Many towns + factories are built near rivers so that they can use water from the river. But sometimes the water is not cleaned before it is put back into the river. Pollution can take lots of forms:
- Rubbish - crisp packets, newspapers, bags etc
- Poisonous substances
- Cans, bottles + other solid objects
- Human waste / excretement
Causes of Pollution
There are four main causes of pollution:
1. Agriculture - Farmers put fertilizers + pesticides on their crops so that their crops grow better. But these fertilizers and pesticides can be washed through the soil by rain, to end up in rivers.
2. Factories - Factories use water from rivers to power machinery or to cool down machinery. Dirty water containing chemicals is put back in the river. Water used for cooling is warmer than the river itself, and this is also a form of pollution.
3. Mines - Waste water from old tin, coal and lead mines is a problem. When the mines were in use, they had pumps to keep them dry. Now, water drips through the old mine shafts + fills tunnels. The water reaches the surface by springs after coming into contact with rusty machinery.
4. People - People are sometimes careless and throw rubbish such as bottles + crisp packets directly into rivers.
Effects of Pollution
Pollution can make rivers smell. Pollution kills water plants + animals. Fertilizers and pesticides are harmful because they cause algae to grow. The algae then destroy water plants.
Polluted water also carries diseases. When animals drink the water, they may get diseases which can kill them. People can even get these diseases by eating the infected animal. This happens a lot in poor countries in Africa where people get untreated water directly from the river. Rivers also look unsightly when there is rubbish in them.
Efforts are being made to clean dirty rivers like the Mississippi and Missouri in the USA. Water companies like Southern Water are spending a lot of money to clean up dirty rivers. There are fines for companies and people who delibaretely throw rubbish into the river. In some countreis there are action groups where local people lobby the government to do something about pollution. The Rhine Action Programme is financed by the countries which the River Rhine flows through. Officials check the levels of pollution in the river. Governments also make guidelines on the amount of chemicals allowed in the water which is put back into rivers.