黄土高原大理河流域水沙耦合模型应用研究

水沙模型是定量描述水沙关系及水沙规律的重要工具,现阶段国内外对于水沙模型的研究大都为基于某个典型流域的经验统计模型或基于流域大量基础资料的物理模型,极大限制了其使用范围及模拟精度.本文建立了结构与参数均具有物理意义的流域水沙耦合物理概念模型,其优点是物理概念清楚,模拟精度高,实用性强,易于深入研究泥沙基本规律.该模型将概念性水文模型和泥沙模型耦合,提出水流挟沙能力和土壤抗侵蚀能力概念,用对数曲线近似描述流域土壤抗侵蚀能力的空间变异性,在拜格诺河道水流悬移质泥沙公式基础上建立概念性沟蚀产沙公式,参照水流汇集相似性建立泥沙汇集演算公式.选取黄河中游大理河流域4个不同流域尺度的实际流域对模型进行应用检验,模拟结果表明,该模型的水流泥沙两部分均有很高的模拟精度,可以很好地模拟黄河中游地区不同流域尺度和年际尺度上的洪水过程和泥沙产生及输移过程,充分证明了该模型结构、参数和计算方法的合理性,可用于定量分析流域内各项水保措施的减水减沙效益及水沙关系变化趋势,对该模型的推广应用可做进一步分析研究.     

防止河道泥沙淤积的最小生态环境需水量

水土流失问题是生态系统面临的重要问题. 对于多沙河道来说,必须维持一定的生态环境需水量用于输沙,以保证河道生态平衡. 本文以多沙河流为研究对象,以输沙动力学理论为基础,分析了河流输沙能力和水流挟沙能力,在此基础上提出了河道在不冲不淤的临界状态下河流最小流量的计算方法,此为防止河道泥沙淤积的最小生态环境需水量. 通过实际算例,本文还说明了所提出的计算方法的应用,以期为多沙河道水资源合理配置及生态平衡维护提供科学依据.     

三峡工程下游宜昌至沙市河段河床冲刷预测

在已建水库下游河床冲刷泥沙数学模型的基础上针对宜昌－沙市河段的河道特性,修改并建立了能够反映该河段水沙运动特性的一维水流泥沙数学模型,在此基础上,进行了三峡建库后,前２０年内宜昌－沙市河段的一维水沙运动及河床冲淤计算。     

波浪和风生浪流作用下的近岸海底泥沙运移模型的推广和应用

本文利用数值计算和经验公式相结合的方法,获得了在波浪和风生流和波浪共同作用下海底泥沙输移的二维模型.在此基础上,讨论了海底泥沙输移在风速、风向和泥沙粒径不同等三种情况下的变化特征;指出了经验公式对泥沙输移规律的适用范围以及风速、风向对于近岸处泥沙输移重要性.这一研究结果对近岸结构物的选址设计具有实际应用价值.     

非稳定流单井排放诱发地壳形变的研究──基于Neuman理论的无压含水层完整井

在高精度动态大地测量时,为考虑地下水单井排放对台站坐标的影响,需精细研究不同水流系统和地层模型下相应的定量计算问题．本文将地下水单井排放诱发地表位移的一般公式与Muman理论结合起来,导出了适用于各向异性和滞后反应的无压含水层完整井非稳定流单井排放诱发的地表位移的解析表达式,以20个结点的Hermite求积公式和15个结点的Gauss－laguerre求积公式,编制了相应的计算程序,给出了模拟算例．本文的研究在理论上比基于Boulton理论的相应研究更合理,在实践上此方案是可行的．     

非稳定流单井排放诱发地壳形变的研究──基于Neuman理论的无压含水层完整井

在高精度动态大地测量时,为考虑地下水单井排放对台站坐标的影响,需精细研究不同水流系统和地层模型下相应的定量计算问题．本文将地下水单井排放诱发地表位移的一般公式与Muman理论结合起来,导出了适用于各向异性和滞后反应的无压含水层完整井非稳定流单井排放诱发的地表位移的解析表达式,以20个结点的Hermite求积公式和15个结点的Gauss－laguerre求积公式,编制了相应的计算程序,给出了模拟算例．本文的研究在理论上比基于Boulton理论的相应研究更合理,在实践上此方案是可行的．     

黄河中游多沙粗沙区的风水两相侵蚀产沙过程

以黄河中游各支流的资料为基础,提出了风水两相侵蚀产沙的概念,并建立了风水两相侵蚀产沙模式,从而为这一地区强烈的侵蚀产沙过程提出了新的解释.风力作用与水力作用在时间上是相异的,前者为高含沙水流搬运作用准备了大量粗颗粒泥沙,存贮在坡面、沟道和河道中;后者则形成了富含细颗粒的暴雨径流,为粗颗粒泥沙的搬运提供了动力条件.由此形成了高含沙水流,导致了这一地区高强度的侵蚀产沙过程.     

钻井岩心古水流方向确定方法和原理

为了实现钻井岩心信息最大化的应用.首先利用古地磁技术对钻井岩心进行原始方位恢复,然后通过测定岩心上具有古水流指向性的沉积构造的参数,或者通过测定岩心磁性组构判定古流向,最后经过岩心校正得出研究区的古水流方向.文中以钻井岩心上的斜层理为例,推导出其在岩心坐标系中的倾向和倾角的表达式,经过公式校正得到真倾向和真倾角的表达式,确定古流向.最终将井位、岩心恢复及古水流计算结果综合反映,获得每个井位的古水流方向,进而通过连片处理分析,可获得某区块的局部及整体的古水流趋势方向,预测砂体的展布方位.本文为钻井岩心古水流方向的确定提供了研究方法,实现了岩心信息最大化利用,可以指导油田的进一步勘探开发.     

利用机械取样和浅地层剖面数据反演河底泥沙参数（英文）

河流动力学研究需要河底泥沙物性参数(孔隙率、渗透率和波速等)作为依据,机械取样和浅地层剖面探测是获取物性的重要途径。取样时的机械扰动使测试结果产生偏差,仅利用浅地层剖面数据获取河底特性有限,本文将两者结合起来开展反演研究。将取样测试的级配作为先验信息,进而根据Kozeny-Carman公式确定孔隙率和渗透率的关系。从浅地层剖面数据中提取了水-泥沙界面的声波反射系数。基于等效密度流模型,结合Kozeny-Carman公式和声波反射系数,提出了一种表层淤积泥沙参数反演方法。经过黄河库区试验,得到多个断面的密度和波速等参数,并获取泥沙物性参数的空间变化特征。对比发现,取样点的反演结果与测试结果较为一致,证明了本文提出泥沙参数反演方法的有效性。     

降雨动态系统响应曲线修正方法在黄土区域水沙模拟中的应用

采用水沙模型对流域水沙过程进行计算是目前分析和研究黄土地区水土流失、水沙锐减等问题的有效途径由于降雨的时段均化和缺测、漏测、误测等问题,导致水沙模型的重要输入项和动力因子——降雨资料存在误差,进而影响水流和泥沙过程模拟精度因此,本研究将降雨动态系统响应曲线的误差修正方法与概念性水沙模拟模型相结合以提高水沙过程模拟精度此方法将水沙模型的水流模拟部分看作响应系统,通过修正水沙模型的重要输入项——面平均雨量,利用修正之后的面平均雨量系列,通过模型重新计算以提高模型对产汇流和产汇沙过程的模拟精度通过理想案例验证该方法可行性后,选择黄土地区曹坪流域进行检验,结果表明修正后的水流和泥沙过程模拟精度均有显著提高,平均提高幅度分别为17.56%和15.86%.     

THE SOURCE OF COHESIVE SEDIMENT AND ITS TRANSPORT IN THE YANGTZE ESTUARY AND NEAR SEA

In the light of the regional physiography and its effect on clay mineral composition of cohesive sediment (d < 0.005 mm) the source area of cohesive sediment in the Yangtze Estuary can be identified as three supplying regions: the main stem of the Yangtze River, the deltaic region of the abandoned Yellow River including the northwest Huanghai Sea and the Hangzhou Bay. Based on the evaluation of clay mineral composition in the supplying regions and the converging region, a computational model is established. More than 89.6% of cohesive sediment comes from the Yangtze River, a considerable amount is replenished from the deltaic region of the abandoned Yellow River while some part of the cohesive sediment load is transported from the Yangtze Estuary to the Hangzhou Bay. Computation results reveal that the annual deposit of cohesive sediment in the Yangtze Estuary amounts to 45.54 x 106 t. The annual cohesive sediment load replenished from the deltaic region of the abandoned Yellow River is 27.30 x 106t, while the annual cohesive sediment load transported to the Hangzhou Bay is 22.47 x 106 t. The amount of deposit in the Yangtze Estuary has been checked against the value obtained by comparing bathemetry of the Yangtze Estuary in 1915 and 1963.     

Trends in suspended sediment grain size in the upper Yangtze River and its tributaries,as influenced by human activities

Abstract

Based on data from five hydrometric stations, Pingshan station on the Jinshajiang River, Gaochang station on the Minjiang River, Wulong station on the Wujiang River, Wusheng station on the Jialingjiang River and Yichang station on the Yangtze River, a study has been made of the temporal variation in grain size of suspended sediment load in the upper Yangtze River. The results show that in the past 40 years, the grain size of the suspended sediment load in the main stem and major tributaries of the upper Yangtze River has had a decreasing trend, that can be explained by the effect of reservoir construction and implementation of soil conservation measures. The reservoirs in the upper Yangtze River Basin, all used for water storage for hydro-electric generation and/or irrigation, have trapped coarse sediment from the drainage area above the dam and, thus, the sediment released now is much finer than before the construction of the reservoirs. The downstream channels are all gravel-bedded or even in bedrock, with little fine sediment, and thus, the released flow can hardly get a supply of fine sediment through eroding the bed. Then, after the downstream adjustment, the grain size of suspended sediment is still fine. Large-scale soil conservation measures have significantly reduced sediment yield in some major sediment source areas. The relatively coarse sediment is trapped and, thus, the sediment delivered to the river becomes finer.     

A semi-physical sediment yield model for estimation of suspended sediment in loess region

Sediment yield is a complex function of many environmental factors including climate,hydrology,vegetation,basin topography,soil types,and land cover.We present a new semi-physical watershed sediment yield model for the estimation of suspended sediment in loess region.This model is composed by three modules in slope,gully,and stream phases.For slope sediment yield,a balance equation is established based on the concept of hydraulic erosion capacity and soil erosion resistance capacity.According to the statistical analysis of watershed characteristics,we use an exponential curve to approximately describe the spatial variability of watershed soil erosion resistance capacity.In gully phase,the relationship between gully sediment concentration and flow velocity is established based on the Bagnold'stream power function.In the stream phase,we assume a linear dependence of the sediment volume in the reach on the weighted sediment input and output.The proposed sediment yield model is operated in conjunction with a conceptual hydrologic model,and is tested over 16 regions including testing grounds,and small,medium and large watersheds in the loess plateau region in the mid-reach of Yellow River.Our results indicate that the model is reasonable in structure and is able to provide a good simulation of sediment generation and transportation processes at both flood event scale and inter-annual time scale.The proposed model is generally applicable to the watersheds with soil texture similar to that of the loess plateau region in the Yellow River basin in China.     

Quantitatively distinguishing sediments from the Yangtze River and the Yellow River using δ Eu<Subscript>N</Subscript>-ΣREEs plot

Sediment samples were collected from the lower channel of the Yangtze River and the Yellow River and the contents of rare earth elements (REEs) were measured. In addition, some historical REEs data were collected from published literatures. Based on the δ Eu_N-ΣREEs plot, a clear boundary was found between the sediments from the two rivers. The boundary can be described as an orthogonal polynomial equation by ordinary linear regression with sediments from the Yangtze River located above the curve and sediments from the Yellow River located below the curve. To validate this method, the REEs contents of sediments collected from the estuaries of the Yangtze River and the Yellow River were measured. In addition, the REEs data of sediment Core 255 from the Yangtze River and Core YA01 from the Yellow River were collected. Results show that the samples from the Yangtze River estuary and Core 255 almost are above the curve and most samples from the Yellow River estuary and Core YA01 are below the curve in the δEu_N-ΣREEs plot. The plot and the regression equation can be used to distinguish sediments from the Yangtze River and the Yellow River intuitively and quantitatively, and to trace the sediment provenance of the eastern seas of China. The difference between the sediments from two rivers in the δEu_N-ΣREEs plot is caused by different mineral compositions and regional climate patterns of the source areas. The relationship between δEu_N and ΣREEs is changed little during the transport from the source area to the river, and from river to the sea. Thus the original information on mineral compositions and climate of the source area was preserved. Supported by National Natural Science Foundation of China (Grant Nos. 40506016, 40576032, and 90411014)     

SEDIMENT TRANSPORT IN THE YANGTZE RIVER ESTUARY

SEDIMENT TRANSPORT IN TIIE YANGTZE RIVER ESTUARYSHEN Zhigang'ANSTa^CTThe hy~ntalc and the sedimen tranSport Patter'nS within the estUaIy of the YangtZe mver arecomPlex because of intemehon of fluvial and the hdal forCes, depending on freshwate discharge andhdal range. Based on the data measuIed in meent years, thes papo discusses the characterishcs of flowand sNnt movemen in the tw forer EstUaIy and their iIifluences on the evolution of theestuaryKey W: YangtZe mver…     

PREDICTION OF IMPACT OF THE THREE GORGES PROJECT ON ESTUARY BEACH OF THE YANGTZE RIVER

ＰＲＥＤＩＣＴＩＯＮＯＦＩＭＰＡＣＴＯＦＴＨＥＴＨＲＥＥＧＯＲＧＥＳＰＲＯＪＥＣＴＯＮＥＳＴＵＡＲＹＢＥＡＣＨＯＦＴＨＥＹＡＮＧＴＺＥＲＩＶＥＲＷｅｉｂｉｎｇＦＥＮＧ１ＹｉｇａｎｇＷＡＮＧ２ａｎｄＸｉｕｃｈｅｎｇＺＨＯＮＧ３ＡＢＳＴＲＡＣＴＡｌｔｈｏ...     

Fine sediment carrying capacity of combined wave and current flows

The so-called fine sediment in many coastal areas and estuaries in China is mostly referred to the mixture of cohesive sediment and non-cohesive sediment. To predict the mixed type time sediment transport, sediment carrying capacity formulae combined with the 2-D suspended sediment transport equation and morphologic equation have been widely used in China. In the present study, the sediment carrying capacity formula suggested by Dou et al. （1995） for wave conditions has been improved and implemented for the prediction of sediment transport in nearshore regions where wave activities are significant. The improvement is based on the wave energy dissipation principle inside and outside the surf zone. In the improved formula, sediment in suspension increases with the magnitude of the wave period and this feature complies with general observations. More than 300 laboratory and field measured data sets have been reviewed and 12 of them have been used to verify and determine the major coefficients in the improved formula. The application of the sediment carrying capacity model in combined wave and current situations shows that the model can faithfully reproduce the cross-shore sediment concentration distributions at the southwest coast of Bohai Bay.     

CASE STUDIES OF THREE-DIMENSIONAL NUMERICAL SIMULATION FOR TOTAL SEDIMENT TRANSPORT

1 INTRODUCTION With advances in computer technology and numerical methods, three-dimensional (3D) mathematical models for sediment transport are gradually applied more often and for more practical projects of hydraulic engineering. Three-dimensional mathematical river models can describe not only the secondary flow, but also the transport, deposition, and erosion of sediment in the river channel and the flood plain. However, at present the theories of sediment transport are not as well de…     

洞庭湖冲淤变化分析(1956-1995年)

根据１９５６－１９９５年洞庭湖水文泥沙原型观测和地形测绘等翔实资料,运用输沙量法和地形法对洞庭湖冲瘀变化进行了认真的统计分析,分析结果表明,洞庭湖来水量以四水为主,占５７．８％,来沙量以四口为主,多年平均沉积率为７４．０％,出湖仅占２６．０％;淤积量及湖水沙量随着四分流分沙比的减少而减少。     

Sediment transport at the network scale and its link to channel morphology in the braided Vjosa River system

In this article we apply the CASCADE network-scale sediment connectivity model to the Vjosa River in Albania. The Vjosa is one of the last unimpaired braided rivers in Europe and, at the same time, a data scarce environment, which limits our ability to model how this pristine river might respond to future human disturbance. To initialize the model, we use remotely sensed data and modeled hydrology from a regional model. We perform a reach-by-reach optimization of surface grain size distribution (GSD) and bedload transport capacity to ensure equilibrium conditions throughout the network. In order to account for the various sources of uncertainty in the calculation of transport capacity, we performed a global sensitivity analysis. The modeled GSD distributions generated by the sensitivity analysis generally match the six GSDs measured at different locations within the network. The modeled bedload sediment fluxes increase systematically downstream, and annual fluxes at the outlet of the Vjosa are well within an order of magnitude of fluxes derived from previous estimates of the annual suspended sediment load. We then use the modeled sediment fluxes as input to a set of theoretically derived functions that successfully discriminate between multi-thread and single-thread channel patterns. This finding provides additional validation of the model results by showing a clear connection between modeled sediment concentrations and observed river morphology. Finally, we observe that a reduction in sediment flux of about 50% (e.g., due to dams) would likely cause existing braided reaches to shift toward single thread morphology. The proposed method is widely applicable and opens a new avenue for application of network-scale sediment models that aid in the exploration of river stability to changes in water and sediment fluxes.