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海水入侵作为一个全球化的问题,正随着沿海地区对地下淡水需求的增加而不断加剧,其不断发展引起地下水水质
恶化、土壤盐渍化等一系列生态环境问题。海水入侵的相关研究既具有重要的理论意义,对沿海地区的可持续发展也有重
要的实际价值,因此逐渐成为了国际研究的热点。随着数值计算方法及计算平台的不断发展,数值模拟方法已经成为研究
海水入侵问题最有效的工具之一。文章总结归纳了多种海岸带类型的划分方法与标准,从海岸带水文地质学的角度将海岸
带概括为松散岩类和基岩类两大类,并将其含水介质分别概化为等效多孔介质和裂隙岩溶介质。在此基础上,分析阐述这
两类含水介质海水入侵的数值模拟方法及其适用性,对当前海水入侵数值模拟方法进行了较为全面的概括。此外,对海水
入侵数值模拟方法的发展方向及趋势进行了展望,指出考虑密度变化的过渡带模型和离散-连续介质耦合模型将成为今后
研究中的重点发展方向。 相似文献
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通过对大连大魏家、秦皇岛枣园和莱州湾南岸海水入侵的调查,结合已有研究成果和方法,笔者总结和梳理了环渤海地区海水入侵研究现状及存在的问题,并探讨了海水入侵调查研究技术方法。多年来对环渤海地区海水入侵的调查研究工作,基本查清了不同地段、不同类型海水入侵的机理和动态变化趋势,并为海水入侵有效防治提供了科学依据。随着海水入侵问题研究的深入,发现在水文地质条件、地下水动态监测及海水入侵对生态环境影响等方面仍存在问题,应持续加强海水入侵监测与研究。海水入侵调查研究是一项涉及多学科的综合性技术,应从基础调查,综合分析、动态监测和数值模拟等多方面开展研究。综合运用水化学分析、同位素示踪、室内模拟试验等技术方法,在充分揭示海水入侵机理和过渡带溶质运移规律的基础上,实现对海水入侵变化趋势的预测预报,提高对海水入侵的防范意识。 相似文献
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海水入侵的实验研究 总被引：10，自引：0，他引：10
张奇 《水文地质工程地质》2005,32(4):43-47
在海岸含水层中,含较多盐分的海水向陆地方向入侵形成淡-咸水交界面,通常称为海水入侵界面。该界面的动态变化受气象、水文地质和人类活动等因素的影响,是海水入侵问题的主要研究内容。本文介绍了海水向含水层中入侵的室内实验研究,以着色海水和图像处理方法获得入侵界面的形态及其动态变化。实验方法先进,所得数据整体性强,精度高,而且观测方法对流场没有干扰,比传统的提取水样进行化验的方法更有效。实验中模拟了海洋潮汐条件,揭示了入侵界面在不同实验条件下的动态特征。应用数值模拟方法揭示了流场的特征。计算表明,流场分两个区———淡水区和咸水区,由入侵界面分开。淡水区的水流相对活跃,淡水由入侵界面以上区域渗出边界,在界面以上形成淡水通道。 相似文献
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海水入侵是困扰沿海地区经济社会发展的重大资源、环境问题,严重影响沿海地区地下水资源。定量模拟、预测和可视化管理是对海水入侵进行有效监测和机理分析的重要手段。基于前期海水入侵模拟的理论研究及方法,提出了海水入侵模拟及预测模型VFT3D,该模型综合考虑地表水-地下水对海水入侵的协同控制作用,能够模拟变密度地下水流及复杂反应性迁移,实现模拟海水入侵的完整水文循环过程。文章介绍了VFT3D模型,利用VFT3D模型模拟了一个海水入侵案例,并与SEAWAT模型模拟结果进行了对比分析。结果表明VFT3D 模型模拟水头与SEAWAT模型模拟结果相差不大,但SEAWAT模型无法模拟海水入侵中复杂的化学反应过程。VFT3D 模型模拟发现,水文地球化学过程（阳离子吸附交换作用）对阳离子（Na+、K+、Mg2+和Ca2+）运移产生明显影响,同时引起过渡带中离子组分浓度发生变化,对海水入侵过程产生较大影响。因此,考虑变密度和复杂反应过程,才能更加准确地描述海水入侵,从而有利于地下咸水治理工程的科学实施。 相似文献
6.
为实现滨海含水层地下水开采-回灌方案优化、控制海水入侵面积和降低海水入侵损失等多重管理目标,建立了海水入侵条件下地下水多目标模拟优化管理模型SWT-NPTSGA。模拟模型采用基于变密度流的数值模拟程序SEAWAT来模拟海水入侵过程。优化模型采用小生境Pareto禁忌遗传混合算法NPTSGA来求解,该算法在保证多目标权衡解的收敛性和计算效率的前提下,能维护整个进化群体的全局多样性。将SWT-NPTSGA程序应用于一个理想滨海含水层地下水开采方案和人工回灌控制海水入侵的优化设计中,结果表明该管理模型能够同时处理最大化总抽水流量、最小化人工回灌总量和最小化海水入侵范围等3个目标函数之间的权衡关系。通过采用人工回灌海水入侵区的减灾策略,既能增加滨海地区的供水量,又可减少海水入侵的范围,由此进一步验证了模型的有效性和可靠性。 相似文献
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在一定条件下,水动力弥散作用较弱时,可应用突变界面模型来研究滨海含水层的海水入侵.本文应用了边界元数值模拟方法和狭缝槽模型,对影响界面运动的因素进行了分析,得出了界面变化的主要特征是:向内陆方向推进慢而向海洋方向消退快.有关结论可应用于地下水资源的管理和保护. 相似文献
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中国滨海城市地下水开发与海水入侵的研究 总被引：7，自引：0，他引：7
本文经过对中国滨海城市海水入侵的研究，系统地总结了海水入侵的若干特点，详细地分析论述了海水入侵与地下水开发的关系，全面地介绍了中国目前已建立的海水入侵数值模型，并且提出了一系列切实可行的海水入侵防治措施。 相似文献
11.
It is important to understand how phosphate sorption dynamics of coastal carbonate aquifers are affected by seawater intrusion, because many coastal aquifers are composed of carbonate rocks and subject to an increase in saltwater intrusion during relative sea-level rise. Twelve carbonate rock and unconsolidated sediment specimens were acquired from a test corehole spanning the full thickness of the Biscayne aquifer in southeastern Florida. All 12 samples exhibit low phosphorus content but variable contents of iron. Column leaching experiments were conducted with two carbonate aquifer samples, alternating between freshwater and saltwater flow. With the first influx of saltwater, phosphate concentration in leachate increased rapidly from a freshwater value of approximately 0.2 μM to peaks of between 0.8 and 1.6 μM. The phosphate concentration began to diminish as saltwater continued to flow, but sustained desorption continued for over 2 h. Overall, seawater drove sorption behavior much more than chemical composition for the aquifer rocks and sediment from the seven rock samples for which we did isotherm sorption experiments. Our results indicate that an immediate and intense pulse of phosphate desorption from carbonate rock and sediment with low phosphorus content occurs in response to an influx of seawater and that the duration of desorption will vary by layer within a single aquifer. 相似文献
12.
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
13.
J. Rey J. Martínez G. G. Barberá J. L. García-Aróstegui J. García-Pintado D. Martínez-Vicente 《Environmental Earth Sciences》2013,70(5):2271-2282
Anthropogenic pressure influences the two-way interactions between shallow aquifers and coastal lagoons. Aquifer overexploitation may lead to seawater intrusion, and aquifer recharge from rainfall plus irrigation may, in turn, increase the groundwater discharge into the lagoon. We analyse the evolution, since the 1950s up to the present, of the interactions between the Campo de Cartagena Quaternary aquifer and the Mar Menor coastal lagoon (SE Spain). This is a very heterogeneous and anisotropic detrital aquifer, where aquifer–lagoon interface has a very irregular geometry. Using electrical resistivity tomography, we clearly identified the freshwater–saltwater transition zone and detected areas affected by seawater intrusion. Severity of the intrusion was spatially variable and significantly related to the density of irrigation wells in 1950s–1960s, suggesting the role of groundwater overexploitation. We distinguish two different mechanisms by which water from the sea invades the land: (a) horizontal advance of the interface due to a wide exploitation area and (b) vertical rise (upconing) caused by local intensive pumping. In general, shallow parts of the geophysical profiles show higher electrical resistivity associated with freshwater mainly coming from irrigation return flows, with water resources mostly from deep confined aquifers and imported from Tagus river, 400 km north. This indicates a likely reversal of the former seawater intrusion process. 相似文献
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Saltwater intrusion is generally related to seawater-level rise or induced intrusion due to excessive groundwater extraction in coastal aquifers. However, the hydrogeological heterogeneity of the subsurface plays an important role in (non-)intrusion as well. Local hydrogeological conditions for recharge and saltwater intrusion are studied in a coastal groundwater system in Vietnam where geological formations exhibit highly heterogeneous lithologies. A three-dimensional (3D) hydrostratigraphical solid model of the study area is constructed by way of a recursive classification procedure. The procedure includes a cluster analysis which uses as parameters geological formation, lithological composition, distribution depth and thickness of each lithologically distinctive drilling interval of 47 boreholes, to distinguish and map well-log intervals of similar lithological properties in different geological formations. A 3D hydrostratigraphical fence diagram is then generated from the constructed solid model and is used as a tool to evaluate recharge paths and saltwater intrusion to the groundwater system. Groundwater level and chemistry, and geophysical direct current (DC) resistivity measurements, are used to support the hydrostratigraphical model. Results of this research contribute to the explanation of why the aquifer system of the study area is almost uninfluenced by saltwater intrusion, which is otherwise relatively common in coastal aquifers of Vietnam. 相似文献
15.
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
16.
Delineation of saltwater intrusion into the freshwater aquifer of Lekki Peninsula,Lagos, Nigeria 总被引：2，自引：0，他引：2
A. A. Adepelumi B. D. Ako T. R. Ajayi O. Afolabi E. J. Omotoso 《Environmental Geology》2009,56(5):927-933
Recently, the deterioration of water quality in the coastal zones of Lekki Peninsula area of Lagos due to saltwater infiltration
into the freshwater aquifer has become a major concern. With the aim of providing valuable information on the hydrogeologic
system of the aquifers, the subsurface lithology and delineating the groundwater salinity, vertical electrical resistivity
(VES) sounding survey was carried out utilizing surface Schlumberger electrode arrays, and electrode spacing varying between
1 and 150 m. The DC resistivity surveys revealed significant variations in subsurface resistivity. Also, the VES resistivity
curves showed a dominant trend of decreasing resistivity with depth (thus increasing salinity). In general, the presence of
four distinct resistivity zones were delineated viz.: the unconsolidated dry sand (A) having resistivity values ranging between
125 and 1,028 Ωm represent the first layer; the fresh water-saturated soil (zone B) having resistivity values which correspond
to 32–256 Ωm is the second layer; the third layer (zone C) is interpreted as the mixing (transition) zone of fresh with brackish
groundwater. The resistivity of this layer ranges from 4 to 32 Ωm; while layer four (zone D) is characterized with resistivities
values generally below 4 Ωm reflecting an aquifer possibly containing brine. The rock matrix, salinity and water saturation
are the major factors controlling the resistivity of the formation. Moreover, this investigation shows that saline water intrusion
into the aquifers can be accurately mapped using surface DC resistivity method. 相似文献
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Coastal aquifers are usually exposed to saltwater intrusion. Therefore, groundwater extracted from these aquifers should be regulated considering their dimensions and effective parameters. In this paper, optimum discharge from a large number of exploitation wells is evaluated according to variations of width, length, and anisotropy coefficient in the Qom aquifer near the salt lake in central Iran. First, the wells are divided into clusters to decrease the number of decision variables. Then, the location and discharge from each cluster is obtained using SEAWAT and charged system search (CSS) simulation–optimization model with the assumption of three-dimensional variable density flow. The maximum discharge considering various anisotropy rates is computed based on different values of lengths and widths of the aquifer. Finally, an M5-tree model is trained using the obtained samples to derive a linear relationship between input and output data. Based on the results, for various ranges of width and length of an aquifer with impermeable boundaries, different linear equations for optimum discharge are obtained. Also, it was found that for an aquifer with a small width, the critical discharge is a function of the length while the effect of the boundaries is negligible. Sensitivity analysis of the anisotropy coefficient reveals that with increasing the anisotropy rate, thickness and slope of the transition zone decrease and as the maximum discharge increases consequently. However, the sensitivity of the discharge to anisotropy rate is not remarkable. A comparison between the results of this study with those of the analytical method based on sharp interface assumption is carried out. For the critical condition, the best agreement between analytical equation (\(\overline {L} =0.87\overline {W} +0.62\)) and proposed method (\(\overline {L} =0.83\overline {W} - 1.41\)) is achieved for the anisotropic aquifer when the 50% isochlor is assumed as the measure of salt water intrusion. 相似文献
18.
Simulation-optimization approach to assess groundwater availability in Refugio County, TX 总被引：10，自引：0，他引：10
Sustainable management of groundwater resources is critical for viable development of semi-arid regions. Refugio County, TX,
is predominantly a rural community that is in close proximity to two large urban areas of Corpus Christi and San Antonio.
Large-scale water supply projects are being planned to export surplus water available in Refugio County to nearby growing
cities. Being a coastal county with several sensitive bays and estuaries, these projects have caused concerns with regard
to decreases in freshwater inflows to coastal bodies and raised the possibility of saltwater intrusion. A simulation model
characterizing groundwater flow in the shallower unconfined and the deeper semi-confined formations of the Gulf coast aquifer
was calibrated and evaluated. The model results were used in conjunction with a mathematical programming scheme to estimate
maximum available groundwater in the county. Stakeholder concerns were incorporated as constraints, which included prevention
of saltwater intrusion in the aquifer, limiting the amount of allowable drawdown in shallow aquifers, as well as maintaining
current flow gradients especially near baseflow-dependent streams and rivers. For the conditions assumed in this study, the
model results indicate that roughly 4.93 × 107 m3 of water can be extracted in a typical year. The management model was noted to be very sensitive to the imposed saltwater
intrusion constraint. 相似文献
19.
Despite the broad impact and importance of saltwater intrusion in coastal aquifers, little research has been directed towards forecasting saltwater intrusion in areas where the source of saltwater is uncertain. Saline contamination in inland groundwater supplies is a concern for numerous communities in the southern US including the city of Deltona, Florida. Furthermore, conventional numerical tools for forecasting saltwater contamination are heavily dependent on reliable characterization of the physical characteristics of underlying aquifers, information that is often absent or challenging to obtain. To overcome these limitations, a reliable alternative data-driven model for forecasting salinity in a groundwater supply was developed for Deltona using the fast orthogonal search (FOS) method. FOS was applied on monthly water-demand data and corresponding chloride concentrations at water supply wells. Groundwater salinity measurements from Deltona water supply wells were applied to evaluate the forecasting capability and accuracy of the FOS model. Accurate and reliable groundwater salinity forecasting is necessary to support effective and sustainable coastal-water resource planning and management. The available (27) water supply wells for Deltona were randomly split into three test groups for the purposes of FOS model development and performance assessment. Based on four performance indices (RMSE, RSR, NSEC, and R), the FOS model proved to be a reliable and robust forecaster of groundwater salinity. FOS is relatively inexpensive to apply, is not based on rigorous physical characterization of the water supply aquifer, and yields reliable estimates of groundwater salinity in active water supply wells. 相似文献
20.
The present study concerns the application of a numerical approach to describe the influence of anthropogenic modifications in surface flows (operation of a projected reservoir) on the freshwater-seawater relationships in a downstream coastal aquifer which has seasonal seawater intrusion problems (River Verde alluvial aquifer, Almuñécar, southern Spain). A steady-state finite element solution to the partial differential equation governing the regional motion of a phreatic surface and the resulting sharp interface between fresh water and salt water was used to predict the regional behavior of the River Verde aquifer under actual surface flow conditions. The present model approximates, with simple triangular elements, the regional behavior of a coastal aquifer under appropriate sinks, sources, Neumann and open boundary conditions. A steady-state solution to this numerical approach has been shown to precisely calculate freshwater heads, saltwater thicknesses, and freshwater discharges along steeply sloping coasts. Hence, the adequate treatment and interpretation of the hydrogeological data which are available for the River Verde aquifer have been of main concern in satisfactorily applying the proposed numerical model. Present simulated conditions consider steady-state yearly averaged amounts of external supplies of fresh water in order to determine the influences of the projected Otívar reservoir on the further behavior of the River Verde coastal aquifer. When recharges occur at the coastline, essentially because of freshwater deficits due to groundwater overexploitation, a hypothesis of mixing for the freshwater-saltwater transition zone is made in order to still allow the model to continue calculating groundwater heads under the sea level, and, as a consequence, the resulting seawater intrusion and recharges of saltwater from the sea. Simulations show that a considerable advance in seawater intrusion would be expected in the coastal aquifer if current rates of groundwater pumping continue and a significant part of the runoff from the River Verde is channeled from the Otívar reservoir for irrigation purposes. 相似文献