Raw sewage and industrial waste in the New River as it passes from Mexicali to Calexico, California

By-products of copper color this stream blue.

Water pollution is the pollution of bodies of water, such as lakes, rivers, seas, the oceans, as well as groundwater. It occurs when pollutants reach these bodies of water, without treatment. Waste from homes, factories and other buildings get into the water bodies and as a result water gets polluted.