Several hundred stone-throwing protesters disrupted the opening of the World Water Forum, an international gathering in Istanbul designed to address the growing demand for fresh water, and to find ways to avert conflicts over the limited resource. Outside the meeting riot police clashed with stick-wielding protesters, eventually using tear gas and water cannons to break up the protest. The police also arrested 17 activists who tried to enter the meeting hall. The need for new environmental policies was highlighted last week when the United Nations warned that nearly half of the world's people will live in areas with acute water shortages by 2030.