Central Asia is a huge landmass situated between the world's largest inland water body, the Caspian Sea, and the mountain ranges of the Tian Shan, Pamirs and the Hindukush. For centuries, caravans travelled along the famed Silk Road-actually there were many-to connect the civilizations of Europe and Asia, crossing deserts, grassy steppes and mountain ranges. Powerful Khans built cities and centres of Islamic scholarship and developed sophisticated irrigation systems to compensate for the region's low rainfall. These systems focused primarily on the two main rivers that carry the snowmelt of the Central Asian mountain ranges west to the Aral Sea: the Amu Darya (darya means river in Persian), which was known by the ancient Greeks as the Oxus, and the Syr Darya (the Jaxartes, or Pearl River, to the Greeks). Before 1991 and the break-up of the Soviet Union, both rivers ran mostly inside the USSR, along with a small part of Afghanistan. Today, sharing the water has become much more complicated because the rivers cross the territory of six independent states: Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan, along with Afghanistan.

Water is unevenly distributed in Central Asia. Most of the renewable surface water is formed in the mountain regions of Tajikistan, Kyrgyzstan and Afghanistan, while most of it is used in the downstream countries of Kazakhstan, Turkmenistan and Uzbekistan. Starting in the 1960s, the Soviet authorities began a massive irrigation expansion that drew water from both rivers to increase cotton production. The result was that much less water reached the Aral Sea, then the world's fourth-largest inland lake, than was required to compensate for evaporation. The sea is now a tenth of its size half a century ago.

With the disintegration of the Soviet Union, the five newly independent states faced the challenge of cooperating with each other and with Afghanistan to determine how to share the water and also how to address the Aral Sea desiccation.

They had to learn how to do this against a backdrop of growing populations, institutional upheavals and climate change. Global warming has already caused glaciers feeding both rivers to melt, temporarily increasing flow but promising long-term decreases. At the same time, warmer temperatures will mean increasing losses due to evaporation, both in irrigation and in the reservoirs.

Given these challenges, in the early 1990s many experts expressed concerns that future shortages could heighten tensions among the six Central Asian states. Instead, what emerged over the last 20 years was a process of building up and institutionalising regional cooperation on water management. This book will give an overview of the achievements so far, the remaining weaknesses and challenges, and of future prospects.