Drinking water is crucial for human survival and for agriculture. But, as the world's population grows and pressure on resources increases, water is increasingly becoming a scarce commodity. Conflicts over water have a long history and in recent decades more and more countries want to dam rivers to control the flow, provide water for agriculture and generate power. But activities upstream have a big potential impact downstream. Putting a dam in to generate electricity upstream may have very large consequences downstream in terms of water flow, agriculture and sediment built up. Although Europe, the USA, australia and other continents have experienced big floods in recent years there are also droughts and California is facing major problems. This episode looks, among other things, at the river Nile, the Tigris and Euphrates in Iraq, and the major rivers, the Brahmaputra, the Indus and the Mekong with headwaters in Tibet which are crucial for water supply in India, Pakistan and several countries in South East Asia.