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About this book

This textbook provides a complete introduction to Hydrogeology. It is a comprehensive reference for earth science professionals involved in groundwater exploitation as well as for geotechnical engineers. This English translation of the German textbook "Hydrogeologie" by Hölting & Coldewey, which has been published in its 8th edition, provides insights into the sources and reservoirs of groundwater, the dynamics of fluid flow, and the physical and chemical composition of groundwater. It also gives an overview about the economic value of groundwater and its exploitation and use. A consistent use of the internationally accepted SI units as well as the formula symbols in the text contributes to the understandability.

Table of Contents


1. Introduction

Water is needed in all aspects of life. The general objective is to make sure that adequate supplies of water of good quality are maintained for the entire population of this planet, while preserving the hydrological, biological and chemical functions of ecosystems, adapting human activities within the capacity limits of nature and combating vectors of water-related diseases. Innovative technologies, including the improvement of indigenous technologies are needed to fully utilize limited water resources and to safeguard those resources against pollution. Agenda 21: Programme of Action for Sustainable Development, 1992.
Bernward Hölting, Wilhelm G. Coldewey

Part I


2. Theories and Basic Terminology

The varying use of hydrogeological and water management terms, particularly in older literature, makes it necessary to standardize these terms to ensure clear understanding. With regard to this, in Germany, they published the first edition of DIN 4049-1 in 1944 and is now in its fourth edition, published in three parts:
  • Hydrological basic terms with sections on, for example, metrology/models and statistics.
  • Hydrological terms relating to the characteristics of groundwater with sections on: general, physical, chemical, ecological and limnological terms as well as terms for sampling and evaluation.
  • Terms relating to quantitative hydrology with sections on Precipitation/Water Budget, Surface Waters and Subsurface Waters
Bernward Hölting, Wilhelm G. Coldewey

3. Voids in the Subsoil

Groundwater movement is only possible if there is some degree of continuity between voids in a rock or soil formation. The composition of the earth’s crust is quite heterogeneous which leads to the fact that the formed voids can vary greatly in terms of their nature and scale. For example, depending on the type of void, the German standard, DIN 4049-3, differentiates between pore, joint and karst groundwater. Accordingly, the voids in rocks where groundwater circulates can be subdivided as follows:
  • Pore voids,
  • Joint (interface) voids,
  • Karst voids,
  • Anthropogenic loosening due to building projects (such as tunnels and shafts).
Bernward Hölting, Wilhelm G. Coldewey

4. Geohydraulics

There must be an existing pressure gradient for water to be able to flow in the underground and this gradient determines the water’s velocity and direction of flow. The Reynolds number Re (Osborne Reynolds, British physicist and engineer, 1842–1912) is a dimensionless parameter that describes the behavior of water in pipes as well as in pores and joints. It also enables the identification of the transition from laminar to turbulent flow.
Bernward Hölting, Wilhelm G. Coldewey

5. Surface Water Infiltration

Infiltration is defined as the inflow of water through narrow voids in the lithosphere. Here, however, a distinction is made (according to DIN 4049-3) between infiltration processes from precipitation, from irrigation and flooding, as well as from surface waters. In these cases, “water” is a collective term for all types of water occurring in nature, including any dissolved, emulsified and suspended substances it may contain. Infiltration is an important part of the water cycle.
Bernward Hölting, Wilhelm G. Coldewey

6. Groundwater Dynamics

After the infiltration of the percolated fraction of rain water through the unsaturated soil zone, the water enters the saturated soil zone and thence the groundwater where it is subject to the hydraulic laws relating to strata and rock. Groundwater dynamics (i.e. movement) is exclusively governed by gravity. A distinction is made between two states of flow, namely steady-state and unsteady groundwater flow. With the former, the Darcy velocity within the time interval at the point of observation is the same, while with the latter, it changes (according to DIN 4044).
Bernward Hölting, Wilhelm G. Coldewey

7. Groundwater Morphology

In addition to knowledge of the regional geological composition, a detailed record of groundwater morphology is of great significance for hydrogeologists. This is because the shape of the groundwater level, and the level of the free or confined groundwater level, reflect the ongoing state of equilibrium in the geohydraulic dynamics of the area in question. Therefore, the definition of hydrogeological regimes and issues usually begins with the evaluation of the groundwater morphology. The following terms (as defined DIN 4049-3) are important for the description of groundwater morphology:
  • Groundwater level represents the upper boundary surface of a groundwater body.
  • Groundwater longitudinal section shows the section through a groundwater body normal to its lines of equal hydraulic head (The groundwater longitudinal section often corresponds to a good approximation of a vertical section along a flow-line of the groundwater level).
  • Hydraulic head (i.e. hydraulic pressure head) is the sum of the geodetic height and pressure head for a point in an observed groundwater body.
  • Total hydraulic head gradient is the gradient of the hydraulic/piezometric heads between two measuring points.
  • Piezometric surface describes the surface of all hydraulic heads of a groundwater level/surface from the geometric location of the endpoints (The general morphological designations can be used for the description of the piezometric surface, e.g. groundwater depression).
  • Groundwater equipotential lines (also known as groundwater contour lines) are lines of equal elevation of a piezometric surface.
  • Groundwater gradient consists of the gradients of the piezometric surface.
  • Groundwater flow lines represent an idealized movement path of groundwater particles in the potential field of a groundwater body (Groundwater flow lines are perpendicular to the potentiometric surface of a groundwater body).
  • Direction of groundwater current (also called direction of groundwater flow) takes place in the direction of the groundwater flow lines.
  • Potentiometric surface of a groundwater body is the geometric location of all points in the observed groundwater body with the same total hydraulic head (Applies only with negligible differences in density).
  • Equipotential line corresponds to the intersection line between the potentiometric surface of a groundwater body and the groundwater longitudinal section. It is an imaginary line at right angles to the groundwater flow line (Fig. 15.​10).
Bernward Hölting, Wilhelm G. Coldewey

8. Hydrological Cycle: Water Balance

Groundwater is only a part of the hydrological cycle, or water cycle, which (according to DIN 4049-1) is defined as a “constant sequence of state and location changes of water with the main components of precipitation, discharge and evaporation” (Fig. 8.1). Solar radiation supplies the required energy.
Bernward Hölting, Wilhelm G. Coldewey

9. Numerical Groundwater Models

Numerous questions in the field of hydrogeology (such as the effects of large abstractions in extensive heterogeneous aquifers, infiltration and discharge to nearby receiving waters) require detailed mathematical calculations. There was a move towards investigating these points using models because
  • it is not possible to take samples from the groundwater system,
  • the transferability of analytical calculations to large areas with different subareas cannot be ensured and
  • sampling the reaction of the natural systems can only be carried out slowly and so has significant time and financial consequences.
Bernward Hölting, Wilhelm G. Coldewey

10. Basic Physical and Chemical Factors

Water never exists in a chemically pure form in nature because it dissolves substances, transports them and then deposits some of them elsewhere. This leads not only to redistribution of substances in the groundwater conducting layers, but also to the formation of secondary rocks and possibly to the salinization of groundwater and soils. Here, the chemical composition of the water (and thus its quality) depends on its physical and physical-chemical properties. The understanding of such processes and of the respective water quality regimes enables conclusions to be drawn on the origin and the movement of the groundwater, the availability for industrial and domestic use, the environmental influences and options for the remediation of harmful impacts. On the other hand, the composition of some mineral and medicinal waters can give them therapeutic characteristics in health care.
Bernward Hölting, Wilhelm G. Coldewey

Groundwater Properties groundwater - properties

11. Basic Chemical and Physicochemical Principles

Legally approved units are defined for Europe as defined in the Directives of the EU Commission which are then implemented in the various national legislations. In Germany, for example, the parameters and units in chemistry were redefined in DIN 32625 wherein some of the formula symbols and/or their format have been changed. Aylward and Findlay (2002) and Küster and Thiel (2003) give a clear representation of the chemical units. Further information can be found in Domenico and Schwartz (1997) (Table 11.1).
Bernward Hölting, Wilhelm G. Coldewey

12. Physicochemical Processes in Groundwater Flow

The chemical property of groundwater depends on the infiltrated substances (mainly from anthropogenic sources) from the earth’s surface through percolating water, as well as on the chemical-petrographic properties of the water-conducting aquifer. During groundwater flow, there are interactions between the aquifer and groundwater bodies with different properties (Luckner and Schestakow 1986). One can assume that the property of the groundwater, i.e. the ion contents (quantitative and qualitative) given in a water analysis, is the result of various physicochemical processes towards a state of equilibrium. Such processes are sometimes called water “diagenesis” or “metamorphosis”. A groundwater analysis should be understood as an expression of this chemical-physical state of equilibrium and can be used through careful interpretation to recognize the processes occurring as a result of groundwater flow. However, because the petrographic properties of an aquifer in the subsoil are seldom homogenous, the states of equilibrium are constantly changing, all the more so with longer flow paths. For this reason, the results of chemical water analyses should only be assessed at selected points and the processes that took place regionally or temporally can only be deduced in comparison with other analytical results. This interpretation of chemical conditions in aquifers should not be performed statically but, rather, dynamically.
Bernward Hölting, Wilhelm G. Coldewey

13. Groundwater Biology

Although groundwater is characterized by an extreme range of living conditions, it also offers a habitat for a multitude of organisms such that groundwater is increasingly considered as an ecosystem. The extreme conditions include permanent darkness, spatial restriction, constant low temperatures and limited nutrients. In Germany, the joint project group “Groundwater Biology” of the DWA and DVGW compiled current knowledge on groundwater habitats in a detailed overview (VDG 2005).
Bernward Hölting, Wilhelm G. Coldewey

14. Groundwater Classifications

The evaluation and representation methods enable the classification of groundwater types, i.e. the classification of different types of groundwater according to their solutes and the grouping of geohydrochemically or genetically similar groundwater into units (or types). The goal is to investigate the geohydrochemical properties of groundwater generally, using a discrete statistical record of geohydrochemical data from a specific groundwater occurrence.
Bernward Hölting, Wilhelm G. Coldewey

Part III


15. Groundwater Exploitation

In terms of groundwater quality and management, the exploitation and utilization of groundwater as drinking water requires fundamental knowledge in various areas of expertise that are important requirements for the establishment and operation of waterworks. In Germany the DVGW textbook on water supply (DVGW 1996a) and the rules and standards for groundwater exploration (DVGW 1996b) provide comprehensive basic information. Also, the DVWK “Groundwater Utilization” Expert Committee compiled basic information for the determination of the available potential yield (DVWK 1982a).
Bernward Hölting, Wilhelm G. Coldewey

16. Geohydraulic Investigations

Various methods, both in the laboratory as well as in the field, can be used to determine geohydraulic parameters in unconsolidated rock and bedrock (Batu 1998; Hiscock 2005). The methods differ greatly in terms of not only their accuracy but also with respect to the time and costs involved. For this reason, it is important to make sure that the costs are consistent with the required accuracy.
Bernward Hölting, Wilhelm G. Coldewey

17. Water Exploitation

The type of technical facilities for water production, i.e. water exploitation plant (Fig. 17.1), depends on the existing geological and hydrogeological conditions (Fig. 15.​9) (Flinspach 1996) and so a distinction is made between the following scenarios:
  • Water exploitation from surface waters,
  • Water exploitation from rain water,
  • Catchments of springs, which also include (in the broad sense) percolation shafts and (mining) galleries,
  • Dug wells,
  • Drilled wells: usually bored vertically, but sometimes horizontally or diagonally.
Bernward Hölting, Wilhelm G. Coldewey

18. Building Activities in Groundwater

Groundwater is of great importance when building in unconsolidated rock and in bedrock, and knowledge of both the composition and discharge of the groundwater can be decisive in the implementation of a building project. Structures can lead to retention of the groundwater, but also can have a drawdown effect. In sticky unconsolidated rocks, the physical properties of the rock are often significantly altered by water in the rock pores and so groundwater has an effect on the bearing capacity, internal resistance and compressibility. In bedrock, the shear strength could be reduced by an increase of the pore water fraction in clayey rock layers on the joints. Hydrostatic pressure can lead to the upwelling of entire buildings or, even worse, individual parts of the building; this uplifting process can lead to significant structural damage. Furthermore, the chemical composition of the water and thus its effect on the building material, should also be taken into account because free carbonic acids, chlorides, sulfates and sulfides can corrode building materials. Therefore, in some cases, the composition of the building materials should be adapted to the groundwater quality; for example, the effect of sulfates can be inhibited by using sulfate-resistant cement in concrete. On the other hand, care should be taken that there are no negative impacts on groundwater quality due to the use of building materials.
Bernward Hölting, Wilhelm G. Coldewey

19. Drinking Water Protection German Experience

In times of intensive utilization of springs, groundwater and surface water, the protection of these resources is of increasing critical importance. This is true for both quantitative and qualitative aspects and so numerous laws and ordinances are invariably implemented to protect this vital commodity for all of mankind. With regard to this, while a considerable proportion of the texts in Sects. 19.1 and 19.2 are directly linked to German legislation and policies, the essential principles discussed and the advice given in those sections are likely to be highly relevant to most developed/developing countries.
Bernward Hölting, Wilhelm G. Coldewey


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