By the year 2000 the world had built more than 45'000 large dams. They have transformed the management of both water and energy resources, but their impacts have generated growing controversy and conflicts. The World Commission on Dams (WCD) worked between 1998 and 2000 in a unprecedented effort to bring all the stakeholders together (governments, private sector, international financial institutions, export credit agencies and NGOs) to discuss the complex development challenges that big dams have created.