Groundwater issues have generated worldwide concern in recent decades. The problems are numerous: too little groundwater, too much groundwater, groundwater contaminated by either saline water or a broad spectrum of industrial and domestic pollutants. Many urban groundwater problems are not unique to any one region, which is the thinking behind this book. Many of the case studies presented here have never before been described in English. Overall, the papers represent the work and experience of researchers and groundwater professionals who have worked on urban groundwater issues in developed and less-developed nations around the world. They reveal the magnitude and scope of the problem as well as identify future challenges, potential courses of action, and emerging technologies that offer hope for the future.

During the past three decades, urban groundwater has emerged as one of the worlds most pressing issues. Explosive population growth, most prevalent in cities, has placed an inordinate demand on groundwater supply, prompting concerns for its long-term sustainability at a time when the quality of available groundwater resources is being increasingly

It is well known that 55% of the world’s population currently lives in urban areas, and this figure is predicted to grow to 68% by 2050, adding more than 2.5 billion people to urban populations. It is also projected that there will be 43 megacities worldwide by 2030, with populations of more than 10 million inhabitants. The United Nations World Water Development Report, 2018, warned that by 2030, the global demand for fresh water is likely to exceed supply by 40%. Added to population growth, climate change has the potential to lead to changes in rainfall regimes, with the potential of increased flooding and drought. Currently, 1.2 billion people are at risk from flooding, but this is predicted to increase to about 1.6 billion, i.e., nearly 20% of the total world population, by 2050. In line with this, replacing deteriorating water management infrastructure that can no longer cope is economically unfeasible, impracticable from a construction point of view, and likely to fail in the long term. To address these issues, approaches are needed that are flexible and have multiple benefits. In its World Water Development Report, 2018, the UN promotes the use of nature-based solutions to some of these problems, with the focus of Sustainable Development Goal 6 (making sure that everyone has access to a safe and affordable supply of potable water and sanitation by 2030) requiring investment in suitable infrastructure across the world. This Special Issue covers the challenges faced in managing urban water in all its forms, from potable supplies to reuse and harvesting, as well as resilient and sustainable approaches developed to address flooding and drought.

Water resources, both in terms of water quality and water quantity, are of critical importance in planning for sustainable development in Central Asia and the Caucasus, as well as in other parts of the world. This NATO Advanced Research Workshop (ARW), entitled "Risk Assessment as a Tool for Water Resources Decision-Making in Central Asia", was conducted on September 23-25, 2002 in Almaty, Kazakhstan. The ARW addressed methods and approaches by which risk assessment methodology that has been developed in the United States, Europe and elsewhere can be applied to environmental and water resource problems in Central Asia. The stated goals of the ARWwere: • to assess the existing state of knowledge in the context of potential applications of risk assessment tools to water resources and other environmental issues in Central Asia; • to identify research gaps and directions for future research in the area of water resources which may be addressed through the application of risk assessment tools; • to promote closer working relationships between the scientists and technical experts from Central Asia and the Caucasus, as well as the scientists and technical experts from the United States and Europe. Based on historical experiences of Central Asian scientists and their colleagues in other parts of the world, there is a demonstrated need in the region to provide education, training and technical assistance on environmental decision-making tools, including risk assessment.

The forty papers in this book explore the state of sustainable groundwater management in a wide range of countries and cultures, climates, and geologies. They are organized in topic areas covering flow, chemical water quality, biological water quality, remediation, engineering, and socio-economics. An introductory section presents a range of integrated regional-scale studies. This volume will interest groundwater specialists in industry and research, and will provide insight for other urban specialists, including planners.

This text is written by a number of authors from different countries and disciplines, affording the reader an invaluable and unbiased perspective on the subject of intensive groundwater development. Based on information gathered from the experience of many countries over the last decades, the text aims to present a clear discussion on the conventional hydrogeological aspects of intensive groundwater use, along with the ecological, legal, institutional, economic and social challenges. Divided into two main sections, the first group of authors put forward the positive and negative aspects of intensive groundwater use, whilst a second group provide an overview of the situation specific countries face as a consequence of this phenomenon. Fully revised and up-to-date, Groundwater Intensive Use makes a significant number of discoveries in a subject area that is topical in today's climate.