When it rains some of the rain water soaks into the ground and starts to travel downwards through the soil. Eventually it will find its way into areas of porous rock known as AQUIFERS. Water companies drill deep holes known as BOREHOLES down into these aquifers and use powerful pumps to draw the water up to the surface so it can eventually be used for drinking. This water is known as GROUND WATER.
Characteristics of Ground Water
Ground water is usually much cleaner than surface water. There are a number of reasons why this is the case:
1: The water is filtered by the sand and rocks as it percolates down through the ground, (it is pulled down by the force of gravity.) Hence, much of the dirt that ground water contains is filtered out as the water journeys downwards.
2: Owing to the dark and cold conditions, and a lack of oxygen in the aquifer it is much harder for many types of bacteria to grow and reproduce. Hence, ground water usually contains fewer germs, (bad bacteria), than surface water.
3: Ground water isn't as exposed as surface water, so it doesn't have the problem of waste from animals such as fish, mammals, birds etc. being released directly into it.
However, there are some problems that ground water shares with surface water.
Examples of Problems
1: If it rains after farmers have put chemicals such as fertilisers or pesticides on their crops to help them grow, the chemicals used may dissolve in the rainwater and be carried down into the ground, polluting the water in the aquifer. These pollutants are considered to be contributory factors to the development of some illnesses.
2: Even though ground water is often quite clean it may still contain some germs (bad bacteria). To ensure this water is safe to drink, water treatment is necessary.
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