Water pollution

Pollution is something which spoils or dirties a place or a thing. Water pollution occurs when a body of water is affected, in a bad way, by the addition of large amounts of a material. That material might be oil, garbage, animal wastes, fertilisers and other chemicals, sewage or litter.

Oil
Petroleum often pollutes water in the form of oil. Oil spills from ships and super-tankers, and from off-shore oil drilling operations cause pollution. Oil and petrol that leaks from cars and trucks also washes off roads and into waterways through stormwater drains.
Oil forms a thin layer on top of water and act like a lid on the surface and the water. Animals and plants living in the water can't breathe, the oil coats the feathers of water birds, and the fur of animals that swim in the water, causing them to become sick and, if there is a great amount of oil on their bodies, to die. Even the insects that live on the surface of the water are badly affected.

Nutrients in fertilisers cause excessive growth of plants and algae which takes oxygen and light from water animals

Fertilisers contain nutrients such as nitrates and phosphates that help plants to grow. That's why farmers use them. When fertilisers are washed into rivers and streams the nitrates and phosphates cause excessive growth of water plants. The plants clogs the waterways, use up oxygen in the water, and block light to deeper waters. This is harmful to the fish and other invertebrates that live in water because it make it hard for the animals to breathe.

Soil
Pollution of waterways is also caused when silt and soil washes off ploughed fields, construction and logging sites, and from river banks when it rains.

Sewage and other organic pollutants
When material such as leaves and grass clippings, and waste from farm animals enters the water, it rots and breaks down and uses up the oxygen in the water. Many types of fish and other aquatic animals cannot survive.
Organisms such as bacteria and viruses enter waterways through untreated sewage in storm-water drains, run-off from septic tanks, and from boats whose owners dump sewage into the water. These microscopic pollutants cause sickness in people and in animals that drink or live in the water.

Chemicals
Chemical pollution entering rivers and streams causes great destruction. The chemicals can come from factories, construction sites, mining operations, and from homes when people pour chemicals down the sink or down the toilet.

Plastics
Floating plastic is ugly, and harmful to the environment. Plastic rubbish is not biodegradable (it doesn't rot away after we have used it) It can choke animals that try to eat it, and drown those that get tangled in it.

Litter
When people drop litter such as plastic and cans, food wrappers and cigarette butts, they can be washed by the rain into rivers and other waterways through stormwater drains in the streets . At the beach, it is important that people take home their litter or put it into garbage bins at the beach so that it doesn't get into the sea.

If you use any of this information in your own work acknowledge this source in your bibliography like this:
Thomas, R & Sydenham, S. Water pollution [Online] www.kidcyber.com.au (2008)