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InhaltsangabePreface Abbreviations and dimensions Definitions 1 Introduction 2 The water cycle 2.1 Distribution of water on earth 2.2 The continental water cycle 2.2.1 The components of the Water Cycle 2.2.1.1 Characteristics of different climate zones 2.3 The vadose zone and its water balance for different climate zones 2.4 Rechargeable and fossil groundwater and water exploitation 2.5 The place of recharge in the water cycle 3 Mechanisms and processes of recharge 3.1 The input: precipitation and snowmelt 3.2 Wet and dry deposition at the interface atmosphere/lithosphere/biosphere 3.3 Overland-flow and infiltration 3.4 Matrix-flow and preferential-flow 3.5 Inter-flow 3.6 River-infiltration 3.7 Artificial recharge 3.8 Water vapor-fluxes in the subsurface 4 Research tools and methods in the study of recharge 4.1 Water balance estimates 4.1.1 Estimate of evapo-transpiration 4.1.2 Hydrograph analysis 4.1.3 Groundwater level fluctuations 4.2 Lysimeter studies 4.3 Hydraulic methods in the vadose zone 4.4 Isotope and chemical tracers 4.4.1 Stable and radioactive environmental isotopes 4.4.1.1 Preparation techniques 4.4.1.2 Measuring techniques 4.4.2 Environmental tracers for recharge determination 4.4.2.1 Environmental chloride 4.4.2.2 Environmental tritium 4.4.2.3 Environmental 2H and 18O 4.4.3 Artificial tracers 4.4.4 Application of tracers 4.5 Water sampling and sample conservation 4.6 Comparison between tracers and conventional techniques 5 Recharge under different climate regimes 5.1 Humid climates 5.1.1 Conceptual models 5.1.2 Water balance and separation of discharge components 5.2 Semi-arid climates 5.3 Arid climates 5.4 Cold climates 6 Man's impact on the groundwater recharge 6.1 Land use change: Agriculture 6.2 Land use change: Urban areas 6.3 Global changes and the water cycle 7 Literature survey Subject index

Groundwater constitute the most important reservoir of available clean water. Due to its overexploitation, some anthropogenic mismanagement on the surface and the overloading of the cleanup potential of subsurface, many of the groundwater systems used for water supply are in jeopardy. The problem is very severe in dry-lands, but also in urban, industrial, agricultural and traffic areas. This book first discusses the recharge fluxes relating both to the quantity and quality of groundwater. In order to face the threats to the water supply and to be able to maintain a sustainable water management policy, detailed knowledge is needed in between others on the surface to subsurface transformation link in the water cycle. Secondly, the presentation and comparison of both the traditional and modern approach to determine groundwater recharge is discussed. The traditional approach to determine groundwater recharge, is based on water balance estimates and hydraulic considerations, which yield instantaneous values at best but do not integrate the totality of recharge pathways in time and space. In contrast, environmental tracers do integrate these factors. Finally, the fate of groundwater recharge in the subsurface by hydraulic and geologic means is discussed in detail, in order to stimulate adapted groundwater management strategies and to better assess consequences of climate changes on groundwater resources as a whole. Audience This book will be of interest to hydrologists, hydro-geologists, engineers, geographers, agronomists, soil scientists, groundwater modellers, environmental physicists, limnologists