We hear a lot about how drinking water is drying up around the world. But the fact is that we have a "theoretically limitless" supply of drinking water, according to hydraulics engineers. The real problem is economic.


Over on Quora, subsea hydraulics engineer Ryan Carlyle answers whether scientists have determined how much water is left for us to drink on the planet:

Global water supplies are theoretically limitless, because it's not destroyed when we use it — it just gets dirty. Water can be reused... if you live on a river, some of your drinking water probably comes from an upstream town's sewage treatment plant! Waste water recycling and salt water desalination can produce any imaginable quantity of potable water. Moisture can be slowly pulled from the air even in the driest deserts. A sufficiently deep well drilled almost anywhere on the planet will eventually hit a large salt-water aquifer.



The real problem is that fresh water requires energy and money to produce. Nations and citizens don't want to spend vast quantities of resources on producing fresh water. Access to clean water is seen by most as a basic human right, meaning it must be cheap for consumers, meaning it must be cheap to produce.



Cheap water has to be accessible, low-salt, and relatively clean to start with. That's a very rare sort of water — basically just rivers, lakes, shallow aquifers, and a bit of precipitation and ice. Such fresh water is being diverted in enormous quantities for agriculture. When you consider the rapid depletion of major aquifers and various lakes for irrigation projects around the world, we're probably already using more fresh water than can be sustained. There is extra fresh water in inconvenient places like glaciers and rainforests but it isn't cheap enough to transport to population centers.



So water is limited by the amount of wealth and economic activity we're willing to invest. But if money is no object, global water supplies are limitless.


We could easily be assuring the entire world an endless supply of potable water, if only the money were available.

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