If you think that an energy shortage was bad, it will pale in comparison to the next water crisis. So investment in fresh water infrastructure is going to be a great recurring long-term investment theme.

One theory about the endless wars in the Middle East since 1918 is that they have really been over water rights.

Although Earth is often referred to as the water planet, only 2.5% is fresh, and three quarters of that is locked up in ice at the North and South poles.

In places like China, with a quarter of the world?s population, up to 90% of the fresh water is already polluted, some irretrievably so.

Some 18% of the world population lacks access to potable water, and demand is expected to rise by 40% in the next 20 years.

Aquifers in the US, which took nature millennia to create, are approaching exhaustion, especially in California?s Central Valley.

While membrane osmosis technologies exist to convert seawater into fresh, they use ten times more energy than current treatment processes, a real problem if you don't have any, and will easily double the end cost of water to consumers.?

While it may take 16 pounds of grain to produce a pound of beef,?it takes a staggering 2,416 gallons of water?to do the same. Beef exports are really a way of shipping water abroad in highly concentrated form.

The UN says that $11 billion a year is needed for water infrastructure investment and $15 billion of the 2008 US stimulus package was similarly spent.

It says a lot that when I went to the University of California at Berkeley's School of Engineering to research this piece, most of the experts in the field had already been retained by major hedge funds!

At the top of the shopping list to participate here would be the Guggenheim S&P Global Water Index ETF (CGW).

You can also check out the PowerShares Water Resources Portfolio (PHO), the First Trust ISE Water Index Fund (FIW), or the individual stocks Veolia Environment (VEOEY), Tetra-Tech (TTEK) and Pentair (PNR).

Bonus Question:? Which country has the world?s greatest water resources? Siberia, which could become a major exporter of H2O to China in the decades to come.

The New Liquid Gold?