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Private Island Water Supply

In the city, we often take water for granted. We turn on the taps and out it pours. We fill jacuzzis and washing machines full of the stuff, never stopping to think where it comes from.

We don’t struggle much for our most important resource in the developed world, but on a private island, water is a much scarcer commodity. After a few years of private island living, you won’t take water for granted ever again. If your 30,000 gallon cistern is full, you’ll feel rich, no matter what your bank balance says. In the search for a private island, water should be one of your first concerns. We can live without satellite TV and most other amenities, but water is necessary. If you’re close enough to a water source on the mainland or a larger island, you can run pipe across to your island. If not, there are a few ways to access the water that lives above, below and all around us on a private island.

Catching Water from the Sky

A cistern catches and stores rainwater, ranging in size from a few gallons to thousands of gallons. In the tropics, a cistern can supply enough water for household needs, if you calculate everything correctly. The first thing you need to calculate is the average rainfall in your area, spanning five years, including droughts. Next, calculate the size of your cistern, the roof area used to collect rain, and the number of people who will be using the water supply. As life goes on, rain will occupy a large part of your thoughts. If a cistern is your only water source, you will always wonder if it’s full enough. Cisterns can be built above or below ground, sometimes incorporated into the foundation of a dwelling or set on top of a house. If the water supply is meant for human consumption, cisterns can be outfitted with filters or other water purification methods. Desalination Systems

Desalination Systems

Remember that old expression, “water, water, everywhere, but not a drop to drink”? This can often be the case for salt water islands without a fresh water supply. The days of the Ancient Mariner are past; modern technology offers a convenient rescue plan for island dwellers. Desalination systems can be purchased from $20-50,000. Reverse osmosis is the most common method of desalination; sea water passes through a semi permeable membrane through which water molecules can flow, but salt cannot. A membrane in good condition will remove 99% of the saline. The pores also restrict some disease causing bacteria and other nasty molecules, but an additional carbon filter might be considered where chemicals like pesticides are a concern. We have our own internal semipermeable membrane: the lining of our intestines. Osmosis, the opposite of reverse osmosis, is why drinking salty ocean water will kill you. With salty water in your stomach, osmosis draws water from your body in an effort to dilute the salt in your stomach. This is why we eventually dehydrate and die. A desalination unit will ensure that you don’t.

Digging yourself a well

Getting busy with a pick and shovel and a few strong friends is one way to dig yourself a well. If your island doesn’t already have a functioning well, it might be the only way to go. If the ground is soft and the water table is shallow, a dug well might just work. If the ground is rocky, you will need some serious digging equipment. But in order to dig a well at all, you need access to the ground water table. If you’ve ever dug a hole in the ground right next to an ocean or a lake, water eventually bubbles up. That is groundwater. (Half of everyone in the United States drinks groundwater everyday).

Groundwater comes from rain (or snow) that soaks into the ground. The water moves down into the ground, passing between particles of soil, sand, gravel, or rock until it reaches a depth where the ground is filled, or saturated, with water. The area that is filled with water is called the saturated zone and the top of this zone is called the water table. The water table may be very near the ground’s surface or it may be hundreds of feet below. Water in lakes, rivers, or oceans is called surface water, for obvious reasons! The earth is like a sponge, holding all that water. An area that holds a lot of water, which can be pumped up with a well, is called an aquifer. In theory, a well pumps groundwater from the aquifer to you. Dig it?