There is a likely shortage of clean water for many nations on the horizon. Let's take a look at two world powers, China and Russia. Here is the amount of Internal Renewable Water Resources (IRWR) that China has per capita: just 2,173 cubic meters IRWR per person. Russia, on the other hand, with 1/5th the population (and declining), has 30,001 cubic meters IRWR per person, nearly 15 times that of China.

Nations may squabble over land, oil, gold or some other commodity, but when it comes to water, there's no squabbling, no protracted negotiation water is critical to survival.

All that fresh clean water which Russia has in Siberia has to look pretty good to China, a nation that, relative to its population, didn't have much to begin with and has squandered much of water resources it does have via pollution.

If China is in bad shape for potable water now, hence their land grab of Tibet from which most of their still-clean water now comes from. Let's imagine India's possible crisis, with just 1,211 cubic meters IRWR per person, barely enough to sustain new life after taking into account agriculture, industrial uses, and survival consumption.

Let's contrast China and India with, the USA and Canada. The U.S. has nearly 10,000 cubic meters IRWR per person, and Canada weighs in with an amazing 91,000. Water is needed for oil extraction, to squeeze gas from shale, to cool solar water towers, to keep agricultural products growing, and for scores of other projects.

In nations like the USA and Canada water is readily and cheaply available; we take it so much for granted that we barely notice it. Worldwide, this is big business. And over time the business of producing clean water in China and India will grow exponentially.

Here are a few possibilities for investors to gain diversification by investing in ETFs and mutual funds with exposure to water. Two ETFs are in this business, PowerShares Global Water (PIO) and PowerShares Water Resources (PHO). PIO is up about 50% this year and PHO about 20%. Another ETF is First Trust ISE Water (FIW). .

Current water usage and future water demand doesn't depend upon the actions of governments or pricing of the resource. The case for investing in water is simple, if populations increase, water usage will also increase. If more water is contaminated, more water has to be cleaned to be a usable resource. If there are more mouths to feed, more food must be grown, more manufacturing which requires water. It all adds up to increased demands for water.

Note: I do not own PIO, PHO or FIW