Since the Earth Summit in Rio de Janeiro in 1992 it has become obvious that there can be no global sustainable development without sustainable settlement. However, today the issue of urban environmental sustainability is becoming critical because urbanization and its associated environmental impacts are occurring at an unprecedented rate. The fast expanding large cities raise many problems for water resources management. Water for cities is a topic of paramount importance for the sustainability of urban areas, as well as for water resources, whether groundwater, lakes, reservoirs or rivers.

Adequate water supply and drainage management are urgent tasks, and new solutions are needed to overcome the problems of water scarcity, deteriorating water quality, lack of sufficient supply systems, inappropriate handling of wastewater, inadequate storm water management, flood risk, etc. However, the context in which water management activities are planned and carried out in the developing and developed world are changing and the world is very different today to how it was, say, ten years ago. Water service providers in the developed world are facing key issues across several fronts:

– more stringent regulatory requirements,

– increased consumer expectations,

– increased economic pressures to improve operating efficiency,

– a trend to privatize water services, and

– the requirement of higher security of supply.

However, the sustainability aspects of water management in developing countries are often quite different from those in the developed world and have been badly neglected over the past years. For example, management of water supply and sanitation systems is often poor, resulting in interruptions in the provision of services and sometimes in the complete collapse of systems and the contamination of water supply sources. Normally, the operation and maintenance of water supply and sanitation facilities, which represent a major requirement for sustainable services, are regarded as low profile areas, whilst the construction of new facilities has historically been given the highest priority.

Given the requirements for sustainability and integrated water management, the relationships between large cities and their surrounding areas have to be reconsidered. The 39 papers presented at the Symposium on Sustainable Water Management Solutions for Large Cities (organized by the International Commission on Water Resources Systems, ICWRS) at the VIIth IAHS Scientific Assembly, held in Foz do Iguaçu (Brazil), April 2005, address the complex problems of water management for large cities with an interdisciplinary outlook, taking into account their hydrological, technical, environmental, as well as socio-economic aspects. The papers help develop an understanding of the hydrological principles fundamental to the solution of management problems in surface waters, groundwater and public supplies in an international context. They evaluate the influence of human activity on hydrological processes,

provision of water supply and sanitation services, and include alternative styles of water management. The papers are organized in four broad topics:

– Integrated water resource management

– Sustainability and socio-economic and eco-environmental issues

– Urban drainage/flooding and wastewater management, and

– Water quality monitoring and management

We hope that the symposium and the book have defined the challenges for hydrology and water management caused by the long-lasting trend to form extended urbanized areas, and that they will serve to promote the exchange of existing experiences of water management for, in and around large cities.

We wish to thank all the participants of the Symposium for their role in supporting this event and contributing to this volume. Without their contributions this book could not have been completed. We also recognize the diligent efforts of the IAHS Secretariat and the steady encouragement and wise counsel of Dr Cate Gardner of the IAHS Press and Dr Pierre Hubert, IAHS Secretary General.