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1.
Facies reconstructions are used in hydrogeology to improve the interpretation of aquifer permeability distribution. In the absence of sufficient data to define the heterogeneity due to geological processes, uncertainties in the distribution of aquifer hydrofacies and characteristics may appear. Geometric and geostatistical methods are used to understand and model aquifer hydrofacies distribution, providing models to improve comprehension and development of aquifers. However, these models require some input statistical parameters that can be difficult to infer from the study site. A three-dimensional reconstruction of a kilometer scale fine-grain dominated Cenozoic alluvial fan derived from more than 200 continuously cored, closely spaced, and regularly distributed wells is presented. The facies distributions were reconstructed using a genetic stratigraphic subdivision and a deterministic geostatistical algorithm. The reconstruction is only slightly affected by variations in the geostatistical input parameters because of the high-density data set. Analysis of the reconstruction allowed identification in the proximal to medial alluvial fan zones of several laterally extensive sand bodies with relatively higher permeability; these sand bodies were quantified in terms of volume, mean thickness, maximum area, and maximum equivalent diameter. These quantifications provide trends and geological scenarios for input statistical parameters to model aquifer systems in similar alluvial fan depositional settings. 相似文献
2.
Application of multiple-point geostatistics on modelling groundwater flow and transport in a cross-bedded aquifer (Belgium) 总被引：3，自引：1，他引：2
Sedimentological processes often result in complex three-dimensional subsurface heterogeneity of hydrogeological parameter values. Variogram-based stochastic approaches are often not able to describe heterogeneity in such complex geological environments. This work shows how multiple-point geostatistics can be applied in a realistic hydrogeological application to determine the impact of complex geological heterogeneity on groundwater flow and transport. The approach is applied to a real aquifer in Belgium that exhibits a complex sedimentary heterogeneity and anisotropy. A training image is constructed based on geological and hydrogeological field data. Multiple-point statistics are borrowed from this training image to simulate hydrofacies occurrence, while intrafacies permeability variability is simulated using conventional variogram-based geostatistical methods. The simulated hydraulic conductivity realizations are used as input to a groundwater flow and transport model to investigate the effect of small-scale sedimentary heterogeneity on contaminant plume migration. Results show that small-scale sedimentary heterogeneity has a significant effect on contaminant transport in the studied aquifer. The uncertainty on the spatial facies distribution and intrafacies hydraulic conductivity distribution results in a significant uncertainty on the calculated concentration distribution. Comparison with standard variogram-based techniques shows that multiple-point geostatistics allow better reproduction of irregularly shaped low-permeability clay drapes that influence solute transport. 相似文献
3.
The complexity of alluvial-pluvial fan depositional systems makes the detailed characterization of their heterogeneity difficult, yet such a detailed characterization is commonly needed for construction of reliable groundwater models. Traditional models mainly focus on using a single aquifer property to qualitatively or semi-quantitatively characterize the heterogeneity of aquifer, so that they are unable to quantitatively reflect the synthetic heterogeneity of all aquifer properties. In this paper, we propose the heterogeneity synthetic index (HSI) for quantitative characterization of synthetic heterogeneity of an aquifer. The proposed calculation process involves four steps: (1) estimation of the hydraulic conductivity of a sediment sample using the cloud-Markov model, (2) establishment of the sedimentary microfacies distribution model through the Markov chain, (3) characterization of the distribution model of hydrogeological parameters using the improved sequential simulation method according to the “facies-controlled modeling” technique, and (4) application of the entropy weight method to calculate the weight coefficient of the above aquifer properties. The HSI of an aquifer is calculated by superposition of these models according to the corresponding weight coefficient. This approach was applied to the Luancheng aquifer deposit in the southeast Hutuo River alluvial-pluvial fan in the North China Plain (NCP). The results have demonstrated that aquifer 3 which was formed in the middle Pleistocene has the strongest heterogeneity, with an HSI of 0.25–0.75. Aquifer 4 formed in the early Pleistocene shows an intermediate heterogeneity, with the HSI ranging 0.35–0.75. The weakest heterogeneity was found in aquifers 1 and 2 formed in the Holocene and late Pleistocene, with HSI values of 0.40–0.75 and 0.40–0.80, respectively. The heterogeneity of all the four aquifers is relatively strong in the radial direction of the Huai River alluvial-pluvial fan due to the abrupt change of microfacies. In contrast, in the radial direction of the Hutuo River alluvial-pluvial fan, the microfacies change mildly, and the continuity of hydrogeological parameters is better, which has resulted in weaker heterogeneity of the four aquifers in this direction. Findings suggest that the sedimentary environment has significant effects on the aquifer heterogeneity. Considering that there are many aquifer properties, HSI can quantitatively characterize the synthetic heterogeneity of the aquifer and describe the influence of each aquifer property on the synthetic heterogeneity of the aquifer according to its weight coefficient. Thus the HSI approach can be successfully used to deal with the spatial heterogeneity of aquifer and provide a foundation for studies on contaminant transport. 相似文献
4.
Source, type, and quantity of various components of groundwater, as well as their spatial and temporal variations were determined
by different hydrochemical methods in the alluvial aquifer of the upper Rhone River valley, Bois de Finges, Wallis Canton,
Switzerland. The methods used are hydrochemical modeling, stable-isotope analysis, and chemical analysis of surface water
and groundwater. Sampling during high- and low-water periods determined the spatial distribution of the water chemistry, whereas
monthly sampling over three years provided a basis for understanding seasonal variability. The physico-chemical parameters
of the groundwater have spatial and seasonal variations. The groundwater chemical composition of the Rhone alluvial aquifer
indicates a mixing of weakly mineralized Rhone River water and SO4-rich water entering from the south side of the valley. Temporal changes in groundwater chemistry and in groundwater levels
reflect the seasonal variations of the different contributors to groundwater recharge. The Rhone River recharges the alluvial
aquifer only during the summer high-water period.
Electronic Publication 相似文献
5.
Ma Lei Liao Huasheng Qian Jiazhong Zhao Weidong Li Shuguang 《Hydrogeology Journal》2023,31(4):985-1004
The heterogeneity of hydrofacies is represented as spatial variability on different scales, and it has a significant impact on the behavior of groundwater flow and pollutant transport. However, effectively characterizing hydrofacies heterogeneity on different scales remains one of the most challenging problems in hydrogeology. In this study, an upscaling hydrofacies simulation (UHS) framework is proposed by integrating the upscaling borehole generalization (UBG) approach and transition probability geostatistics (TPG). A new UBG approach for generating virtual boreholes with equivalent hydrofacies information based on relatively high-density borehole lithological data is proposed, and the TPG is used to delineate the multiscale facies distribution. The results show that the UBG approach can significantly reduce borehole data volume while retaining the key equivalent hydrofacies information on a coarser scale. The UHS method can well characterize the overall distribution of equivalent hydrofacies on coarser scales, with the minor-component hydrofacies underestimated and the major-component hydrofacies overestimated to a lesser extent, and more equivalent facies appearing in strong heterogeneous areas. These results demonstrate that the UHS method can provide valuable capacity insights and advantages in characterizing hydrofacies heterogeneity on different scales using such high-density borehole lithological data.
相似文献6.
Daniel Paradis Laurie Tremblay René Lefebvre Erwan Gloaguen Alfonso Rivera Michel Parent Jean-Marc Ballard Yves Michaud Patrick Brunet 《Environmental Earth Sciences》2014,72(5):1325-1348
Providing a sound basis for aquifer management or remediation requires that hydrogeological investigations carried out to understand groundwater flow and contaminant transport be based on representative data that capture the heterogeneous spatial distribution of aquifer hydraulic properties. This paper describes a general workflow allowing the characterization of the heterogeneity of the hydraulic properties of granular aquifers at an intermediate scale of a few km2. The workflow involves characterization and data integration steps that were applied on a 12-km2 study area encompassing a decommissioned landfill emitting a leachate plume and its main surface water receptors. The sediments composing the aquifer were deposited in a littoral–sublittoral environment and show evidence of small-scale transitional heterogeneities. Cone penetrometer tests (CPT) combined with soil moisture and electrical resistivity (SMR) measurements were thus used to identify and characterize spatial heterogeneities in hydraulic properties over the study area. Site-specific statistical relationships were needed to infer hydrofacies units and to estimate hydraulic properties from high-resolution CPT/SMR soundings distributed all over the study area. A learning machine approach was used due to the complex statistical relationships between colocated hydraulic and CPT/SMR data covering the full range of aquifer materials. Application of this workflow allowed the identification of hydrofacies units and the estimation of horizontal hydraulic conductivity, vertical hydraulic conductivity and porosity over the study area. The paper describes and discusses data acquisition and integration methodologies that can be adapted to different field situations, while making the aquifer characterization process more time-efficient and less labor-intensive. 相似文献
7.
Zhenxue Dai Elizabeth Keating Carl Gable Daniel Levitt Jeff Heikoop Ardyth Simmons 《Hydrogeology Journal》2010,18(3):607-624
Based on the regional hydrogeology and the stratigraphy beneath the Los Alamos National Laboratory (LANL) site, New Mexico (USA), a site-scale groundwater model has been built with more than 20 stratified hydrofacies. A stepwise inverse method was developed to estimate permeabilities for these hydrofacies by coupling observation data from different sources and at various spatial scales including single-well test, multiple-well pumping test and regional aquifer monitoring data. Statistical analyses of outcrop permeability measurements and single-well test results were used to define the prior distributions of the parameters. These distributions were used to define the parameter initial values and the lower and upper bounds for inverse modeling. A number of inverse modeling steps were performed including the use of drawdown data from the pump tests at two wells (PM-2 and PM-4) separately, and a joint inversion coupling PM-2 and PM-4 pump test data and head data from regional aquifer monitoring. Parameter sensitivity coefficients for different data sets were computed to analyze if the model parameters can be estimated accurately with the data provided at different steps. The joint inversion offers a reasonable fit to all data sets. The uncertainty of estimated parameters for the hydrofacies is addressed with the parameter confidence intervals. 相似文献
8.
Ground penetrating radar (GPR) has proved to be an extremely useful geophysical tool, in conjunction with direct geological data, to develop a realistic, macroscopic, subjective-based conceptual model of aquifer architecture within a shallow coastal alluvial plain. Subsequent finite-difference groundwater modelling has not only enabled determination of the dominant groundwater flow paths for the plain, but has also quantified the effects of within-facies and between-facies sedimentary heterogeneity on those flow paths. The interconnection of narrow, unconfined alluvial channels and a broad, semi-confined alluvial delta is ensuring that most fresh groundwater that enters the plain in the form of precipitation or recharge from lateral bedrock hills, is discharged into the eastern coastal wetlands via that alluvial delta aquifer. 相似文献
9.
10.
An efficient method to upscale hydraulic conductivity (K) from detailed three-dimensional geostatistical models of hydrofacies heterogeneity to a coarser model grid is presented. Geologic heterogeneity of an alluvial fan system was characterized using transition-probability-based geostatistical simulations of hydrofacies distributions. For comparison of different hydrofacies architecture, two alternative models with different hydrofacies structures and geometries and a multi-Gaussian model, all with the same mean and variance in K, were created. Upscaling was performed on five realizations of each of the geostatistical models using the arithmetic and harmonic means of the K-values within vertical grid columns. The effects of upscaling on model domain equivalent K were investigated by means of steady-state flow simulations. A logarithmic increase in model domain equivalent K with increasing upscaling, was found for all fields. The shape of that upscaling function depended on the structure and geometry of the hydrofacies bodies. For different realizations of one geostatistical model, however, the upscaling function was the same. From the upscaling function a factor could be calculated to correct the upscaled K-fields for the local effects of upscaling. 相似文献
11.
为探讨含水层非均质性不同刻画方法对地下水流和溶质运移预测的影响,基于非均质含水层砂箱实验,分别用传统等效均质模型、克立金插值和水力层析刻画含水层渗透系数场,并探讨了先验信息对水力层析结果的影响.将不同方法估算的渗透系数场用以预测地下水流和溶质运移过程,以此判断不同方法估算结果的优劣,分析含水层非均质性对地下水流和溶质运移的影响.结果表明:与克立金插值法相比,水力层析法可以更好地刻画含水层非均质性,较准确地预测地下水流和溶质运移过程;钻孔岩心渗透系数样本值作为先验信息可以提高水力层析法估算结果的精度;传统等效均质模型无法准确预测地下水流和溶质运移过程.含水层非均质性的增强将导致溶质污染羽分布形态和运移路径的空间变异性增强,并且优势通道直接决定溶质的分布及运移路径. 相似文献
12.
为了研究地面沉降的时空分布模式、机理机制,选择北京典型沉降区——潮白河冲洪积扇为研究区,采用PS-InSAR技术、莫兰指数及地理探测器,分析了研究区地面沉降的空间异质性特征,探测了不同特征下的地面沉降的主要驱动因素。结果表明：2017-01—2019-01研究区内地面沉降时空分布特征以一般沉降为主,沉降速率为[-133,3] mm/a,最大累积沉降量为261 mm,呈北部轻微、中部较严重、南部较轻的分布状态,其中,严重、极严重等级地面沉降主要分布在中游顺义后沙峪东部等地区及中下游交界地带的潞城镇;不同地区地面沉降呈现不同的空间异质性特征,即不均匀地面沉降分布特征明显,中游、下游均表现为低—低集聚;不同分布特征下地面沉降主要驱动因素不同,中游地区主要驱动因素为第二承压水水位变化和可压缩层厚度,下游主要驱动因素为浅层地下水水位变化和第一承压水水位变化。莫兰指数能够有效分析地面沉降空间异质性,识别集聚特征;地理探测器可以探明沉降空间异质性成因,获得其主要驱动因素。 相似文献
13.
The complex siliciclastic aquifer system underneath the Baton Rouge area, Louisiana (USA), is fluvial in origin and is characterized by strongly binary heterogeneity of sand units and mudstones as pervious and impervious hydrofacies. The east–west trending Baton Rouge fault and Denham Springs-Scotlandville fault cut across East Baton Rouge Parish and play an important role in groundwater flow and aquifer salinization. This study reconstructs the Baton Rouge aquifer-fault system architecture for a Miocene-Pliocene depth interval that consists of the 1,200-foot sand to the 2,000-foot sand. The results show the spatial extent of sand units, their interconnections, and flow paths within each sand unit. The regional-scale formation dip, the sand unit offset on the faults, and the volumetric spatial extent of individual sand units are quantified. The study reveals the complexity of the Baton Rouge aquifer-fault system where the sand deposition is non-uniform, different sand units are interconnected, the sand unit displacement on the faults is significant, and the spatial distribution of flow pathways through the faults is sporadic. The identified locations of flow pathways through the Baton Rouge fault provide useful information on possible windows for saltwater intrusion from the south. 相似文献
14.
A. Lawrence D. Gooddy P. Kanatharana W. Meesilp V. Ramnarong 《Hydrogeology Journal》2000,8(5):564-575
Many cities and towns in South and Southeast Asia are unsewered, and urban wastewaters are often discharged either directly
to the ground or to surface-water canals and channels. This practice can result in widespread contamination of the shallow
groundwater. In Hat Yai, southern Thailand, seepage of urban wastewaters has produced substantial deterioration in the quality
of the shallow groundwater directly beneath the city. For this reason, the majority of the potable water supply is obtained
from groundwater in deeper semi-confined aquifers 30–50 m below the surface. However, downward leakage of shallow groundwater
from beneath the city is a significant component of recharge to the deeper aquifer, which has long-term implications for water
quality. Results from cored boreholes and shallow nested piezometers are presented. The combination of high organic content
of the urban recharge and the shallow depth to the water table has produced strongly reducing conditions in the upper layer
and the mobilisation of arsenic. A simple analytical model shows that time scales for downward leakage, from the surface through
the upper aquitard to the semi-confined aquifer, are of the order of several decades.
Electronic Publication 相似文献
15.
J. B. Callegary C. P. Kikuchi J. C. Koch M. R. Lilly S. A. Leake 《Hydrogeology Journal》2013,21(1):25-39
Groundwater in the US state of Alaska is critical to both humans and ecosystems. Interactions among physiography, ecology, geology, and current and past climate have largely determined the location and properties of aquifers as well as the timing and magnitude of fluxes to, from, and within the groundwater system. The climate ranges from maritime in the southern portion of the state to continental in the Interior, and arctic on the North Slope. During the Quaternary period, topography and rock type have combined with glacial and periglacial processes to develop the unconsolidated alluvial aquifers of Alaska and have resulted in highly heterogeneous hydrofacies. In addition, the long persistence of frozen ground, whether seasonal or permanent, greatly affects the distribution of aquifer recharge and discharge. Because of high runoff, a high proportion of groundwater use, and highly variable permeability controlled in part by permafrost and seasonally frozen ground, understanding groundwater/surface-water interactions and the effects of climate change is critical for understanding groundwater availability and the movement of natural and anthropogenic contaminants. 相似文献
16.
This study evaluates the alternative conceptual models for groundwater modelling. A true model was created with a synthetic alluvial fan-plain hydrogeological framework. Various alternative conceptual models were evaluated for groundwater flow simulations. The first alternative model is a single aquifer layer model; the second alternative model is a 3-layer aquifer model; and the third model is a 5-layer model consisting of 3 aquifers separated by 2 aquitards. All models could fit very well to the observations with optimized values of hydraulic conductivities. However, the single aquifer layer model can only compute water balance components with good accuracy. The 3-layer aquifer model can be used for water balance computation and groundwater head simulation with small errors. The 5-layer model is capable of simulating water budget, groundwater head distribution and travel times with high accuracy. Multi-model analysis found only the 3rd alternative model superior. 相似文献
17.
Zhou Xun Chen Mingyou Wan Li Department of Water Resources Environmental Engineering China University of Geosciences Beijing China Wang Juping Ning Xuesheng Beihai Institute of Hydrogeology Engineering Geology Mineral Resour 《中国地质大学学报(英文版)》2000,11(3)
INTRODUCTIONThe city of Beihai,located on the south coast ofGuangxi,China,relies heavily on groundwater for its potablewater supply and agricultural irrigation.With rapid increasein population (for instance,from 134 0 0 0 in 1987to 47930 0in1995 ) and in developm ent program s,the demand for freshwater has been growing. Approxim ately 170 0 0 0 m3/ d ofgroundwater has been pumped from the productive coastalaquifers in recent years.Contamination of the fresh water inthe coastal aquifers b… 相似文献
18.
This paper describes the implementation of process-based models reflecting relative groundwater nitrate vulnerability of the
shallow alluvial Lower Savinja Valley (LSV) aquifer in Slovenia. A spatially explicit identification of the potentially vulnerable
priority areas within groundwater bodies at risk from a chemical point of view is being required for cost-effective measures
and monitoring planning. The shallow LSV unconfined aquifer system consists of high-permeable Holocene and middle- to low-permeable
Pleistocene gravel and sand, with a maximum thickness of about 30 m, mainly covered by shallow eutric fluvisoils or variously
deep eutric cambisoil. The hydrogeological parameters, e.g. the depth to the groundwater, hydrological role of the topographic
slope, etc. usually used in different point count schemes are, in the case of the lowland aquifer and shallow groundwater,
spatially very uniform with low variability. Furthermore, the parametric point count methods are generally not able to illustrate
and analyze important physical processes, and validation of the results is difficult and expensive. Instead of a parametric
point count scheme, we experimentally used the Arc-WofE extension for weights-of-evidence (WofE) modelling. All measurement
locations with a concentration higher than the value of 20 mg NO3
− per litre of groundwater have been considered as training points (173), and the three process-based models generalized output
layers of groundwater recharge (GROWA), nitrate leached from the soil profile (SWAT) and groundwater flow velocity (FEFLOW),
served as evidential themes. The technique is based on the Bayesian idea of phenomena occurrences probability before (prior
probability) and after consideration of any evidential themes (posterior probability), which were measured by positive and
negative weights as an indication of the association between a phenomena and a prediction pattern. The response theme values
describe the relative probability that a 100 × 100 m spatial unit will have a groundwater nitrate concentration higher than
the training points’ limit values with regard to prior probability value. The lowest probability of groundwater nitrate occurrence
is in the parts of the LSV aquifer, which are known as anoxic condition areas with very likely denitrification processes.
The cross-validation of the dissolved oxygen and dissolved nitrate response theme confirmed the accuracy of the groundwater
nitrate prediction. The WofE model results very clearly indicate regional groundwater nitrate distribution and enable spatial
prediction of the probability for increased groundwater nitrate concentration in order to plan the groundwater nitrate reduction
measures and optimize the programme for monitoring the effects of these measures. 相似文献
19.
分析了目前孔隙地下水流三维有限差分数值模拟中对含水层系统三维空间离散存在的问题，针对自然界孔隙含水层与隔水层空间分布的不连续性与厚度的不均匀性，研究了基于GIS的孔隙含水层系统三维空间离散实现的技术路线，提出了基于GIS与不规则六面体元的孔隙含水层系统的三维空间离散方法，最大限度地保证了离散体元中含水层类型的单一性，提高了孔隙地下水流模拟模型三维空间离散的精度。 相似文献