Groundwater Modelling in Arid and Semi-Arid Areas

Preface

Arid and semi-arid regions present special challenges for water management. They are, by definition, areas where water is at its most scarce, and face great pressures to deliver and manage freshwater resources. Demand for water has increased dramatically, due to population growth, increasing expectations for domestic water use, and expansion of industrial and agricultural activities. Available water resources have been reduced by pollution and over-abstraction. Many of the world’s arid regions are further threatened by climate change.

In addition, the science base to support water management remains limited. Hydrological processes can be very different from those of humid regions, precipitation and flow exhibit extreme variability in space and time, and data are often restricted in spatial coverage, record length and data quality.

UNESCO has identified, within the International Hydrological Programme, a special need to exchange knowledge on scientific aspects of water resources (with respect to both quantity and quality) in arid and semi-arid lands, and is supporting a number of regional centres to promote exchange of information and dissemination of good practice. At the global level, UNESCO
has initiated G-WADI, a Global network for Water and Development Information for arid lands. Information on G-WADI products and a news-watch service can be found on the G-WADI website (www.gwadi.org). G-WADI aims to facilitate the global dissemination of state-of-the-art scientific knowledge and management tools, and to facilitate the sharing of scientific and technical knowledge and management experience of new and traditional technologies to conserve water.

With the support of UNESCO and the UK Government, the first major G-WADI event was held in Roorkee, India, in March 2005, focusing on the surface-water modelling tools required to
support water management in arid and semi-arid areas. The strategy was to bring together the world’s leading experts to provide lectures and tutorials on this topic. This resulted in a book in the International Hydrology Series, Hydrological Modelling in Arid and Semi-Arid Areas, published by Cambridge University Press in late 2007.

Groundwater is commonly the most important water resource in arid areas, but is particularly difficult to quantify in terms of sustainability, and almost universally suffers from problems of over-abstraction, declining water tables and degradation of water quality. Hence, a second event was held in Lanzhou, China, in 2007, focusing on groundwater modelling in arid and semi-arid areas, and attended by 56 participants from 22 countries. The aims of the workshop were:
1. to bring together the world’s leading experts in arid zone groundwater modelling to deliver a definitive set of lectures and case studies to an audience of active researchers from the world’s arid regions; 2. to draw on the experience of the workshop participants in developing this material and to consider recommendations for future activities; 3. to make this material available to the global community through UNESCO and in particular the G-WADI website (www.gwadi.org);
4. to stimulate follow-up activities, regionally and globally. The material from this workshop provides the content of this book. It brings together state-of-the-art information on groundwater data, modelling and management, specifically focused on the challenges of arid and semi-arid areas, and we can say with confidence that the authors represent some of the world’s most distinguished authorities

The structure of the book is as follows: 

Chapter 1 describes the context for groundwater management in arid and semi-arid areas, including historical development and current pressures, and the associated needs for modelling, and
provides a summary of the book content and structure. Chapter 2 provides a review of some of the special hydrological features of arid areas, with a particular focus on groundwater recharge processes, and examples from the Arabian peninsula. Chapter 3 introduces isotopic and geochemical methods as important sources of information and insight into groundwater systems, with case studies from Africa and the Mediterranean. 

Chapter 4 provides an ix
overview of groundwater modelling, including the treatment of spatial variability, calibration and uncertainty, and Chapter 5 illustrates the application of geostatistics to an Indian case study. Groundwater source protection is discussed in Chapter 6, and Chapter 7 provides a comprehensive discussion of the problems of density-dependent groundwater flows associated with salinity effects. Finally, Chapter 8 addresses sustainable water management in arid and semi-arid regions, with case studies from North Africa, Southern Africa and China.

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Groundwater Modelling in Arid and Semi-Arid Areas