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Pollution and depth of waterFeatured science projectScience project video


Does the pollution in a lake get worse as it gets deeper? Is the water cleaner nearer the surface? Or is it the other way around? This science fair project was conducted to determine how the depth of water can affect the concentration of pollution found in the water. The experiment was done by collecting water samples from a lake at depths of 1 meter, 2 meters 3 meters and 4 meters.


A water sample taken from deeper waters will contain less pollutant.

Scientific Terms

Pollution, fertilizers, insecticides, organic material, turbidity


Water pollution

Rivers, lakes and oceans become polluted when foreign substances are released into these bodies of water before treatment to remove these contaminants has taken place. Our rivers and lakes are an important source of drinking water. They are also an important source of water for animals living in these habitats. When water is polluted, the entire ecosystem is affected. Polluted water is also unfit for agricultural and industrial use.
During heavy rainfall, pollutants in the surrounding catchment area are washed into  lakes and rivers. These pollutants are a result of agricultural and industrial waste including fertilizers, insecticides, loose soil, organic material, chemicals and much more. When land is cleared for farming or development, the top layer of the soil is washed into the rivers and lakes. This causes a higher level of sedimentation in the water and affects the turbidity of the water.

In areas that are populated, water pollution arises in the form of domestic sewage, namely waste water discharged as a result ofhousehold activities such as washing clothes, showering or washing dishes. This waste water contains detergents, fat, grease and other household waste. The waste is discharged into the rivers through a network of drains and they eventually end up in the lakes or the ocean.

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Complexity level:
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Time required:
1 day to prepare, 1 day for observation
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Access to laboratory equipment
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Scuba diving safety protocols and water safety measures to be strictly observed at all times. Should be performed only by an experienced adult.