平度市地下水人工回灌补源试验研究

由过度开采而引起的地下水资源短缺已经成为平度市面临的最为迫切的环境问题之一。地下水人工回灌可以有效的恢复地下水位、增加地下水资源,实施人工回灌的第一步是对含水层进行回灌试验研究。根据现场水文地质条件,采用管井回灌法,通过反滤回灌井和普通回灌井试验,确定其稳定回灌量;利用干扰井回灌试验,分析普通回灌井间的合适距离;对比了回灌井间歇运行与连续运行的回灌效果;研究了渗透系数在回灌过程中的变化规律。研究结果表明:普通回灌井的回灌能力优于反滤回灌井;相距75m的回灌井相互干扰较小;回灌井的最大单井稳定回灌量为33.4m~3/h;渗透系数随回灌时间的衰减符合指数函数关系,且潜水-承压回灌井的衰减程度大于潜水回灌井。     

人工回灌控制基坑工程地面沉降的数值模拟

人工回灌是控制基坑降水工程引起地面沉降的有效手段,本文以上海地铁2、4、9号3条地铁线所围区域盛大基坑降水为例,探讨基坑降水地下水回灌控制地面沉降的作用机理,并基于下负荷面剑桥理论,建立水-土耦合的地面沉降数学模型,预测基于人工回灌的深基坑工程地面沉降,与实测地面沉降数据对比,得到比较符合实际的数值模拟结果,真实地反映了基坑开挖、支撑和降水共同作用下的地面沉降,值得基坑降水回灌工程推广。     

中国沿海地区地面沉降的危害及防治对策--以天津市为例

中国沿海地区地面沉降问题非常突出。主要以天津市为例,对地面沉降所造成的危害作以分析和阐述,并提出相应减缓和防治沿海地区地面沉降的对策。认为过量开采地下水是沿海地区地面沉降问题的主要原因,节约用水、限量开采、解决替代水源、人工回灌地下水等是防治地面沉降的主要对策。最后,就地面沉降监测和治理方面的新技术、新方法做了简单的介绍。     

青岛地区玄武岩蓄水条件探讨

提出在青岛开发利用玄武岩地下水资源。探讨白垩纪与第三纪玄武岩孔洞裂隙水分布、赋存特征、蓄水条件、富集规律、水量与水质评价、利用现状,开发利用存在的问题以及合理开发玄武岩地下水资源的主要措施。     

人工回灌过程中含水介质物理堵塞的试验研究

采用土柱渗流试验,模拟人工回灌过程中含水层的物理堵塞过程。通过测定回灌过程中含水介质渗透系数的时-空变化,系统分析和评价回灌液悬浮物浓度和水动力条件对堵塞的影响,并探讨含水介质的物理堵塞机理。研究表明,随着回灌液中悬浮物浓度的增大,悬浮物首先在含水介质的表层沉积,当悬浮物浓度为50、100、200mg/L时,回灌结束后砂柱表层介质的渗透系数分别降至初始的21%、13%和4%,表明表层发生了不同程度的堵塞现象;悬浮物浓度的大小对深部介质的渗透性影响较弱。另外,当进-出水面的水头差△H较小(即水力坡度较小)时,物理堵塞主要发生在砂柱表层,当△H为19.25cm时,回灌结束后表层渗透系数降为初始的7%;随着△H的增大,物理堵塞深度和程度越大,当△H为48.64cm时,19~34cm深度砂层渗透系数变成初始的60%。     

环境水文地质研究中的C1~-示踪法

用CI一分析法可确定地下水污染途径，分析污染强度、海水入侵范围与程度、水动力场特征等问题。通过实验证实包气带中CI不易被吸附，不参与化学反应，包气带及地下水中极易迁移，形成天然的和人工的地下水运动示踪剂。     

砂质河床对悬浮物去除行为的试验研究

在用雨洪水回灌地下水前,利用天然河床滤除水中悬浮物,可以防止回灌时含水层的物理堵塞。为了系统研究悬浮物粒径、浓度及渗透流速对河床过滤效果的影响,设计和制作了水淘选装置,将河水表层沉积物按粒径分级后,用河砂作为过滤介质进行过滤,测定过滤介质的渗透性和悬浮物分布的变化。结果表明,中值粒径为12.9、7.3和2.3μm的悬浮物分别在表层(5cm)过滤介质内沉积,使该滤层的渗透性分别降低了91.3%、98.6%和99.7%后,可全部去除悬浮物。对于20μm以下的悬浮物,提高浓度会加快其沉积速率,使得悬浮物去除效果快速提高;而提高渗流速度,增加了悬浮物在过滤介质内迁移深度,不利于悬浮物的去除。     

麦哲伦海山区MA、MC海山玄武岩基岩的岩石学特征

麦哲伦海山区MA、MC海山玄武岩基岩的岩石学特征研究表明,岩性为蚀变玄武岩、橄榄玄武岩等;结构为基质具间隐、间往结构及拉斑玄武结构的斑状结构;矿物组成为斜长石、橄榄石、辉石及脱玻化玻璃等。按岩石化学成分分类属碱性玄武岩,而稀土分配模式属洋岛碱性玄武岩类型。     

东太平洋海隆1.5°N～1.5°S和南大西洋中脊13.2°S玄武岩物质组成

对东太平洋海隆(EPRⅠ区和Ⅱ区)和南大西洋中脊(SMAR)6个站位新鲜的玄武岩样品进行了岩石学及地球化学研究。结果显示,EPR玄武岩样品可分为辉石玄武岩、气孔玄武岩和玻基玄武岩3种类型,SMAR玄武岩样品主要为辉石玄武岩。EPR和SMAR玄武岩样品的标准矿物组合相同,均出现了石英和紫苏辉石标准矿物,为典型的拉斑玄武岩。EPRⅠ区和SMAR玄武岩表现出轻稀土富集的配分模式,可能受到了富集地幔源区(EMORB)的影响,其玄武岩可能形成于未经历早期熔融事件的富集地幔或部分熔融程度相对较低。EPRⅡ区玄武岩为正常型洋中脊玄武岩(N-MORB),其源区为经历了早期熔融事件的、亏损洋中脊地幔源区(DMM),且源岩部分熔融程度较高。EPRⅠ区与Ⅱ区不同的幔源特征说明东太平洋海隆地幔源区存在不均一性。     

中太平洋海山玄武岩的岩石学特征与年代

玄武岩在中太平洋海山分布广泛, 且普遍存在风化蚀变现象.对测区内玄武岩样品的岩石学特征研究表明, 玄武岩具斑状结构, 基质以间粒结构为主.斑晶矿物为基性斜长石、单斜辉石和伊丁石化橄榄石.基质矿物为斜长石、辉石、橄榄石、铁矿物、磷灰石、玻璃及次生矿物等. 各海山玄武岩同属碱性玄武岩系列, 并为钾质类型玄武岩, 它们的形成基本上处于同一地质构造环境中.稀土元素分析结果为轻稀土富集型, 轻重稀土在岩石形成过程中发生了不同程度的分异作用.CM5海山玄武岩比其他海山年代相对较老（60 Ma）.     

三门湾海岸带第四系地下水资源

利用三门湾海岸带最近施工完成的水文地质孔、工程地质孔和地下水碳（14C）测年以及前人的分析研究资料,对三门湾海岸带第四系分布、第四系承压含水层富水性和咸淡水资源分布、承压水年龄和可更新能力进行了深入研究。三门湾海岸带蛇盘滩涂围垦区第一承压含水层（组）富水性较好,绝大部分地区为淡水;宁海县长街镇区域承压水淡水资源总体呈“人”字型分布,北部的大湖?车岙港区域淡水主要分布在第一承压含水层（组）中,在大湖?下洋涂区域淡水主要分布在第二承压含水层（组）中。三门湾海岸带第四系承压水年龄普遍较老。蛇盘滩涂围垦区第一承压含水层地下水年龄为21 642～22 012 cal a BP,未受到后期海侵作用影响;长街下洋涂滩涂围垦区第二承压含水层地下水的年龄为35 052～45 439 cal a BP,部分地段受到后期海侵影响。在目前未开采利用条件下,承压水补给条件差、水资源更新性差。对于拟作为应急供水水源地靶区,应加强地下水资源管理。     

莱州湾海底地下水动态及影响机制研究

地下水监测及数理分析是地下水动态研究的主要方法。但目前海岸带地区多以陆域地下水监测为主,海域部分尤其具有多层含水层系统的海底地下水缺少直接监测数据。本研究通过海域钻孔ZK03与ZK08实时监测不同层位海底地下水动态以及海洋潮汐变化,结合其地层结构和沉积演化背景,分析莱州湾海底地下水动态特征并揭示其影响机制。研究结果表明,莱州湾海底地下水动态具有周期性和分层性特征;全新世含水层与海水关系密切,其海水入侵界面垂向上厚10 m左右。海底地下水分层与沉积地层划分大致相同,其动态特征是在地层结构及沉积演化环境影响下,降水、径流及潮汐驱动不同层深地下水间或地下水与海水间混合作用的结果。本文初步构建了海底地下水分布模式,探讨区域地下水与海水的相互作用关系。莱州湾海底地下水动态研究对于深入分析海(咸)水界面变化机制及探索海底地下水排泄具有推动作用。     

Simulation of groundwater level in a coastal aquifer

Abstract

The groundwater levels can have a significant impact on structures and infrastructures of coastal areas. The simulation of the hydraulic behavior of coastal aquifers is very important due to its specific boundary conditions. In this study, the groundwater level in the Bandar-e-Gaz coastal aquifer in the Gorgan Gulf region located in northern Iran is simulated using the MODFLOW mathematical model. The modeling of the coastal aquifer behavior carried out in two calibrations (steady and unsteady states). The validation periods (unsteady state), the mean absolute error (MAE) and mean bias error (MBE) were used to evaluate the results. The values of MAE and MBE criteria for the steady state were 0.31 (m) and –0.08 (m), while the average of these criteria in the unsteady state in calibration period were 0.46 and –0.39, and in the validation period were 0.42 (m) and –0.31 (m), respectively. The mentioned results confirm the precision of the model for the entire simulation period, they also indicate that the simulation has a limited underestimation behavior. Moreover, it shows that the precision of the results has a negligible variability, which means the simulation also has considerable reliability. The highest and lowest amount of error in the winter and summer seasons are in accordance with the lowest and highest seawater levels, and it shows the significant sea effect on the hydraulic behavior of the coastal aquifer.     

莱州湾南岸海水入侵变化趋势及成因分析

为了探讨滨海经济快速发展形势下莱州湾南岸海水入侵范围变化及其控制因素,利用2011—2015年4月份(枯水期)莱州湾南岸地下水潜水层TDS(可溶性固体总量)、Cl–质量浓度连续监测数据,结合历史资料,分析莱州湾南岸海水入侵分布特征。结果表明,近5年来研究区地下水Cl–质量浓度均值为13.4 g/L,呈由岸向内陆快速减小趋势;研究区海水入侵呈带状分布,2015年入侵线向内陆伸入超过45 km,入侵范围较1980年向陆扩张约11~30 km。通过对比分析得出,研究区年均降雨量、地下水位埋深及地下水超采面积与海水入侵面积呈显著线性相关,发现持续干旱气候、地下淡水超采是导致海水入侵扩张的主要因素,卤水开发、海水养殖及莱州湾沿岸河流拦蓄工程进一步导致海水入侵的加剧。     

Control of Phosphate Concentration through Adsorption and Desorption Processes in Groundwater and Seawater Mixing at Sandy Beaches in Tokyo Bay, Japan

Field observation was conducted to monitor phosphate concentrations in groundwater and seawater mixing at two sandy beaches in Futtsu and Miura in Tokyo Bay, Japan. Dissolved phosphate concentrations were measured along transects from fresh groundwater aquifer to seawater adjacent the beaches. The concentrations were often high (up to 46 µM) in fresh groundwater samples (Cl^– < 0.2). Coastal seawater, on the other hand, exhibited low phosphate concentrations (1.5 µM or less). Along the transects, phosphate generally displayed non-conservative behavior during mixing of fresh and saline waters in the aquifer; concentrations as high as 100 µM were found around the upper limit of seawater intrusion (Cl^– = 2). Laboratory experiments were executed to identify the processes that control the phosphate behavior in the mixing processes. The results revealed that adsorption-desorption processes by the aquifer sand particles could significantly control the phosphate concentrations in the groundwater. Furthermore, the adsorption and/or desorption was found to be a function of salinity; the equilibrium concentration of dissolved phosphate in slurry of sand and water was the highest in freshwater and decreased considerably in saline water. The extreme concentration of phosphate may be caused by release from sand particles coinciding with the rapid change in salinity with tide.     

Long-term water monitoring in two Mediterranean lagoons as an indicator of land-use changes and intense precipitation events (Adra,Southeastern Spain)

During recent historical times the Adra river delta, a detrital coastal aquifer of nearly 32 km² located in a semi-arid, mountainous area of SE Spain, has undergone different changes caused by human activity. Within this context, both the river dynamics in the plain and the geomorphology of the coastline have at various times resulted in the formation of small lagoons. At present only two small (<0.5 km²) lagoons exist, at the eastern edge of the aquifer, which, although closely surrounded by commercial market-garden greenhouses, are protected under international agreements. During the last 30 years of the twentieth century traditional agricultural irrigation techniques have undergone significant changes to improve their efficiency. Surface-water resources in the Adra river basin are regulated via the Beninar reservoir. In addition, the use of groundwater is increasing progressively. Both these factors affect the recharge of the coastal aquifer. To monitor these changes measurements of electrical conductivity and water level fluctuations have been recorded in these lagoons for the last 35 years (1975–2010). A comparison of the hydrochemical characteristics of the water in the lagoons and of the surrounding groundwater from 2003 to 2010 shows marked differences induced by the different hydrological dynamics in each lagoon, as well as by the hydrogeological impact of changes in land use in the delta. The increase in water demand is a consequence of the extension of irrigated areas from the fluvio-deltaic plain to its slopes, originally occupied by unirrigated crops. A reduction in irrigation return-flow is linked to the use of new irrigation techniques. These modifications affect both the recharge regime of the aquifer and its water quality. Moreover, extreme precipitation events, which are characteristic of Mediterranean semi-arid environments, can affect the lagoons’ hydrological dynamics to a considerable extent. One such example is the unusually rainy period from January to March 2010 (>600 mm). This event, along with other effects, has dramatically lowered the salinity of the water in both lagoons. This case study reveals the extreme vulnerability of deltaic environments and also how lagoons can reflect anthropogenic changes over the whole river basin.     

Wave-induced water table fluctuations,sediment transport and beach profile change: Modeling and comparison with large-scale laboratory experiments

Coastal groundwater systems can have a considerable impact on sediment transport and foreshore evolution in the surf and swash zones. Process-based modeling of wave motion on a permeable beach taking into account wave-aquifer interactions was conducted to investigate the effects of the unconfined coastal aquifer on beach profile evolution, and wave shoaling on the water table. The simulation first dealt with wave breaking and wave runup/rundown in the surf and swash zones. Nearshore hydrodynamics and wave propagation in the cross-shore direction were simulated by solving numerically the two-dimensional Navier–Stokes equations with a k–ε turbulence closure model and the Volume-Of-Fluid technique. The hydrodynamic model was coupled to a groundwater flow model based on SEAWAT-2000, the latter describing groundwater flow in the unconfined coastal aquifer. The combined model enables the simulation of wave-induced water table fluctuations and the effects of infiltration/exfiltration on nearshore sediment transport. Numerical results of the coupled ocean/aquifer simulations were found to compare well with experimental measurements. Wave breaking and infiltration/exfiltration increase the hydraulic gradient across the beachface and enhance groundwater circulation inside the porous medium. The large hydraulic head gradient in the surf zone leads to infiltration across the beachface before the breaking point, with exfiltration taking place below the breaking point. In the swash zone, infiltration occurs at the upper part of the beach and exfiltration at the lower part. The simulations confirm that beaches with a low water table tend to be accreted while those with a high water table tend to be eroded.     

Hydrogeological changes in coastal aquifers due to sea level rise

Global warming and climatic changes can lead to sea level rise (SLR) of dozens of cms over up-coming decades, along with groundwater permanent reserve losses (PRL). This study focuses on understanding the processes and estimating groundwater losses. A case study for such phenomena is Israel's Coastal aquifer. PRL estimation methodology is based upon a simple hydrogeological conceptual model. The results lead to estimation of two main components of an aquifer's PRL, and to key factors that can enhance or mitigate these losses. Such recommended measures as high-resolution topographic mapping and improved monitoring of sea level have been noted.     

Hydrogeology and geochemistry of near-shore submarine groundwater discharge at Flamengo Bay,Ubatuba, Brazil

Near-shore discharge of fresh groundwater from the fractured granitic rock at Flamengo Bay, Ubatuba, Brazil, is strongly controlled by the local geology. Freshwater flows primarily through a zone of weathered granite to a distance of 24 m offshore. In the nearshore environment this weathered granite is covered by about 0.5 m of well-sorted, coarse sands containing pore water with sea water salinity, with an abrupt transition to much lower salinity once the weathered granite is penetrated. Further offshore, low-permeability marine sediments contain saline porewater, marking the limit of offshore migration of freshwater. Freshwater flux rates based on tidal signal and hydraulic gradient analysis indicate a fresh submarine groundwater discharge of 0.17–1.6 m³/day per m of shoreline. Dissolved inorganic nitrogen and silicate are elevated in the porewater relative to seawater, and appeared to be a net source of nutrients to the overlying water column. The major ion concentrations suggest that the freshwater within the aquifer has a short residence time. Major element concentrations do not reflect in situ alteration of the granitic rocks, possibly because the alteration occurred prior to development of the current discharge zones, or because of large volumes of water discharge in this high rainfall region.     

白沙河地下水资源管理模型

针对白沙河地下水含水层的内部结构和本区开采特点以及已出现的环境问题，建立了地下水资源管理模型，确定了优化开采方案。该管理模型针对本区每年２个管理时段的长度及其开采量均不同的特点，导出了新的响应矩阵的公式。管理模型的建立有助于对该区地下水的合理开采。