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1.
淡水透镜体作为海岛上珍贵的地下淡水资源,对于满足居民生活用水与维护生态系统具有重要作用,增加海岛地下淡水资源储量可有效缓解海岛地区普遍存在的水资源短缺问题。本研究提出通过在海岛外部区域采用低渗透性介质材料增加海岛地下淡水资源储量的方法,采用室内物理模型实验与基于变密度地下水流溶质运移模型的数值模拟相结合的方法对提出方法的有效性进行了验证,并通过野外尺度的数学模型分析工程实施可能性。实验与数值模拟结果较吻合,表明该方法具有抵御海水入侵、增加海岛地下淡水资源储量的巨大潜力。通过基于野外尺度的数值模拟分析工程实施的可能性,发现对于降雨入渗补给强度为0.005 7 m/d、长度为200 m,孔隙度为0.3的狭长形均质海岛,地下淡水储量为66.5 m3/m,在海岛外部区域采用渗透系数为1 m/d、厚度为5 m的低渗透性介质材料后,淡水透镜体经过约8 a时间可再次达到稳态,地下淡水储量为343.8 m3/m,增加约4倍,工程实施具备一定可能性。本研究为缓解海岛地区缺水问题、实现淡水资源可持续利用提供了一种新方法。 相似文献
2.
钙质砂的水理性质对岛礁地下淡水透镜体的形成至关重要。通过室内试验的方法从透水性、容水性和给水性3个方面对南海钙质砂的水理性质进行了研究,并在此基础上进一步结合数值模拟手段,探讨了上述相关性质对岛礁淡水透镜体形成的影响。结果表明：南海钙质砂多具有级配不良且不均匀的特征;其渗透系数通常在0.023~110 m/d之间,区域间差异较大,而孔隙度和给水度则主要集中在0.40~0.55和0.012~0.310之间,与同粒径范围的陆源砂相比,呈现出容水性好但给水性偏低的特征。钙质砂的水理性质对岛礁地下淡水透镜体形成的影响主要体现在流速、厚度、资源储量以及形成时间等方面,其中钙质砂的透水性越好,地下水中的流速越快,咸淡水间的混合作用越强,导致淡水透镜体的厚度越薄,储量越少;给水性则主要影响钙质砂中淡水透镜体的资源储量,对淡水透镜体的厚度及形状影响较小。 相似文献
3.
淡水透镜体是位于岛屿的地下像凸透镜一样,中间厚四周薄的淡水层,是岛礁环境的重要组成部分。以位于西太平洋北马里亚纳群岛的Saipan岛为研究区域,基于为Ocean Vista Resort酒店项目寻找稳定水源中的相关地层与构造勘探成果,综合岛上现有水文地质资料,合理概化该岛屿的水文地质概念模型,对淡水透镜体的赋存状态、取水井中氯化物的浓度变化与井位选取、淡水透镜体厚度变化规律进行分析,在此基础上对岛屿商业开发供水水源类型及供水潜力进行评价,明确限制饮用水开发可利用性的主要因素,提出Ocean Vista Resort项目水源地的开发建议。结果认为：Saipan岛上地下淡水唯一补给为大气降水,降雨随高渗透性的礁灰岩渗透到地下,并在地下向海边运移,最终在海岸带排出,形成悬浮在咸水上的淡水透镜体,淡水透镜体的形状呈凸圆状,其厚度的变化受季节性交替,岛中心位置厚,朝向海岸线方向相当薄,研究区限制饮用水可利用性的因素主要是海水入侵、井群干扰导致的地下水位降低和向海洋排泄;在为Ocean Vista Resort项目进行地下水开发时应合理布置钻孔,找出饮用淡水透镜体最厚的井的位置,确认井深没有揭穿相... 相似文献
4.
淡水透镜体作为海岛主要的甚至是唯一的淡水资源,对其在天然和开采条件下的演变规律研究是海岛淡水资源利用和管理的首要任务。采用自制的室内物理模型,对海岛淡水透镜体的演变过程进行了模拟实验。模拟了降雨补给条件下淡水透镜体的形成过程;在无补给条件下,开采淡水时倒锥的变化过程。结果表明：当开采量达到3.73×10-5m3/s时,倒锥进入抽水井,淡水透镜体被击穿。 相似文献
5.
大气降水是滨海盐碱地区浅层地下水的重要补给来源。滨海地区浅层地下水多为咸水且埋藏较浅,在不同包气带岩性渗透性差异下,在大气降水入渗补给过程中,一定时间内潜水面以上一定范围内存在淡水分布,即淡水透镜体,它能局部隔离地下咸水对上层土壤和植物的危害,并在一定程度上供给植物吸收利用。采用自制的室内物理模拟装置,通过控制土层结构,模拟了大气降水入渗补给条件下包气带中淡水透镜体的形成与消退过程,探讨了不同土壤类型中淡水透镜体的维持情况;并利用吸水管模拟客土上所种植物根系吸水,研究了不同吸水量条件下土壤中淡水透镜体的变化规律。结果表明:上层中砂、底层粉砂质黏土的双层土体结构中,淡水透镜体的维持性最好,在降水入渗补给条件下,透镜体形成时间在1500 min左右可达最大厚度(约15 cm),若补给源消失,透镜体完全消退需7500 min,能较长时间地阻隔地下咸水;双层土中模拟形成的稳定淡水透镜体在无补给条件下,能够隔离地下咸水的同时亦能为上层植物提供243.5 mL淡水资源。 相似文献
6.
本文依据对庙岛群岛基岩裂隙水进行的地质构造、水文地质、物探等方面的研究,提出了适用于我国东部沿海基岩海岛的地下淡水蘑菇体新模式。以新构造控水为指导思想,探讨了基岩海岛裂隙水的赋存条件及富集规律,指出了地下水资源开发方向,并且结合生产实际,比较有效地解决了研究区变质岩海岛找淡水难的问题。 相似文献
7.
细颗粒对钙质砂渗透性的影响试验研究 总被引：1，自引：0，他引：1
钙质砂地基的渗透性是影响人工灰沙岛地下淡水形成的重要因素,而细颗粒的含量及其赋存状态对渗透性有重要的影响,为此开展了不同细颗粒含量的钙质砂渗透性试验研究。选用南海某岛的钙质砂,基于不同细粒配比的钙质砂样常水头渗透试验,分析细颗粒对钙质砂地层渗透性的影响。试验结果显示,促使钙质砂渗透性发生明显变化的粒级为≤0.075mm范围。当最小粒径≤0.075mm时,钙质砂的渗透系数量级为10^-2cm/s,呈中透水性。当最小粒径介于0.075~0.500mm时,渗透系数量级为10^-1cm/s,呈高透水性。钙质砂最终稳定渗透系数与细粒含量之间表现出不同的规律:(1)当细颗粒含量小于9%时,渗透系数随细粒含量的增加而缓慢减小;(2)当细颗粒含量在9%~24%时,渗透性随细粒含量的增加而迅速减小;(3)当细颗粒含量大于24%时,渗透性随细粒含量的增加变化不大。影响渗透系数的细粒含量存在着由试样骨架形成的孔隙决定的,反映孔隙最佳充填时的细粒含量界限值,充填不佳或过量细粒均可能在渗透作用下发生细粒运移流失。 相似文献
8.
为了探究土的分层特征对珊瑚礁岛下淡水透镜体形成的意义,在南海某珊瑚礁岛采用钻孔取样,分析每个钻孔不同层位样品的粒度。根据水平和垂直方向上的粒度特征,确定岛的水平分区和垂直分层;根据每个钻孔所代表的范围,确定每个水平分区的面积;根据每个钻孔中不同颗粒级配的样品所代表的厚度,确定每个垂直分层厚度。礁灰岩以上松散层的不同分区和分层的颗粒级配控制地层的渗透性,垂直和水平方向的渗透性特征控制淡水透镜体形成的难度、淡水透镜体的总厚度以及过渡带的厚度。根据岛的总面积和垂直分层数建立数值模型,得到不同时间、不同水平位置和垂直深度的地下水浓度特征的模拟结果。 相似文献
9.
防渗膜（HDPE土工膜）目前广泛应用于防污染、防渗漏、防扩散为主的防渗工程中，且铺设形式复杂多样。在我国某露天煤矿地下截水帷幕工程中，将防渗膜进行大深度垂向隐蔽铺设，深度可突破50 m，作为帷幕墙防渗主体；利用接头箱技术，实现了不同槽段间的防渗膜叠覆连接；通过注浆回填工艺，在压紧防渗膜的同时，提高了帷幕墙的抗渗性；最后采用围井抽水试验验证了墙体的防渗性，结果表明，防渗膜帷幕墙渗透系数仅为8.6×10-7 cm/s，达到设计要求。防渗膜帷幕墙具有施工效率高、成本低、绿色环保等优点，其成功应用对其他类似项目具有推广借鉴意义。 相似文献
10.
11.
Groundwater in a coral island 总被引：4，自引：3，他引：1
Freshwater aquifers in small coral islands usually occur as thin lenses which are significantly influenced by stresses such
as groundwater pumping, sea tides, etc. Kavaratti, a coral island, is one of the 36 such islands in the Arabian Sea off the
western coast of India. Detailed hydrogeological investigations were carried out to determine the quantity of freshwater that
could be pumped in addition to the present usage. Salinity of groundwater must remain within permissible limits and a 2-D
solute mass transport model with a vertical section of the island was constructed by the computer code SUTRA. The model was
calibrated by obtaining a match of computed and observed values of the water table, tidal efficiency, and salinity of groundwater
at the water table. The model analysis showed that the salinity of groundwater continues to increase unless groundwater pumping
is kept below a certain rate. Groundwater potential can be augmented by reducing the subsurface outflow to the sea and by
raising the water table by a subsurface dam.
Received: 8 September 1997 · Accepted: 27 April 1998 相似文献
12.
Management of freshwater lenses on small Pacific islands 总被引：3，自引：0，他引：3
The nature of shallow aquifers and the impacts of seawater intrusion in small islands within the Pacific Ocean are reviewed. Many Pacific islands rely on shallow fresh groundwater lenses in highly permeable aquifers, underlain and surrounded by seawater, as their principal freshwater source. It is argued here that, in small islands, the nature of fresh groundwater lenses and their host aquifers coupled with frequent natural and ever-present anthropogenic threats make them some of the most vulnerable aquifer systems in the world. A simple steady-state approximation is used to provide insight into the key climatic, hydrogeological, physiographic, and management factors that influence the quantity of, and saline intrusion into freshwater lenses. Examples of the dynamic nature of freshwater lenses as they respond to these drivers are given. Natural and human-related threats to freshwater lenses are discussed. Long dry periods strongly coupled to sea surface temperatures impact on the quantity and salinity of fresh groundwater. The vulnerability of small island freshwater lenses dictates careful assessment, vigilant monitoring, appropriate development, and astute management. Strategies to aid future groundwater sustainability in small islands are presented and suggested improvements to donor and aid programs in water are also advanced. 相似文献
13.
Modelling the response of fresh groundwater to climate and vegetation changes in coral islands 总被引：2，自引：1，他引：1
Jean-Christophe Comte Jean-Lambert Join Olivier Banton Eric Nicolini 《Hydrogeology Journal》2014,22(8):1905-1920
In coral islands, groundwater is a crucial freshwater resource for terrestrial life, including human water supply. Response of the freshwater lens to expected climate changes and subsequent vegetation alterations is quantified for Grande Glorieuse, a low-lying coral island in the Western Indian Ocean. Distributed models of recharge, evapotranspiration and saltwater phytotoxicity are integrated into a variable-density groundwater model to simulate the evolution of groundwater salinity. Model results are assessed against field observations including groundwater and geophysical measurements. Simulations show the major control currently exerted by the vegetation with regards to the lens morphology and the high sensitivity of the lens to climate alterations, impacting both quantity and salinity. Long-term changes in mean sea level and climatic conditions (rainfall and evapotranspiration) are predicted to be responsible for an average increase in salinity approaching 140 % (+8 kg m?3) when combined. In low-lying areas with high vegetation density, these changes top +300 % (+10 kg m?3). However, due to salinity increase and its phytotoxicity, it is shown that a corollary drop in vegetation activity can buffer the alteration of fresh groundwater. This illustrates the importance of accounting for vegetation dynamics to study groundwater in coral islands. 相似文献
14.
N. C. Mondal V. S. Singh D. V. Sarwade M. V. Nandakumar 《Journal of Earth System Science》2009,118(3):217-229
A group of 36 coral islands is being scattered in the Arabian Sea off the western coast of India. On such islands, groundwater
is the only source of fresh water for the islanders. The demand for groundwater is increasing every year due to growing population
and urbanization. On the other side the peculiar hydrologic, geologic and geomorphic features restrict the availability of
groundwater. Thus a proper understanding of the groundwater condition is important in order to meet this increasing demand
and also to formulate future development and management strategies. Detailed hydrogeological, geophysical and hydrochemical
studies had been carried out to identify potential fresh groundwater resources and quantify vulnerable parts of Andrott Island,
Union Territory of Lakshadweep. Systematic collection and analysis of hydrological, geophysical and hydrochemical data gives
an early signal of deterioration in groundwater quality in the peripheral parts of eastern and western coasts of this island
and it suggests immediate measures for arresting the deterioration in groundwater quality as well as augmentation for restoration
of aquifer in some parts of the island. 相似文献
15.
A comparison of the d-excess values of precipitation and of spring water, streams, groundwater wells and submarine groundwater discharge indicated that the precipitation that occurred during winter season was an important source of groundwater recharge. Due to the steep slope of the island, most of the short duration and high intensity precipitation is lost through direct surface runoff. The comparison indicated that snowmelt is an important resource of groundwater recharge on Rishiri Island. Future climate change will continue to diminish the snowpack, and therefore, reduce groundwater recharge. It may cause the decline of the groundwater level in the coastal area and possibly shift the saline–freshwater boundary on the island. Chloride data indicated that saltwater intrusion is beginning to occur on the western flank of the island. A Piper diagram shows that the water samples are characterized by the dominance of the Ca–HCO3 and Na–Cl type. Their chemistry probably results from sea salt spray and the dissolution of minerals. These results support the need for the effective management of groundwater resources. 相似文献
16.
高坝泄洪雾化雨入渗是影响其水垫塘边坡稳定的关键因素之一。为分析乌东德水电站水垫塘边坡受泄洪雾化雨影响程度,选取水垫塘边坡典型断面,建立二维非饱和、非稳定渗流计算模型,采用有限元法模拟泄洪雾化雨入渗过程,分析雾化雨入渗条件下坡体饱和区范围及压力水头的变化规律,同时对比研究坡面防护措施的效果。结果表明,对于坡体内部渗透性上强、下弱的部位,随着入渗补给量的持续增加,在阻水部位压力水头会逐渐升高;当坡面采取弱透水材料防护后,可显著减少坡面雾雨入渗量,从而显著降低雾化雨入渗对坡体渗流场的影响 相似文献
17.
Groundwater travel times for unconfined island aquifers bounded by freshwater or seawater 总被引：1，自引：1，他引：0
Analytical solutions for calculating groundwater travel times within unconfined island aquifers are given for cases of both a freshwater-bounded island (island located in a fresh water lake) and an oceanic island (freshwater contained above intrusive saltwater). The solutions apply for homogenous aquifers recharged by surface infiltration and discharged by a down-gradient, fixed-head boundary, under steady-state conditions. The solutions are given for two simple island geometries: circular islands and strip islands. A technique is also provided for comparing travel times in inland islands and oceanic islands. Travel times in oceanic islands are found to be shorter than travel times in inland islands, and travel times in circular islands are found to be longer than travel times in strip islands. 相似文献
18.
岛屿是我国领土的重要组成部分,对国家安全和国防军事意义非凡。岛屿的地下水资源尤为珍贵,地下水流场模拟是研究地下水分布规律的重要手段。水文地质条件复杂、可利用的观测井较少等原因,造成了基岩岛屿水文地质模型概化精度不高、初始条件难以获取等问题。为克服基岩岛屿地下水流场模拟的诸多困难,将珠海外伶仃岛作为研究区,利用数字高程模型数据开展地质地貌建模; 利用探地雷达法、直流电法与地质分析对岛屿进行探测,获取了地层数据; 采用地下水遥感评估法,利用实测井位数据,确定了地下水的初始水位,进而对基岩岛屿地下水流场进行建模; 最终,通过对外伶仃岛地下水流场的数值模拟得出地下水模拟流场图。岛上多个测点的探测水位值与模拟水位相关性较好,其拟合优度R2为0.872 2。由此可见,综合遥感、物探、水文地质手段等技术方法获取的数据,采用地下水模拟软件或程序实现基岩岛屿地下水流场的数值模拟,是基岩岛屿地下水资源研究的一个有效方法。 相似文献