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Groundwater (GW) flooding mechanisms differ from river flooding, both spatially and temporally, and preventative methods against groundwater flooding must take this into account. Although groundwater flooding caused by a rise of river water seldom occurs, it can occasionally become severe and last for a long time if the river is significantly flooded. In the southwest portion of the research domain, Friedrichshafen, Germany, with a few urban communities, the level of the groundwater table was discovered to be roughly 1 m below the surface. In the study region, it is typical for the bottom level of the foundation of a single-story building to extend up to a depth of about 1.5 m. Therefore, flood mitigation methods are taken into account for the southwest portion of the study region. In this study, FEFLOW is used to explore the preventative methods for groundwater flooding caused by river water increase in urban settings, the spread of contamination, and the strategizing of effective mitigation solutions for flooding. The installation of a pumping well, drainage, and a barrier in the affected area are three different flood control strategies that are taken into consideration for the study area. Pumping well installation, reducing up to 1.5 m of hydraulic head, was found to be the most effective flood control measure locally in a small region. By contrast, removing groundwater by building drainage and barriers was shown to be ineffective for lowering the groundwater table over an extended region, and was significantly more expensive than the installation of wells. Additionally, when river flooding is taken into account, compared to the default scenario where no intake of water from the river is included along the western border of the study area, it was discovered that the spread of pollution (nitrate concentration) is significantly greater.

Water stress conditions associated with population growth, climate change, and groundwater contamination, represent a significant challenge for all stakeholders in the water sector. Increasing the resilience of Water Supply Systems (WSSs) becomes of fundamental importance: along with an adequate level of service, sustainability targets must be ensured. A long-term management strategy is strictly connected to a holistic approach, based on analyses at different scales. To this end, both groundwater modeling tools and water management models, with different spatial and temporal scales, are routinely and independently employed. Here, we propose a coupled approach combining: i) groundwater models (MODFLOW) to investigate different stress scenarios, involving climate change and anthropic activities; ii) water management models (Aquator), to assess the water resources availability and the best long-term management strategy for large-scale WSS. The management models are implemented starting from input and output flows derived by groundwater models: this leads to establish a comprehensive framework usually not defined in management models and including a quantitative characterization of the aquifer. The proposed methodology, general and applicable to any study area, is here implemented to the WSS of Reggio Emilia Province, and its main groundwater resource, the Enza aquifer, considering three different stress scenarios for groundwater models (BAU, ST1, and ST2), and for management strategies (BAU, BAURV2, ST2). Among the key results, we observe that coupling the two model types: i) allows evaluating water resources availability in connection with management rules; ii) leads to examining more realistic operation choices; iii) permits planning of infrastructures at basin scale.

Groundwater depletion poses a major threat to global groundwater resources with increasing trends due to natural and anthropogenic activities. This study presents a surface-groundwater framework for water resources modelling of ill-posed problems in hydrogeologically data-scarce areas. The proposed framework is based on the application of a conceptual water balance model and composed of surface hydrological (UTHBAL) and groundwater flow simulation with the integration of a Newton formulation of the MODFLOW-2005 code (MODFLOW-NWT) and PEST suite modules. The groundwater simulation includes a preprocessor tool for automated calibration and a post-processor tool for automated validation. The methodology was applied to a rural region of Central Greece, Lake Karla Basin, which is degraded due to groundwater resources overexploitation to cover irrigation water demands. The aquifer is modelled focusing on a precise simulation–validation procedure of the conceptual model. The groundwater model was calibrated with the calibration preprocessor tool for spatially distributed hydraulic conductivity with the pilot points method. The calibration process achieved satisfactory results as validated by the post-process analysis of observed and simulated water levels. The findings for the groundwater budget indicate that the groundwater system is still under intense pressure even though farming activity in recent years has turned to less water-intensive crops. HIGHLIGHT My research deals with the pilot points method on groundwater modelling in an area with scarce hydrogeologic data.

This study was performed while the author was at Purdue University. The author thanks Prof. Dr Bernard Engel for his acceptance as a visiting scholar at Purdue University. Also, the author thanks The Scientific and Technological Research Council of Turkey (TUBITAK) for financial support (No. 1059B191800383). The purpose of this study was to improve the optimization model for predicting more parameters in more difficult conditions (more grid cell numbers and high time interval numbers) than other studies in groundwater flow modelling. Also, the model needs fewer observation numbers for estimating parameters than other studies. In the present study, an optimization model based on model calibration was developed to estimate simultaneously four groundwater flow parameters - hydraulic conductivity, transmissivity, storage coefficient and leakance. The modified clonal selection algorithm, a class of artificial immune systems, was used as a heuristic optimization method. In order to simulate the groundwater flow, MODFLOW was used in conjunction with the model in MATLAB. The input files for MODFLOW were obtained by GMS groundwater simulator. The model was applied to two different hypothetical groundwater systems (two- and three-dimensional) under transient conditions to evaluate its performance. The results showed that the model was feasible for groundwater flow modelling and it could determine the groundwater flow parameters successfully with less observations and more grid cell numbers than the other studies. Scientific and Technological Research Council of Turkey (TUBITAK) [1059B191800383]

Groundwater is an important source of freshwater in many parts of the world. The use of groundwater resources is projected to rise significantly, especially as traditional surface water resources become less available due to changing precipitation patterns. Groundwater can also be an important pathway for contaminant transport including nutrients and pesticides to coastal environments. In order to quantify groundwater resources and its movement, a comprehensive understanding of aquifer systems and the factors that control groundwater flow and quality is needed., In this thesis, firstly, to test the effectiveness of different geological, hydrogeological and geophysical approaches to characterize aquifer settings, I compared and contrasted different methods in the Lake Haramaya watershed, Ethiopia (Chapter 2). The study used pumping test and vertical electrical sounding (VES) data to estimate aquifer transmissivity and hydraulic conductivity, where a 40% and 33% reduction in uncertainties were found, respectively, when the methods were combined rather than when VES data alone was used. Combining drill logs and geo-electrical resistivity data to develop the 3D geological setting of the aquifer system also identified lithologic units that were not detected using either method., In much larger regional aquifer systems where extensive drill log data was available (the Great Barrier Reef catchment), 3D geological and hydrogeological models were then constructed (Chapter 3). These models revealed previously unknown faults and aquifer units in the catchment., The fourth chapter then combined 3D geological and hydrogeological models with hydro-geochemical datasets to quantify the governing processes of groundwater flow and chemistry in the Raya Valley, Ethiopia. Evaluating the correlations between the ionic concentrations and the processes governing groundwater chemistry, the study showed that rock weathering, mineral dissolution, ion exchange and anthropogenic activities were the major processes governing the hydro-geochemical characteristics of the groundwater., These improved hydrogeological and hydro-geochemical conceptualization approaches were then combined with isotope analysis and groundwater chemistry to determine the legacy effects and drivers of nutrient and pesticide pollution in agriculturally impacted aquifers (Chapter 5)., Overall, the thesis closes crucial knowledge gaps in the understanding of hydrogeological systems and provides groundwater managers with a much better understanding of the system to make more effective groundwater management decisions relating to issues such as groundwater sustainability and pollution issues.

This paper concerns about a stepwise modelling procedure for groundwater flow simulation in a complex carbonate, folded and faulted, multilayer aquifer, in the Apennine chain in Central Ita-ly, which constitutes a source of good quality water for human consumption. A perennial river acts as the main natural drain for groundwater while sustaining valuable water related ecosys-tems. The spatial distribution of recharge was estimated using the Thornthwaite-Mather method on 60 years of climate data. The system was conceptualized as three main aquifers separated by two locally discontinuous aquitards. Three numerical models were implemented by gradually adding complexity to the model grid: single layer (2D), three layers (Quasi-3D), and five layers (Fully-3D), using an equivalent porous medium approach, in order to find the best solution with a parsimonious model setting. To overcome dry-cell problems in the Fully-3D model, the New-ton-Raphson formulation for MODFLOW-2005 was invoked. Calibration results show that a Fully-3D model was required to match the observed distribution of aquifer outflow to the river baseflow. The numerical model demonstrated the major impact of folded and faulted geological structures on controlling the flow dynamics in terms of flow direction, water heads and spatial distribution of the outflows to the river and springs.

PREFACE The Groundwater Modelling Decision Support Initiative (GMDSI) is an industry-funded and industry-aligned project focused on improving the role that groundwater modelling plays in supporting environmental management and decision-making. Over the life of the project, it will document a number of examples of decision-support groundwater modelling. These documented worked examples will attempt to demonstrate that by following the scientific method, and by employing modern, computer-based approaches to data assimilation, the uncertainties associated with groundwater model predictions can be both quantified and reduced. With realistic confidence intervals associated with predictions of management interest, the risks associated with different courses of management action can be properly assessed before critical decisions are made. GMDSI worked example reports, one of which you are now reading, are deliberately different from other modelling reports. They do not describe all of the nuances of a particular study site. They do not provide every construction and deployment detail of a particular model. In fact, they are not written for modelling specialists at all. Instead, a GMDSI worked example report is written with a broader audience in mind. Its intention is to convey concepts, rather than to record details of model construction. In doing so, it attempts to raise its readers’ awareness of modelling and data-assimilation possibilities that may prove useful in their own groundwater management contexts. The decision-support challenges that are addressed by various GMDSI worked examples include the following: • assessing the reliability of a public water supply; • protection of a groundwater resource from contamination; • estimation of mine dewatering requirements; • assessing the environmental impacts of mining; and • management of aquifers threatened by salt water intrusion. In all cases the approach is the same. Management-salient model predictions are identified. Ways in which model-based data assimilation can be employed to quantify and reduce the uncertainties associated with these predictions are reported. Model design choices are explained in a way that modellers and non-modellers can understand. The authors of GMDSI worked example reports make no claim that the modelling work which they document cannot be improved. As all modellers know, time and resources available for modelling are always limited. The quality of data on which a model relies is always suspect. Modelling choices are always subjective, and are often made differently with the benefit of hindsight. What we do claim, however, is that the modelling work which we report has attempted to implement the scientific method to address challenges that are typical of those encountered on a day-to-day basis in groundwater management worldwide. As stated above, a worked example report purposefully omits many implementation details of the modelling and data assimilation processes that it describes. Its purpose is to demonstrate what can be done, rather than to explain how it is done. Those who are interested in technical details are referred to GMDSI modelling tutorials. A suite of these tutorials has been developed specifically to assist modellers in implementing workflows such as those that are described herein. We thank and acknowledge our collaborators, and GMDSI project funders, for making these reports possible.

This paper deals with the double-constraint methodology for calibration of steady-state groundwater flow models. The methodology is based on updating the hydraulic conductivity of the model domain by comparing the results of two forward groundwater flow models: a model in which known fluxes are specified as boundary conditions and a model in which known heads are specified as boundary conditions. A new zone-integrated double-constraint approach is presented by partitioning the model domain in zones with presumed constant hydraulic conductivity (soft data), and the double-constraint methodology is reformulated accordingly. The feasibility of the method is illustrated by a practical case study involving a numerical steady-state groundwater flow model with about 3 million grid blocks, subdivided into four zones corresponding to the major hydrogeological formations. The results of the zone-integrated double-constraint method for estimating the horizontal and vertical hydraulic conductivities of the zones compare favourably with a classical model calibration based on minimisation of the differences between calculated and measured heads, while the double-constraint method proves to be more robust and computationally less cumbersome.

Despite the availability of numerical models, interest in analytical solutions of multidimensional advection-dispersion systems remains high. Such models are commonly used for performing Tier I risk analysis and are embedded in many regulatory frameworks dealing with groundwater contamination. In this work, we develop a closed-form solution of the three-dimensional advection-dispersion equation with exponential source decay, first-order reaction, and retardation, and present an approach based on some ease of use diagrams to compare it with the integral open form solution and with earlier versions of the closed-form solution. The comparison approach focuses on the relative differences associated with source decay and the effect of simulation time. The analysis of concentration contours, longitudinal sections, and transverse sections confirms that the closed-form solutions studied can be used with acceptable approximation in the central area of a plume bound transversely within the source width, both behind and beyond the advective front and for concentration values up to two orders of magnitude less than the initial source concentration. As the proposed closed-form model can be evaluated without nested numerical computations and with simple mathematical functions, it can be very useful in risk assessment procedures.

This work deals with the hydraulic phenomenon of the ascendant groundwater flow affecting the karst area of the Grassano and Telese springs (Campania, Southern Italy). It has been investigated through piezometric measurements, discharge and chemical-physical monitoring of springs and measurements of the radon 222Rn activity. The presence of ascendant flows is supported by numerous and different types of evidences in the area: location and topographical position of the springs; amazing density of sinkholes connected to geomorphic processes that develop below the topographic surface and involve the rising of CO2 and H2S rich waters; constancy of the temperature and the electrical conductivity of the spring waters over the time; fluctuation of the radon activity during the hydrological year; increasing of the hydraulic head with depth; presence of artesian conditions in the alluvial plain. Numerical simulations of the groundwater flow also support the general phenomenon of the ascendant flow in the discharge area and represent a useful background to interpret hydrological phenomena in the study area. The results of the simulations are suitable with all the hydrogeological processes observed in the area of the Grassano and Telese springs; this last is thought to belong to the regional groundwater flow system of the Matese massif and represents its discharge zone.

International audience; Limestone aquifers represent an important part of groundwater resources in the world. They are usually considered as fractured karstic rock formations. However, a different type, called weathered' or ghost-rock' karst aquifer has recently been highlighted. In this particular type of aquifer, the karst is not expressed as open conduits but consists in zones made of a residual alterite, resulting from the in-situ partial dissolution of limestone. These particular structures are crucial in some areas because they actually govern groundwater flow and transport in the aquifer. They have, however, never been studied from a hydrogeological perspective. In this study, we present a methodology to characterize and model such aquifers. Results show that the ghost-rock features are usually organized into networks, and that their hydraulic properties are variable within each feature, according to the limestone weathering intensity. Measurements in a specific aquifer in Belgium are presented. The modelling approach, derived from the common Equivalent Porous Medium approach, enables to spatially distribute the variable hydraulic properties within the features, from the hard fresh rock to the alterite, in finite difference grids. The method allows creating models including thousands of features and respecting correct connectivity relations. The approach is considered at different scales with varying grid cells sizes. Results show that the induced error increases significantly when the size of the grid cells exceeds the width of the main features controlling flow. The approach is applied on a case study consisting in dewatering operations in an exploited quarry located in a weathered karst aquifer. Presented results provide new insights regarding characterization and modelling of this kind of aquifers, and highlight their importance in hydrological studies.

This study uses groundwater isotopes and ion composition to verify model simulations and ecohydrological studies in the Drentsche Aa nature reserve in The Netherlands, which is representative for the northwestern wetland areas in the Ice Marginal Landscape zone. At eight field sites, a total of 24 samples were analysed for their 13 C, 14 C, 2 H, and 18 O isotopes and ionic composition. The isotopes indicate that most of the fen peatlands in the area depend on the exfiltration of sub-regional groundwater flows, which confirmed the previous model simulations and ecohydrological studies. At three sites, isotopes and ionic composition indicate that the groundwater from the sub-regional system has been replaced by local infiltrated rainwater, due to nearby groundwater abstractions for drinking water, which influenced the success rates of the restoration measures. Furthermore, the evidence from chloride and 14 C contents was found to indicate the presence of more saline groundwater, which are influenced by the groundwater flows near salt diapirs. Groundwater abstractions may enhance the upward flow of the saline groundwater to eventually exfiltrate at the wetlands, affecting the biodiversity of the nature reserve.

Model averaging makes it possible to use multiple models for one modelling task, like predicting a certain quantity of interest. Several Bayesian approaches exist that all yield a weighted average of predictive distributions. However, often, they are not properly applied which can lead to false conclusions. In this study, we focus on Bayesian Model Selection (BMS) and Averaging (BMA), Pseudo-BMS/BMA and Bayesian Stacking. We want to foster their proper use by, first, clarifying their theoretical background and, second, contrasting their behaviours in an applied groundwater modelling task. We show that only Bayesian Stacking has the goal of model averaging for improved predictions by model combination. The other approaches pursue the quest of finding a single best model as the ultimate goal, and use model averaging only as a preliminary stage to prevent rash model choice. Improved predictions are thereby not guaranteed. In accordance with so-called M -settings that clarify the alleged relations between models and truth, we elicit which method is most promising.

The use of fertilizers in greenhouse-grown crops can pose a threat to groundwater quality and, consequently, to human beings and subterranean ecosystem, where intensive farming produces pollutants leaching. Albenga plain (Liguria, Italy) is an alluvial area of about 45km2 historically devoted to farming. Recently the crops have evolved to greenhouses horticulture and floriculture production. In the area high levels of nitrates in groundwater have been detected. Lysimeters with three types of reconstituted soils (loamy sand, sandy clay loam and sandy loam) collected from different areas of Albenga plain were used in this study to evaluate the leaching loss of nitrate (NO3-) over a period of 12weeks. Leaf lettuce (Lactuca sativa L.) was selected as a representative green-grown crop. Each of the soil samples was treated with a slow release fertilizer, simulating the real fertilizing strategy of the tillage. In order to estimate the potential risk for aquifers as well as for organisms exposed via pore water, nitrate concentrations in groundwater were evaluated by applying a simplified attenuation model to the experimental data. Results were refined and extended from comparison of single effects and exposure values (Tier I level) up to the evaluation of probabilistic distributions of exposure and related effects (Tier II, III IV levels). HHRA suggested HI >1 and about 20% probability of exceeding RfD for all the greenhouses, regardless of the soil. ERA suggested HQ>100 for all the greenhouses; 93% probability of PNEC exceedance for greenhouses containing sand clay loam. The probability of exceeding LC50 for 5% of the species was about 40% and the probability corresponding to DBQ of DEC/EC50>0.001 was >90% for all the greenhouses. The significantly high risk, related to the detected nitrate leaching loss, can be attributed to excessive and inappropriate fertigation strategies.

Water availability restrictions are already a reality in several countries. This issue is likely to worsen due to climate change, predicted for the upcoming decades. This study aims to estimate the impacts of climate change on groundwater system in the Guarani Aquifer outcrop zone. Global Climate Models (GCM) outputs were used as inputs to a water balance model, which produced recharge estimates for the groundwater model. Recharge was estimated across different land use types considering a control period from 2004 to 2014, and a future period from 2081 to 2099. Major changes in monthly rainfall means are expected to take place in dry seasons. Most of the analysed scenarios predict increase of more than 2 ºC in monthly mean temperatures. Comparing the control and future runs, our results showed a mean recharge change among scenarios that ranged from ~-80 to ~+60%, depending on the land use type. As a result of such decrease in recharge rates, the response given by the groundwater model indicates a lowering of the water table under most scenarios.

The impact of climate change and Baltic Sea level rise on groundwater resources in a shallow, unconfined, low-lying coastal aquifer in Hanko, southern Finland, was assessed using the UZF1 model package coupled with the three-dimensional groundwater flow model MODFLOW to simulate flow from the unsaturated zone through the aquifer. The snow and PET models were used to calculate the surface water availability for infiltration from the precipitation data used in UZF1. Infiltration rate, flow in the unsaturated zone and groundwater recharge were then simulated using UZF1. The simulation data from climate and sea level rise scenarios were compared with present data. The results indicated changes in recharge pattern during 2071–2100, with recharge occurring earlier in winter and early spring. The seasonal impacts of climate change on groundwater recharge were more significant, with surface overflow resulting in flooding during winter and early spring and drought during summer. Rising sea level would cause some parts of the aquifer to be under sea level, compromising groundwater quality due to intrusion of sea water. This, together with increased groundwater recharge, would raise groundwater levels and consequently contribute more surface leakage and potential flooding in the low-lying aquifer.

The paper presents risk assessment methodology used within a Decision Support System for Water Management in the Vicinity of Open Cast Mines (DS WMVOC). The DSS was designed to aid in decision making regarding ground and surface water resources, by two potentially conflicting stake holders in Konin county (Central Poland) that is, the County Administration and the open pit mine industry. Estimates of potential changes in groundwater head are achieved by numerical modelling of the groundwater system in which the open cast mines and receptors are located. The evaluation of spatially and time‐distributed environmental risk is obtained by means of GIS supported Monte Carlo methodology. Calculations can be run in the DS WMVOC resulting maps of the risk to different receptor types, and maps of relative risk for different abstraction or dewatering scenarios, as well as an overall risk value for the region. Estimation of the magnitude of any adverse impact is related to the element (type of receptor) being impacted and a sensitivity rating has been devised for each receptor type. The risk estimation methodology implemented in the DS WMVOC was illustrated by analysis of two hypothetical groundwater management scenarios. Santrauka Straipsnyje pateikiama rizikos vertinimo metodika, naudojama netoli atvirųjų kasyklų esančių vandens išteklių valdymo sprendimų paramos sistemoje. Sprendimų paramos sistema (SPS) buvo sukurta siekiant priimti naudingus sprendimus, priešingus interesų turinčioms šalims, dėl požeminio ir paviršinio vandens išteklių. Konino regione (Vidurio Lenkija) konfliktuojančios pusės yra apskrities administracija ir atvirų kasyklų pramonės įmonė. Galimi požeminio vandens lygio pokyčiai įvertinami atliekant skaitmeninį požeminio vandens sistemos modeliavimą. Rizika aplinkai erdvės ir laiko požiūriu vertinama taikant GIS ir Monte Karlo metodologiją. Skaičiuojant sprendimų paramos sistema sudaro specialius rizikos žemelapius, atlieka bendra rizikos įvertinimą regione. Sprendimų paramos sistemoje įdiegta rizikos vertinimo metodologija pritaikyta analizuoti du hipotetinius požeminio vandens valdymo scenarijus. First published online: 10 Feb 2011 Reikšminiai žodžiai:sprendimų paramos sistema (SPS),GIS,rizikos įvertinimas,atvirosios kasyklos,požeminio vandens modeliavimas

The problem of identifying and reproducing the hydrological behaviour of groundwater systems can often be set in terms of ordinary differential equations relating the inputs and outputs of their physical components under simplifying assumptions. Conceptual linear and nonlinear models described as ordinary differential equations are widely used in hydrology and can be found in several studies. Groundwater systems can be described conceptually as an interlinked reservoir model structured as a series of nonlinear tanks, so that the groundwater table can be schematized as the water level in one of the interconnected tanks. In this work, we propose a methodology for inferring the dynamics of a groundwater system response to rainfall, based on recorded time series data. The use of evolutionary techniques to infer differential equations from data in order to obtain their intrinsic phenomenological dynamics has been investigated recently by a few authors and is referred to as evolutionary modelling. A st...

In this work, we propose some analytical solutions of the advection-dispersion equation and adopt them to solve a non-linear parameter estimation problem. A solution with no reactive term and another one with a unique coefficient representing the kinetic mechanisms of the solute decay in groundwater are described in detail and are then considered in the estimation procedure. To test the robustness of these analytical solutions if adopted in inverse problems, the anisotropic dispersion and kinetics are estimated using sets of experimental data simulated by Monte Carlo techniques. Cylindrical geometry is considered since large columns are the most common devices adopted to study both dispersion and kinetics mechanisms and, even if the solutions are expressed in terms of Bessel-function expansion, they give very good results in terms of reliability and precision of our estimates. Discussion of results is based on the analysis of residuals, variance-covariance matrix and bias of parameters. The influence of location and time of sampling and of the number of samples on the estimates of dispersion and kinetic parameters is also analysed by means of Analysis of Variance (ANOVA) and Fisher tests. Copyright © 2005 John Wiley & Sons, Ltd.

La nappe aquifère de Hesbaye située au Nord-Ouest de Liège (Belgique) est logée dans les craies du Crétacé, surmontées d'une épaisse couche de limon. L'alimentation en eau de la région est assurée par les 60 000 m3 extraits Joumel!ement des galeries captantes et des puits.Un modèle mathématique par éléments finis a été construit pour simuler numériquement le comportement de l'aquifère en régime transitoire. La complexité de la géologie locale a nécessité l'emploi d'une méthode par éléments finis permettant une discrétisatlon 30 souple et détaillée de la zone étudiée, modélisation réalisée avec un maillage fixe en condition de nappe libre.Des développements numériques comprenant la simulation de la surface libre en mode transitoire, ont été introduits dans le modèle LAGATHER du programme LAGAMINE (Université de Liège). Le programme a été testé sur des exemples bidimensionnels avant d'étre appliqué en 30 à l'aquifère de Hesbaye.La discrétisation et les principaux résultats sont présentés., The Hesbaye aquifer located in Cretaceous chalks near Liège (Belgium), is recharged by infiltration through the overlying loess and conglomerate.Wells and collecting adits produce a daily flow of 60 000 m3 out of this aquifer, to provide the alimentation of the area of Liège and its suburbs.More Man 500 boreholes, plezometers and wells give many informations for the idealization and the calibration procedures. Variation ranges of permeability and effective porosity are determined from 150 pumping tests. The main drainance axis of the aquifer (called « dry valleys ») are located and characterized by higher permeabilities.Finite element modelling has been developed to foresee the evolution of the water table and to get some additional informations especially about these main drainance axis.The modelling method is based on the LAGAMINE code (from Liège University). The LAGATHER code is one of the module of the LAGAMINE which is initially adapted to treat non-linear thermic problems. Here, it has been developed to compute flows in porous media in transient conditions. The water table is calculated with a fixed mesh structure using a new method developed by (CHARLIER et al., 1988). Constitutive laws of the flow are changed to take into account the state of saturation or no-saturation of the media. Then the flow equation (the Darcy's law) becomes non-linear. The transition from unsaturated to saturated field is treated at a constant zero pressure, according to the analogy with thermodynamical phase changes at constant temperature. The method has been checked on uniaxial and two dimensionnal sections.3D discretisation and modelling of the whole aquifer has been realized. The problem requires about 2 670 8-nodes isoparametric brick finite elements. The complexity of the geological conditions justifies fully the use of finite element method by the diversity and the wide range of the hydrogeological parameters to introduce in the model.The discretisation is described and some of the must significant results are presented.

Axisymmetric flow to a well is an important topic of groundwater hydraulics, the simulation of which depends on accurate computation of head gradients. Groundwater numerical models with conventional rectilinear grid geometry such as MODFLOW (in contrast to analytical models) generally have not been used to simulate aquifer test results at a pumping well because they are not designed or expected to closely simulate the head gradient near the well. A scaling method is proposed based on mapping the governing flow equation from cylindrical to Cartesian coordinates, and vice versa. A set of relationships and scales is derived to implement the conversion. The proposed scaling method is then embedded in MODFLOW 2000. To verify the accuracy of the method steady and unsteady flows in confined and unconfined aquifers with fully or partially penetrating pumping wells are simulated and compared with the corresponding analytical solutions. In all cases a high degree of accuracy is achieved.

A tracer test to examine in situ denitrification in shallow groundwater by a piezometer with a packer system used bromide as a tracer of dilution and acetylene (10%) to block the denitrification process at the nitrous oxide stage. During the test, dissolved oxygen, nitrate (NO3‾), bromide (Br‾), nitrous oxide (N2O) and dissolved organic carbon (DOC) were measured. To calibrate the experimental method, comparison with numerical simulations of the groundwater transfer were carried out, taking into account the environmental characteristics. The method was tested by measurements undertaken in different environmental conditions (geology, land use and hydrology) in two riparian wetlands. Denitrification rates measured by this method ranged from 5.7 10-6 g N-NO3‾L-1 h-1 to 1.97 10-3 g N-NO3‾L-1 h-1 The method is applicable in shallow aquifers with a permeability from 10-2 to 10-4m s-1. Keywords: denitrification, shallowaquifer, groundwater modelling, wetlands, nitrate-nitrogen, packer system

Die genaue Kenntnis über den Wasserhaushalt stellt die Grundlage für die Bewirtschaftung der Ressource Wasser dar. Im urbanen Raum spielen dabei die siedlungshydrologischen Randbedingungen, wie Versiegelung, Anschlussgrad an die Kanalisation oder wasserbauliche Eingriffe, eine nicht zu vernachlässigende Rolle. Zur Quantifizierung der verschiedenen Wasserhaushaltsgrößen wurde ein konzeptioneller Ansatz entwickelt, der die jeweiligen Randbedingungen berücksichtigt und deren gegenseitige Beeinflussung abbildet. Hierbei muss der Einfluss auf den Wasserhaushalt auch bei veränderten Bedingungen simulierbar sein. Als Untersuchungsgebiet wurde das Gebiet der Wuhle, ein rechter Nebenfluss der Spree, gewählt, da es alle relevanten Aspekte der Wasserwirtschaft beinhaltet. Die Wuhle entspringt auf der Barnim-Grundmoränenhochfläche bei Ahrensfelde und mündet nach etwa 15,7 km Lauflänge im Stadtteil Köpenick in die Spree. Der Ansatz beruht auf der Berechnung der Wasserhaushaltsgrößen mit Hilfe eines flächendifferenzierten Verfahrens zur Ermittlung des Gesamtabflusses aus Niederschlag abzüglich der Verdunstung sowie dessen Aufteilung in einen oberirdischen und einen unterirdischen Teil. Zur Verifizierung der wasserhaushaltlich bestimmten Abflussgrößen wurden detaillierte hydraulische Untersuchungen an der Wuhle durchgeführt und abschnittsweise interpretiert. Anschließend wurde mit Hilfe der Förderdaten der Wasserwerke eine Grundwasserhaushaltsbilanz durchgeführt. Im Ergebnis ließ sich hydrogeologisch der Anteil an Uferfiltrat an der Gesamtfördermenge ermitteln. Zur Simulation des Einflusses des Wasserhaushaltes und der Grundwassernutzung auf den Grundwasserkörper wurde mit Hilfe des Simulators FEFLOW© eine numerische Modellierung der Strömungsverhältnisse durchgeführt. Über den Abgleich der simulierten Grundwasserhöhen mit den Grundwasserständen aus der Stichtagsmessung erfolgte eine zusätzliche Überprüfung der wasserhaushaltlich berechneten Abflussgrößen., The exact knowledge of the water balance is the basis of the water supply and distribution within a catchment area. In an urban area the boundary conditions of the civil engineering like the sewer system or the hydraulic engineering plays an important role. To quantify the water balance a conceptual approach was developed which takes the current conditions and their interdependence into consideration. The impact of changing conditions on the water balance can also be simulated. As investigation area the catchment of the Wuhle River was chosen because it includes all relevant aspects of water management. The Wuhle River has its source on the ground moraine of the Barnim plateau directly at the city boundary in Ahrensfelde and reaches the Spree in the quarter Köpenick after about 15.7 km. This method uses a differentiated calculation by area to determine the total outflow of rainfall minus evaporization. It also determines the submontane and aboveground distribution. For verification purposes detailed hydraulic investigations were carried out at the Wuhle. With the production rate of the waterworks the groundwater balance was then calculated. As a result the amount of bank filtrate of the total groundwater withdrawal was determined in a hydro geological way. Using the simulation software FEFLOW© a numeric model of the flow pattern was created to simulate the influence on the water balance and the groundwater. The displayed subterranean catchment area of the water work Wuhlheide was based on the water table contours which were interpolated from a fixed date measurement of the groundwater heads. By comparing the simulated groundwater heads and the water levels from the fixed date measurement an additional verification of the water balance was realised.

A contaminated alluvial aquifer, in a former gasworks factory and discharging to an adjacent river, was the object of field and laboratory investigations to assess pollutant attenuation and dispersion. Various organic and inorganic compounds were found in the aquifer in concentrations exceeding regulatory values, among them, benzene, which was presenting the major worry for off-site dispersion, mainly due to its mobility and high concentration, i.e. up to 750 mg L-1 in the source zone. However, benzene could never be detected near the river which is about 160 m downgradient the main source. Due to redox conditions of the aquifer, heavy metals were almost immobile, thus not posing a major risk of dispersion off-site the brownfield. Benzene concentrations together with redox conditions in the aquifer, suggested that benzene degradation was mainly occurring within 100 m distance from the contaminant source under anoxic conditions, and most probably with sulphate as main oxidant. A numerical groundwater flow and transport model, calibrated under transient conditions, was used to simulate benzene attenuation in the alluvial aquifer towards the Meuse River. The mean benzene degradation rate used in the model was quantified in situ along the groundwater flow path using compound-specific carbon isotope analysis (CSIA). The results of the solute transport simulations confirmed that benzene concentrations decreased almost five orders of magnitude 70 m downgradient the source. Simulated benzene concentrations were found to be below the detection limit in the zone adjacent to the river and consistent with the absence of benzene in downgradient piezometers located close to the river. In a transient model scenario including groundwater-surface water dynamics, benzene concentrations were observed to be inversely correlated to the river water levels, leading to the hypothesis that benzene dispersion is mainly controlled by natural attenuation and river fluctuations.

Results of purposeful groundwater monitoring and modelling studies are presented, which were carried out in order to better understand groundwater flow patterns from the “Vector” site for near-surface radioactive waste disposal and storage in the Chornobyl exclusion zone towards river network. Both data of observations at local-scale monitoring well network at “Vector” site carried out in 2015 - 2016 and modelling analyses using the regional groundwater flow model of Chornobyl exclusion zone suggest that the groundwater discharge contour for water originating from “Vector” site is Sakhan River, which is the tributary to Pripyat River. The respective groundwater travel time is estimated at 210 - 340 years. The travel times in subsurface for 90Sr, 137Cs, and transuranium radionuclides (Pu isotopes, 241Am) are estimated respectively at thousands, tenths of thousands, hundreds of thousands – million of years. These results, as well as presented data of analyses of lithological properties of the geological deposits of the unsaturated zone at “Vector” site, provide evidence for good protection of surface water resources from radioactivity sources (e.g., radioactive wastes) to be disposed in the near-sursface facilities at “Vector” site.