Water pollution is a large set of adverse effects upon water bodies such as lakes, rivers, oceans, and groundwater caused by human activities. Although natural phenomena such as volcanoes, algae blooms, storms, and earthquakes also cause major changes in water quality and the ecological status of water, these are not deemed to be pollution. Water is only called polluted when it is not able to be used for what one wants it to be used for.

Pollutants in water include a wide spectrum of chemicals, pathogens, and physical chemistry or sensory changes. Many of the chemical substances are toxic. Pathogens can obviously produce waterborne diseases in either human or animal hosts. Alteration of water's physical chemistry include acidity, conductivity, temperature, and eutrophication. Eutrophication is the fertilization of surface water by nutrients that were previously scarce. Even many of the municipal water supplies in developed countries can present health risks. Water pollution is a major problem in the global context. It has been suggested that it is the leading worldwide cause of deaths and diseases, and that it accounts for the deaths of more than 14,000 people daily.

Together we must conserve what clean, fresh water is left on Earth. Pollutant free drinking water is an essential element of human life.

Eutrophication • Hypoxia • Marine Pollution • Ocean Acidification • Oil Spill • Ship Pollution • Surface Runoff • Thermal Pollution • Wastewater • Waterborne Diseases • Water Quality • Water Stagnation