Why do rivers get polluted

But when measured for nitrates, fewer than one in ten European rivers is any longer natural: most have nitrate levels four times the norms found in nature. As cities expand to support larger populations, roofs, highways and parking lots increasingly replace permeable soils and vegetation. Rain water in urban areas is channeled into sewers and drain systems instead of filtering into the ground to raise the water table.

In developing countries the picture is very different. Rivers in the poorest countries have shown a substantial drop in the level of dissolved oxygen. Nine-tenths of all sewage in developing countries runs directly into rivers, lakes and seas without treatment. Many types of pollution are discharged into rivers, and the purification processes remove them at various speeds.

Some heavy metals , for example, are removed relatively quickly because suspended clay and organic particles have a slight electric charge and adsorb the metal atoms. When the clay or organic particles settle out of the water, they take the metal atoms with them. Unfortunately some pollutants are very persistent in the water and can accumulate downstream, causing great hazard. Suspended solids in a moving body of water will settle out at a various points or be carried longer distances, depending on their size and the rate of the flow.

The higher the amount of suspended solids is, the cloudier or more turbid is the water. Suspended matter can affect the amount of light entering water and therefore restrict the amount of photosynthesis that can occur and therefore the growth of plants.

Small particles settling out in large amount on the bottom of a water body can prevent some organisms from living there as well as preventing green plants from photosynthesising. How fast the water body moves affects the degree of mixing of water and how much dioxygen it will carry. Thus, fast-flowing highly agitated streams will not only be saturated with oxygen but also carry well-mixed nutrients, which will be ultimately carried to a river.

The temperature of a water body is crucial to the amount of dissolved dioxygen it can contain. The warmer the water, the less dioxygen it contains. Toggle navigation. River water quality and pollution A river is defined as a large natural stream of water emptying into an ocean, lake, or other body of water and usually fed along its course by converging tributaries.

Skip to main content. K-5 GeoSource. PDF version. Learn More. Why is water an important resource? How is water distributed? Where does our water come from? Some of the dirt polluting streams comes from the stream banks. The solution is to stop the dirt from getting into the stream in the first place by disturbing the land as little as possible. Farmers and construction workers are using new methods to reduce the amount of earth they disturb.

Bacteria are also a big water quality problem. Not all bacteria are harmful, but germs and viruses that can make you sick might be in the water.

Bacteria can come from combined sewers after rainstorms and runoff of animal waste from farms, pets, and wildlife. Sewage systems can be improved to keep untreated sewage from overflowing. Farmers are developing better ways to manage livestock manure. Dog owners are picking up after their pets. Nutrients are element needed for animal or plants to grow.

The two most common nutrients found in water are nitrogen and phosphorus. They cause algae to grow and can turn the water green.