Search

The Qingtongxia Grand Canyon (QGC) of the Yellow River is a region of intense tectonic deformation that is located in the southern Yinchuan Basin, at the junction of the western margin of the Ordos Plateau and the northeast arcuate structural belt of the Qinghai–Tibetan Plateau. The Yellow River makes a 90° turn as it traverses the Qingtongxia area, incising the hard Ordovician sandstones of Niushou Mountain, while leaving the relatively soft Quaternary sediments on the northern side of the channel undisturbed. Despite this apparent inconsistency with the expected pattern of river erosion, there has been no significant research to date on the formation of the QGC. Here, we utilize remote sensing, surficial geomorphology, and shallow coring to confirm the evolution of the Yellow River channel and formation of the QGC. Using Landsat Thermic Mapper and ASTER imagery, we identified a N–S‐oriented zone of high water‐content in the northern part of the QGC that is characterized at the surface by marsh and wetlands. Shallow cores reveal the zone is underlain by Yellow River gravel, while seismic profiling confirms anomalous seismic structures relative to the surrounding strata. Together, these data document a paleo‐Yellow River channel in the northern Qingtongxia area. We selected four representative profiles of the Yellow River terraces in the Qingtongxia and adjacent areas to acquire measurements on above water level and age. The uppermost terraces preserved at the entrance, central section, and exit of the QGC are labelled T6, T9, and T3, respectively. Our data indicate that the flow direction during the construction of T9 was different to that of the modern Yellow River and that canyon incision occurred during the development of T3, which we constrain to 65–85 ka. Ultimately, we (a) document a paleo‐Yellow River channel north of the QGC, which may have been affected by tectonic activity since the late Pleistocene and (b) show that the Yellow River has since been diverted towards the Yinchuan Basin via the QGC. [ABSTRACT FROM AUTHOR]

The Yellow River (YR) is the fifth-longest and the most sediment-laden river in the world. Frequent historical YR flooding events, however, have resulted in tremendous loss of life and property, whereas in recent decades YR runoff and sediment load have fallen sharply. To put these recent changes in a longer-term context, we reconstructed natural runoff for the middle reach of the YR back to 1492 CE using a network of 31 moisture-sensitive tree-ring width chronologies. Prior to anthropogenic interference that started in the 1960s, the lowest natural runoff over the past 500 y occurred during 1926 to 1932 CE, a drought period that can serve as a benchmark for future planning of YR water allocation. Since the late 1980s, the low observed YR runoff has exceeded the natural range of runoff variability, a consequence of the combination of decreasing precipitation and increasing water consumption by direct and indirect human activities, particularly agricultural irrigation. This reduced runoff has resulted in an estimated 58% reduction of the sediment load in the upper reach of the YR and 29% reduction in the middle reach. [ABSTRACT FROM AUTHOR]

This study analyzed the wintertime surface heat exchange for the Inner Mongolia reach of the Yellow River, China, based on the data from the nearby weather station at Wulateqianqi. In this analysis, the solar radiation is based on the observed data. Other components of the surface heat flux, that is, long‐wave radiation, and evaporative and conductive heat fluxes, are calculated. The relative importance of the contributions of long‐wave radiation, conductive, and evaporative heat fluxes are in descending order. The air temperature is the most important meteorological factor to the total heat flux. Although the wind speed influences evaporative and conductive heat fluxes, it has the least correlation with the total heat budget. The heat exchange coefficient for the linearized surface heat exchange equation is 21.87 W/(m2 °C), which is comparable with published values in the regions of United States and Canada with similar latitudes. Research Impact Statement: Wintertime surface heat exchange plays an important role on water temperature and ice conditions in cold region rivers. The surface heat exchange for the Inner Mongolia region is analyzed. [ABSTRACT FROM AUTHOR]

Based on historical records, we investigated the dynamic conditions, geomorphological characteristics, and evolution mechanisms of the Huaihe River estuary during the period of Yellow River invasion. The results showed that the runoff and sediment discharge of the Huaihe River increased owing to a large quantity of sediment-laden runoff into the Yellow River from 1128 to 1855 CE. However, the sediment discharge in different periods is also affected by repeated siltation along the lower reaches of the Yellow River. Huaihe estuary is a tidal estuary with moderate intensity. Its reciprocating tidal current and coastal current system are favorable to the discharge of sediment into the sea. The shape of the Huaihe estuary is narrow on the upper side and wide on the lower side. Large-scale sandbar and underwater delta were developed in the inside and outside of the estuary, respectively. The channel of the estuary has a typical curved river type, and the width of the estuary has had an increasing trend since the 18th century. The evolution mechanism of the Huaihe estuary is that the tidal current limit continuously moves downstream, and the estuary continuously extends to the sea. In addition, the downstream movement distance of the tidal current limit is much longer than that of the outward extension of the estuary during the same period, resulting in a significant shortening of the estuary section. To satisfy the energy demand by runoff and tidal current, the river type of the estuary section becomes meandering and the entrance is widened. The ancient Huaihe River estuary and the modern Yellow River estuary have different dynamic geomorphological characteristics and evolution mechanisms, which cannot be simply analogized. [ABSTRACT FROM AUTHOR]

Through the geochemical analysis of two hundred-meters cores KD4 and ZK3 from Laizhou Bay, in this study, we determined the distribution law and controlling factors of the geochemical elements. We analyzed 24 elements with respect to their R factors and major principal components, which were combined with the source discrimination functions DFCr/Th and DFCa/Al to obtain the sediment source index and its variation with depth for this area. A comparison of the changes in climate indicators suggests a clear correlation between the source and climate changes. The results show that the Yellow River and surrounding short-term rivers are the main sediment sources in this area. The PC3 of the KD4 core and PC2 of the ZK3 core (e.g., CaO, MnO, SiO2) exhibit significant variations and reflect the relative contributions of Yellow River sources. The deposition process can be divided into six stages: in Phase I (MIS 5c-MIS 5a), the Yellow River formed, and the composition of the Yellow River had a greater influence on the sedimentary composition of the study area. In Phase II (MIS 5a-MIS 3), the sediment sources of the Yellow River and the short-term streams in this area were wavering, with the sediments derived from short-term rivers playing a more important role. In Phase III (MIS 3), with a sharp drop in temperature, the study area was in the process of retreat, and the sediment source changed from the Yellow River to short-term rivers, after which the Yellow River source material remained the main sediment source for the region. A similar process occurred three more times in Phase IV (MIS 3-MIS 2), Phase V (MIS 2-MIS 1), and Phase VI (MIS 1). With changes in climate, especially during alternating sea-land phases, the sediment source varied in marine-terrestrial-marine phases, and the changes are observed as Yellow River source-surrounding provenance-Yellow River source. However, this process of change is not synchronized with the sea-land strata alternation. [ABSTRACT FROM AUTHOR]

A systematic study of the wind regime characteristics in a region can not only accurately grasp the dynamic factors of the development of aeolian geomorphology, but also provide a scientific basis for the prevention and treatment of regional sand disasters. Taking the Hobq Desert as the study area, the basic characteristics of dune are analyzed by using remote sensing images. Based on the annual meteorological data of six meteorological stations from 2009 to 2018, the spatial and temporal distribution characteristics of wind speed were obtained. With the daily wind data of three stations from 2009 to 2018, we have figured out the wind regime and sand transport characteristics of the Hobq Desert. The results show that the sand dune height of the Hobq Desert ranges large, the highest height is 5010 m and the lowest is 10 m. It decreases gradually from the west to the east. The height of dune mainly distributed below 1500 m, followed by 1500–2000 m. Migratory sand dunes in Hobq Desert accounts for 51.8% and is mainly distributed in the west of the desert. The distribution area of fixation sand dunes in Hobq Desert is the least, accounting for 8.3%. The migratory dune pattern is trellis dune, semimigrated dune and semifixed dune patterns include honeycomb dune, parabolic duneand brush dune, and fixation dune pattern is grass dune. Annual wind speed was greatest in the southeast and decreased moving to the northwest. The dominant wind direction was W and SW from 2009 to 2018 in the Hobq Desert, the average wind speed of the prevailing winds mainly distributed at 4–8 m/s. The frequency of wind speed exceeding 10 m/s is very low, with a maximum value of 10% or below. There is a low energy wind environment in the Hobq Desert, with intermediate annual directional variability and obtuse or acute bimodal wind regime. The resultant drift direction (RDD)at Dongsheng station was relatively constant from 2009 to 2018, it was about 350°. RDD differed significantly at Baotou and Linhestations were 181 ± 169° and 231 ± 121°, respectively.The relationship between drift potential (DP) and the average and maximum wind speed was expressed as a power function. DP was strongly correlated with them. There is no significant correlated between the temporal changes in DPandprecipitation and temperature from 2009 to 2018 in the Hobq Desert. [ABSTRACT FROM AUTHOR]

In order to determine the key influencing factors, risk areas, and source pathways of heavy metals in the sediment of the Yellow River, 37 samples were collected in the surface sediment (0–5 cm) of the Inner Mongolia section of the Yellow River main stream for the determination of heavy metals copper (Cu), nickel (Ni), zinc (Zn), chromium (Cr), lead (Pb), and cadmium (Cd). Based on the geographical detector model (GDM) and ArcGIS 10.2 software, this paper selected 6 heavy metals and 15 influencing factors, including 8 natural factors and 7 anthropogenic factors, to detect key influencing factors, risk areas, and sources of heavy metals. The results showed that: (1) The average contents of heavy metals Cr and Cd in the sediments exceeded the average value in soil, the world average concentration in the shales, and the first-level standard of soil environmental quality in China, and they were the main risk metals; (2) Vegetation coverage (VC) was the largest influencing factor for the spatial distribution of heavy metals in the sediment, followed by per capita income (PI), and land use type (LUT) and road network density (RD) were smaller influencing factors. The interactions of the factors were enhanced; (3) The Wuhai section for a risk area was mainly polluted by Cd and Pb, which were caused by atmospheric deposition and industrial emission. The Baotou section for a risk area was mainly polluted by Cr, which mainly originated from river transportation and industrial discharge. The conclusions can provide a scientific basis for the environmental protection and management of the different areas in the Inner Mongolia section of the Yellow River.

The integration of rivers and basins highly implies the possible existence of certain relationships between hierarchical characteristics of river networks and primary basin factors. Here we investigated river networks in two large basins, the Yangtze River and the Yellow River, characterized with basic factors such as annual precipitation, slope, soil erodibility and vegetation. Hierarchical analysis demonstrated a fair self-similarity of river networks at the stream-order 1–5 in both rivers, described by the structural parameters including bifurcation ratio, side-branching ratio, drainage density, and length of headwater-river. Besides precipitation, basin slope was essential in shaping river networks in both basins, showing a significant positive correlation (R2=0.39–0.85) to bifurcation ratio, side-branching ratio, and drainage density. Given the same basin slope (5°–15°), the higher soil erodibility and sparse vegetation would promote greater side-branching ratio and drainage density in the Yellow River, which were estimated 11.97 % and 63.70 % larger, respectively than those in the Yangtze River. This study highlights the importance to formulate basin-specific strategies for water and soil conservation in terms of different structures of river networks. [ABSTRACT FROM AUTHOR]

Under the impact of climate change, the variation in the magnitude and frequency of extreme precipitation events has become a major issue worldwide. Based on the daily precipitation data at 9 meteorological stations and 111 precipitation stations in the Hekouzhen-Longmen region (HLR) in the middle reaches of the Yellow River Basin during 1966–2015, the spatial and temporal variations in and statistical probability characteristics of extreme precipitation were investigated. The probability distribution of extreme precipitation in the HLR was simulated with the annual maximum (AM) series and peak over threshold (POT) series by three extreme distributions, namely, generalized extreme value (GEV) distribution, generalized Pareto (GP) distribution, and gamma distribution. The parameters of the GEV, GP and gamma distributions were estimated by the L-moments method, and the best fit model was selected by the Kolmogorov-Smirnov (K-S) test. The results showed that high value area of extreme precipitation was located in the southeast part of the HLR, while the lower value area was mainly distributed in the northwestern part of the HLR and the upper reaches of the Wuding River Basin. A positive trend of annual maximum precipitation was detected at half of the stations, and the other half of the stations were found to show a negative trend from 1966 to 2015, while the changing trends of extreme precipitation at almost all of the stations were nonsignificant. From the results of the K-S test, the GEV distribution can better fit the AM series, and the GP distribution can better fit the POT series. The estimated extreme precipitation of the AM series is larger than that of the POT series with the same return period at most stations. [ABSTRACT FROM AUTHOR]

In order to further explore the relationship between water body eutrophication of some reaches of Yellow River and phosphorus species in sediments, and evaluate phosphorus release potential from sediments to overlying water, we investigated the distribution of P species and their release risk in the surface sediments from different reaches along Yellow River, as well as the influence of artificial dam on phosphorus cycle in Yellow River. The results show that the content of calcium phosphorus (PCa) is higher than the content of bioavailable phosphorus (BP) (BP = Pex + PFe; in the formula, Pex means exchangeable phosphorus and PFe means iron phosphorus) in the surface sediments from Yellow River. Among all the surface sediment samples from 21 stations, only Dayudu section (H15) has a ratio of W (BP)/W (PCa) higher than 0.5; the results show that the intensity of phosphorus release from H15 is high, and there is a potential risk of eutrophication in water, while the phosphorus release level of water sediment in other reaches of Yellow River is low. The content of BP and total phosphorus (∑P) in surface sediments along the Yellow River is in descending order: middle reaches of Yellow River > upper reaches of Yellow River > Yellow River downstream, while the content order of total phosphorus (TP) in the overlying water is as follows: Yellow river downstream > middle reaches of Yellow River > upper reaches of Yellow River (except the H7 station), indicating that extensive artificial corresponding damming in Yellow River basin makes the concentration of TP increasing significantly in overlying from upstream to downstream. The establishment of Haibowan water conservancy project in Yellow River makes the total particulate matter (TPM) concentration in the water to reduce to very low lever in Wuhai H7 section, and the phosphorus concentration in the overlying water reaches 0.136 mg L−1. [ABSTRACT FROM AUTHOR]

For many event-based, high-sediment yield rivers draining arid zones, where erosion activities in the watershed and fluvial erosion in the stream channel are nearly equally important in sediment transport, determination of fluvial sediment dynamics are of great importance in establishing reliable strategies to manage environmental changes in watershed scale. Wash load rating curve indicating watershed characteristic changes and Ackers and White's bed load function (wash load excluded) used for determining bed load transport dynamics are distinguished for the first time to recognize the true sediment transport mode in the lower Huangshui River, which is the largest tributary of the upper Yellow River, contributing a lot to the wash load of the Inner Mongolia desert reach of the Yellow River and causing complicated water-sediment response. Based on the continuous and detailed hydrological data monitored at the Minhe gauge station, our results indicated that the sediment transport regime has altered since the 1980s in response to the eco-environmental changes mainly due to urbanization, with suspended sediment concentration (SSC) decreased by 50% on average compared with the natural state (1950–1980). The combined use of wash load rating curve and theoretical bed load function derived an estimate of total sediment transport due to comprehensive ecological management since the 2000s to be 3.43 × 107 t for the lower Huangshui River, among which the total bed load is 1.40 × 107 t, and the wash load is 2.03 × 107 t. The transport ratio of wash load to total bed load is 1.45:1. [ABSTRACT FROM AUTHOR]

The lower Yellow River channel was maintained by artificial levees between 1580 and 1849. During this period, 280 levee breaches occurred. To estimate sediment storage on the floodplains outside the levees, a regression model with a decadal time step was developed to calculate the outflow ratio for the years when levee breaching occurred. Uncertainty analysis was used to identify the likely outflow ratio. Key variables of the model include annual water discharge, a proxy for levee conditions, and potential bankfull discharge of the channel before flood season. Uncertainty analysis reveals an outflow ratio of 0.35–0.56. We estimate that during this period, 18.8–30.1% of the total ~312 Gt of sediment load was deposited on the floodplains outside the levees. Human‐accelerated erosion in the Loess Plateau caused a 4‐fold increase in sediment delivery to the lower Yellow River, which could not be accommodated by channel morphodynamic changes. As a result, 21.2–27.5% of the total sediment load was deposited within the levees, creating a super‐elevated channel bed that facilitated an uncommonly high breach outflow ratio. Hence, the factor of a large super‐elevation relative to the mean main channel depth should be considered when designing diversions to restore floodplains. © 2018 John Wiley & Sons, Ltd. Around 24% of the sediment was deposited in the channel belt and floodplains within levees, 19–30% was trapped in the floodplains outside the levees, and the rest was delivered to the delta area. Human‐accelerated erosion in the Loess Plateau caused a super‐elevated channel bed on the lower river, which favors sediment trapping in the floodplains outside the levees. [ABSTRACT FROM AUTHOR]

The anastomosing river that is present within the First Great Bend of the Yellow River is different from other sand-bedded rivers of this type because it contains gravel-bedded materials. It is therefore important to determine whether, or not, the specific characteristics of this anastomosing river are similar to those seen in sand-bedded forms, including the characteristics of erosion and deposition, and the stability of channel and interchannel wetlands. Four Landsat images from 1990, 2001, 2013, and 2016 alongside two Google Earth (GE) images from 2011 and 2013 were utilized in this study in tandem with field sampling and observations to select a 12 km main channel length section of the Qihama reach anastomosing river. This section was then used to determine variations in channel planform and sedimentary characteristics over a 26 year period. The results of this study show that this gravel-bedded anastomosing river has exhibited a high degree of stability overall, and that there has been no obvious channel and wetland bank erosion and deposition. Data also show that over the 26 years of this study, anastomosing belt area increased by 2.43%, while the ratio of land to water area remained almost equal. The number of wetlands has also increased along this river section at a rate as high as 62.16% because of the fragmentation of some small interchannel examples, while the talweg has alternately migrated to either the left or right over long periods of time at a relatively stable rate. Indeed, as a result of the migration of this line, there has been significant turnover in the number of islands within the main channel while bank shift has occurred at a rate of about 5 m/yr. The numerous anastomosing channels within this river section remained very stable over the course of this study, characterized by a mean annual migration rate of just 1 m/yr, while the sediments in bank columnar sections are mainly composed of fine sands or silts with a relatively high clay content. The sediment grain-size distribution curve for this river section contains multiple peaks, distinct from the muddy sediments within bank columnar sections from sand-bedded anastomosing rivers. The dense vegetation within riparian and interchannel wetlands alongside this river reach has also protected anastomosing channels from erosion and maintained their stability, a key feature of this gravel-bedded system. [ABSTRACT FROM AUTHOR]

The source region of the Yellow River, located in the northeastern part of the Qinghai-Tibetan Plateau, is the typical environmentally fragile region of Chinese eco-environment. As the important water source supplying area of Yellow River, the source region is known as “plateau’s water tower”. There inhabit large quantities of rare wild animals. In this study, based on land ecological classification and field investigation, we used landsat images obtained in 2000 and 2015 to establish databases. From spatial distribution pattern variations and type transformation trend, the spatial changes and dynamic transfers of landscape ecotypes in the source region were analysed by using the analytical methods of landscape ecological spatial patterns. Results show that the unique natural conditions of the source region are more harsh and fragile. There have been phenomena of grasslands deterioration, desertification and wetlands shrinking, and water yield in the upper reaches of the Yellow River has been decreasing in recent years. In the source region, the serious eco-environmental problems have been caused by climate changes, rodent damages and human activities. [ABSTRACT FROM AUTHOR]

In this study, adsorption performance of polyvinyl alcohol (PVA) onto sediments of Yellow River was systematically investigated. Results showed that the sediments could effectively adsorb PVA so as to decrease its dissolved amount in the natural water. Kinetic experiments indicated that a rather rapid uptake of PVA occurred and the removal percentage could reach 60.2% by 24 h. Non-linear fitting method succeeded in discerning that both Toth and Koble-Corrigan models best fitted the experimental data, indicating the possible mono layer and physical adsorption of PVA on the sediments. Langmuir isotherm model also simulated the adsorption isotherm data better, and at 288 K, the maximum adsorption capacity of 356.56 mg/g for PVA uptake was obtained by Langmuir isotherm model. Both, the increase of temperature and solution pH values, would reduce the uptake of PVA. At the same time, the co-existing anions could inhibit the uptake of PVA to some extent. This research would be useful in the risk assessment and subsequent treatment and utilization of the Yellow River. It could also be a reference for other pollution adsorption performances onto the sediments in different rivers. [ABSTRACT FROM AUTHOR]

Tetraena mongolica Maxim (Zygophyllaceae) is an endangered species endemic to western Inner Mongolia and China, and is currently threatened by habitat loss and human over-exploitation. We explored the genetic background, its genetic diversity, population structure, and demographic history, based on 12 polymorphic nuclear microsatellite loci. Our results indicated high genetic diversity in extant populations, but no distinguishable gene cluster corresponding with a specific biogeography. Population demography analysis using a MSVAR indicated a strong, recent population decline approximately 5,455 years ago. These results suggest that the Yellow River and Zhuozi Mountain range may not prevent pollination between populations. Finally, we surmised that the population demography of T. mongolica was likely to have been affected by early mankind activities. [ABSTRACT FROM AUTHOR]

Abstract: The braiding intensity and dynamics in large braiding rivers are well known to depend on peak discharges, but the response in braiding and channel–floodplain transformations to changes in discharge regime are poorly known. This modelling study addresses the morphodynamic effects of increasing annual peak discharges in braiding rivers. The study site is a braiding reach of the Upper Yellow River. We estimated the effects on the larger‐scale channel pattern, and on the smaller‐scale bars, channel branches and floodplains. Furthermore, we determined the sensitivity of the channel pattern to model input parameters. The results showed that the dominant effect of a higher peak discharge is the development of chute channels on the floodplains, formed by connecting head‐cut channels and avulsive channels. Widening of the main channel by bank erosion was found to be less dominant. In addition, sedimentation on the bars and floodplains increased with increasing peak discharge. The model results also showed that the modelled channel pattern is especially sensitive to parametrization of the bed slope effect, whereas the effect of median grain size was found to be relatively small. Copyright © 2018 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Streamflow and sediment runoff are important indicators for the changes in hydrological processes. In the context of environmental changes, decreases in both streamflow and sediment (especially in the flood season) are often observed in most of the tributaries of the middle Yellow River in China’s Loess Plateau. Understanding the effect of human activities could be useful for the management of soil and water conservation (SWC) and new constructions. In this paper, changes in streamflow and sediment during the flood season (June−September) of the 1966−2017 period in a typical loess hill and gully landform basin were analyzed. Basin-wide rainfall of the flood season decreased nonsignificantly with an average rate of −0.6 mm/flood season for the whole study period by using the trend-free pre-whitening based Mann−Kendall trend test, while the decreasing rate was weakened on the time scale. A remarkable warming trend (1985−1999) and two decreasing trends (1966−1984 and 2000−2017) were observed, and the overall increasing trend could be found in air temperature series with a rate of 0.01 °C/flood season during the study period. Statistical models were developed to describe the rainfall-runoff and rainfall-sediment processes in the pre-impact period (when the hydrological series was stationary). Furthermore, the relative effects of climate variability and human activities on hydrological changes were quantified. Results proved the dominant role of human activities (versus climate variability) on the reductions of both streamflow and sediment load. The relative contribution of human activities to streamflow decrease was 84.6% during the post-impact period 1995−2017, while the contributions were 48.8% and 80.1% for two post-impact periods (1982−1996 and 1997−2017), respectively, to the reduction of sediment load. Besides, the effect of the exclusion of anomalous streamflow or sediment events on change-point detection was also analyzed. It indicated that the anomalous events affect the detection of change points and should be given full consideration in order to decide whether to remove them in the change-point detection. Otherwise, the full series with anomalous samples will completely affect the attribution results of hydrological changes. We also suggest that large-scale SWC measures with different construction quality and operational life could intercept and relieve most floods and high sediment concentration processes, but may amplify the peaks of streamflow and sediment when the interception capacities are exceeded under the condition of extreme rainstorm events.

Both interchannel wetlands and multi-channels are crucial geomorphologic units in an anastomosing river system. Planform characteristics and development of interchannel wetlands and multi-channels control the characteristics of anastomosing rivers. To understand the role that interchannel wetlands play in the development of anastomosing rivers, a study was conducted on the Maqu Reach of the Upper Yellow River (MRUYR), a gravel-bed anastomosing river characterized by highly developed interchannel wetlands and anabranches. Geomorphologic units in the studied reach were extracted from high resolution satellite imagery in Google Earth. The size distributions of interchannel wetlands and interchannel wetland clusters (IWCs), a special combination of interchannel wetlands and anabranches, were investigated. Geomorphologic parameters, including the ratio of interchannel wetland area to IWC area (P), shoreline density (D), and node density (D) were used to analyze planform characteristics of IWCs and the development of multi-channels in the studied reach. The results suggest that small or middle sized interchannel wetlands and large or mega sized IWCs are more common at the study site. The area of IWC (S) is highly correlated with other geomorphologic parameters. P increases with increasing S, and the upper limit is about 80%, which indicates that the development of interchannel wetlands and anabranches in the IWC is in the equilibrium stage. In contrast, D and D show a tendency to decrease with increasing S due to diverse evolution processes in IWCs with different sizes. There are three main reasons leading to the formation of IWCs: varying stream power due to the meandering principal channel; development of the river corridor due to the weakening of geologic structure control; and high stability of interchannel wetlands due to conservation by shoreline vegetation. [ABSTRACT FROM AUTHOR]

High-resolution multiproxy records, including clay minerals and Sr-Nd-Pb isotopes of the clay-sized silicate fraction of sediments from IODP Site U1429 in the northern Okinawa Trough, provide reliable evidence for distinct control mechanism on fine-grained sediments input from the Yellow River and the southern Japanese Islands to the northern Okinawa Trough since 34 ka BP. Provenance analysis indicates that the sediments were mainly derived from the Yellow River and the island of Kyushu. Since the last glacial, clay-sized sediments transported from the Yellow River to the study site were strongly influenced by sea-level fluctuation. During low sea-level stage (∼34-14 ka BP), the paleo-Yellow River mouth was positioned closer to the northern Okinawa Trough, favoring large fluvial discharge or even direct input of detrital sediments, which resulted about four times more flux of clay-sized sediments supply to the study area as during the relatively high sea-level stage (∼14-0 ka BP). The input of Kyushu-derived clay-sized sediments to the study site was mainly controlled by the Kuroshio Current and Tsushima Warm Current intensity, with increased input in phase with weakened Kuroshio Current/Tsushima Warm Current. Our study suggests that the Kuroshio Current was very likely flowed into the Okinawa Trough and thus influenced the fine-grained sediment transport in the area throughout the last glacial and deglacial. During ∼34-11 ka BP, the Kyushu clay-sized sediment input was mainly controlled by the Kuroshio Current. Since ∼11 ka BP, the occurrence of Tsushima Warm Current became important in influencing the Kyushu fine-grained sediment input to the northern Okinawa Trough. [ABSTRACT FROM AUTHOR]

Tan, C.; Huang, B.; Liu, F.; Yang, Q.; Jiang, C., and Zhang, S., 2016. Transformation of the three largest Chinese river deltas in response to the reduction of sediment discharges. The Yellow, Yangtze, and Pearl rivers deliver more than 1.2 × 1012 m3/a of freshwater and 13.6 × 108 t/a of sediment into the western Pacific Ocean, playing important roles in the morphological evolution of the ocean in this region. From the 1950s to the 2000s, the total sediment loads of the three rivers decreased by 81.2%; this change has been primarily caused by human activities, such as dam construction and water-soil conservation projects. The sediment loads in the Yellow, Yangtze, and Pearl rivers decreased by 89.9%, 62.1% and 57.1%, respectively, from the 1950s to the 2000s. In response to the sediment supply decrease, the sediment regimes of the river channels in the lower reaches of the three rivers generally transitioned from deposition to erosion since the 1990s. The erosion of the channel has modulated the characteristics of the suspended sediment delivered to the estuary; for example, the erosion of the lower river channel increased the sediment flux and caused relatively coarser suspended sediments to be delivered to the estuary. As a consequence of the changes in the river basins, the evolutions of the three river deltas have transformed in the 2000s. The subaqueous deltas of the Yellow and Yangtze rivers changed from deposition to erosion. However, the Pearl River delta generally prograded seaward, and a portion of its subaqueous delta ( e.g., the Modaomen River mouth) underwent erosion. In the coming decades, the sediment discharges into the seas from these three rivers are likely to decrease further because of intensifying human activities. Therefore, enhanced erosion in the three river deltas will continue when the river deltas remain unprotected. Our study demonstrates that human activities in the three river basins can influence the morphological changes of the estuaries, indicating that a river basin and its coastal zone are an integrated system. [ABSTRACT FROM AUTHOR]

Channel variations of the Inner Mongolian reach in the upper Yellow River are very complicated because of diversity of channel patterns, intense changes in water and sediment, and enhanced human activities in the last decades. It is important to examine the channel migration rates in this river reach. Based on channel planform changes at 236 digital channel cross-sections, the present study estimated the channel migration rates in terms of mid-channel line shift at the digital channel cross-sections during the periods 1975-1990, 1990-2000, 2000-2006, 2006-2010, and 2010-2011. The results show that the average channel migration rate for the whole river reach is 5.0, 7.9, −5.9, 8.6, and −1.0 m in the five different periods, respectively. In both directions to the right and to the left, the highest channel migration rate was always observed in the meandering channels, while the lowest channel migration rate was in the whole Inner Mongolian reach except the Sanhuhekou-Zhaojunfen (S-Z) sub-reach. The temporal variation of channel migration rate was mainly controlled by changing sediment concentration in river flow, while the spatial variation along the straight, braided, and meandering channel reaches was largely affected by material differences of channel banks as reflected by different channel patterns. With the highest average lateral migration rate to the left bank, the meandering channel reach is extremely vulnerable to lateral migration and needs to be protected with engineering practices, because a large population and wide farmland are located on its left floodplain. [ABSTRACT FROM AUTHOR]

The Inner Mongolia reaches of the Yellow River face problems of severe sedimentation caused by a variety of complex factors. The sedimentation process in those reaches has been characterized using the sediment balance method, and the key factors affecting the process have been analyzed using the correlation analysis method. The results show that during the period 1952-2012 the Bayangaole (Bayan Gol) to Toudaoguai reaches in Inner Mongolia have undergone successive processes of accumulative sedimentation, then relative balance, and then accumulative sedimentation once again. The total annual sedimentation is 12.0341×10 m, of which accumulations from July to October account for 95.1% and the reaches from Sanhuhekou to Toudaoguai account for 98.5%. The main factor affecting scouring and sedimentation of the Bayangaole to Sanhuhekou reaches is the combined water and sediment condition. The critical conditions for equilibrium are an incoming sediment coefficient < 0.007 kg·s·m and a flow discharge > 700 m·s. The main factor affecting scouring and sedimentation of the Sanhuhekou to Toudaoguai reaches is the incoming sediment from the tributaries on the south bank and the combined water and sediment condition of the main stream. The critical conditions of the main stream for maintaining equilibrium status are a flow discharge of the main stream exceeding 800 m·s and a comprehensive incoming sediment coefficient < 0.005 kg·s·m. The incoming sediment from the tributaries has little impact on the main stream when the annual sediment load is less than 0.1×10 t. The incoming sediment coefficient of the main stream and the incoming sediment from the tributaries both play vital roles in the riverbed evolution of the Inner Mongolia reaches, but the latter contributes the most. [ABSTRACT FROM AUTHOR]

Bohai Sea is one of the most intensively exploited region in the world and its environment has been severely impacted by the extensive human activities. The Yellow River is the most important river which connects with the Bohai Sea. Therefore, this study focused on analyzing heavy metals (HMs) in 21 surface sediment samples collected from the Yellow River, China. Sequential extraction procedure (SEP), proposed by the Community Bureau of Reference (BCR), was applied in the present study to determine the concentration and fractionation characteristics of these HMs. The aim of this study was to investigate the spatial distribution, fractionation, risk assessment, and sources of HMs, including copper (Cu), zinc (Zn), lead (Pb), chromium (Cr), iron (Fe), manganese (Mn), and nickel (Ni). The results obtained from this research will play a significant role in understanding the migration, transformation, and accumulation of HMs for future research in study area. Results of fractionation revealed that most of the HMs in the study area mainly existed in residual fraction; however, Mn mostly existed in exchangeable fraction. A high percentage of reducible fractions was found for Cu and Pb. The mean contamination factor (C) values indicated that Pb was the highest. It was >1 and showed moderate contamination, followed by Cr, Cu, Mn, Ni, and Zn, had <1 and indicated low contamination. Among studied HMs Pb had higher enrichment factor (EF) as compared to others. Significant positive correlations within all studied HMs and principal component analysis (PCA) results indicated their common sources, however, Pb showed the different contamination sources. The total contents of HMs in sediment were compared with the threshold effect level (TEL) and probable effect level (PEL) sediment quality guideline (TEL/PEL-based SQGs) values for trace metals in sediment, as well as literature reported data for comparative purposes, which indicated that the selected river in present study is not severe. [ABSTRACT FROM AUTHOR]

Distribution of five heavy metals (Cr, Pb, Cd, Cu, and Zn) and some physicochemical variables were studied from ten sites (S1-S10) in filtered water, suspended particles, and sediment samples from Gansu Province, Ningxia, and Inner Mongolia Autonomous Regions of the Yellow River in Northern China. The results showed that heavy metal concentrations in filtered water were relatively lower, while they were higher and approximated in suspended particles and sediment samples. Metal chemical fractions showed that high proportions of Cd were found in the exchangeable fractions, while others likely to be existed in lithology. Heavy metal pollution index (HPI) indicated that the quality of filtered water was relatively better, and the potential ecological risk index (PERI) revealed that only Cd has the higher ecological risk in suspended particles and sediment samples, which is accordance with the results obtained by the chemical fractions analysis; at the same time, the higher ecological risks existed in S3, S6, S9, and S10 in suspended particles and sediment samples due to the waste emission of a variety of industries. Results of cluster analysis (CA) indicated that contamination sources in the sediment samples were from both natural processes and anthropogenic activities. [ABSTRACT FROM AUTHOR]

The Yellow River is well known for high concentration of suspended particulate matter (SPM), which is one of the most important SPM sources in the Bohai Sea and Yellow Sea, China. The mechanisms of long-distance transport and deposition of the Yellow River sediment discharges are hot topics. Based on field observations in four different seasons of 2010-2011 and 15 numerical experiments, this work studied the seasonal sediment transportation and deposition in the Bohai and Yellow Seas. Results show that the horizontal distribution of suspended sediment concentration in the Bohai Sea and Yellow Sea is neither closely related to the Yellow River discharge in flood and dry seasons nor to the temperature and salinity distributions in winter and summer because most of the Yellow River-discharged sediments deposited near the river mouth. However, the winter northerly wind events, especially the winter storm events with high waves, are the major factors inducing the long-distance transport of the sediments from the Bohai Sea to the Yellow Sea. The net SPMs are transported to the Yellow Sea from the Bohai Sea in both winter and summer. The net SPM flux at the Bohai Strait is 14.0 Mt/year by the combined effects of tides, wind, and waves. The SPM is transported to the Shandong Peninsula in the Yellow Sea for the generation of the mud wedge off the peninsula. The northern part of the mud wedge is related to the southerly wind in summer, and the southeastern part resulted from the winter northerly wind, especially the strong wind. [ABSTRACT FROM AUTHOR]

Samples were collected monthly from January to December in 2010, and daily observations were made during the water-sediment regulation event in June-July 2010. Sequential extractions were applied to determine the forms of P in different particle-size fractions and to assess the potential bioavailability of particulate phosphorus (PP). The results indicated that exchangeable phosphorus, organic phosphorus, authigenic phosphorus, and refractory phosphorus increased with the decreasing of particulate size; conversely, detrital phosphorus decreased with the decreasing of particulate size. The content of bioavailable particulate phosphorus (BAPP) varied greatly in different sizes of particles. In general, the smaller the particle size, the higher the content of bioavailable phosphorus and its proportion in total phosphorous was found in these particles. Hydrological forcing controlled the variability in the major P phases found in the suspended sediments via changes in the sources and the particle grain-size distribution. The variation of particle sizes can be attributed also to different total suspended sediment (TSS) sources. Water-sediment regulation (WSR) mobilized only particulate matter from the riverbed, while during the rainstorm soil erosion and runoff were the main source. The BAPP fluxes associated with the 'truly suspended' fraction was approximately 200 times larger than the dissolved inorganic phosphorus (DIP) flux. Thus, the transfer of fine particles to the open sea is most probably accompanied by BAPP release to the DIP and can support greater primary and secondary production. [ABSTRACT FROM AUTHOR]

Polychlorinated dibenzodioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) are toxic environmental pollutants that are often found in sediments. The Yangtze and Yellow rivers in China are two of the largest rivers in Asia and are therefore important aquatic ecosystems; however, few studies have investigated the PCDD/F and PCB content in the sediments of these rivers. Accordingly, this study was conducted to generate baseline data for future environmental risk assessments. In the present study, 26 surface sediments from the middle reaches of the Yellow and Yangtze rivers were analyzed for PCDD/Fs and dioxin-like (dl) PCBs by high-resolution gas chromatography and high-resolution mass spectrometry. The ranges of PCDD/F, dl-PCB, and WHO-TEQ content in sediments from the Yellow River were 2.1-19.8, 1.11-9.9, and 0.08-0.57 pg/g (dry weight), respectively. The ranges of PCDD/F, dl-PCB, and WHO-TEQ content in sediments from the Yangtze River were 6.1-84.9, 1.8-24.1, and 0.13-0.29 pg/g (dry weight), respectively. Total organic carbon and dl-PCB contents in the Yellow River were significantly correlated (Spearman's correlation coefficient, r = 0.64, P < 0.05). It is well known that total organic carbon plays a role in the transport and redistribution of dl-PCB. Principal component analysis indicated that PCDD/Fs may arise from pentachlorophenol, sodium pentachlorophenate, and atmospheric deposition, while dl-PCBs likely originate from burning of coal and wood for domestic heating. The dioxin levels in the river sediments examined in this study were relatively low. These findings advance our knowledge regarding eco-toxicity and provide useful information regarding contamination sources. [ABSTRACT FROM AUTHOR]

Hechuan wetland is located in the mid-Yellow River and at the intersection of Shaanxi, Shanxi and Henan provinces in China. It is the largest hot spring lake wetland in the Yellow River basin and the birthplace of Guanju, a famous poem in the Book of Songs. Based on field investigations and questionnaires, we valued Hechuan Wetland ecosystem services, considering use values and non-use values. The annual use value of Hechuan Wetland ecosystem services is 79.236 billion CNY. The contingent valuation method was applied to value the annual non-use value, which is 6.27 billion CNY. We examined how the historical and cultural value of the Book of Songs affected respondents' willingness to pay by establishing a control group. Results suggest that historical and cultural value does have a strong influence on willingness to pay. [ABSTRACT FROM AUTHOR]

The impact of reservoirs on downstream river channel change has been a scientific issue in fluvial geomorphology during the last few decades. However, it is still a difficult issue as to how to express quantitatively the channel adjustment in the Inner Mongolian reach of the Yellow River induced by the joint operation of upstream reservoirs. Based on the shape parameters of channel cross-sections at four gauging stations in this river reach over a flooding season in two periods, 1978-1982 and 2008-2012, the present work investigated the channel changes in terms of shape parameter change rate under the same controlling water level in each flooding season at the channel cross-sections. Results showed that most of the change rates of the parameters evidently increased over a flooding season in both periods. However, the change rate of each parameter at the cross-sections decreased evidently in the latter period, compared with the former period. At the same time, the distribution pattern of the change rate of the shape parameters along the cross-sections thus changed from a convex curve in the former period to an S-shaped curve in the latter period. The obvious decrease of the change rates is related to the joint operation of the Liujiaxia and Longyangxia reservoirs. The reservoirs stored a large volume of water and decreased the peak discharge and maximum velocity in the flooding season; as a result, the erosion ability of the flood decreased accordingly. With the joint operation of the large reservoirs, the Inner Mongolian channel shrunk markedly. Therefore, the channel will present the possibility of an extreme flood in the future. Consequently, it is reasonable to adjust the function of the reservoirs in future. The total water and sediment discharges and the peak discharge in flooding seasons should be effectively controlled. Continuous shrinkage of the channel can thus be avoided and it can be ready for a potential extreme flood. [ABSTRACT FROM AUTHOR]

The Yellow River is an important source of sediment flux to oceans in the world, and approximately 90% of the sediment originates from the middle Yellow River, an area with known high rates of soil erosion and sediment delivery. Trends and interannual variations in sediment discharge have considerable implications for reservoir operation and river management of the lower Yellow River. The annual sediment discharge of four main stream stations and ten tributary stations was used to show the spatiotemporal variation in sediment yield and to quantify the relative contribution of precipitation change and human activities, especially the influence of vegetation restoration with implementation of the Grain for Green Project (GGP) in 1999. The Mann-Kendall and Pettitt tests were used to detect the abrupt change in sediment discharge since the 1950s. The annual sediment yield of the middle Yellow River has shown a significant downward trend, decreasing by an order of magnitude in the last decade (2000-2010) compared with the 1950s. Annual sediment yield was reduced by 95.5% from 3,887.0 t ⋅ km-2 ⋅ year-1 in the 1950s to 174.7 t ⋅ km-2 ⋅ year-1 in the 2000s. The eastern part of the middle Yellow River basin showed the most significant decrease, with sediment yield decreasing up to 90% in the 2000s compared with the 1950s. Annual precipitation decreased by 7.3% in the periods 1980-2010 and 1959-1979. Human activities and precipitation explain 83.6 and 16.4% of the total reduction in sediment yield, respectively, using the double mass curve method. Annual sediment discharge decreased by 597 x 106 t ⋅ year-1--from 660 x 106 in 1980-1999 to 63 x 106 in 2000-2010. Sediment deposition along the Longmen- Huayuankou section amounted to 120 x 106 t ⋅ year-1 during 1980-1999 and 229 x 106 t ⋅ year-1 during 2000-2010 based on mass balance. The additional 109 x 106 t ⋅ year-1 of sediment was trapped following completion of the Xiaolangdi Reservoir in the Longmen- Huayuankou section. This explains 18.3% of the sediment reduction in the 2000s. Soil conservation practices have further reduced sediment discharge by 253 x 106 t ⋅ year-1, which explains about 42.4% of the decrease (597 x 106) during 2000-2010. A reduction of approximately 235 x 106 t ⋅ year-1 occurred because of vegetation restoration driven by the Grain for Green Project, which accounted for 39.4% of the total reduction (597 x 106 t ⋅ year-1) in the last decade compared to 1980-1999. [ABSTRACT FROM AUTHOR]

The impact of the El Niño-Southern Oscillation (ENSO) phenomenon within the Huangfuchuan watershed, one of the major first-order sub-basins in the middle region of the Yellow River, has not clearly been established. Consequently, the co-varying relationships between rainfall and El Niño/La Niña spanning the period 1954 to 2010 are investigated. Trends and step changes in annual rainfall are investigated with the Mann-Kendall and the distribution free cumulative sum (CUSUM) tests. Wavelet transforms are employed to perform spectral analysis of temporal variations in rainfall rates within the watershed. Cross wavelet and wavelet coherence transforms are used to study localized co-varying relationships between rainfall and ENSO index. Results from statistical tests indicate that rainfall in the Huangfuchuan watershed is declining, although not significantly. In addition, wavelet coherency and cross wavelet analysis, and comparison of the extracted dominant annual rainfall and 2-7 year ENSO signals demonstrate that ENSO events impact Huangfuchuan rainfall with El Niño corresponding to rainfall decline and La Niña to rainfall increment with a semiannual to annual lag. [ABSTRACT FROM AUTHOR]

The concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) in water, suspended particulate matters (SPMs), and sediments in the Lanzhou reach of the Yellow River were investigated in this study. The total PAH concentrations ranged from 548 to 2598 ng/L in water, 1502 to 11,562 ng/g in SPMs, and 181 to 1583 ng/g in sediments. The compositions of PAHs showed that 2- to 3-ring PAHs were abundant in water, 2- to 4-ring PAHs were predominant in SPMs, and 2- to 5-ring PAHs were abundant in sediments. The spatial distribution of PAHs was site-specific and PAHs varied at different sampling locations. The diagnostic ratio analysis indicated that the PAHs mainly had a pyrolytic source. The ecological risk assessment showed that the ecosystem risk of PAHs was low in the Lanzhou reach of the Yellow River. [ABSTRACT FROM AUTHOR]