GIS-based subsurface databases and 3-D geological modeling as a tool for the set up of hydrogeological framework: Nabeul–Hammamet coastal aquifer case study (Northeast Tunisia)

The subsurface data are a basic requirement for the set up of hydrogeological framework. Geographic information systems (GIS) tools have proved their usefulness in hydrogeology over the years which allow for management, synthesis, and analysis of a great variety of subsurface data. However, standard multi-layered systems are quite limited for modeling, visualizing, and editing subsurface data and geologic objects and their attributes. This paper presents a methodology to support the implementation of hydrogeological framework of the multi-layered aquifer system in Nabeul–Hammamet (NH) coastal region (NE, Tunisia). The methodology consists of (1) the development of a complete and generally accepted hydrogeological classification system for NH aquifer system (2) the development of relational databases and subsequent GIS-based on geological, geophysical and hydrogeological data, and (3) the development of meaningful three-dimensional geological and aquifer models, using GIS subsurface software, RockWorks 2002. The generated 3-D geological models define the lithostratigraphy and the geometry of each depositional formation of the region and delineate major aquifers and aquitards. Where results of the lithologic model revealed that there is a wide range of hydraulic conductivities in the modeled area, which vary spatially and control the groundwater flow regime. As well, 17 texturally distinct stratigraphic units were identified and visualized in the stratigraphic model, while the developed aquifer model indicates that the NH aquifer system is composed of multi-reservoir aquifers subdivided in aquifers units and separated by sandy clay aquitards. Finally, this study provides information on the storing, management and modeling of subsurface spatial database. GIS has become a useful tool for hydrogeological conceptualization and groundwater management purposes and will provide necessary input databases within different groundwater numerical models.     

Interaction of various flow systems in small alpine catchments: conceptual model of the upper Gurk Valley aquifer,Carinthia, Austria

Small alpine valleys usually show a heterogeneous hydraulic situation. Recurring landslides create temporal barriers for the surface runoff. As a result of these postglacial processes, temporal lakes form, and thus lacustrine fine-grained sedimentation intercalates with alluvial coarse-grained layers. A sequence of alluvial sediments (confined and thus well protected aquifers) and lacustrine sediments (aquitards) is characteristic for such an environment. The hydrogeological situation of fractured hard-rock aquifers in the framing mountain ranges is characterized by superficially high hydraulic conductivities as the result of tectonic processes, deglaciation and postglacial weathering. Fracture permeability and high hydraulic gradients in small-scaled alpine catchments result in the interaction of various flow systems in various kinds of aquifers. Spatial restrictions and conflicts between the current land use and the requirements of drinking-water protection represent a special challenge for water resource management in usually densely populated small alpine valleys. The presented case study describes hydrogeological investigations within the small alpine valley of the upper Gurktal (Upper Carinthia, Austria) and the adjacent Höllenberg Massif (1,772 m above sea level). Hydrogeological mapping, drilling, and hydrochemical and stable isotope analyses of springs and groundwater were conducted to identify a sustainable drinking-water supply for approximately 1,500 inhabitants. The results contribute to a conceptual hydrogeological model with three interacting flow systems. The local and the intermediate flow systems are assigned to the catchment of the Höllenberg Massif, whereas the regional flow system refers to the bordering Gurktal Alps to the north and provides an appropriate drinking water reservoir.     

苏锡常地区含水层结构和地下水位的虚拟表达

由于三维地质结构模型和地下水面(包括潜水水面和承压水水面)模型开展地面沉降机理研究的重要基础,因此,本次利用Visual C 和OpenGL(Open Graphics Library)将苏州—无锡—常州(简称苏锡常)地区第四系含水层结构和地下水位形态进行三维虚拟表达,创建了酷似于实际情况的地下水赋存环境(三维地质结构模型),并在该环境中添加了各含水层的水位线。研究者可交互操作于该虚拟环境,并能够直观形象地了解研究区内的水文地质情况(各地层间的空间分布及岩性特征、含水层间的补给关系及地下水位的动态过程等),从而获得身临其境的感受,为进行地面沉降机理研究提供一个基础性的辅助方法。     

Evaluation of alternative conceptual models for groundwater modelling

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.     

Assessment of paleo-recharge under the Fennoscandian Ice Sheet and its impact on regional groundwater flow in the northern Baltic Artesian Basin using a numerical model

The study investigates the mechanism of glacial meltwater recharge under the Fennosciandian Ice Sheet during the last glacial maximum (LGM) and its impact on regional groundwater flow in the northern Baltic Artesian Basin (BAB) in Estonia and Latvia. The current hypothesis is that a flow reversal occurred in the BAB due to subglacial recharge during the LGM. This hypothesis is supported by an extensive dataset of geochemical and isotopic measurements in the groundwater of northern Estonia, exhibiting significant depletion in δ¹⁸O with respect to modern precipitation. To verify the consistency of this hypothesis and better understand groundwater flow dynamics during the LGM period, a numerical model is developed for this area. Two cross-sectional models have been created across the northern BAB, in which groundwater flow and the transport of δ¹⁸O have been simulated from the beginning of the LGM to present-day. Several simulations were performed with different subglacial boundary conditions, to investigate the uncertainty related to subglacial recharge of meltwater during the LGM and the subsequent flow reversal in the northern BAB. Several simulations provide a satisfying fit between computed and observed values of δ¹⁸O, which means that the hypothesis of subglacial recharge of meltwater is consistent with δ¹⁸O distribution. The numerical model suggests that preservation of meltwater in northern Estonia is controlled by confining layers and the proximity to the outcrop area of aquifers, located in the Gulf of Finland. The results also suggest that glacial meltwater has been preserved under the Baltic Sea in the Gulf of Riga.     

An integrative geological and geophysical approach to characterize a superficial deltaic aquifer in the Camargue plain,France

Deltaic aquifers are complex due to the important heterogeneity of their structure and their hydrogeological functioning. Auger drilling provides localized, but very robust geological and hydrogeological information, while geophysical surveys can provide integrated subsurface information. An effective, easy-to-use and low-cost methodology combining geological/hydrogeological information from Auger drillings and the results from three geophysical techniques (Electromagnetic mapping, Electrical Sounding and Electrical Resistivity Tomography) is being developed to characterize the structure of a typical Mediterranean deltaic aquifer. A first hypothesis about hydrodynamic properties of the aquifer is also obtained. The study area is located in the Rhone delta (Middle Camargue/southern France). Integration of geophysical and geological techniques allowed identifying the presence and lateral extension of the Saint-Ferréol paleochannel, the vertical contact between lagoonal–fluvial deposits and the marine clayed silt that separate the superficial aquifer from the deeper aquifer. Likewise, high north–south heterogeneity and east–west homogeneity were highlighted in the study area. Presence of clay in sandy deposits in the low areas implies changes in lateral hydraulic permeability. This fact, jointed to the low hydraulic gradient, suggests a slow groundwater flow in the local system. The Rhone delta presents a typical configuration of a Mediterranean deltaic aquifer, thus this methodological approach can be used for similar deltaic Mediterranean systems.     

基于MODFLOW参数不确定性的地下水水流数值模拟方法

考虑到模型不确定性引起的地下水数值模拟不确定性对模拟过程的影响,在简要介绍含水层水文地质参数变异性研究进展和地质统计学的基础上,基于常用的确定性地下水流数值模拟软件MODFLOW开发了MODFLOW-Gslib软件,相较于传统的数值模拟方法,将地质统计学与数值模拟结合的方法能够模拟非均质含水层中的参数变异性问题。将MODFLOW-Gslib软件运用于模拟实例中,选择常见的不确定性因素进行模拟,并对其模拟产生的数据进行统计分析,结果表明,软件转化后的参数符合水文地质参数不确定性的相关特征;与原模拟结果进行对比,该软件能够更加真实地刻画含水层参数变异性特征。     

A simple model of leakage induced by deep pumping and its application to pollution beneath a city in Thailand

Many cities in developing countries are dependent upon groundwater for water supply. Frequently this groundwater is pumped from semi-confined aquifers in alluvial deposits. These deeper aquifers are often considered to be protected from polluted shallow water by intervening less-permeable layers. However, where groundwater is pumped from a semi-confined aquifer immediately beneath a city, significant induced leakage of contaminated shallow water can occur. This may lead to a serious deterioration of water quality in deeper aquifers in the longer-term. A simple model has been developed which provides insight into the hydraulic controls on water quality in such semi-confined aquifers. The model provides a tool for the initial assessment and prediction of the impact of urbanization on groundwater quality. Also, the model characterizes the key hydrogeological behaviour through a single parameter, here termed the ‘city leakage factor’, which can be used to assess the vulnerability to contamination by leakage. A case study of a city in Thailand illustrates the use of this model.

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Résumé Beaucoup de villes des pays en développement dépendent de l’eau souterraine pour leur alimentation en eau. Cette eau souterraine est souvent pompée dans des aquifères alluviaux semi-captifs. Ces aquifères plus profonds sont souvent considérés comme protégés des eaux peu profondes et polluées, grace à des couches intercalaires moins perméables. Cependant, dans le cas où l’eau souterraine est pompée à partir d’un aquifère semi-captif situé directement sous une ville, une drainance importante des eaux peu profondes et polluées peut être induite. Ceci peut entra?ner, à long terme, une détérioration significative de la qualité de l’eau dans les aquifères plus profonds. Un modèle simple a été construit fournissant un aper?u des contr?les hydrauliques agissant sur la qualité de l’eau dans des aquifères semi-captifs. Ce modèle est un outil permettant d’évaluer l’état initial et de prédire l’impact de l’urbanisation sur la qualité de l’eau souterraine. Le modèle caractérise également les comportements hydrogéologiques majeurs à travers un unique paramètre, nommé dans cette étude facteur de drainance de la ville“, et qui peut être utilisé pour évaluer la vulnérabilité de l’aquifère face à une contamination par drainance. L’étude de cas d’une ville en Tha?lande illustre l’utilisation de ce modèle.

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Resumen Muchas ciudades de paises en desarrollo dependen del agua subterránea para el abastecimiento de agua. Frecuentemente el agua subterránea se bombea de acuíferos semi-confinados en depósitos aluviales. Estos acuíferos más profundos se protegen frecuentemente de agua somera contaminada mediante la intervencción de capas menos permeables. Sin embargo, donde el agua subterránea se bombea de un acuífero semi-confinado inmediatamente debajo de una ciudad, pueden ocurrir fugas significativas inducidas de agua somera contaminada. Esto puede conducir a un serio deterioro de calidad de agua en acuíferos más profundos en el largo plazo. Se ha desarrollado un modelo simple el cual aporta idea acerca de los controles hidráulicos en la calidad del agua en tales acuíferos semi-confinados. El modelo aporta una herramienta para la evaluación inicial y predicción del impacto de urbanización en la calidad del agua subterránea. El modelo también caracteriza el comportamiento hidrogeológico clave a traves de un solo parámetro, que aquí se denomina ′factor de fuga de la ciudad′el cual puede usarse para evaluar la vulnerabilidad a la contaminación por fuga. El uso de este modelo se ilustra con un estudio de caso de una ciudad en Tailandia.

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Coastal aquifer assessment based on geological and geophysical survey,northwestern Crete,Greece

Groundwater preservation comprises a major problem in water policy. The comprehension of the groundwater/hydraulic systems can provide the means to approach this problem. Generally, drilling is expensive and time-consuming. On the other hand, new techniques have been applied during the last few decades that provide useful information on the depth and quality of aquifers. Among them, transient electromagnetic method (TEM) is an appealing method that provides fast results with minimum field crew and solves several hydrogeological problems. Many portable systems for single-site measurements are commercially available. The TEM-Fast 48HPC was used for acquiring 106 soundings in the northwestern Crete in Greece for defining the hydrogeological characteristics of the study area, since there were no available data from boreholes. Detailed geological, hydrolithological and tectonic survey was applied prior to the geophysical measurements. All the data were integrated to produce a secure and reliable hydrogeological model for the study area prior to any future hydrowell. Specifically, geometrical and hydraulic data of the study area groundwater were acquired. Two unconnected aquifers were detected and their possible contamination due to saltwater intrusion was analyzed and eliminated. Moreover, a location for borehole construction and groundwater pumping based on the potential of the aquifer system was proposed. Finally, the contribution of TEM (and electrical resistivity tomography) geophysical methods in studying complex coastal aquifers is shown by this work.     

Development of a 3D groundwater model based on scarce data: the Wadi Kafrein catchment/Jordan

In this work, a 3D groundwater flow model integrating all important geological features of the hydrogeological system is developed to investigate hydrological processes in the Wadi Kafrein area of Jordan. A large amount of available geological and hydrological data is integrated to construct a 3D groundwater flow model for the Wadi Kafrein area. Using the newly developed mapping approach, the translation of the highly detailed geological formations to an unstructured finite element grids, can be accomplished with high precision. The existing data set for model calibration is scarce, which is a typical situation for many hydrogeological case studies. At first, the steady state calibration of the groundwater model is carried out based on the observation wells. Then, the time and space-dependent recharge from precipitation are applied at the top surface of the finite element model. The transient simulation is conducted during the period of 1996–2008 considering the abstraction rates of the production wells and discharge of the springs. The calculated water levels are close to the observed values. The difference is partly caused by return flows from irrigation and the groundwater inflow from the adjacent aquifers which are not taken into consideration so far. Since the Wadi Kafrein area is an important agricultural area in the semiarid region of the Lower Jordan Valley, the model developed in this study can be regarded as a useful tool for analyzing the hydrological processes and improving groundwater management practices elsewhere affected by similar geological and hydrogeological conditions.     

Hydrochemistry and isotope geochemistry as tools for groundwater hydrodynamic investigation in multilayer aquifers: a case study from Lomellina, Po plain, South-Western Lombardy, Italy

A multicriteria approach in studying hydrodynamics of a multilayer aquifer system has been used in the Lomellina region (Northern Italy). It involves the reconstruction of the hydrogeological framework coupled to the definition of the hydrochemical and isotopic features of the aquifers. A shallow phreatic aquifer, reaching depths of about 60–80 m from the surface, and deeper aquifers containing confined groundwater, were distinguished. Groundwater generally shows mineralisation decreasing with depth; dissolved ions depict calcium-bicarbonate hydrochemical facies and stable isotopes define the recharge mechanisms, the origin of groundwater, and the hydraulic confinement of deep aquifers. The phreatic aquifer is fed by local infiltration and by streams and irrigation channels. Tritium and Carbon-14 groundwater dating indicate long residence times (on the order of thousands of years) for confined aquifers. The confined aquifers show essentially passive hydrodynamic conditions and maintain a higher piezometric level than the phreatic aquifer. This inhibits the possibility of recent water penetrating far below the surface. The hydrogeological setting of the Lomellina region displays features which are common to other sectors of the Po plain. As a consequence, the results of this study, although conducted on a restricted area, are highly illustrative of groundwater hydrodynamics in large sedimentary aquifers.     

Impact of groundwater withdrawals on the interaction of multi-layered aquifers in the Viterbo geothermal area (central Italy)

The impact of groundwater withdrawals on the interaction between multi-layered aquifers with different water qualities in the Viterbo geothermal area (central Italy) was studied. In this area, deep thermal waters are used to supply thermal spas and public pools. A shallow overlying aquifer carries cold and fresh water, used for irrigation and the local drinking-water supply. Starting with a conceptual hydrogeological model, two simplified numerical models were implemented: a steady-state flow model of the entire groundwater system, and a steady-state flow and heat transport model of a representative area, which included complex interactions between the aquifers. The impact of increased withdrawals associated with potential future development of the thermal aquifer must be considered in terms of the water temperature of the existing thermal sources. However, withdrawals from the shallow aquifer might also influence the discharge of thermal sources and quality of the water withdrawn from the shallow wells. The exploitation of the two aquifers is dependent on the hydraulic conductivity and thickness of the intervening aquitard, which maintains the delicate hydrogeological equilibrium. Effective methods to control this equilibrium include monitoring the vertical gradient between the two aquifers and the residual discharge of natural thermal springs.     

Groundwater flow model of the Pipiripau watershed, Federal District of Brazil

In order to understand the groundwater dynamics and to improve the management of water resources in the Federal District of Brazil, this research proposes a 3D groundwater flow model to represent the groundwater level and flow system. The selected test site was the Pipiripau catchment. The development of the model was based on available geological, hydrogeological, geomorphological, climatological and pedological data. Geological and hydrogeological data were used to generate the 3D groundwater flow model. The 3D mesh elements of the domain were generated through the Groundwater Modeling System software, based on the logs of the well materials. The numerical simulation of the finite element method was implemented in the framework of the scientific software OpenGeoSys. With the 3D mesh-appropriated boundary conditions, annual average infiltration data and hydrogeological parameters were incorporated. Afterwards, the steady-state model was calibrated by the PEST software using available data of the water level from wells. The results showed the distribution of the steady-state hydraulic heads in the model domain, where the highest values occurred in the east and west recharge areas and the lowest values were found in the southwest of the basin. The results of this study can be a used as initial condition for the transient groundwater flow simulation and to provide a scientific basis for water resource management.     

Numerical groundwater-flow modeling to evaluate potential effects of pumping and recharge: implications for sustainable groundwater management in the Mahanadi delta region,India

Process-based groundwater models are useful to understand complex aquifer systems and make predictions about their response to hydrological changes. A conceptual model for evaluating responses to environmental changes is presented, considering the hydrogeologic framework, flow processes, aquifer hydraulic properties, boundary conditions, and sources and sinks of the groundwater system. Based on this conceptual model, a quasi-three-dimensional transient groundwater flow model was designed using MODFLOW to simulate the groundwater system of Mahanadi River delta, eastern India. The model was constructed in the context of an upper unconfined aquifer and lower confined aquifer, separated by an aquitard. Hydraulic heads of 13 shallow wells and 11 deep wells were used to calibrate transient groundwater conditions during 1997–2006, followed by validation (2007–2011). The aquifer and aquitard hydraulic properties were obtained by pumping tests and were calibrated along with the rainfall recharge. The statistical and graphical performance indicators suggested a reasonably good simulation of groundwater flow over the study area. Sensitivity analysis revealed that groundwater level is most sensitive to the hydraulic conductivities of both the aquifers, followed by vertical hydraulic conductivity of the confining layer. The calibrated model was then employed to explore groundwater-flow dynamics in response to changes in pumping and recharge conditions. The simulation results indicate that pumping has a substantial effect on the confined aquifer flow regime as compared to the unconfined aquifer. The results and insights from this study have important implications for other regional groundwater modeling studies, especially in multi-layered aquifer systems.     

Multi-scale aquifer characterization and groundwater flow model parameterization using direct push technologies

Direct push (DP) technologies are typically used for cost-effective geotechnical characterization of unconsolidated soils and sediments. In more recent developments, DP technologies have been used for efficient hydraulic conductivity (K) characterization along vertical profiles with sampling resolutions of up to a few centimetres. Until date, however, only a limited number of studies document high-resolution in situ DP data for three-dimensional conceptual hydrogeological model development and groundwater flow model parameterization. This study demonstrates how DP technologies improve building of a conceptual hydrogeological model. We further evaluate the degree to which the DP-derived hydrogeological parameter K, measured across different spatial scales, improves performance of a regional groundwater flow model. The study area covers an area of ~60 km² with two overlying, mainly unconsolidated sand aquifers separated by a 5–7 m thick highly heterogeneous clay layer (in north-eastern Belgium). The hydrostratigraphy was obtained from an analysis of cored boreholes and about 265 cone penetration tests (CPTs). The hydrogeological parameter K was derived from a combined analysis of core and CPT data and also from hydraulic direct push tests. A total of 50 three-dimensional realizations of K were generated using a non-stationary multivariate geostatistical approach. To preserve the measured K values in the stochastic realizations, the groundwater model K realizations were conditioned on the borehole and direct push data. Optimization was performed to select the best performing model parameterization out of the 50 realizations. This model outperformed a previously developed reference model with homogeneous K fields for all hydrogeological layers. Comparison of particle tracking simulations, based either on the optimal heterogeneous or reference homogeneous groundwater model flow fields, demonstrate the impact DP-derived subsurface heterogeneity in K can have on groundwater flow and solute transport. We demonstrated that DP technologies, especially when calibrated with site-specific data, provide high-resolution 3D subsurface data for building more reliable conceptual models and increasing groundwater flow model performance.     

Numerical simulation of groundwater flow and contamination transport in Nahavand plain aquifer,west of Iran

Numerical simulation of groundwater flow used for the estimation of hydraulic and hydrologic parameters which is an important tool for the management of aquifers. This study presents the results of a mathematical model developed for the simulation of groundwater flow in Nahavand plain aquifer in the southwest Hamadan province. For this purpose Groundwater Modeling Software (GMS) was used which supports the MODFLOW-2000 code. After gathering required data such as the hydrological, hydrogeological and topography maps, a 3D hydrogeological model of plain was constructed with borehole and surface elevation data. Then MODFLOW was used for simulation of flow. After initial simulation of the flow, the model was calibrated in steady state with trial-and-error and parameter estimation methods the observed head of groundwater table monitoring data of 1997. Results of calibration show that error between observed head and computed head is in allowable range. Also results of computed head with model show that groundwater flow is in the direction of the dominate slope (southeast to northwest). Finally MODPATH code which simulates advective transport of particles was used for estimation of flow path and source of contaminants.     

Highly parameterized model calibration with cloud computing: an example of regional flow model calibration in northeast Alberta,Canada

Expanding groundwater datasets collected by automated sensors, and improved groundwater databases, have caused a rapid increase in calibration data available for groundwater modeling projects. Improved methods of subsurface characterization have increased the need for model complexity to represent geological and hydrogeological interpretations. The larger calibration datasets and the need for meaningful predictive uncertainty analysis have both increased the degree of parameterization necessary during model calibration. Due to these competing demands, modern groundwater modeling efforts require a massive degree of parallelization in order to remain computationally tractable. A methodology for the calibration of highly parameterized, computationally expensive models using the Amazon EC2 cloud computing service is presented. The calibration of a regional-scale model of groundwater flow in Alberta, Canada, is provided as an example. The model covers a 30,865-km² domain and includes 28 hydrostratigraphic units. Aquifer properties were calibrated to more than 1,500 static hydraulic head measurements and 10 years of measurements during industrial groundwater use. Three regionally extensive aquifers were parameterized (with spatially variable hydraulic conductivity fields), as was the aerial recharge boundary condition, leading to 450 adjustable parameters in total. The PEST-based model calibration was parallelized on up to 250 computing nodes located on Amazon’s EC2 servers.     

Numerical simulation of groundwater flow for a coastal plain in Japan: data collection and model calibration

Using a three-dimensional finite element model, this study characterizes groundwater flow in a costal plain of the Seto Inland Sea, Japan. The model characterization involved taking field data describing the aquifer system and translating this information into input variables that the model code uses to solve governing equations of flow. Geological geometry and the number of aquifers have been analyzed based on a large amount of geological, hydrogeological and topographical data. Results of study demonstrate a high correlation between the ground surface elevation and the groundwater level in the shallow coastal aquifer. For calibrating the numerical groundwater model, the groundwater flow was simulated in steady state. In addition, the groundwater level and trend in the transient state has also been elucidated. The numerical result provides excellent visual representations of groundwater flow, presenting resource managers and decision makers with a clear understanding of the nature of the types of groundwater flow pathways. Results build a base for further analysis under different future scenarios.     

The typology of Irish hard-rock aquifers based on an integrated hydrogeological and geophysical approach

Groundwater flow in hard-rock aquifers is strongly controlled by the characteristics and distribution of structural heterogeneity. A methodology for catchment-scale characterisation is presented, based on the integration of complementary, multi-scale hydrogeological, geophysical and geological approaches. This was applied to three contrasting catchments underlain by metamorphic rocks in the northern parts of Ireland (Republic of Ireland and Northern Ireland, UK). Cross-validated surface and borehole geophysical investigations confirm the discontinuous overburden, lithological compartmentalisation of the bedrock and important spatial variations of the weathered bedrock profiles at macro-scale. Fracture analysis suggests that the recent (Alpine) tectonic fabric exerts strong control on the internal aquifer structure at meso-scale, which is likely to impact on the anisotropy of aquifer properties. The combination of the interpretation of depth-specific hydraulic-test data with the structural information provided by geophysical tests allows characterisation of the hydrodynamic properties of the identified aquifer units. Regionally, the distribution of hydraulic conductivities can be described by inverse power laws specific to the aquifer litho-type. Observed groundwater flow directions reflect this multi-scale structure. The proposed integrated approach applies widely available investigative tools to identify key dominant structures controlling groundwater flow, characterising the aquifer type for each catchment and resolving the spatial distribution of relevant aquifer units and associated hydrodynamic parameters.     

Investigating groundwater flow components in an Alpine relict rock glacier (Austria) using a numerical model

Relict rock glaciers are complex hydrogeological systems that might act as relevant groundwater storages; therefore, the discharge behavior of these alpine landforms needs to be better understood. Hydrogeological and geophysical investigations at a relict rock glacier in the Niedere Tauern Range (Austria) reveal a slow and fast flow component that appear to be related to the heterogeneous structure of the aquifer. A numerical groundwater flow model was used to indicate the influence of important internal structures such as layering, preferential flow paths and aquifer-base topography. Discharge dynamics can be reproduced reasonably by both introducing layers of strongly different hydraulic conductivities or by a network of highly conductive channels within a low-conductivity zone. Moreover, the topography of the aquifer base influences the discharge dynamics, which can be observed particularly in simply structured aquifers. Hydraulic conductivity differences of three orders of magnitude are required to account for the observed discharge behavior: a highly conductive layer and/or channel network controlling the fast and flashy spring responses to recharge events, as opposed to less conductive sediment accumulations sustaining the long-term base flow. The results show that the hydraulic behavior of this relict rock glacier and likely that of others can be adequately represented by two aquifer components. However, the attempt to characterize the two components by inverse modeling results in ambiguity of internal structures when solely discharge data are available.