Global population is expected to grow from more than seven billion at present to nine billion by the year 2050. As a result, resource issues are becoming increasingly severe. The questions raised in connection with natural resources are practical, but also philosophical and political.Alluvial groundwater is becoming increasingly important for drinking water supply, but also agriculture and other human needs. Human civilisations developed in alluviums during the Holocene. Armies, roads, trade and agglomerations largely concentrated in river valleys. Alluviums are resource treasuries (water, forests, farmland, etc.), but at the same time they are exposed to pressures from the population and economy. These threats to alluvial plains and alluvial aquifers require very careful planning and persistent implementation of protection measures.Sudden social and natural changes increasingly lead the world into a tangle of global events and problems whose outcomes are not easy to perceive, let alone influence. One of the factors that can help is knowledge or, in other words, expertise focussed on a single problem or area. The ability to synthesise information and master comprehensive models is also extremely important.This book, a monograph, is a modest attempt to contribute to the understanding of planetary water management, groundwater and certain natural processes in alluviums. It comprehensively encompasses current topics associated with the state, processes and problems of alluvial aquifers and is devoted to professionals, experts, professors and students in advanced stages of learning.ISBN: 9781789060898 (Paperback)ISBN: 9781789060904 (eBook)ISBN: 9781789060911 (ePUB)

An analysis of the dynamics of the process of biochemical colmation of laterals of radial wells at the Belgrade groundwater source is presented. A very good correlation between the rate of forming of the colmations and the concentration of bivalent iron was obtained, on the basis of which the maximum recommended flows and velocities were defined, which are in good agreement with the values from previous articles and studies. The effects of regenerations on yield and the total volume of extracted water (up to 2 times higher than in the case of no regeneration) were investigated using a mathematical and software model. A correlation was developed linking the ratio of the amounts of water extracted with and without regeneration, to the aquifer hydraulic resistance, the coefficient of local hydraulic losses reduction due to regeneration, and the number of regenerations. The factor equal to the square root of the number of regenerations increased by one was added to the expressions for the maximum recommended values of inlet velocities and flows per lateral. The differences in flows and extracted volumes between operating modes with constant flow between regenerations and a constant, minimal water level were also examined using the model. The ratio between the total extracted volumes when the drawdown is kept equal to maximum and when the flow between the regenerations is kept constant reaches up to 1.25.

A convergent flow field tracer test, in two phases, with injection of sodium chloride solution, was conducted on a pumping well and neighboring piezometers belonging to the Kovin-Dubovac area drainage system, on the Serbian sector of the Danube River. The initial goal was to determine the values of hydrogeological parameters in order to analyze the results of the subsequent experiments involving injection of the selected solutes. SEAWAT code (through the Visual Modflow™ 2011 interface), as well as the newly developed analytical model for multilayer setting (1D transport solution for tracer injected as a Dirac impulse in a radial convergent flow field), was used to develop and calibrate a model of the studied portion of the aquifer. The new analytical model demonstrated a very good match to the measured values and to the results of numerical simulation, which indicates that it can be of great utility in characterizing transport conditions. PRACTITIONER POINTS: Results confirm the conclusions of research papers on tracer tests that 10-m scale tests regularly point to heterogeneous aquifer. New analytical 1D radial transport model for multilayer setting demonstrated a very good match with numerical simulation and experimental data. Developed analytical model is usable for characterizing transport conditions in a radial convergent multilayer flow field or other settings.

A part of the Balkan ultramafic massif is situated in western Serbia and belongs to a mountain range with several prominent peaks, including Mt. Tara, Mt. Zlatibor, and Mt. Zlatar. The porosity of ultramafic rocks is generally very low, such that they are classified as nearly or completely waterless rocks. However, due to tectonic activity and exogenic processes over geologic time, some ultramafic rocks exhibit a certain level of secondary fracture porosity. Hydraulically interconnected fractures can form aquifers of the fractured type, such as the one found in Gruda on Mt. Zlatibor. On this location, the quality parameters of the groundwater in the fractured aquifer, drained via a spring called Bijela eesma, prompted detailed multidisciplinary investigations aimed at defining the elements of the aquifer for commercial water bottling purposes. Given that the investigations were comprehensive, the results allowed high-quality interpretation of the hydrogeologic conditions and provided the background for developing a hydrodynamic model of the fractured hydrogeologic system in the ultramafic rocks at Gruda. Modfiow software was used for modeling. This software is primarily intended for intergranular aquifers, but no programs are available for fractured aquifers in hard rocks with pronounced discontinuities. Modeling of the fractured aquifer in the ultramafic rocks at Gruda provided the following information: size of active infiltration surface, hydraulic conductivity of the porous medium, rate of recharge, residence time of a drop of groundwater from entry to exit, graphical representation of streamlines, and the like. Despite these difficulties, the results are satisfactory. The values of the analyzed parameters are believed to be objective and indicate a certain possibility of using Modflow in hydrodynamic modeling and solving hydrogeologic problems that involve hard rocks and fractured porosity. In practice, this is especially important for sanitary protection zoning of groundwater sources that rely on fractured aquifers.

We consider non-linear multi-point flux approximations (MPFA) scheme for flow simulations in a model of anisotropic porous medium that includes wells. The hydraulic head varies logarithmically and its gradient changes rapidly in the well vicinity. Due to this strong non-linearity of the near-well flow, use of the MPFA scheme in the near well region results in a completely wrong total well flux and an inaccurate hydraulic head distribution. In this article we propose correction of the MPFA scheme. The outcome is a scheme that is second-order accurate even in the well vicinity for anisotropic medium. Solution obtained with this scheme respects minimum and maximum principle, and also, it is non-oscillating.

The outcomes of a study on groundwater flow from a river to a radial collector well are presented in the paper. The considered well, RB-16, is part of a groundwater source that provides water supply to Belgrade (Serbia). The source relies on the alluvial aquifer of the Sava River. The groundwater is mildly anoxic (Eh ~ 125 mV, Fe2+ = 0.46 mg/L, NO3 ~ 0.24 mgN/L, O2 ~ 0.1 mg/L). The paper is specific in the sense that it presents a novel approach to the definition of water well susceptibility to iron incrustation in an anoxic alluvial setting. Maximum permissible screen entrance velocities, as well as the structural characteristics of the horizontal screens and the radial collector well itself, are determined based on correlations established between the rate of well incrustation, redox potential, iron concentration in groundwater, and screen entrance velocities. One of the criteria is that the hydraulic resistances, caused by the precipitation of iron on the horizontal screens, are being lower than specified. The correlations between maximum permissible screen entrance velocities (the velocities that still allow a lower-than-specified increase in local hydraulic resistances at the entrance to the screens) and biochemical indicators (Eh, Fe2+) were taken from previous papers by the same authors and their associates. Original software was used for hydraulic analysis of the potential capacity of the location of well RB-16. The software supports 3D analysis, including boundary conditions, and was adapted for this particular purpose.

In radial collector well design or rehabilitation it is extremely important to define the capacity of the location and the long-term sustainable discharge of the well. Where incrustation occurs, groundwater entrance velocities at horizontal screens also need to be determined. At Belgrade Groundwater Source, maximum permissible screen entrance velocities are correlated with the oxic state of the aquifer, expressed via the redox potential, and the concentration of bivalent iron in the groundwater. The entrance velocities limit the rate of screen incrustation and are based on the maximum permissible increase in local hydraulic resistance at the screens. This is a novel approach on a global scale. In the case of anoxic groundwater, the derived permissible entrance velocities are much lower than estimated by standard, commonly used methods. The new approach is believed to be a significant contribution to well design. Jaroslav Cerni Institute for the Development of Water Resources (JCI) has developed software for estimating 3D groundwater flow, which relatively easily and realistically simulates horizontal screens and riverbed configuration and conductivity. The software is an effective tool for determining the capacity of the location and of the radial collector well itself. It is especially useful where the aquifer system comprises a semi-permeable interbed between the water-bearing layer, in which the screens are emplaced, and the overlying strata. A comparative hydrodynamic analysis of two wells at Belgrade Groundwater Source is presented in the paper. One of the wells (RB-16) clearly reflects the presence of a semi-permeable interbed, whereas the other (RB-46) does not.

The application of a mathematical model that analyzes the transport of selected pharmaceuticals from the Sava River to a corresponding radial collector well at Belgrade?s groundwater source is assessed. The occurrence of the selected pharmaceuticals in surface water and the corresponding well was monitored from 2009 to 2015. The pharmaceuticals selected for the present study are carbamazepine, trimethoprim, and metamizole metabolites 4-AAA and 4-FAA. Transport is analyzed based on experimental data (sorption isotherms) and a field tracer experiment that includes injection of the selected pharmaceuticals. The analysis shows that sorption of carbamazepine is relatively low and that this pharmaceutical does not degrade under the studied conditions, so it is not possible to accurately determine the degradation half-life. Trimethoprim is detected in the Sava River with an average concentration 8.5 ng/L, but there is no positive detection in well Rb-16. The average concentration of 4-AAA in the surface water is 34 ng/L and of 4-FAA 13 ng/L. The average concentrations of 4-FAAand 4-AAA in the groundwater are in the range from 1 and 1.85 ng/L. The objective of the research is to use an existing hydrogeologic model and apply a transport model to determine the minimum degradation half-life of the investigated pharmaceuticals.

We consider a finite volume method for a well-driven fluid flow in a porous medium. Due to the singularity of the well, modeling in the near-well region with standard numerical schemes results in a completely wrong total well flux and an inaccurate hydraulic head. Local grid refinement can help, but it comes at computational cost. In this article we propose two methods to address well singularity. In the first method the flux through well faces is corrected using a logarithmic function, in a way related to the Peaceman correction. Coupling this correction with a second-order accurate two-point scheme gives a greatly improved total well flux, but the resulting scheme is still not even first order accurate on coarse grids. In the second method fluxes in the near-well region are corrected by representing the hydraulic head as a sum of a logarithmic and a linear function. This scheme is second-order accurate.

To ensure the discrete maximum principle or solution positivity in finite volume schemes, diffusive flux is sometimes discretized as a conical combination of finite differences. Such a combination may be impossible to construct along material discontinuities using only cell concentration values. This is often resolved by introducing auxiliary node, edge, or face concentration values that are explicitly interpolated from the surrounding cell concentrations. We propose to discretize the diffusive flux after applying a local piecewise linear coordinate transformation that effectively removes the discontinuities. The resulting scheme does not need any auxiliary concentrations and is therefore remarkably simpler, while being second-order accurate under the assumption that the structure of the domain is locally layered.

A water supply system including radial wells (RWs) is usually large, extending several tens of kilometers horizontally and is dozens of meters deep. An RW is a vertical shaft with lateral screens, which radially penetrate the soil. A large and complex 3D finite element (FE) mesh also needs to include laterals with cross-sectional dimensions measured in centimeters. An adequate representation of lateral screens by line elements, with nodes coinciding with the 3D FE mesh nodes, is desirable in order to simplify modeling, render the computation efficient, and present the results in an easily readable form. Line elements are introduced for the lateral screens and accuracy of the results is analyzed. It was found that the domain size of an RW (or laterals) has a more pronounced effect on accuracy than mesh density. The authors' conclusion is that the concept of 1D RW lateral screens representation is adequate for practical purposes.

An interpolation method for diffusion in anisotropic discontinuous media based on convex combinations and physical relationships is presented. The method is exact for any piecewise linear solution, even if the interpolation nodes lie on the opposite sides of a material discontinuity. Values in points that do not lie within the convex hull of interpolation nodes are computed using flux boundary conditions. The method permits interpolation in every point within most domains, while preserving the maximum and minimum principles. We propose to replace the interpolation techniques in several non-linear finite volume schemes with the present method. Additionally, it is demonstrated that the construction of a convex combination by a simple search strategy may not be economical or even feasible if the grid is distorted. An alternative search structure that behaves well in such cases is proposed. (C) 2013 Elsevier Inc. All rights reserved.

Research conducted at the Belgrade Groundwater Source in Serbia has shown that significant well screen clogging processes take place under reduced oxic and initial anoxic conditions. Criteria for the prevention, or deceleration, of clogging are becoming more relevant to well ageing, compared with classical, mechanical clogging criteria and the permissible entrance velocities derived from them. The research project was later expanded to encompass other alluvial sources, which feature distinct oxic conditions. This paper presents some of the outcomes of this project, which shed light on the correlation between certain important indicators of well screen clogging (such as the redox potential and iron concentration) and the rate of increase in local hydraulic resistance at the wells.

Evaluation of saturation and relative conductivity using analytical models such as Van Genuchten and Mualem formulae is computationally expensive because it requires evaluation of power functions with fractional exponent. For this reason, these models are tabulated and evaluated approximately using splines. Solution of Richards equation can be quite sensitive to the relative conductivity evaluation accuracy, requiring short spline sub-intervals, higher-order splines, or both. Pressure head variation can be large or not known in advance, for example if the unsaturated zone is large. This variation must be estimated and divided in short sub-intervals for spline interpolation. Such a table may require much memory. An alternative is to use non-uniform sub-intervals. Relative conductivity changes rapidly with the pressure head in a narrow region of higher saturation, and more slowly in drier conditions. Thus using short sub-intervals near the saturation point, and longer sub-intervals away from it, saves the memory and provides the accuracy. However, mapping the pressure head into non-uniform sub-intervals may require expensive evaluation of analytical functions, potentially annihilating the speedup achieved by the tabulation. In order to conserve the memory and speed up the computation, we propose such nonuniform division where mapping to sub-intervals is not much more expensive than in the uniform case.

The City of Belgrade receives most of its drinking water supply from the alluvial aquifer of the Sava River. The wells are radial, placed in the lower part of the aquifer, so they partly run below the Sava riverbed. However, the groundwater quality of the wells in one part of the source (near the confluence of the Sava and Danube rivers) is found to differ somewhat from the groundwater quality of the other wells. The finding gave rise to additional investigations. The results revealed the existence of a deeper, limestone aquifer which is isolated from upper alluvial sediments by a thick layer of clay in most of the terrain. The naturally potential hydraulic contact of the two aquifers was additionally maintained by well operation in this part of the source. According to multiple analyses of groundwater flow using a hydrodynamic mathematical model, a hydrogeological and hydraulic system of groundwater flow was defined. Although the wells are situated adjacent to the river, and some well laterals are below the riverbed, most of the groundwater that flows to the wells is partly from the wider zone of the alluvial aquifer, and partly from the deeper aquifer. The initial results of hydrochemical investigations also showed an unexpected, inverse oxic character of the groundwater in these two aquifers.

From 2005 to 2009, research was conducted at the Belgrade Groundwater Source (BGWS) to investigate the process of clogging of wells with horizontal lateral screens (radial wells). The clogging process was monitored via the kinetics of the increase in hydraulic losses at the laterals. A correlation of this process with the redox potential, the iron concentration in water, and the microbial population growth at the laterals and in their immediate vicinity was established. Research outcomes are presented here from a study of five wells where laterals were replaced between 2006 and 2008. Derived dependencies were later used to define the preferred approach to the installation and maintenance of well laterals at the BGWS. Results contribute to the study of well ageing caused by biochemical clogging.

Finite volume method for well-driven porous media flow which uses a computational mesh tailored for finite elements is presented. It replaces onedimensional elements used to model well drains in the original mesh with one-dimensional cells. It does not modify the original mesh by adding or moving nodes. It can handle the discontinuous anisotropic hydraulic conductivity. Special discretization of the flux between the porous medium and the drain is proposed. Numerical results are compared to an analytical solution.

A non-linear finite volume method with monotone matrix for the diffusion equation is presented. It does not extrapolate the primary variable to Neumann boundaries, as this was previously done in similar methods. This change results in faster convergence. Computation time is significantly shortened further using the reduced rank extrapolation method (RRE), and imposing an upper limit on the number of linear iterations per non-linear step. Second-order accuracy and performance improvement are demonstrated by numerical examples.

Over time, the radial collector wells of the Belgrade Groundwater Source, located in the alluvial sediments of the Sava River, exhibit a decline in discharge and a reduction in operating efficiency due to well ageing. An increase in hydraulic losses at the lateral screens, due to chemical and biochemical clogging, has been identified as the primary cause. Certain hydrogeological, hydrochemical and microbiological parameters reflect the well-ageing process and can, therefore, be considered as its indicators. An indicator-based determination of scale is an important aspect in the selection of appropriate well locations, structural characteristics, and maintenance approaches. Well ageing was studied over a period of 5 years (2005-2009). The objective was to investigate the causes of well ageing. The correlations established between the groundwater redox potential, the total iron concentration in groundwater, the grain-size distribution of the aquifer, and well discharge, are presented in the paper.