Philippe QUEVAUVILLER is a member of the Water & Marine Unit of the EC Environment Directorate-General where he is responsible for the development and implementation of a new Groundwater Directive which will complement the existing water policy framework. He has worked as a researcher in marine geochemistry for over 20 years during which he has published more than 200 papers in the international literature and several books linked to environmental quality measurements. He is also a part-time professor at the K.U. Leuven teaching “water quality and treatment”.

Groundwater Science and Policy

An International Overview

By Philippe Quevauviller

The Royal Society of Chemistry

Copyright © 2008 The Royal Society of Chemistry
All rights reserved.
ISBN: 978-0-85404-294-4

Contents

List of Contributors, xxxiii,
1. General Introduction,
Chapter 1 General Introduction: The Need to Protect Groundwater Philippe Quevauviller,
2. Science–Policy Integration Needs,
Chapter 2.1 Science–Policy Integration for Common Approaches Linked to Groundwater Management in Europe Philippe Quevauviller,
Chapter 2.2 Transferring Scientific Knowledge to Societal Use: Clue from the AQUATERRA Integrated Project Philippe Négrel, Dominique Darmendrail and Adriaan Slob,
Chapter 2.3 Groundwater Management and Planning: How Can Economics Help? Jean-Daniel Rinaudo and Pierre Strosser,
3. Groundwater Regulatory Framework,
Chapter 3.1 European Union Groundwater Policy Philippe Quevauviller,
Chapter 3.2 US Drinking Water Regulation: The Ground Water Rule Crystal Rodgers-Jenkins,
4. Stakeholder Interactions,
Chapter 4.1 Principles of the Common Implementation Strategy of the WFD: The Groundwater Woking Group Philippe Quevauviller, Johannes Grath and Andreas Scheidleder,
Chapter 4.2 The Pilot River Basin Network: Examples of Groundwater-related Activities Lorenzo Galbiati and Giovanni Bidoglio,
Chapter 4.3 The Harmoni-CA Initiative Geo E. Arnold, Wim J. de Lange and Michiel W. Blind,
Chapter 4.4 Linking Public Participation to Adaptive Management Claudia Pahl-Wostl, Jens Newig and Dagmar Ridder,
5. Groundwater Characterization and Risk Assessment,
Chapter 5.1 Groundwater Characterization and Risk Assessment in the Context of the EU Water Framework Directive Andreas Scheidleder, Johannes Grath and Philippe Quevauviller,
Chapter 5.2 Groundwater Quality Background Levels Emilio Custodio and Marisol Manzano,
Chapter 5.3 Groundwater Age and Quality Klaus Hinsby, Roland Purtschert and W. Mike Edmunds,
Chapter 5.4 Characterisation of Groundwater Contamination and Natural Attenuation Potential at Multiple Scales Thomas Ptak and Jerker Jarsjö,
Chapter 5.5 Improved Risk Assessment of Contaminant Spreading in Fractured Underground Reservoirs Christos D. Tsakiroglou,
Chapter 5.6 Groundwater Risk Assessment at Contaminated Sites (GRACOS): Test Methods and Modelling Approaches Peter Grathwohl and Hans van der Sloot,
Chapter 5.7 INCORE: Integrated Concept for Groundwater Remediation Thomas Ertel and Hermann J. Kirchholtes,
6. Groundwater Monitoring,
Chapter 6.1 Groundwater Monitoring in the Policy Context Johannes Grath, Rob Ward and Andreas Scheidleder,
Chapter 6.2 Screening Methods for Groundwater Monitoring Catherine Gonzalez, Anne-Marie Fouillac and Richard Greenwood,
Chapter 6.3 Quality Assurance for Groundwater Monitoring Philippe Quevauviller and Stéphane Roy,
7. Groundwater Pollution Prevention and Remediation,
Chapter 7.1 Prevention and Reduction of Groundwater Pollution at Contaminated Megasites: Integrated Management Strategy and its Application on Megasite Cases Jeroen Ter Meer, Hans Van Duijne, Rob Nieuwenhuis and Huub Rijnaarts,
Chapter 7.2 Forecasting Natural Attenuation as a Risk-based Groundwater Remediation Strategy Ryan D. Wilson, Steven F. Thornton and David N. Lerner,
Chapter 7.3 Diffuse Groundwater Quality Impacts from Agricultural Land-use: Management and Policy Implications of Scientific Realities Stephen Foster and Lucila Candela,
8. Integrated River Basin Management,
Chapter 8.1 Integrated Management Principles for Groundwater in the WFD Context Philippe Quevauviller,
Chapter 8.2 System Approach to Environmentally Acceptable Farming Ramon Laplana and Nadine Turpin,
Chapter 8.3 WATCH. Water Catchment Areas: Tools for Management and Control of Hazardous Compounds Thomas Track, Steve Setford, Sharon Huntley, Claudine Vermot-Desroches, John Wijdenes, Damia Barceló, Monica, Rosell Linares, Peter Werner, Jens Fahl, Hans-Peter Rohns, Claudia Forner, Jesper Holm, Douglas Graham, Eckard Hitsch and Josef Lintschinger,
9. Groundwater Status Assessment,
Chapter 9.1 Methodology for the Establishment of Groundwater Environmental Quality Standards Dietmar Müller and Anne-Marie Fouillac,
Chapter 9.2 Pesticides in European Groundwaters: Biogeochemical Processes, Contamination Status and Results from a Case Study Christophe Mouvet,
Chapter 9.3 Evaluation of the Quantitative Status of Groundwater-Surface Water Interaction at a National Scale Hans Jørgen Henriksen, Lars Troldborg, Per Nyegaard, Anker L. Højberg, Torben O. Sonnenborg and Jens Christian Refsgaard,
10. Modelling,
Chapter 10.1 Conceptual Models in River Basin Management Antony Chapman, Jos Brils, Erik Ansink, Cécile Herivaux and Pierre Strosser,
Chapter 10.2 Modelling Reactive Transport of Diffuse Contaminants: Identifying the Groundwater Contribution to Surface Water QualityHans Peter Broers, Bas van der Grift, Jasper Griffioen and Ruth Heerdink,
Chapter 11.1 SNOWMAN: An Alternative for Transnational Research Funding Jörg Frauenstein and H. Johan Van Veen,
Chapter 11.2 Incorporation of Groundwater Ecology in Environmental Policy Dan L. Danielopol, Christian Griebler, Amara Gunatilaka, Hans Jürgen Hahn, Janine Gibert, F. Mermillod-Blondin, Giuseppe Messana, Jos Notenboom and Boris Sket,
Chapter 11.3 Towards a Science-Policy Interface (WISE-RTD) in Support of Groundwater Management Philippe Quevauviller,
Appendices,
Subject Index, 716,

CHAPTER 1

General Introduction: The Need to Protect Groundwater

PHILIPPE QUEVAUVILLER

European Commission, DG Environment (BU9 3/142), Rue de la Loi 200, BE-1049 Brussels, Belgium

1.1 Introduction

Groundwater constitutes the largest reservoir of freshwater in the world, accounting for over 97% of all freshwater available on earth (excluding glaciers and ice caps). The remaining 3% is composed mainly of surface water (lakes, rivers, wetlands) and soil moisture. Until recently, focus on groundwater mainly concerned its use as drinking water (e.g. about 75% of European Union (EU) inhabitants depend on groundwater for their water supply). Groundwater is also an important resource for industry (e.g. cooling waters) and agriculture (irrigation). It has, however, become increasingly obvious that groundwater should not only be viewed as a drinking water reservoir, but also as a critical aquatic ecosystem. In this respect, groundwater represents an important link of the hydrological cycle for the maintenance of wetlands and river flows, acting as a buffer through dry periods. In other words, it provides the base flow (i.e. the water which feeds rivers all year round) for surface water systems, many of which are used for water supply and recreation. In many rivers, indeed, more than 50% of the annual flow is derived from groundwater. In low-flow periods in summer, more than 90% of the flow in some rivers may come from groundwater. Hence, deterioration of groundwater quality may directly affect other related aquatic and terrestrial ecosystems.

Since groundwater moves slowly through the subsurface, the impact of anthropogenic activities may last for a relatively long time, which means that pollution that occurred some decades ago — whether from agriculture, industry or other human activities — may still be threatening groundwater quality today and, in some cases, will continue to do so for several generations to come. The legacy of the past is clearly visible at large-scale contaminated sites, e.g. industrial sites or harbour areas, where it is simply not possible, with state-of-the-art technology and a proportionate use of public and/or private money, to clean up the regional contamination encountered at these locations. In addition, the experience of remediation of the past 20 years has shown that the measures taken have in most cases not been able to completely remove all contaminants and that pollutant sources, even if partially removed, continue to emit for long periods of time (i.e. several generations). Therefore, an important focus should be on preventing pollution in the first place.

Secondly, since surface water systems receive a continuous discharge of inflowing groundwater, a deteriorated groundwater quality will ultimately be reflected in the quality of surface waters. In other words, the effect of human activity on groundwater quality will eventually also impact on the quality of associated aquatic ecosystems and directly dependent terrestrial ecosystems if so-called natural attenuation reactions such as biodegradation in the subsurface are not sufficient to contain the contaminants.

Finally, groundwater is a “hidden resource” which is quantitatively much more significant than surface water and for which pollution prevention and quality monitoring and restoration are even more difficult than for surface waters, which is mostly due to its inaccessibility. This “hidden” character makes it difficult adequately to locate and quantitatively appreciate pollution impacts, resulting in a lack of awareness and/or evidence regarding the extent of risks and pressures. Recent reports, however, show that pollution from domestic, agricultural and industrial sources is, despite the progress in some fields, still a major concern, either directly through discharges (effluents) or indirectly from the spreading of nitrogen fertilisers and pesticides or through leaching from old landfills or industrial sites (e.g. chlorinated hydrocarbons, heavy metals). For example, around one-third of ground-water bodies in Europe currently exceed the nitrate guideline values. While point sources have caused most of the pollution identified to date, there is evidence that diffuse sources are having an increasing impact on ground-water.

This chapter develops the elements discussed above as a general introduction to this book, which further elaborates issues related to groundwater policy, protection and remediation throughout the different chapters.

1.2 The Scientific Background

1.2.1 The Hydrogeological Cycle

It is estimated that roughly 22% of freshwater is stored underground, representing some 8 million km3 of 37 million km3 of freshwater found on the planet. Excluding water from polar ice, groundwater constitutes some 97% of all the freshwater that is potentially available for human use on or beneath the earth’s surface. The remainder is stored in lakes, rivers and swamps. Groundwater recharge is essentially ensured by rain that infiltrates through the soil into underlying layers; this recharge is occasionally augmented by streams and rivers that lose water to underground strata. Once underground, groundwater flows at rates which range from more than 10 metres per day to as little as 1 metre per year until it reaches an outlet, e.g. a spring or seepages at the ground surface (which actually keep rivers flowing during dry periods).

The time scales at which groundwater flows hence considerably vary, depending on hydrogeological conditions. It may take years to decades for water to move through the soil to reach the water table, the level at which the ground is fully saturated, where it may remain underground for tens or even thousands of years before reappearing at the surface. Geological settings may also trap groundwater from both its source and its outlets. Finally, climate change may also lead to groundwater losses by depriving aquifers from recharge as it appears in a number of regions which turned into deserts.

The level of available geological and hydrogeological information varies from area to area, and this has an effect on the protection schemes to be developed. Where the information is adequate, a comprehensive scheme, based on hydrogeological concepts, is achievable. However, as mentioned below, aquifers are rarely homogeneous and their geological variability conditions the nature of groundwater flowing through their respective lithologies and structures, which makes it difficult to establish large-scale conceptual hydro-geological models.

1.2.2 Waters in Aquifers

The nature of aquifers, consisting either of unconsolidated materials such as sand or gravel or consolidated rock such as sandstone, has a considerable influence on groundwater flows and hence on pollution pathways (see Section 1.4.3). On the one hand, unconsolidated materials, such as sands, can store up to 30% of their volume as water. On the other hand, consolidated materials may also store large volumes of water, depending upon their porosity, but groundwater flow is usually very slow owing to the small size of the pores. In some types of rocks, the capillary attraction between the ground-water and the pore surface does not allow water to be released and hence to flow. However, consolidated materials may also store water in fractures in the rock, which although they usually represent less than 1% of the total volume can be enlarged by dissolution in rocks such as limestones. Enlarged fractures enable the aquifer both to store large volumes of water and permit high groundwater flows, which has an impact on pollution spreading (see Chapter 5.5).

Aquifers are usually bounded above by an unsaturared zone, which contains both air and water, and below by an impermeable bed constituted, for example, of clay or rock. The boundary between the unsaturared and saturated zones (water table) is found at different depths depending on the hydrogeological and climatic settings, e.g. as much as 100 m below the surface in arid areas and close to the surface in humid areas. Some aquifers are, however, bounded entirely by impermeable layers and contain groundwater under pressure (which enables water abstraction by artesian wells).

1.2.3 Groundwater Flows

With aquifer characteristics in mind (in particular the type of materials containing the water), it is possible to better approximate groundwater flows. Ground-water moves through aquifers as a result of differences in pressure or elevation of the water table within the aquifer. The groundwater flow may be slowed down by various obstructions while moving from the point of recharge to its exit from the aquifer. In some cases, impermeable rock formations (known as aquicludes) such as shale stop completely the water flow, while other geological strata (known as aquitards), such as clay lenses embedded with sand, may slow down the groundwater flow.

The groundwater flow rate depends on the permeability and porosity of the aquifer, and on the pressure gradient. As an example, highly permeable aquifers such as limestones respond rapidly to changes in recharge and abstraction rates, and groundwater levels in such areas may fluctuate by as much as 10 m a year and may change by up to 50 m a year.

The greatest variations in groundwater flow patterns occur where changes in rock types, e.g. limestone overlying sediments and a hard crystalline rock, induce discontinuities in flow and may bring groundwater flow to the surface on the junction between the two rock types. Variations in groundwater flow may also occur within an unconsolidated alluvial aquifer, e.g. great lateral variations occur in the mix of gravel, sand and clay making up the aquifer matrix. In larger-scale alluvial aquifers, layers of sand or gravel-rich sediment interbedded with clay-rich layers induce lateral flow following the more permeable sand- and gravel-rich zones.

Needless to say that groundwater flow rates are very small in comparison to those of surface water. In this respect, some groundwater from deep alluvial basins is likely to be thousands or even hundreds of thousands of years old. The slow movement of groundwater largely contributes to its purity since contaminants become highly attenuated during the usually long groundwater flowing pathway to the surface. Groundwater may also become enriched with elements that are naturally present in rocks. Furthermore, saltwater intrusion may occur near coastlines, in particular where the water table is lowered due to abstraction, and this is likely to be accentuated by rising sea levels due to climate change.

1.2.4 Groundwater Quality

Most groundwater originates from water that has permeated first the soil and then the rock below it. The soil removes many impurities and the rock through which the water then flows, perhaps for thousand of years, filters and purifies the water even further. It therefore usually reappears at the earth surface free of pathogenic micro-organisms. This is the reason for an increasing exploitation of groundwater resources (see Section 3.1).

While groundwater is generally less easily/rapidly polluted than streams and rivers, it often contains high concentrations of dissolved elements from the rock through which it has passed. Another feature is that when groundwater is polluted, many processes occur during its pathway to the surface; in particular, pollutant loads may be attenuated by adsorption by the rock itself or biochemical transformation into substances that are less harmful than the original compounds. However, severe pollutions may affect groundwater quality over long periods, i.e. once pollutants reach the water table, it may take a very long time before they are flushed out from the aquifer. Furthermore, groundwater quality affected by pollution may take a long time to recover since the water within the aquifer moves so slowly. Once polluted, aquifers are difficult — and sometimes even impossible — to clean up. The process can be likened to trying to squeeze out the last traces of soap from a sponge.

As stressed above, the complex nature of groundwater is compounded in the context of pollution and quality problems. Let us repeat that the chemical characteristics of aquifer materials and the way pollutants react with them vary greatly. In some cases, pollutants are “filtered” out mechanically or through adsorption onto particles within the soil or aquifer matrix. In other cases, however, pollutants remain mobile and can rapidly spread throughout an aquifer. The aquifer matrix itself can become contaminated and pockets of pollutants can serve as continuous sources of contamination. For example, small pockets of organic solvents can remain as pollution sources virtually indefinitely because of their low solubility in water. Furthermore, changes in pH or other groundwater characteristics can cause the release of toxic materials, such as fluoride, from natural sources within aquifers. Given the hundreds of thousands of naturally occurring compounds in groundwater and aquifer materials, and the similarly large number of compounds present in waste water released to aquifers, understanding and managing pollution problems is a highly complex task. This illustrates the importance of preventing pollution of groundwater from the start rather than dealing with the consequences (Chapter 5.5).

All the above considerations have an impact on the way groundwater background levels are evaluated and also on the assessment of groundwater quality either related to its use or to its environmental value. These aspects are discussed in various chapters of this book (Chapters 5.1–5.3 and 9.1).

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