This report traces the trends in both conflict and cooperation over water resources from the beginnings of human civilization to the modern day challenges of big dams, climate change and mega-cities. Drawing on the many research papers, case studies, identified tools and mechanisms and field work of the joint PC-CP and Water for Peace process programme, this report provides an account and analysis of the myriad intricate and interdependent links between water, security and peace. This report clearly shows that there has always been competition, and sometimes conflict, over water; but what matters most in preventing conflicts is a community's capacity to cope with and adapt to water stress and the institutions available to them to deal with competition between users. Both our capacities and institutions have evolved over the centuries, but while the need to develop the technical means to address shortages through the diversion or storage of water has always received attention and resources, less focus has been placed on human capacity-building and the development of effective institutions to manage water wisely and equitably. This neglect of the institutional side is largely responsible for spawning the water management crisis experienced across the world today.