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1.
Detailed local geological, geophysical, and hydrogeological investigations were carried out for the alluvial aquifer in the Kangavar basin, West Iran to delineate the architecture of different subsurface geological horizons using lithologs and generated vertical electrical sounding (VES) data. An attempt has also been made to estimate aquifer transmissivity from resistivity data. Forty VESs were recorded with the Schlumberger electrode configuration in the study area; 28 of these were selected for evaluation. The maximum current electrode spacing was 400–500 m. The data obtained were interpreted by computer iterative modeling with curve matching for calibration purposes. In order to ascertain the subsurface geological framework, the general distribution of resistivity responses of the geological formations was obtained and geoelectrical sections along a number of lines were prepared. Probable aquifer horizons from these sections were identified. The transmissivity of the unconfined aquifer was computed by determining the Dar-Zarrouk parameters (longitudinal unit conductance and transverse unit resistance) and were compared with the actual field transmissivity. The results showed a direct relation between aquifer transmissivity and modified transverse resistance.  相似文献   

2.
The applicability of geophysical techniques has been examined for evaluating aquifer properties like transmissivity and hydraulic conductivity of coastal aquifers, Tuticorin, Tamil Nadu. The pumping test data of 10 wells are interpreted by using forward modelling to obtain the aquifer characteristics in the study area. The available vertical electrical soundings (VES) data in the vicinity of the sites of pumping test have been interpreted; and true resistivity and thickness are determined at each site in the study area. Empirical relationships are established for estimating the hydraulic parameters from the electrical data.  相似文献   

3.
The Yamuna flood plains spread across the northern part of Indian subcontinent is home to millions of people. The ever-growing population in these plains make it difficult to sustain the demand of freshwater resources. However, the productive aquifers of flood plains could provide solution for these issues. In this context, it is necessary to understand the aquifer characteristics. Thus, the paper attempts to characterize the aquifer in Palla area of the flood plain using integrated approach. Besides, grain size analysis and site-litholog study, the nature of aquifer material was also ascertained from bulk mineralogy of the sediments using X-Ray Diffraction. The aquifer parameters were estimated with help of long duration pumping test data. Moreover, the effect of pumping on salinity variation and hydrochemical facies evolution was also examined. The sand dominant, unconfined aquifer was estimated to have horizontal hydraulic conductivity in the range of 25 m/day and vertical hydraulic conductivity of 6–7 m /day. While the specific yield of the aquifer was estimated in the range of 0.07–0.08. It is observed that under conducive active flood plain environment, the given sand mineralogy at the site does not allow salinity increase in groundwater even after more than a decade of groundwater pumping. In fact, over years, hydrochemical facies have evolved towards Bicarbonate type. These things put together make the active flood plain aquifer a sustainable groundwater resource.  相似文献   

4.
The physical explanation is presented for two types of theoretical equations which encompass a direct and an inverse relationship between the hydraulic conductivity and electrical resistivity of an aquifer. Using the theory of direct current (DC) resistivity prospecting, it is shown that a direct relation exists if the bulk of the current flow is in the vertical direction, whereas the inverse relation exists if the current is in the horizontal direction. Consequently, the relation in question is direct in the case of a relatively conducting basement and inverse in the case of a comparatively resistive basement. Then, the aquifer hydraulic conductivity for the hydrogeologically well-studied area of Krauthausen in Germany is estimated by two different techniques using surface geoelectrical data. The estimated values are compared with those conventionally determined by a pump test experiment and it can be concluded that the estimation is better whenever geoelectrical data are used.  相似文献   

5.
Electrical geophysical surveys in the mode of vertical electrical soundings (VES) and continuous vertical electrical soundings (CVES) were conducted in the León-Chinandega plains, northwestern Nicaragua, in order to obtain detailed information about the geometry of the different hydrogeological layers in the aquifer and depth to the basement. A total of 51 VES were carried out within the plains. The results show a complex structure towards the north east of the area, and the southwestern part of the plains presents a smoother stratification. The geoelectrical measurements and borehole information indicate that the basement topography is characterized by hills and deep valleys with highly variable basement depths. Fifty CVES where done in a smaller area in the center of the plain. The resistivity data yielded considerable information revealing the existence of two main geo-electrical units. The combined interpretation of geological and geophysical data shows an environment typical of sedimentary volcanic coastal plains. The information collected during this investigation provides valuable data for estimating the fresh-water resources of the León-Chinandega aquifer system and for development of a groundwater management plan.  相似文献   

6.
陈晨  文章  梁杏  李霞 《地球科学》2017,42(5):727-733
含水层参数对于定性分析区域地下水资源评价、数值模拟及预报、开发利用与保护及科学管理具有重要意义,而江汉平原水文地质参数求解的研究却相对较少.2015年江汉平原1:50 000水文地质调查项目完成杨林尾图幅与陆溪口图幅,选择杨林尾图幅和陆溪口图幅中的4个代表性钻孔,分别做了3组抽水试验和一组压水试验.对抽水数据使用Dupuit公式法结合抽水稳定阶段数据求解含水层参数,同时利用Aquifer Test软件中Theis标准曲线法、直线图解法对抽水试验中非稳定条件下抽水数据对含水层参数求解,得到孔隙水含水层渗透系数及弹性给水度;利用压水试验工程规范求解基岩裂隙含水层的渗透系数.探讨了利用非稳定抽水试验条件下求解含水层参数方法的可行性及该方法的优势.计算结果表明:杨林尾镇浅层(20.2~64.55 m)含水层渗透系数为0.075 m/d,弹性给水度为5.8×10-2;深层(138~160 m)含水层渗透系数为9.89 m/d,弹性给水度为2.3×10-5;陆溪口镇浅层(19.4~36.4 m)含水层渗透系数1.26 m/d,弹性给水度为1.1×10-1;基岩渗透系数为0.012 m/d.通过结果对比分析发现对于单孔非稳定抽水试验,对前期水位降深数据筛选分析,同样可以利用非稳定井流理论反演含水层参数,结果比较可靠.   相似文献   

7.
The use of resistivity sounding and two-dimensional (2-D) resistivity imaging was investigated with the aim of delineating and estimating the groundwater potential in Keffi area. Rock types identified are mainly gneisses and granites. Twenty-five resistivity soundings employing the Schlumberger electrode array were conducted across the area. Resistivity sounding data obtained were interpreted using partial curve matching approach and 1-D inversion algorithm, RESIST version 1.0. The 2-D resistivity imaging was also carried out along two traverses using dipole–dipole array, and the data obtained were subjected to finite element method modeling using DIPRO inversion algorithm to produce a two-dimensional subsurface geological model. Interpretation of results showed three to four geoelectrical layers. Layer thickness values were generally less than 2 m for collapsed zone, and ranged from 5 to 30 m for weathered bedrock (saprolite). Two major aquifer units, namely weathered bedrock (saprolite) aquifer and fractured bedrock (saprock) aquifer, have been delineated with the latter usually occurring beneath the former in most areas. Aquifer potentials in the area were estimated using simple schemes that involved the use of three geoelectrical parameters, namely: depth to fresh bedrock, weathered bedrock (saprolite) resistivity and fractured bedrock (saprock) resistivity. The assessment delineated the area into prospective high, medium and low groundwater potential zones.  相似文献   

8.
李霞  文章  梁杏  马腾  陈晨 《地球科学》2017,42(5):743-750
含水层的水文地质参数是进行地下水资源计算、地下水污染防控等所必需的基础数据,结合数值模拟技术进行含水层参数反演很有必要.按照1:5万水文地质调查规范在江汉平原仙桃市杨林尾镇复兴水厂不同含水层位开展抽水试验,包括深层含水层单孔抽水试验以及浅层含水层中群孔(2孔)抽水试验.对于单孔抽水试验,应用第1类越流系统井流理论进行参数反演;对于群孔抽水试验,推导了特定综合井函数,并利用特定标准曲线匹配法和直线图解法求解了含水层参数.随后利用FEFLOW软件建立了相应数值模型,拟合了含水层参数.结果表明:浅层含水层的渗透系数变化范围为21.66~54.00 m/d,贮水率变化范围为1.28×10-5~8.00×10-4 m-1;深层含水层渗透系数变化范围为1.27~7.00 m/d,贮水率变化范围为3.90×10-6~5.00×10-6 m-1.对于深层承压含水层而言,越流补给量较大.采用数值模拟方法结合抽水试验数据求参,综合考虑了含水层结构,拟合效果好,所得结果更加可靠.   相似文献   

9.
An electrical resistivity survey of a portion of the Cooper Reservoir Basin in northeast Texas has been used to delineate the major lithostratigraphic units of Quaternary flood plain deposits and subsurface paleogeomorphic features of interest to geoarchaeologists. This investigation was conducted to evaluate the fluviatile deposits along the South Sulphur River which flows through Cooper Basin, to identify the basin morphology, and to detect buried geomorphic features. Buried stream channels were considered to be important targets since buried prehistoric site locations are thought to be related to patterns of fluvial facies. Two general techniques were used in the survey. First, soundings were conducted over borehole locations to correlate lithologies with resistivity variations. Second, multiple resistivity profiles were established along traverses across the flood plain. By repeating each traverse but with increased probe separations, a composite of profiles was developed yielding electrical cross-sections of the subsurface. These cross-sections were then interpreted in terms of the lithologic stratigraphy in the basin. Sounding data were evaluated using empirical methods, and profile data were evaluated qualitatively. the sounding data defined the major resistivity horizons which correlate to the primary sedimentary units in the Cooper Basin. Profile data, used to construct resistivity cross-sections, revealed a series of buried erosional features interpreted as channel segments and allowed for the estimation of relative time boundaries within sediments buried under the flood plain as the basin evolved.  相似文献   

10.
This study aims at finding out possible relation between lithology and spatial pattern of dissolved arsenic (As) in groundwater around Chakdaha municipality, West Bengal, India. Satellite image, coupled with electrical resistivity survey and borehole drilling helps to delineate surface and sub-surface lithological framework of the As affected alluvial aquifers. The satellite imagery demonstrate that the high As area are presumably under active flood plain environment (low-lying areas), that constantly receive organics due to periodic flooding. Thick low resistive (fine-grained) layer was observed at the top around the high As areas, which, however, not found in low As areas. The result suggests that hydraulic properties of the surface/sub-surface soil/sediment have an important control on the fate and transport of As in the aquifer. This study demonstrates that electrical resistivity tools can be effectively used for the reconnaissance survey in characterizing the plausible lithological framework of an alluvial aquifer containing As.  相似文献   

11.
Three approaches for estimating the hydraulic conductivity (K) of the Trifa aquifer, Morocco were investigated: (1) kriging of the K values obtained from pumping tests, (2) cokriging of the pumping test data with electrical resistivity data as a secondary variable, and (3) cokriging of the pumping test data with the slope of the water table. Gauss-transformed values of the variables are used because they provide more robust variograms and transformed values of the primary and secondary variables show correlations higher than the raw values, which is beneficial in cokriging. In cokriging with electrical resistivity, two zones are considered since the geological deposits are different from the north to the south of the aquifer, which is reflected in different correlations between the variables. Comparison of the three approaches is based mainly on the estimation errors, and to a lesser degree on the cross-validations of the corresponding variogram models and general considerations, like the measurements’ reliability and aquifer make-up. The best-estimated K is given by cokriging with the slope of the water table and is therefore preferred for further use in groundwater flow modeling. Thus, electrical resistivity or the slope of the water table can both be used as secondary variables to estimate K, especially in heterogeneous aquifers with lateral variations in lithology, as is the case of the Trifa aquifer.  相似文献   

12.
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13.
The interpreted Earth subsurface resistivity layer parameters of 55 vertical geoelectrical soundings are analyzed over a fan shaped area of 1,700 km2 from Pipli-Astrang-Bhramgiri, Orissa, India. In this study, Dar-Zarrouk (D-Z) parameters, namely the longitudinal conductance (S), transverse resistance (T) and longitudinal resistivity (R s ) are analyzed and we encountered the resistivity regime of the clay layers, saline and fresh water bearing formations. The significance of these parameters in establishing an easily decipherable vision about the occurrence and distribution of fresh and saline water aquifers, while dealing with complicated situations of intermixing of the resistivity ranges of saline and fresh water aquifers has been illustrated. The results show that the Dar-Zarrouk (D-Z) parameters provide a useful and confident solution in delineating the saline and fresh water aquifers. The behavior of the D-Z parameters S, T and R s , and its patterns in space over large areas with respect to the occurrence of saline water and fresh water aquifer systems in the deltaic coastal aquifer system has been demonstrated.  相似文献   

14.
A monitoring system, including five groups of piezometers and five vertical multielectrode profiling probes (VMEP), has been installed in an aquifer beneath a coastal dune in Denmark. In order to assess the salinity distribution within the aquifer, geoelectrical data were gathered in March, June and September 2008, by measuring a dipole-dipole and gradient array using multielectrode profiling. Interpretation of the processed resistivity data was performed by regularized inversion using a one-dimensional, horizontally layered model of formation resistivity. The standard deviation on estimated layer log-resistivity was 0.01–0.03. By estimating two parameters of a power function, observed fluid conductivities derived from samples of porewater were related to corresponding estimated formation resistivities. The conductivity profiles correlate with a winter situation in March with high sea level, active recharge and significant wave activity, causing increased hydraulic heads, a thicker freshwater lens and salt water overlying freshwater close to the sea. In June, the thickness of the freshwater lens is reduced due to less recharge and prevailing offshore winds, imposing density-stable conditions and a sharper transition between fresh and brackish water. During the autumn, aquifer recharge is enhanced and hydraulic heads increase, resulting in a thicker freshwater lens.  相似文献   

15.
The integration of surface geological and geomorphological information with borehole point-data and geophysical (e.g., geoelectrical) images of the subsurface yields spatially consistent representations of alluvial aquifers heterogeneity at different scales, from depositional systems to basin fills. Such an approach requires a conceptual framework to match the stratigraphic units with their evidence from ground-based DC resistivity methods to effectively fill the gaps between sparse borehole data and to obtain valid representations of sedimentary heterogeneities. Such an approach is applied to characterize two sites of the Quaternary aquifers of the central Po Plain (Italy), which represent (1) the middle-upper Pleistocene braided to meandering river depositional systems sitting on Southalpine crust and (2) their down-current counterparts, where they are involved by the latest uplift and deformation due to the tectonic activity of the Apennine frontal thrusts. Electrical resistivity was considered as a proxy of the litho-textural properties of hydrofacies and their major hierarchical association at depth and was interpreted in accordance with the depth-decreasing resolution of ground-based resistivity methods. Thus, it was possible to identify the geophysical signature of hydrostratigraphic units through “Electrostratigraphic Units”, i.e., sedimentary volumes identified by resistivity contrasts that spatially preserve the vertical polarity. Hydrostratigraphy and electrostratigraphy were then joined together through a site-specific relationship between electrical resistivity and hydraulic conductivity, which takes into account the prevailing process of current conduction, the litho-textural properties of hydrofacies and the groundwater electrical conductivity. At the scales of aquifer systems and complexes, this approach permitted to establish the conceptual framework to match hydrostratigraphy, electrostratigraphy, average hydrodynamic properties and distribution of heterogeneities.  相似文献   

16.
This study has been conducted to find out the aquifer characteristics of Bagerhat Sadar and adjacent areas in Bangladesh using geoelectrical resistivity method and borehole logs. The interpretation of resistivity soundings (14 nos.) shows that the sub-surface lithological sequence can be divided into four geoelectric units. The deepest geoelectric unit (with resistivity from 8 Ohm-m to 18 Ohm-m) represents the deep aquifer with usually fresh water. Resistivity values of 12 ?m or more for this unit may indicate formation water as acceptable for coastal people. In the study area, the shallow aquifer inferred is not suitable for groundwater development.  相似文献   

17.
The integration of geophysical data with direct hydrogeological measurements can provide a minimally invasive approach to characterize the subsurface at a variety of resolutions and over many spatial scales. The field of hydrogeophysics has attracted much attention during the last two decades. In this domain, the geophysical data inverted to geophysical models are interpreted in terms of the hydrogeology to serve as a basis for the definition of hydraulic models in the areas of interest. The hydraulic conductivity (K) value measured in a reference borehole has been combined with the electrical conductivity obtained from nearby geo-electromagnetic sounding data in the Cenomanian (Upper Cretaceous) aquifer, central Sinai, Egypt. The resulting relation was interpreted with Dar Zarrouk parameters to infer the transmissivity variations at other vertical electrical sounding locations, where K values are unknown. Coincident transient electromagnetic data have been adopted to increase accuracy while interpreting the aquifer geoelectrical properties. The results indicate that the transmissivity values in the aquifer of interest vary from 2,446 to 9,694 m2/day, and K varies from 12.9 to 57.0 m/day throughout the studied area.  相似文献   

18.
The Mida plain, which is part of the North Gabès region (southern Tunisia), is characterized by the deep sandy units of the ‘Continental intercalaire’ (CI) or the limestone of the Lower Senonian. A geophysical survey, by electrical sounding (ES), was undertaken in the studied region to better characterize the deep geological structure of this plain and therefore its aquifer resources potential. The analysis of the results shows that the prospected zone is characterized by the succession of several levels with contrasted resistivities, which are often affected by faults. Among these observed geoelectrical levels, the highly conductor one could host a saline aquifer. Another geoelectrical level corresponding to the resistant bedrock detected at Oudhref horst can contain better-quality water than that of the aquifer detected in the El Mida Graben. In this work, we tried to explain the origin of the salinity of this aquifer. Thus, we hypothesise about a contamination from Jebel Zemlet El Beida through a border fault and another one from the Sebkhet El Hamma. To cite this article: A. Mhamdi et al., C. R. Geoscience 338 (2006).  相似文献   

19.
A heterogeneous anisotropic steady-state groundwater flow model for the multi-aquifer system of a part of southern Bengal Basin shows that human intervention has changed the natural groundwater flow system. At present, the shallow groundwater flow is restricted within the aquifer, with very short travel time of tens of years and vertical path length. The deep aquifer is fed by surface water or rainwater from distant locations with travel time of thousands of years and has no hydraulic connection with the arsenic-rich shallow aquifer. Numerical simulations indicate that the future pumping of deep groundwater is not likely to drive in arsenic from the shallow aquifer. Therefore, new wells may be installed in the deep aquifer. High pumping of shallow unpolluted aquifer consisting of brown sand will drive in groundwater containing organic matter from the post-Last Glacial Maximum aquifer-aquitard system. The organic matter drives reduction of manganese oxides at strip interfaces between palaeo-channel and palaeo-interfluve. After the completion of manganese reduction, FeOOH reduction may take place in the marginal palaeo-interfluvial aquifer and release sorbed arsenic. Arsenic then moves into the interior of palaeo-interfluvial aquifer polluting its fresh groundwater. Arsenic migration rates ranges between 0.21 and 6.3 and 1.3 × 10?2 and 0.4 m/year in horizontal and vertical directions, respectively. Therefore, palaeo-interfluvial aquifer will remain arsenic-free for hundreds to thousands of years to supply safe drinking water.  相似文献   

20.
Estimation of hydraulic conductivity from surface resistivity measurements is one of the most difficult and challenging hydrogeophysical targets. The promising side of this relation is the analogy between electric current flow and water flow, whereas the grand ambiguity is the non-dimensionality between both two quantities. Imaginary surface conductivity component is used recently to deduce the hydraulic conductivity via complex resistivity measurements. Since there are similar properties between imaginary (out-of-phase) and real (in-phase) surface conductivity components, the latter is used in this paper to predict the hydraulic conductivity. Two mathematical parameters were determined to express the electrical equivalent of hydraulic conductivity in sand and clay systems based on the mode of electrical double-layer formation in both systems. The reliability of the proposed method is tested through applying on two datasets representing sand and clay systems. The first dataset is a clean sand and gravel aquifer in the Keritis basin in Chania, Crete, Greece. The second is mostly clayey sand aquifer in Wadi El-Assuity, Egypt. Application of the present approach in these two cases resulted in promising nearly identical values with the measured hydraulic conductivity via pumping test or geometric hydraulic conductivity via grain size analysis.  相似文献   

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