The document discusses water pollution and its causes and effects. It begins by describing a clear, clean river that turns brown and muddy as it passes through a city, picking up pollutants. It then discusses how water from different sources like taps, puddles, and rivers can have different colors, tastes, and smells depending on what they flow through. Major rivers like the Yamuna and Ganga in India become polluted as they pass through populated areas and pick up garbage, chemicals, and other waste. This pollution affects humans, animals, and plants and can spread disease. The document emphasizes the importance of keeping water bodies clean and provides some ways to do so, as well as methods for purifying water.