Over the last many decades, the condition of rivers, lakes and springs of fresh water throughout much of the world has deteriorated.
Many years ago, water from natural sources could be used for drinking, irrigation, everyday use and fish-breeding. Today, many rivers and lakes have become polluted by sewage and industrial waste.
One of the main issues for the world at this time is finding a solution to the problem of supplying people in cities and in their homes and on farms with clean water.