Humans depend on water for drinking, cooking, swimming, fishing, and farming.
Discharges of organic wastes, heated water, nutrients, sediments, toxic chemicals, and other hazardous substances can all make water unfit for human use. Organic wastes, produced by animals and humans, decompose through the use of oxygen. If a body of water spends too much oxygen during the decomposition of organic wastes within it, certain types of fish will not survive. Aquatic life can also be harmed by the discharge of heated water into lakes and streams, because the increased temperatures accelerate biological and chemical processes that reduce the water's ability to retain oxygen. The release of nutrients and sediments, such as detergents and fertilizers, can also harm bodies of water.