Xinhua: The surging growth in global population, climate change, widespread mismanagement and increasing demand for energy have tightened the grip on the world’s evaporating water supplies, warned a new United Nations report released here on Wednesday. As the world’s population has swollen to well over 6 billion people, some countries have already reached the limits of their water resources, according to the report compiled by 24 UN agencies. “Climate change is going to make this …