dégradation des ressources en eau douce

Pollution immediately or eventually involves the hydrological cycle of the earth, because even pollutants emitted into the air and those present in the soil are washed out by precipitation. Water is considered polluted when it is altered in composition or condition so that it becomes less suitable for any or all of the functions and purposes for which it would be suitable in its natural state. This definition includes changes in the physical, chemical and biological properties of water, or such discharges of liquid, gaseous or solid substances into water as will or are likely to create nuisances or render such water harmful to public health, safety or welfare, or to domestic, commercial, industrial, agricultural, fish or other aquatic life. It also includes changes in temperatures, due to the discharge of hot water.