Throughout history water has confronted humanity with some of its greatest challenges. Water is a source of life and a natural resource that sustains our environments and supports livelihoods but it is also a source of risk and vulnerability. In the early 21st Century, prospects for human development are threatened by a deepening global water crisis. Debunking the myth that the crisis is the result of scarcity, this report argues poverty, power and inequality are at the heart of the problem. In a world of unprecedented wealth, almost 2 million children die each year for want of a glass of clean water and adequate sanitation. Millions of women and young girls are forced to spend hours collecting and carrying water, restricting their opportunities and their choices. And water-borne infectious diseases are holding back poverty reduction and economic growth in some of the worlds poorest countries. Beyond the household, competition for water as a productive resource is intensifying. Symptoms of that competition include the collapse of water-based ecological systems, declining river flows and large-scale groundwater depletion. Conflicts over water are intensifying within countries, with the rural poor losing out. The potential for tensions between countries is also growing, though there are large potential human development gains from increased cooperation.