Desalination for free

Yes, that’s right.  I said it.  Free. 

When we imagine ourselves being completely out of water resources, we look toward the ocean.  We lament desalination as the inevitable and least desirable way to get our future fresh water.  This is natural - just look at all of that water.  But we fail to recognize desalination is already happening for us - for free.

Contrary to conventional wisdom, the available quantity of fresh water is not finite.  It is expandable to a far greater extent than we will ever need.  During the height of the last ice age (aka last glacial maximum about 20,000 years ago), entire land masses were covered in fresh water glaciers to such an extent that sea level was 100 feet lower than today.  In order for glaciers to impound that quantity of water, they needed to be several thousand feet in thickness!  This stored quantity of fresh water was multitudes greater than we have today.  All of this happened naturally.

The greatest single source of our planet’s atmospheric moisture comes from the oceans.  This moisture then blows over the continents and forms clouds where it precipitates inland.  The ocean delivers purified, chilled, desalinated water onto our dry land.  One of the scary impacts of global warming is that ice formations are receding and the sea is consequently rising.  This is causing beach erosion, inland flooding, and in some rare cases, the complete disappearance of small habited islands.  Imagine that we make an effort to trap all of our rain and snow in millions of containers so none of the fresh water flows back to the ocean.  Each year, new precipitation will fall.  Much of it will come from the evaporation from the buckets, but still more would come from the ocean.  Each year we will need more containers.  The more fresh water we store, the more fresh water we get.  Consequently we also mitigate sea level rise.

The Great Salt Lake is 2 to 7 times more saline than the ocean, yet it too provides us with free desalination via the “lake effect”.  This large body of water allows humans to survive in the area because the evaporation from the lake creates precipitation, with the highest concentrations of fresh water within 30 miles of the shore.  Consequently, the Great Salt Lake is a source of fresh water in Salt Lake City.  If you take away the Great Salt Lake you also lose the fresh water that precipitates from it, thus making Salt Lake City uninhabitable.

Lake Havasu was created in 1938 when the Colorado River was dammed for the purpose of storing and routing water through aqueducts.  The city of Lake Havasu, AZ was established there in 1968 and it now contains over 52,000 people.  Yet the river still flows.  Did we manage to accumulate fresh water?  Yes in fact we did.  If we need more fresh water, we simply need to store more water inland.  Water reservoirs do not deplete water - they reserve it and increase it.  As we build more reservoirs, we control flooding and we keep excess fresh water from running back to the ocean.  We also encourage lake effect precipitation thus enriching the land around the reservoirs.  At the same time, the oceans continue to contribute even more fresh water to inland locations, providing natural desalination for free.   We only need to store it.

Tony F.