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1.
长江口南支河段盐水入侵规律的研究 总被引：20，自引：0，他引：20
依据实测资料分析和数学模型计算分析了上游径流、外海潮流以及河势变化对长江口南支河段盐水入侵的，同时着重研究了长江口北支以及南支下游的南、北港三个盐水入侵源对南支河段盐水入侵的影响。研究表明：徐六泾水域基本不受盐水入侵的影响；浏河口以上主要为北支倒灌盐水所控制；钱泾、七丫口河段受北支倒灌的影响；宝钢水域受到三个人入侵源的共同影响，其含氯度峰值一般发生在中、小潮期，主要取决于北支倒灌南支的过境盐水。综 相似文献
2.
基于2006年汛期10月长江干流大通水文站逐时水位流量资料和长江口区现场实测水文、盐度资料,探讨了特枯水文年份在大型水利枢纽调控影响下的长江口区汛期盐水入侵及其对淡水资源的影响。结果表明:①2006年汛期10月大潮期间,外海上溯至北支的咸潮强度较大,倒灌南支严重,导致观测期间陈行水库、宝钢水库河段不存在淡水资源;②北支高盐度的咸水倒灌主要经白茆沙北水道而进入南支,长江入海冲淡水则主要由白茆沙南水道下泄入南支,两股不同性质的水流在白茆沙尾部汇合,其影响范围可到南港吴淞口;③观测期间,外海高盐水团经南北槽上溯,其强度和上溯距离可影响到吴淞口,致使除吴淞口附近水域存在淡水资源外,南港吴淞口以下河段皆为高盐水体覆盖。 相似文献
3.
为研究磨刀门水道咸潮上溯的动力特性,基于非结构网格海洋模型（Finite Volume Coastal Ocean Model,FVCOM）,构建了覆盖珠江河口及其上游网河区的高分辨率三维斜压数值模型,采用实测资料对其进行率定和验证,并开展了咸潮上溯的数值模拟计算。根据计算结果和实测资料,对磨刀门水道大、中、小潮期间的盐淡水分层与混合特征、盐分物质的分层输移机制进行分析,探讨其咸潮上溯强度时空分布差异的原因。结果表明:小潮期,底层累积盐通量明显大于表层,净输移方向为陆向;大潮期,表层累积盐通量明显大于底层,净输移方向为海向;而平衡点一般出现于中潮期,这就是磨刀门水道咸潮上溯最强和最弱时刻分别出现于小潮和大潮后的中潮期的原因所在。 相似文献
4.
杭州城市供水85%取自钱塘江河口段,取水水质在枯水大潮期都不同程度地受到盐水入侵的威胁,分析钱塘江河口盐水入侵时空变化及研制二维数值预测模型对保障城市供水安全十分必要。根据钱塘江河口段实测水文氯度资料,分析了强潮作用下盐水入侵的时空变化特征;据此构建考虑斜压作用的二维水流、盐度输移的耦合数学模型,计算格式采用守恒性较好的有限体积法;在模型验证的基础上,数值分析了径流和潮汐对钱塘江河口段盐水入侵的影响,结果表明河口段的盐水入侵明显地受径流和潮汐的影响,据此可通过增大上游新安江水库的下泄流量抑制盐水入侵上溯以减小取水口氯度及超标时间,确保用水安全。 相似文献
5.
基于MIKE3研究扰动底层盐水楔实现抑制咸潮上溯的最优化方案。结果表明,在河道底部喷水扰动盐水楔可以有效减弱底层盐水浓度,且存在最优喷水流量与最优喷水点。当喷水流量小于该值时,咸潮上溯距离随流量的增大而减小,当大于该值时,咸潮上溯距离随流量的增大反而会增大;最优喷水流量从小潮到大潮逐渐增加,且随着径流量的增大而减小,如径流量为500 m/s~3时,小、中、大潮期间的最优喷水流量分别为20 m/s~3、20 m/s~3和25 m/s~3,减少的咸潮上溯距离分别为3.82 km、3.40 km和1.18 km。随着径流量增大,取得最佳抑咸效果的最优喷水点位置逐渐向下游移动。针对珠江河口的特殊径潮环境,盐水楔扰动的抑咸效果在小潮和中潮期间较好,在大潮期间相对较差。 相似文献
6.
为研究三峡蓄水后滞流点的时空变化规律,应用ECOMSED模型模拟长江河口在不同径流、潮流作用下的水流动态过程。结果表明:北支大洪水期下移幅度大,涨潮动力强劲,随潮流变化大;南侧变化幅度整体较北支小,随径流的变化幅度自大至小依次为北港、南槽、北槽;随潮流的变化幅度自大至小依次为南槽、北港、北槽。滞流点随径、潮条件变化时,受地形影响明显,三峡蓄水后,径流变化范围缩小,引起不同地貌单元滞流点范围不同程度的缩小,可据此认为,与滞流点位置一致的最大浑浊带范围呈现减小的趋势,由此可能引起最大浑浊带和地貌调整。 相似文献
7.
王承书 《沉积与特提斯地质》1990,10(6):61-68
《沉积学》36卷5期 1988年10月一、澳大利亚北部南Alligator河大潮河口湾和泛滥平原沉积模式澳大利亚北部地区南Alligator河有一大潮河口湾,潮汐影响(河口处大潮差为5—6m)沿河道向上达105km。在潮湿季节(12月—4月)以淡水为主,靠近河口有一盐水楔,在整个干旱季节混合成为盐水。潮道可划分为四种不同的类型:河口湾漏斗、蛇曲河段、尖形曲流河段(尖形于河曲内侧)和上游潮道。河口湾两侧泛滥平原上每一级陆地内,按地 相似文献
8.
为了解三峡水库的运行对长江河口北支咸潮倒灌的影响,对三峡水库初步运行前后北支咸潮倒灌的变化进行了分析.结果表明:三峡水库运行后,受水库下泄水量变化影响,北支咸潮倒灌时间提前,10~11月咸潮倒灌强度增加,12月至次年4月倒灌强度减弱,咸潮倒灌强度的降幅小于增幅;在咸潮倒灌最为严重和长江口淡水利用最为重要的1~4月,水库的实际运行所引起的北支咸潮倒灌减弱的幅度并不大;三峡水库的实际运行使得北支咸潮倒灌的强度在各月重新分配,但对一年中整个咸潮期咸潮倒灌的总强度影响不大;水库运行后,北支极端咸潮倒灌的强度降低,这对提高长江口水源地的供水安全及保证率有利. 相似文献
9.
采用物理模型实验方法对不同潮差驱动下咸水入侵距离进行实验研究,结果表明存在潮差临界值使得咸水入侵距离最短,当潮差小于该临界值,咸水入侵距离随潮差增大呈快速减小趋势,而大于该临界值则呈缓慢增大趋势。基于实验数据对盐淡水混合进行理论分析,揭示了实验现象的产生机制:①潮差增大过程中盐淡水混合由高度分层变为均匀混合,导致驱动咸潮入侵的动力发生了改变;②当盐淡水为弱混合类型,盐淡水高度分层,重力环流输运是盐进入河口的主要方式,潮汐强度增大减小了盐淡水分层,减弱了重力环流的输运作用,因此入侵距离变小;③当盐淡水为强混合类型,盐淡水混合均匀,重力环流输运作用大大减弱,潮汐扩散成为主要的输运方式,潮汐增强使得扩散能力增大,因此潮汐强度越大,咸潮入侵距离越大。 相似文献
10.
长江口北支沉积物粒度特征与沉积环境 总被引：1，自引：0，他引：1
长江口北支为喇叭口型中潮河口,在径流－潮流共同作用下,塑造了典型的心滩、边滩、沙嘴、潮流脊和潮汐汊道等地貌形态。本文根据所采集的长江口北支底质的粒度分析结果,利用数字地质方法对粒度参数进行对应分析;并在此基础上分析北支的沉积特征及沉积环境,揭示其沉积作用的动力机制。 相似文献
11.
Saltwater intrusion typically develops in the along-channel direction but exceptions can be found in bifurcated estuaries. Based on the observational data, we found that the saltwater intrusion in the upper reaches of the North Channel (NC) of Changjiang Estuary is dominated by the lateral saltwater intrusion from a small northern outlet (denoted as NONC) of this channel. This phenomenon has severe effects on the freshwater usage in this region. To investigate the underlying mechanisms of this pattern of intrusion, numerical experiments were conducted using a well-validated model. A flux decomposing method was used to decompose the process of saltwater intrusion into several mechanisms. During the neap tide, the saltwater begins to intrude landward into the NONC through shear transport induced by estuarine circulation. During the transition period between the neap tide and the following spring tide, the saltwater that previously reached the NONC further intrudes into the NC via Lagrangian and tidal pumping transports, causing a significant salinity increase in the middle and upper reaches of the NC. During the spring tide and the subsequent middle tide, saltwater intrusion in the NONC retreats. The impacts of the topography of the NONC and the wind stress on this lateral saltwater intrusion were also evaluated in this study. 相似文献
12.
River discharge, tide, wind, topography and other factors all have great impacts on the saltwater intrusion of Modaomen Waterway (MW), a major outlet of the Pearl River Estuary. A coupled 1D–3D numerical model was applied in this study to account for the dynamic characteristics of saltwater intrusion in the MW, and the impacts of tide and river discharge on the length of saltwater intrusion were uncovered. Results are as the followings: (1) River discharge from upstream induces an obvious dilution of salinity along the MW, whereas tide can exert a positive force that pushes salt water landward. The effects of river discharge and tide on the length of saltwater intrusion can be well described by a regression function; (2) the saltwater intrusion along the MW is generally aggravated by increases in tidal range from the South China Sea. The length of saltwater intrusion usually reaches a maximum 2 or 3 days before spring tide, and the hourly length of saltwater intrusion along the MW usually slows the tidal process for approximately 4 h, which can provide important information that the pumping operation along the MW to store freshwater in the backup storages needs to be at least 3 days ahead of the spring tide so as to avoid serious impact from saltwater intrusion; (3) the length of saltwater intrusion generally decreases with increasing river discharge. In 2005, 2009 and 2010, the average river discharge from upstream was 2680, 2630 and 3160 m3/s, respectively, with corresponding average lengths of saltwater intrusion of 32.7, 42.3 and 21.4 km. The inverse correlation between the water flow and the length of saltwater intrusion may provide some guidance for operations to maintain enough upstream flow to dilute the salinity and therefore satisfy the domestic water supply. 相似文献
13.
为进一步认识径流型河口枯季盐水上溯距离变化的影响因素及其作用机制,将实际河口简化并在不同径流量下分别用等潮差正弦潮和主要分潮驱动,进行盐水三维数值模拟试验。结果表明:随着径流和潮汐两大基本作用的相对强度不同,平衡态下盐水形态和位置自动调整并最终达到盐输运平衡,径流量小于3 000 m3/s且潮差小于2 m时,最大上溯距离随潮差的变化规律在不同径流量下存在明显差别;大小潮半月周期内盐水呈现非平衡态,非强混合时潮周期盐水上溯最大距离围绕平衡态随潮差呈顺时针绳套关系变化。径流导致的密度环流作用和潮汐的混合作用交织,两者相互影响并协同发展,两种作用相对强度的不同是导致径流型河口盐水上溯距离变化显著的主导因素。 相似文献
14.
Saltwater intrusion into coastal freshwater aquifers is an ongoing problem that will continue to impact coastal freshwater resources as coastal populations increase. To effectively model saltwater intrusion, the impacts of increased salt content on fluid density must be accounted for to properly model saltwater/freshwater transition zones and sharp interfaces. We present a model for variable density fluid flow and solute transport where a conforming finite element method discretization with a locally conservative velocity post-processing method is used for the flow model and the transport equation is discretized using a variational multiscale stabilized conforming finite element method. This formulation provides a consistent velocity and performs well even in advection-dominated problems that can occur in saltwater intrusion modeling. The physical model is presented as well as the formulation of the numerical model and solution methods. The model is tested against several 2-D and 3-D numerical and experimental benchmark problems, and the results are presented to verify the code. 相似文献
15.
Saltwater intrusion in coastal regions of North America 总被引：7，自引：3，他引：4
Saltwater has intruded into many of the coastal aquifers of the United States, Mexico, and Canada, but the extent of saltwater intrusion varies widely among localities and hydrogeologic settings. In many instances, the area contaminated by saltwater is limited to small parts of an aquifer and to specific wells and has had little or no effect on overall groundwater supplies; in other instances, saltwater contamination is of regional extent and has resulted in the closure of many groundwater supply wells. The variability of hydrogeologic settings, three-dimensional distribution of saline water, and history of groundwater withdrawals and freshwater drainage has resulted in a variety of modes of saltwater intrusion into coastal aquifers. These include lateral intrusion from the ocean; upward intrusion from deeper, more saline zones of a groundwater system; and downward intrusion from coastal waters. Saltwater contamination also has occurred along open boreholes and within abandoned, improperly constructed, or corroded wells that provide pathways for vertical migration across interconnected aquifers. Communities within the coastal regions of North America are taking actions to manage and prevent saltwater intrusion to ensure a sustainable source of groundwater for the future. These actions can be grouped broadly into scientific monitoring and assessment, engineering techniques, and regulatory approaches. 相似文献
16.
准确确定咸淡水界面位置是评价咸水入侵范围的前提。对于咸淡水界面位置的确定,传统研究以水化学法和物探法为主。为克服单一使用传统方法造成的人力、物力和财力的大量浪费,以莱州湾西南岸广饶县小清河以南咸水入侵区为研究对象,在综合分析研究区地下水开采现状、水化学监测结果的基础上,选择3个典型断面,采用水化学法中的野外现场电导率法,快速判断咸淡水界面大致位置（某两眼监测井之间）;再在一咸一淡的两眼监测井之间,采用高密度电阻率法快速、准确地确定咸淡水界面的空间分布。结果表明：该地区的地下水电导率若大于1.61 mS/cm,即可认为此处受到咸水入侵;咸淡水界面位置的视电阻率特征值为11~13 Ω·m,咸淡水界面附近咸水体呈舌状入侵并主要发生在地表以下13 m内的浅层地下水中。 相似文献
17.
山东烟台夹河中、下游地区海水入侵三维水质数值模拟研究 总被引：17，自引：0，他引：17
建立了三维变密度对流弥散水质数学模型来研究山东省烟台夹河中、下游地区咸淡水界面的运移规律。以四面体为基本离散单元 ,推导出三维海水入侵变密度水质模型求解的数值方法 ,其中水流方程求解时运用了迦辽金有限单元法。溶质运移方程求解时运用了欧拉拉格朗日混合方法 ,将对流项与弥散项分离 ,用传统迦辽金有限元方法求解弥散项 ;采用自适应MOC MMOC法求解对流项 ,以消除人工过量和数值弥散。根据地下水的潮汐效应观测信息 ,确定了含水系统的海底延伸边界 ;利用该地区地下水水头及水质长观资料识别了模型的水文地质参数 ,探讨了夹河地区海水入侵的原因 :认为夹河下游地区滨海地带地下水过量开采是造成烟台地区海水入侵的主要原因。此外 ,海水随潮定期地倒灌进入夹河 ,通过局部岩性天窗侵入淡水含水层加剧了沿夹河河床两侧地下水的咸化。同时还预测了几种情况下地下水的水质演化趋势 ,为防止和减轻夹河地区海水入侵提供合理、科学的依据。 相似文献