三峡大坝下游水位变化与河道形态调整关系研究

三峡水库蓄水利用已有13年,对坝下游洪、枯水位和河道形态调整的影响已初步显现,通过对1955-2016年长江中游水位、河道地形等资料的分析,结果表明：① 坝下游各水文站同流量枯水位下降、洪水位变化不大,最低水位上升,最高水位下降趋势;② 2002年10月-2015年10月枯水河槽冲刷量占平滩河槽冲刷量的95.5%,冲淤分布由蓄水前“冲槽淤滩”转为“滩槽均冲”,不同蓄水阶段存在差异;③ 河槽冲刷过程中,上荆江及以上河段枯水位下降趋势趋缓,下荆江及以下河段下降速率增加,应采取防控措施遏制河道水位下降趋势;④ 枯水河槽冲刷是长江中下游航道水深提升的基础,枯水位降幅小于深槽下切深度,在河道和航道整治工程综合作用下航道尺度提升,提前5年实现了2020年航道尺度规划目标;⑤ 平滩水位以上河槽形态调整不大,在河床粗化、岸滩植被、人类活动等综合作用下河道综合阻力增加,出现了中洪水流量—高水位现象,应引起足够重视。三峡水库汛期调蓄作用可有效提升中下游洪水防御能力,但不排除遭遇支流洪水叠加效应,中下游洪水压力仍然较大。     

The relationship between water level change and river channel geometry adjustment in the downstream of the Three Gorges Dam

In this study, data measured from 1955-2016 were analysed to study the relationship between the water level and river channel geometry adjustment in the downstream of the Three Gorges Dam (TGD) after the impoundment of the dam. The results highlight the following facts: (1) for the same flow, the low water level decreased, flood water level changed little, lowest water level increased, and highest water level decreased at the hydrological stations in the downstream of the dam; (2) the distribution of erosion and deposition along the river channel changed from “erosion at channels and deposition at bankfulls” to “erosion at both channels and bankfulls;” the ratio of low-water channel erosion to bankfull channel erosion was 95.5% from October 2002 to October 2015, with variations between different impoundment stages; (3) the low water level decrease slowed down during the channel erosion in the Upper Jingjiang reach and reaches upstream but sped up in the Lower Jingjiang reach and reaches downstream; measures should be taken to prevent the decrease in the channel water level; (4) erosion was the basis for channel dimension upscaling in the middle reaches of the Yangtze River; the low water level decrease was smaller than the thalweg decline; both channel water depth and width increased under the combined effects of channel and waterway regulations; and (5) the geometry of the channels above bankfulls did not significantly change; however, the comprehensive channel resistance increased under the combined effects of riverbed coarsening, beach vegetation, and human activities; as a result, the flood water level increased markedly and moderate flood to high water level phenomena occurred, which should be considered. The Three Gorges Reservoir effectively enhances the flood defense capacity of the middle and lower reaches of the Yangtze River; however, the superposition effect of tributary floods cannot be ruled out.     

长江中游荆江河段同流量-水位演化特征及驱动成因

水库运行改变了坝下游水沙输移条件,在河道冲刷的同时,引起水位过程出现适应性调整.本文以长江中游荆江河段为对象,采用多项式拟合法,对比分析1991-2016年间分级流量一水位变化特征,采用基于河流动力学原理的分离变量法,识别河道冲淤、下游控制水位及河床综合糙率等变化对分级流量-水位变化的影响程度.研究表明:1991-20...     

EFFECT OF DAMS ON MOUNTAINOUS BEDROCK RIVERS

This study examines the adjustment of river systems in the Golan Heights to reservoir construction in small basaltic mountainous catchments where total water flow is impounded, and discusses comparisons with the effects of large dams on alluvial rivers. Annual rainfall ranges from 500 mm to 900 mm, and no major springs are found in the area. About 3/4 of total runoff is in the form of floods caused by rainstorms. The 11 dams receive drainage from about 20% of the total catchment, and a third of the total runoff. Changes in the river channels were studied at 28 field stations. Flood marks provided peak stage levels for largest season discharge, and 8 nearby hydrometric stations provided a continuous hydrological record. Bed material was sampled at each cross-section site. The main effect of river impoundment is a sharp decrease in flood peaks below the reservoirs to about one-third of their previous natural regime. The channel cross-sectional area decreased, but no temporal adjustment can be established, as most of the reservoirs were built in the last 5–8 years. Channel-flow hydraulics are competent enough to transport the suspended material, but evidence of aggradation was found in the channel reaches close to the dams. Bedload transport and the size of transported cobbles and boulders decreased downstream from the dams. Increased vegetation cover downstream from the dams was the most pronounced effect. Adjustment of the fluvial system to dam building in mountainous streams seems to be less sensitive than in alluvial channels. [Key words: fluvial geomorphology, dams, water reservoirs, environmental changes, Israel.]     

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.     

Downstream effects of reservoirs in areas suffering from water deficiency-the case of Hutuo River, China

l llltroductionIn North Che ~ of lack of water resources, moSt reservoir detain high poisons of both sediment andWater, so the oncoming Water in the POSt~ channel is severely reduced. Chalmel adjUStlnellt takes Placeunder the conditions of attenuated flow and sediment load. and the capedty Of the find conveyance Of thectal is ctrisot accodegh. hi the ~ or the ~o her, the ea~ty orfind convm ho bornerelatively lower air many you of chalmel adjUStment. Hence, the small fled, Which had been …     

Downstream effects of dams on livelihoods of river-dependent communities: the case of Ghana’s Kpong Dam

Construction of dams affects the livelihoods of the population living along the dammed river. There is a need for more studies to guide dam development policies and management to safeguard the livelihoods of local river users. This paper examines the effects of dams on the socio-economic livelihoods of downstream communities by drawing on the Kpong Dam in Ghana constructed from 1979 to 1982 with the goal of supplying energy and for irrigation purposes. Primary data were collected in resettled and non-resettled downstream communities using a mixed-research approach. This case study highlights how the Kpong Dam has affected the downstream river-dependent population whose livelihoods, particularly farming and fishing revolved around the seasonal flow regimes of the Volta River. Our study challenges the general perception that dams increase agricultural production by illustrating that developing ancillary facilities such as irrigation schemes as part of dam projects can enhance all-year-round agricultural production to improve food and income security of downstream households only when constraints such as lack of farm inputs are addressed. To safeguard livelihoods and limit the social impacts of dams, compensation schemes and alternative livelihood activities should be designed to include resettled and non-resettled communities along the downstream areas affected by dam projects.     

Channel morphology and its impact on flood passage, the Tianjiazhen reach of the middle Yangtze River

The Tianjiazhen reach of the middle Yangtze is about 8 km long, and characterized by a narrow river width of 650 m and local water depth of > 90 m in deep inner troughs, of which about 60 m is below the mean sea level. The troughs in the channel of such a large river are associated with regional tectonics and local lithology. The channel configuration plays a critical role in modifying the height and duration of river floods and erosion of the riverbed. The formation of the troughs in the bed of the Yangtze is considered to be controlled by sets of NW–SE-oriented neotectonic fault zones, in which some segments consist of highly folded thick Triassic limestone crossed by the Yangtze River. Several limestone hills, currently located next to the river channel, serve as nodes that create large vortices in the river, thereby accelerating downcutting on the riverbed composed of limestone highly susceptible to physical corrosion and chemical dissolution. Hydrological records indicate that the nodal hills and channel configuration at Tianjiazhen do not impact on normal flow discharges but discharges > 50,000 m³s^− 1 are slowed down for 2–3 days. Catastrophic floods are held up for even longer periods. These inevitably result in elevated flood stages upstream of prolonged duration, affecting large cities such as Wuhan and a very large number of people.     

滦河下游河道及三角洲地貌的近期演化

自20世纪80年代滦河上中游大型水库的修建以及下游农业用水量的激增,滦河下游水沙锐减。至桃林口水库修建后,滦河入海水量减至5.96亿m³/a,下泻泥沙减至2.43万t/a,滦河断流趋势日益严重。本文选择1979年至2007年多期遥感影像,探讨在大规模水资源开发影响下滦河下游河道及三角洲地貌的演化。结果表明:20世纪90年代以后滦河下游水沙量的大幅减少直接导致下游河道萎缩。由于上游水库的拦截以及下游河道搬运能力下降,入海泥沙量大幅减少几至断绝,致使滦河三角洲主汊道1984年改道后并未发育形成新的三角洲叶瓣,入海汊道由多汊萎缩为单汊,三角洲逐渐转入全面侵蚀阶段。     

Quantitative relationship between channels and bars in a tidal reach of the lower Yangtze River: Implications for river management

Deep-water navigation channels in the tidal reaches of the lower Yangtze River are affected by water and sediment fluxes that produce complex shoals and unstable channel conditions. The Fujiangsha reach is particularly difficult to manage, as it has many braided channels within the tidal fluctuation zone. In this study, hydrologic and topographic data from the Fujiangsha reach from 2012 to 2017 were used to examine the variations in deposition and erosion, flow diversion, shoals, and channel conditions. Since the Three Gorges Dam became operational and water storage was initiated, the Fujiangsha reach has shown an overall tendency toward erosion. Channels deeper than 10 m accounted for 83.7% of the total erosion of the Fujiangsha reach during 2012–2017. Moreover, the dominant channel-forming sediments have gradually changed from suspended sediments to a mixed load of suspended and bed-load sediments. Deposition volumes of these sediments has varied significantly among different channels, but has mainly occurred in the Fubei channel. Furthermore, periodic variations in the Jingjiang point bar have followed a deposition-erosion-deposition pattern, and the downstream Shuangjian shoal mid-channel bar has been scoured and shortened. Approximately 44.0% of the bed load from the upstream Fujiangsha reach is deposited within the 12.5-m deep Fubei channel. The increased erosion and river flow from the Jingjiang point bar and the Shuangjian shoal during the flood season constituted 59.3% and 40.7%, respectively, of the total amount of siltation in the Fubei channel.     

黄河游荡河段河床形态调整对洪水过程的响应

以黄河流域1950～1985年200余场洪水资料为基础，并增加了最近的实验资料，分析了黄河下游游荡河段不同含沙量沙水过程中河床形态的调整过程，结果表明，由洪水过程所导致的河床形态变化是相当剧烈的。且与含沙量密切相关，表现出非线性的变化规律，当含沙量较小时，随含沙量的增大，洪水后河床宽深比增大，当含沙量增大到一定程度后再增大时，宽深比随含沙量的增大而减小，这一结果为修正Schumm关于河床形态变化的定性预测关系提供了新的依据。     

汉江丹江口水库下游河床演变

丹江口水库建库20多年来,下游河道由堆积性河道变成了冲刷性的河道,河床物质沿程粗化,比降得以调平。水深增加幅度大于河宽,流速并不随着水深增加而加快。深槽、浅滩分布明显化,宽深比不断在减少。整个库下游变化可分为三段:1)近库段,游荡河道向单一限制性曲流转化;2)大支流影响段,河道仍保持着游荡特性;3)下游段,游荡段游荡特性减弱,弯曲段则深蚀作用加强。     

长江中下游河床沉积物分布特征

对长江中下游武汉至河口段304处河床沉积物样品进行了粒度测量与分析,通过各参数间的模拟、统计及对比,探讨了沉积物粒度、水动力因素及河床地貌三者间的关系。研究结果表明：本区河床沉积物以中、细砂为主,床底搬运十分微弱,河道相对稳定;从上至下沿程有明显的“粗-细-粗-细”粒径变化,主要反映河流动力地貌、动力沉积特征;粒径在河床的沿程分布总体为北粗南细,说明北岸侵蚀,南岸淤积的特点。研究同时也表明,颗粒因河型不同而迥异;颗粒偏态度-峭度在不同河型中表现各异,对区分顺直微弯分汊和鹅头形分汊河道尤为显著。     

河道糙率系数变化对全新世古洪水流量计算的影响研究

洪水流量计算中河道糙率是一个重要的灵敏度参数。以汉江上游郧县尚家河台地前沿记录的四期古洪水流量计算为例,研究河道糙率系数在比降-面积法和HEC-RAS模型中对古洪水流量计算结果的影响。结果表明：其他水文参数一定时,河道糙率系数以±15%变幅,比降-面积法重建的古洪水流量变幅在-13.04%～17.65%,HEC-RAS模型计算的流量变幅在-4.32%～4.57%;若河道糙率系数以±25%变幅,比降-面积法和HEC-RAS模型计算的流量变幅分别为-20%～33.33%和-7.79%～9.18%,说明采用HEC-RAS模型重建古洪水流量,可减少河道糙率系数对计算结果的影响,使古洪水流量计算结果更为可靠。此外,假定其他参数不变,主河槽和左、右岸糙率系数依次变幅±25%,主河槽糙率系数变化对流量计算结果影响最大,说明洪水流量计算时应准确选取主河槽的糙率系数。该结果对水利工程建设具有重要的现实意义。     

Age and hydrological significance of lichen limits on sandstone river channels near Sydney,Australia

Trimmed lichen communities (lichen limits) are abrupt changes from a lichen community to a scoured bare rock surface and have been used to determine bankfull channel capacity on bedrock channels and their response to the combined disturbances of flow regulation and climate change. They can also be used to set flushing flows in bedrock channels. In sandstone gorges of the Nepean River, Australia, the crustose lichen, Lecidea terrena Nyl, was common at both gorge and cemetery (sandstone headstones) sites, enabling construction of growth curves for above and below dam areas. Growth curves were used to date lichen colonisation of sandstone surfaces in rivers. The oldest, highest lichen limit at all sites represented the pre‐flow regulation lichen community because its characteristics above and below Nepean Dam were similar and were trimmed to a level that produced consistent discharges across a range of catchment areas. They corresponded to return periods of less than 2 years on the annual maximum series and was developed during the flood‐dominated regime (FDR) of 1857–1900. Lichen limits form by the phycobiont dominating the mycobiont and hence degrading lichen thalli due to water inundation causing weak or dead thalli to be scrubbed from the rock surface. Trimming to the unregulated lichen limit represents a small flood of frequent occurrence appropriate for flushing bedrock channels. A lower lichen limit was only found below a diversion weir and was formed by frequent dam spills between 1950 and 1952 during an extraordinary wet period at the start of the FDR between 1949 and 1990. Lichens colonised exposed sandstone between the level of frequent flows from 1949 to 1952, and the high lichen limit. On the Avon River, an additional lower limit reflected a massive downward shift in flow duration following the start of interbasin diversions to Wollongong in 1962.     

Downstream hydrologic and geomorphic effects of large dams on American rivers

The hydrology and geomorphology of large rivers in America reflect the pervasive influence of an extensive water control infrastructure including more than 75,000 dams. One hundred thirty-seven of the very large dams, each storing 1.2 km³ (10⁶ acre feet) of water or more, alter the flows of every large river in the country. The hydrologic effects of these very large dams emerge from an analysis of the stream gage records of 72 river reaches organized into 36 pairs. One member of each pair is an unregulated reach above a dam, whereas the other is a regulated reach downstream from the same structure. Comparison of the regulated and unregulated reaches shows that very large dams, on average, reduce annual peak discharges 67% (in some individual cases up to 90%), decrease the ratio of annual maximum/mean flow 60%, decrease the range of daily discharges 64%, increase the number of reversals in discharge by 34%, and reduce the daily rates of ramping as much as 60%. Dams alter the timing of high and low flows and change the timing of the yearly maximum and minimum flows, in some cases by as much as half a year. Regional variation in rivers, dams, and responses are substantial: rivers in the Great Plains and Ozark/Ouachita regions have annual maximum/mean flow ratios that are 7 times greater than ratios for rivers in the Pacific Northwest. At the same time, the ratio of storage capacity/mean annual water yield for dams is greatest for Interior Western, Ozark/Ouachita and Great Plains rivers and least for Pacific Northwest streams. Thus, in many cases those rivers with the highest annual variability have the greatest potential impact from dams because structures can exert substantial control over downstream hydrology. The hydrologic changes by dams have fostered dramatic geomorphic differences between regulated and unregulated reaches. When compared to similar unregulated reaches, regulated reaches have 32% larger low flow channels, 50% smaller high flow channels, 79% less active flood plain area, and 3.6 times more inactive flood plain area. Dams also affect the area of active areas, the functional surfaces that are functionally connected to the present regime of the river. Regulated reaches have active areas that are 72 smaller than the active areas of similar unregulated reaches. The geomorphic complexity (number of separate functional surfaces per unit of channel length) is 37% less in regulated reaches. Reductions in the size of hydrologically active functional surfaces are greatest in rivers in the Great Plains and least in Eastern streams. The largest differences in geomorphic complexity are in interior western rivers. The shrunken, simplified geomorphology of regulated large rivers has had direct effects on riparian ecology, producing spatially smaller, less diverse riparian ecosystems compared to the larger, more complex ecosystems along unregulated reaches of rivers.     

Computational fluid dynamics and the physical modelling of an upland urban river

This paper describes the application of a commercially available, three-dimensional computational fluid dynamic (CFD) model to simulate the flow structure in an upland river that is prone to flooding. Simulations use a rectangular channel geometry, smooth sidewalls and a bed topography obtained from the field site that contains a subdued pool–riffle sequence. The CFD model uses the RNG κ– turbulence closure scheme of Yakhot and Orszag (J. Sci. Comput. 1 (1986) 1), as implemented in FLUENT 4.4.4, with a free surface. Results are shown for numerical runs simulating a 1:100 year return interval flood. Output from the numerical model is compared to a physical model experiment that uses a 1:35 scale fibreglass mould of the field study reach and measures velocity using ultrasonic Doppler velocity profiling (UDVP). Results are presented from the numerical and flume models for the water surface and streamwise velocity pattern and for the secondary flows simulated in the numerical model. A good agreement is achieved between the CFD model output and the physical model results for the downstream velocities.Results suggest that the streamwise velocity is the main influence on the flow structure at the discharge and channel configuration studied. Secondary flows are, in general, very weak being below the resolution of measurement in the physical model and less than 10% of the streamwise velocity in the numerical model. Consequently, there is no evidence for a ‘velocity dip’. It is suggested that the subdued topography or inlet morphology may inhibit the development of secondary flows that have been recorded in previous flat-bed, rectangular open channel flows. A significant corollary of these results is that the morphological evolution of the pool–riffle sequence at high discharges may be controlled primarily by the downstream distribution of velocity and sediment transport with little role for lateral sorting and sediment routing by secondary flows. This paper also raises a number of issues that may be of use in future CFD modelling of three-dimensional flow in open channels within the geomorphological community.     

试论黄河下游北岸可能决口地段及其最大淹没范围

鉴于黄河的现状,作者认为黄河决口的潜在危险越来越大。推断北岸决口的可能性为大。根据溃坝原理,采用水力学方法对北岸决口的最大淹没范围作了模拟。指出若从沁河口—原阳段决堤,淹没面积约2.21万平方公里,从原阳—高村段决堤,则约为2.12万平方公里。     

HYDROLOGY AND GEOMORPHIC EFFECTS OF A HIGH-MAGNITUDE FLOOD IN AN ALPINE RIVER

The catchment of the River Partnach, a torrent situated in a glacial valley in the Northern Calcareous Alps of Bavaria/Germany, was affected by a high‐magnitude flood on 22/23 August 2005 with a peak discharge of more than 16 m³s^‐1 at the spring and about 50 m³s^‐1 at the catchment outlet. This flood was caused by a long period of intense rainfall with a maximum intensity of 230 mm per day. During this event, a landslide dam, which previously held a small lake, failed. The flood wave originating from the dam breach transported a large volume of sediment (more than 50 000 m³) derived from bank erosion and the massive undercutting of a talus cone. This caused a fundamental transformation of the downstream channel system including the redistribution of large woody debris and channel switching. Using terrestrial survey and aerial photography, erosional and depositional consequences of the event were mapped, pre‐ and post‐event surfaces were compared and the sediment budget of the event calculated for ten consecutive channel reaches downstream of the former lake. According to the calculations more than 100 000 tonnes of sediment were eroded, 75% of which was redeposited within the channel and the proximal floodplain. A previous large flood which occurred a few weeks prior to the August 2005 event had a significant effect on controlling the impact of this event.     

基于RS和GIS的城市化进程中河道时空演变分析——以深圳市布吉河为例

为研究城市化对城市河道的影响,论文选择处于粤港澳大湾区的典型高度城市化流域布吉河流域为研究区,基于1988-2015年10期Landsat系列遥感影像、2003-2017年9期Google Earth高分辨率遥感影像、2019年深圳市水系图以及1980年以来的河道整治相关文献,应用RS和GIS技术,构建城市河道演变特征...