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1.
《Applied Geochemistry》2006,21(1):83-97
Groundwater in the Gwelup groundwater management area in Perth, Western Australia has been enriched in As due to the exposure of pyritic sediments caused by reduced rainfall, increased groundwater abstraction for irrigation and water supply, and prolonged dewatering carried out during urban construction activities. Groundwater near the watertable in a 25–60 m thick unconfined sandy aquifer has become acidic and has affected shallow wells used for garden irrigation. Arsenic concentrations up to 7000 μg/L were measured in shallow groundwater, triggering concerns about possible health effects if residents were to use water from household wells as a drinking water source. Deep production wells used for public water supply are not affected by acidity, but trends of progressively increasing concentrations of Fe, SO4 and Ca over a 30-a period indicate that pyrite oxidation products extend to the base of the unconfined aquifer. Falling Eh values are triggering the release of As from the reduction of Fe(III) oxyhydroxide minerals near the base of the unconfined aquifer, increasing the risk that groundwater used as a drinking water source will also become contaminated with high concentrations of As.  相似文献   

2.
In the Red River Delta, situated in the northern part of Vietnam, nearly its entire population depends solely on groundwater for daily water consumptions. For this reason, groundwater quality assessments must be carefully carried out using hydrogeochemical properties, to ensure effective groundwater resource planning for the Delta’s present and future groundwater use. In this study, the spatial and seasonal changes in the hydrogeochemical characteristics of groundwater in the two main aquifers of the RRD were investigated by analyzing the physicochemical data obtained in 2011 from 31 conjunctive wells in the Delta’s Holocene unconfined aquifer (HUA) and Pleistocene confined aquifer (PCA) using the Piper diagram and the Gibbs diagram. Results of the data analysis show that the groundwater in both aquifers in the upstream area of the delta is dominated by the [Ca2+–HCO3−] water-type, while the [Na+–Cl−] dominates along the middle-stream and downstream areas. Seasonal changes in the hydrogeochemical facies in both aquifers, comparing the results for the dry and the rainy seasons, were detected in about one third of the sampling wells, which were mainly located at the upstream portion of the Delta. The hydrogeochemical facies of HUA were different from that of PCA by about 45% of the sampling wells in both the dry and the rainy seasons, which were found mostly in the upstream and middle-stream areas.  相似文献   

3.
Slurry walls are non-structural barriers that are constructed underground to impede groundwater flow or manage groundwater control problems. The study area is in the Piemonte plain (Italy), close to the River Po. Quarrying works carried out below the piezometric surface created two big quarry lakes. The local groundwater system is characterized by a lower semi-confined aquifer, which is overlain by a semi-permeable bed of clayey peat (aquitard) and an upper unconfined aquifer. Locally, the peat fades away and the granulometry of this horizon becomes silty sandy. A planned enlargement of the quarry will increase the size and depth of the quarry lakes. So the aquitard bed between the two aquifers will be damaged, creating a mixing rate of groundwater. Such a procedure would not be compatible with the presence of two municipal wells upstream from the quarries. Consequently, the installation of a vertical diaphragm (slurry wall) is recommended to separate the aquifers and to act as a filter for the groundwater flowing from the unconfined to the semi-confined aquifer. To predict the consequences caused by the installation of the vertical diaphragm separating the unconfined aquifer and the semi-confined one, a specifically adjusted finite-difference model was used. The model showed a maximum rising of the water table equal to 12 cm, just upstream of the diaphragm and for a distance of about 100 m, and a maximum lowering of 2 cm just downstream of the diaphragm. However, the slurry wall would not cause any change in the piezometric head in the area where there are municipal wells and, hence, will not have any negative effect on the functionality of the municipal wells. Moreover, the migration of water from the unconfined aquifer through the vertical diaphragm will stimulate a series of attenuation and auto-depuration processes of eventual contaminants. These processes are due to the higher crossing time that the groundwater flow takes to go through the vertical barrier (t a = 96.5 days, whereas for the horizontal semi-permeable layer t a = 9.6 days). So, the vertical diaphragm can be a resolutive element, representing a mediation and separation factor between the unconfined and the semi-confined aquifers along the border of the quarrying areas, and a protective barrier for the water quality of the quarry lake and the semi-confined aquifer.  相似文献   

4.
An overview is presented of existing groundwater-age data and their implications for assessing rates and timescales of recharge in selected unconfined aquifer systems of the United States. Apparent age distributions in aquifers determined from chlorofluorocarbon, sulfur hexafluoride, tritium/helium-3, and radiocarbon measurements from 565 wells in 45 networks were used to calculate groundwater recharge rates. Timescales of recharge were defined by 1,873 distributed tritium measurements and 102 radiocarbon measurements from 27 well networks. Recharge rates ranged from?<?10 to 1,200?mm/yr in selected aquifers on the basis of measured vertical age distributions and assuming exponential age gradients. On a regional basis, recharge rates based on tracers of young groundwater exhibited a significant inverse correlation with mean annual air temperature and a significant positive correlation with mean annual precipitation. Comparison of recharge derived from groundwater ages with recharge derived from stream base-flow evaluation showed similar overall patterns but substantial local differences. Results from this compilation demonstrate that age-based recharge estimates can provide useful insights into spatial and temporal variability in recharge at a national scale and factors controlling that variability. Local age-based recharge estimates provide empirical data and process information that are needed for testing and improving more spatially complete model-based methods.  相似文献   

5.
In 1980, the Arizona legislature passed the Groundwater Management Act (GMA), creating the active management areas (AMAs) to protect shared groundwater resources and to control severe overdrafts occurring in many parts of the state. With the 30-year anniversary of the GMA approaching, this article addresses the question: Have there been notable changes in the trends in observed groundwater levels in the AMAs from before enactment of the GMA until present? New tools developed for the US Geological Survey’s National Water Availability and Use Pilot Program are used to analyze and present trends in observed groundwater level data. Trends in groundwater levels in the AMAs were investigated for 10-year time periods from 1970 through 1999 and an 9-year period from 2000–2008. Results indicate that the number of wells with rising trends in water levels increased and the number of wells with falling trends in water levels decreased during the early decades after passage of the GMA in the most-populated Phoenix and heavily agricultural Pinal AMAs. However, these trends in water levels are reversed during the 1995–2004 time period. The value of trend analyses would be improved by consistent groundwater-level monitoring in both developed and undeveloped areas of the region.  相似文献   

6.
Coastal aquifers are considered as major sources for freshwater supply worldwide, especially in arid zones. The weak rainfall as well as the intensive extraction of groundwater from coastal aquifers reduce freshwater budget and create local water aquifer depression, causing both seawater intrusion and a threat to groundwater. This phenomenon was observed in the Jerba Island which is located in southeast Tunisia. Jerba??s unconfined aquifer shows high values of groundwater salinity reaching, locally, 17?g/l and a strong contrast between some zones of the aquifer. High pumping rates and weak recharge disturb the natural equilibrium between fresh and saline water causing water salinization in most areas of the island. This study aims at establishing the salinity map of the aquifer and identifying the origin of groundwater salinization. The salinity map shows that zones characterized by low groundwater salinity are located in the center of the study area. High groundwater salinities are observed near the coast and in some parts having low topographic and piezometric levels. Groundwater geochemical characterization, and Br/Cl and Na/Cl ratios suggest that the origin of abnormal salinity is seawater intrusion. Considering groundwater salinity values and Br concentrations, a seawater intrusion map is established. It shows that many areas of the unconfined aquifer are contaminated by mixed groundwater and seawater. The statistical analysis demonstrates that high mineralization of the groundwater is due to gypsum and carbonate dissolution coupled with the mixed groundwater and seawater in many areas.  相似文献   

7.
郭敏  万军伟  江峰  黄琨 《地球科学》2017,42(1):155-160
目前对潜水含水层地下水潮汐效应和水文地质参数求解方法的研究相对较少.通过对福建古雷半岛滨海潜水含水层地下水潮汐效应和海水潮汐动态的观测, 运用Fourier频谱分析方法确定了研究区海水潮汐波动方程(波动特征参数), 并以此作为地下水的边界条件, 推导了潜水含水层地下水潮汐效应的波动方程, 利用最小二乘法以地下水水位波动观测值为目标函数对潜水含水层的渗透系数与重力给水度的比值进行了反演识别, 为类似地区水文地质参数的确定提供了借鉴, 也为该区后续地下水中溶质迁移规律的研究奠定了基础.   相似文献   

8.
黑龙江建三江地区地下水动态趋势突变点分析   总被引：2，自引：0，他引：2  
农业区地下水动态规律是农业水资源管理的重要依据。采用双向回归突变分析方法研究黑龙江建三江地区(19922011)地下水埋深序列的趋势突变点,结合水稻面积增长数据进行对比分析,找出地下水动态趋势突变与灌溉面积的响应关系,同时运用标准化降水指数(SPI)方法来分析研究地下水动态趋势突变与降水之间的响应关系。结果表明:建三江地区地下水水位的下降趋势具有明显的突变特征,整体上呈"快慢快"的特点,趋势突变时间多发生在20002001年间和20062007年间;在第一阶段和第二阶段,地下水水位下降趋势受水稻种植面积与降水影响,第三阶段主要受水稻种植面积增长的控制。  相似文献   

9.
The use of isotope tracers as a tool for assessing aquifer responses to intensive exploitation is demonstrated and used to attain a better understanding of the sustainability of intensively exploited aquifers in the North China Plain. Eleven well sites were selected that have long-term (years 1985–2014) analysis data of isotopic tracers. The stable isotopes δ18O and δ2H and hydrochemistry were used to understand the hydrodynamic responses of the aquifer system, including unconfined and confined aquifers, to groundwater abstraction. The time series data of 14C activity were also used to assess groundwater age, thereby contributing to an understanding of groundwater sustainability and aquifer depletion. Enrichment of the heavy oxygen isotope (18O) and elevated concentrations of chloride, sulfate, and nitrate were found in groundwater abstracted from the unconfined aquifer, which suggests that intensive exploitation might induce the potential for aquifer contamination. The time series data of 14C activity showed an increase of groundwater age with exploitation of the confined parts of the aquifer system, which indicates that a larger fraction of old water has been exploited over time, and that the groundwater from the deep aquifer has been mined. The current water demand exceeds the sustainable production capabilities of the aquifer system in the North China Plain. Some measures must be taken to ensure major cuts in groundwater withdrawals from the aquifers after a long period of depletion.  相似文献   

10.
The recharge sources and groundwater age in the Songnen Plain, Northeast China, were confirmed using environmental isotopes. The isotopic signatures of the unconfined aquifers in the southeast elevated plain and the north and west piedmont, cluster along local meteoric water lines (LMWLs) with a slope of about 5. The signature of source water was obtained by the intersection of these LMWLs with the regional meteoric water line (RMWL). This finding provides evidence that the recharge water for these areas originate from the Changbai Mountains and the Low and High Hingan Mountains, respectively. Groundwater in the unconfined aquifer in the low plain yields a LMWL with a slope of 4.4; its nitrate concentration indicates the admixture of irrigation return flow. The δ-values of the unconfined aquifer in the east elevated plain plot along the RMWL, reflecting recharge by local precipitation. The mean residence time of groundwater in these aquifers is less than 50?years. However, the 14C age of the groundwater in the confined Quaternary aquifer ranges from modern to 19,500?years, and in the Tertiary confined aquifer from 3,100 to 24,900?years. Modern groundwater is mainly recharged to the Quaternary confined aquifer on the piedmont by local precipitation and lateral subsurface flow.  相似文献   

11.
吴庆  郭永丽  滕彦国  左锐  姜光辉  罗飞 《水文》2017,37(1):19-24
基于过程模拟的地下水污染预警是基于包气带和饱和带过程模拟的耦合实现的,且融合了涵盖整个地下水系统的四个预警指标。选取浑河冲洪积扇的李官堡水源地为例,基于Hydrus-1D和Visual Modflow分别进行包气带过程模拟和饱和带过程模拟,针对潜层和承压层的复杂程度分别制定了各自的预警临界值;经分析可知,随着时间的推移,地表污染物持续进入到地下水中,污染晕范围不断扩大,地下水中最大浓度值和水源井浓度值也持续增加,且承压含水层的预警级别要高于潜水含水层;同时基于潜层和承压层中污染物最大浓度值与时间分别近似呈线性关系和指数关系可进行长时间尺度的预警;并提出了零级预警区和一级预警区管理措施以监测和预防为主,二级预警区、三级预警区和四级预警区管理措施以控制和监测为主。  相似文献   

12.
为了给吉林省白城市地下水资源合理开发利用提供科学依据,运用地下水模拟技术对白城市地下水位变化趋势进行预测。首先在分析研究区水文地质条件的基础上建立水文地质概念模型,将含水系统概化为潜水含水层、越流层和承压含水层,并确定了系统的边界条件。运用地下水模型软件(GMS)对研究区地下水流进行了模拟和预测,预测结果表明在扩大开采的情况下,潜水含水层水位总体下降约1~2 m;随着开采量的增加和时间的增长,含水层在洮儿河扇形地、洮南、研究区东北部、镇赉、大安南部等地相继出现疏干现象,最大降幅达5~6 m。承压含水层在大安南部、镇赉北部等地水位下降较大,但是流场整体降幅不大,总体降幅在0.5 m以内。最后提出了地下水合理开发利用建议。  相似文献   

13.
The potential for contamination of groundwater in an over-exploited system led to this investigation on aspects of aquifer vulnerability in the Toluca Basin, Mexico. This study involved the use of various hydrogeological, geochemical and isotopic tools to better understand the susceptibility to contamination where heavy groundwater extraction along with industrial extensive development is concentrated. Geochemical and isotopic analyses of groundwater from production wells along the mountain boundary show little evidence of contamination at present time. Radiocarbon and tritium data collected in piezometers and wells penetrating the Lower basalt aquifer indicate that the groundwater is of varying age and quality. These data, in addition to stable isotope and chemical data also indicate evidence of contamination in the Lower aquifer; which could be associated with fast recharge in the mountains or injection of waste water by illegal wells. Evidence found in this study of low downward gradients in the valley fill sediments and the presence of low permeability aquitard deposits suggest that the aquifer system is currently not highly threatened by surface sources of contamination. However, where urban and industrial development occurs, in the centre of the valley and along the flanks of the Basin, the vulnerability of the aquifer system increases significantly.  相似文献   

14.
A significant component of domestic demand for water of urban areas located in the Gangetic plains is met by heavy pumping of groundwater. The present study is focused on the Patna municipal area, inhabited by 17 million people and spanning over 134 km2, where entire urban water demand is catered from pumping by wells of various capacities and designs. The present study examines the nature of the aquifer system within the urban area, the temporal changes in the water/piezometric level and the recharge mechanism of the deeper aquifers. The aquifer system is made up of medium-to-coarse unconsolidated sand, lying under a ~40-m-thick predominantly argillaceous unit holding 8- to 13-m-thick localised sand layers and continues up to 220 m below ground. Groundwater occurs under semi-confined condition, with transmissivity of aquifers in 5,500–9,200 m2 day?1 range. Hydraulic head of the deeper aquifer remains in 9–19 m range below ground, in contrast to 1–9 m range of that of the upper aquitard zone. The estimated annual groundwater extraction from the deeper aquifer is ~212.0 million m3, which has created a decline of 3.9 m in the piezometric level of the deeper aquifer during the past 30 years. Unregulated construction of deep tube wells with mushrooming of apartment culture may further exacerbate the problem. The sand layers within the aquitard zone are experiencing an annual extraction of 14.5 million m3 and have exhibited stable water level trend for past one and half decades. This unit is recharged from monsoon rainfall, besides contribution from water supply pipe line leakage and seepage from unlined storm water drains.  相似文献   

15.
About 40% of the water supply of Cairo, Egypt, is drawn from a groundwater reservoir located southeast of the Nile Delta. Several thousand shallow wells supply drinking water to the farmers from the same groundwater reservoir, which is recharged by seepage from Ismailia canal, the irrigation canal network, and other wastewater lagoons in the same areas. Sewage water lagoons were located at the high ground of the area, recharging contaminated water into the aquifer. Since the groundwater in this area is used for drinking purposes, it was decided to treat the sewage water recharging the aquifer for health reasons. In this paper a solution to the problem is presented using an injection well recharging good quality water into the aquifer. A pumping well located at a distance downstream is used to pump the contaminated water out of the aquifer. A three-dimensional solute transport model was developed to study the concentration distribution with remediation time in the contaminated zone.  相似文献   

16.
The scarcity of surface water resources in arid and semi-arid regions from North African countries contributes to the considerable increase of groundwater exploitation, which leads to the development of hydrogeological studies. However, due to the lack of hydrodynamic data in these regions, these studies focus more and more on the geochemical and environmental isotope techniques to insure a better understanding of the hydrodynamic functioning of subsurface systems. In this study, which interests an important unconfined aquifer in central Tunisia, tritium data and chloride mass balance (CMB) method were applied in order to (1) understand the mode of recharge of this aquifer and (2) obtain a reliable estimation of its recharge amount as well as (3) estimate its annual renewal rate. It has been demonstrated that the shallow groundwaters are classified into two groups according to their tritium contents. The first group includes wells located mainly downstream and highlights the significant role of the post-nuclear lineal recharge through Wadis courses. The second group encloses wells located practically overall the rest of the basin and refers to relatively modern waters originated from areal recharge of present-day rainfall. Based on the CMB method, the recharge to this unconfined aquifer is estimated to 31.7 mm year−1, which corresponds to 10.5% of the total rainfall. The annual renewal rate of groundwater, evaluated based on the tritium contents, is up to 16%.  相似文献   

17.
Analysis of tidal effects on aquifer systems plays an important role in coastal aquifer management owing to various hydrological, engineering and environmental problems in coastal areas. Using the real-world data of unconfined and confined aquifers, a data-driven approach is presented in this study for the analysis of tide–aquifer interaction in coastal aquifers. Six analytical tide–aquifer interaction models were selected which take into account the effects of vertical beach, sloping beach, tidal loading, aquifer leakage, outlet capping, and combined leakage and outlet capping on tide-induced groundwater fluctuations. The tide–aquifer interaction datasets were obtained from the Konan groundwater basin (unconfined aquifer) of Japan and the Dridrate groundwater basin (confined aquifer) of Morocco. The analysis of the results obtained by the sloping beach model revealed that for a given beach slope, the amplitude of groundwater level increases with an increase in aquifer diffusivity and a decrease in aquifer thickness. However, no significant effect of beach slope was observed in this study at unconfined sites for all the datasets. The influence of tidal loading was found to be considerably less for all the three confined sites. Further, the analysis of the results of the leakage model indicated that with an increase in leakage into the aquifer, the amplitude of groundwater level as well as the phase shift (time lag) decreases. Of all the confined and unconfined datasets, only two confined sites were found to be affected by outlet capping. Overall, it is concluded that the coastal beach bordering the Konan basin is not significantly sloping, the contribution of tidal loading to tide-induced groundwater fluctuations in the Dridrate aquifer is not appreciable, and that the aquifer leakage and outlet capping do not exist at the unconfined sites under investigation.  相似文献   

18.
北京平原地下水水位监测网优化   总被引：10，自引：0，他引：10  
文章在北京市地下水水位监测现状基础上,分潜水和承压水对北京平原地下水监测网的监测密度和监测频率进行了优化设计。主要采用编制地下水动态类型图的方法进行了地下水水位监测网的优化,克里金插值法能定量评价依据监测网观测值绘制的地下水水位等高线的精度,因而可以用来评价监测优化结果。并根据时间序列分析和统计检验提供的定量标准优化了地下水水位监测频率。优化后,北京平原共有监测孔400眼,其中利用原有监测孔300眼,新设计监测孔100眼,手工监测频率由原来的每月6次优化为每月1次,专项高频率监测可以由地下水自动监测仪实现。文中还对地下水自动监测仪(DIVER)的监测结果和手工监测结果进行了对比评价,提出了地下水水位监测网的维护、管理措施和信息发布方式。  相似文献   

19.
鲁北平原地下水的劣变特征与可持续利用的对策   总被引：2，自引：0，他引：2  
2005年相对于20世纪70年代,鲁北平原开采机井数由9．29万眼增至28．76万眼．浅层水、深层水开采量分别增加了近2倍和3．76倍。长期超量开采和不合理的开采布局,使地下水水位持续下降、含水层疏干体积不断增加、地下水位降落漏斗持续扩展．并产生地面沉降、成水入侵等环境地质问题。采取农业节水、调整工业开采强度布局、加强浅层水均衡开发利用、地表水与地下水联合调蓄、本地劣质水资源化、保护和涵养深层地下水资源等举措,修复和涵养鲁北平原超采区的深层地下水系统势在必行。  相似文献   

20.
The combined effects of low rainfall, groundwater withdrawal in excess of 300 GL/year and reduced recharge in areas covered by pine plantations has caused the water table in a sandy unconfined aquifer on the Gnangara Mound in Western Australia to drop by up to 5 m and aquifer storage to decline by about 500 GL over the last 20 years. Groundwater has become acidic in areas of high drawdown, with pH values typically being less than 5.0 at the water table, and elevated concentrations of SO4 2?, Al, Fe, Zn, Cu, Ni and Pb. Trends of increasing acidity and base cation concentrations in deep water supply wells in the Mirrabooka wellfield indicate that about 0.7 keq/ha/year of base cations are being leached from soil within cones of depression of pumping wells. These results indicate that the assessment of the sustainable yields of aquifers under conditions of low rainfall needs to consider geochemical interactions between groundwater, aquifer sediments, soils and vegetation, and not be just based on aquifer hydraulics and water-balance changes.  相似文献   

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