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1.
Investigation for high yielding water wells in the khondalitic terrain (graneti ferrous silliminite gnesiss) is mostly faced with the problem of identification of the extent of the depth of kaolinisation of the aquifer. The traditional Vertical Electrical Sounding survey, Seismic Refraction survey and Very Low Frequency Electromagnetic survey could not identify the kaolinisation of the aquifer in the present investigations. The Two Dimensional (2D) Resistivity and Induced Polarization (IP) Imaging surveys are attempted for the identification of kaolinised layer and depth of kaolinisation. Number of 2D Resistivity and IP Imaging profiles were conducted near Chipurupally in Vizianagaram district of Andhra Pradesh, India along successful and failed wells located within short distances. Resistivity and IP measurements were carried out using an ABEM SAS 4000 Terrameter. The resistivity and I.P. images have provided a clear view of the thickness of the highly weathered zone (kaolinised zone) at both successful and failed wells. The highly weathered zone is identified with the resistivity values below 25 ohm.m. The depth of highly weathered material at failed well is extended about 8–10 m more deeper than the successful wells at some places to as much as 20 m more deep at some other places. This extended deeper kaolinisation of the aquifer is responsible for failure of wells. Layers having resistivities between 25–65 Ohm.m are identified as aquifer layers which are composed of moderately weathered and fractured khondalitic suit of rocks (Garnti ferrous sillimanite/biotite gneiss). Layers with resistivities greater than 65 Ohm.m are interpreted to have basement characteristics belonging to the granite gneiss. Interestingly IP imaging has not provided any greater insights in delineating the kaolinistion of the aquifer when compared to resistivity Imaging, in fact resitivity imaging has shown greater depths of kaolinisation than IP Imaging.  相似文献   

2.
Groundwater is a treasured earth’s resource and plays an important role in addressing water and environmental sustainability. However, its overexploitation and wide spatial variability within a basin and/or across regions are posing a serious challenge for groundwater sustainability. Some parts of southern West Bengal of India are problematic for groundwater occurrence despite of high rainfall in this region. Characterization of an aquifer in this area is very important for sustainable development of water supply and artificial recharge. Electrical resistivity surveys using 1-D and 2-D arrays were performed at a regular interval from Subarnarekha River at Bhasraghat (south) to Kharagpur (north) to map the lithological variations in this area. Resistivity sounding surveys were carried out at an interval of 2–3 km. Subsurface resistivity variation has been interpreted using very fast simulated annealing (VFSA) global optimization technique. The analysis of the field data indicated that the resistivity variation with depth is suitable in the southern part of the area and corresponds to clayey sand. Interpreted resistivity in the northern part of the area is relatively high and reveals impervious laterite layer. In the southern part of the area resistivity varies between 15 and 40 Ωm at a depth below 30 m. A 2-D resistivity imaging conducted at the most important location in the area is correlated well with the 1-D results. Based on the interpreted resistivity variation with depth at different locations different types of geologic units (laterite, clay, sand, etc.) are classified, and the zone of interests for aquifer has been demarcated. Study reveals that southern part of the area is better for artificial recharge than the northern part. The presence of laterite cover in the northern part of the area restricts the percolation of rainwater to recharge the aquifer at depth. To recharge the aquifer at depth in the northern part of the area, rainwater must be sent artificially at depth by puncturing laterite layers on the top. Such studies in challenging areas will help in understanding the problems and finding its solution.  相似文献   

3.
Bhadra  B. K.  Gor  Naresh  Jain  Ashish K.  Meena  Hansraj  Rao  S. Srinivasa 《Hydrogeology Journal》2021,29(8):2705-2724

The Great Rann of Kachchh (GRK) in Gujarat, India, is the largest salt desert in the world, which is usually filled with seawater ingression during high tide from the Arabian Sea. As a result, the soil gets saturated with saline water that has percolated down for several meters. Groundwater exploration in Rann area is a challenging task due to the prevailing hostile environment. For this purpose, multisensor satellite data have been used to delineate the palaeochannels in search of an alternate source of drinking water. In GRK, palaeochannels represent the zone of elevated fluvial sediments with respect to the surroundings. Evolutionary history of the palaeochannels indicates upliftment of GRK area during Allah Bund faulting. For assessing the groundwater potential of the palaeochannels, high-resolution electrical resistivity tomography (HERT) surveys have been carried out with the pole-dipole method. Electrical resistivity tomograms along 710 m traverses to a depth of 250 m in Dharmsala and Gainda area show higher-resistivity zones (medium to coarse sand with brackish water) below a thick low-resistivity layer (clay with saline water). A few exploratory drillings in the area confirm the existence of the palaeochannels, which act as a confined aquifer below 100 m depth. The artesian condition of the two drilled wells at Gainda and Khardoi along the northern boundary of GRK may be attributed to hydraulic gradient along the confined layers from the Tharparkar region in Pakistan. Thus, HERT is found to be a faster and more cost-effective geophysical survey technique for study of the deep aquifer.

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4.
辽河油田以开采上第三系地下水为主，已出现降落漏斗、水质恶化及咸水入侵等问题。文章应用Visual MODFLOW模型，建立了地下水流数值模拟模型，对不同开采方案下的地下水动态变化进行了预测和分析，确定了最佳开采量和最优开采布局。建议调减开采量和调整地下水开采布局以实现辽河油田地区水资源可持续利用。  相似文献   

5.
The overexploitation of groundwater in coastal aquifers is often accompanied by seawater intrusion, intensified by climate change and sea level rise. Heading long-term water quality safety and thus the determination of vulnerable zones to seawater intrusion becomes a significant hydrogeological task for many coastal areas. Due to this background, the present study focussed the established methodology of the GIS-based GALDIT model to assess the aquifer vulnerability to seawater intrusion for the Algerian example of the Quaternary coastal Collo aquifer. According to the result analysis overall, more than half of the total surface of the northern study area can be classified as highly vulnerable. Besides the coastline, the areas nearby the local wadis of Guebli and Cherka occur to be the most vulnerable in the region. In view of further map removal performance as well as single-parameter sensitivity analyses from a coupled perspective respectively the GALDIT parameters, distance from the shore (D) and aquifer hydraulic conductivity (A) have been found to be of key significance regarding the model results (mean effective weightings ~?18–19%). Overall, the study results provide a good approximation basis for future management decisions of the Collo aquifer region, including various perspectives such as identification of suitable settings for prospective groundwater pumping wells.  相似文献   

6.
With the increased demand for groundwater resulting from fast demographic growth, accelerated urbanization, economic and agricultural activity diversification, and the increase of per capita consumption, ground water resources, in particular in coastal regions, remain relatively low, compared to demand. The groundwater quality and piezometric variations result mainly from intensive exploitation, agricultural activities and the intrusion of seawater. This phenomenon is observed mostly in semi-arid areas, such as the oriental Sahel of Tunisia, where an apparent reduction in rainfall in recent years can be seen. Groundwater becomes overexploited especially as its natural recharge by rainwater does not succeed in maintaining the hydrologic balance. The imbalance between water demand and resources induces the degradation of the water quality. In such a case, the artificial recharge of water-table aquifers by water from dams is a credible alternative to improve the hydrodynamic and physicochemical conditions of the groundwater. Like most coastal aquifers, the Teboulba water-table aquifer is threatened by overexploitation for at least three decades. This threat appears by a considerable piezometric level drop and by water salinisation, due to seawater intrusion. Given this alarming situation, since 1971, artificial recharge through wells with surface water from a dam was tested in order to restore the water levels and to improve water quality. The piezometric and chemical surveys of the Teboulba aquifer permitted one to describe the temporal and spatial piezometric and geochemical conditions of the aquifer and to show the effect of the artificial recharge. Indeed, the artificial recharge undertaken since 1971 made the geochemical and piezometric conditions of the Teboulba aquifer improve. This example is a rare, well-documented case-study of the benefits of artificial recharge in a coastal aquifer, over the long term.  相似文献   

7.
In this study, the critical (or maximum) discharge rates before saline water enters a well were determined for vertical and horizontal wells in a freshwater aquifer which is separated from a static saline aquifer by a sharp interface. Flow around the well was solved by integration of a point sink solution along the well axis, and both the critical discharge rate and critical interface rise were determined through a comparison of the heads and vertical gradients at the saline–fresh water interface. The rates were determined for vertical and horizontal wells with various lengths and depths for different aquifer salinities. Results were generalized by drawing dimensionless type curves. The results showed that the dimensionless total critical discharge rates are higher for the longer horizontal wells and longer vertical wells with a certain bottom depth, and they almost linearly decrease with well depth at rates of 0.7–0.9. For the dimensionless well length of 0.2, the dimensionless total discharge rate of a horizontal well is about 0.1 more than that of a vertical well with the same length and well-top depth. Also, the critical discharge rates per unit length of well are inversely proportional to well length and remarkably higher for shallower wells. Additionally, the critical pumping rate is proportional to the salinity difference of the aquifers. These results were confirmed by comparison to existing solutions for vertical wells with dimensionless lengths of 0.2, 0.5 and 0.6, and for critical interface rises in the range of 0.75–0.9.  相似文献   

8.
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   

9.
Ongoing hydrogeological research aims to develop a correct management model for the Plio-Pleistocene multi-aquifer system of the Albegna River coastal plain (southern Tuscany, Italy); overexploitation of this aquifer for irrigation and tourism has caused seawater intrusion. The conceptual model is based on field and laboratory data collected during the 1995–2003 period. Meteoric infiltration and flows from the adjoining carbonate aquifer recharge the aquifer. Natural outflow occurs through a diffuse flow into the sea and river; artificial outflow occurs through intensive extraction of groundwater from wells. Water exchanges in the aquifer occur naturally (leakage, closing of aquitard) and artificially (multiscreened wells). The aquifer was represented by a three-dimensional finite element model using the FEFLOW numerical code. The model was calibrated for steady-state and transient conditions by matching computed and measured piezometric levels (February 1995–February 1996). The model helped establish that seawater intrusion is essentially due to withdrawals near the coast during the irrigation season and that it occurs above all in the Osa-Albegna sector, as well as along the river that at times feeds the aquifer. The effects of hypothetical aquifer exploitation were assessed in terms of water budget and hydraulic head evolution.  相似文献   

10.
近来,为缓解北京市日趋紧张的供水情况,需启用1995年建成的北京某应急备用地下水源地。该水源地建有30眼水井,属第四系河旁非承压含水层,当时静水位埋深为4m,单井平均出水量超过4000m3h。近年来由于各种原因,尤其是2003年该水源井出水量大幅减少的主要原因是含铁碳质化合物附着对井壁的堵塞。针对这一情况,通过试验确定了以强力正反冲洗活塞洗井工艺为核心的复合洗井方案,对17眼水井实施洗井处理,使井群出水量恢复到了建井初期的水平,取得了良好的效果。  相似文献   

11.
The Paluxy aquifer in north-central Texas is composed primarily of Lower Cretaceous clastics. This aquifer provides water for both domestic and agricultural purposes in the region. The study area for this investigation incorporates the outcrop and recharge areas, as well as the confined and unconfined portions of the aquifer. The purpose of this investigation is to develop a predictive modeling approach for evaluating the susceptibility of groundwater in the Paluxy aquifer to contamination, and then compare this susceptibility evaluation to water-chemistry data collected from wells completed within the aquifer. Using such an approach allows one to investigate the potential for groundwater contamination on a regional, rather than site-specific scale. Based on data from variables such as land use/land cover, soil permeability, depth to water, aquifer hydraulic conductivity and topography, subjective numerical weightings have been assigned according to each variables' relative importance in groundwater pollution susceptibility. The weights for each variable comprise a Geographic Information System (GIS) map layer. These map layers are combined to formulate the final pollution susceptibility map. Using this method of investigation, the pollution susceptibility map classifies 32% of the study area as having low pollution susceptibility, 41% as having moderate pollution susceptibility, 25% as having high pollution susceptibility, and 2% as having very high pollution susceptibility. When comparing these modeling results with water-chemistry data from wells within the Paluxy aquifer, the four wells with the highest concentration of nitrate contamination are all found within regions of very high pollution potential. This confirms the accuracy and usefulness of the predictive modeling approach for assessing aquifer pollution susceptibility. Received: 1 June 1999 · Accepted: 30 August 1999  相似文献   

12.
屋顶雨水回灌裂隙岩溶含水层连通示踪试验   总被引：1，自引：0，他引：1  
雨水回灌后对岩溶水的影响分析和效果需要对回灌井和下游的观测井监测数据说明。由于岩溶含水层中岩溶发育极不均匀,在测定地下水位并判定出地下水流向的基础上,连通示踪试验是选择与回灌井相对应的观测井的有效办法。用氯化钠作为示踪剂,监测不同测井不同埋深地下水电导率随时间变化的方法确定了岩溶水观测井选址、岩溶含水层的结构及水文地质条件。示踪试验结果表明,3#观测井(西院井)可用来监测雨水回灌效果,并计算出该地区的地下水势流速在9 m/h～20 m/h之间。该成果对北方地区岩溶含水层回灌和环境评价具有重要的参考价值。  相似文献   

13.
The Tel Aviv metropolitan region (200 km2), located on the sandy and phreatic Mediterranean Coastal Plain aquifer in Israel, is an example of a contaminated megasite that is additionally complicated by being part of a densely populated urban environment. Despite being a major source of fresh potable water, no dedicated aquifer monitoring systems exist. The vast majority of tested water supply wells (82% of 90 wells) were found to be contaminated with one or more chlorinated volatile organic compounds (Cl-VOCs) such as trichloroethene and tetrachloroethene, originating from multiple sources, including former industrial sites. Temporal variations in Cl-VOC concentrations in water supply wells were large and unpredictable. Such aquifer contamination requires immediate action in terms of aquifer management and municipal water distribution. To cope with temporal and spatial variations in contaminant concentrations in water supply wells in an area where monitoring wells are absent, aquifer impact areas were defined based on the concentration of the Cl-VOC contaminant in pumping wells that was greatest in relation to its drinking water standard over a 3-year period. Such a map can be used to define water supply treatment and municipal well monitoring requirements, until an adequate monitoring system is established.  相似文献   

14.
Geophysical and hydrogeological investigations have been carried out around Sawmills in Zimbabwe, Africa. The investigations are components of a larger investigation to assess the groundwater potential of the Karoo sedimentary basin with regards to supplying water to Bulawayo City. The Sawmills area was selected due to the availability of borehole logs indicating favourable stratigraphy for groundwater availability and due to the high yields from the aquifers measured from these boreholes. Data collected using two geophysical methods are presented here: transient electromagnetic (TEM) and continuous vertical electrical sounding (CVES) data. The data have also been processed using laterally constrained inversion (LCI). Because the CVES provides greater detail in the shallow subsurface, whereas TEM is more effective at depth, a more accurate image of the entire subsurface profile is provided based on using both methods. The results suggest that LCI of CVES and TEM data, in the subsurface at the required depths at Sawmills, is able to provide a substantially more accurate image of the subsurface than either method alone. The hydrogeological interpretation of the geophysical data is valuable for determining the depth to and thickness of the potential aquifer horizon(s) and for identifying the position of potential recharge zones.  相似文献   

15.
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   

16.
As in many other semi-arid regions, the Plio-quaternary aquifer of the eastern coast of Cap Bon peninsula (NE Tunisia) shows a parallel increase in overexploitation and mineralization of groundwater resources and so the water quality is deteriorating. Different methods using geochemistry (ions Na+, Cl−, Ca2+, Mg2+, Br−) and stable isotopes (18O, 2H) are compared with the hydrodynamic information for identifying the main processes involved in the increase of salinization. Along the coast, intrusion of seawater resulting from groundwater overexploitation is identified, but is not the only cause of qualitative degradation: the development of irrigation that induces soil leaching and transfer of fertilizers to groundwater over the whole aquifer extent is another major reason for the increase in salinization. A total of 48 groundwater wells were sampled to obtain additional information on the hydrochemical characteristics of the groundwater defined in previous studies.  相似文献   

17.
Azraq Oasis in the eastern Jordanian desert is an important freshwater resource of the country. Shallow groundwater reserves are heavily exploited since the 1980s and in consequence the groundwater table dropped significantly. Furthermore, some wells of the major well field drilled into the shallow aquifer show an increasing mineralization over the past 20 years. A previous study using conventional tracers did not result in a satisfactory explanation, from where the salt originates and why only a few wells are affected. In this study, the application of dissolved noble gases in combination with other tracer methods reveals a complex mixing pattern leading to the very localized salinization within the well field. It is found that primarily the wells affected by salinization 1) contain distinctly more radiogenic 4He than the other wells, indicating higher groundwater age, and 2) exhibit 3He/4He ratios that argue for an imprint of deep fluids from the Earth's mantle.However, the saline middle aquifer below is virtually free of mantle helium, which infers an upstream from an even deeper source through a nearby conductive fault. The local restriction of the salinization process is explained by the wide range of permeabilities of the involved geologic units. As the wells abstract water from the whole depth profile, they initially pump water mainly from the well conductive top rock layer. As the groundwater table dropped, this layer fell progressively dry and, depending on the local conductivity profile, some wells began to incorporate more water from the deeper part of the shallow aquifer into the discharge. These are the wells affected by salinization, because according to the presented scheme the deep part of the shallow aquifer is enriched in both salt and mantle fluids.  相似文献   

18.
A novel study on using geoelectrical resistivity, soil property, and hydrogeochemical analysis methods for delineating and mapping of heavy metal in aquifer system is presented in this paper. A total of 47 surveys of geoelectrical resistivity with Wenner configuration were conducted to determine the subsurface and the groundwater characteristics. The groundwater sample from 53 existing wells and 2 new wells has been analyzed to derive their water chemical content. The chemical analysis was done on the soil sample obtained from new two wells and from selected locations. The water and soil chemical analysis results from the new two wells were used as calibration in resistivity interpretation. The occurrence of heavy metal in aquifer system was expected to detect using the geoelectrical resistivity survey for the whole study area. The result of groundwater analysis shows that the groundwater sample contains a relatively low concentration of Fe (<?0.3 mg/L) elongating from the south up to the middle region. While in the middle and the northwestern, Fe concentration is relatively high (around 12 mg/L). Chemical analysis of soil sample shows that in the lower resistivity zone (<?18 Ωm), Al and Fe concentrations are comparatively high with an average of 68,000 and 40,000 mg/kg, respectively. Starting from the middle to the northwestern zone, the resistivity value appears to be low. It is definitely caused by higher Al and Fe concentration within the soil, and it is supported also by lower total anion content in the groundwater. While the resistivity value of more than 40 Ωm in aquifers is obtained in the zone which Fe concentration is relatively lower in the soil but not present in the groundwater. Correlation Fe concentration in the soil and Fe concentration in the groundwater sample shows the trend of positively linear; however, the Al concentration in soil has no correlation with Al content in groundwater. Finally, the probability of high heavy metal zone in the aquifer system is easily delineated by the distribution of geoelectrical resistivity presented in depth slice shapes which extend from the Boundary Range Composite Batholith in the north to the northwest.  相似文献   

19.
This study describes the groundwater quantity and quality conditions in the Damghan aquifer in Iran. The quantitative analysis of data obtained from observation wells indicates overexploitation of groundwater during recent years, which has resulted in deterioration of water quality. The mean water level has declined about 7.4 m between years of 1966 and 2010. The hydrochemical facies of water collected from sampling wells were investigated though Piper and Chadha diagrams, and the general dominant type of water in the study area was determined as Na-Cl. The quality assessment examined the suitability of groundwater for drinking and irrigation purposes. Compared to the World Health Organization (WHO) guidelines for drinking water, all regions were found to have unpotable groundwater. Furthermore, unsuitability of groundwater for agricultural applications due to high salinity was observed through analysis of major quality indicators. The saltwater intrusion was investigated by ionic ratio analyses and was determined to be the main factor contributing to high salinity and deterioration of the groundwater quality in the Damghan basin.  相似文献   

20.
Aquifer overexploitation: what does it mean?   总被引：9，自引：0，他引：9  
Groundwater overexploitation and aquifer overexploitation are terms that are becoming common in water-resources management. Hydrologists, managers and journalists use them when talking about stressed aquifers or some groundwater conflict. Overexploitation may be defined as the situation in which, for some years, average aquifer abstraction rate is greater than, or close to the average recharge rate. But rate and extent of recharge areas are often very uncertain. Besides, they may be modified by human activities and aquifer development. In practice, however, an aquifer is often considered as overexploited when some persistent negative results of aquifer development are felt or perceived, such as a continuous water-level drawdown, progressive water-quality deterioration, increase of abstraction cost, or ecological damage. But negative results do not necessarily imply that abstraction is greater than recharge. They may be simply due to well interferences and the long transient period that follow changes in the aquifer water balance. Groundwater storage is depleted to some extent during the transient period after abstraction is increased. Its duration depends on aquifer size, specific storage and permeability. Which level of "aquifer overexploitation" is advisable or bearable, depends on the detailed and updated consideration of aquifer-development effects and the measures implemented for correction. This should not be the result of applying general rules based on some indirect data. Monitoring, sound aquifer knowledge, and calculation or modelling of behaviour are needed in the framework of a set of objectives and policies. They should be established by a management institution, with the involvement of groundwater stakeholders, and take into account the environmental and social constraints. Aquifer overexploitation, which often is perceived to be associated with something ethically bad, is not necessarily detrimental if it is not permanent. It may be a step towards sustainable development. Actually, the term aquifer overexploitation is mostly a qualifier that intends to point to a concern about the evolution of the aquifer-flow system in some specific, restricted points of view, but without a precise hydrodynamic meaning. Implementing groundwater management and protection measures needs quantitative appraisal of aquifer evolution and effects based on detailed multidisciplinary studies, which have to be supported by reliable data. Electronic Publication  相似文献   

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