中国的水库泥沙淤积问题

由于我国有许多河流是含沙最高、输沙量大的多泥沙河流,水库泥沙淤积问题异常严重．主要表现在：淤积数量大,淤积速率快．据统计,截止到1981年底全国水库总淤积量达115×10~8m~3．占统计水库总库容的14．2％．年平均库容损失率达2．3％,高于世界各国．水库的严重淤积,不仅影响水库兴利效益的发挥,严重威胁水库的使用寿命,而且还造成一系列在进行水库规划时未曾充分估计到的环境问题．本文重点从河流水文泥沙特性、我国水库淤积问题的严重性、水库淤积引起的问题及水库防淤减淤措施等4个方面作一较全面的分析和探讨．     

阿斯旺水库

1958年埃-苏两国签定了关于苏联帮助埃及建设阿斯旺高坝的协定,1965年动工,1971年建成.坝高111m,长4200m,拦水形成纳赛尔湖——阿斯旺水库.湖周长500km,平均深度35m,最大水深97m,一般水域面积5120km~2,最大水面6116km~2,一般容积1570×10~8m~3,最大库容1640×10~8m~3.高坝建成后,安装了12台17.5×10~4kW发电机组,水力发电量达210×10~4KW;其二,调节迳流,保证灌溉用水,实现了洪季不涝、枯季不旱,各个生长季节都能得到充分、均衡的     

近20年来三峡水库泥沙淤积及其对库区的影响

泥沙问题是三峡工程建设与运行中的关键技术问题之一,只有妥善处理好泥沙问题,才能保证三峡工程长期有效使用,维持水库功能的全面发挥。本文首先结合实测水文、河道地形观测资料,对三峡水库运行近20年来的泥沙淤积特性及水库排沙比进行了较为全面的分析研究,并与已有研究成果进行了对比;其次,围绕防洪、航运以及坝前段的泥沙淤积等方面,进一步分析了水库淤积产生的影响。结果表明:三峡水库蓄水以来,在不考虑区间来沙的情况下,三峡水库共淤积泥沙20.484亿t,近似年均淤积1.102亿t,水库排沙比为23.6%,水库年均淤积量为原论证预测值的33%。其中,库区干流段累计淤积泥沙17.835亿m³(变动回水区冲刷0.694亿m³;常年回水区淤积18.529亿m³),淤积在水库防洪库容内的泥沙为1.648亿m³(干、支流分别淤积1.517亿m³和0.131亿m³),占水库防洪库容的0.74%,“十一五”攻关阶段研究得出的多年平均淤积量及排沙比较实测值均偏大,变动回水区冲淤则出现反向的...     

封面——三峡水库专辑

三峡水库,位于长江中游,是三峡工程建成后蓄水形成的人工湖泊,面积1084km^2,是我国最大的水库。2003年开始蓄水,175m正常蓄水位高程时,水库总库容为393×10^8m^3（摄影：黄正平）。     

长江葛洲坝水库溪口滩的演变及其对航道的影响

葛洲坝水库位于长江三峡,库容15.8×10~8m~3,水库长度188.1km,其中变动回水段占66％。溪口潍主要由粒径大于20mm的卵石推移质组成。葛洲坝库区的卵石推移质有65％来源于灰岩为主补给区,该补给区卵石推移质数量大,颗粒粗,易成滩,所以库区溪口滩有92％分布在以灰岩为主的补给区。葛洲坝库区溪口滩可分洪水急流滩、洪中水急流滩、中水急流滩、中枯水急流滩与枯水急流潍等5种类型,建库后库区回水变动段占总数50％的溪口滩得到改善。但是占总数50％的位于库尾段的溪口滩与变动回水段洪水急流滩溪口滩,未能得到改善。随着这些溪口滩得到卵石推移质补给,航道将会恶化。在三峡水库建成前应加强对溪口滩的观测、研究与整治。     

大纵湖开发利用的几点建议

大纵湖地处江苏省里下河地区的腹部,在盐城、兴化两市之间,湖形略近椭圆,东西长6km,南北宽5.5km,面积28km~2,为里下河地区之最大湖泊。湖盆浅碟形,湖底甚平坦,高程一般在0.1—0.3m。该湖主要承受郭正湖、蜈蚣湖和得胜湖三个小型湖荡地区的来水,经由南部的鲤鱼河、中引河等入湖。排水河道主要为东北部的蟒蛇河及东部的兴盐界河。以多年平均水位1.42m计,平均水深1m,蓄水量0.285×10~8m~3;汛期平均水深1.8m,蓄水量0.501×10~8m~3,枯水期平均水深0.5m,蓄水量0.14×10~8m~3。具蓄洪、灌溉之利。     

金沙江下游梯级水库泥沙淤积和坝下河道冲刷规律

金沙江下游4个梯级水电站总装机容量相当于两座三峡水库,是“西电东送”中部地区的源头工程,工程效益发挥对经济社会发展意义重大。2012年以来,向家坝、溪洛渡、乌东德和白鹤滩电站等陆续蓄水运行,层层拦截金沙江的泥沙,2013—2020年向家坝出库年输沙量均值下降至152万t,减幅超过99%。大量泥沙淤积在梯级水库内,同时向家坝以下河道发生长距离冲刷。本文以自金沙江下游工程筹建以来的观测资料为基础,针对梯级水库的泥沙淤积和坝下游河道冲刷规律开展研究,结果表明:金沙江下游四个梯级电站自建成运行至2020年底,累计淤积泥沙约5.98亿m³,其中溪洛渡库区淤积量占比达92.5%,2013-2020年溪洛渡和向家坝水库排沙比分别为2.64%和22.2%,其水库泥沙主要淤积在常年回水区的干流河道内,以死库容内淤积为主,侵占有效库容的比例小于1.3%。金沙江下游库区干流河道的峡谷特征明显,淤积多表现为主河槽的平铺式淤高。溪洛渡和向家坝库区淤积的泥沙沿程分选特征明显,越靠近坝前,中数粒径减小、细颗粒泥沙沙量百分数增加,极细颗粒泥沙会在库区一定范围内大量沉积。向家坝下游河床普遍冲刷,但...     

鄱阳湖简介

鄱阳湖(115°49′E—116°46′E、28°24′N—29°46′N)纳赣江、抚河、信江、饶河、修河五河来水。经湖口注入长江,是一个过水性吞吐型湖泊。流域面积162225km~2,湖面积和容积高水时分别为3210km~2和252×10~8m~3,低水时分别是146km~2和4.5×10~8m~3,高水呈湖相,低水呈河相,有“洪水汪洋一大片,枯水漫长一条线”的自然地理景观。平均宽度16.9km,最宽处70km,最窄处仅3km,最大长度173km,平均水深8.4m。     

长江流域水库"过滤器效应"对入海溶解硅通量的影响

根据1960-2000年间长江大通水文站记录的水、沙以及硅、氮、磷等数据,结合1954-2006年间长江流域库容大于10⁸ m³的162座水库的库容、上游径流量、总磷等数据,利用Vollenweider模型分析了水库"过滤器效应"对入海溶解硅(DSi)通量的影响.结果表明:1)1990s相比1960s,长江入海DSi通量下降了约1.85×10⁶ t/a,减少了大约25.3%;入海DSi通量的下降与流域径流波动、入海悬沙通量下降以及溶解无机氮通量的增加紧密相关.2)流域水库明显改变径流的自然过程,增加径流的滞留时间,流域90%以上的水库对上游径流的滞留时间超过0.05年,水库产生显著的DSi"生物过滤器"效应.模型计算显示流域大型水库对DSi的累计滞留量可达0.85×10⁶ t/a,占年均入海DSi通量(1990-2000年)5.4×10⁶ t的15.7%,是入海DSi通量减少量(1.85×10⁶ t/a)的45.9%.3)根据保守估计,流域162座大型水库内泥沙累计淤积量达6.75×10⁸ t/a,不仅使悬沙入海通量显著下降,而且造成大量颗粒吸附的外源和内源DSi颗粒沉淀,这对入海DSi通量减少也起到重要贡献.但目前对水库"泥沙过滤器"的滞留机理并不清楚,需要展开进一步的研究.     

太湖的泥沙与演变

历史时期,太湖是不断扩展的,其平均扩展速率为0.37km~2/a。据沙量平衡分析与计算表明。因湖岸崩塌和太湖水系的输沙作用,近期太湖的泥沙淤积量为9.28×10~5t/a.泥沙数量虽然不大,但经过长期的积累,对太湖演变具有深刻影响。就自然演变趋势而言,近期太湖面积仍以0.168km~2/a的速率扩大,容积则以3.95×10~5m~3/a的速率减小,太湖正进一步向浅平方向演变。然而,因围湖造田,建国以来,太湖的面积则以4.58km~2/a的速率在减小。     

丹江口水库的饵料生物资源及水体营养状态评价

根据1992年12月至1993年9月的调查,丹江口水库的饵料生物资源量为1．845×10~6t．其产鱼潜力为1．615×10~4t．是现有鱼产量（包括捕捞产量和不投饵网箱产量）的5倍左右．就水体营养状态而言,汉江库区为中营养型,丹江库区属贫一中营养型．文中还对丹江口水库的渔业发展和水质保护进行了讨论．     

Bed material transport estimate in large gravel‐bed rivers using the virtual velocity approach

This paper reports on a first attempt of using the virtual velocity approach to assess sediment mobility and transport in two wide and complex gravel‐bed rivers of northern Italy. Displacement length and virtual velocity of spray‐painted tracers were measured in the field. Also, the thickness of the sediment active layer during floods was measured using scour chains and post‐flood morphological changes as documented by repeated survey of channel cross‐sections. The effects of eight and seven floods were studied on the Tagliamento and Brenta Rivers, where 259 and 277 spray‐painted areas were surveyed, respectively. In the Tagliamento River 36% of the spray‐painted areas experienced partial transport, whereas in the Brenta River this accounted for 20%. Whereas, full removal/gravel deposition was observed on 37% and 26% of these areas on the Tagliamento and Brenta Rivers, respectively. The mean displacement length of particles, the thickness of the active layer and the extent of partial transport are well correlated with the dimensionless shear stress. The virtual velocity approach allowed calculation of bed material transport over a wide range of flood magnitudes. Annual coarse sediment transport was calculated up to 150 for the Tagliamento, and 30 × 10³  m³ yr^?1 for the Brenta. The outcomes of this work highlight the relevance of partial transport condition, as it could represent more than 70% of the total bed material transported during low‐magnitude floods, and up to 40% for near‐bankfull events. Results confirm that bed material load tends to be overestimated by traditional formulas. Copyright © 2016 John Wiley & Sons, Ltd.     

Deposition and resuspension of fine particles in a riverine ‘dead zone’

Particulate matter suspended in the River Severn (Shropshire, UK) consists chiefly of clay-sized mineral particles, together with living and dead micro-organisms (algae and bacteria). Its concentration depends strongly on discharge, but the particle size distribution shows no systematic variability. For most samples, the particle volume is log-normally distributed with respect to diameter, the mean diameter being ca. 9 μm. The particles are mainly aggregates, including some with linear dimensions of the order of tens or hundreds of micrometres. Particle density depends appreciably on size, decreasing from ca. 2.5 × 10⁶ g m^?3 at a diameter of 2.5 μm to ca. 1.3 × 10⁶ g m ^?3 at 20 μm. The collision efficiency factor for particle aggregation is estimated to be 0.01–0.03. At low discharge, the ‘dead zone’ in the River Severn at Leighton is a well defined region of stagnant water behind a gravel bar. The rate of deposition of fine particles on its bed is of the order of tens of grams per square metre per day. Resuspension requires a critical bed shear velocity of 0.03–0.04 m s^?1, which occurs at main river discharges greater than about 150 m³ s^?1. Under such conditions the gravel bar is underwater and the dead zone is a region of highly turbulent return flow. A simple mechanistic model of particle dynamics in the dead zone accounts reasonably well for particle accumulation rates when run with parameter values based on measured particle and hydraulic properties. Calculations with the model suggest that most of the sedimentation flux to the dead zone bed is due to particles with equivalent sphere diameters in the range 30–240 μm. Simulations indicate that deposition proceeded continuously during spring and summer, whereas repeated deposition and resuspension occurred in autumn and winter.     

Restoration of spawning grounds for trout and grayling in the river High-Rhine

In January 1990 10 m³ of washed gravel (grain size 16–50 mm) were introduced in an impounded section of the River High-Rhine to test its potential as a spawning ground for salmonids. The process of infiltration of fine sediments into the gravel and subsequent clogging was monitored for three years. Levels of clogging of the gravel matrix were estimated and ranged from slight to moderately-heavy. The degree of clogging was lower in winter than in summer. Since no bedload transport was observed during the study period, flood events could wash out sediments from the top layer of the gravel bed only. An equilibrium diffusion technique using porewater samplers was employed to measure oxygen concentrations within the interstitial space during the spawning period ofThymallus thymallus (April),Salmo trutta fario andOncorhynchus mykiss (December till February). Oxygen concentration decreased with increasing depth and during the course of the study period. Oxygen concentrations measured as a reference in the interstitial of the confluence of the river Glatt were considerably lower than those of the new gravel bed. A wide range of O₂ concentrations was found in winter 1991/92 and in spring 1992. This could be explained by the heterogeneous microstructure of the substrate. Successful embryonic and larval development of grayling in the gravel bed was observed in spring 1991 and 1992. However, no eggs or larvae of brown trout or rainbow trout were found. Habitat restoration projects for salmonids in impoundments of the High-Rhine are critically discussed.     

Geomorphological effects of catastrophic flooding on a small subtropical Estuary

The Mgeni Estuary is situated on the east coast of South Africa. Tidal salinity changes commonly extend 2.5 km upstream from the mouth. The subtropical climatic regime causes seasonal flooding, the geomorphological effects of which are increased by a steep river gradient. A 120-150 year flood event during September 1987, with an estimated peak discharge of 10800 cumecs, resulted in the erosion of 1.86 × 10⁶ m³ of sediment from the estuary. The normal high tide volume of the estuary (0.35 × 10⁶ m³) increased to 1.85 × 10⁶ m³ after the flood. The post-flood intertidal volume (tidal prism) of the estuary was 0.43 × 10⁶ m³ compared to 0.19 × 10⁶ m³ before the event. The nature and extent of erosion in the estuary was controlled by the composition of the estuary banks and bed material. Gravel and sand substrates were preferentially eroded from the estuary bed before the cohesive bank materials were undercut in sections of the estuary. Mud and fine sand were deposited on overbank areas when the flood waned and a lag of coarse sand and gravel was produced on the estuary bed. Approximately 46 per cent of the bedload sediment supplied to the estuary since 1917 was retained in the estuary until the 1987 flood. The remainder was transported through the system and into the Indian Ocean. Results show that catastrophic floods play an important role in sedimentation in small estuaries.     

Gravel excavation and geomorphic evolution of the mining affected river in the upstream reach of the Yangtze River,China

As economic development upstream in the Yangtze River basin has progressed in recent decades,the demand for sediment has rapidly increased and contributed to an expansion in sediment excavation that may affect the river’s stability and navigation safety.In the current study,the distribution of gravel mining in the upstream reach of the Yangtze River was investigated using field measurements obtained from2008 to 2017.An experimental investigation was then done to analyze the bed load behavior in ...     

Long-term variations in the second sectorial Stokes harmonics on the basis of TOPEX/POSEIDON altimetry between 1993 and 2000

The long-term variations in the second degree sectorial Stokes parameters of the geopotential have been determined from TOPEX-POSEIDON (T/P) satellite altimeter data, covering the period of January 1, 1993 to January 3, 2001 (T/P cycles 11-305). It is the first attempt to determine the variations in the second sectorial harmonics in the Earth’s inertia tensor due to the ocean dynamics. The variations amount to about 1 × 10⁻¹⁰ (J ₂ ⁽²⁾ ≈ 1.6 × 10⁻⁶ and S ₂ ⁽²⁾ ≈ −0.9 × 10⁻⁶). The variations are about 5% of the tidal effect. This corresponds to variations in the directions of the equatorial axes of the Earth’s inertia ellipsoid of up to 10 arc-seconds. Consequently, the annual and semi-annual variations of the Earth’s equatorial flattening is about 10⁻⁹; i.e. it corresponds to a change of 8 units of its denominator of 91 030. (The equatorial flattening ≈ 1/91 030). Since the coverage of the Earth’s ocean surface is not worldwide, and the inclination of T/P is i = 66°, it is only 58.2% (min. depth of the ocean 2 000 m) of the Earth’s surface which is processed, the torque, resulting from the seasonal transfer of masses within a sea surface layer, is not zero. It amounts up to 10¹⁶ kg m²s⁻², which is comparable to the total indirect tidal torque due to the Moon and the Sun, ∼ 3.9 × 10¹⁶ kg m²s⁻². However, the above estimate strongly depends on the adopted thickness of the sea surface layer, ΔR = 50 m. For a larger thickness of ΔR = 100 m, the seasonal torque amounts to about ∼ 2.3 × 10¹⁶ kg m²s⁻².     

115 years of sediment deposition in a reservoir in Central Europe: Topographic change detection

Reservoirs have become an important component in the worldwide river sediment flux. Reservoirs prevent downstream sediment transport and have become a major sediment sink. In this study, sediment deposition during the last 115 years in the Urft Reservoir in western Germany is reconstructed. The Urft Reservoir is the oldest reservoir in the Eifel Mountains and was almost completely drained in 2020. This enabled a detailed mapping of the lake bottom using an unmanned aerial system and the computation of a high-resolution digital surface model. Topographic maps with a nominal resolution of 1:1000 from the time prior to the construction of the dam (around 1900) were used to construct a pre-reservoir elevation model. A digital elevation model of difference (DoD) was calculated from these two datasets for the reservoir floor (0.72 km²). Based on the DoD, a net sediment accumulation of 1.16 × 10⁶ m³ was calculated alongside a propagated volume error of 6.91 × 10⁵ m³, resulting in a mean accumulation of 1.54 m. Conservative vertical error propagation results in an average level of detection (LoD) of 1.8 m. In contrast, the comparison of the DoD with 47 cores in the upper part of the reservoir showed a mean difference of −0.11 m, indicating a high, independently assessed accuracy of the DoD. Three depositional hotspots were identified in the reservoir. One is close to the Urft dam where very fine sediments are draped across the pre-reservoir topography. Two areas are related to reservoir management. Sediment deposition in the Urft Reservoir has been comparably low in comparison to other regions globally, resulting in a 3.25% ± 1.93% loss of reservoir volume between 1905 and 2020. To analyse the effect of strong flooding events, a subset of the reservoir was analysed after an extreme event in July 2021, but accumulation did almost entirely not exceed the LoD.