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1.
《国际泥沙研究》2020,35(4):365-376
The Yom River is one of the four major sediment sources to the Chao Phraya River in Thailand. Human activities and changes in climate over the past six decades may have affected the discharge and sediment load to some extent. In the current study, the river discharge and sediment characteristics in the mainstream of the Yom River were investigated using the field observation data from 2011 to 2013 and the historical river flow and sediment data from 1954 to 2014 at six hydrological stations operated by the Royal Irrigation Department of Thailand (RID). The non-parametric Mann-Kendall test and double mass curve were used to analyze the sediment dynamics and temporal changes in the discharge of the Yom River. The results revealed that the sediment was mainly transported in suspension, and the bed-to-suspended sediment loads ratio varied between 0 and 0.05. The daily suspended sediment load (SSL) in the upper and middle basins had a strong correlation with the daily discharge and could be represented by power equations with coefficients of determination higher than 0.8. The daily suspended sediment load in the lower basin did not directly depend on the corresponding discharge because of the reduction in river slope and water diversion by irrigation projects. It also appeared that the river discharges and sediment loads were mainly influenced by climate variation (floods and droughts). Moreover, the average sediment transport of the upper, middle, and lower reaches were 0.57, 0.71, and 0.35 million t/y, respectively. The sediment load in the lower basin decreased more than 50% as a result of changes in the river gradient (from mountainous to floodplain areas). The results from sediment analysis also indicated that the construction of the Mae Yom Barrage, the longest diversion dam in Thailand, and land-use changes did not significantly affect the sediment load along the Yom River.  相似文献   

2.
Despite a growing interest in the sediment dynamics of dryland rivers, most research has been based on ephemeral streams in endogenic hydrological systems (runoff and sediment transport determined by local precipitation). Less attention, however, has been paid to allogenic and perennial dryland rivers. Here, we report a case study on the suspended sediment dynamics of the Tarim River, an allogenic and perennial river flowing in a very arid environment in China, based on mean daily discharge and mean daily suspended sediment concentration (SSC) over the last 5 decades (1960–2011). Results reveal that discharge and SSCs are predominantly low and have distributions with large positive skewness. The SSC–discharge relationships can be fairly well generalized by power functions, with quite large scatter at extreme (low and high) flow conditions. Marked temporal and spatial variations were observed in the effective discharge for sediment transport. The frequency of the effective discharge ranged from 0.5% to 2% (or an average flow duration of 2–7 days/year), implying that moderate to high flows play an important role in sediment transport. The sediment rating curves show strong hysteresis effects, with 3 types of hysteresis loops observed, clockwise (the most predominant), anticlockwise, and figure of eight. The high potential for bank collapse near the peak and falling limb of the flood hydrograph is the major cause of anticlockwise and figure‐of‐eight hysteresis loops.  相似文献   

3.
长时间序列水沙数据分析有助于科学评价流域尺度水土保持减流减沙效应,为科学开展区域水土保持成效评估提供实现路径.本文选取南方红壤区水土保持工程最为集中、持续时间最长的典型流域——平江流域,基于1975-2014年的逐日降水量、流量、含沙量数据,综合应用预置白M-K检验法、Theil-Sen趋势度估计法、Pettitt检验法与累积量斜率变化率比较法,开展河流水沙变化特征及归因分析,揭示长期水土流失治理对河流水沙的影响.结果表明:(1)1975-2014年平江年输沙量、汛期输沙量和非汛期输沙量均存在显著减少趋势,年均减少率分别为2.38×104、1.75×104和0.44×104t/a,汛期输沙量在流域开始实施系统水土流失治理时即发生突变,而年输沙量和非汛期输沙量在系列国家水土保持重点工程实施一段时间后方开始突变;(2)流域长期水土保持显著减少平江输沙,但对径流无显著影响,重点治理期、治理后期以水土保持为主的生态保护工程对输沙量减少的贡献均在94.0%以上,且生态保护工程对汛期输沙量减少的贡献较非汛期的更为突出;(3)以水土保持为主的长期生态保护工程导致平江全年、汛期、非汛期输沙量分别减少59.3%、60.7%和55.7%;(4)在剔除大型水利工程(尤其是大中型水库)建设影响后,南方红壤区可以基于长时间序列水沙数据分析科学评价流域尺度水土保持减流减沙效应.研究结果可以为南方红壤区流域尺度水土保持减流减沙效应评价提供参考,并有望为区域系列国家生态保护与建设工程的布局和管理提供科学依据.  相似文献   

4.
《水文科学杂志》2013,58(6):1270-1285
Abstract

The transport of sediment load in rivers is important with respect to pollution, channel navigability, reservoir filling, longevity of hydroelectric equipment, fish habitat, river aesthetics and scientific interest. However, conventional sediment rating curves cannot estimate sediment load accurately. An adaptive neuro-fuzzy technique is investigated for its ability to improve the accuracy of the streamflow—suspended sediment rating curve for daily suspended sediment estimation. The daily streamflow and suspended sediment data for four stations in the Black Sea region of Turkey are used as case studies. A comparison is made between the estimates provided by the neuro-fuzzy model and those of the following models: radial basis neural network (RBNN), feed-forward neural network (FFNN), generalized regression neural network (GRNN), multi-linear regression (MLR) and sediment rating curve (SRC). Comparison of results reveals that the neuro-fuzzy model, in general, gives better estimates than the other techniques. Among the neural network techniques, the RBNN is found to perform better than the FFNN and GRNN.  相似文献   

5.
Riverine sediments have played an important role in the morphological evolution of river channels and river deltas. However, the sediment regime in the many world's rivers has been altered in the context of global changes. In this study, temporal changes in the sediment regime of the Pearl River were examined at different time scales, that is, annual, seasonal, and monthly time scales, using the Mann–Kendall test. The results revealed that precipitation variability was responsible for monthly and seasonal distribution patterns of the sediment regime and the long‐term changes in the water discharge; however, dam operation has smoothed the seasonal distribution of water discharge and resulted in decreasing trends in the annual, wet‐season, and dry‐season sediment load series since the 1950s. Due to the different regulation magnitudes of dam operation, differences were observed in sediment regime changes among the three tributaries. In addition, human activities have altered the hysteresis of seasonal rating curves and affected hysteresis differences between increasing and decreasing water discharge stages. Sediment supply is an important factor controlling river channel dynamics, affecting channel morphology. From the 1950s to the 1980s, siltation was dominant in river channels across the West River and North River deltas in response to the sediment increases; however, scouring occurred in the East River deltas due to sediment reduction. Significant erosion occurred in river channels in the 1990s, which was mostly due to downcutting of the river bed caused by sand excavations and partly because of the reduced sediment load from upstream. Although sand excavations have been banned and controlled by authority agencies since 2000, the erosion of cross sections was still observed in the 2000s because of reduced sediment caused by dam construction. Our study examines the different effects of human activities on the sediment regime and downstream channel morphology, which is of substantial scientific importance for river management.  相似文献   

6.
Accuracy and precision of methods for estimating river loads   总被引：1，自引：0，他引：1  
River loads often have to be estimated from continuous discharge data but relatively infrequent sampling of sediment, solute, or pollutant concentrations. Two standard ways of doing this are to multiply mean concentration by mean discharge, and to use a rating curve to predict unmeasured concentrations. Both methods are known from previous empirical studies to underestimate true load. Statistical considerations explain these biases and yield correction factors which can be used to obtain unbiased estimates of load. Simulation experiments with normally-distributed scatter about log-linear trends, and sampling experiments using a natural data set, show that the corrected rating curve method has lower sampling variability than other unbiased methods based on average instantaneous load and is thus the recommended procedure when the rating plot is of the assumed form. The precision of all methods increases with sample size and decreases with increasing rating-curve slope and scatter.  相似文献   

7.
More frequent extreme flood events are likely to occur in many areas in the twenty‐first century due to climate change. The impacts of these changes on sediment transport are examined at the event scale using a 1D morphodynamic model (SEDROUT4‐M) for three tributaries of the Saint‐Lawrence River (Québec, Canada) using daily discharge series generated with a hydrological model (HSAMI) from three global climate models (GCMs). For all tributaries, larger flood events occur in all future scenarios, leading to increases in bed‐material transport rates, number of transport events and number of days in the year where sediment transport occurs. The effective and half‐load discharges increase under all GCM simulations. Differences in flood timing within the tributaries, with a shift of peak annual discharge from the spring towards the winter, compared to the hydrograph of the Saint‐Lawrence River, generate higher sediment transport rates because of increased water surface slope and stream power. Previous research had shown that channel erosion is expected under all GCMs' discharge scenarios. This study shows that, despite lower bed elevations, flood risk is likely to increase as a result of higher flood magnitude, even with falling base level in the Saint‐Lawrence River. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

8.
In this paper, the changes in sediment transport over 51 years from 1955 to 2006 in the Kuye River in the Loess Plateau in China are assessed. Key factors affecting sediment yield and sediment transport, such as precipitation depth, discharge, and human activities are studied. To investigate the changes in sediment yield in this watershed, a trend analysis on sediment concentration, precipitation depth, and discharge is conducted. Precipitation depths at 2 Climate Stations （CSs）, as well as discharge and sediment transport at 3 Gauging Stations （GSs） are used to assess the features of sediment transport in the Kuye River. The rtmoff modulus （defined as the annual average discharge per unit area, L/（s·km^2）） and the sediment transport modulus （defined as the annual suspended sediment transport per unit area, t/（yr km^2）） are introduced in this study to assess the changes in runoff and sediment yield for this watershed. The results show that the highest average monthly discharge during the study period in the Kuye River is 66.23 m^3/s in August with an average monthly sediment concentration of 88.9 kg/m^3. However, the highest average monthly sediment concentration during the study period in the Kuye River is 125.34 kg/m^3 and occurs in July, which has an average discharge of 42.6 m^3/s that is much less than the average monthly discharge in August. It is found that both the runoff modulus and sediment transport modulus at Wenjiachuan GS on the Kuye River has a clear downward trend. During the summer season from July to August, the sediment transport modulus at Wenjiachuan GS is much higher than those at Toudaoguai and Longmen GSs on the Yellow River. The easily erodible loess in the Kuye River watershed and the sparse vegetation are responsible for the extremely high sediment yield from the Kuye River watershed. The analyses of the grain size distribution of suspended load in the Kuye River are presented. The average monthly median grain size of suspended load in the Kuye River is largest in February and then decreases until June. In July, the average monthly median grain size of suspended load approaches another peak and decreases until September. Then, the median grain size of suspended load starts to increase until February of the following year. However, the average monthly median grain size of suspended load in the Yellow River at Toudaoguai and Longmen GSs is the smallest between early summer and late fall The median grain size in the Yellow River starts to increase in November and approaches the largest size in January.  相似文献   

9.
Abstract The suspended sediment load in the middle Yellow River basin (YRB) cannot be well predicted by capacity‐based transport formulas because a large fraction of suspended sediment load is composed of wash load. This study evaluated the spatial variations of sediment rating curves (SRCs) in the middle YRB. Both power and linear SRCs were used to fit daily flow and suspended sediment concentration (SSC) historical data at 49 gauging stations throughout the middle YRB. The spatial variation in regression coefficients was investigated, and the relationship between regression coefficients and the physical characteristics of watersheds was discussed. The results indicate that SRC regression coefficients vary with drainage area and basin slope, but their responses to these parameters are remarkably different in watersheds with different underlying surfaces, which indicates the significance of sediment availability, erodibility, and grain size distribution. For power SRCs representing sediment transport in unsaturated flows, the regression coefficients are more closely correlated with the drainage area in loess regions and with the basin slope in rock mountain regions. For linear SRCs representing sediment transport in saturated flows, saturated SSCs vary with coarse (particle size > 0.05 mm) and fine (particle size < 0.01 mm) fractions in suspended sediment. The maximum saturated SSC among the different gauging stations is associated with the optimal grain size composition of suspended sediment, which has been proposed for loess regions in previous studies. This study provides theoretical support for estimating the regression parameters for sediment transport modelling, especially in ungauged basins.  相似文献   

10.
Abstract

Analyses of data from reservoir surveys and sediment rating curves are compared to predict sediment yield in three large reservoir watershed areas in Turkey. Sediment yield data were derived from reservoir sedimentation rates and suspended sediment measurements at gauging stations. The survey data were analysed to provide the volume estimates of sediment, the time-averaged sediment deposition rates, the long-term average annual loss rates in the reservoir storage capacity, and the long-term sediment yield of the corresponding watershed areas. Four regression methods, including linear and nonlinear cases, were applied to rating curves obtained from gauging stations. Application of the efficiency test to a power function form of a rating curve with nonlinear regression yielded the highest efficiency values. Based on the analysis of the sediment rating curves, sediment load fluxes were calculated by using average daily discharge data at each gauging station. Comparison of these two sediment yield values for each reservoir showed that the sediment yields from the suspended sediment measurements, SYGS, are 0.99 to 3.54 times less than those obtained from the reservoir surveys, SYRS. The results from the reservoir surveys indicate that all three reservoirs investigated have lost significant storage capacity due to high sedimentation rates.  相似文献   

11.
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12.
The behaviour of suspended sediment in rivers is often a function of energy conditions, i.e. sediment is stored at low flow and transported under high discharge conditions. The timing of maximum sediment transport can, however, also be related to mixing and routing of water and sediment from different sources. In this study suspended sediment transport was studied in the River Rhine between Kaub and the German–Dutch border. As concentrations decrease over a runoff season and as the relationship between water discharge and suspended sediment concentrations during most floods is characterized by clockwise hysteresis, it is concluded that sediment depletion occurs during a hydrological year and during individual floods. However, analyses of the sediment contribution from the River Mosel indicate that clockwise hysteresis may result from sediment depletion as well as from early sediment supply from a tributary. Thus, although the suspended sediment behaviour in the downstream part of the River Rhine is partly a transport phenomenon related to energy conditions, mixing and routing of water from different sources also plays an important role. Suspended sediment transport during floods was modelled using a ‘supply‐based’ model. Addition of a sediment supply term to the sediment rating curve leads to a model that produces better estimates of instantaneous suspended sediment concentrations during high discharge events. A major constriction of the model is that it cannot be used to predict suspended sediment concentrations as long as the amount of sediment in storage and the timing of sediment supply are unknown. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

13.
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14.
River discharge values, estimated using a rating curve, are subject to both random and epistemic errors. We present a new likelihood function, the ‘Voting Point’ likelihood that accounts for both error types and enables generation of multiple possible multisegment power‐law rating curve samples that aim to represent the total uncertainty. The rating curve samples can be used for subsequent discharge analysis that needs total uncertainty estimation, e.g. regionalisation studies or calculation of hydrological signatures. We demonstrate the method using four catchments with diverse rating curve error characteristics, where epistemic uncertainty sources include weed growth, scour and redeposition of the bed gravels in a braided river, and unconfined high flows. The results show that typically, the posterior rating curve distributions include all of the gauging points and succeed in representing the spread of discharge values caused by epistemic rating errors. We aim to provide a useful method for hydrology practitioners to assess rating curve, and hence discharge, uncertainty that is easily applicable to a wide range of catchments and does not require prior specification of the particular types and causes of epistemic error at the gauged location. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

15.
This paper considers the influence of volcanic eruptions on the variation in the characteristics of the runoff of the suspended river load (suspended sediment concentration, discharge, rate of runoff, and grain-size distribution) on a variety of space–time scales (daily, seasonal, and long-term). The main factors that affect the yield of suspended load in rivers that flow in volcanic areas include the water runoff, drainage area, and the abundance of unconsolidated volcanic deposits. The areas of recent volcanism in Kamchatka are characterized by the maximum values of potential scour of particles, the mean long-term suspended sediment concentration, and specific suspended sediment yield. The largest increment in the transport of suspended river load in areas of volcanic activity is observed after major eruptions. The daily variations in the transport of suspended load are controlled by the water regime of rivers on the slopes of active volcanoes, namely, periodic cessations of surface runoff because of filtering into volcanic deposits.  相似文献   

16.
Before 1900, the Missouri–Mississippi River system transported an estimated 400 million metric tons per year of sediment from the interior of the United States to coastal Louisiana. During the last two decades (1987–2006), this transport has averaged 145 million metric tons per year. The cause for this substantial decrease in sediment has been attributed to the trapping characteristics of dams constructed on the muddy part of the Missouri River during the 1950s. However, reexamination of more than 60 years of water‐ and sediment‐discharge data indicates that the dams alone are not the sole cause. These dams trap about 100–150 million metric tons per year, which represent about half the decrease in sediment discharge near the mouth of the Mississippi. Changes in relations between water discharge and suspended‐sediment concentration suggest that the Missouri–Mississippi has been transformed from a transport‐limited to a supply‐limited system. Thus, other engineering activities such as meander cutoffs, river‐training structures, and bank revetments as well as soil erosion controls have trapped sediment, eliminated sediment sources, or protected sediment that was once available for transport episodically throughout the year. Removing major engineering structures such as dams probably would not restore sediment discharges to pre‐1900 state, mainly because of the numerous smaller engineering structures and other soil‐retention works throughout the Missouri–Mississippi system. Published in 2009 by John Wiley & Sons, Ltd.  相似文献   

17.
洞庭湖城陵矶水道水力几何形态的研究   总被引：1，自引：1，他引：0  
黎明 《湖泊科学》1997,9(2):112-116
根据１９５１－１９８８年洞庭湖城陵矶站的水文测验资料,运用Ｌ．Ｂ．Ｌｅｏｐｏｌｄ河床力几何形态原理,建立洞庭湖出口－城陵矶水道河相关系式,研究该水道水力几何形态的特点及变化。研究表明,与河流水道相比,洞庭湖出口水道河宽指数ｂ随流量的变化较小,而水深指数ｆ及流速指数ｍ随流量的变化较大,河床横面具有窄深的特点。  相似文献   

18.
ABSTRACT

The suspended sediment rating curves for six stations on four rivers in western and northern Greece are investigated. For each station the suspended sediment load is a power function of the water discharge, which may be distinguished according to wet and dry seasons; the latter yields higher sediment loads for a given discharge than the former. This is due to the higher erosivity of dry season rainfall compared to wet season rainfall producing the same runoff. All rating curve exponents b lie in the range 2.5–3.5 for the wet and 2.0–3.0 for the dry season and are related to the constants a of the curves by empirical equations. The variation in a and b is explained in terms of the annual precipitation and area of the basin, the hypsometric fall, the main channel length, and the average bedslope of the river from the basin divide to the station, through empirical relationships, which also permit the prediction of rating curves for ungauged basins.  相似文献   

19.
A rating curve provides a reasonable estimate of the suspended sediment concentration at a given discharge. However, analysis of a detailed 9‐year time‐series of suspended sediment concentration (SSC) and discharge Q of the Meuse River in The Netherlands indicates that SSC is (besides discharge) controlled by exhaustion and replenishment of different sediment sources. Clockwise hysteresis and other effects of sediment exhaustion can be observed during and after flood events, and the effects of stockpiling of sediment in the river bed during low‐discharge periods are obvious in the SSC of the next flood. In a single regression equation we have implemented a parameter that represents the presence or absence of stock for sediment uptake. In comparison with a rating curve of SSC and Q, adding this parameter is shown to be a more reliable and comprehensive method to predict SSCs at all discharge regimes with all preceding discharge conditions, for single‐peaked and multi‐peaked runoff events as well as for low flow conditions. The method is probably applicable to other small‐ to medium‐scaled river basins. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

20.
This study analyses the changes in sediment transport regimes in the middle Yellow River basin (MYRB) using sediment rating parameters. Daily streamflow and suspended sediment concentration data were collected at 35 hydrological stations from the 1950s to 2016, which can be divided into three periods based on the type and intensity of human activities: the base stage before 1970, the restraining stage from 1971 to 1989, and the restoration stage after 2002. Data within each period were fitted by log‐linear sediment rating curves and the sediment rating parameters were utilized to analyse the spatial and temporal variations in sediment transport regimes. The results show that sediment rating parameters are indicative of sediment transport regimes. In the base stage and the restraining stage, the hydrological stations can be categorized into four groups based on their locations on the rating parameter plot. The stations with small drainage basins were characterized by the highest sediment transport regime, followed by those located in the coarse‐particle zone, the loess zone, and the mountainous/forest zone. In the restoration stage, the difference in sediment transport regimes between different geomorphic zones became less distinguishable than in previous stages. During the transition from the base stage to the restraining stage, sediment rating parameters showed no significant changes in sediment transport regimes in all four geomorphic groups. During the transition from the restraining stage to the restoration stage, significant changes were observed in the coarse‐particle zone and the mountain/forest zone, indicating that the revegetation programme and large reservoirs imposed a stronger influence on sediment transport regimes in these two zones than in the rest of the MYRB. This study provides theoretical support for evaluating sediment transport regimes with sediment rating parameters.  相似文献   

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