Coral Island Water Sources

Finding water on a coral island can be extremely difficult and expensive. The techniques used generally use a lot of electricity, and can take a long time and a lot of money to build and maintain the facilities. Since fresh water is scarce, coral islands have to use one or more of the following methods.

Ground Water

One of the oldest methods of getting fresh water, digging a well is still the cheapest way to do it. The materials for drilling wells is more accessible than those used for some of the later described methods, so it is easier for less affluent islands. The image to the right illustrates how water percolates to the saturation zone, where a layer of rock makes it difficult for the water to penetrate further. A well can then be dug to extract the water which builds up. The depth necessary depends upon where in the world the island is. If it is in an area with a lot of rainfall, or lots of rock which would prevent water from going deep in to the ground, the water would be close to the surface, and easier to access.

Desalinisation by Distillation

Distillation is an effective way to remove the salt in water. There are several methods used, but the most common is one called multi stage flash, in which water is drawn in to a tank with lower pressure than the one it is in, and is rapidly heated, causing it to evaporate. It is then condensed in a tank with lower pressure, and the process is repeated with left over water. The byproduct is salt, which once separated from the other minerals in the water can be safely disposed of or sold.

Desalinisation by Reverse Osmosis

Reverse osmosis is the most common method by which salt is removed from water. In reverse osmosis, water is forced through a semi-permeable membrane which prevents the salt from flowing through. The process is repeated several times through carbon and TFC (Thin Film Composite) membranes, and the end result is almost pure water.

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