水库联合运行对库下汛期河道过水断面形态参数变化率的影响——以黄河内蒙古河段为例

水库联合运行对于库下河道的影响是河流地貌学近年来的热点问题,如何定量表征河道的因应调整则是其难点所在。基于同水位河道过水断面形态参数变化率分析方法,针对黄河内蒙古河段磴口、巴彦高勒、三湖河口、头道拐4个水文站,利用刘家峡水库、龙羊峡水库联合运行之前的1978-1982年、之后的2008-2012年汛期前后实测断面资料,计算了相应年份上述各站同水位下的河道断面面积、水面宽、平均水深等特征参数在经历汛期冲刷后的变化率。结果表明,每年在经历汛期洪水冲刷之后,上述形态参数总体上以增大为主,变化率为正值;大型水库联合运行之前与之后的两个时期相比,同水位下河道断面面积、水面宽和平均水深的变化率分别减小了3.4、3.5和2.8倍。过水断面形态参数的沿程空间变化也由之前的上凸形曲线变为之后增减相间的"S"形曲线。其原因在于,大型水库联合运行削减了洪峰流量、降低了汛期最大流速,从而导致洪水造床能力显著变弱,河道断面形态参数的变化率因之显著减小。大型水库联合运行使黄河内蒙古河道明显萎缩,这不利于可能遭遇的极端大洪水的安全行洪,因此,需要合理利用这些水库的调节功能,有效控制汛期总水沙量和洪峰流量,避免因过度调节而使河道持续萎缩,为可能出现的极端大洪水的安全行洪创造条件。     

黄河流域动力系统泥沙时序混沌特征分析——地理系统综合研究的一种尝试

选取黄河头道拐、潼关、花园口和利津断面1952²000年的泥沙含量为时序,在G-P重构相空间的基础上,分别计算了各断面泥沙时序的关联维（D2）、K2熵和Hurst指数。结果表明,各断面的最小饱和镶嵌维（m）、D2和K2熵分别为5、3.24和0.13,说明黄河流域各级系统均具有混沌特征,并且从上游到下游混沌特性逐渐增强。随着混沌特性的增强其平均可预报时间下降,头道拐断面为8年,其余断面为3年。各断面Hurst指数均大于0.68,在可预报时间内,各断面泥沙时序具有持续性下降趋势,并用2001²004年实际数据得到了验证。文章还给出了黄河流域动力系统的一般形式,该系统至少需要8个状态变量,2个控制变量。     

黄河宁蒙河段悬沙冲淤量时空变化及其影响因素

通过对黄河宁蒙河段6个水文站1952~2003年间的实测悬移质泥沙资料,运用输沙平衡方法,对划分的5个时段和5个区段的悬沙冲淤量进行了计算分析,探讨宁蒙河段悬沙冲淤量的时空变化规律。黄河上游无大型水库的1952~1959年间和水库建成坝下河道充分调整后的1994~2003年间,宁蒙河段强烈淤积,年均悬沙淤积量分别为0.9588亿t/a和0.9503亿t/a;而期间的三个时段,年均悬沙分别为净侵蚀0.6127亿t/a、微淤0.0161亿t/a和较强淤积0.7475亿t/a。年均悬沙淤积量在宁蒙河段为0.345亿t/a;在宁夏河段为0.076亿t/a,其中下沿河~青铜峡区段微淤,青铜峡~石嘴山区段冲淤平衡;在内蒙古河段总和为0.269亿t/a,石嘴山~巴彦高乐、巴彦高乐~三湖河口、三湖河口~头道拐三个区段分别为0.0084亿t/a、0.113亿t/a和0.147亿t/a,沿程增大。悬沙淤积量的时间变化主要受到区间支流来沙量变化和水库建设的双重影响,而空间变化主要受到青铜峡水库拦沙以及刘家峡、龙羊峡水库消减洪峰的影响。黄河宁蒙河段处于构造沉降区,淤积是总趋势,人类活动可以引起个别时段、区段发生侵蚀,但无法改变其沉积的总趋势。     

黄河内蒙古段洪峰特征及水沙关系变化

本文通过黄河头道拐站1950-2009 年水沙年系列进行突变点分析, 识别出1969 年、1986 年、1996 年3 个突变点, 将黄河内蒙古段水文过程划分为4 个时期。在此基础上, 利用内蒙古段6 个水文站长系列日流量、日含沙量及泥沙组成数据, 划分了各站的夏汛洪峰, 并统计分析了分期洪峰的水沙分布特征和洪峰水沙关系, 揭示出夏汛洪峰流量和输沙率逐渐减少的规律:1996-2006 年与1954-1968 年相比, 夏汛洪峰水沙量占全年水沙的比例都减少了约一半, 流量级频率与输沙率乘积的峰值对应的流量也降低了约一半。分析认为, 黄河内蒙古段夏汛洪峰特征阶段性变化既有大型水库的影响, 又有气候变化及人类活动的影响, 而且后者的作用越来越大。分析发现, 20 世纪90 年代以前, 黄河上游水沙变化只是改变了内蒙古段来沙中粗颗粒泥沙的水沙关系, 显示出大流量输送粗颗粒泥沙能力相对增强的趋向;进入内蒙段后, 通过泥沙冲淤调整, 分粒径组泥沙水沙关系变化比较复杂。近期在水沙条件巨大变化下, 河流的输沙特性并没有发生根本变化, 但是无论全沙还是分组沙, 水沙关系曲线变陡, 大流量输送泥沙能力相对增强。     

大型水库运行下内蒙古河道泥沙侵蚀淤积过程

 通过1954—2000年黄河泥沙资料分析,黄河内蒙古河段侵蚀淤积过程对上游水库运行的响应主要表现为:①盐锅峡和三盛公首先将黄河输沙能力由7.33 kg·m-3降为6.27 kg·m-3, 使内蒙古河道由自然淤积状态转变为侵蚀下切状态,小于0.1 mm泥沙侵蚀速率高于大于0.1 mm泥沙淤积速率,河道发生粗化现象;②）刘家峡和青铜峡水库将黄河输沙能力降为3.91 kg·m-3,促使黄河河道中大于0.01 mm泥沙淤积速率大于小于0.01 mm泥沙侵蚀速率,使内蒙古河道发生粗化淤积现象;③龙羊峡水库将黄河输沙能力进一步降为 3.48 kg·m-3,加剧黄河内蒙古河道淤积现象, 大于0.01 mm泥沙和小于0.01 mm泥沙均呈现出淤积状态,淤积速度与黄河上游无水库运作时的自然状态相似。     

黄河上游内蒙古河段平滩流量对人类活动和气候变化的响应

冲积河流平滩流量既反映了河道尺度上的水文-地貌耦合关系,又与流域因素密切相关。从这一概念出发,以黄河上游内蒙古河段为例,研究了平滩流量的变化,并在流域层面与河道层面上对其成因进行了研究。结果表明：上游水库调节改变了出库流量过程,使汛期流量大幅度减小,泄流过程均匀化,因而平滩流量减小。在龙羊峡水库修建后洪水流量减小导致漫滩机遇降低的情形下,泥沙淤在主槽内,也是平滩流量减小的重要原因。泥沙冲淤对于平滩流量的影响存在着某种累积或滞后效应,巴彦高勒平滩流量Q_bf,BY不仅与当年的冲淤量有关,还与以前冲淤量有关,前4 a平均淤积量对平滩流量的影响最大。建立了平滩流量与前4 a累计淤积量、年均流量、年最大日流量的多元回归方程,该方程表明平滩流量既与当年的流量特征相联系,也与一定时间尺度上河道冲淤造成的后果相联系,反映了某种水文地貌耦合关系。研究还表明,存在着以下因果关系链：龙羊峡水库修建→汛期来沙系数增大→河道淤积加强→平滩流量减小。因此,通过改变龙羊峡水库的运用方式,增大汛期下泄流量,可以减小河道淤积、增大平滩流量,从而增大下泄洪水的能力,降低凌汛期间的防洪压力。平滩流量的变化是流域因素变化的结果,所建立的多元回归方程表明,在50 a的时间尺度上,暖干化指标的增大、引水率的增大、水库总库容的增大和天然径流系数的减小,是黄河上游平滩流量减小的原因。     

渭河下游河道调整过程中的复杂响应现象

应用系统复杂响应的原理研究三门峡水库上游渭河河道调整过程,表明上游河道河床形态对基面上升所作出的响应是复杂的,弯曲系数的变化为先减小而后增大,宽深比的变化是先增大后减小,比降由先减小而后增大,最后均趋于稳定.     

黄河上游内蒙古段河床演变及其与水沙变化的关系

对黄河内蒙古段河道大断面进行了连续4 a的测量,分析了断面泥沙冲淤与形态调整的变化过程;通过对河床形态指标变化与水沙条件的相关分析,揭示了河床调整主要的影响因素。结果显示：近4 a内不存在河槽萎缩的现象,整个河段河道存在总的冲刷降低的趋势,继承了自2004年以来该段河道以深度加大为主,河槽逐渐缓慢扩大的变化方向。整个河段平均从2011年汛后至2014年汛后,全断面冲刷了64 m²,河槽河底降低了0.16 m,河槽断面面积增加了4.4%,平均深度增加了4.9%,河槽宽度只增加了0.88%,河槽宽深比减小了4.8%。河槽冲刷和形态调整主要发生在2011年汛后至2012年汛后期间,与2012年较大的洪峰有关。分析河槽冲淤和断面形态变化与水沙条件的关系,结果显示滩唇高度、河槽过水面积、平均深度及宽深比变率与流量大小关系密切。滩唇高度、河槽过水面积、平均深度随着流量的增大而增加,宽深比随着流量的增大而减小。相反,河床断面面积和主槽宽度的变化与水沙条件的关系不显著。除了滩唇高度与平均含沙量有关外,平均含沙量和来沙系数与河床冲淤以及河槽形态变化之间关系都不显著。揭示出近年来内蒙河道主槽以垂向冲淤为主,并且流量变化控制着河槽冲淤与形态调整过程。     

黄河上游近60 a径流量与降水量变化特征研究

为探究黄河上游径流量与降水量变化特征,基于唐乃亥、下河沿、头道拐3个水文站近60 a的降水量、径流量资料,采用线性倾向趋势检验、Mann-Kendall检验法（M-K趋势检验）、Spearman秩次相关检验、M-K突变检验、Pettitt非参数检验、有序聚类分析、累积距平法、双累积曲线等分析方法对比研究了黄河上游及上游不同子区域降水量和径流量的变化特征,并讨论了径流量对降水量的响应关系。结果表明：黄河上游降水量呈不显著增加趋势,在2003年发生突变,突变前后变化率为4.67%;径流量呈显著减少趋势,突变年份为1986年,突变前后变化率为35.34%。3个子区域年降水量变化趋势分别呈显著增加、不显著增加和显著减少趋势,径流量均呈减少趋势。以唐乃亥以上的Ⅰ区为基准区时,唐乃亥—下河沿所在的Ⅱ区降水量因素对径流量的影响达到25.08%,非降水量因素为74.92%,而下河沿—头道拐的Ⅲ区,降水量对径流量的影响为32.14%,非降水量因素为67.86%。研究结果对黄河流域水资源综合管理与科学配置具有参考意义。     

黄河下游河道输沙功能的时间变化及其原因

以输出某一河道的泥沙总量与进入这一河道的泥沙量之比来定义河道输沙功能,以此为指标研究了黄河下游输沙功能的时间变化。研究表明,近50年来黄河下游河道输沙功能表现出随时间而减小的明显趋势。在总的减小趋势中,由于水库运用方式与下游水沙组合的不同,河道输沙功能指标具有明显的差异,可以划分为6个阶段。1986¹997年,由于降水偏少,且人类大量引水,黄河下游进入连续枯水的水文系列,河道萎缩,输沙功能迅速降低,此时段中输沙功能指标的时段平均值为0.62,为有水沙记录以来最低的时期。对于黄河下游输沙功能指标与流域因子和河道特性因子的时间变化系列进行了比较,以揭示输沙功能减小的原因。结果表明,黄河下游河道输沙功能指标与流域平均年降水量、兰州站和三门峡站汛期径流占年径流百分比、游荡段典型断面平滩水位下断面面积、花园口站和高村站水面比降等因子有同步减小的关系,并随流域水土保持面积、人类引水量及其占天然径流量比率的增大而增大,说明这些因子的变化导致了黄河下游输沙功能的减弱。     

黄河内蒙古头道拐断面河道变化及其对上游水库的响应(英文)

The application of dams built upstream will change the input conditions,including water and sediment,of downstream fluvial system,and destroy previous dynamic quasi-equilibrium reached by channel streamflow,so indispensable adjustments are necessary for downstream channel to adapt to the new water and sediment supply,leading the fluvial system to restore its previous equilibrium or reach a new equilibrium.Using about 50-year-long hydrological,sedimentary and cross-sectional data,temporal response processes ...     

Channel change at Toudaoguai Station and its responses to the operation of upstream reservoirs in the upper Yellow River

The application of dams built upstream will change the input conditions, including water and sediment, of downstream fluvial system, and destroy previous dynamic quasi-equilibrium reached by channel streamflow, so indispensable adjustments are necessary for downstream channel to adapt to the new water and sediment supply, leading the fluvial system to restore its previous equilibrium or reach a new equilibrium. Using about 50-year-long hydrological, sedimentary and cross-sectional data, temporal response processes of Toudaoguai cross-section located in the upper Yellow River to the operation of reservoirs built upstream are analyzed. The results show that the Toudaoguai cross-section change was influenced strongly by upstream reservoir operation and downstream channel bed armoring thereafter occurred gradually and extended to the reach below Sanhuhekou gauging station. Besides, median diameter of suspended sediment load experienced a three-stage change that is characterized by an increase at first, then a decrease and an increase again finally, which reflects the process of channel bed armoring that began at Qingtongxia reservoir and then gradually developed downstream to the reach below Sanhuhekou cross-section. Since the joint operation strategy of Longyangxia, Liujiaxia and Qingtongxia reservoirs was introduced in 1986, the three-stage change trend has become less evident than that in the time period between 1969 and 1986 when only Qingtongxia and Liujiaxia reservoirs were put into operation alone. In addition, since 1987, the extent of lateral migration and thalweg elevation change at Toudaoguai cross-section has reduced dramatically, cross-sectional profile and location tended to be stable, which is beneficial to the normal living for local people.     

长江中下游河道冲淤与河床自动调整作用分析

根据实测河道测图资料及水沙资料，首次利用断面地形法和输沙平衡法较全面地系统地计算分析了长江中下游河道泥沙的冲淤变化及其分布规律，计算结果表明宜昌－大通段呈冲槽、淤滩、淤汊特征；同时剖析和验证了长江中下游河床具有较强的自动调整作用。     

Effects of Stronach Dam removal on fluvial geomorphology in the Pine River, Michigan, United States

Although dam removal has been increasingly used as an option in dam management, and as a river restoration tool, few studies provide detailed quantitative assessment of the geomorphological response of rivers to dam removal. In this study, we document the response of the Pine River, Michigan, to the gradual removal of Stronach Dam. In 1996, prior to the initiation of removal, 31 permanent cross-sectional transects were established in the 10-km study area. These transects were surveyed annually during the course of the removal (1996–2003) and for the three years following removal (2004–2006). Dam removal resulted in progressive headcutting of sediments in the former impoundment, extending upstream 3.89 km of the dam. Over the course of the 10 years since dam removal was initiated, a net total of 92 000 m³ of sediment erosion occurred. The majority of sediments stored in the former reservoir remained in place, with only 12% of the estimated reservoir sediment fill being eroded. Approximately 14% of the net erosion was deposited within the stream channel 1 km downstream of the dam location, with the remainder being transported further downstream or deposited in the floodplain. Sediment fill incision resulted in a narrower and deeper channel upstream, with higher mean water velocity and somewhat coarser substrates. Downstream deposition resulted in a wider and shallower channel, with little change in substrate size composition. Counter-intuitively, water velocity also increased downstream because of the increased slope that developed. Prior to removal, bedforms in the former impoundment were dominated by runs but are showing signs of restoration toward reference conditions. Continuing changes in river geomorphology are evident even three years following removal and are likely to occur for years to come.     

基于元胞模型的河道纵剖面调整动态模拟

纵剖面的调整是河道演化的重要内容,其对于河道整治及水沙灾害机理研究都具有重要意义。利用多年观测资料可以较为精确地分析和推断河道纵剖面的调整过程。但是,这种方法不能从过程机理上对纵剖面的调整进行模拟分析。而自然条件下河道边界条件的复杂性使得对河道纵剖面演化的物理过程模拟有很大困难。元胞自动机是一个时间、空间和状态都离散的动力模型,是研究复杂系统动态演化过程的有力工具。本文以黄河尾闾河道为例,利用一维元胞模型对河道纵剖面的调整进行动态模拟。模拟揭示了河道纵剖面在初始形态、不同水沙组合以及河道延伸等情况下的演化规律与趋势。     

The coast evolution and regulation in Wanquan River Estuary, Hainan Island

In this paper, sediment samples were collected along the Wanquan beaches and sieved in the laboratory in order to obtain the grain size distributions and associated parameters, i.e. mean grain size, sorting coefficient and skewness. Furthermore, we have calculated the longshore drift sediment transport rates and equilibrium cross-sectional areas of the entrance channel by using the method of sedimentary dynamics. The results indicate that the longshore drift sediment transport is dominated by waves with a direction from south to north, which result in rapid changes of the entrance channel. Therefore, some suggestions were proposed for improving the water quality and restoring the ecosystem of estuary. The engineering method includes increasing the sea-route of entrance channel, tidal prism and water exchanges in Shamei Lagoon.     

海南岛万泉河口海岸动态及其整治对策

In this paper, sediment samples were collected along the Wanquan beaches and sieved in the laboratory in order to obtain the grain size distributions and associated parameters, i.e. mean grain size,sorting coefficient and skewness. Furthermore, we have calculated the longshore drift sediment transport rates and equilibrium cross-sectional areas of the entrance channel by using the method of sedimentary dynamics. The results indicate that the longshore drift sediment transport is dominated by waves with a direction from south to north, which result in rapid changes of the entrance channel.Therefore, some suggestions were proposed for improving the water quality and restoring the ecosystem of estuary. The engineering method includes increasing the sea-route of entrance channel,tidal prism and water exchanges in Shamei Lagoon.     

Immediately downstream effects of Three Gorges Dam on channel sandbars morphodynamics between Yichang-Chenglingji Reach of the Changjiang River,China

Sandbars are of vital ecological and environmental significance, which however, have been intensively influenced by human activities. Morphodynamic processes of sandbars along the Yichang-Chenglingji Reach of the Changjiang River, the channel immediately downstream of the Three Gorges Dam (TGD), are assessed based on remote sensing images between 2000 and 2016. It can be found that the entire area of sandbars reduces drastically by 19.23% from 149.04 km² in 2003 to 120.38 km² in 2016, accompanied with an increase in water surface width. Owing to differences in sediment grain size and anti-erosion capacity, sandbar area in the upstream sandy gravel reach (Yichang-Dabujie) and downstream sandy reach (Dabujie-Chenglingji) respectively decreases by 45.94% (from 20.79 km² to 11.24 km²) and 14.93% (from 128.30 km² to 109.14 km²). Furtherly, morphological evolutions of sandbars are affected by channel type: in straight-microbend channel, mid-channel sandbars exhibit downstream moving while maintaining the basic profile; in meandering channel, point sandbars show erosion and deposition in convex and concave bank respectively, with mid-channel sandbars distributing sporadically; in bending-branching channel, point sandbars experience erosion and move downstream while mid-channel sandbars show erosion in the head part along with retreating outline. We document that the primary mechanism of sandbars shrinkages along the Yichang-Chenglingji Reach can be attributed to TGD induced suspended sediment concentration decreasing and increasing in unsaturation of sediment carrying capacity. Additionally, channel type can affect the morphological evolution of sandbars. Along the Yichang-Chenglingji Reach, sandbars in straight-microbend channel are more affected by water flow than that in bending-branching channel.     

The late Quaternary evolution of the Negro River, Amazon, Brazil: Implications for island and floodplain formation in large anabranching tropical systems

The Rio Negro has responded significantly in the Late Pleistocene and Holocene to lagged environmental changes largely associated with activity during the last glacial in the Amazon basin. On the basis of geological structure, the Rio Negro can be divided into six distinct reaches that each reflects very marked differential processes and geomorphological styles. No deposits of the Upper Pleniglacial were recognized in the field. The oldest recognizable Late Pleistocene alluvial unit is the Upper Terrace of Middle Pleniglacial age (ca. 65–25 ka) (reach I), tentatively correlated with the oldest terrace identified on the left bank of reach III. At that time, the river was mainly an aggradational bed load system carrying abundant quartz sand, a product of more seasonal conditions in the upper catchment. The late glacial (14–10 ka) is represented by a lower finer-grained terrace along the upper basin (reach I), which was recognized in the Tiquié, Curicuriarí, and Vaupes rivers. At that time, the river carried abundant suspended load as a response to climatic changes associated with deglaciation.Since about 14 ka, the river has behaved as a progradational system, infilling in downstream series a sequence of structurally controlled sedimentary basins or ‘compartments,’ creating alluvial floodplains and associated anabranching channel systems. Reach II was the first to be filled, then reach III, both accumulating mainly sand. Fine deposits increase downstream in reach III and become predominant in some anabranch islands of the distal reach. The lowermost reaches of the Negro (V and VI) have been greatly affected by a rising base level and associated backwater effect from aggradation of the Amazon during late glacial and recent times. Reach V has acted almost entirely as a fine sediment trap. The remarkable Anavilhanas archipelago is the product of Holocene deposition in the upper part of this sedimentary basin; however, suspended sediment load declined about 1.5 ka, prior to the lower part of this basin becoming infilled.The progradational behavior of the Rio Negro, filling tectonic basins as successive sediment traps with sand in the upper basins and fines in the downstream ones, illustrates how a large river system responses to profound changes in Late Quaternary base level and sediment supply. The most stable equilibrium conditions have been achieved in the Holocene in reaches IIb and IIIa, where an anabranching channel and erosional–relictual island system relatively efficiently convey water and sediment downstream. Reaches IIIb and V never achieved equilibrium conditions during the Holocene, characterised as they are today with incomplete floodplains and open water.     

调水调沙以来黄河尾闾河道冲淤演变及其影响因素

2002年开始的黄河调水调沙改变了进入黄河口的水沙条件,必然引起尾闾河道地貌的显著调整。根据黄河尾闾河道利津以下的断面实测高程数据,建立基于正交曲线网格的河道DEM,结合河床形态与水沙条件变化,综合研究黄河尾闾河道冲淤的时空演变及其影响因素。结果表明,调水调沙以来尾闾河道冲刷明显,2002—2017年累计冲刷6240万m ³,根据冲淤速率可以分为3个阶段：快速冲刷阶段（2002—2005年）冲刷速率为1443万m ³/a;冲刷减慢阶段（2006—2014年）冲刷速率为139万m ³/a;以及淤积阶段（2015—2017年）,淤积速率为263万m ³/a。其中,调水调沙初始4年尾闾河道的冲刷量占总冲刷量的80%,2006年以后冲刷强度逐渐减弱,甚至转为淤积。从季节上看,主要表现为汛期冲刷,非汛期淤积;从空间上看,越往口门方向,冲刷强度越小。调水调沙改变了入海水沙的年内分配,造成了尾闾河道的持续冲刷,入海流路也发生多次调整。但经过多年冲刷,河床整体下切,加上河口淤积延伸影响,调水调沙对尾闾河道的冲刷效率在持续降低。受河口海域淤积影响,近口门段在经历冲刷后转为淤积,河道纵比降减缓,增加了尾闾的不稳定性。