Analyses of Runoff and Sediment Transport and their Drivers in a Rare Earth Mine Drainage Basin of the Yangtze River, China

A comprehensive analysis of the effects of major climate conditions such as El Nino Southern Oscillation (ENSO) and precipitation on changes in runoff and sediment transport in a basin may provide a scientific basis and technical support for regional water resource management and protection of the aquatic ecology. Taking the Taojiang River as an example, a large set of hydrogeographic data on runoff and sediment transport measured on a monthly basis from 1957 to 2015 was analyzed to study the impacts of various correlation factors on runoff and sediment transport in the river, which is located in the middle and lower reaches of the Yangtze River. Besides the conventional Mann–Kendall (M-K) method, cross-wavelet and wavelet coherence analysis methods were also applied in the data analysis. The results showed that: (1) From the M-K mutation tests conducted for the runoff volume and the sediment transport rate from 1957 to 2015, there were no significant changes in runoff. However, a mutation occurred in the sediment transport rate in 2005 and the average annual decrease reached 88.2237 million tons. (2) Precipitation was a dominant factor that controlled the changes in runoff volume and sediment transport rate. It directly influenced the changes in runoff volume, which subsequently caused the changes in sediment transport rate in the study area. Since the year 2005, sediment transport rates have been heavily influenced by the construction of large-scale hydro-power stations (Julongtan), causing a significant rate decline. A comparison between the sediment transport volume during 2005 to 2015 and that during 1980 to 2004 revealed that the annual sediment transport decrease reached 84.4079 million tons, accounting for 95.7% of the total decrease in sediment transport volume. (3) The significant resonance cycle between the sea surface temperature (SST) and the precipitation, runoff volume and sediment transport mainly occurred with a cyclic period between 1.33 and 5.33 years. During an ENSO event, the precipitation, runoff, and sediment transport rates all decreased at the beginning, then increased and reached their maximums, followed by a decline at the end

Etude du transport de matière et hydraulique d'une rivière graveleuse de haute montagne, la rivière Ürümqi (Tianshan chinois)

Au cours des trois dernières décennies, les questions liées au transport des sédiments et la structure lit des rivières ont reçu une attention considérable. Les lois de l'écoulement et du mouvement des sédiments dans une rivière un lit de gravier sont un objectif important de recherche car ils permettent de caractériser la dynamique des flux de matière et l'évolution du lit d'une rivière. Un suivi in situ sur la rivière Urumqi (rivière à lit de gravier du nord-ouest de la Chine) a été réalisé de l'année 2004 à 2006. les données acquises nous permettent la réalisation d'important progrès dans notre connaissance de la structure du lit et la dynamique précise de la charge de fond. Nous montrons que le protocole d'échantillonnage est d'une importance cruciale lorsqu'il s'agit de transport de sédiments en général et de charge de fond en particulier. Les données de terrain de grande envergure a été recueillies sur une gamme relativement étendue de débit,charriage et des conditions de pente du chenal. Ces données ont fourni l'occasion d'aller au delà des limites imposées par les corrélations classiques contrainte de cisaillement versus charge de fond, et nous a permis d'examiner en détail le comportement local du flux de gravier. La variation à court terme des taux de transport a été en outre étudiée. Une équation asymptotique "simple" de charriage est proposée, qui simplifie considérablement l'analyse de la charge de fond et ce malgré une structure de lit et une distribution granulométrique complePARIS-BIUSJ-Sci.Terre recherche (751052114) / SudocSudocFranceChinaFRC

Current Status and Health Risk Assessment of Heavy Metals Contamination in Tea across China

Tea is a non-alcoholic beverage popular among Chinese people. However, due to the application of chemical and organic fertilizers in the tea planting process, the environment pollutionaround the tea plantation, and the instruments used in the processing, heavy metal elements will accumulate in the tea, which brings health risks for tea consumers. This study summarized heavy metal concentrations from 227 published papers and investigated the current contamination status of tea and tea plantation soils, and, finally, the risk of heavy metal exposure to tea consumers in China is assessed, in terms of both non-carcinogenic and carcinogenic risk. The average contamination of six heavy metals in tea—arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), and lead (Pb)—were 0.21, 0.14, 1.17, 14.6, 0.04, and 1.09 mg/kg, respectively. The areas with high concentrations of heavy metals in tea were concentrated primarily in southwest China, some areas in eastern China, and Shaanxi Province in northwest China. The non-carcinogenic risks of heavy metals in tea are all within safe limits. The national average HI value was 0.04, with the highest HI value of 0.18 in Tibet, which has the largest tea consumption in China. However, the carcinogenic risks of Cd in Shaanxi Province, Anhui Province, and southwest China exceed the acceptable range, and due attention should be given to these areas

Probabilistic Analysis of Extreme Discharges and Precipitations with a Nonparametric Copula Model

Urumqi River is an important river in the Xinjiang autonomous region, China, where floods or droughts are the major concerns of the local communities. This river's discharge is mainly influenced by the natural factors such as precipitation and climates, rather than human activities. This paper quantifies the interdependent structure between Urumqi River's discharge and precipitation using a nonparametric Copula method. It then analyzes the relationship between the extreme discharges of this river and extreme precipitation of the region. Comparison between simulation result and real data is conducted to verify the rationality of the model. Furthermore, the conditional probabilities of maximum and minimum discharge at different precipitation levels are also investigated using the Copula distribution functions. The results show a strong relationship between large discharge and heavy precipitation in this region. The upper dependence coefficient is nearly 0.6 and the probability of large discharge reaches 0.64 when the rainfall is greater than 159.56 mm. The relationship between small discharge and rainfall is insignificant. The lower dependence coefficient is zero, suggesting that the base flow and snowmelt from Tianshan likely contribute to Urumqi River's discharge during the dry season.National Natural Science Foundation of China [41471001, 41402210, 41272245, 11601244]; Scientific Research Foundation for Qingjiang Scholars of Jiangxi University of Science and Technology [JXUSTQJBJ2017002]; innovation team training plan of the Tianjin Education Committee [TD12-5037]; US National Science Foundation-Division of Earth Sciences [1014594]; Outstanding Oversea Professorship award through Jilin University from Department of Education, China; Global Expert award through Tianjin Normal University from the Thousand Talents Plan of Tianjin CityOpen access journal.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Measuring bedload in gravel-bed mountain rivers: averaging methods and sampling strategies Measuring bedload in gravel-bed mountain rivers: averaging methods and sampling strategies

International audienceA dataset of more than 1,000 individual bedload samples coupled with hydraulic flow variables (water depth and velocity) was collected on two high mountain rivers the torrent de Saint Pierre, a proglacial gravel-bed river in the French Alps, in July 2002 and the Urumqi River, in the Chinese Tianshan mountains during summer 2005 and 2006. Analysis of the dataset leads to question the usual section averaged sampling procedure of bedload using Helley-Smith type bedload sampler. It is shown that this procedure is inadequate to catch the full range of flow conditions. Comparison between moving averages on individual datasets and section averages furthermore show that this technique can lead to significantly different rating curves with predictions differing by more than an order of magnitude. Single point sampling is shown to be much more adequate than multiple point sampling and section averaging provided the dataset is sufficiently large

Dissolution in a porous rock: effect on the concentration–discharge relationships

International audienceVarious empirical or physically-based theory have been proposed to understand how the solute concentration of a stream varies with the discharge. We focus here on the influence of the dynamics of the groundwater flow on the chemical erosion rate. To do so, we couple a one-dimensional aquifer model to a first order dissolution equation. If the aquifer extends far below the stream level, the theoretical discharge–concentration equation corresponds to the empirical " working model " proposed by Johnson in 1969, thus providing a physical interpretation of its parameters. Conversely, if the aquifer lays mainly above the stream level, a significantly different relationship is found. These theoretical findings are then compared to two field-data sets. From this comparison, we conclude that the dynamics of the groundwater flow could play a significant role in moderating the impact of dilution on the stream concentration at large discharges

Dissolution in a porous rock: effect on the concentration-discharge relationships

Abstract Various empirical or physically-based theory have been proposed to understand how the solute concentration of a stream varies with the discharge. We focus here on the influence of the dynamics of the groundwater flow on the chemical erosion rate. To do so, we couple a onedimensional aquifer model to a first order dissolution equation. If the aquifer extends far below the stream level, the theoretical discharge-concentration equation corresponds to the empirical "working model" proposed by Johnson in 1969, thus providing a physical interpretation of its parameters. Conversely, if the aquifer lays mainly above the stream level, a significantly different relationship is found. These theoretical findings are then compared to two field-data sets. From this comparison, we conclude that the dynamics of the groundwater flow could play a significant role in moderating the impact of dilution on the stream concentration at large discharges

Erosion rates deduced from seasonal mass balance along the upper Urumqi River in Tianshan

International audienceWe report measurements performed during two complete flow seasons on the Urumqi River, a proglacial mountain stream in the northeastern flank of the Tianshan, an active mountain range in Central Asia. This survey of flow dynamics and sediment transport (dissolved, suspended and bed loads), together with a 25-year record of daily discharge , enables the assessment of secular denudation rates on this high mountain catchment of Central Asia. Our results show that chemical weathering accounts for more than one-third of the total denudation rate. Sediment transported as bed load cannot be neglected in the balance, given that sand and gravel transport accounts for one third of the solid load of the river. Overall, the mean denudation rates are low, averaging 46 t × km −2 × yr −1 (17–18 m Myr −1). We furthermore analyse the hydrologic record to show that the long-term sediment budget is not dominated by extreme and rare events but by the total amount of rainfall or annual runoff. The rates we obtain are in agreement with rates obtained from the mass balance reconstruction of the Plio-Quaternary gravely deposits of the foreland but signicantly lower than the rates recently obtained from cosmogenic dating of the Kuitun River sands, west of the Urumqi River. We show that the resolution of this incompatibility may have an important consquence for our understanding of the interplay between erosion and tectonics in the semi-humid ranges of Central Asia

Reconstruction of the sediment transport conditions in the Urumqi alluvial fan (northeastern Tian Shan, China)

International audienceAlluvial fans must contain information about the physical parameters of palaeo-rivers that built them. In particular, their grain-size evolution is partly related to water discharge and granulometry of the sediment supply. However, the temporal framework of deposits could also influence this grain size evolution. In order to discriminate the respective influence of the short-and long-term sedimentation dynamics on the grain-size organization of alluvial fans, we used a coupled experimental and field 99 approach. The experiments show that aggradation is a local and short-term process, whereas progradation is a more long-term and regional one. Moreover, progradation is clearly related to time through a power law, which indicates a progradation rate lowering. Accordingly, the progradation rate seems to be a good proxy to reconstruct the overall evolution of fans. The field measurements performed on the Quaternary deposits of the Uumqi River shows that it is possible to observe a progradation rate lowering associated with a natural fan growth, and to document and quantify this lowering on a single vertical section using a granulometric approach. This example shows that granulometric studies could be a good manner to characterize the long-term and regional fan dynamics and, we hope soon, the associated transport conditions