Preface
Groundwater ranks among the world’s most important natural resources. Apart from being a major source to meet human water demands for domestic, agricultural and industrial purposes, it provides a range of other services, such as supporting groundwater-dependent ecosystems, regulating (often buffering) a variety of natural processes and carrying geothermal energy. Making optimal use of these services and pursuing their sustainability requires sound hydrogeological knowledge: not only generic knowledge (necessary to understand the scientific rules governing groundwater-related processes) but also area-specific knowledge on the occurrence and properties of the invisible groundwater resources and their physical environment.
Acquiring and enhancing area-specific knowledge on groundwater and its setting belong to the core tasks of hydrogeologists. In this context, the aquifer concept has proven to be a powerful tool for integrating individual pieces of information about groundwater into a comprehensive spatial conceptual model and for sharing the acquired knowledge. Countless aquifers – ranging from small to very large – are scattered around the globe, many of them clustered in aquifer systems. The more important aquifers and aquifer systems usually carry a name, for easy identification.
This book is an introduction to the world’s large aquifer systems. It focuses on thirty-seven so-called mega aquifer systems and presents a macroscopic picture of their state and relevance based on attributes such as spatial dimensions, geology, groundwater reserves, groundwater renewal, mineral content, groundwater withdrawal and storage depletion. This information is of little use for practical purposes at the field level, given its aggregated nature and the lack of spatial detail. However, the book intends to serve other purposes and interests, linked to other spatial scales. It informs the reader about the existence and geographical distribution of a set of very large aquifers that – although limited in number – together represent more than half of the world’s groundwater reserves and constitute the source of approximately 40 percent of the global groundwater withdrawal. It reveals the huge differences in opportunities and challenges among these aquifer systems, resulting from differences in natural conditions (climate, geology, topography, hydrology, – including those prevailing in the remote past) and in interactions with people (groundwater withdrawal, pollution, mining, water management). Acquired knowledge of these mega aquifer systems may also contribute to a better understanding of the role of groundwater in various global processes, and to putting local groundwater issues into a wider geographic perspective.
Most information in this book is presented in the form of simple indicators and succinct explanatory text. For learning more about individual mega aquifer systems, however, many publications are available, the fruit of meticulous efforts by numerous scientists.