Question

What are the causes for water pollution??

Answer 1

Answer:

Water pollution may cause very dangerous diseases, for example cholera, giardia, and typhoid. Water pollution can be caused in a number of ways, one of the most polluting being city sewage and industrial waste discharge. Indirect sources of water pollution include contaminants that enter the water supply from soils or groundwater systems and from the atmosphere via rain.

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Answer 2

Urbanisation

Urbanisation causing water pollutionAs more and more people move into cities and towns, a number of factors cause pollution:

the physical disturbance of land due to construction of houses, industries, roads, etc.;

chemical pollution from industries, mines, etc.;

inadequate sewage collection and treatment;

increase in fertilisers to grow more food. This results in an increase in nutrients (nitrates and phosphates) in the water which causes enhanced plant growth (algal blooms). When this plant material dies and decays the bacteria uses the oxygen in the water. This lowering of oxygen levels results in the death of other water life that needs oxygen to survive, eg. fish, etc. This process is called eutrophication;

litter, which causes disease and has a negative visual impact.

Deforestation

Clearing land for agriculture and urban growth often leads to water pollution. When soil is stripped of its protective vegetation it becomes prone to soil erosion. This leads to an increase in the murkiness of the water which can cause the following:

it can block the gills of fish;

bottom dwelling plants cannot photosynthesize as the sun’s rays cannot reach them; and

there is an increase in disease as bacteria and viruses use the soil particles as a method of transportation.

Damming of Rivers

Damming of rivers can have an impact on water in the following ways:

Water flowing out of dams:

has reduced suspended material as a large amount settles to the bottom of dams;

is depleted of nutrients; and

is often more saline

with detrimental effects on downstream agriculture and fisheries.

Enhanced eutrophication may result due to the water spending a longer time in the dam.

There is also increased evaporation in dams, especially those with a large surface area, such as the Vaal Dam.

Destruction of Wetlands

Wetlands in South AfricaWetlands are nature’s way of cleaning water as well as damming water (they hold back water in summer and release it in winter).

Destruction of wetlands:

Destroys the habitat of many birds and fish;

Removes the natural filters capable of storing and degrading many pollutants, such as phosphorus and heavy metals;

Destroys natural dams and causes flooding further downstream.

Industries

Industry causing pollutionIndustries produce waste that can affect the:

pH of water (whether it is acid, neutral or alkaline);

colour of water;

amount of nutrients (increase in nutrients can cause eutrophication);

temperature (increase or decrease in temperature can have an impact on temperature sensitive organisms living in the water);

amount minerals and salts (too much can cause health problems);

murkiness of water (can block fish gills; bottom dwelling plants cannot photosynthesize as the sun’s rays cannot reach them; increase in disease as bacteria and viruses use the soil particles as a method of transportation).

Mining

Mining causing pollutionMines produce waste that:

can increase the amount of minerals and salts in the water (too much can cause health problems);

can affect the pH of the water (whether it is acid, neutral or alkaline);

can increase the murkiness of the water.

Agriculture

AgricultureIncreases soil erosion due to the physical disturbance of soil and vegetation due to ploughing, overgrazing, logging and road building. This effects the murkiness and the amount of salts and minerals in water;

Increases nutrients due to fertilisers and excreta, which contribute worrying amounts of nitrates and phosphates to water supplies (this can cause eutrophication);

Increased pesticide use.