Water (H2O) is the most abundant compound on Earth’s surface, covering about 70 percent of the planet. Of all the water on Earth, only 2.5 per cent is freshwater. And of all this freshwater, the total usable supply for ecosystems and humans is less than 1 per cent. According to the World Bank, Water is essential to food and energy security, industrial growth, and protection of ecosystems. The water challenges are growing and they are all interlinked: Growing populations and economies put unprecedented pressures in water. Over the next 20 years, cities will have to meet water demand of 70 million more people each year. It is estimated that feeding the world will require 30 to 45 percent more water in 2030 than today. Energy demand will more than double in poor and emerging economies in the next 25 years putting additional pressures on already constrained water resources. Yet, 783 million and 2.5 billion people remain without water and sanitation, respectively. Climate change will worsen the situation by increasing water stress. Climate change may also reintroduce water security challenges in countries that for a hundred years have enjoyed reliable water supplies and few, if any, water shocks. Much of the developing world will have to cope with droughts and/or the growing risk of flooding. Currently, 1.6 billion people live in countries and regions with absolute water scarcity and the number is expected to rise to 2.8 billion people by 2025.