"Thousands have lived without love, not one without water.”
— W. H. Auden
Did you know…
If all the salt dissolved in Earth’s oceans were removed and spread evenly across the Earth's land surface, it would create a layer about 500 feet deep.
That is roughly the height of a 40-story building made entirely of salt. And yes, that estimate includes all of Earth’s oceans combined.
Being the curious soul that I am, that fact immediately led to a whole litany of other questions.
Since the oceans contain about 97% of all the water on Earth, why don’t we simply turn ocean water into drinking water?
The answer is that we can (and do). The process is called desalination, which removes salt from seawater. The challenge is that desalination requires significant energy and infrastructure, making it an expensive option typically used only where freshwater is scarce.
Globally, desalination plants produce about 26 billion gallons of freshwater each day, with 60–65% coming directly from seawater. Even so, desalinated ocean water still supplies well under 1% of the world’s freshwater use.
So, where is desalination most important?
The Middle East produces roughly half of the world’s desalinated water, largely because many countries there have very little rainfall and few natural rivers.
Some examples include:
Saudi Arabia, the world’s largest producer of desalinated water
Qatar, where about 90–99% of drinking water is desalinated
Israel, where about 70–80% of household water comes from desalination
Bahrain, where about 60–65% of drinking water is desalinated
Countries around the Mediterranean, including Spain, as well as parts of Italy and Greece, also use desalination during drought periods. Australia built large desalination plants during major droughts to supply cities such as Perth and Melbourne.
The United States, however, uses relatively little seawater desalination. One example is the Carlsbad Desalination Plant in California, which supplies about 10% of San Diego County’s drinking water. Nationally, well under 1% of U.S. drinking water comes from desalinated seawater. Perhaps our friend Jeff Dowler, CRS will check in on that topic.
So while the oceans hold almost all of the planet’s water and enough salt to bury the continents hundreds of feet deep, humanity still depends mostly on the small fraction of Earth’s water that is naturally fresh.
Interestingly, not all desalination involves ocean water. In many places, the water that needs treatment is naturally saline groundwater, often called brackish water. This water comes from underground aquifers that contain higher levels of dissolved minerals and salts than typical freshwater. It is not nearly as salty as seawater, but it is still too salty to drink or use for irrigation without treatment.
A good example is Yuma, where I spend winters. Much of the water in that area comes from the Colorado River and local groundwater sources that pick up salts from surrounding desert soils and rock formations. To make the water suitable for use, it must be treated to remove some of that natural salinity. We can buy desalinated water for .25 per gallon or 5 gallons for $1.
Nearby is the Yuma Desalting Plant, one of the largest desalination facilities in the world, built to treat salty agricultural drainage water from the Colorado River irrigation system.
In other words, desalination is not just about turning seawater into drinking water. In many parts of the world, it is also used to treat naturally saline groundwater and river water, making it usable for homes, farms, and communities.
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