite, atrazine reaches a peak at approximately 55 min. Thus, atrazine can be absorbed on colloidal particles and spread in the area, and the remaining atrazine aggravates the risk of pollution for groundwater environment. Therefore, preventive measures should be considered in the MAR system to reduce the exogenous colloid into the aquifer, it is significant for sustainable MAR operations. Equilibrium and non-equilibrium models can better fit the experimental data and can be utilized to analyze the colloid-assisted atrazine transport in saturated heterogeneous porous media under a steady state. [ABSTRACT FROM AUTHOR]