Water scarcity is a worldwide issue and will affect an increasing number of people as the world population grows from the current 6 billion to 9 billion by mid-century. U.N. studies indicate that 2.7 billion people will face severe water shortages by 2025 if consumption continues at current rates. Not only sheer population growth but also urbanization will strain water resources. While historically more people have lived in the countryside than cities, that trend has been changing, and by 2020, urban dwellers will outnumber their rural counterparts. As a result of this population density, municipalities will have increasing difficulty providing sufficient amounts of water to their residents.