Editors' foreword.

Water has been a considerable source of power throughout human civilization. Watercourses have served as natural boundaries between states, routes for trade and commerce, and as a necessary component in health, cultural and religious practices of peoples around the world. Over time, human population growth and economic expansion have placed enormous demands on the planet's freshwater resources. As a result, water has long been a source of hostility and conflict between neighboring communities and across borders. From the Tigris-Euphrates River basin to the American Southwest to the deserts of Sudan, water has been a driver of tension between its users. The insertion of global climate change into this equation threatens to make water resources less secure and the potential for conflict even greater.

At present, an estimated 1.1 billion people lack access to safe drinking water. Each year, over 3 billion people suffer from water-related diseases. Understanding the compounding global challenges of climate change, population growth and the increasing demand for water has never been more urgent. This is reflected in the language of politicians and businesspeople, the media and international institutions. For instance, in 2002, the United Nations amended the Millennium Development Goals to include drinking water and sanitation targets. The United Nations has also branded the years 2005-2015 as the "International Decade for Water Action" and 2008 as the "International Year of Sanitation." At the 2008 World Economic Forum in Davos, water was featured prominently in the discussions between corporate and government leaders, with particular corporations pledging to become net-zero water users in the near future.

The Journal of International Affairs uses its single-topic format to analyze water from a variety of angles. "Water: A Global Challenge" examines water in remote indigenous communities and cosmopolitan megacities, as a right and as a commodity, in sustaining ecosystems and our modern lifestyles, as a source of disease and life, and in promoting conflict and cooperation. Such an endeavor is accomplished through the works of a diverse set of scholars and practitioners experienced in water's global implications.

In this issue's capstone essay, Upmanu Lall, Tanya Heikkila, Casey Brown and Tobias Siegfried identify three distinct water crises that have vet to be systematically connected by scholars: access, pollution and scarcity. By looking at how...