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Wednesday, January 14, 2009

Shipping Water Across Long Distances

(My Original Blog Post:
Jessica from Australia asks:

I remember... it would have been about 2001. Queensland was suffering with massive floods while the rest of the country was parched. I remember asking my Grade 5 teacher why they didn't just ship all that water further down the continent. He seemed to think it wasn't feasible.  Is that true?

Thanks for the question, Jessica.

Because of geology, terrain, the hydrological cycle, and many other factors, it is true that there are some geographic locals that have more water than others.  Typically, human civilization has sprung up around vast sources of fresh water.  Farming, drinking, shipping - these are but some of the uses of a local and large fresh water supply, and most cities that are near one tend to be better off than those who's water supplies are short.

Water supplies are in high demand, and there's no doubt as our supplies dwindle wars will be fought over them, as they are now over fossil fuels.

It may not seem like it, but water is a very heavy substance.  It may surprise you to learn that on average, a full ten percent of all electricity used by any particular city is consumed just to move potable water around water mains.  That is a lot of electricity.

The average person in a first world nation, considering the high and low, uses about four hundred liters of water a day.  This includes bathing, cooking, drinking, cleaning, laundry, gardening and other miscellaneous activities.

Then a typical family of four would use 1,600 liters a day, and 11,200 liters a week.  The typical water truck carries 6,000 liters, so for just one family it would cost two water trucks to make a round trip to wherever it is that has the water.

Consider then a city of 100,000 people.  In one week, a city of that size would require a visit by the equivalent of 46,666 water trucks just to keep the reservoirs full of water.

Considering the needs of the rest of the cities that may be low on water, and you can see that the task of hauling or piping water from long distances is just not feasible. There aren't enough trucks, diesel fuel, pipeline, or electricity to meet the demand of today's water consumer.

This would, however be feasible for a short duration of emergency, say after war or natural disaster, when water would be used only for drinking and medical purposes.

The above model also does not take into consideration industrial water use, water wastage during the treatment process, and the inefficiencies of infrastructure (small losses from water mains are typical).

As you can see, your teacher is correct. It is indeed not feasible to transport water over large distances at the current rate of consumption and at the current population.

Better alternatives would be desalination if you live near an ocean. However, because of the current technologies available to remove salt from water, producing a liter of drinkable ocean water costs thousands of times more than a liter of fresh water.

A more realistic approach would be to drastically change the way we as a society uses and wastes water in general.  This combined with proper recycling techniques, rain water collection and more efficient treatment practices would solve many problems.

I hope I've answered your question. If you would like further clarification, don't hesitate to ask.

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